Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.
For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.
But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.
It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.
There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)
Mathematically you're correct.
But engineers like to cheat ;D
1 type of tile in 2 forms, whole and cut in half.
PS: I'd like to emphasize that only 200deg of SS needs to be tiled.
No straight path for hot gas to accelerate through the gaps
I agree that is a problem, every solution has its trade offs.Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.
For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.
But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.
It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.
There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)
Mathematically you're correct.
But engineers like to cheat ;D
1 type of tile in 2 forms, whole and cut in half.
PS: I'd like to emphasize that only 200deg of SS needs to be tiled.
Long straight lines like that are problematic.
In the words of Elon when asked why hexagons:QuoteNo straight path for hot gas to accelerate through the gaps
https://twitter.com/elonmusk/status/1107379727302451200
I think there will be near ideal hexagonal throughout, however they will get smaller in width and height as the cone hoop diameter gets smaller (as you go up the cone).Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.
For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.
But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.
It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.
There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)
Mathematically you're correct.
But engineers like to cheat ;D
1 type of tile in 2 forms, whole and cut in half.
PS: I'd like to emphasize that only 200deg of SS needs to be tiled.
Long straight lines like that are problematic.
In the words of Elon when asked why hexagons:QuoteNo straight path for hot gas to accelerate through the gaps
https://twitter.com/elonmusk/status/1107379727302451200
Seems there has been some discussion concerning the nature and geometry of the tiles to be used on Starship.[bolding mine]
https://forum.nasaspaceflight.com/index.php?topic=50620.msg2073268#msg2073268 (https://forum.nasaspaceflight.com/index.php?topic=50620.msg2073268#msg2073268)
Moving this to a separate thread as requested
Here's my take on what the tile layout might be. I know that everyone is trying to minimise the number of tiles, but I think there is a trade off and if they need to have a few dozen tile types to make a reliable and uniform surface then so be it. In my design the tiles get narrower as you move towards the apex. At some point depending on the degree of curvature relative to the size of the tiles it might also be necessary to decrease their height as well.
If there are 100 rows, each with indentical tiles, and each tile has the same fastening arrangement, then every tile on the SS can be cut from the same identical raw tile (using a water jet cutter).Seems there has been some discussion concerning the nature and geometry of the tiles to be used on Starship.[bolding mine]
https://forum.nasaspaceflight.com/index.php?topic=50620.msg2073268#msg2073268 (https://forum.nasaspaceflight.com/index.php?topic=50620.msg2073268#msg2073268)
Moving this to a separate thread as requested
Here's my take on what the tile layout might be. I know that everyone is trying to minimise the number of tiles, but I think there is a trade off and if they need to have a few dozen tile types to make a reliable and uniform surface then so be it. In my design the tiles get narrower as you move towards the apex. At some point depending on the degree of curvature relative to the size of the tiles it might also be necessary to decrease their height as well.
As long as there are multiples of each shape, whole rows for example, I wholeheartedly agree with this. We have to remember that there will be hundreds of these ships, so having different shapes, as long as they aren’t “one offs” shouldn’t be a problem. This applies to initial construction and repairs (both on Earth or Mars). Biggest issue with the shuttle was that almost every single tile was slightly different.
I have a questions based on excellent BCG's photos https://forum.nasaspaceflight.com/index.php?topic=48895.msg2072270#msg2072270The Shuttle had thin high temperature pads which would be inserted in the gaps between tiles to prevent heat getting under the tile.
There are indications that some tiles on SS SN4 are made by coating bent sheet metal. There are even some areas where there is small surface damage to the coating. Is there any other explanation?
Will the tiles be flat and approximate the 9 meter curved shape of SS?flat is probably significantly cheaper, and good enough to do the job.
Or will the tiles themselves have That 9M curve made into them?
The forward end of the nose will need to be curved, probably in 2 dimensions the closer to the nose.
Once flying the heat shield could easily be a multi year improvement project.
Edit: There will be plenty of specialty pieces around and on the control surfaces as well.
I have a questions based on excellent BCG's photos https://forum.nasaspaceflight.com/index.php?topic=48895.msg2072270#msg2072270
There are indications that some tiles on SS SN4 are made by coating bent sheet metal. There are even some areas where there is small surface damage to the coating. Is there any other explanation?
Will the tiles be flat and approximate the 9 meter curved shape of SS?flat is probably significantly cheaper, and good enough to do the job.
...
I have a questions based on excellent BCG's photos https://forum.nasaspaceflight.com/index.php?topic=48895.msg2072270#msg2072270
There are indications that some tiles on SS SN4 are made by coating bent sheet metal. There are even some areas where there is small surface damage to the coating. Is there any other explanation?
I have a questions based on excellent BCG's photos https://forum.nasaspaceflight.com/index.php?topic=48895.msg2072270#msg2072270
There are indications that some tiles on SS SN4 are made by coating bent sheet metal. There are even some areas where there is small surface damage to the coating. Is there any other explanation?
I have a questions based on excellent BCG's photos https://forum.nasaspaceflight.com/index.php?topic=48895.msg2072270#msg2072270
There are indications that some tiles on SS SN4 are made by coating bent sheet metal. There are even some areas where there is small surface damage to the coating. Is there any other explanation?
- The tiles look similar to how the Shuttle tiles were made. Molded white rigid insulation (AETB or similar) with a hard outer coating for protection and control of emissivity. I don't know how you would mechanically attach such a tile since the rigid insulation have very little strength. Perhaps structural inserts molded into the insulation.
- Rigid insulation is easily milled to any shape, then the coating is applied.
John
I have a questions based on excellent BCG's photos https://forum.nasaspaceflight.com/index.php?topic=48895.msg2072270#msg2072270
There are indications that some tiles on SS SN4 are made by coating bent sheet metal. There are even some areas where there is small surface damage to the coating. Is there any other explanation?
I have a questions based on excellent BCG's photos https://forum.nasaspaceflight.com/index.php?topic=48895.msg2072270#msg2072270
There are indications that some tiles on SS SN4 are made by coating bent sheet metal. There are even some areas where there is small surface damage to the coating. Is there any other explanation?
- The tiles look similar to how the Shuttle tiles were made. Molded white rigid insulation (AETB or similar) with a hard outer coating for protection and control of emissivity. I don't know how you would mechanically attach such a tile since the rigid insulation have very little strength. Perhaps structural inserts molded into the insulation.
- Rigid insulation is easily milled to any shape, then the coating is applied.
John
so maybe many different types of tiles will be viable and for repairing (on mars for example) they'll just have blanks and cut it with a small cnc milling machine (it shouldn't be heavy at all)
Yes, the tiles are ~-05% fiber and binder and 95% void.
Yes, the tiles are ~-05% fiber and binder and 95% void.
For attachment points, maybe when they are casting/molding the tiles, they insert a fiber matrix that terminates in one or more attachment points?
Or they could glue an attachment plate onto the bottom of each tile, but that could add a lot of weight.
Yes, the tiles are ~-05% fiber and binder and 95% void.
For attachment points, maybe when they are casting/molding the tiles, they insert a fiber matrix that terminates in one or more attachment points?
Or they could glue an attachment plate onto the bottom of each tile, but that could add a lot of weight.
In my design the tiles get narrower as you move towards the apex. At some point depending on the degree of curvature relative to the size of the tiles it might also be necessary to decrease their height as well.
In my design the tiles get narrower as you move towards the apex. At some point depending on the degree of curvature relative to the size of the tiles it might also be necessary to decrease their height as well.
It looks to me like the radius in the in that direction is constant, so you would not need to decrease the height. Getting narrower is enough.
They were called "gap fillers" and were put in to stop rentry plasma hitting the aluminum skin.I have a questions based on excellent BCG's photos https://forum.nasaspaceflight.com/index.php?topic=48895.msg2072270#msg2072270The Shuttle had thin high temperature pads which would be inserted in the gaps between tiles to prevent heat getting under the tile.
There are indications that some tiles on SS SN4 are made by coating bent sheet metal. There are even some areas where there is small surface damage to the coating. Is there any other explanation?
Elon is trying to avoid having to do this by using hexagonal tiles, however he may have to resign himself to there being a need for something to be positioned between the tiles.
SS SN04 tiles have 2 types of snap mounting:They were called "gap fillers" and were put in to stop rentry plasma hitting the aluminum skin.I have a questions based on excellent BCG's photos https://forum.nasaspaceflight.com/index.php?topic=48895.msg2072270#msg2072270The Shuttle had thin high temperature pads which would be inserted in the gaps between tiles to prevent heat getting under the tile.
There are indications that some tiles on SS SN4 are made by coating bent sheet metal. There are even some areas where there is small surface damage to the coating. Is there any other explanation?
Elon is trying to avoid having to do this by using hexagonal tiles, however he may have to resign himself to there being a need for something to be positioned between the tiles.
Then the tiles were glued to thin nylon fabric layers (AIU like the stuff womens tights are made out of) to handle the contraction and expansion.
But steels TCE is substantially less than aluminiums so such a support pad should be redundant.
Also is it my impression that each tile is on a single point mounting? In principle each tile could tip and tile (slightly) in the airstream. This might be enough to avoid flow separation and any need to curve every tile to match the underlying surface.
But this is the easy part.
Wrapping that TPS around the wings/drag surfaces/whatever is likely to prove much trickier.
Think that difference is worth noting: How much time-cost-effort-$ does it require to initially fabricate-install , versus how much time-cost-effort-$ does it require to maintain-replace? Obviously robustness of solution affects cost of both. Guess is that SpaceX would prefer a more robust solution that decreases maintenance.Indeed.
All of the verticals are the same size as the standard hex tile and the other lines are shorter.Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.
For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.
But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.
It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.
There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)
Mathematically you're correct.
But engineers like to cheat ;D
1 type of tile in 2 forms, whole and cut in half.
PS: I'd like to emphasize that only 200deg of SS needs to be tiled.
Long straight lines like that are problematic.
In the words of Elon when asked why hexagons:QuoteNo straight path for hot gas to accelerate through the gaps
https://twitter.com/elonmusk/status/1107379727302451200
SS SN04 tiles have 2 types of snap mounting:Thanks for that detail.
1. On all 6 sides
2. On 3 studs
...
Also is it my impression that each tile is on a single point mounting? In principle each tile could tip and tile (slightly) in the airstream. This might be enough to avoid flow separation and any need to curve every tile to match the underlying surface.
...
SS SN04 tiles have 2 types of snap mounting:Please provide a definitive reference? We have conjecture as to attachment for both. Caution that what we have seen is not necessarily indicative of final configuration. Thanks.
1. On all 6 sides
2. On 3 studs
Only true reference except EMSS SN04 tiles have 2 types of snap mounting:Please provide a definitive reference? We have conjecture as to attachment for both. Caution that what we have seen is not necessarily indicative of final configuration. Thanks.
1. On all 6 sides
2. On 3 studs
If there are 100 rows, each with indentical tiles, and each tile has the same fastening arrangement, then every tile on the SS can be cut from the same identical raw tile (using a water jet cutter).
It would be to much weight to take 100-200 spare tiles to mars. Instead they will just take half a dozen or so of these raw tiles as spares and use simple hand tools to cut them to any of the 100 or so different shapes (corresponding to 100 different rows).
They would have to get some practice in custom making tiles before they left for Mars.
The problem is that each tile needs to align with those in front and behind it. On a curved surface this means the angles on the hexagons have to change (see my diagram at the top of page 1) unless the intention is for tile overlap, in which case regular hexagons might be tried, but I think it would be very messy. The areas of overlap would change and the zig-zag peaks and troughs between layers of tiles would run out of phase and wouldn't line up.In my design the tiles get narrower as you move towards the apex. At some point depending on the degree of curvature relative to the size of the tiles it might also be necessary to decrease their height as well.
It looks to me like the radius in the in that direction is constant, so you would not need to decrease the height. Getting narrower is enough.
Are you considering that the heat shield only needs to be on one side? That is, they only go ~halfway around. That means that the ends of a row of tiles need not align with the previous row. Does that mean that the same sized tiles could be used for adjacent tile rows? Maybe not, but it is an additional degree of freedom to consider.
The problem is that each tile needs to align with those in front and behind it. On a curved surface this means the angles on the hexagons have to change (see my diagram at the top of page 1) unless the intention is for tile overlap, in which case regular hexagons might be tried, but I think it would be very messy. The areas of overlap would change and the zig-zag peaks and troughs between layers of tiles would run out of phase and wouldn't line up.Practically there are 2 issues here.
Can they make a special tile type that totally covers the leading edge on one side and keys in with the hexagon tiles on the other? If the curvature of the wings was constant it would only require one such tile... that said I'm thinking the curvature won't be the same will it? in which case it means unique tiles all along leading edge or at least on the variable curvature bits...The problem is that each tile needs to align with those in front and behind it. On a curved surface this means the angles on the hexagons have to change (see my diagram at the top of page 1) unless the intention is for tile overlap, in which case regular hexagons might be tried, but I think it would be very messy. The areas of overlap would change and the zig-zag peaks and troughs between layers of tiles would run out of phase and wouldn't line up.Practically there are 2 issues here.
1) Finding the minimum number of tile type and sizes that map the surface. Kind of like how you render a CAD image with the minimum number (and type) of polygons.
2) How the edges of those polygons line up.
1) is relatively simple (for simple shapes)
2) Gets much more complex. The real question is how good does the polygonal approximation to the underlying surface need to be?
Because an exact match would imply thick tiles that can be machined to a curve (which is how they did it with the shuttle, and part of the very high cost of maintenance).
My instinct (and the work of DLR sounding rocket test) is that is not necessary provided the discontinuities are a fairly small part of the boundary layer thickness
If so you can get away with flat files of the same shape, but multiple sizes, all machined from a standard size billet.
That problem gets a lt trickier on the fin leading edges, with high curvature, needing a lot of small (but IMHO still standard shaped) tiles to handle the leading edge. The area between the body and the control surfaces being exceptionally tricky.
All of the verticals are the same size as the standard hex tile and the other lines are shorter.Having a large number of intricate tile shapes might not be a problem by itself as long as they don't require a manual repairs. Unlike on the Shuttle there is no chance of getting hit by debris during launch.
For tiling a rounded cone they could do it using the same slightly warped hexagon at each height point.
But they might eventually go for unique shapes of varying thickness anyway in order to optimize mass.
It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.
There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)
Mathematically you're correct.
But engineers like to cheat ;D
1 type of tile in 2 forms, whole and cut in half.
PS: I'd like to emphasize that only 200deg of SS needs to be tiled.
Long straight lines like that are problematic.
In the words of Elon when asked why hexagons:QuoteNo straight path for hot gas to accelerate through the gaps
https://twitter.com/elonmusk/status/1107379727302451200
Then the tiles were glued to thin nylon fabric layers (AIU like the stuff womens tights are made out of) to handle the contraction and expansion.
BTW
A few years ago DLR ran a sounding rocket test with the Brazilian space agency.
They built a nose cone out of standard sized RCC tiles, mostly triangles, pentagons etc.
The key development was the software to confirm despite the segments being flat that the aerodynamics were OK and the flow was smooth enough to avoid turbulent flow (which multiplies heat transfer between 4x and about 6x).
For „field repairs“ on mars they could easily use dissimilar materials (for example ablative materials). AFAIK Elon also said mars ships might have a heatshield that‘s different from what your average daily-use starship will have. Most Starships flying to mars might only use their heatshield once.That opens up the field considerably
Any data about the weight of the heatshield materials per square meter on SS. thanks.
Hi, i'm new in this forum
i have notice this article from "the nextbig future" :
'Magnet Enhanced Aerocapture Would Enable 39 Day Mars Crewed Flights' (my enhanced)
I think it will be useful for Starship, someone could explain how it works
Any data about the weight of the heatshield materials per square meter on SS. thanks.
there is a thread for that. Rafael did a great job.
https://forum.nasaspaceflight.com/index.php?topic=50049.0
Is there a thread somewhere that gives the raptor specs. I know there is a post somewhere in the raptor thread that has it but it is very hard to find? I think livingjw did a very good post in there?
Any data about the weight of the heatshield materials per square meter on SS. thanks.
there is a thread for that. Rafael did a great job.
https://forum.nasaspaceflight.com/index.php?topic=50049.0
Is there a thread somewhere that gives the raptor specs. I know there is a post somewhere in the raptor thread that has it but it is very hard to find? I think livingjw did a very good post in there?
Any data about the weight of the heatshield materials per square meter on SS. thanks.
there is a thread for that. Rafael did a great job.
https://forum.nasaspaceflight.com/index.php?topic=50049.0
Is there a thread somewhere that gives the raptor specs. I know there is a post somewhere in the raptor thread that has it but it is very hard to find? I think livingjw did a very good post in there?
Here is the best I can come up to answer my own question:
https://forum.nasaspaceflight.com/index.php?topic=47506.600
The actual thickness of the tiles is ~9mm and they are placed on the sides/spikes with a height of ~37 mm:
(https://i.imgur.com/572IhiN.jpg)
Having just done some TPS mass estimation work, my latest estimations are leaning to an average areal density of ~13 kg/m^2
John
Having just done some TPS mass estimation work, my latest estimations are leaning to an average areal density of ~13 kg/m^2Does this include the studs or sheet metal surround mounting system?
John
Not necessarily.Any data about the weight of the heatshield materials per square meter on SS. thanks.
there is a thread for that. Rafael did a great job.
https://forum.nasaspaceflight.com/index.php?topic=50049.0
Is there a thread somewhere that gives the raptor specs. I know there is a post somewhere in the raptor thread that has it but it is very hard to find? I think livingjw did a very good post in there?
10 tons of heatshielding tiles for SS, a lot of work ahead for weight saving.
Having just done some TPS mass estimation work, my latest estimations are leaning to an average areal density of ~13 kg/m^2Does this include the studs or sheet metal surround mounting system?
John
Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
I would think a visual check with camera would be enough.
Now the real question is what would a missing tile(fell off early in reentry) look like for damage.
1. heat would burn through the 4mm steel.
2. heat would permanently weaken steel but no hole.
So if just weakened it could be cut out and patched.
So for a hole and the fact that they have header tanks would this doom the landing? Maybe the depressurized tank would not be able to handle the aero forces?
Why not cut out the bad section - no different than the square access holes they are using now.Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
I would think a visual check with camera would be enough.
Now the real question is what would a missing tile(fell off early in reentry) look like for damage.
1. heat would burn through the 4mm steel.
2. heat would permanently weaken steel but no hole.
So if just weakened it could be cut out and patched.
So for a hole and the fact that they have header tanks would this doom the landing? Maybe the depressurized tank would not be able to handle the aero forces?
I doubt they would cut into the tank wall, that just unnecessarily weakens it further.. They could weld a doubler sheet over that spot, and then put a (slightly thinner) tile over the whole mess.
Why not cut out the bad section - no different than the square access holes they are using now.Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
I would think a visual check with camera would be enough.
Now the real question is what would a missing tile(fell off early in reentry) look like for damage.
1. heat would burn through the 4mm steel.
2. heat would permanently weaken steel but no hole.
So if just weakened it could be cut out and patched.
So for a hole and the fact that they have header tanks would this doom the landing? Maybe the depressurized tank would not be able to handle the aero forces?
I doubt they would cut into the tank wall, that just unnecessarily weakens it further.. They could weld a doubler sheet over that spot, and then put a (slightly thinner) tile over the whole mess.
Looking at the possibilities for tiling the flippers it seems the more curves the more tiles required. If they can keep the edges relatively straight it will help minimise the number of tiles required. That said in the battle between aerodynamics and tile count I think aerodynamics wins.TBH at this stage in the game these are early test patches. This articles not likely to go very high or very far.
One other thing, with the standard tiles which is the best configuration for the main tile type? Hexagon flat sides aligned upwards or hexagon vertices pointing upwards? Currently the test patch is installed flat side aligned upwards, but I would have thought the other orientation would provide less vertical tile gaps.
Sorry - just now able to get back to this.Why not cut out the bad section - no different than the square access holes they are using now.Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
I would think a visual check with camera would be enough.
Now the real question is what would a missing tile(fell off early in reentry) look like for damage.
1. heat would burn through the 4mm steel.
2. heat would permanently weaken steel but no hole.
So if just weakened it could be cut out and patched.
So for a hole and the fact that they have header tanks would this doom the landing? Maybe the depressurized tank would not be able to handle the aero forces?
I doubt they would cut into the tank wall, that just unnecessarily weakens it further.. They could weld a doubler sheet over that spot, and then put a (slightly thinner) tile over the whole mess.
Still need the doubler around the cutout, so what does it gain?
Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
I'm thinking about an indepent one piece heatshield that could be bolt to SS and removed easily so they wont be a lot of time consumming checks. (I think it should be the same for engines).
Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
I'm thinking about an indepent one piece heatshield that could be bolt to SS and removed easily so they wont be a lot of time consumming checks. (I think it should be the same for engines).
One large piece doesn't make checks easier. And large single piece would be heavy and close to impossible to manufacture (the only viable option would be soft blanket like material, but no such tech for the temperatures involved has been developed (soft blankets are good for ~1000K like Shuttle leeward, but Stainless steel doesn't need protection against 1000K, it needs protection against 1400-1600K on windward side). Also shield penetrating bolts add difficulty and failure points -- the current small tiles have a smart solution for tat problem: non penetrating snap-on studs.
Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
I'm thinking about an indepent one piece heatshield that could be bolt to SS and removed easily so they wont be a lot of time consumming checks. (I think it should be the same for engines).
One large piece doesn't make checks easier. And large single piece would be heavy and close to impossible to manufacture (the only viable option would be soft blanket like material, but no such tech for the temperatures involved has been developed (soft blankets are good for ~1000K like Shuttle leeward, but Stainless steel doesn't need protection against 1000K, it needs protection against 1400-1600K on windward side). Also shield penetrating bolts add difficulty and failure points -- the current small tiles have a smart solution for tat problem: non penetrating snap-on studs.
I was suggesting multiple heatshields that are interchanged so we don't lose time checking while ideling SS.
Couldn´t they just use some material painted... like Starlite? It seems a chemist guy rediscovered the formula and posted it on Youtube... that, or something else.
Even if they are all the same hexagonal tiles, won´t they have to check them all after each landing? Won´t that and replacing any damaged tile still be expensive and labor intensive?
I'm thinking about an indepent one piece heatshield that could be bolt to SS and removed easily so they wont be a lot of time consumming checks. (I think it should be the same for engines).
One large piece doesn't make checks easier. And large single piece would be heavy and close to impossible to manufacture (the only viable option would be soft blanket like material, but no such tech for the temperatures involved has been developed (soft blankets are good for ~1000K like Shuttle leeward, but Stainless steel doesn't need protection against 1000K, it needs protection against 1400-1600K on windward side). Also shield penetrating bolts add difficulty and failure points -- the current small tiles have a smart solution for tat problem: non penetrating snap-on studs.
I was suggesting multiple heatshields that are interchanged so we don't lose time checking while ideling SS.
How much time and infrastructure would be required to change out the heat shields on something the size of a Starship? :o
How much time and infrastructure would be required to change out the heat shields on something the size of a Starship? :oIndeed.
You guys find it easy to colonize Mars and hard to interchange a heatshield? ;D if so I would prefer being more down to earth and let talk about how to put the american flag on the red planet soil before chinese do the same it's more interesting for me than the aspirationals goals (dreams) of EM.Not just any heat shield, you want a single unitary heat shield, that is also swappable. While being made out of materials chosen for their thermal characteristics, not their durability.
10 tons for heatshield any respectable overhead crane could manage such a weight.it would be a sail so a building would be needed. And it'd be nearly as flexible as sail cloth. It'd need lots of hands and eyes to apply and verify it was installed properly.
You guys find it easy to colonize Mars and hard to interchange a heatshield? ;D if so I would prefer being more down to earth and let talk about how to put the american flag on the red planet soil before chinese do the same it's more interesting for me than the aspirationals goals (dreams) of EM.Not just any heat shield, you want a single unitary heat shield, that is also swappable. While being made out of materials chosen for their thermal characteristics, not their durability.
There's a reason the shuttle used tiles, and starship is also using hexagonal tiles.
10 tons for heatshield any respectable overhead crane could manage such a weight.it would be a sail so a building would be needed. And it'd be nearly as flexible as sail cloth. It'd need lots of hands and eyes to apply and verify it was installed properly.
Please refere to the above response, it must be as easy as interchanging an airliner engine.
Please refere to the above response, it must be as easy as interchanging an airliner engine.
Do you know what it takes and how long to change out an airliner engine? :o
https://blog.virginatlantic.com/change-aircraft-engine/ (https://blog.virginatlantic.com/change-aircraft-engine/)
You'll notice they swap one engine, not an entire wing at once.Please refere to the above response, it must be as easy as interchanging an airliner engine.
Do you know what it takes and how long to change out an airliner engine? :o
https://blog.virginatlantic.com/change-aircraft-engine/ (https://blog.virginatlantic.com/change-aircraft-engine/)
I saw a documentary on National Geographic it was too easy.
You'll notice they swap one engine, not an entire wing at once.Please refere to the above response, it must be as easy as interchanging an airliner engine.
Do you know what it takes and how long to change out an airliner engine? :o
https://blog.virginatlantic.com/change-aircraft-engine/ (https://blog.virginatlantic.com/change-aircraft-engine/)
I saw a documentary on National Geographic it was too easy.
Tiles are the smart way of doing heat shields.
Why swap the whole heat shield if only a few tiles are damaged?You'll notice they swap one engine, not an entire wing at once.Please refere to the above response, it must be as easy as interchanging an airliner engine.
Do you know what it takes and how long to change out an airliner engine? :o
https://blog.virginatlantic.com/change-aircraft-engine/ (https://blog.virginatlantic.com/change-aircraft-engine/)
I saw a documentary on National Geographic it was too easy.
Tiles are the smart way of doing heat shields.
I was also suggesting swaping all the heat shield.
Why swap the whole heat shield if only a few tiles are damaged?You'll notice they swap one engine, not an entire wing at once.Please refere to the above response, it must be as easy as interchanging an airliner engine.
Do you know what it takes and how long to change out an airliner engine? :o
https://blog.virginatlantic.com/change-aircraft-engine/ (https://blog.virginatlantic.com/change-aircraft-engine/)
I saw a documentary on National Geographic it was too easy.
Tiles are the smart way of doing heat shields.
I was also suggesting swaping all the heat shield.
Swapping a 10 ton heat shield is going to be MUCH slower than scanning the shield, then swapping 4-5 tiles.Why swap the whole heat shield if only a few tiles are damaged?You'll notice they swap one engine, not an entire wing at once.Please refere to the above response, it must be as easy as interchanging an airliner engine.
Do you know what it takes and how long to change out an airliner engine? :o
https://blog.virginatlantic.com/change-aircraft-engine/ (https://blog.virginatlantic.com/change-aircraft-engine/)
I saw a documentary on National Geographic it was too easy.
Tiles are the smart way of doing heat shields.
I was also suggesting swaping all the heat shield.
To make SS ready to fly as quickly as possible.
You guys find it easy to colonize Mars and hard to interchange a heatshield? ;D if so I would prefer being more down to earth and let talk about how to put the american flag on the red planet soil before chinese do the same it's more interesting for me than the aspirationals goals (dreams) of EM.Not just any heat shield, you want a single unitary heat shield, that is also swappable. While being made out of materials chosen for their thermal characteristics, not their durability.
There's a reason the shuttle used tiles, and starship is also using hexagonal tiles.
Those hexagonal tiles could be fixed to a structure that could be disassembled or fixed to SS, if you won't to operat quickly you won't be able to aford ideling all the spacecraft just because one tile has been damaged and need time to get repaired.
10 tons for heatshield any respectable overhead crane could manage such a weight.it would be a sail so a building would be needed. And it'd be nearly as flexible as sail cloth. It'd need lots of hands and eyes to apply and verify it was installed properly.
Please refere to the above response, it must be as easy as interchanging an airliner engine.
Please refere to the above response, it must be as easy as interchanging an airliner engine.
Do you know what it takes and how long to change out an airliner engine? :o
https://blog.virginatlantic.com/change-aircraft-engine/ (https://blog.virginatlantic.com/change-aircraft-engine/)
I saw a documentary on National Geographic it was too easy.
https://www.youtube.com/watch?v=lU4mXljJRC8
I saw a documentary on National Geographic it was too easy.
https://www.youtube.com/watch?v=lU4mXljJRC8
Rapid inspection of tiles and replacement of only the defective ones is a solvable problem in an era of computer vision.It would have been a solved problem in the 90's if Marshall had let CMU install their shuttle inspection robot but apparently it was too risky as it might crash into the vehicle it was scanning (despite CMU's plan to use a very slow moving vehicle to carry the arm carrying the sensor package).
- There is also going to be thermal expansion mismatch between the heat shield and the underlying structure. Because of this tile or panels can only be so large before expansion joints have to be incorporated into the heat shield.True. In the case of the Shuttle tiles versus aluminum skin it was something like 3:1 in favor of the skin.
Ideally you want a thermal protection system that never gets damaged, then you don't care how long it takes to repair.
That's a fantasy, but the toughness of the tiles and gentleness of operations is an important part of the engineering.
Assuming that a single tile has been damaged and needs to be replaced, how would they do this? Do they have to use the narrow gap between tiles to get underneath or do they do something from the front of the damaged tile to remove it?Well, the tile is damaged already, so it's already written off. Shatter it with a hammer, pry off the remains, straighten the pins, and attach a new tile?
Seems reasonable, but when attaching the new tile won't the face of the tile insulate the studs from their needed electrical connection for the weld?Assuming that a single tile has been damaged and needs to be replaced, how would they do this? Do they have to use the narrow gap between tiles to get underneath or do they do something from the front of the damaged tile to remove it?Well, the tile is damaged already, so it's already written off. Shatter it with a hammer, pry off the remains, straighten the pins, and attach a new tile?
Seems reasonable, but when attaching the new tile won't the face of the tile insulate the studs from their needed electrical connection for the weld?Assuming that a single tile has been damaged and needs to be replaced, how would they do this? Do they have to use the narrow gap between tiles to get underneath or do they do something from the front of the damaged tile to remove it?Well, the tile is damaged already, so it's already written off. Shatter it with a hammer, pry off the remains, straighten the pins, and attach a new tile?
I wonder what the optimal tile size is? There must be some cross over point as you get larger where it starts to become less easy to manufacture, install or handle, likewise getting smaller. Too small, too many and hence heavy, too large, need to be curved.
I suspect there will have to have some 'custom' tiles rather than hexagons for things like leading edgers and the nose.
For those who don't go out to an airport and look at a 777 or an airbus 380. the Shuttle was about DC9 sized. Bigger than any previous vehicle, but still quite small.
Rapid inspection of tiles and replacement of only the defective ones is a solvable problem in an era of computer vision.It would have been a solved problem in the 90's if Marshall had let CMU install their shuttle inspection robot but apparently it was too risky as it might crash into the vehicle it was scanning (despite CMU's plan to use a very slow moving vehicle to carry the arm carrying the sensor package).
I'm guessing that would have made several hundred staff surplus to requirement as well.
- Heat shields have very little strength. They usually have a thin outer shell, or ablator, with insulation underneath. The insulation may be either rigid, like the Shuttle tile, or in the form of felt or batting. The whole has very little strength because you are trying to make it as light and as insulating as possible.
- There is also going to be thermal expansion mismatch between the heat shield and the underlying structure. Because of this tile or panels can only be so large before expansion joints have to be incorporated into the heat shield.
- A large heat shield would not be self supporting. It would rip apart of its own weight. Adding reinforcements to it only makes it heavier. Not good.
John
RMS/OBSS won because it really was the best solution for reducing risk, despite being heavier than all the free-flyer solutions, including CMU's (and AERCam).I suspect we're talking at cross purposes. The CMU project I am referring to was for a robot to inspect shuttle TPS on the ground during refurbishment in the hangar.
RMS/OBSS won because it really was the best solution for reducing risk, despite being heavier than all the free-flyer solutions, including CMU's (and AERCam).I suspect we're talking at cross purposes. The CMU project I am referring to was for a robot to inspect shuttle TPS on the ground during refurbishment in the hangar.
Fair enough. I mistook it for one of the in-flight robotic proposals.No. On the ground refurb. The sensor package was designed to use multiple sensors to detect both surface visible damage and sub surface damage brought on by over temperature stressing of the tiles. In principle with every tile bar coded it could detect a damage one and issue the re-order immediately.
I wonder what the optimal tile size is? There must be some cross over point as you get larger where it starts to become less easy to manufacture, install or handle, likewise getting smaller. Too small, too many and hence heavy, too large, need to be curved.
I suspect there will have to have some 'custom' tiles rather than hexagons for things like leading edgers and the nose.
Well, since SpaceX has hired really smart engineers to work out the details of its TPS system, my guess would be, about the size of the tiles we have seen. :^)
John
I get the feeling, that a lot people here assume that the heat tilds are based on the shuttle design. They are not. They don't have to protect so much (steel, not aluminum below), and they can weight more.
This is starship, so they won't optimize to the end to save weight. When the equation is 2 tons less capacity for a more robust heat shield, they will take the 2 tons. Because it is still cheaper to start it 101 instead of 100 times, than to have an intensive checkup, every time it landed.
Mars, exactly. They want to land this thing on mars, and the thermal envelop for loosing speed on mars will be not much apart from earth reentry. And what they clearly can not do, it trying to fix the heat shield on mars. It has to be rock solid, and I am sure, they knew that from day one.I get the feeling, that a lot people here assume that the heat tilds are based on the shuttle design. They are not. They don't have to protect so much (steel, not aluminum below), and they can weight more.
This is starship, so they won't optimize to the end to save weight. When the equation is 2 tons less capacity for a more robust heat shield, they will take the 2 tons. Because it is still cheaper to start it 101 instead of 100 times, than to have an intensive checkup, every time it landed.
But still 10 tons or so (more than F9 payload to GTO) of weight to escape earth and mars gravity is a huge payload loss and fuel consumming burden.
There's always a plan B if the heat shield is damaged fly them home and transfer to another starship for return to Earth, then repair in orbit if possible else park in a high orbit for posterity or let it burn up after all samples and crew have been transfered out.Mars, exactly. They want to land this thing on mars, and the thermal envelop for loosing speed on mars will be not much apart from earth reentry. And what they clearly can not do, it trying to fix the heat shield on mars. It has to be rock solid, and I am sure, they knew that from day one.I get the feeling, that a lot people here assume that the heat tilds are based on the shuttle design. They are not. They don't have to protect so much (steel, not aluminum below), and they can weight more.
This is starship, so they won't optimize to the end to save weight. When the equation is 2 tons less capacity for a more robust heat shield, they will take the 2 tons. Because it is still cheaper to start it 101 instead of 100 times, than to have an intensive checkup, every time it landed.
But still 10 tons or so (more than F9 payload to GTO) of weight to escape earth and mars gravity is a huge payload loss and fuel consumming burden.
I get the feeling, that a lot people here assume that the heat tilds are based on the shuttle design. They are not. They don't have to protect so much (steel, not aluminum below), and they can weight more.
This is starship, so they won't optimize to the end to save weight. When the equation is 2 tons less capacity for a more robust heat shield, they will take the 2 tons. Because it is still cheaper to start it 101 instead of 100 times, than to have an intensive checkup, every time it landed.
Doesn't work too well if you're depending on aerocapture or braking to get into orbit.There's always a plan B if the heat shield is damaged fly them home and transfer to another starship for return to Earth, then repair in orbit if possible else park in a high orbit for posterity or let it burn up after all samples and crew have been transfered out.Mars, exactly. They want to land this thing on mars, and the thermal envelop for loosing speed on mars will be not much apart from earth reentry. And what they clearly can not do, it trying to fix the heat shield on mars. It has to be rock solid, and I am sure, they knew that from day one.I get the feeling, that a lot people here assume that the heat tilds are based on the shuttle design. They are not. They don't have to protect so much (steel, not aluminum below), and they can weight more.
This is starship, so they won't optimize to the end to save weight. When the equation is 2 tons less capacity for a more robust heat shield, they will take the 2 tons. Because it is still cheaper to start it 101 instead of 100 times, than to have an intensive checkup, every time it landed.
But still 10 tons or so (more than F9 payload to GTO) of weight to escape earth and mars gravity is a huge payload loss and fuel consumming burden.
10 tons sounds like a lot, but the current design assumes a loaded dry weight (ship dry weight+payload) of 270 tons- so the heat shield is less than 5%, close to 3% of that number. Starship has a ROUNDING ERROR on it's lift capacity bigger than some launcher's max capacity.I get the feeling, that a lot people here assume that the heat tilds are based on the shuttle design. They are not. They don't have to protect so much (steel, not aluminum below), and they can weight more.
This is starship, so they won't optimize to the end to save weight. When the equation is 2 tons less capacity for a more robust heat shield, they will take the 2 tons. Because it is still cheaper to start it 101 instead of 100 times, than to have an intensive checkup, every time it landed.
But still 10 tons or so (more than F9 payload to GTO) of weight to escape earth and mars gravity is a huge payload loss and fuel consumming burden.
True, I had forgotten about that. How tough are aerocapture requirements vs re-entry requirements?Doesn't work too well if you're depending on aerocapture or braking to get into orbit.There's always a plan B if the heat shield is damaged fly them home and transfer to another starship for return to Earth, then repair in orbit if possible else park in a high orbit for posterity or let it burn up after all samples and crew have been transfered out.Mars, exactly. They want to land this thing on mars, and the thermal envelop for loosing speed on mars will be not much apart from earth reentry. And what they clearly can not do, it trying to fix the heat shield on mars. It has to be rock solid, and I am sure, they knew that from day one.I get the feeling, that a lot people here assume that the heat tilds are based on the shuttle design. They are not. They don't have to protect so much (steel, not aluminum below), and they can weight more.But still 10 tons or so (more than F9 payload to GTO) of weight to escape earth and mars gravity is a huge payload loss and fuel consumming burden.
This is starship, so they won't optimize to the end to save weight. When the equation is 2 tons less capacity for a more robust heat shield, they will take the 2 tons. Because it is still cheaper to start it 101 instead of 100 times, than to have an intensive checkup, every time it landed.
I have a question.To recap my quick estimates in the Moon Starship mission profile thread:
If we have a moon SS launched from the moon surface to the earth LEO.
No heat shield.
Aerocapture doesn't need to be done because you have less than earth escape velocity.
So you still need to slow down slowly because we don't have a heat shield.
How many passes are needed to slow down to a LEO orbit?
Does the time needed to do this greatly increase radiation exposer?
Asking in this thread because this thread has to do with heat loads and protection for planetary entry.
You look like you are running a steady-state calculation. But what about a thermal mass one? An eliptcal orbit would give starship plenty of time to dissapate reentry heating before the next pass. So how much thermal energy can Starship hold without letting the structure pass 1000 degrees?I have a question.To recap my quick estimates in the Moon Starship mission profile thread:
If we have a moon SS launched from the moon surface to the earth LEO.
No heat shield.
Aerocapture doesn't need to be done because you have less than earth escape velocity.
So you still need to slow down slowly because we don't have a heat shield.
How many passes are needed to slow down to a LEO orbit?
Does the time needed to do this greatly increase radiation exposer?
Asking in this thread because this thread has to do with heat loads and protection for planetary entry.
Excess energy of a 100 t Starship going from 11 km/s to say 8 km/s at perigee is 1/2*100 t*((11 km/s)^2-(8 km/s)^2) = 2.9 TJ
This will be dissipated through thermal black-body radiation from the skin. Lets assume 623 K (350 °C, maxium temperature of Space Shuttle top TPS blankets) evenly over the whole Starship area (BBQ roll).
Stefan-Boltzmann with 623 K, emissivity=1: 8.5 kW/m^2. Times 1300 m^2 = 11 MW of thermal radiation.
2.9 TJ/11 MW = 260 000 s or very close to 3 days.
This would take many years considering that the orbital period starts out at many days and the time at maximum drag is at most a few minutes and it completely neglects incoming heat from the Sun and Earth during aerobraking.
Yes, I neglected that since Moon Starship will be well insulated (it is supposed to support humans and store cryogens in LLO and on the lunar surface) and each aerobraking session is just minutes long.You look like you are running a steady-state calculation. But what about a thermal mass one? An eliptcal orbit would give starship plenty of time to dissapate reentry heating before the next pass. So how much thermal energy can Starship hold without letting the structure pass 1000 degrees?I have a question.To recap my quick estimates in the Moon Starship mission profile thread:
If we have a moon SS launched from the moon surface to the earth LEO.
No heat shield.
Aerocapture doesn't need to be done because you have less than earth escape velocity.
So you still need to slow down slowly because we don't have a heat shield.
How many passes are needed to slow down to a LEO orbit?
Does the time needed to do this greatly increase radiation exposer?
Asking in this thread because this thread has to do with heat loads and protection for planetary entry.
Excess energy of a 100 t Starship going from 11 km/s to say 8 km/s at perigee is 1/2*100 t*((11 km/s)^2-(8 km/s)^2) = 2.9 TJ
This will be dissipated through thermal black-body radiation from the skin. Lets assume 623 K (350 °C, maxium temperature of Space Shuttle top TPS blankets) evenly over the whole Starship area (BBQ roll).
Stefan-Boltzmann with 623 K, emissivity=1: 8.5 kW/m^2. Times 1300 m^2 = 11 MW of thermal radiation.
2.9 TJ/11 MW = 260 000 s or very close to 3 days.
This would take many years considering that the orbital period starts out at many days and the time at maximum drag is at most a few minutes and it completely neglects incoming heat from the Sun and Earth during aerobraking.
I have a question.To recap my quick estimates in the Moon Starship mission profile thread:
If we have a moon SS launched from the moon surface to the earth LEO.
No heat shield.
Aerocapture doesn't need to be done because you have less than earth escape velocity.
So you still need to slow down slowly because we don't have a heat shield.
How many passes are needed to slow down to a LEO orbit?
Does the time needed to do this greatly increase radiation exposer?
Asking in this thread because this thread has to do with heat loads and protection for planetary entry.
Excess energy of a 100 t Starship going from 11 km/s to say 8 km/s at perigee is 1/2*100 t*((11 km/s)^2-(8 km/s)^2) = 2.9 TJ
This will be dissipated through thermal black-body radiation from the skin. Lets assume 623 K (350 °C, maxium temperature of Space Shuttle top TPS blankets) evenly over the whole Starship area (BBQ roll).
Stefan-Boltzmann with 623 K, emissivity=1: 8.5 kW/m^2. Times 1300 m^2 = 11 MW of thermal radiation.
2.9 TJ/11 MW = 260 000 s or very close to 3 days.
This would take many years considering that the orbital period starts out at many days and the time at maximum drag is at most a few minutes and it completely neglects incoming heat from the Sun and Earth during aerobraking.
I have a question.To recap my quick estimates in the Moon Starship mission profile thread:
If we have a moon SS launched from the moon surface to the earth LEO.
No heat shield.
Aerocapture doesn't need to be done because you have less than earth escape velocity.
So you still need to slow down slowly because we don't have a heat shield.
How many passes are needed to slow down to a LEO orbit?
Does the time needed to do this greatly increase radiation exposer?
Asking in this thread because this thread has to do with heat loads and protection for planetary entry.
Excess energy of a 100 t Starship going from 11 km/s to say 8 km/s at perigee is 1/2*100 t*((11 km/s)^2-(8 km/s)^2) = 2.9 TJ
This will be dissipated through thermal black-body radiation from the skin. Lets assume 623 K (350 °C, maxium temperature of Space Shuttle top TPS blankets) evenly over the whole Starship area (BBQ roll).
Stefan-Boltzmann with 623 K, emissivity=1: 8.5 kW/m^2. Times 1300 m^2 = 11 MW of thermal radiation.
2.9 TJ/11 MW = 260 000 s or very close to 3 days.
This would take many years considering that the orbital period starts out at many days and the time at maximum drag is at most a few minutes and it completely neglects incoming heat from the Sun and Earth during aerobraking.
I have a question.To recap my quick estimates in the Moon Starship mission profile thread:
If we have a moon SS launched from the moon surface to the earth LEO.
No heat shield.
Aerocapture doesn't need to be done because you have less than earth escape velocity.
So you still need to slow down slowly because we don't have a heat shield.
How many passes are needed to slow down to a LEO orbit?
Does the time needed to do this greatly increase radiation exposer?
Asking in this thread because this thread has to do with heat loads and protection for planetary entry.
Excess energy of a 100 t Starship going from 11 km/s to say 8 km/s at perigee is 1/2*100 t*((11 km/s)^2-(8 km/s)^2) = 2.9 TJ
This will be dissipated through thermal black-body radiation from the skin. Lets assume 623 K (350 °C, maxium temperature of Space Shuttle top TPS blankets) evenly over the whole Starship area (BBQ roll).
Stefan-Boltzmann with 623 K, emissivity=1: 8.5 kW/m^2. Times 1300 m^2 = 11 MW of thermal radiation.
2.9 TJ/11 MW = 260 000 s or very close to 3 days.
This would take many years considering that the orbital period starts out at many days and the time at maximum drag is at most a few minutes and it completely neglects incoming heat from the Sun and Earth during aerobraking.
Thankfully, the vast majority (something on the order of 99% IIRC) of reentry heating/energy loss occurs in the shockwave ahead of the vehicle and is never actually absorbed. Also, since SS is steel, the body can accept much higher temperatures than the shuttle, on the order of 1000C. This means that even without a heatshield, you can aerobrake pretty aggressively, and thermal emission occurs much faster.
Finally, you can use evaporative cooling by letting the heat boil your propellant, and just venting the gas. Assuming only 1% of the reentry heat is actually absorbed by the vehicle, your 2.9 TJ number requires around 150-200kg of propellant to be vaporized (assuming I got my math right), which is trivial.
Since heat can be shedded so easily by vaporizing a small amount of fuel, the only question remaining is how many aerobraking passes must occur.
If we handwave internal heat transfer during reentry and just assume the vehicle can accept enough energy to heat 30 tons worth of steel on the windward side to 1000C, then assuming 1% of reentry energy is accepted by the vehicle, then the specific heat of steel of 0.5 J/K suggests that 2 aerobraking passes are sufficient. Since the lunar return trajectory has a high eccentricity, it only takes a small amount of energy loss at perigee to greatly lower apogee. Thus, the intermediate orbit between brakings can be expected to be fairly low and only slightly eccentric, with a period on the order of hours and not days. It might even slip below Van Allen belt entirely, which means the radiation exposure during this time would be quite low.
The Starship Moon mission profile (https://forum.nasaspaceflight.com/index.php?topic=50817.0) tread, but it was the same analysis just a slightly different formulation.
To recap my quick estimates in the Moon Starship mission profile thread:
[...]
I must have missed that.
Thanks
Is that the "moon starship" thread?
Yes, that is the secret to why reentry and aerocapture is possible at all - forming a shock wave at some distance from the surface which dumps almost all of the energy into the air. The role of the TPS is to make the proximity to that super heated air survivable.I have a question.To recap my quick estimates in the Moon Starship mission profile thread:
If we have a moon SS launched from the moon surface to the earth LEO.
No heat shield.
Aerocapture doesn't need to be done because you have less than earth escape velocity.
So you still need to slow down slowly because we don't have a heat shield.
How many passes are needed to slow down to a LEO orbit?
Does the time needed to do this greatly increase radiation exposer?
Asking in this thread because this thread has to do with heat loads and protection for planetary entry.
Excess energy of a 100 t Starship going from 11 km/s to say 8 km/s at perigee is 1/2*100 t*((11 km/s)^2-(8 km/s)^2) = 2.9 TJ
This will be dissipated through thermal black-body radiation from the skin. Lets assume 623 K (350 °C, maxium temperature of Space Shuttle top TPS blankets) evenly over the whole Starship area (BBQ roll).
Stefan-Boltzmann with 623 K, emissivity=1: 8.5 kW/m^2. Times 1300 m^2 = 11 MW of thermal radiation.
2.9 TJ/11 MW = 260 000 s or very close to 3 days.
This would take many years considering that the orbital period starts out at many days and the time at maximum drag is at most a few minutes and it completely neglects incoming heat from the Sun and Earth during aerobraking.
Thankfully, the vast majority (something on the order of 99% IIRC) of reentry heating/energy loss occurs in the shockwave ahead of the vehicle and is never actually absorbed. Also, since SS is steel, the body can accept much higher temperatures than the shuttle, on the order of 1000C. This means that even without a heatshield, you can aerobrake pretty aggressively, and thermal emission occurs much faster.
Finally, you can use evaporative cooling by letting the heat boil your propellant, and just venting the gas. Assuming only 1% of the reentry heat is actually absorbed by the vehicle, your 2.9 TJ number requires around 150-200kg of propellant to be vaporized (assuming I got my math right), which is trivial.
Since heat can be shedded so easily by vaporizing a small amount of fuel, the only question remaining is how many aerobraking passes must occur.
If we handwave internal heat transfer during reentry and just assume the vehicle can accept enough energy to heat 30 tons worth of steel on the windward side to 1000C, then assuming 1% of reentry energy is accepted by the vehicle, then the specific heat of steel of 0.5 J/K suggests that 2 aerobraking passes are sufficient. Since the lunar return trajectory has a high eccentricity, it only takes a small amount of energy loss at perigee to greatly lower apogee. Thus, the intermediate orbit between brakings can be expected to be fairly low and only slightly eccentric, with a period on the order of hours and not days. It might even slip below Van Allen belt entirely, which means the radiation exposure during this time would be quite low.
- I don't assume they will be based solely on Shuttle tile. I suspect that they will make use of the NASA research in this area and may add some novel twists of their own.Definitely. Especially the later stuff like ROCCI.
- We are pretty sure they would like to mechanically fasten their tile. Shuttle tile bonding probably won't work for their interface temperature and anyway bonding was a pain in the neck.The key parameter would be the tile back face temperature.
I remember in the movie 2010 (I know, it's fiction) they used an inflatable cocoon to do an aerobrake in Jupiter. Since NASA has already been experimenting with this concept, I wonder if something like that could be done on SS to help matters in returning form LLO to LEO this way.Almost certainly not.
True, I had forgotten about that. How tough are aerocapture requirements vs re-entry requirements?Doesn't work too well if you're depending on aerocapture or braking to get into orbit.There's always a plan B if the heat shield is damaged fly them home and transfer to another starship for return to Earth, then repair in orbit if possible else park in a high orbit for posterity or let it burn up after all samples and crew have been transfered out.Mars, exactly. They want to land this thing on mars, and the thermal envelop for loosing speed on mars will be not much apart from earth reentry. And what they clearly can not do, it trying to fix the heat shield on mars. It has to be rock solid, and I am sure, they knew that from day one.I get the feeling, that a lot people here assume that the heat tilds are based on the shuttle design. They are not. They don't have to protect so much (steel, not aluminum below), and they can weight more.But still 10 tons or so (more than F9 payload to GTO) of weight to escape earth and mars gravity is a huge payload loss and fuel consumming burden.
This is starship, so they won't optimize to the end to save weight. When the equation is 2 tons less capacity for a more robust heat shield, they will take the 2 tons. Because it is still cheaper to start it 101 instead of 100 times, than to have an intensive checkup, every time it landed.
That's two static fires for SN4 so far......
Have any of the test-fit heat tiles (3 sets) fallen off or broken?
So with 3 engines they can stay attached through 2 engine startup/shutdown cycles.That's two static fires for SN4 so far......
Have any of the test-fit heat tiles (3 sets) fallen off or broken?
Well at least there's an answer to my question thanks to Nomadd and his wanderings!
Looks like they have survived so far intact.
So with 3 engines they can stay attached through 2 engine startup/shutdown cycles.That's two static fires for SN4 so far......
Have any of the test-fit heat tiles (3 sets) fallen off or broken?
Well at least there's an answer to my question thanks to Nomadd and his wanderings!
Looks like they have survived so far intact.
That was not a guaranteed outcome.
So should the next big milestone be the first hop off the ground? Full loading of the tanks to thermally stress the TPS mounting hardware?
Oops.So with 3 engines they can stay attached through 2 engine startup/shutdown cycles.That's two static fires for SN4 so far......
Have any of the test-fit heat tiles (3 sets) fallen off or broken?
Well at least there's an answer to my question thanks to Nomadd and his wanderings!
Looks like they have survived so far intact.
That was not a guaranteed outcome.
So should the next big milestone be the first hop off the ground? Full loading of the tanks to thermally stress the TPS mounting hardware?
Only 1 engine so far.......
~1750K is peak heating expected on about 20% of Starship for LEO entry, ~1600K on 20%. Rest drops below 1450K, so no heat shield needed. Radiative cooling at T^4 takes care of 60% of the ship. Another reason for steel.
Back in Jan 2019, EM tweeted that 60% of Starship wouldn't need any heat shield at all for a LEO reentry.Quote~1750K is peak heating expected on about 20% of Starship for LEO entry, ~1600K on 20%. Rest drops below 1450K, so no heat shield needed. Radiative cooling at T^4 takes care of 60% of the ship. Another reason for steel.
a) have we seen any updates since then that contradict this?
b) what would this look like? I assume nose and fins would need TPS; where else would?
Not disputing, just trying to understand, but why is the centreline the highest temp?Back in Jan 2019, EM tweeted that 60% of Starship wouldn't need any heat shield at all for a LEO reentry.Quote~1750K is peak heating expected on about 20% of Starship for LEO entry, ~1600K on 20%. Rest drops below 1450K, so no heat shield needed. Radiative cooling at T^4 takes care of 60% of the ship. Another reason for steel.
a) have we seen any updates since then that contradict this?
b) what would this look like? I assume nose and fins would need TPS; where else would?
The whole centerline should be the highest. Nose slightly higher depending in Angle of Attack.
At 90deg nose and centerline should be close to the same temp. If not make the nose blunter.
This is the first part of the ship to slow and divert the supersonic flow therefore the flow comes closer. The peak heat is mostly radiation which is determined by the temp and observable half sphere. I am totally guessing here as I try to imagine myself as an air molecule travelling at 6km/s at an immovable barrier. On the edges you have flow coming from the centerline that can divert the flow away from the body. The edge also sees less angle of hot stuff.I've been struggling to find reentry temperature maps of capsules myself. The shuttle ones I've found (including the one you posted) certainly suggest that the main body is (comparatively) cool, but I know the angle of attack for Starship is very different.
You can also see this with like the shuttle temp map.
https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system#/media/File:STS-3_infrared_on_reentry.jpg
remember the AoA of the shuttle was about 30-40? so the edges of the wings are first in line for heat.
Is there a temp map of the dragon?
EDIT added shuttle heat map
This is the first part of the ship to slow and divert the supersonic flow therefore the flow comes closer. The peak heat is mostly radiation which is determined by the temp and observable half sphere. I am totally guessing here as I try to imagine myself as an air molecule travelling at 6km/s at an immovable barrier. On the edges you have flow coming from the centerline that can divert the flow away from the body. The edge also sees less angle of hot stuff.I've been struggling to find reentry temperature maps of capsules myself. The shuttle ones I've found (including the one you posted) certainly suggest that the main body is (comparatively) cool, but I know the angle of attack for Starship is very different.
You can also see this with like the shuttle temp map.
https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system#/media/File:STS-3_infrared_on_reentry.jpg
remember the AoA of the shuttle was about 30-40? so the edges of the wings are first in line for heat.
Is there a temp map of the dragon?
EDIT added shuttle heat map
My, probably naive, assumption was that peak heating would be where the shock wave rapidly changes direction, so on the edges of the fins, etc.
This is the first part of the ship to slow and divert the supersonic flow therefore the flow comes closer. The peak heat is mostly radiation which is determined by the temp and observable half sphere. I am totally guessing here as I try to imagine myself as an air molecule travelling at 6km/s at an immovable barrier. On the edges you have flow coming from the centerline that can divert the flow away from the body. The edge also sees less angle of hot stuff.I've been struggling to find reentry temperature maps of capsules myself. The shuttle ones I've found (including the one you posted) certainly suggest that the main body is (comparatively) cool, but I know the angle of attack for Starship is very different.
You can also see this with like the shuttle temp map.
https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system#/media/File:STS-3_infrared_on_reentry.jpg
remember the AoA of the shuttle was about 30-40? so the edges of the wings are first in line for heat.
Is there a temp map of the dragon?
EDIT added shuttle heat map
My, probably naive, assumption was that peak heating would be where the shock wave rapidly changes direction, so on the edges of the fins, etc.
General principal. Blunt is best. Near the roots of the fins/whatever is where the flow should be quite hot.
Simple Newtonian hypersonic flow approximation is pretty good at determining pressure and heating.Simple what now? ???
John
The fun starts when you get shock/shock interference and the heat transfer can raise between 4x and 10x.I've been struggling to find reentry temperature maps of capsules myself. The shuttle ones I've found (including the one you posted) certainly suggest that the main body is (comparatively) cool, but I know the angle of attack for Starship is very different.
My, probably naive, assumption was that peak heating would be where the shock wave rapidly changes direction, so on the edges of the fins, etc.
General principal. Blunt is best. Near the roots of the fins/whatever is where the flow should be quite hot.
Newton used a model for airflow that assumed air molecules travel in straight lines, like beams of light.Simple Newtonian hypersonic flow approximation is pretty good at determining pressure and heating.Simple what now? ???
John
Simple Newtonian hypersonic flow approximation is pretty good at determining pressure and heating.Simple what now? ???
John
Intriguing.
But they still have the two separate style: one with the mounting holes (or whatever those white dots in a triangle pattern) and another, where the black cover seems continuous. No sign of the welded mounting pads however.
I like the runt of the litter. Can't seem to fit in. ;^)Yes it seems they are testing a smaller tile that is a little twisted of centre. Perhaps they want to see how well it holds up if the air can get under it and how much room they have to play with concerning gaps.
John
Does anybody know, how much the heat shield weighs? kg/m²?
Could it be that the placement of the runt tile was aligned with the group at first. And now we are seeing it in a state where the fastening method has somewhat failed?
The next question is to what extent they can replicate the conditions of reentry without Super Heavy. Remember, energy is proportional to velocity squared! Perhaps tossing it on a long suborbital trajectory at a drone ship would be sufficient?
RTLS would be a problem since near orbital velocity is much too fast for straight up, straight down to be survivable. At these speeds, you traverse the thickness of the entire atmosphere in mere seconds, and going from a near orbital 7500 m/s to 0 in 30 seconds needs 25Gs of constant accelleration. Of course, since most of that atmosphere is very thin, the bulk of your decelleration will occur much faster toward the end! This leaves flying way out over the ocean and turning around. It's hard to imagine how they'd get going more than maybe 3000-4000m/s this way, which, due to the square law, is an order of magnitude less energy than orbital reentry.
This leaves flying way out over the ocean and turning around. It's hard to imagine how they'd get going more than maybe 3000-4000m/s this way, which, due to the square law, is an order of magnitude less energy than orbital reentry.
Thanks John, I've started trying to get my head around that. If the current lockdown continues for another 8 or 9 years I might understand it all :)Simple Newtonian hypersonic flow approximation is pretty good at determining pressure and heating.Simple what now? ???
John
Reference Anderson, Hypersonics and High Temperature Gas Dynamics, 2nd ed. pg 311:
Newtonian impact theory: Cp=2*cos(phi)^2 where phi is the angle between the surface normal and freestream. This equation gives you pressure over the entire windward side of the vehicle. With the pressure you can get the velocities over the windward surface. With this and equation 6.106 and figure 6.17 you can get heating rate.
John
Did SN4 shake off a few heatshield tiles? (screenshots taken from bocachicagal photos)
First photo was from 5/15, second is from this morning.
. A NASA DRA 5.0 manned mission to Mars can be accomplished with 225 MT is mass savings and decreased programmatic and technical risk. Deep space planetary orbiters can be launched on rapid, direct trajectories decreasing trip times by more than 70%. And, with the same launch mass, a mission can be accomplished with significantly less trip time and thus, less solar and cosmic ray radiation exposure.
bocachicagal's latest and greatest pictures of the SN4 failed/removed heat shield tiles show that they were attached trough some kind of coarse-threaded screw that looks a lot like a shallow version of a self-drilling drywall anchor. I guessing it was drilled into the tile which was then pushed onto the protruding studs, locking in place.
To get maximum of data, it might make sense to do flight tests with deliberately incorrectly or incompletely attached tiles ... ommit one or two bolts, see if the method can tolerate partial attachment failures. Also what happens if a tile is missing, can the airstream get underneath adjacent tiles and lift them off - like roof shingles in a storm - causing a chain reaction.Good point.
So seeing tiles fail during tests might not necessarily be a failure per se, it could have been "supposed to fail" or "fail as expected". importance at this point is gathering lotsa data
bocachicagal's latest and greatest pictures of the SN4 failed/removed heat shield tiles show that they were attached trough some kind of coarse-threaded screw that looks a lot like a shallow version of a self-drilling drywall anchor. I guessing it was drilled into the tile which was then pushed onto the protruding studs, locking in place.
Those photos, if you zoom in reeeally close, show a hex shape to the central hole, and a hint of a crosshead screw inside.
I think the 'drywall anchor' (good analogy btw) is screwed into a hole in the white insulation layer using a hex key, and that assembly is attached to the welded-on stud with a screw. Finally, the black ceramic layer is placed on top, secured (I assume) with high-temperature cement.
Another interesting question. Could they just be a press fit cap over the studs/spigots on the skin? Then you'd just need a suction cup to pull them off.Well there is that pesky vacuum that these Starships are supposed to spend a lot of time in... no greater negative pressure than that. ;)
Which of course raises the question "Are there any flight stages where the tile could be subjected to a negative surface pressure?" The answer should be "No, never."
Another interesting question. Could they just be a press fit cap over the studs/spigots on the skin? Then you'd just need a suction cup to pull them off.Well there is that pesky vacuum that these Starships are supposed to spend a lot of time in... no greater negative pressure than that. ;)
Which of course raises the question "Are there any flight stages where the tile could be subjected to a negative surface pressure?" The answer should be "No, never."
Exactly. As long as the air from behind the tiles vents fast enough that should not be a problem.
It's not the vacuum that is a concern, it would be a pressure differential caused by a vacuum. And for the tiles there should not be any areas that have pockets of contained air from the time of launch.
As to replacing tiles, unless you are on Earth using a vacuum to suction off tiles won't likely work since there would no or little air pressure. So hopefully they are planning for a mechanical means of removing and replacing tiles.Good point. I was only considering tile replacement on earth. I'd forgotten possible on orbit and mars replacement scenarios.
bocachicagal's latest and greatest pictures of the SN4 failed/removed heat shield tiles show that they were attached trough some kind of coarse-threaded screw that looks a lot like a shallow version of a self-drilling drywall anchor. I guessing it was drilled into the tile which was then pushed onto the protruding studs, locking in place.
Those photos, if you zoom in reeeally close, show a hex shape to the central hole, and a hint of a crosshead screw inside.
I think the 'drywall anchor' (good analogy btw) is screwed into a hole in the white insulation layer using a hex key, and that assembly is attached to the welded-on stud with a screw. Finally, the black ceramic layer is placed on top, secured (I assume) with high-temperature cement.
The black coating wraps around the tile into the gap, where it would be extremely hard to consistently apply in the field, so I'm sure that they come that way from the tile production facility.
As for the fastener, I see 2 square-ish things around a center dark spot. The alignment of the squares is consistent, pointing always to the center of the tile. I think the squares are the ends of spring tabs, and they snap over the little sphere on the end of the studs we previously saw welded to the tank walls.
The radial alignment is important because it would allow the tile to remain centered in its intended location as it expands at high temperature. The snap fit onto the sphere-tipped stud allows easy installation and allows some location tolerance between the stud positions and the anchors.
Edit: two of the weld studs are visible in the same photo, but it's difficult to make out the round tip. It looks like they wanted to test out a single centered mount, but couldn't be bothered to weld on one more stud outside the triangular pattern :D
I know the material of the tile isn't that sturdy, but I'm sure it's stronger than tinsel.
One thing I’m fairly certain about is the drywall anchors screw into the back of the tile. The large threads are to distribute the load to a material with miserable tinsel strength. Sort of like drywall or a foamy ceramic. The question is, are they screwed into the tile then the wall anchors mounted to the surface in some way or are they free spinning on the stud and the tile, with three small holes for a hex key, mounted and screwed onto them?
I wonder what the wall anchors are made of. Titanium? Stainless would be really heavy. How do stainless and titanium interact?
Phil
I know the material of the tile isn't that sturdy, but I'm sure it's stronger than tinsel.
One thing I’m fairly certain about is the drywall anchors screw into the back of the tile. The large threads are to distribute the load to a material with miserable tinsel strength. Sort of like drywall or a foamy ceramic. The question is, are they screwed into the tile then the wall anchors mounted to the surface in some way or are they free spinning on the stud and the tile, with three small holes for a hex key, mounted and screwed onto them?
I wonder what the wall anchors are made of. Titanium? Stainless would be really heavy. How do stainless and titanium interact?
Phil
Hollow stainless screws shouldn't be too heavy. Maybe a six sided hole for driving in the back. Welding titanium needs a lot more perfect conditions, as in a pretty much pure Argon or He environment. (Not an expert by any definition disclaimer) A lot of extra trouble and expense to save a couple hundred pounds.
One thing I’m fairly certain about is the drywall anchors screw into the back of the tile. The large threads are to distribute the load to a material with miserable tinsel strength. Sort of like drywall or a foamy ceramic. The question is, are they screwed into the tile then the wall anchors mounted to the surface in some way or are they free spinning on the stud and the tile, with three small holes for a hex key, mounted and screwed onto them?
I know the material of the tile isn't that sturdy, but I'm sure it's stronger than tinsel.On the off chance you're not joking he means tensile. Ceramics are typically -10x stronger in compression than tension.
Hollow stainless screws shouldn't be too heavy. Maybe a six sided hole for driving in the back. Welding titanium needs a lot more perfect conditions, as in a pretty much pure Argon or He environment. (Not an expert by any definition disclaimer) A lot of extra trouble and expense to save a couple hundred pounds.Titanium is quite reactive in air in a way that SS simply isn't.
I know the material of the tile isn't that sturdy, but I'm sure it's stronger than tinsel.On the off chance you're not joking he means tensile. Ceramics are typically -10x stronger in compression than tension.Quote from: NomaddHollow stainless screws shouldn't be too heavy. Maybe a six sided hole for driving in the back. Welding titanium needs a lot more perfect conditions, as in a pretty much pure Argon or He environment. (Not an expert by any definition disclaimer) A lot of extra trouble and expense to save a couple hundred pounds.Titanium is quite reactive in air in a way that SS simply isn't.
Let's keep in mind all of the design constraints for these tiles to avoid "local optimums."
Protect against earth re-entry from LEO.
Protect against earth re-entry from GEO (or at least GTO)
Protect against earth re-entry from mars
All of the above should be possible multiple (TBD) times.
At some point installation has to be capable of automation, ideally fairly simple and high speed. Hand placement on 100s of SS's won't cut it.
Tiles should be fairly easy//quick to inspect. Ideally you should be able to look at them and say "Yes, those are all good. That one's marginal and those two need replacing now" while inside a pressure suit. :)
Has to be capable of repair while in a pressure suit (but could be straight swap out from a stock of spares rather than some clever single use repair foam like the shuttle)
It's that total combination that makes this design and development task so tough. :(
Which suggest (regardless of how they are implemented)
Tiles self align WRT to each other, possibly with some compliance in the mounts to accommodate slightly misaligned placement.
No hand cut/sized/installed gap fillers (like on shuttle)
Limited number of sizes and shapes. Complex areas are done using more smaller (but standard) tiles.
Eliminate any special case areas, otherwise you have to either a) Carry special repair materials for them or b) Assume they never fail. With enough vehicles flying over a long enough period (and they definitely will be if Musks goals are to be met) this is very wishful thinking. :(
The clamps that hold pin can be designed to be able released by applying the strong magnetic field. Just like security tags for clothes.
This way the tile can be removed for inspection or replacement with ease.
When installing a high rpm grinding wheel it is standard to give it a tap. If there is a hidden crack somewhere it will give a characteristic dead thump. This got me thinking.What you're talking about is usually called "Acoustic emission" monitoring. It's been proposed (used?) for COPV monitoring amongst other applications. That's when you listen for sounds. But if you excite the structure that's more like active ultrasound system.
The SS has every promise of being a boom box. There is the possibility that many if not all failure modes will have acoustic signatures that a pickup array could narrow down to a few tiles making detailed inspection much easier. An inspection tool, essentially an acoustic pickup and a pinger, would be placed on a tile to be checked. Lots of moving parts here and maybe not practical. If it can be made to work it both makes inspection easier and lends itself to automation.
Phil
Protect against earth re-entry from LEO.
Protect against earth re-entry from GEO (or at least GTO)
Protect against earth re-entry from mars
All of the above should be possible multiple (TBD) times.
At some point installation has to be capable of automation, ideally fairly simple and high speed. Hand placement on 100s of SS's won't cut it.
Tiles should be fairly easy//quick to inspect. Ideally you should be able to look at them and say "Yes, those are all good. That one's marginal and those two need replacing now" while inside a pressure suit. :)
Has to be capable of repair while in a pressure suit (but could be straight swap out from a stock of spares rather than some clever single use repair foam like the shuttle)
Of all Musks goals, fast turnaround, at least after interplanetary EDL, may be the least realistic. The heat shield has a rough job. If it needs TLC after a high energy EDL, that's part of the cost of doing business.Well yes and no.
Phil
I wasn't very precise on my wording but it looks like I got the idea across. By 'ping' I meant going active. The frequencies of interest and character of the signal (musician speak) will be very different, passive and active.When installing a high rpm grinding wheel it is standard to give it a tap. If there is a hidden crack somewhere it will give a characteristic dead thump. This got me thinking.What you're talking about is usually called "Acoustic emission" monitoring. It's been proposed (used?) for COPV monitoring amongst other applications. That's when you listen for sounds. But if you excite the structure that's more like active ultrasound system.
The SS has every promise of being a boom box. There is the possibility that many if not all failure modes will have acoustic signatures that a pickup array could narrow down to a few tiles making detailed inspection much easier. An inspection tool, essentially an acoustic pickup and a pinger, would be placed on a tile to be checked. Lots of moving parts here and maybe not practical. If it can be made to work it both makes inspection easier and lends itself to automation.
Phil
In effect you hear "pings" as the material cracks, or crystals slide over each other.
Note.
"Acoustic" in this context is not "sound" but a mechanical vibration wave. The signals can have a bandwidth of Mega Hertz rather than less than 20KHz.
The sound spectrum from a structure this big and the network of attached sensors ("Microphones doesn't really do them justice somehow) is going to be very complex. However if there are certain key features of a failure signature then something much simpler (like a filterbank) could serve well enough as a continuous failure detection system.
I wasn't very precise on my wording but it looks like I got the idea across. By 'ping' I meant going active. The frequencies of interest and character of the signal (musician speak) will be very different, passive and active.That's a tricky one.
On the passive side I figure a combination of band pass filter and DSP. It'll be a noisy (vibration rich) environment. Hard to pick out signal from noise. I wonder if SX is already building a vibration database during testing. Something like what is done with sonar. I'd be very surprised if they weren't doing this at least on the engines.
Hand installation is fine, as long as it quick per tile. If 2 or 3 guys in a lift can install 2 tiles per minute, then 2 crews working 3 shifts can tile a whole Starship in 2 days. That's only 150-200 man-hours. For 100 ships a year, that's probably not worth automating.You might like to re-consider that.
Inspection and repair is a whole different question, but they need to get it flying first so I highly doubt they are spending too much time optimizing inspection techniques. Worst case, they break off all the tiles and install all new ones, which should only take a couple days. Better case, they are able to visually identify problematic tiles, which could eventually be automated with a high res photographic scanning system.
Hand installation is fine, as long as it quick per tile. If 2 or 3 guys in a lift can install 2 tiles per minute, then 2 crews working 3 shifts can tile a whole Starship in 2 days. That's only 150-200 man-hours. For 100 ships a year, that's probably not worth automating.
I wasn't very precise on my wording but it looks like I got the idea across. By 'ping' I meant going active. The frequencies of interest and character of the signal (musician speak) will be very different, passive and active.That's a tricky one.
On the passive side I figure a combination of band pass filter and DSP. It'll be a noisy (vibration rich) environment. Hard to pick out signal from noise. I wonder if SX is already building a vibration database during testing. Something like what is done with sonar. I'd be very surprised if they weren't doing this at least on the engines.
Modern storage is so large and cheap it's possible to record a staggering amount of data. So you can store more or less as much data as you want (the usual issue is resolution. 8 bits at 2MHz. Piece of cake. 16bits at 2MHz. Much tougher)
But right now SS (even its engines) is a moving development target.
So what part(s) of that spectrum is down to the TPS operating normally? What part is due to a tile failure? What part to the rest of the system?
It's unclear how much of that data will be usable as raw material for diagnostic purposes.
But it's probably cheaper to collect it and not use it than vice versa.
Could they embed a loop of wire inside the tile when it was made? Any cracks might then break the wire loop which could then be detected by magnetic induction.
Surface damage can be checked visually. Maybe a drone on mars.Could they embed a loop of wire inside the tile when it was made? Any cracks might then break the wire loop which could then be detected by magnetic induction.
Neat idea. Now factor in
Will it detect surface damage, or will it be so deep for thermal protection it survives even when the surface is too compromised to survive?
What does the metal properties interacting to the tile material do to them?
Most very high temp metals are also very dense. How much extra mass would this add?
It's actually a very neat idea. No electronics. No batteries. But because of the extreme range of environments involved everything becomes a factor that has to be tested for interaction with everything else. :(
Surface damage can be checked visually. Maybe a drone on mars.
I'm not quite getting the idea. Would there be an induction coil under each tile? Would the whole SS body carry an AC signal? That sounds interesting. Can two AC signals be injected and phase shifted to act like a phased array to pinpoint the failure?
Yes similar to the sort of thing you get in a library where each book that gets scanned out and scanned back in again. Although obviously with different materials.Surface damage can be checked visually. Maybe a drone on mars.
I'm not quite getting the idea. Would there be an induction coil under each tile? Would the whole SS body carry an AC signal? That sounds interesting. Can two AC signals be injected and phase shifted to act like a phased array to pinpoint the failure?
I read it as a loop of wire in the tile (not necessarily circular). An induction coil on some kind of carrier is passed over each tile and the assumption is that most damage processes would involve breaking the coil, so no signal. In principle that head could also carry a camera to check for visual damage which might not snap the wire.
But I could be wrong.
Surface damage can be checked visually. Maybe a drone on mars.
I'm not quite getting the idea. Would there be an induction coil under each tile? Would the whole SS body carry an AC signal? That sounds interesting. Can two AC signals be injected and phase shifted to act like a phased array to pinpoint the failure?
I read it as a loop of wire in the tile (not necessarily circular). An induction coil on some kind of carrier is passed over each tile and the assumption is that most damage processes would involve breaking the coil, so no signal. In principle that head could also carry a camera to check for visual damage which might not snap the wire.
Could they embed a loop of wire inside the tile when it was made? Any cracks might then break the wire loop which could then be detected by magnetic induction.
Neat idea. Now factor in
Will it detect surface damage, or will it be so deep for thermal protection it survives even when the surface is too compromised to survive?
What does the metal properties interacting to the tile material do to them?
Most very high temp metals are also very dense. How much extra mass would this add?
It's actually a very neat idea. No electronics. No batteries. But because of the extreme range of environments involved everything becomes a factor that has to be tested for interaction with everything else. :(
Could they embed a loop of wire inside the tile when it was made? Any cracks might then break the wire loop which could then be detected by magnetic induction.
Neat idea. Now factor in
Will it detect surface damage, or will it be so deep for thermal protection it survives even when the surface is too compromised to survive?
What does the metal properties interacting to the tile material do to them?
Most very high temp metals are also very dense. How much extra mass would this add?
It's actually a very neat idea. No electronics. No batteries. But because of the extreme range of environments involved everything becomes a factor that has to be tested for interaction with everything else. :(
My feeling is that the wire would survive many situations where the tile would not, making it useless as an indicator. The wire would simply be stronger than the tile, and, even assuming a crack shifts enough to put force on the wire, the tile around the wire would crumble as the wire flexes to accept the load without breaking. Think about the way rebar in concrete survives long after the concrete itself begins to crack and crumble.
A worse problem is that the weaknesses in tiles that are most worrying are hairline cracks, nearly invisible to the eye. Such a crack would be unlikely to break the wire, since neither side actually moved.
How about using optical fibers instead of wire?
You could update this idea for the digital age. Put an RFID chip and and antenna loop in each tile, just like in a credit card. Then each tile has a separate unique ID and you can interrogate a bunch of them in parallel. You'd need to keep the loop some minimum distance away from the steel hull, of course.That was developed for the Shuttle programme in the early 90's.
How about using optical fibers instead of wire?Also possible. Alumina (basically sapphire without metal ions to color it) FO is available and is good to somewhere around 1500-2000c
The same issue exists with wires and with optical fibers - the connectors. If each tile has a connector, that weight not only adds up, but connectors are points of failure.OP was the the design is passive, read by a moving read with an induction coil. Break in wire -->> no signal.
Optical fibres won't allow an electrical current to be induced so wouldn't workCould they embed a loop of wire inside the tile when it was made? Any cracks might then break the wire loop which could then be detected by magnetic induction.
Neat idea. Now factor in
Will it detect surface damage, or will it be so deep for thermal protection it survives even when the surface is too compromised to survive?
What does the metal properties interacting to the tile material do to them?
Most very high temp metals are also very dense. How much extra mass would this add?
It's actually a very neat idea. No electronics. No batteries. But because of the extreme range of environments involved everything becomes a factor that has to be tested for interaction with everything else. :(
My feeling is that the wire would survive many situations where the tile would not, making it useless as an indicator. The wire would simply be stronger than the tile, and, even assuming a crack shifts enough to put force on the wire, the tile around the wire would crumble as the wire flexes to accept the load without breaking. Think about the way rebar in concrete survives long after the concrete itself begins to crack and crumble.
A worse problem is that the weaknesses in tiles that are most worrying are hairline cracks, nearly invisible to the eye. Such a crack would be unlikely to break the wire, since neither side actually moved.
How about using optical fibers instead of wire?
I believe there to be some confusion about the original proposal here, particularly on your part, Coastal Ron. The tiles are not connected. They are passive, they do no active reporting. If the wire is intact, an external robot can pass over it and get an inductive response. If the wire is broken, the external robot will get a different inductive response. This happens on the ground in post-flight checkout, or I guess one could do it in orbit.How about using optical fibers instead of wire?
The same issue exists with wires and with optical fibers - the connectors. If each tile has a connector, that weight not only adds up, but connectors are points of failure.
OK, now you have collected the signals from one tile, but there are thousands of them. Do you run individual wire or optical cables for each of those into one central monitor, or do you group them into local collection boxes that then have to run wires up to the central monitor? And if you group them, where are those local connection boxes at, and how are they protected?
This is a lot of technology to put on the side of the Starship that will be experiencing extremely high temperatures.
So I'm thinking they won't put sensors on the tiles.
I don't know if this is useful or not:I believe there to be some confusion about the original proposal here, particularly on your part, Coastal Ron. The tiles are not connected. They are passive, they do no active reporting. If the wire is intact, an external robot can pass over it and get an inductive response. If the wire is broken, the external robot will get a different inductive response. This happens on the ground in post-flight checkout, or I guess one could do it in orbit.How about using optical fibers instead of wire?
The same issue exists with wires and with optical fibers - the connectors. If each tile has a connector, that weight not only adds up, but connectors are points of failure.
OK, now you have collected the signals from one tile, but there are thousands of them. Do you run individual wire or optical cables for each of those into one central monitor, or do you group them into local collection boxes that then have to run wires up to the central monitor? And if you group them, where are those local connection boxes at, and how are they protected?
This is a lot of technology to put on the side of the Starship that will be experiencing extremely high temperatures.
So I'm thinking they won't put sensors on the tiles.
Ahh, thank you. Rube Goldberg was taking over. However it's done it has to be cheap and simple.I believe there to be some confusion about the original proposal here, particularly on your part, Coastal Ron. The tiles are not connected. They are passive, they do no active reporting. If the wire is intact, an external robot can pass over it and get an inductive response. If the wire is broken, the external robot will get a different inductive response. This happens on the ground in post-flight checkout, or I guess one could do it in orbit.How about using optical fibers instead of wire?
The same issue exists with wires and with optical fibers - the connectors. If each tile has a connector, that weight not only adds up, but connectors are points of failure.
OK, now you have collected the signals from one tile, but there are thousands of them. Do you run individual wire or optical cables for each of those into one central monitor, or do you group them into local collection boxes that then have to run wires up to the central monitor? And if you group them, where are those local connection boxes at, and how are they protected?
This is a lot of technology to put on the side of the Starship that will be experiencing extremely high temperatures.
So I'm thinking they won't put sensors on the tiles.
Ahh, thank you. Rube Goldberg was taking over. However it's done it has to be cheap and simple.I believe there to be some confusion about the original proposal here, particularly on your part, Coastal Ron. The tiles are not connected. They are passive, they do no active reporting. If the wire is intact, an external robot can pass over it and get an inductive response. If the wire is broken, the external robot will get a different inductive response. This happens on the ground in post-flight checkout, or I guess one could do it in orbit.How about using optical fibers instead of wire?
The same issue exists with wires and with optical fibers - the connectors. If each tile has a connector, that weight not only adds up, but connectors are points of failure.
OK, now you have collected the signals from one tile, but there are thousands of them. Do you run individual wire or optical cables for each of those into one central monitor, or do you group them into local collection boxes that then have to run wires up to the central monitor? And if you group them, where are those local connection boxes at, and how are they protected?
This is a lot of technology to put on the side of the Starship that will be experiencing extremely high temperatures.
So I'm thinking they won't put sensors on the tiles.
Gettin complex again. The original proposal was a simple loop of wire embedded in the tile. Nothing more. An inspection device with an active induction coil would pass over the tiles. A tile with an intact loop will experience an induced current flow and create a corresponding magnetic field. A tile with a broken loop will not. A magnetic field, or the lack, will tell the state of the tile.Ahh, thank you. Rube Goldberg was taking over. However it's done it has to be cheap and simple.I believe there to be some confusion about the original proposal here, particularly on your part, Coastal Ron. The tiles are not connected. They are passive, they do no active reporting. If the wire is intact, an external robot can pass over it and get an inductive response. If the wire is broken, the external robot will get a different inductive response. This happens on the ground in post-flight checkout, or I guess one could do it in orbit.How about using optical fibers instead of wire?
The same issue exists with wires and with optical fibers - the connectors. If each tile has a connector, that weight not only adds up, but connectors are points of failure.
OK, now you have collected the signals from one tile, but there are thousands of them. Do you run individual wire or optical cables for each of those into one central monitor, or do you group them into local collection boxes that then have to run wires up to the central monitor? And if you group them, where are those local connection boxes at, and how are they protected?
This is a lot of technology to put on the side of the Starship that will be experiencing extremely high temperatures.
So I'm thinking they won't put sensors on the tiles.
Basically, the proposal is to embed the equivalent of a passive rfid tag in each tile designed so that if the tile breaks the rfid circuit is broken right?
Gettin complex again. The original proposal was a simple loop of wire embedded in the tile. Nothing more. An inspection device with an active induction coil would pass over the tiles. A tile with an intact loop will experience an induced current flow and create a corresponding magnetic field. A tile with a broken loop will not. A magnetic field, or the lack, will tell the state of the tile.
TBD: will all non visible tile failures consistently break the wire?
If this works it's elegant. And simple.
Phil
Healthcare and automotive industries have OTC "high-temp" RFID chips that are good into the 300-400 C range. My earlier thought was that if you took the OPs original idea of the metal strands through the tile for break detection and formed those strands into an antenna shape connected to an embedded RFID chip you'd then be able to use cheap over the counter RFID scanning gear to rapidly scan the entire shield.One informed opinion (livingjw) is that max acceptable skin temp is 600C. That would make a chip that fails at 400C a problem.
Working tiles would self identify and tiles with broken antennas won't answer.
Edit: With the OP I was left with the impression that because you're just looking at continuity within the tile you'd need to scan each tile individually. The RFID addition was to allow scanning large numbers of tiles simultaneously and know which specific tiles didn't answer.
Healthcare and automotive industries have OTC "high-temp" RFID chips that are good into the 300-400 C range. My earlier thought was that if you took the OPs original idea of the metal strands through the tile for break detection and formed those strands into an antenna shape connected to an embedded RFID chip you'd then be able to use cheap over the counter RFID scanning gear to rapidly scan the entire shield.One informed opinion (livingjw) is that max acceptable skin temp is 600C. That would make a chip that fails at 400C a problem.
Working tiles would self identify and tiles with broken antennas won't answer.
Edit: With the OP I was left with the impression that because you're just looking at continuity within the tile you'd need to scan each tile individually. The RFID addition was to allow scanning large numbers of tiles simultaneously and know which specific tiles didn't answer.
Theoretically the RFID could be stimulated and read from a distance but unless there is some mongo RF pumping out, even with a bit of an antenna and a half wave standoff from the skin, this will have some limitations. There needs to be a visual check anyhow so it seems simpler to just do both at the same time and go with a simple loop.
Despite defending the wire loop idea I think acoustic deserves some investigation.
Phil
Healthcare and automotive industries have OTC "high-temp" RFID chips that are good into the 300-400 C range. My earlier thought was that if you took the OPs original idea of the metal strands through the tile for break detection and formed those strands into an antenna shape connected to an embedded RFID chip you'd then be able to use cheap over the counter RFID scanning gear to rapidly scan the entire shield.One informed opinion (livingjw) is that max acceptable skin temp is 600C. That would make a chip that fails at 400C a problem.
Working tiles would self identify and tiles with broken antennas won't answer.
Edit: With the OP I was left with the impression that because you're just looking at continuity within the tile you'd need to scan each tile individually. The RFID addition was to allow scanning large numbers of tiles simultaneously and know which specific tiles didn't answer.
Theoretically the RFID could be stimulated and read from a distance but unless there is some mongo RF pumping out, even with a bit of an antenna and a half wave standoff from the skin, this will have some limitations. There needs to be a visual check anyhow so it seems simpler to just do both at the same time and go with a simple loop.
Despite defending the wire loop idea I think acoustic deserves some investigation.
Phil
Generally I am a bit skeptic about drone over usage (for every possible usage, even when more practical solutions are available), but inspection of tiles seems like a good task for drones. The required cameras, RFID or the suggested RF devices shall be well within the lift capacity, and in outdoor environment (possibly with reference GPS stations to differential measurements) positioning should not be a problem. (not sure about ultrasound however).
Replacement and repairs will need a scaffolding/cherry pickers anyhow. But a quick inspection can be done without that. And the platform (as a drone, positioning and guidance) can be COTS solution with marginal cost.
I wasn't sure about the backside tile temperatures and 600C would be an issue. Agree the idea is probably played out but one last thought before I retreat ;) If the RFID readers were strategically positioned inside the Starship it would allow you to check the heat shield status dynamically on orbit and before you start your entry. Knowing you'd taken no mmod damage after a 6 month journey and before landing would have some upsides. Reading RFID through metal comes with additional challenges and specialized requirements so agree the idea is probably exhausted.Boom Boom :) Very good.
Edit: This would also allow the captain to say "Status report on shields!". "Shields are at 100% sir." That makes it worth it right?
Think an acoustic scanner producing sonograms with advanced signal processing software. Intact tiles have one signature. Tiles with cracks or detached produce a variety of anomalous signatures. An analog (physical world) process that produces a digital signature capable of highly automated software processing and analysis.
Were I Elon, I'd assign the breadboard for this to interns.
But I am not familiar with this tech. Does it require mechanical proximity/attachments (like the emitter/microphone pushed against the tiles)? Or it is doable from a small distance (like several cm or something)? If former, that may define some procedural constraints, countering the advantages.It's usually done with contact transducers but can be done with non -contact methods. The higher the range the higher the power needed.
Can you do this on Mars after landing?
Agreed. But if there is any significant damage to the heat shield when they need to leave Mars can the ship return to Earth using repeated aerocapture at lower temperature as an emergency measure? If it can then that might be a better fall back rather than attempt to repair on Mars.Can you do this on Mars after landing?
Each method except RF readed from a distance (RFID) seems problematic on Mars, not enough air pressure for drones, or for sound propagation, no huge fixed structures to move inspection heads. Same for the Moon or in orbit inspections.
If they want to move any kind of inspection head along the surface, they will need a huge Canadarm or some kind of climbing robot for that. The climbing robot is very Sci-Fi, but far from a readily available solution, so less likely in my opinion.
Keep in mind that unlike Shuttle you only need to check half of the structure, which I think makes the task a bit easier (not easy, easier). They were looking at a frame the shuttle would pass through, but it's shape made that quite complex. The sensor head could be quite light, no more than a few kilos, and SS has been getting shorter (I thought it was about 80m but IIRC it's now nearer 60m long).Can you do this on Mars after landing?
Each method except RF readed from a distance (RFID) seems problematic on Mars, not enough air pressure for drones, or for sound propagation, no huge fixed structures to move inspection heads. Same for the Moon or in orbit inspections.
If they want to move any kind of inspection head along the surface, they will need a huge Canadarm or some kind of climbing robot for that. The climbing robot is very Sci-Fi, but far from a readily available solution, so less likely in my opinion.
Agreed. But if there is any significant damage to the heat shield when they need to leave Mars can the ship return to Earth using repeated aerocapture at lower temperature as an emergency measure? If it can then that might be a better fall back rather than attempt to repair on Mars.I think you're confused.
Can you do this on Mars after landing?
Each method except RF readed from a distance (RFID) seems problematic on Mars, not enough air pressure for drones, or for sound propagation, no huge fixed structures to move inspection heads. Same for the Moon or in orbit inspections.
If they want to move any kind of inspection head along the surface, they will need a huge Canadarm or some kind of climbing robot for that. The climbing robot is very Sci-Fi, but far from a readily available solution, so less likely in my opinion.
Keep in mind that unlike Shuttle you only need to check half of the structure, which I think makes the task a bit easier (not easy, easier). They were looking at a frame the shuttle would pass through, but it's shape made that quite complex. The sensor head could be quite light, no more than a few kilos, and SS has been getting shorter (I thought it was about 80m but IIRC it's now nearer 60m long).Can you do this on Mars after landing?
Each method except RF readed from a distance (RFID) seems problematic on Mars, not enough air pressure for drones, or for sound propagation, no huge fixed structures to move inspection heads. Same for the Moon or in orbit inspections.
If they want to move any kind of inspection head along the surface, they will need a huge Canadarm or some kind of climbing robot for that. The climbing robot is very Sci-Fi, but far from a readily available solution, so less likely in my opinion.
However once you factor in a mars post-landing inspection they you'd like to do it from the inside. Steel make magnetic field and RF sensors awkward (not impossible just more difficult) but something based on sound seems relatively viable.
A good point to consider is what are you going to do if you find tile damage after you're on mars?
Making the TPS out of a small number of different size (and thickness) tiles could mean you could get by with a small spares inventory (possibly with some on site machining).
Keep in mind the shuttle repair foam was never actually tested to survive from orbit. :(
On Mars consider an external acoustic test transducer where a long crane arm lifts and moves the transducer array touching (minimal atmosphere, or maybe not?) each tile or tile array to obtain a return signal for digital signal processing analysis. A long crane arm lifting a not heavy transducer is relatively easy. If not an automated move & scan, move & scan, a video feed allows a Mars resident to move it around. My guess is NOT automated. The human is there. Automation is engineering development time & resource intensive and fails fragile with unknown unknowns.
The harder part is replacing the tile. Maybe a human in a bucket lifted by a crane.
Crane stuff is a bit easier on Mars with ~38% gravity and sundry crane capability is needed for other applications.
On Mars consider an external acoustic test transducer where a long crane arm lifts and moves the transducer array touching (minimal atmosphere, or maybe not?) each tile or tile array to obtain a return signal for digital signal processing analysis. A long crane arm lifting a not heavy transducer is relatively easy. If not an automated move & scan, move & scan, a video feed allows a Mars resident to move it around. My guess is NOT automated. The human is there. Automation is engineering development time & resource intensive and fails fragile with unknown unknowns.
The harder part is replacing the tile. Maybe a human in a bucket lifted by a crane.
Crane stuff is a bit easier on Mars with ~38% gravity and sundry crane capability is needed for other applications.
Replace in orbit. Easier to get around.
Agreed. But if there is any significant damage to the heat shield when they need to leave Mars can the ship return to Earth using repeated aerocapture at lower temperature as an emergency measure? If it can then that might be a better fall back rather than attempt to repair on Mars.Can you do this on Mars after landing?
Each method except RF readed from a distance (RFID) seems problematic on Mars, not enough air pressure for drones, or for sound propagation, no huge fixed structures to move inspection heads. Same for the Moon or in orbit inspections.
If they want to move any kind of inspection head along the surface, they will need a huge Canadarm or some kind of climbing robot for that. The climbing robot is very Sci-Fi, but far from a readily available solution, so less likely in my opinion.
Lots of interesting ideas here for how to inspect/test/repair TPS. I suspect most of then are probably unworkable, but that's OK, real gold comes from the Crazy Ideas Division, but only if there are enough crazy ideas!On Mars consider an external acoustic test transducer where a long crane arm lifts and moves the transducer array touching (minimal atmosphere, or maybe not?) each tile or tile array to obtain a return signal for digital signal processing analysis. A long crane arm lifting a not heavy transducer is relatively easy. If not an automated move & scan, move & scan, a video feed allows a Mars resident to move it around. My guess is NOT automated. The human is there. Automation is engineering development time & resource intensive and fails fragile with unknown unknowns.
The harder part is replacing the tile. Maybe a human in a bucket lifted by a crane.
Crane stuff is a bit easier on Mars with ~38% gravity and sundry crane capability is needed for other applications.
Replace in orbit. Easier to get around.
Yep. Especially that more damage could happen on ascent. And still more on the way.
I'd guess the best time for inspection+repair EVA would be some couple of weeks before re-entry
Think an acoustic scanner producing sonograms with advanced signal processing software. Intact tiles have one signature. Tiles with cracks or detached produce a variety of anomalous signatures. An analog (physical world) process that produces a digital signature capable of highly automated software processing and analysis.When I introduced the idea of acoustic, it was intended to be a two step process with passive pickups inside the hull for rough localization and an active second pass of whatever process, to identify the specific tile.
Were I Elon, I'd assign the breadboard for this to interns.
A canada arm would be a narrow use expensive solution that as currently built can not operate in 1g. Operation in .38g - unknown to me. If it were not for the external mounting points it would be a good solution for pre EDL inspection. IMO opinion a small free flyer would be better if inspection can be done without contact.Can you do this on Mars after landing?
Each method except RF readed from a distance (RFID) seems problematic on Mars, not enough air pressure for drones, or for sound propagation, no huge fixed structures to move inspection heads. Same for the Moon or in orbit inspections.
If they want to move any kind of inspection head along the surface, they will need a huge Canadarm or some kind of climbing robot for that. The climbing robot is very Sci-Fi, but far from a readily available solution, so less likely in my opinion.
In the parlance of 1960's US Army aviation, a missing tile would be a red X. Not flight worthy. A field repair (hopefully already tested and known to work) would be a circled red X. One time flight only. Field repair could be an array of small tiles, thermal caulking or ablative marshmallows. It only has to work for that one flight needed to get to a proper maintenance facility.Keep in mind that unlike Shuttle you only need to check half of the structure, which I think makes the task a bit easier (not easy, easier). They were looking at a frame the shuttle would pass through, but it's shape made that quite complex. The sensor head could be quite light, no more than a few kilos, and SS has been getting shorter (I thought it was about 80m but IIRC it's now nearer 60m long).Can you do this on Mars after landing?
Each method except RF readed from a distance (RFID) seems problematic on Mars, not enough air pressure for drones, or for sound propagation, no huge fixed structures to move inspection heads. Same for the Moon or in orbit inspections.
If they want to move any kind of inspection head along the surface, they will need a huge Canadarm or some kind of climbing robot for that. The climbing robot is very Sci-Fi, but far from a readily available solution, so less likely in my opinion.
However once you factor in a mars post-landing inspection they you'd like to do it from the inside. Steel make magnetic field and RF sensors awkward (not impossible just more difficult) but something based on sound seems relatively viable.
A good point to consider is what are you going to do if you find tile damage after you're on mars?
Making the TPS out of a small number of different size (and thickness) tiles could mean you could get by with a small spares inventory (possibly with some on site machining).
Keep in mind the shuttle repair foam was never actually tested to survive from orbit. :(
Lots of interesting ideas here for how to inspect/test/repair TPS. I suspect most of then are probably unworkable, but that's OK, real gold comes from the Crazy Ideas Division, but only if there are enough crazy ideas!The 3 key things people should take away from this discussion are
Anyway, given the structure of likely TPS tiles, how likely is it really that we'll have hidden failure modes? This is a legitimate question on my part (I'm not just making a rhetorical point ... I'm in no way well informed about the ins and outs of TPS). ISTM that provided the attachment system is well designed (after they fly these things a few time they're going to have to strip the tiles and see how the attachments are doing), any trauma that would compromise a tile should leave a visible crack or crater. I would think this would actually be a desirable design goal. This would then reduce testing to a matter of optical inspection ... some combination of eyeballs (via HD video), machine vision, laser scanners, etc. Ideally this could all go on a smallish free flyer that would be deployed to scan the TPS a couple weeks before re-entry.Yes. The ideal design would visibly change in a way that says "I can handle one more earth entry, but after that replace me." I hope such a design is possible, but honestly have no idea. I keep thinking "Ok so there's a different color sub-surface layer that shows through if it's damaged, but won't that be hidden by the surface discoloration on entry?"
As for actual repair, there's been a lot of talk about what shape tiles, how many types of spares, can they be fabbed locally, etc. but ISTM that it may be more practical to develop an emergency ablative patch material (sort of like what they had, but apparently never tested, for the shuttle ... definitely want to test it though!).Shuttle when with repair foam because NAA built a vehicle where nearly every single one of the 24 000 odd tiles (IIRC) was unique. Covering a surface with a limited number of different tile types (both in size, shape and thickness) means you can replace a part with a tested part. While a foam can accommodate any shape (as long as it's not too big) it's all down to the care and precision that it's applied and how closely the setting conditions match the nominal conditions the foam was tested in.
Anybody have a WAG as to whether:I'm not sure if this even rises to the level of a WAG. Just running the
A tile on the centerline of windward which should be the hottest short of the fins
Is missing and would:
Burn through on reentry. Probably around melting of 1400C
Get so hot that the steel would be annealed and need replacement. Less than melting but more than 600C.
Not even get to the heat damage limit of 600C. This could happen because hot gases flow around single missing tile.
A hidden failure mode would be a hairline crack. That might have no impact or be total disaster. I doubt Elon even knows but I expect he intends to have some engineers looking at all failure modes.Lots of interesting ideas here for how to inspect/test/repair TPS. I suspect most of then are probably unworkable, but that's OK, real gold comes from the Crazy Ideas Division, but only if there are enough crazy ideas!On Mars consider an external acoustic test transducer where a long crane arm lifts and moves the transducer array touching (minimal atmosphere, or maybe not?) each tile or tile array to obtain a return signal for digital signal processing analysis. A long crane arm lifting a not heavy transducer is relatively easy. If not an automated move & scan, move & scan, a video feed allows a Mars resident to move it around. My guess is NOT automated. The human is there. Automation is engineering development time & resource intensive and fails fragile with unknown unknowns.
The harder part is replacing the tile. Maybe a human in a bucket lifted by a crane.
Crane stuff is a bit easier on Mars with ~38% gravity and sundry crane capability is needed for other applications.
Replace in orbit. Easier to get around.
Yep. Especially that more damage could happen on ascent. And still more on the way.
I'd guess the best time for inspection+repair EVA would be some couple of weeks before re-entry
Anyway, given the structure of likely TPS tiles, how likely is it really that we'll have hidden failure modes? This is a legitimate question on my part (I'm not just making a rhetorical point ... I'm in no way well informed about the ins and outs of TPS). ISTM that provided the attachment system is well designed (after they fly these things a few time they're going to have to strip the tiles and see how the attachments are doing), any trauma that would compromise a tile should leave a visible crack or crater. I would think this would actually be a desirable design goal. This would then reduce testing to a matter of optical inspection ... some combination of eyeballs (via HD video), machine vision, laser scanners, etc. Ideally this could all go on a smallish free flyer that would be deployed to scan the TPS a couple weeks before re-entry.
As for actual repair, there's been a lot of talk about what shape tiles, how many types of spares, can they be fabbed locally, etc. but ISTM that it may be more practical to develop an emergency ablative patch material (sort of like what they had, but apparently never tested, for the shuttle ... definitely want to test it though!). Leave tile replacement for Earth depot maintenance. Eventually we'll have the deep-space infrastructure for off-world heat shield work, but for the first decade (at least) of Starships to Mars, it would be much simpler to just leave Mars with minor TPS damage and patch (with a well tested ablative patch material) before Earth arrival. I'm really having a hard time imagining a practical system for doing TPS repair, even temporary patch work, on another planetary surface without a fair bit of infrastructure development happening first.
Edit: minor tyops
Anybody have a WAG as to whether:I'm not sure if this even rises to the level of a WAG. Just running the
A tile on the centerline of windward which should be the hottest short of the fins
Is missing and would:
Burn through on reentry. Probably around melting of 1400C
Get so hot that the steel would be annealed and need replacement. Less than melting but more than 600C.
Not even get to the heat damage limit of 600C. This could happen because hot gases flow around single missing tile.cartoonsimulation through my mind. IIRC 1400C is about the temp expected on the centerline. Most of this is heat from hypersonic shock compression with some radiative thrown in to keep it interesting.
Which a tile missing the I can think of nothing that would mitigate radiative impact. The raw skin would literally take the heat. Its not impossible that there might be an edge condition that would keep the shock compression from immediately entering the cavity. The operant word is 'immediately'. Closer to the center of the cavity the edge condition, whatever it is, will diminish until it just isn't there anymore and again, the skin is taking the heat. The rate of edge effect diminution would be impacted by tile thickness. In the hypersonic regime I'd expect it to be gone less than one tile thickness into the cavity.
So, after sober consideration and a bit of hot air, loose a centerline tile, loose the mission. It'll burn through.
Phil
What is the effective difference between a crack in a tile and the small space between adjacent tiles? How close together can they be?Because if the space between tiles is normally occupied with a filler to prevent inter-tile contact, then some types of cracks could be repaired in place rather than replaced. In this case the crack did not cause the tile to be dislodged, but is held in place by one or more pegs on each side of the crack.
When I introduced the idea of acoustic, it was intended to be a two step process with passive pickups inside the hull for rough localization and an active second pass of whatever process, to identify the specific tile.
The SS is going to be a big reverberating structure and I expect it to carry sound quite well. If a tile cracks it will give out a uniquely "tile like" sound. To give an example, I recently saw a water tumbler that looked as if it could have been glass or plastic. One tap with a fingernail and I knew it was plastic. Hard materials seem to have a characteristic sound signature independent of size or shape.
This would probably not need any very high frequency gymnastics. Most of the signature will probably be under 40khz (guess) but this would need some exploration. DSP to pull signal out of the background noise.
The fins can each have their own pickup array. Unless cryo rated pickup are used the tanks could be difficult. Bottom and top dome would be the closest the sensors could be to the middle. As 'boomy' as the SS is, I doubt it would be difficult to pick out a small array of tiles as the source of a signature.
Of course this is all speculation but it offers the potential for an inexpensive and easy to implement first line of defense. As a bonus, preliminary research looks to be inexpensive.
Phil
Much of that is over my head. While reading I was nodding my head and going ok, ok, and working towards a learning moment (for which I thank you). I do have a couple quibbles on what I did immediately understand.Anybody have a WAG as to whether:I'm not sure if this even rises to the level of a WAG. Just running the
A tile on the centerline of windward which should be the hottest short of the fins
Is missing and would:
Burn through on reentry. Probably around melting of 1400C
Get so hot that the steel would be annealed and need replacement. Less than melting but more than 600C.
Not even get to the heat damage limit of 600C. This could happen because hot gases flow around single missing tile.cartoonsimulation through my mind. IIRC 1400C is about the temp expected on the centerline. Most of this is heat from hypersonic shock compression with some radiative thrown in to keep it interesting.
Which a tile missing the I can think of nothing that would mitigate radiative impact. The raw skin would literally take the heat. Its not impossible that there might be an edge condition that would keep the shock compression from immediately entering the cavity. The operant word is 'immediately'. Closer to the center of the cavity the edge condition, whatever it is, will diminish until it just isn't there anymore and again, the skin is taking the heat. The rate of edge effect diminution would be impacted by tile thickness. In the hypersonic regime I'd expect it to be gone less than one tile thickness into the cavity.
So, after sober consideration and a bit of hot air, loose a centerline tile, loose the mission. It'll burn through.
Phil
Heat transfer isn't that simple. The skin temp would rise from the equilibrium temp with the tile towards the equilibrium temp without it. However, that equilibrium temperature will likely not be the same as the stagnation temp of the gas flow.
For example, as the temperature of the skin approaches 1100 C, it will dump about 100 kW/m^2 via radiation to the cooler back walls of the tank. This goes up to 300 kW/m^2 at 1400 C. T^4 is your friend. The Shuttle TPS centerline flux peaked around 100 kW/m^2, so if the lost tile is over a tank or engine section, burn-through seems unlikely.
On the crew area, there will be insulation backing the skin, so that the crew compartment interior walls don't tend toward the 500+ degree skin temp. This is probably bad news for the skin, since it won't be able to dump heat radiatively to the interior. But that insulation might be able to handle the heat flux for long enough for the vehicle to finish reentry.
MMOD is a danger at all times and should be acoustically detectable. There are many open questions and the answers will determine feasibility. It may not be viable but shouldn't take a lot of effort to explore.
When I introduced the idea of acoustic, it was intended to be a two step process with passive pickups inside the hull for rough localization and an active second pass of whatever process, to identify the specific tile.
The SS is going to be a big reverberating structure and I expect it to carry sound quite well. If a tile cracks it will give out a uniquely "tile like" sound. To give an example, I recently saw a water tumbler that looked as if it could have been glass or plastic. One tap with a fingernail and I knew it was plastic. Hard materials seem to have a characteristic sound signature independent of size or shape.
This would probably not need any very high frequency gymnastics. Most of the signature will probably be under 40khz (guess) but this would need some exploration. DSP to pull signal out of the background noise.
The fins can each have their own pickup array. Unless cryo rated pickup are used the tanks could be difficult. Bottom and top dome would be the closest the sensors could be to the middle. As 'boomy' as the SS is, I doubt it would be difficult to pick out a small array of tiles as the source of a signature.
Of course this is all speculation but it offers the potential for an inexpensive and easy to implement first line of defense. As a bonus, preliminary research looks to be inexpensive.
Phil
This pickup system sounds like something that "cost nothing" and "can help" so definitely worth to implement. But I don not think that It can reach a fidelity level required to be used as a single method to restrict deeper scanning to specific areas. I mean, If it works, it can signal/pickup some tile failures, but I doubt that is good enough to detect all possible anomalies.
I interpret your idea as the passive checks should be done continuously, waiting for tiles to crack. No active pinging (like a man with hammer, knocking along the heatshield).
In this case the problem is the timing. The pickup system presumably will detect the cracking tiles in the coast phase/in orbit (if the crew does not party too loud at that time), if a spontaneous crack in coast phase ever happen. Those events are separated, one at a time, and no obvious external noise at that phase.
But I think tiles will fail more likely during the ascent/descent, maybe in groups (multiple at a time), in an environment where plenty of sound and resonance apply. And filtering out a tile cracking sound of the noise of reentry does not sounds that easy (needs quite big dynamic range).
PS: actually the man with hammer could work, just make no sense (if there is a hammer why not a more sophisticated inspection device).
Heat transfer isn't that simple. The skin temp would rise from the equilibrium temp with the tile towards the equilibrium temp without it. However, that equilibrium temperature will likely not be the same as the stagnation temp of the gas flow.Much of that is over my head. While reading I was nodding my head and going ok, ok, and working towards a learning moment (for which I thank you). I do have a couple quibbles on what I did immediately understand.
For example, as the temperature of the skin approaches 1100 C, it will dump about 100 kW/m^2 via radiation to the cooler back walls of the tank. This goes up to 300 kW/m^2 at 1400 C. T^4 is your friend. The Shuttle TPS centerline flux peaked around 100 kW/m^2, so if the lost tile is over a tank or engine section, burn-through seems unlikely.
On the crew area, there will be insulation backing the skin, so that the crew compartment interior walls don't tend toward the 500+ degree skin temp. This is probably bad news for the skin, since it won't be able to dump heat radiatively to the interior. But that insulation might be able to handle the heat flux for long enough for the vehicle to finish reentry.
Shuttle EDL temps inform for a LEO reentry but would be an underestimate of higher energy reentries. SS coming from afar will do at least one skip so maybe this is a non-issue.
Maybe more important, "might be able to handle the heat flux" is fine for an armchair discussion but is a bit uncomfortable for spam actually in the can. Ouch!
Peak heat flux is very strongly a function of hypersonic lift/drag ratio and ballistic coefficient, so we don't really have a good comparison other than Shuttle.And the ability to predict either hypersonic lift or drag from shape alone is still quite limited.
...When entering Earth atmosphere (EDL) detecting a crack may be too late anyway. Because what could you do about it until landing?
...
But I think tiles will fail more likely during the ascent/descent, maybe in groups (multiple at a time), in an environment where plenty of sound and resonance apply. And filtering out a tile cracking sound of the noise of reentry does not sounds that easy (needs quite big dynamic range).
...
...
...When entering Earth atmosphere (EDL) detecting a crack may be too late anyway. Because what could you do about it until landing?
...
But I think tiles will fail more likely during the ascent/descent, maybe in groups (multiple at a time), in an environment where plenty of sound and resonance apply. And filtering out a tile cracking sound of the noise of reentry does not sounds that easy (needs quite big dynamic range).
...
...
Interesting point on L/D narrowing as mach goes up. Between you and envy stuff is getting pounded into my noggin.Peak heat flux is very strongly a function of hypersonic lift/drag ratio and ballistic coefficient, so we don't really have a good comparison other than Shuttle.And the ability to predict either hypersonic lift or drag from shape alone is still quite limited.
It also turns out the the L/D ratio narrows as the Mach number rises.
So your uncertainty rises just as margin of lift over drag falls. This is one of the things that has made designing SCramjets so hard.
Usually CFD types look to "anchor" the data with actual wind tunnel (or better yet flight) data. So the question is how closely does the SS design look like anything else in the database they have actual data on?
I would suggest the answer is "Not very." :(
Obviously they'll do the best job possible but I'd expect significant design changes when an SS actually starts flying.
Mars too....When entering Earth atmosphere (EDL) detecting a crack may be too late anyway. Because what could you do about it until landing?
...
But I think tiles will fail more likely during the ascent/descent, maybe in groups (multiple at a time), in an environment where plenty of sound and resonance apply. And filtering out a tile cracking sound of the noise of reentry does not sounds that easy (needs quite big dynamic range).
...
...
Heat transfer isn't that simple. The skin temp would rise from the equilibrium temp with the tile towards the equilibrium temp without it. However, that equilibrium temperature will likely not be the same as the stagnation temp of the gas flow.Much of that is over my head. While reading I was nodding my head and going ok, ok, and working towards a learning moment (for which I thank you). I do have a couple quibbles on what I did immediately understand.
For example, as the temperature of the skin approaches 1100 C, it will dump about 100 kW/m^2 via radiation to the cooler back walls of the tank. This goes up to 300 kW/m^2 at 1400 C. T^4 is your friend. The Shuttle TPS centerline flux peaked around 100 kW/m^2, so if the lost tile is over a tank or engine section, burn-through seems unlikely.
On the crew area, there will be insulation backing the skin, so that the crew compartment interior walls don't tend toward the 500+ degree skin temp. This is probably bad news for the skin, since it won't be able to dump heat radiatively to the interior. But that insulation might be able to handle the heat flux for long enough for the vehicle to finish reentry.
Shuttle EDL temps inform for a LEO reentry but would be an underestimate of higher energy reentries. SS coming from afar will do at least one skip so maybe this is a non-issue.
Maybe more important, "might be able to handle the heat flux" is fine for an armchair discussion but is a bit uncomfortable for spam actually in the can. Ouch!
Peak heat flux is very strongly a function of hypersonic lift/drag ratio and ballistic coefficient, so we don't really have a good comparison other than Shuttle.
And I have no idea what the insulation between the crew capsule interior and the hot structure will be, so I can't say if it will survive reentry or not. It should be possible to design it to survive in the event of losing a tile and a burn-through of the hot structure. At least, for one entry as a fail-safe.
The reason one tile falling off a tank skin isn't necessary fatal, while the same tank with no tiles at all would burn up, is because of the total heat flux. Without the tiles shielding most of the tank, the entire windward surface would heat up and glow, radiating heat through the tank to the lee surface - which would then also heat up and stop absorbing much heat from the windward side. Once the whole thing is glowing hot, it can't radiate heat internally, and it would probably melt. But with only a single time missing, only a tiny fraction of the windward side is radiating heat to the whole lee side, which would not heat up much.
It seems like there might be an opportunity for different approaches in the early design and the later designs by just adding redundancy. Instead of shielding half the ship at 10 tons, shield the entire ship at 20 tons. If an anomalous temp is detected beneath the tiles roll the ship to put good tiles into the heat.You do know that SS is going to have canard wings right?
It seems like there might be an opportunity for different approaches in the early design and the later designs by just adding redundancy. Instead of shielding half the ship at 10 tons, shield the entire ship at 20 tons. If an anomalous temp is detected beneath the tiles roll the ship to put good tiles into the heat.You do know that SS is going to have canard wings right?
And the passenger version will be part glazed on the nose.
does this still sound like a good idea to you?
It seems like there might be an opportunity for different approaches in the early design and the later designs by just adding redundancy. Instead of shielding half the ship at 10 tons, shield the entire ship at 20 tons. If an anomalous temp is detected beneath the tiles roll the ship to put good tiles into the heat.You do know that SS is going to have canard wings right?
And the passenger version will be part glazed on the nose.
does this still sound like a good idea to you?
Cargo versions will precede passenger versions to Mars, so no issue there for early flights.
Canard wings are the prevailing speculation on the forums and Musk has said there are new designs coming soon. I wasn't aware they'd become a certainty, have they? And, I wasn't aware that canard wings prohibit inverted flight (or falling), do they?
Cargo versions will precede passenger versions to Mars, so no issue there for early flights.It would invalidate any flight testing done by cargo flights, so yes there is an issue there.
Canard wings are the prevailing speculation on the forums and Musk has said there are new designs coming soon. I wasn't aware they'd become a certainty, have they? And, I wasn't aware that canard wings prohibit inverted flight (or falling), do they?Canards are what musk has called them. He has also stated that SS will generate lift so what do you call an aero surface that generates lift?
Cargo versions will precede passenger versions to Mars, so no issue there for early flights.It would invalidate any flight testing done by cargo flights, so yes there is an issue there.Quote from: wes_wilsonCanard wings are the prevailing speculation on the forums and Musk has said there are new designs coming soon. I wasn't aware they'd become a certainty, have they? And, I wasn't aware that canard wings prohibit inverted flight (or falling), do they?Canards are what musk has called them. He has also stated that SS will generate lift so what do you call an aero surface that generates lift?
I can see you're quite fond of this idea. But coming up with an idea and being fond of it doesn't make it viable. :(
Cargo versions will precede passenger versions to Mars, so no issue there for early flights.It would invalidate any flight testing done by cargo flights, so yes there is an issue there.Quote from: wes_wilsonCanard wings are the prevailing speculation on the forums and Musk has said there are new designs coming soon. I wasn't aware they'd become a certainty, have they? And, I wasn't aware that canard wings prohibit inverted flight (or falling), do they?Canards are what musk has called them. He has also stated that SS will generate lift so what do you call an aero surface that generates lift?
The movable surfaces on Starship are for adjusting drag, not lift. Yes drag can create lift, but at these high angles of attack (60-90 degrees) that will be a minor side effect at best. They LOOK like canards (and are therefore informally called canards) but will operate like air brakes. The vast majority of lift at re-entry angles will be coming from the body itself.QuoteI can see you're quite fond of this idea. But coming up with an idea and being fond of it doesn't make it viable. :(
I’m not going to touch that with a 10ft pole. ;)
It seems like there might be an opportunity for different approaches in the early design and the later designs by just adding redundancy. Instead of shielding half the ship at 10 tons, shield the entire ship at 20 tons. If an anomalous temp is detected beneath the tiles roll the ship to put good tiles into the heat.You do know that SS is going to have canard wings right?
And the passenger version will be part glazed on the nose.
does this still sound like a good idea to you?
Cargo versions will precede passenger versions to Mars, so no issue there for early flights.
Canard wings are the prevailing speculation on the forums and Musk has said there are new designs coming soon. I wasn't aware they'd become a certainty, have they? And, I wasn't aware that canard wings prohibit inverted flight (or falling), do they?
The skydiving reentry concept depends on moveable control surfaces. These are normally designed to operate with a defined hot side. The space shuttle, for example, would burn up if inverted during reentry. So would the Starship.
John
It seems like there might be an opportunity for different approaches in the early design and the later designs by just adding redundancy. Instead of shielding half the ship at 10 tons, shield the entire ship at 20 tons. If an anomalous temp is detected beneath the tiles roll the ship to put good tiles into the heat.You do know that SS is going to have canard wings right?
And the passenger version will be part glazed on the nose.
does this still sound like a good idea to you?
Cargo versions will precede passenger versions to Mars, so no issue there for early flights.
Canard wings are the prevailing speculation on the forums and Musk has said there are new designs coming soon. I wasn't aware they'd become a certainty, have they? And, I wasn't aware that canard wings prohibit inverted flight (or falling), do they?
The skydiving reentry concept depends on moveable control surfaces. These are normally designed to operate with a defined hot side. The space shuttle, for example, would burn up if inverted during reentry. So would the Starship.
John
Hi John, appreciate the answer! A follow up question if you don't mind? My original thought was to shield both sides of the ship to provide heat shield redundancy for early flights before the ability to do external inspections/repairs exist. Aside from the windows, I thought the designs floating around were symmetric so I'm still unclear why if both sides were shielded it couldn't re-enter with the bad side up and the good side down? Something about the canards that only works in one orientation, or the ship isn't actually symmetrical, etc?
Thanks
There could be profiles that might be sub optimal in other ways but easier on a damaged heat shield.But I think tiles will fail more likely during the ascent/descent, maybe in groups (multiple at a time), in an environment where plenty of sound and resonance apply. And filtering out a tile cracking sound of the noise of reentry does not sounds that easy (needs quite big dynamic range).When entering Earth atmosphere (EDL) detecting a crack may be too late anyway. Because what could you do about it until landing?
Possible yes. At that point you'd just want to get on the ground ASAP and figure everything else out later.There could be profiles that might be sub optimal in other ways but easier on a damaged heat shield.But I think tiles will fail more likely during the ascent/descent, maybe in groups (multiple at a time), in an environment where plenty of sound and resonance apply. And filtering out a tile cracking sound of the noise of reentry does not sounds that easy (needs quite big dynamic range).When entering Earth atmosphere (EDL) detecting a crack may be too late anyway. Because what could you do about it until landing?
Could a thin layer of PICA-X under the tiles work as a fail-safe for a damaged tile? No idea how thick the layer would need to be or how much mass it would add.That might be a good idea. In fact looking at the tiles it looks like they are multi layer - presumably some insulation is needed to stop the contents of the Starship heating up. Perhaps the insulation might save them in an emergency
Another question involving PicaX. Any idea if a PicaX heat shield would be cheaper or more expensive than the ceramic heat shield they are working on?Not sure it would be worth the effort of developing a separate heatshield for this. But depending on cost it might make sense to coat the steel under the heat shield with it for insulation and emergency protection from loss of a tile
Background of my question is the possibility of permanently leaving cargo Starships on Mars. They would need to do only one Mars entry, no problem with reuse and water after launch. Would it make economic sense to use a PicaX heatshield for those flights?
Another question involving PicaX. Any idea if a PicaX heat shield would be cheaper or more expensive than the ceramic heat shield they are working on?Not sure it would be worth the effort of developing a separate heatshield for this. But depending on cost it might make sense to coat the steel under the heat shield with it for insulation and emergency protection from loss of a tile
Background of my question is the possibility of permanently leaving cargo Starships on Mars. They would need to do only one Mars entry, no problem with reuse and water after launch. Would it make economic sense to use a PicaX heatshield for those flights?
Perhaps you're right, although I'm not sure what structural function it would serve as the titles would be supported through this layer on their studs. But if not PicaX then perhaps there's something else that might be suitable. Candidate materials need to be good insulators and also capable of providing so degree of last ditch emergency heat shield capability by ablation or any other mechanism to make tile loss a bit more survivable. The best part is no part, but they will need insulation anyway so this would just be added protection "for free".Another question involving PicaX. Any idea if a PicaX heat shield would be cheaper or more expensive than the ceramic heat shield they are working on?Not sure it would be worth the effort of developing a separate heatshield for this. But depending on cost it might make sense to coat the steel under the heat shield with it for insulation and emergency protection from loss of a tile
Background of my question is the possibility of permanently leaving cargo Starships on Mars. They would need to do only one Mars entry, no problem with reuse and water after launch. Would it make economic sense to use a PicaX heatshield for those flights?
If you put PicaX between the tiles and the underlying metal you'd be asking PicaX to perform structural functions. That's not really PicaX's forte.
How about stove cement?Stove cement is IIRC more of a grout with good thermal characteristics than a glue. Here is one companies offerings for aerospace.
I think it is some kind of water soluble silica
I don't think this has been remarked on but it appears that SpaceX is testing yet another TPS attachment approach. This makes at least four types:
1) Tile, 3 stud mechanically attached with holes showing and what looks like a felt pad against the tank.
2) Tile without holes showing, probable mechanically attached, with felt pad.
3) Tile mechanically attached using welded metal frame
4) Tile which appears to be bonded with green adhesive of some sort. (Does not look like RTV. RTV probably could not handle the temperature.)
John
They went to considerable effort for the goo. It looks like they roughed up the surface for better bonding. Maybe a replacement for Johns call of a felt pad in 1 & 2 above, plus bonding.I don't think this has been remarked on but it appears that SpaceX is testing yet another TPS attachment approach. This makes at least four types:
1) Tile, 3 stud mechanically attached with holes showing and what looks like a felt pad against the tank.
2) Tile without holes showing, probable mechanically attached, with felt pad.
3) Tile mechanically attached using welded metal frame
4) Tile which appears to be bonded with green adhesive of some sort. (Does not look like RTV. RTV probably could not handle the temperature.)
John
Or its some goo added for whatever purpose in addition to mechanical attachment.
The pads on shuttle were to deal with the thermal expansion coefficient of the aluminum being 3x that of the tile. AFAIK the mfg shut down the line and maybe out of business. It was some kind of nylon stocking material.They went to considerable effort for the goo. It looks like they roughed up the surface for better bonding. Maybe a replacement for Johns call of a felt pad in 1 & 2 above, plus bonding.I don't think this has been remarked on but it appears that SpaceX is testing yet another TPS attachment approach. This makes at least four types:
1) Tile, 3 stud mechanically attached with holes showing and what looks like a felt pad against the tank.
2) Tile without holes showing, probable mechanically attached, with felt pad.
3) Tile mechanically attached using welded metal frame
4) Tile which appears to be bonded with green adhesive of some sort. (Does not look like RTV. RTV probably could not handle the temperature.)
John
Or its some goo added for whatever purpose in addition to mechanical attachment.
The pads on shuttle were to deal with the thermal expansion coefficient of the aluminum being 3x that of the tile. AFAIK the mfg shut down the line and maybe out of business. It was some kind of nylon stocking material.They went to considerable effort for the goo. It looks like they roughed up the surface for better bonding. Maybe a replacement for Johns call of a felt pad in 1 & 2 above, plus bonding.I don't think this has been remarked on but it appears that SpaceX is testing yet another TPS attachment approach. This makes at least four types:
1) Tile, 3 stud mechanically attached with holes showing and what looks like a felt pad against the tank.
2) Tile without holes showing, probable mechanically attached, with felt pad.
3) Tile mechanically attached using welded metal frame
4) Tile which appears to be bonded with green adhesive of some sort. (Does not look like RTV. RTV probably could not handle the temperature.)
John
Or its some goo added for whatever purpose in addition to mechanical attachment.
Glue and pads were the lightweight quick fix. SS TCE is lower than aluminum (not sure how much). I'd have guess low enough not to need pads. They were part of the reason shuttle tile replacement costs wer listed at $12000/m^2.
If you're definitely going tiles and cost is a factor (which it is) and mass not so much that points you in certain directions.
More "graded" materials, rather than any kind of very thin skin. Shifting the coating method on some high damage tiles lowered the repair rate by a factor of 10. IE 1 damaged for every 10 that had needed replacement.
No messing around with glue. It's called room temperature vulcanizing adhesive for a reason. Either go to a hotter formulation (which makes removal tricky) or don't do glue.
NASA solved ways to mount materials not just with different TCE's but materials with different TCE's in different axes of the same material (RCC be the prime example) in the early 80's.
Obviously if you can break the tile into a couple of pieces, then remove those (like a spring driven center punch, but with a spade blade maybe?) then just remove the individual pieces.
Interesting pictures today by Nomadd of a heat shield test ring, half filled with tile fastening studs.
Appear to be testing the application of the studs in a bulk situation, as they would do it on an actual install.
There are two types of studs being applied to the test hull - A round version with flats milled on the outside and a hole in the center (threaded or not) and an 'open spring clip' (don't know how else to describe it).
Photo by Nomadd (cropped):
You could update this idea for the digital age. Put an RFID chip and and antenna loop in each tile, just like in a credit card. Then each tile has a separate unique ID and you can interrogate a bunch of them in parallel. You'd need to keep the loop some minimum distance away from the steel hull, of course.IIRC this has already been mentioned in this thread.
HelloGreat question. Nobody's replied yet so I'll take a shot. I doubt the tiles will be airtight and for an overall solution, well, I don't know.
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
Hello
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
HelloGreat question. Nobody's replied yet so I'll take a shot. I doubt the tiles will be airtight and for an overall solution, well, I don't know.
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
Not much help :(
Phil
Hello
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
HelloGreat question. Nobody's replied yet so I'll take a shot. I doubt the tiles will be airtight and for an overall solution, well, I don't know.
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
Not much help :(
Phil
I don't think it's practical to seal the tiles airtight and have them properly serve their main function.
I'm most interested in the heat-shield and see that it's the biggest risk to the whole venture. First concern is how well they endure the changing shape changing of the tanks when they pressurize and what will happen when the body of the vehicle encounters the pressure of re-entry.
Then the transition from the pressurized tank section and the unpressurized sections fore and aft.
Seems like those would be significant, maybe each tile can handle it. But we haven't seen it yet. No doubt there is a lot of work going into it.
There seems to be a need to have a gap between the tiles to allow for expansion. Presumably this will be self correcting to a limited extent - the hotter the tiles get the less the gap and less heat seeps through. That said I'm not sure how much heat seepage is permissible or how much insulation there will be below the tiles?HelloGreat question. Nobody's replied yet so I'll take a shot. I doubt the tiles will be airtight and for an overall solution, well, I don't know.
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
Not much help :(
Phil
I don't think it's practical to seal the tiles airtight and have them properly serve their main function.
I'm most interested in the heat-shield and see that it's the biggest risk to the whole venture. First concern is how well they endure the changing shape changing of the tanks when they pressurize and what will happen when the body of the vehicle encounters the pressure of re-entry.
Then the transition from the pressurized tank section and the unpressurized sections fore and aft.
Seems like those would be significant, maybe each tile can handle it. But we haven't seen it yet. No doubt there is a lot of work going into it.
So there's not the risk from expansion. But if the frost forms under the tiles, what happens to it during the launch. As it shakes free and drops off, (but still under the tiles), does it not risk damaging the tile mounts and or tiles? I know... SpaceX must know what they're doing and have some plan in place. I'm just wondering what that might be.Hello
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
The frost on the tanks during propellant load is formed by continuous vapor deposition, which doesn't cause the expansion force associated with freezing liquid water.
So there's not the risk from expansion. But if the frost forms under the tiles, what happens to it during the launch. As it shakes free and drops off, (but still under the tiles), does it not risk damaging the tile mounts and or tiles? I know... SpaceX must know what they're doing and have some plan in place. I'm just wondering what that might be.Hello
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
The frost on the tanks during propellant load is formed by continuous vapor deposition, which doesn't cause the expansion force associated with freezing liquid water.
Hello
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
As far as I can remember, hexagonal tiles were chosen so that there's no straight air channel along the gaps, and they aren't concerned about the tiles not being airtight as long as the majority of flow is across the outer surface. I could be misremembering though.
For all of the above stated reasons, I believe the tiles will be mounted on something like Nomex felt between the tile and the tank. Instead of bonding like the Shuttle did, it appears they will be attached using studs. This allow each tile to deal with vehicle deformations due to stresses applied throughout the mission. Between some tiles we may see filler material similar to that used on the Shuttle, but we have not seen any sign of that so far.That makes no sense.
John
I hope that will work on Mars as well, because Starship will be on Mars with cryogenic propellant aboard for more than a year.So there's not the risk from expansion. But if the frost forms under the tiles, what happens to it during the launch. As it shakes free and drops off, (but still under the tiles), does it not risk damaging the tile mounts and or tiles? I know... SpaceX must know what they're doing and have some plan in place. I'm just wondering what that might be.Hello
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
The frost on the tanks during propellant load is formed by continuous vapor deposition, which doesn't cause the expansion force associated with freezing liquid water.
There's a rope seal is under the tile to keep hot gases out during reenty. Frost forms from atmospheric water vapor, and the rope seal should prevent air from entering the space under the tile.
I hope that will work on Mars as well, because Starship will be on Mars with cryogenic propellant aboard for more than a year.So there's not the risk from expansion. But if the frost forms under the tiles, what happens to it during the launch. As it shakes free and drops off, (but still under the tiles), does it not risk damaging the tile mounts and or tiles? I know... SpaceX must know what they're doing and have some plan in place. I'm just wondering what that might be.Hello
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
The frost on the tanks during propellant load is formed by continuous vapor deposition, which doesn't cause the expansion force associated with freezing liquid water.
There's a rope seal is under the tile to keep hot gases out during reenty. Frost forms from atmospheric water vapor, and the rope seal should prevent air from entering the space under the tile.
I hope that will work on Mars as well, because Starship will be on Mars with cryogenic propellant aboard for more than a year.So there's not the risk from expansion. But if the frost forms under the tiles, what happens to it during the launch. As it shakes free and drops off, (but still under the tiles), does it not risk damaging the tile mounts and or tiles? I know... SpaceX must know what they're doing and have some plan in place. I'm just wondering what that might be.Hello
I have a question.
Since there is no thermal insulation of the tanks (well, not yet), how will they avoid the frost/ice formation to break the tiles apart?
Will the gap between the tiles be perfectly airtight insulated?
The frost on the tanks during propellant load is formed by continuous vapor deposition, which doesn't cause the expansion force associated with freezing liquid water.
There's a rope seal is under the tile to keep hot gases out during reenty. Frost forms from atmospheric water vapor, and the rope seal should prevent air from entering the space under the tile.
The atmosphere on Mars is so thin that any water that somehow forms on the surface of SS while it's sitting there will just sublimate away......
For all of the above stated reasons, I believe the tiles will be mounted on something like Nomex felt between the tile and the tank. Instead of bonding like the Shuttle did, it appears they will be attached using studs. This allow each tile to deal with vehicle deformations due to stresses applied throughout the mission. Between some tiles we may see filler material similar to that used on the Shuttle, but we have not seen any sign of that so far.That makes no sense.
John
Firstly steel is about 1/10 the thermal conductivity of aluminum and IIRC it's expansion coefficient is about 1/3 that of aluminum. So the tanks contents are easier to keep cool and the tank stresses caused by expansion and contraction are much reduced.
The key reason for the pads was that the tiles were bonded to the aluminum skin originally so as the skin expanded the tiles either cracked (reducing most of them to about 6" wide as the safe size) or peeled. The pads isolated the tiles excellent thermal but poor mechanical properties from the skins excellent mechanical but poor thermal properties.
But SS tiles are point mounted, which should simplify mounting them, although the reduced expansion should also reduce stress on the tiles anyway.
I'm actually more concerned about water between and under the tiles on Earth.
There will be small gaps between the tiles and a small space underneath the tiles.
These spaces may or may not have some form of padding or filling material....
The problem with small gaps and spaces are that they are great at drawing in water through capillary action. This water then is very hard to get out.
So....... The SS is sitting on the pad waiting for fueling and launch and it's raining.
Water is drawn between and below the tiles, largely filling the gaps.
You then add cryogenic fuel and oxidiser.
The water freezes, how much damage to the tiles does this cause?
How much additional weight is added to the vehicle from this trapped water? I would imagine it's non-trivial......
Do we know how the Space Shuttle was affected by this?
Perhaps the gaps between the tiles and mounting hardware and the gaps between the tiles themselves meant to accomodate reentry heat expansion are large enough to also accomodate expansion from frozen rainwater and humidity. It's not like both icy tile gaps and red hot expanded tiles are ever going to be a threat at the same time and compound each other or anything.Actually they might be.
I'm actually more concerned about water between and under the tiles on Earth.Depends on the porosity and surface tension of the tile material.
There will be small gaps between the tiles and a small space underneath the tiles.
These spaces may or may not have some form of padding or filling material....
The problem with small gaps and spaces are that they are great at drawing in water through capillary action. This water then is very hard to get out.
So....... The SS is sitting on the pad waiting for fueling and launch and it's raining.
Water is drawn between and below the tiles, largely filling the gaps.
You then add cryogenic fuel and oxidiser.
The water freezes, how much damage to the tiles does this cause?
How much additional weight is added to the vehicle from this trapped water? I would imagine it's non-trivial......
Do we know how the Space Shuttle was affected by this?The short answer is badly :(
I'm actually more concerned about water between and under the tiles on Earth.Depends on the porosity and surface tension of the tile material.
There will be small gaps between the tiles and a small space underneath the tiles.
These spaces may or may not have some form of padding or filling material....
The problem with small gaps and spaces are that they are great at drawing in water through capillary action. This water then is very hard to get out.
So....... The SS is sitting on the pad waiting for fueling and launch and it's raining.
Water is drawn between and below the tiles, largely filling the gaps.
You then add cryogenic fuel and oxidiser.
The water freezes, how much damage to the tiles does this cause?
How much additional weight is added to the vehicle from this trapped water? I would imagine it's non-trivial......Quote from: Nevyn72Do we know how the Space Shuttle was affected by this?The short answer is badly :(
All shuttle tiles were injected with a organic water repellent. Pretty nasty stuff AIUI which burnt off on re-entry, multiplying the refurb work on the TPS.
Given the tiles were about 95% air and 5% tile they worked exactly like a sponge and IIRC could absorb several times their own weight in water.
In the later stages of the STS programme an applied physics team at Johnson (IIRC) developed a vacuum dewatering process that multiplied dry out rate several fold (ready in 1/3-1/4 the time of natural process).
Ames had developed a permanent solution using inorganic fluorides, which raised the surface tension and hence made the tiles repel water rather than suck it up. They never got permission to flight test it so we'll never know how permanent this solution was. :(
Given we know ceramic tiles were not SX's first choice you can bet they have studied the pitfalls of this approach closely. The benefit of being the second user of such material is that you can use the known issues list and avoid them in design (point mounting, not bonding. Allowing enough spacing that capillary action is not an issue etc) rather than having to live with them.
The fact we've already been seeing sample tiles in place indicates this is technology SX are very keen to get right.
The area where shuttle can give no guidance is what happens when you put those tiles on mars for 26 months of thermal cycling, dust storms etc before taking off to come back to earth.
The answer is (hopefully) nothing very much, but there is a very good reason why those first flights won't have a crew on board.
For all of the above stated reasons, I believe the tiles will be mounted on something like Nomex felt between the tile and the tank. Instead of bonding like the Shuttle did, it appears they will be attached using studs. This allow each tile to deal with vehicle deformations due to stresses applied throughout the mission. Between some tiles we may see filler material similar to that used on the Shuttle, but we have not seen any sign of that so far.That makes no sense.
John
Firstly steel is about 1/10 the thermal conductivity of aluminum and IIRC it's expansion coefficient is about 1/3 that of aluminum. So the tanks contents are easier to keep cool and the tank stresses caused by expansion and contraction are much reduced.
The key reason for the pads was that the tiles were bonded to the aluminum skin originally so as the skin expanded the tiles either cracked (reducing most of them to about 6" wide as the safe size) or peeled. The pads isolated the tiles excellent thermal but poor mechanical properties from the skins excellent mechanical but poor thermal properties.
But SS tiles are point mounted, which should simplify mounting them, although the reduced expansion should also reduce stress on the tiles anyway.
I wonder whether they could just have the tile standoff from the hull. The 3 point studs could have a spacer or step to prevent the tile from contacting the hull. No porous material to soak up frozen water. Air is a good insulator as long as it's velocity is limited.
The X-33 was going to use high temp metal with standoffs from the composite hull. And it had metal tiles instead of ceramic tiles. Right?
For all of the above stated reasons, I believe the tiles will be mounted on something like Nomex felt between the tile and the tank. Instead of bonding like the Shuttle did, it appears they will be attached using studs. This allow each tile to deal with vehicle deformations due to stresses applied throughout the mission. Between some tiles we may see filler material similar to that used on the Shuttle, but we have not seen any sign of that so far.That makes no sense.
John
Firstly steel is about 1/10 the thermal conductivity of aluminum and IIRC it's expansion coefficient is about 1/3 that of aluminum. So the tanks contents are easier to keep cool and the tank stresses caused by expansion and contraction are much reduced.
The key reason for the pads was that the tiles were bonded to the aluminum skin originally so as the skin expanded the tiles either cracked (reducing most of them to about 6" wide as the safe size) or peeled. The pads isolated the tiles excellent thermal but poor mechanical properties from the skins excellent mechanical but poor thermal properties.
But SS tiles are point mounted, which should simplify mounting them, although the reduced expansion should also reduce stress on the tiles anyway.
- Mounting brittle tiles to stainless steel surfaces which are subjected to thermal, structural, vibration loads and localized buckling would benefit from some isolation. A felt insulating layer applied as a sheet before tile are applied would provide structural isolation, damping and gap insulation.
John
Perhaps the gaps between the tiles and mounting hardware and the gaps between the tiles themselves meant to accomodate reentry heat expansion are large enough to also accomodate expansion from frozen rainwater and humidity. It's not like both icy tile gaps and red hot expanded tiles are ever going to be a threat at the same time and compound each other or anything.Actually they might be.
Reentry during a rain storm?
Another problem that needs to be solved is cryopumping while fueled on the pad.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040001153.pdf
Water vapor will tend to condense inside the insulation. It will then rapidly expand upon during launch. TPS needs to minimize water and vapor entry but also allow for it to escape easily enough so as not to cause damage to the tile.
John
I wonder whether they could just have the tile standoff from the hull. The 3 point studs could have a spacer or step to prevent the tile from contacting the hull. No porous material to soak up frozen water. Air is a good insulator as long as it's velocity is limited.Yes that's how I'm picturing this.
The X-33 was going to use high temp metal with standoffs from the composite hull. And it had metal tiles instead of ceramic tiles. Right?"Metal" is a bit of an exaggeration.
The shuttle tiles never got cryogenic cold. I believe this will be the first vehicle with tiles to have cryogenic cold and 3000F reentry temp.(not at the same time)Good point.
- Mounting brittle tiles to stainless steel surfaces which are subjected to thermal, structural, vibration loads and localized buckling would benefit from some isolation. A felt insulating layer applied as a sheet before tile are applied would provide structural isolation, damping and gap insulation.Agreed, but AIUI that is what the studs provide. :(
John
- Mounting brittle tiles to stainless steel surfaces which are subjected to thermal, structural, vibration loads and localized buckling would benefit from some isolation. A felt insulating layer applied as a sheet before tile are applied would provide structural isolation, damping and gap insulation.Agreed, but AIUI that is what the studs provide. :(
John
The only actual contact between the tiles and the skin is through those studs, so the only way the skin can stress them is through loads through the studs.
Tiles absorbing water is harder to deal with, though. They'd need either some sort of high melting point coating compound, or maybe they could put the tiles through some sort of torch treatment to vitrify the surface and melt it into a thin solid layer? Even then, you still have to worry about the area where the fasteners are embedded.Bad idea. This roughly describes the shuttle tile coating. That thin layer was very brittle and prone to impact damage. When a newer (but heavier) design was developed that created a graded protection running deeper into the tile that had 1/10 the number of damaged tiles.
Water trapped inside the tiles vaporizing is bad, especially if the tiles are sealed.Quite true.
5 ring high section.
Another section stacked in the mid bay.
Inside tent #1.
One of the new robotic arms are already installed and labelled "heat shield". With that i think the questions about stud installation are settled. Seems like automated installation, to barrel segments, before stacking. (quite the opposite to what I guessed).
Will be interesting to see how they address the stud alignment through stacking. But maybe with the gaps beetween tiles (hence more tolerant tile positioning) that would not be a big problem at all.
See the last photo in this post by BCG.5 ring high section.
Another section stacked in the mid bay.
Inside tent #1.
One of the new robotic arms are already installed and labelled "heat shield". With that i think the questions about stud installation are settled. Seems like automated installation, to barrel segments, before stacking. (quite the opposite to what I guessed).They just got these welding bots last week. I would expect them to try out the new process on some rings rather than a completed tank.
Will be interesting to see how they address the stud alignment through stacking. But maybe with the gaps beetween tiles (hence more tolerant tile positioning) that would not be a big problem at all.
See the last photo in this post by BCG.5 ring high section.
Another section stacked in the mid bay.
Inside tent #1.
One of the new robotic arms are already installed and labelled "heat shield". With that i think the questions about stud installation are settled. Seems like automated installation, to barrel segments, before stacking. (quite the opposite to what I guessed).
Will be interesting to see how they address the stud alignment through stacking. But maybe with the gaps between tiles (hence more tolerant tile positioning) that would not be a big problem at all.
See the last photo in this post by BCG.5 ring high section.
Another section stacked in the mid bay.
Inside tent #1.
They may have already done that.One of the new robotic arms are already installed and labelled "heat shield". With that i think the questions about stud installation are settled. Seems like automated installation, to barrel segments, before stacking. (quite the opposite to what I guessed).They just got these welding bots last week. I would expect them to try out the new process on some rings rather than a completed tank.
Will be interesting to see how they address the stud alignment through stacking. But maybe with the gaps beetween tiles (hence more tolerant tile positioning) that would not be a big problem at all.
See the last photo in this post by BCG.5 ring high section.
Another section stacked in the mid bay.
Inside tent #1.
it looks like the tiles with 3 holes visible from the outside broke. The tiles above do not have these holes and are looking quite good. I think they got the data they wanted.
OTOH, the landing, especially on short legs and at 1 atm, might involve some of the worst pressure and vibration loads on the skirt.it looks like the tiles with 3 holes visible from the outside broke. The tiles above do not have these holes and are looking quite good. I think they got the data they wanted.They don't look great. But it's some data. Even if it's a very short gentle flight.
Making orbit and back is a lot more aggressive. But great to be start taking a shot and seeing what works.
it looks like the tiles with 3 holes visible from the outside broke. The tiles above do not have these holes and are looking quite good. I think they got the data they wanted.
They don't look great. But it's some data. Even if it's a very short gentle flight.
Making orbit and back is a lot more aggressive. But great to be start taking a shot and seeing what works.
The image on SN5 in flight tweeted by Elon is right at the limit with regard to resolution and angle but it looks like the three bottom/right "single spiral fitting" tiles are already gone while at least one of the "three rods" tiles is still there.OTOH, the landing, especially on short legs and at 1 atm, might involve some of the worst pressure and vibration loads on the skirt.it looks like the tiles with 3 holes visible from the outside broke. The tiles above do not have these holes and are looking quite good. I think they got the data they wanted.They don't look great. But it's some data. Even if it's a very short gentle flight.
Making orbit and back is a lot more aggressive. But great to be start taking a shot and seeing what works.
it looks like the tiles with 3 holes visible from the outside broke. The tiles above do not have these holes and are looking quite good. I think they got the data they wanted.
They don't look great. But it's some data. Even if it's a very short gentle flight.
Making orbit and back is a lot more aggressive. But great to be start taking a shot and seeing what works.
I think seeing tiles pristine, nearly destroyed, and missing completely next to what is obviously more than one mounting system is a really good sign. It means the solution for mounting the tiles is rich with different options (if hopefully not profuse with them).
This "see what sticks" approach likely means they're not butting up against the limitations of their materials yet. In iterative development, the first iterations always see the largest differences between each other and it's usually easiest to see what to change at that stage. It would be much more worrying if we saw tiles like this destroyed on SN15 or something all with the same type of mounting hardware exposed.
Speculation:
- It appears to me that these tiles got hit hard, probably early in the flight.
- The white tubes attached to the studs appear to have been molded into a solid block of insulation.
- The spiral connectors don't appear to have any white insulation substrate on them. Makes me think they were not bonded or did not bond well to the insulation block.
- From the rub marks under the missing tiles, it appears that they had isolation padding around the perimeter and one in the center.
- It looks like there is some inter-tile filler between some of the tile.
Comments, other ideas?
John
Speculation:I was of the mindset that the majority of the damage was shock caused from the landing - it's must have been one heck of a jar to cause the collapsing of the large hole area of the bottom half of the legs. These tiles look hard, un-elastic and brittle. The ones with the cracks look like the cracks propagate from the three mounting studs in each time. Those tiles may not have had any of the adhesive bonding that the top row appears to have, so they were more prone to shock at the mounting points (as opposed to having bonding all around)
- It appears to me that these tiles got hit hard, probably early in the flight.
- The white tubes attached to the studs appear to have been molded into a solid block of insulation.
- The spiral connectors don't appear to have any white insulation substrate on them. Makes me think they were not bonded or did not bond well to the insulation block.
- From the rub marks under the missing tiles, it appears that they had isolation padding around the perimeter and one in the center.
- It looks like there is some inter-tile filler between some of the tile.
Comments, other ideas?
John
Speculation:I was of the mindset that the majority of the damage was shock caused from the landing - it's must have been one heck of a jar to cause the collapsing of the large hole area of the bottom half of the legs. These tiles look hard, un-elastic and brittle. The ones with the cracks look like the cracks propagate from the three mounting studs in each time. Those tiles may not have had any of the adhesive bonding that the top row appears to have, so they were more prone to shock at the mounting points (as opposed to having bonding all around)
- It appears to me that these tiles got hit hard, probably early in the flight.
- The white tubes attached to the studs appear to have been molded into a solid block of insulation.
- The spiral connectors don't appear to have any white insulation substrate on them. Makes me think they were not bonded or did not bond well to the insulation block.
- From the rub marks under the missing tiles, it appears that they had isolation padding around the perimeter and one in the center.
- It looks like there is some inter-tile filler between some of the tile.
Comments, other ideas?
John
Speculation:IMHO Vibrations. Sound energy making the steel sheet oscillate hard.
- It appears to me that these tiles got hit hard, probably early in the flight.
- The white tubes attached to the studs appear to have been molded into a solid block of insulation.Dunno, but to me it looks like that they were placed in a star pattern and the tile mounted over.
Maybe they were cast in the tile?
- The spiral connectors don't appear to have any white insulation substrate on them. Makes me think they were not bonded or did not bond well to the insulation block.
- From the rub marks under the missing tiles, it appears that they had isolation padding around the perimeter and one in the center.
- It looks like there is some inter-tile filler between some of the tile.
Comments, other ideas?
John
- Very sceptical that such damage was done by vibration. The damaged tile look flattened.IMHO on earlier runs the skirt was more rigid as it was fixed to launch mount so the amplitudes and accelerations were lower.
- Also, why didn't any damage happen on earlier engine runs?
John
Speculation:I was of the mindset that the majority of the damage was shock caused from the landing - it's must have been one heck of a jar to cause the collapsing of the large hole area of the bottom half of the legs. These tiles look hard, un-elastic and brittle. The ones with the cracks look like the cracks propagate from the three mounting studs in each time. Those tiles may not have had any of the adhesive bonding that the top row appears to have, so they were more prone to shock at the mounting points (as opposed to having bonding all around)
- It appears to me that these tiles got hit hard, probably early in the flight.
- The white tubes attached to the studs appear to have been molded into a solid block of insulation.
- The spiral connectors don't appear to have any white insulation substrate on them. Makes me think they were not bonded or did not bond well to the insulation block.
- From the rub marks under the missing tiles, it appears that they had isolation padding around the perimeter and one in the center.
- It looks like there is some inter-tile filler between some of the tile.
Comments, other ideas?
John
- Very sceptical that such damage was done by vibration. The damaged tile look flattened.
- Also, why didn't any damage happen on earlier engine runs?
John
- Very sceptical that such damage was done by vibration. The damaged tile look flattened.One interesting thing is that tiles look like some of them were splashed with something, and more interestingly only those splashed are broken or missing.
- Also, why didn't any damage happen on earlier engine runs?
John
- Very sceptical that such damage was done by vibration. The damaged tile look flattened.One interesting thing is that tiles look like some of them were splashed with something, and more interestingly only those splashed are broken or missing.
- Also, why didn't any damage happen on earlier engine runs?
John
Looking close, it looks like scouring. And it carries over into the undamaged tiles but much reduced. Maybe they're playing with different surface treatments?- Very sceptical that such damage was done by vibration. The damaged tile look flattened.One interesting thing is that tiles look like some of them were splashed with something, and more interestingly only those splashed are broken or missing.
- Also, why didn't any damage happen on earlier engine runs?
John
Water from the noise suppression system, followed by dust sticking to the wet parts during the flight?
I wonder what are those star shaped bars?Here's a blowup of Mary's pic of the bars. Weird. They seem to have a woven surface and the ends appear tied off. Almost look like heavy tubes of sand used for vehicle traction in snow. They also appeared to either be fixed on the outer end of the mounting pins or are free to slide and just happen to be there. One set is in a 'Y' configuration, the others are random. Could it be that they are normally in a delta configuration? I almost feel like I'm talking about generator wiring.
Some of them stay star shaped, others like they've been knocked around.
Tiles mounted to bars mounted to studs to allow the studs to slid out as they expand?
Bars molded into the tiles?
BTW I'm pretty sure SX won't want to go the isolation pad/bonding route. That was very fiddly and expensive.
Not impossible to automate but I can see it being very tricky. How do you define "Press it down just hard enough to stick to the pad, but not to glue the pad material to the skin" ? :(
maybe harder ceramic tubes to spread the load into the bulk of the tile. Bonding between the hard ceramic and the exterior tile ceramic might be weak, so maybe a fiberglass sock around the tube/rod to act as reinforcement, like wire mesh in concreteI wonder what are those star shaped bars?Here's a blowup of Mary's pic of the bars. Weird. They seem to have a woven surface and the ends appear tied off. Almost look like heavy tubes of sand used for vehicle traction in snow. They also appeared to either be fixed on the outer end of the mounting pins or are free to slide and just happen to be there. One set is in a 'Y' configuration, the others are random. Could it be that they are normally in a delta configuration? I almost feel like I'm talking about generator wiring.
Some of them stay star shaped, others like they've been knocked around.
Tiles mounted to bars mounted to studs to allow the studs to slid out as they expand?
Bars molded into the tiles?
BTW I'm pretty sure SX won't want to go the isolation pad/bonding route. That was very fiddly and expensive.
Not impossible to automate but I can see it being very tricky. How do you define "Press it down just hard enough to stick to the pad, but not to glue the pad material to the skin" ? :(
It's really impossible to say what the material is. The only thing that comes to mind is woven fiberglass but it looks like Teflon. Teflon makes no sense from a heat perspective. I'm running mental models of what might be going on here but nothing is clear enough to even warrant a speculation.
The second pic from Mary shows tiles on the rings where the robot was working. The point of interest is a few tiles on the left side. There is something white along the edge. The camera angle is from the right so whatever we're seeing is not tile edge. Maybe those external clip arrangements or maybe part of a felt pad or extruded goop.
A side point. Not all the pins have tiles. Can't see it in this crop but the tiles are laid out in a big 'X'. How autonomous is that robot? Are we seeing emergent AH? Artificial Humor? ???
Phil
I think they are trolling us! But that is very cool, but it looks like they have a spacing issue.
I think the spacing is quite deliberate.
All of these tiles appear to be the 'three pin through' type, all of which either fell off or were cracked on SN5.
The spacing appears greater than that on SN5, mostly a little bit, although you can see the metal skin in between, and quite a bit down the centre line. Perhaps they are trying to test if vibrations are causing the tiles to bump against each other and fail due to brittleness? How big a gap is required to aviod this?
I will be curious to see if other methods for affixing tiles are used on different parts of this barrel section.
I wonder if this is a pathfinder for tile fixing or if it will actually fly?
You have to "learn" a robot, so this very well might just be a first step to adjust it to the work needed. No need to panic or such things here because there are gaps between the tiles.Yes I suspect they are still trying out different tile arrangements and types so they have not focused on the spacing element yet. It seems that the white support elements have been arranged in such a way that there are diamond shaped spaces below the tiles that alternate between layers (upright "Y" upside down "Y" on each layer of tile supports.
I wonder what are those star shaped bars?Here's a blowup of Mary's pic of the bars. Weird. They seem to have a woven surface and the ends appear tied off. Almost look like heavy tubes of sand used for vehicle traction in snow. They also appeared to either be fixed on the outer end of the mounting pins or are free to slide and just happen to be there. One set is in a 'Y' configuration, the others are random. Could it be that they are normally in a delta configuration? I almost feel like I'm talking about generator wiring.
Some of them stay star shaped, others like they've been knocked around.
Tiles mounted to bars mounted to studs to allow the studs to slid out as they expand?
Bars molded into the tiles?
BTW I'm pretty sure SX won't want to go the isolation pad/bonding route. That was very fiddly and expensive.
Not impossible to automate but I can see it being very tricky. How do you define "Press it down just hard enough to stick to the pad, but not to glue the pad material to the skin" ? :(
It's really impossible to say what the material is. The only thing that comes to mind is woven fiberglass but it looks like Teflon. Teflon makes no sense from a heat perspective. I'm running mental models of what might be going on here but nothing is clear enough to even warrant a speculation.
The second pic from Mary shows tiles on the rings where the robot was working. The point of interest is a few tiles on the left side. There is something white along the edge. The camera angle is from the right so whatever we're seeing is not tile edge. Maybe those external clip arrangements or maybe part of a felt pad or extruded goop.
A side point. Not all the pins have tiles. Can't see it in this crop but the tiles are laid out in a big 'X'. How autonomous is that robot? Are we seeing emergent AH? Artificial Humor? ???
Phil
Sequence of current heat shield mounting (IMHO):I wonder what are those star shaped bars?Here's a blowup of Mary's pic of the bars. Weird. They seem to have a woven surface and the ends appear tied off. Almost look like heavy tubes of sand used for vehicle traction in snow. They also appeared to either be fixed on the outer end of the mounting pins or are free to slide and just happen to be there. One set is in a 'Y' configuration, the others are random. Could it be that they are normally in a delta configuration? I almost feel like I'm talking about generator wiring.
Some of them stay star shaped, others like they've been knocked around.
Tiles mounted to bars mounted to studs to allow the studs to slid out as they expand?
Bars molded into the tiles?
BTW I'm pretty sure SX won't want to go the isolation pad/bonding route. That was very fiddly and expensive.
Not impossible to automate but I can see it being very tricky. How do you define "Press it down just hard enough to stick to the pad, but not to glue the pad material to the skin" ? :(
It's really impossible to say what the material is. The only thing that comes to mind is woven fiberglass but it looks like Teflon. Teflon makes no sense from a heat perspective. I'm running mental models of what might be going on here but nothing is clear enough to even warrant a speculation.
The second pic from Mary shows tiles on the rings where the robot was working. The point of interest is a few tiles on the left side. There is something white along the edge. The camera angle is from the right so whatever we're seeing is not tile edge. Maybe those external clip arrangements or maybe part of a felt pad or extruded goop.
A side point. Not all the pins have tiles. Can't see it in this crop but the tiles are laid out in a big 'X'. How autonomous is that robot? Are we seeing emergent AH? Artificial Humor? ???
Phil
The white tubes are ceramic fire rope / furnace gasket.
I just noticed that the tiles have been applied in the shape of the SpaceX logo
(photo from bocachicagal)
The white tubes are ceramic fire rope / furnace gasket.
Positioning accuracy is a solved problem. In the 1980's Intelledex arms had each joint premapped for mechanical irregularities and burned into a ROM on the controller. IIRC the accuracy was measured in thousandths of an inch. Don't remember the precision.I just noticed that the tiles have been applied in the shape of the SpaceX logo
(photo from bocachicagal)
My wishful thinking theory that I realize is most likely not true:
They developed a software that dynamically and procedurally spreads and arranges tiles in the most optimal way for a given surface. What we are seeing is a result of a test of that software after importing a bitmap with SpaceX's logo and clicking "print".
I suppose automatic tracking of position and orientation with sub mm precision relatively to this kind of article would be extremely difficult to implement. But it would be so awesome to have a "smart" adaptive heat shield printing robot...
What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
That tweet is 11 months stale. Mary's pic from this afternoon shows something that might be called marshmallowy sandwiched under some of the tiles. Elon was talking about furnace rope or something similar stuffed in the space between tiles.What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
https://twitter.com/elonmusk/status/1171308928476385281 (https://twitter.com/elonmusk/status/1171308928476385281)
What’s to say that it’s not a more rigid material encased by the rope? Basically a composite of sorts. The tie offs and fraying at the end to me indicate the ceramic rope while the rigidity of the pieces points toward something rigid.That tweet is 11 months stale. Mary's pic from this afternoon shows something that might be called marshmallowy sandwiched under some of the tiles. Elon was talking about furnace rope or something similar stuffed in the space between tiles.What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
https://twitter.com/elonmusk/status/1171308928476385281 (https://twitter.com/elonmusk/status/1171308928476385281)
Those tubes in my earlier posts are impaled on the studs. Can't see them sealing anything.
Phil
This tweet may be 11 months old but Musks point still stands.
https://twitter.com/elonmusk/status/1171308928476385281
What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
So how serious is the loss of a single tile to Starship? Presumably there are some areas where loss of a tile would be catastrophic, but what percentage? 10%, 50% 90%. How survivable is the loss of 1 tile and how likely is the loss of 1 tile going to lead to the loss of a lot more down wind? Or is this the $64,000 question?
So how serious is the loss of a single tile to Starship? Presumably there are some areas where loss of a tile would be catastrophic, but what percentage? 10%, 50% 90%. How survivable is the loss of 1 tile and how likely is the loss of 1 tile going to lead to the loss of a lot more down wind? Or is this the $64,000 question?
Nobody outside of SpaceX knows for sure, but I think there's a general sense among most observers that loss of any single tile will not lead to the loss of the vehicle.
This isn't like the shuttle where there was aluminum underneath with a low melting temperature. This is stainless steel, with a very high melting temperature. Heating absorbed through one missing tile will be transferred over a wide area of the steel skin.
So how serious is the loss of a single tile to Starship? Presumably there are some areas where loss of a tile would be catastrophic, but what percentage? 10%, 50% 90%. How survivable is the loss of 1 tile and how likely is the loss of 1 tile going to lead to the loss of a lot more down wind? Or is this the $64,000 question?
Nobody outside of SpaceX knows for sure, but I think there's a general sense among most observers that loss of any single tile will not lead to the loss of the vehicle.
This isn't like the shuttle where there was aluminum underneath with a low melting temperature. This is stainless steel, with a very high melting temperature. Heating absorbed through one missing tile will be transferred over a wide area of the steel skin.
Stainless is a lousy conductor and the conduction path in the lateral direction is very thin, so I wouldn't expect heat to go sideways far from the patch directly under a missing tile. What it will do is heat up and then radiatively transfer at t^4 to the rest of the tank interior. Since stainless can tolerate a considerably higher temp than aluminum, the t^4 heat transfer is much, much higher, and can easily reach equilibrium with ~100 kW/m^2 heat flux on the windward side.
Since the underside of 1 tile is ~0.1 square m, and the rest of the tank interior is around 100 to 1000 square m, the heat flux at the rest of the tank is very low. So losing 1 tile is probably not an issue at all. Losing 10 tiles might be a problem. Losing 1000 is probably a very serious issue, since that would be a large hot spot that can't shed enough heat to the inside of the vehicle to maintain equilibrium while still cool enough for stainless to maintain enough strength to hold tank pressure.
I thought SX was using much stronger tiles... not Alumina ones! The SX pictures of testing them last year.... left me with the impression of a glazed metallic tile. Elon does say that the backs will be hot and radiate a lot of heat! There were discussions about dispersing heat energy, and reflection, etc.What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
- I think there are some misconceptions about the nature of rigid alumina insulation based tiles. They are very fragile. They have the consistency of foam insulation. They have very little strength. Without their protective outer covering, you can poke holes in it with your pinky. If you want to mechanically fasten one you need to embed something in the insulation block to anchor to. That is what you are seeing with the ceramic tubes dangling from the studs. The little spiral fittings would do the same for the small hex tile.
- The ceramic rope Elon mentioned has a different purpose. It is use to insulate between tiles.
- The ceramic rope material, or Nomex felt, could also be used to seal and isolate the underside of the brittle tile from the vehicle.
John
Well I know very little about alumina tiles, other than alumina is refractory and I would suspect breakable like china. However a quick internet search produced this:I thought SX was using much stronger tiles... not Alumina ones! The SX pictures of testing them last year.... left me with the impression of a glazed metallic tile. Elon does say that the backs will be hot and radiate a lot of heat! There were discussions about dispersing heat energy, and reflection, etc.What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
- I think there are some misconceptions about the nature of rigid alumina insulation based tiles. They are very fragile. They have the consistency of foam insulation. They have very little strength. Without their protective outer covering, you can poke holes in it with your pinky. If you want to mechanically fasten one you need to embed something in the insulation block to anchor to. That is what you are seeing with the ceramic tubes dangling from the studs. The little spiral fittings would do the same for the small hex tile.
- The ceramic rope Elon mentioned has a different purpose. It is use to insulate between tiles.
- The ceramic rope material, or Nomex felt, could also be used to seal and isolate the underside of the brittle tile from the vehicle.
John
So I was very surprised to see the tiles apparently broken during the test on SN5 last week!
I expect the vibration is extreme, and maybe the extra stiffening on SN6's skirt will help a number of issues including reducing vibration.... although when the VacRaptors are fixed to the skirt..... !!!!! that will be another story!
I thought SX was using much stronger tiles... not Alumina ones! The SX pictures of testing them last year.... left me with the impression of a glazed metallic tile. Elon does say that the backs will be hot and radiate a lot of heat! There were discussions about dispersing heat energy, and reflection, etc.What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
- I think there are some misconceptions about the nature of rigid alumina insulation based tiles. They are very fragile. They have the consistency of foam insulation. They have very little strength. Without their protective outer covering, you can poke holes in it with your pinky. If you want to mechanically fasten one you need to embed something in the insulation block to anchor to. That is what you are seeing with the ceramic tubes dangling from the studs. The little spiral fittings would do the same for the small hex tile.
- The ceramic rope Elon mentioned has a different purpose. It is use to insulate between tiles.
- The ceramic rope material, or Nomex felt, could also be used to seal and isolate the underside of the brittle tile from the vehicle.
John
So I was very surprised to see the tiles apparently broken during the test on SN5 last week!
I expect the vibration is extreme, and maybe the extra stiffening on SN6's skirt will help a number of issues including reducing vibration.... although when the VacRaptors are fixed to the skirt..... !!!!! that will be another story!
So how serious is the loss of a single tile to Starship? Presumably there are some areas where loss of a tile would be catastrophic, but what percentage? 10%, 50% 90%. How survivable is the loss of 1 tile and how likely is the loss of 1 tile going to lead to the loss of a lot more down wind? Or is this the $64,000 question?
Nobody outside of SpaceX knows for sure, but I think there's a general sense among most observers that loss of any single tile will not lead to the loss of the vehicle.
This isn't like the shuttle where there was aluminum underneath with a low melting temperature. This is stainless steel, with a very high melting temperature. Heating absorbed through one missing tile will be transferred over a wide area of the steel skin.
Relevant video
- 700 heat shield tiles damaged
- 1 tile lost
- survived thanks to a steel plate
An interesting link on thermal rope from old_geez on the discussion thread. It has a wire inside.What’s to say that it’s not a more rigid material encased by the rope? Basically a composite of sorts. The tie offs and fraying at the end to me indicate the ceramic rope while the rigidity of the pieces points toward something rigid.That tweet is 11 months stale. Mary's pic from this afternoon shows something that might be called marshmallowy sandwiched under some of the tiles. Elon was talking about furnace rope or something similar stuffed in the space between tiles.What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
https://twitter.com/elonmusk/status/1171308928476385281 (https://twitter.com/elonmusk/status/1171308928476385281)
Those tubes in my earlier posts are impaled on the studs. Can't see them sealing anything.
Phil
I agree with other posters, wouldn’t you want some sort of compliance between tiles, in addition to underneath with the felt like padding as described by Livingjw?
What’s to say that it’s not a more rigid material encased by the rope? Basically a composite of sorts. The tie offs and fraying at the end to me indicate the ceramic rope while the rigidity of the pieces points toward something rigid.That tweet is 11 months stale. Mary's pic from this afternoon shows something that might be called marshmallowy sandwiched under some of the tiles. Elon was talking about furnace rope or something similar stuffed in the space between tiles.What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
https://twitter.com/elonmusk/status/1171308928476385281 (https://twitter.com/elonmusk/status/1171308928476385281)
Those tubes in my earlier posts are impaled on the studs. Can't see them sealing anything.
Phil
I agree with other posters, wouldn’t you want some sort of compliance between tiles, in addition to underneath with the felt like padding as described by Livingjw?
Replied to this over in the heat shield thread for consistency.It makes me really happy to see the heat shield tile X... the tanks are probably some of the easiest parts of Starship to build, but it's the fine details that have had me a little worried, like the amount of tiles they're going to need to cover the ship, or the connections between the aero surfaces and the body. Seeing the initial results of their (officially labeled) heat shield robot is huge - a few of those robots in a tent could bang out an entire SS heat shield in no time.
tl;dr: The heat shield mounting robot to me is a sign of them entering the "next level" of testing, where (to use the parlance of our times) "**** gets real"
Agree, in fact the test that did placement in a logo, may have actually been a test to design and automate tile placement accurately. They may have just done the logo in CAD/robotic software and just said "go for it".... and this is initial results.
The problem with the discussion above is that Starship has to be ready for immediate reuse >90% of the time. Loss of single tile is not acceptable in that scenario…
The problem with the discussion above is that Starship has to be ready for immediate reuse >90% of the time. Loss of single tile is not acceptable in that scenario…1. Still its not a loss of the ship.
1&2, Agreed. Point 3, however doesn’t work out statistically. With a fleet of 1000 Starships, and an expectation that they should achieve 10 flights without significant refurbishment, and 8000 tiles per Starship, you’d have to have fewer than 1% with any tile issues on any flight, which implies 6 nines average reliability per tile per flight. So the goal has to be essentially perfect tile performance, consistently, or fleet reusability degrades very quickly.The problem with the discussion above is that Starship has to be ready for immediate reuse >90% of the time. Loss of single tile is not acceptable in that scenario…1. Still its not a loss of the ship.
2. We have a ways to go before immediate reuse.
3. Even accepting what you say, how much it violates your standard, is dependent on the frequency and area of tile loss, and severity of heating. If the frequency of such issues is <10% then it fits your target.
I take it for granted that they will strictly not just clip a new tile in place, but the loss will trigger a close inspection, including to somehow assess the level of heat damage to the hull/tank. I assume once any annealing has happened, a section would have to be cut out, as the cold-rolled properties would be lost, so that SS is out of action for a week(s?) or more. However if the properties of the steel are within tolerance (however that can be established?) then its a new tile and off you go.
Why are the tiles black?
An interesting link from old_geez on the prototype discussion thread. That rope has a stainless wire core.What’s to say that it’s not a more rigid material encased by the rope? Basically a composite of sorts. The tie offs and fraying at the end to me indicate the ceramic rope while the rigidity of the pieces points toward something rigid.That tweet is 11 months stale. Mary's pic from this afternoon shows something that might be called marshmallowy sandwiched under some of the tiles. Elon was talking about furnace rope or something similar stuffed in the space between tiles.What purpose?
The white tubes are ceramic fire rope / furnace gasket.
It is more likely that it is a rigid ceramic composite. My guess would be alumina fiber based.
John
I was thinking that if the tubes are soft they would allow some tile float while buffering between the tile and skin.
Phil
https://twitter.com/elonmusk/status/1171308928476385281 (https://twitter.com/elonmusk/status/1171308928476385281)
Those tubes in my earlier posts are impaled on the studs. Can't see them sealing anything.
Phil
I agree with other posters, wouldn’t you want some sort of compliance between tiles, in addition to underneath with the felt like padding as described by Livingjw?
Why are the tiles black?
For high emissivity. They get rid of heat by radiation.
The problem with the discussion above is that Starship has to be ready for immediate reuse >90% of the time. Loss of single tile is not acceptable in that scenario…1. Still its not a loss of the ship.
Odd that they selected three pin arrangement (-Surprised Pikachu), all three pin tiles at SN5 were fractured, but still attached
The problem with the discussion above is that Starship has to be ready for immediate reuse >90% of the time. Loss of single tile is not acceptable in that scenario…1. Still its not a loss of the ship.
Per the video Kazioo posted (thanks!), on Atlantis the missing tile caused burn-though of the steel plate. Only the aluminum under it remained. I have no clue how thick that "steel plate" was, now what steeel it was made of, but unless Starship's hull is thicker (or more resistant) a similar burn-though could result in loss of vehicle; it'd lose all pressure-derived strength if this occurred on the skin of one of the prop tanks.
My hunch is that Space-X might size the tiles small enough that losing one will not result in LOV. (assuming going smaller is possible, and assuming that they have not already done this).
It's good to know that Starship's tiles won't have a foam-and-ice-covered tank or SRBs nearby that might shed material that could impact the tiles, and that it will be steel under the entire tiled area.
I've read some research into materials that are highly reflective in visible and also high-emissivity in IR, but as far as I can tell they aren't common.Why are the tiles black?
For high emissivity. They get rid of heat by radiation.
At 2300 F, only 0.1% of the black body curve energy is emitted in the visible spectrum. Whether it's black in the IR matters, but its reflectivity in the visible spectrum is almost irrelevant (but it has the downside of absorbing more solar radiation).
It's good to know that Starship's tiles won't have a foam-and-ice-covered tank or SRBs nearby that might shed material that could impact the tiles, and that it will be steel under the entire tiled area.
There may still be parts of the upper body flaps that could fall off and impact the fuselage. And all the tiles on those flaps and on the upper fuselage that could fall off and damage the lower flaps, leg covers and fuselage.
Unfortunately Starship won´t be completely impervious to self-inflicted damage during launch...
It's good to know that Starship's tiles won't have a foam-and-ice-covered tank or SRBs nearby that might shed material that could impact the tiles, and that it will be steel under the entire tiled area.
There may still be parts of the upper body flaps that could fall off and impact the fuselage. And all the tiles on those flaps and on the upper fuselage that could fall off and damage the lower flaps, leg covers and fuselage.
Unfortunately Starship won´t be completely impervious to self-inflicted damage during launch...
In that video,The problem with the discussion above is that Starship has to be ready for immediate reuse >90% of the time. Loss of single tile is not acceptable in that scenario…1. Still its not a loss of the ship.
Per the video Kazioo posted (thanks!), on Atlantis the missing tile caused burn-though of the steel plate. Only the aluminum under it remained. I have no clue how thick that "steel plate" was, now what steeel it was made of, but unless Starship's hull is thicker (or more resistant) a similar burn-though could result in loss of vehicle; it'd lose all pressure-derived strength if this occurred on the skin of one of the prop tanks.
My hunch is that Space-X might size the tiles small enough that losing one will not result in LOV. (assuming going smaller is possible, and assuming that they have not already done this).
I've read some research into materials that are highly reflective in visible and also high-emissivity in IR, but as far as I can tell they aren't common.Why are the tiles black?
For high emissivity. They get rid of heat by radiation.
At 2300 F, only 0.1% of the black body curve energy is emitted in the visible spectrum. Whether it's black in the IR matters, but its reflectivity in the visible spectrum is almost irrelevant (but it has the downside of absorbing more solar radiation).
Based on this NASA document, I don't see much correlation. High emissivity is the rule, even among white materials and coatings. Achieving low emissivity is the trick.On orbit it's been the ratio of emissivity to absorbance that's been difficult.
https://ntrs.nasa.gov/citations/19840015630
Well I know very little about alumina tiles, other than alumina is refractory and I would suspect breakable like china. However a quick internet search produced this:Welcome to the world of technical ceramics. :)
https://www.morgantechnicalceramics.com/en-gb/materials/alumina/98-alumina/
I was a little surprised to say the least.
Another point of note alumina is white and I would expect alumina tiles to be white or shades of grey perhaps if something has been added. But SpaceX tiles are black, so either they're not alumina or they're mixed with a lot of secret sauce to make them black. But thinking back the shuttle tiles were black and made out of silica which is also white so what am I missing?
If there is a small amount of pressure induced on the fabric when tiles are attached and torqued, the incompatible expansion and contraction of the tile and tank skin might be mitigated to an acceptable value. Likewise, if there is a "blanket" of a similar material covering the entire region that has had tile mount studs installed, this could possibly provide additional flexibility and insulative properties to help with absorption of vibration and thermal expansion/contraction, and allow for the slight offsets associated with placing flat tiles on convex surfaces. I have to admit that the visual of installing fiberglass batt insulation in my past came to mind.And you'd be right.
In that video,The problem with the discussion above is that Starship has to be ready for immediate reuse >90% of the time. Loss of single tile is not acceptable in that scenario…1. Still its not a loss of the ship.
Per the video Kazioo posted (thanks!), on Atlantis the missing tile caused burn-though of the steel plate. Only the aluminum under it remained. I have no clue how thick that "steel plate" was, now what steeel it was made of, but unless Starship's hull is thicker (or more resistant) a similar burn-though could result in loss of vehicle; it'd lose all pressure-derived strength if this occurred on the skin of one of the prop tanks.
My hunch is that Space-X might size the tiles small enough that losing one will not result in LOV. (assuming going smaller is possible, and assuming that they have not already done this).it was the Alumimium that burned through(Edit you are correct) and it was lucky that there was a steel plate underneath that was in the process of burning through, but "luckily" had not succumbed by the time they got through reentry. It was the steel and the luck that the missing tile was just there that saved them.
However that only reduces but does not negate your argument.
The reentry profile of Shuttle and Starship are totally different. I don't think the shuttle "skydived" at about 90 degrees to the apparent airflow, like the Starship is planning to. If I remember rightly, argument on this site was the broard smooth cylinder of the Starship, will create a shock wave some metres off of the surface where much of the heating will take place. The smooth cylindrical shape will present less "hot spots" than the wings etc of the Shuttle. However comes the reply, the Starship has flippers/dragerons/whatever sticking out. I suggest these are less of a risk than the shuttle's wings etc, as if there is heat damage or burn through, that of itself will not cause an immediate breakup of the vehicle, as they are separate add-ons and not part of the main pressure vessel. They could cause a lack of controll or uncontrollable roll etc, but with their function as a big airbrake, I would guess they could be badly damaged befor the ship was doomed. A burn through on the shuttle wing risked fast colabse of the aluminium structure of the wing, asymmetric force on the two wins, uncontrollable spin and immediate breakup. (my interpretation)
Edit: I watched it gain, yes you are right, it had got through the steel plate and was "working on the Aluminium underneath" So yes steel is vulnerable. However I won't change my whole comment, as the "re-entry profile" is all still relevant.
What is the primary driver for the tile size? I.e. why not bigger?
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What is the primary driver for the tile size? I.e. why not bigger?
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Curvature is probably one reason. It'll be interesting to see how it looks when they start tiling the nosecone where you get curvature in two dimensions.
Odd that they selected three pin arrangement (-Surprised Pikachu), all three pin tiles at SN5 were fractured, but still attached
The three-pin arrangement assures three-sided symmetry of the tile which simplifies the production process a lot: the tiles basically have no fixed orientation but can be turned "any way you may wish".
What is the primary driver for the tile size? I.e. why not bigger?
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Curvature is probably one reason. It'll be interesting to see how it looks when they start tiling the nosecone where you get curvature in two dimensions.
Is not possible to create curved tiles?
What is the primary driver for the tile size? I.e. why not bigger?
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Curvature is probably one reason. It'll be interesting to see how it looks when they start tiling the nosecone where you get curvature in two dimensions.
Is not possible to create curved tiles?
Possible; but expensive. Why waste resources making many specialist tile types when you can get good at making a minimal number of tile types over and over again as cheaply as possible? Sticking to only two or three types expedites manufacturing and repair, not to mention reducing overhead costs. That's not to say there won't be any curved tiles. I personally just expect a minimum of different types where possible.
Anyway, the smaller the standard hex tile is, the tighter the curvature that can be conformed to without needing specialist curved tiles. There's probably some sort of efficiency maxima in there where the tiles are small enough that the most development and production resources are saved while also large enough as to be sturdy against vibration/expansion and not have too much weight in mounting brackets/take too long to install.
That's got the reverse problem- the chance of instalation error because you didnt notice which way the tile is curved.What is the primary driver for the tile size? I.e. why not bigger?
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Curvature is probably one reason. It'll be interesting to see how it looks when they start tiling the nosecone where you get curvature in two dimensions.
Is not possible to create curved tiles?
Possible; but expensive. Why waste resources making many specialist tile types when you can get good at making a minimal number of tile types over and over again as cheaply as possible? Sticking to only two or three types expedites manufacturing and repair, not to mention reducing overhead costs. That's not to say there won't be any curved tiles. I personally just expect a minimum of different types where possible.
Anyway, the smaller the standard hex tile is, the tighter the curvature that can be conformed to without needing specialist curved tiles. There's probably some sort of efficiency maxima in there where the tiles are small enough that the most development and production resources are saved while also large enough as to be sturdy against vibration/expansion and not have too much weight in mounting brackets/take too long to install.
You only need one curved tile type for the main cylinder, and can still use a hex tile for nose. So that is two tile types. I don't think any of your reasoning applies here.
I don't think that's correct - see the link at the top of the first page of this thread for a diagram. As the diameter of the ship narrows in the nose the hexagons will start to overlap. Each ring of tiles or at least every few rings will need to have a specific shape, you can't use the same tessellated hexagons all the way.What is the primary driver for the tile size? I.e. why not bigger?
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Curvature is probably one reason. It'll be interesting to see how it looks when they start tiling the nosecone where you get curvature in two dimensions.
Is not possible to create curved tiles?
Possible; but expensive. Why waste resources making many specialist tile types when you can get good at making a minimal number of tile types over and over again as cheaply as possible? Sticking to only two or three types expedites manufacturing and repair, not to mention reducing overhead costs. That's not to say there won't be any curved tiles. I personally just expect a minimum of different types where possible.
Anyway, the smaller the standard hex tile is, the tighter the curvature that can be conformed to without needing specialist curved tiles. There's probably some sort of efficiency maxima in there where the tiles are small enough that the most development and production resources are saved while also large enough as to be sturdy against vibration/expansion and not have too much weight in mounting brackets/take too long to install.
You only need one curved tile type for the main cylinder, and can still use a hex tile for nose. So that is two tile types. I don't think any of your reasoning applies here.
That's got the reverse problem- the chance of instalation error because you didnt notice which way the tile is curved.
I don't think that's correct - see the link at the top of the first page of this thread for a diagram. As the diameter of the ship narrows in the nose the hexagons will start to overlap. Each ring of tiles or at least every few rings will need to have a specific shape, you can't use the same tessellated hexagons all the way.
The nature and form of the "rope" insulation:Since this is still being discussed in detail, I am re-posting my suggestion, with an ADDED diagram.... The "E" is now only conceptual and not very obvious, but the principle is there still.
Because a vast quantity of this type of product will be used, SX can design it in a form that best suits the SS. Its current cheapness, standard shape, size, quality and utility, are no longer important, if SX needs a quantity that will allow easy and cheap mass-production of their design.
The pieces we have seen on SN5 look as if (some of them) were anchored on the studs.... which is odd as the picture of the "X" of tiles on SN6 appears to show them trapped aligned under the tile edges.
Other options:
A large or continuous sheet covering all/most of the tiled surface. Cons: weight? spread of tiles being ripped off! PROs: easy, anchored on all pins, protects hull evenly from radited heat as well as plasma, may cushion vibration, stops plasma path to hull however it gets behind a tile.
Formed into"Y" sections, for one vertex meeting point, (or several "Y"'s at once). In manufacture a thin sheet could be cut and folded so that "unwanted" material from the centre of each tile is used to thicken the area behind the tile joints. The arms of the "Y" are wide enough to impale (into pre-formed holes) onto the tile mounting pins. PRO's. Same "weight" (or thinner) material provides much better cushion and insulation at the tile gaps. Three fixed points for each "Y" provide reliable anchoring.
Moulded into "U" cross section. If the tile edges turn back towards the hull as if folded, then a "U" cross-sectioned fibre pad can "contain" two adjacent edges, and even have a tongue that separates them.... now it is an "E" with each gap (in the "E") containing one tile edge! PRO's This allows damping of vibration of tiles, removal of contact/impact between tiles, and a complex and so secure obstruction of all plasma paths.
I don't know how these could be made, whether layers of fabric would be built up, and sewn, or whether fibres could be blown and compressed into a mould.... Whether it needs any stainless wire stiffening etc. But although it has gone from "off the shelf" rope to a carefully designed manufactured product, it could be very cost effective if it is:
1. very secure and naturally stable in its location,
2. saves tile damage through tile vibration, and contact with adjacent tiles.
3. provides an excellent secure barrier to any plasma or hot gas ingress between tile gaps - or even between adjacent tiles!
4. if it can additionally reduce the risk of single tile loss spreading by frustrating the airflow's path under the next tile then it could be an outstanding solution.
Edit: The "E" version may safely allow slightly wider tile gaps, and more tolerance for fitting the tiles because it so thoroughly protects the gaps.
Folks have talked about resonances and flight / temperature flexing, but I've not seen a single post about the obvious elephant in the room...So some kind of spring grip/clip to attach the tile to each mounting pin, and a moulded ceramic fibre "gasket" as I describe in my post just above. There is room for more slack/tolerance if the gasket is engineered to fit the gap. It will have the necessary give.
All one has to do is to simply look at one of these full up SN[x] tank section to see the issue - without internal pressure, the cylinder is loaded with deformations, and deformations that aren't steady state. How will the tiles, and associated inter-tile fillers, deal with all this natural deformation? I doubt the expectation will be that it will always be pressurized - from before tile installation on. But perhaps? A stiff five ring stack is one thing, but a full up tank section, let along the payload area, is a completely different issue...
... but I've not seen a single post about the obvious elephant in the room...What about ice? Not problem with Shuttle orbiter but with X-33 and SS.
Ahhh, now I see what you were getting at. Not so different than what I was getting at about a recess under the edge of the tiles.The nature and form of the "rope" insulation:Since this is still being discussed in detail, I am re-posting my suggestion, with an ADDED diagram.... The "E" is now only conceptual and not very obvious, but the principle is there still.
Because a vast quantity of this type of product will be used, SX can design it in a form that best suits the SS. Its current cheapness, standard shape, size, quality and utility, are no longer important, if SX needs a quantity that will allow easy and cheap mass-production of their design.
The pieces we have seen on SN5 look as if (some of them) were anchored on the studs.... which is odd as the picture of the "X" of tiles on SN6 appears to show them trapped aligned under the tile edges.
Other options:
A large or continuous sheet covering all/most of the tiled surface. Cons: weight? spread of tiles being ripped off! PROs: easy, anchored on all pins, protects hull evenly from radited heat as well as plasma, may cushion vibration, stops plasma path to hull however it gets behind a tile.
Formed into"Y" sections, for one vertex meeting point, (or several "Y"'s at once). In manufacture a thin sheet could be cut and folded so that "unwanted" material from the centre of each tile is used to thicken the area behind the tile joints. The arms of the "Y" are wide enough to impale (into pre-formed holes) onto the tile mounting pins. PRO's. Same "weight" (or thinner) material provides much better cushion and insulation at the tile gaps. Three fixed points for each "Y" provide reliable anchoring.
Moulded into "U" cross section. If the tile edges turn back towards the hull as if folded, then a "U" cross-sectioned fibre pad can "contain" two adjacent edges, and even have a tongue that separates them.... now it is an "E" with each gap (in the "E") containing one tile edge! PRO's This allows damping of vibration of tiles, removal of contact/impact between tiles, and a complex and so secure obstruction of all plasma paths.
I don't know how these could be made, whether layers of fabric would be built up, and sewn, or whether fibres could be blown and compressed into a mould.... Whether it needs any stainless wire stiffening etc. But although it has gone from "off the shelf" rope to a carefully designed manufactured product, it could be very cost effective if it is:
1. very secure and naturally stable in its location,
2. saves tile damage through tile vibration, and contact with adjacent tiles.
3. provides an excellent secure barrier to any plasma or hot gas ingress between tile gaps - or even between adjacent tiles!
4. if it can additionally reduce the risk of single tile loss spreading by frustrating the airflow's path under the next tile then it could be an outstanding solution.
Edit: The "E" version may safely allow slightly wider tile gaps, and more tolerance for fitting the tiles because it so thoroughly protects the gaps.
I have shown a version that only covers one "Y", but obviously a larger "gasket" covering several would mean less joins, faster installation, and anchoring on more pins.
Assuming there is some slack in the mounting on the pins, maybe a spring clip, my gasket could help keep adjoining surfaces flush,and the gaps even.
PS anyone recommend a free CAD program.... I have looked and tried, but never found!!!!
Ahhh, now I see what you were getting at. Not so different than what I was getting at about a recess under the edge of the tiles.Crikey glancing back now my original writing is almost unintelligible .... almost like a patent specification!!!
What is the primary driver for the tile size? I.e. why not bigger?
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Curvature is probably one reason. It'll be interesting to see how it looks when they start tiling the nosecone where you get curvature in two dimensions.
Is not possible to create curved tiles?
Possible; but expensive. Why waste resources making many specialist tile types when you can get good at making a minimal number of tile types over and over again as cheaply as possible? Sticking to only two or three types expedites manufacturing and repair, not to mention reducing overhead costs. That's not to say there won't be any curved tiles. I personally just expect a minimum of different types where possible.
Anyway, the smaller the standard hex tile is, the tighter the curvature that can be conformed to without needing specialist curved tiles. There's probably some sort of efficiency maxima in there where the tiles are small enough that the most development and production resources are saved while also large enough as to be sturdy against vibration/expansion and not have too much weight in mounting brackets/take too long to install.
You only need one curved tile type for the main cylinder, and can still use a hex tile for nose. So that is two tile types. I don't think any of your reasoning applies here.
It helps if you think of this like the techniques of computer graphics where the shapes are composed of polygons.What is the primary driver for the tile size? I.e. why not bigger?
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Curvature is probably one reason. It'll be interesting to see how it looks when they start tiling the nosecone where you get curvature in two dimensions.
Is not possible to create curved tiles?
Possible; but expensive. Why waste resources making many specialist tile types when you can get good at making a minimal number of tile types over and over again as cheaply as possible? Sticking to only two or three types expedites manufacturing and repair, not to mention reducing overhead costs. That's not to say there won't be any curved tiles. I personally just expect a minimum of different types where possible.
Anyway, the smaller the standard hex tile is, the tighter the curvature that can be conformed to without needing specialist curved tiles. There's probably some sort of efficiency maxima in there where the tiles are small enough that the most development and production resources are saved while also large enough as to be sturdy against vibration/expansion and not have too much weight in mounting brackets/take too long to install.
You only need one curved tile type for the main cylinder, and can still use a hex tile for nose. So that is two tile types. I don't think any of your reasoning applies here.
You don't think there's weird curvature where the tanks meet the chines, between the chines and the aero surfaces, the edges of the chines, edges of the aero surfaces, possibly inside the hinges of the aero surfaces, where the fairing reduces in diameter, surrounding RCS ports, and covering the nose? There's going to have to be some specialization in tile shape.
There may or may not be curved tiles. My point is that a single tile however curved cannot cover the whole vehicle. I think we all agree that there will be special cases like the moving surfaces, I’m not considering those, I’m talking about the main body of Starship. The cylinder can be covered with a single type of tile, but the nose section can't. Each specific radii of the nose will require its own tile type regardless because the curvature is different and the radius is different as well. This doesn’t mean thousands of tile types, but it probably does mean many dozens.I don't think that's correct - see the link at the top of the first page of this thread for a diagram. As the diameter of the ship narrows in the nose the hexagons will start to overlap. Each ring of tiles or at least every few rings will need to have a specific shape, you can't use the same tessellated hexagons all the way.
I agree, it's not my idea to use a hex tile. I would have a range of curved tiles for the nose. But apparently SpaceX logistics can't handle more than one type of tile?!
I was expecting a technical reason, like the tiles are cast in large flat sheets and then machined into sections. But I think the Shuttle tiles were cast. If so, then it should be eminently feasible to cast curved tiles. Being a regular solid, the SS/SH can be tiled with a relatively small of tile shapes. Obviously, curved tiles fit a curved surface better.
And to head off another lame objection, no, I am not suggesting a huge range of unique tile shapes like the shuttle used.
Seeing as Elon thinks like an engineer, I would expect to see some curved tiles in future iterations.
Cad program? Try Onshape. Free for hobbyists.TY am following up OnShape.
https://www.onshape.com/products/free?hsCtaTracking=12ef09fd-fa65-48a5-a496-d17c85a4662a%7C7bfa3811-7cbc-49db-9c26-50fb7bd007cd (https://www.onshape.com/products/free?hsCtaTracking=12ef09fd-fa65-48a5-a496-d17c85a4662a%7C7bfa3811-7cbc-49db-9c26-50fb7bd007cd)
My thoughts with the Ceramic rope were similar to how it’s used in reactor vessels. Simply packed in between the tiles. Usually three+ rows.
Given the hex tile layout, alternate rows could take different directions, ensuring no gaps at rope ends.
Just read the whole thread because you're arguing over and over about whether 2+2 is 4 or 5I have read the whole thread. I started it.
It helps if you think of this like the techniques of computer graphics where the shapes are composed of polygons.What is the primary driver for the tile size? I.e. why not bigger?
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Curvature is probably one reason. It'll be interesting to see how it looks when they start tiling the nosecone where you get curvature in two dimensions.
Is not possible to create curved tiles?
Possible; but expensive. Why waste resources making many specialist tile types when you can get good at making a minimal number of tile types over and over again as cheaply as possible? Sticking to only two or three types expedites manufacturing and repair, not to mention reducing overhead costs. That's not to say there won't be any curved tiles. I personally just expect a minimum of different types where possible.
Anyway, the smaller the standard hex tile is, the tighter the curvature that can be conformed to without needing specialist curved tiles. There's probably some sort of efficiency maxima in there where the tiles are small enough that the most development and production resources are saved while also large enough as to be sturdy against vibration/expansion and not have too much weight in mounting brackets/take too long to install.
You only need one curved tile type for the main cylinder, and can still use a hex tile for nose. So that is two tile types. I don't think any of your reasoning applies here.
You don't think there's weird curvature where the tanks meet the chines, between the chines and the aero surfaces, the edges of the chines, edges of the aero surfaces, possibly inside the hinges of the aero surfaces, where the fairing reduces in diameter, surrounding RCS ports, and covering the nose? There's going to have to be some specialization in tile shape.
So you want a shape that can fit with copies of itself (IE a Platonic shape). You want a minimum number of different sizes and a minimum number of different mounting layouts for them to hang off.
Figuring out a good size for these tiles (big enough to cover maximum area, small enough to cover the common level of curvature of most of the hull) is the sort of task computer simulations were made for.
and you are the one that explains to everyone over and over that 2+2 is equal to 4 ;)Just read the whole thread because you're arguing over and over about whether 2+2 is 4 or 5I have read the whole thread. I started it.
Hurrah if everyone agrees than good, just seemed to me that someone was suggesting otherwise. I will let it drop.and you are the one that explains to everyone over and over that 2+2 is equal to 4 ;)Just read the whole thread because you're arguing over and over about whether 2+2 is 4 or 5I have read the whole thread. I started it.
....
The reentry profile of Shuttle and Starship are totally different. I don't think the shuttle "skydived" at about 90 degrees to the apparent airflow, like the Starship is planning to....
What is the primary driver for the tile size? I.e. why not bigger?
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Curvature is probably one reason. It'll be interesting to see how it looks when they start tiling the nosecone where you get curvature in two dimensions.
Is not possible to create curved tiles?
...
Edit: I watched it gain, yes you are right, it had got through the steel plate and was "working on the Aluminium underneath" So yes steel is vulnerable. However I won't change my whole comment, as the "re-entry profile" is all still relevant.
Folks have talked about resonances and flight / temperature flexing, but I've not seen a single post about the obvious elephant in the room...
All one has to do is to simply look at one of these full up SN[x] tank section to see the issue - without internal pressure, the cylinder is loaded with deformations, and deformations that aren't steady state. How will the tiles, and associated inter-tile fillers, deal with all this natural deformation? I doubt the expectation will be that it will always be pressurized - from before tile installation on. But perhaps? A stiff five ring stack is one thing, but a full up tank section, let along the payload area, is a completely different issue...
True.Is not possible to create curved tiles?
It is possible. After molding they can be machined very easily.
John
Your gut is probably right.
Polygonal extruded prisms aren't the only shape that exist. However, I admittedly have no clue how these tiles are manufactured. Maybe it's extremely hard to do anything but a flat two-dimensional sandwich. But maybe it's case that they could be manufactured with compound curves, splines, smooth swept/lofted geometry etc. You are certainly right in that computational methods are a major driving force though.
Not only is the space of what is easy/hard/expensive/effective to manufacture with TUFROC-based TPS tiles a problem of far too many dimensions for me to understand, but also most of those dimensions are problems of design and manufacture in which I have no experience or knowledge. All I'm sure of is that adherence to the KISS principle is king here. Are there going to be a thousand unique types of differently shaped tile like with STS? Of course not. Are there only going to be two types of which both are two different sizes of flat hexagonal prism? My gut says no.
The suggestion, in the physicality of the thing, re the sharp edges, is that the thermal stressing on the sharper edges.. would likely have to fit within a stressing envelope of some kind, whereas there may be a few more degrees of wiggle room in a more rounded tile and shape application.
That the sharp edged thingamabob rocket shape and tile/etc application, has a subtle but potentially critical caveat in it's equation, when compared to the more rounded and/or aerodynamic shapes.
This, of course, indicates neither good nor bad in the weighting of either shape or application, as the overall scenario is more complex than that singular aspect.
Ie, that one can just hang that sharp edged tile out there to burn, while the underlying structure is more robust and less stressed mechanically and thermally due to construction and intent..and so on. All things in the comparison being unequal, etc.
I'm partially interested in the subject as one of my inventions was a new and untested form of highly manipulable low cost ceramic nanopowder composite oxide creation. I know the process works perfectly but it has yet to be applied to ceramic nanopowder compositions. Empirical and done/tested/produced, not theoretical.
Any morphology, any composite, any particle size. Just dial the process in...and away you go....no more complex than squeezing out pasta.
One could probably even make it out as a hard formed porous buckling isolator, which ultimately could act a bit like a thermal diode. Lots of free toys hiding inside...
Hmmm. So stagnation won't be a line up the middle but a point a bit above where the nosecone starts curving.
....
The reentry profile of Shuttle and Starship are totally different. I don't think the shuttle "skydived" at about 90 degrees to the apparent airflow, like the Starship is planning to....
During the hottest parts of the reentry, Starship will want to be producing lift and will probably be closer to 50 degrees AoA. This is not much higher than the Shuttle's maximum which I believe was about 45 degrees.
John
OTOH, Rockwell didn't have additive manufacturing. If inspection on Mars shows a bad tile, a replacement need only be good enough for one EDL. In US army aviation parlance of back in the day, a red X (grounded) log entry becomes a circled red X (one time flight only). Conceivably a substitute tile might even be ablative.True.Is not possible to create curved tiles?
It is possible. After molding they can be machined very easily.
John
But unwise. :(
NA Rockwell Manufacturing division were very proud that the had manage to make c24 000 nearly all unique in thickness and top surface profile.
It was a massive PITA because if a tile was damaged it had to be machined exactly to shape, and if black then have the surface coat added and baked on.
Later Boeing devised a near net shape process using slip casting onto a fairly easily made porous former which could (not sure if it was used) permit bigger blocks (less stress in firing) and lower machining.
Now, think about how much hardware you're going to need on mars to do repairs this way.
This is where interchangability really pays off.
The suggestion, in the physicality of the thing, re the sharp edges, is that the thermal stressing on the sharper edges.. would likely have to fit within a stressing envelope of some kind, whereas there may be a few more degrees of wiggle room in a more rounded tile and shape application.Hmmm. I read this after my post about additive manufacturing. You obviously have some trade secrets so just tell me to butt out and no hard feeling.
That the sharp edged thingamabob rocket shape and tile/etc application, has a subtle but potentially critical caveat in it's equation, when compared to the more rounded and/or aerodynamic shapes.
This, of course, indicates neither good nor bad in the weighting of either shape or application, as the overall scenario is more complex than that singular aspect.
Ie, that one can just hang that sharp edged tile out there to burn, while the underlying structure is more robust and less stressed mechanically and thermally due to construction and intent..and so on. All things in the comparison being unequal, etc.
I'm partially interested in the subject as one of my inventions was a new and untested form of highly manipulable low cost ceramic nanopowder composite oxide creation. I know the process works perfectly but it has yet to be applied to ceramic nanopowder compositions. Empirical and done/tested/produced, not theoretical.
Any morphology, any composite, any particle size. Just dial the process in...and away you go....no more complex than squeezing out pasta.
One could probably even make it out as a hard formed porous buckling isolator, which ultimately could act a bit like a thermal diode. Lots of free toys hiding inside...
The shuttle used carbon carbon on the leading edges. Maybe the flaps edges will be carbon carbon. I think they were close to one long piece on the shuttle.
Are ice impacts possible at SS? Quick comparison for dimensions for STS says yes, but:The shuttle used carbon carbon on the leading edges. Maybe the flaps edges will be carbon carbon. I think they were close to one long piece on the shuttle.
And the failure of that leading-edge reinforced carbon carbon after a foam strike is what doomed Columbia.
The shuttle used carbon carbon on the leading edges. Maybe the flaps edges will be carbon carbon. I think they were close to one long piece on the shuttle.
The suggestion, in the physicality of the thing, re the sharp edges, is that the thermal stressing on the sharper edges.. would likely have to fit within a stressing envelope of some kind, whereas there may be a few more degrees of wiggle room in a more rounded tile and shape application.Are you trolling us KBK?
That the sharp edged thingamabob rocket shape and tile/etc application, has a subtle but potentially critical caveat in it's equation, when compared to the more rounded and/or aerodynamic shapes.
This, of course, indicates neither good nor bad in the weighting of either shape or application, as the overall scenario is more complex than that singular aspect.
Ie, that one can just hang that sharp edged tile out there to burn, while the underlying structure is more robust and less stressed mechanically and thermally due to construction and intent..and so on. All things in the comparison being unequal, etc.
I'm partially interested in the subject as one of my inventions was a new and untested form of highly manipulable low cost ceramic nanopowder composite oxide creation. I know the process works perfectly but it has yet to be applied to ceramic nanopowder compositions. Empirical and done/tested/produced, not theoretical.
Any morphology, any composite, any particle size. Just dial the process in...and away you go....no more complex than squeezing out pasta.
One could probably even make it out as a hard formed porous buckling isolator, which ultimately could act a bit like a thermal diode. Lots of free toys hiding inside...
Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Intersting - OK, here's a follow up question: Obviously (I think ...) aero-capture from an interplanetary trajectory to elliptical capture orbit, should be somewhat less demanding that direct EDL from the same interplanetary trajectory, but how much less? I sometimes see discussion of perhaps using aero-capture followed by multiple aero-braking passes prior to EDL in cases where direct EDL would exceed the vehicle survival envelope, but unless aero-capture is substantially less demanding that direct EDL, there might not be much of a point.Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Aero BREAKING can be arbitrarally low stress, but aero CAPTURE from an interplanetary trajectory to eliptiical capture orbit, is usually more stressful than a LEO entry. You only have once chance to slow down, so you have to be aggressive, going deep while still fast enough to go flying out past the moon again.
I know enough to know there is a mathematical answer to your question, but my credentials come from Kerbal Space Program, so even if I could come up with numbers, I wouldn't trust them with a real-world scenario.Intersting - OK, here's a follow up question: Obviously (I think ...) aero-capture from an interplanetary trajectory to elliptical capture orbit, should be somewhat less demanding that direct EDL from the same interplanetary trajectory, but how much less? I sometimes see discussion of perhaps using aero-capture followed by multiple aero-braking passes prior to EDL in cases where direct EDL would exceed the vehicle survival envelope, but unless aero-capture is substantially less demanding that direct EDL, there might not be much of a point.Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Aero BREAKING can be arbitrarally low stress, but aero CAPTURE from an interplanetary trajectory to eliptiical capture orbit, is usually more stressful than a LEO entry. You only have once chance to slow down, so you have to be aggressive, going deep while still fast enough to go flying out past the moon again.
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....As is the case a lot of the time "It depends."
there's is a minimum force trajectory that will just capture, but at earth you'll have already transited the Van Allen belts by the time you hit the atmosphere. So I think mission planers will probably want to drop below the belts in the first pass, which is pretty aggressive. Might as well just go straight to EDL at that point.Intersting - OK, here's a follow up question: Obviously (I think ...) aero-capture from an interplanetary trajectory to elliptical capture orbit, should be somewhat less demanding that direct EDL from the same interplanetary trajectory, but how much less? I sometimes see discussion of perhaps using aero-capture followed by multiple aero-braking passes prior to EDL in cases where direct EDL would exceed the vehicle survival envelope, but unless aero-capture is substantially less demanding that direct EDL, there might not be much of a point.Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Aero BREAKING can be arbitrarally low stress, but aero CAPTURE from an interplanetary trajectory to eliptiical capture orbit, is usually more stressful than a LEO entry. You only have once chance to slow down, so you have to be aggressive, going deep while still fast enough to go flying out past the moon again.
there's is a minimum force trajectory that will just capture, but at earth you'll have already transited the Van Allen belts by the time you hit the atmosphere. So I think mission planers will probably want to drop below the belts in the first pass, which is pretty aggressive. Might as well just go straight to EDL at that point.Intersting - OK, here's a follow up question: Obviously (I think ...) aero-capture from an interplanetary trajectory to elliptical capture orbit, should be somewhat less demanding that direct EDL from the same interplanetary trajectory, but how much less? I sometimes see discussion of perhaps using aero-capture followed by multiple aero-braking passes prior to EDL in cases where direct EDL would exceed the vehicle survival envelope, but unless aero-capture is substantially less demanding that direct EDL, there might not be much of a point.Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Aero BREAKING can be arbitrarally low stress, but aero CAPTURE from an interplanetary trajectory to eliptiical capture orbit, is usually more stressful than a LEO entry. You only have once chance to slow down, so you have to be aggressive, going deep while still fast enough to go flying out past the moon again.
granted, like Apollo. But that only helps with direct entry. if you're doing multiple passes sooner or later you end up in the belts.there's is a minimum force trajectory that will just capture, but at earth you'll have already transited the Van Allen belts by the time you hit the atmosphere. So I think mission planers will probably want to drop below the belts in the first pass, which is pretty aggressive. Might as well just go straight to EDL at that point.Intersting - OK, here's a follow up question: Obviously (I think ...) aero-capture from an interplanetary trajectory to elliptical capture orbit, should be somewhat less demanding that direct EDL from the same interplanetary trajectory, but how much less? I sometimes see discussion of perhaps using aero-capture followed by multiple aero-braking passes prior to EDL in cases where direct EDL would exceed the vehicle survival envelope, but unless aero-capture is substantially less demanding that direct EDL, there might not be much of a point.Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Aero BREAKING can be arbitrarally low stress, but aero CAPTURE from an interplanetary trajectory to eliptiical capture orbit, is usually more stressful than a LEO entry. You only have once chance to slow down, so you have to be aggressive, going deep while still fast enough to go flying out past the moon again.
Remember that when coming from an interplanetary trajectory, they can choose any inclination they want essentially for free, with the restriction that perigee be roughly over the ecliptic. (This has ramifications depending on what season it is when you're coming back) So if you approach in a polar inclination, you may well be able to go around over the top of the belts and avoid most of the radiation.
Some rough numbers: LEO reentry is ~7.8 km/s and lunar reentry ~11 km/s (just below escape velocity). Squaring these numbers you get 61 and 121 (representing kinetic energy per unit mass). So a good rule of thumb is that lunar reentry needs to get rid of twice the energy. Anything interplanetary is going to have even more energy.Intersting - OK, here's a follow up question: Obviously (I think ...) aero-capture from an interplanetary trajectory to elliptical capture orbit, should be somewhat less demanding that direct EDL from the same interplanetary trajectory, but how much less? I sometimes see discussion of perhaps using aero-capture followed by multiple aero-braking passes prior to EDL in cases where direct EDL would exceed the vehicle survival envelope, but unless aero-capture is substantially less demanding that direct EDL, there might not be much of a point.Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Aero BREAKING can be arbitrarally low stress, but aero CAPTURE from an interplanetary trajectory to eliptiical capture orbit, is usually more stressful than a LEO entry. You only have once chance to slow down, so you have to be aggressive, going deep while still fast enough to go flying out past the moon again.
Some rough numbers: LEO reentry is ~7.8 km/s and lunar reentry ~11 km/s (just below escape velocity). Squaring these numbers you get 61 and 121 (representing kinetic energy per unit mass). So a good rule of thumb is that lunar reentry needs to get rid of twice the energy. Anything interplanetary is going to have even more energy.Intersting - OK, here's a follow up question: Obviously (I think ...) aero-capture from an interplanetary trajectory to elliptical capture orbit, should be somewhat less demanding that direct EDL from the same interplanetary trajectory, but how much less? I sometimes see discussion of perhaps using aero-capture followed by multiple aero-braking passes prior to EDL in cases where direct EDL would exceed the vehicle survival envelope, but unless aero-capture is substantially less demanding that direct EDL, there might not be much of a point.Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Aero BREAKING can be arbitrarally low stress, but aero CAPTURE from an interplanetary trajectory to eliptiical capture orbit, is usually more stressful than a LEO entry. You only have once chance to slow down, so you have to be aggressive, going deep while still fast enough to go flying out past the moon again.
So from a simplistic energy viewpoint a reusable TPS capable of LEO reentry can do a lunar reentry by getting rid of half the energy in a first pass, cooling of during an intermediate elliptical orbit and then doing a standard reentry. This approach could extend to interplanetary reentries up to ~13.5 km/s by splitting it in three.
This does of course not work in real life due to the maximum temperature limitations of the TPS and the fact that the plasma temperature increases rapidly with velocity. It is possible to decrease the temperature by staying at a higher altitude but the drag decreases rapidly and it is already hard to slow down enough during a single pass.
Starship should be able to reenter from the Moon but the question is how many passes will be required - if the TPS is just good enough for LEO (like the Space Shuttle) then it might take a relatively long time and, as mentioned previously, lead to excessive radiation exposure. The higher the maximum temperature of the TPS, the lower the ballistic coefficient and the higher the lift to drag ratio (to stay longer at the optimal altitude) the better.
For interplanetary trajectories the hard limit is indeed if you can get below escape velocity on the first pass. I am quite curios about the capabilities (on paper) of their current TPS designs, especially with regard to the faster return trajectories they would like to do.
I'm curious to know if a fully-fueled SS returning to Earth orbit would need aero braking maneuvers at all. If there are in-orbit refueling capabilities at both Mars and Earth, then sufficient propellants for both acceleration and deceleration in both directions would set up the easiest possible re-entry conditions. Am I being a dumbass here? ;D
granted, like Apollo. But that only helps with direct entry. if you're doing multiple passes sooner or later you end up in the belts.there's is a minimum force trajectory that will just capture, but at earth you'll have already transited the Van Allen belts by the time you hit the atmosphere. So I think mission planers will probably want to drop below the belts in the first pass, which is pretty aggressive. Might as well just go straight to EDL at that point.Intersting - OK, here's a follow up question: Obviously (I think ...) aero-capture from an interplanetary trajectory to elliptical capture orbit, should be somewhat less demanding that direct EDL from the same interplanetary trajectory, but how much less? I sometimes see discussion of perhaps using aero-capture followed by multiple aero-braking passes prior to EDL in cases where direct EDL would exceed the vehicle survival envelope, but unless aero-capture is substantially less demanding that direct EDL, there might not be much of a point.Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Aero BREAKING can be arbitrarally low stress, but aero CAPTURE from an interplanetary trajectory to eliptiical capture orbit, is usually more stressful than a LEO entry. You only have once chance to slow down, so you have to be aggressive, going deep while still fast enough to go flying out past the moon again.
Remember that when coming from an interplanetary trajectory, they can choose any inclination they want essentially for free, with the restriction that perigee be roughly over the ecliptic. (This has ramifications depending on what season it is when you're coming back) So if you approach in a polar inclination, you may well be able to go around over the top of the belts and avoid most of the radiation.
granted, like Apollo. But that only helps with direct entry. if you're doing multiple passes sooner or later you end up in the belts.there's is a minimum force trajectory that will just capture, but at earth you'll have already transited the Van Allen belts by the time you hit the atmosphere. So I think mission planers will probably want to drop below the belts in the first pass, which is pretty aggressive. Might as well just go straight to EDL at that point.Intersting - OK, here's a follow up question: Obviously (I think ...) aero-capture from an interplanetary trajectory to elliptical capture orbit, should be somewhat less demanding that direct EDL from the same interplanetary trajectory, but how much less? I sometimes see discussion of perhaps using aero-capture followed by multiple aero-braking passes prior to EDL in cases where direct EDL would exceed the vehicle survival envelope, but unless aero-capture is substantially less demanding that direct EDL, there might not be much of a point.Sorry don't know if this is the best place for this question, but here goes:
Is there a generally accepted comparison between the heat shield requirements of re-entry from LEO and those of aero-capture from e.g. lunar or martian TEI?
Gut says aero-capture should be much less stressing (thermally, structurally, etc.) than full re-entry. But IANARS....
Aero BREAKING can be arbitrarally low stress, but aero CAPTURE from an interplanetary trajectory to eliptiical capture orbit, is usually more stressful than a LEO entry. You only have once chance to slow down, so you have to be aggressive, going deep while still fast enough to go flying out past the moon again.
Remember that when coming from an interplanetary trajectory, they can choose any inclination they want essentially for free, with the restriction that perigee be roughly over the ecliptic. (This has ramifications depending on what season it is when you're coming back) So if you approach in a polar inclination, you may well be able to go around over the top of the belts and avoid most of the radiation.
Sorry, but clearly it doesn't only help with direct entry. Depends on how big each pass is, an aerobraking trajectory can bypass the belts almost entirely using this technique.
I'm curious to know if a fully-fueled SS returning to Earth orbit would need aero braking maneuvers at all.That's a big if for mars given it takes 4 additional flights to load an SS with prop.
If there are in-orbit refueling capabilities at both Mars and Earth,
then sufficient propellants for both acceleration and deceleration in both directions would set up the easiest possible re-entry conditions. Am I being a dumbass here? ;DNo. the KISS principle suggests early flights will keep the trajectory as simple as possible.
Sorry if this has already been discussed and I missed it. My biggest concern is loosing tiles - and while the attachment methods have been discusses I haven’t seen any discussion of what the mechanical forces are that the tiles will have to survive.If you mean swirls and eddies, probably none while hypersonic. I speak from a great depth of not knowing much.
Obviously the thermal expansion and contraction of the tanks.
Sonic vibration generated by SH during initial stages of launch - but just how big are those forces?
Vibration from the SS Raptors transmitted through the hull?
My biggest unknown - how much turbulence is there at the surface of the tiles during EDL? And when does the peak occur?
Thanks Phil - your explanation helps.Sorry if this has already been discussed and I missed it. My biggest concern is loosing tiles - and while the attachment methods have been discusses I haven’t seen any discussion of what the mechanical forces are that the tiles will have to survive.If you mean swirls and eddies, probably none while hypersonic. I speak from a great depth of not knowing much.
Obviously the thermal expansion and contraction of the tanks.
Sonic vibration generated by SH during initial stages of launch - but just how big are those forces?
Vibration from the SS Raptors transmitted through the hull?
My biggest unknown - how much turbulence is there at the surface of the tiles during EDL? And when does the peak occur?
Using a sphere as a simplified model, the hypersonic air compresses and heats on the leading point, forms a shockwave, and has nowhere to go. This is the stagnation point. A tiny smidge to the side the compressed air is free to move radially and is free to expand slightly. This effect is greater the further from the stagnation point. Lateral movement is virtually impossible (I think). Looking from the side, this flow looks like a bow wave spreading further from the surface the further it is from the stagnation point. The outer edge of this flow is the shockwave. I'm not sure, but I think this flow is supersonic.
It is this flow that holds the plasma off the surface. As the flow passes beyond the 'equator', the stagnation point being the 'pole', there is the chance for turbulence, but this will be in the wake of the SS and is a step beyond my understanding so YMMV.
Applying this to SS is not simple. A post within the last couple of pages pointed out that the AoA will be ~50deg putting the stagnation point on the nosecone somewhere between the cylinder and the tip. Use your imagination to visualize the radial flow from this point. I'm still working on it.
Each flap will also be facing this environment which leads me to believe they will never be face on square to the flow while hypersonic. The transition from raceways is critical. The MK1 raceways had the leading edge forming a rough tangent to the hull allowing a smooth flow transition. If the fins angle forward if this angle the shock could impinge on them which would rip them apart.
I'm trying to visualize the tiles at the stagnation point without much luck yet. If there is packing between them there shouldn't be much problem but without packing (I'm wandering into Wonderland here) there might be flow underneath the tiles. The flow is hot from compression which is not a good thing but at least the tiles would still protect from the plasma's radiative heating. If the flow is supersonic I'm not sure of its impact on the mounting pins and tile edges but I can't see anything good coming of it.
My conclusion is that turbulence, in the traditional sense, should not be a problem but without a robust packing scheme there could be other problems. My understanding really only approached amateur level on this so YMMV.
Phil
I'm really not qualified to have anything more than a guess. And a week one at that.Thanks Phil - your explanation helps.Sorry if this has already been discussed and I missed it. My biggest concern is loosing tiles - and while the attachment methods have been discusses I haven’t seen any discussion of what the mechanical forces are that the tiles will have to survive.If you mean swirls and eddies, probably none while hypersonic. I speak from a great depth of not knowing much.
Obviously the thermal expansion and contraction of the tanks.
Sonic vibration generated by SH during initial stages of launch - but just how big are those forces?
Vibration from the SS Raptors transmitted through the hull?
My biggest unknown - how much turbulence is there at the surface of the tiles during EDL? And when does the peak occur?
Using a sphere as a simplified model, the hypersonic air compresses and heats on the leading point, forms a shockwave, and has nowhere to go. This is the stagnation point. A tiny smidge to the side the compressed air is free to move radially and is free to expand slightly. This effect is greater the further from the stagnation point. Lateral movement is virtually impossible (I think). Looking from the side, this flow looks like a bow wave spreading further from the surface the further it is from the stagnation point. The outer edge of this flow is the shockwave. I'm not sure, but I think this flow is supersonic.
It is this flow that holds the plasma off the surface. As the flow passes beyond the 'equator', the stagnation point being the 'pole', there is the chance for turbulence, but this will be in the wake of the SS and is a step beyond my understanding so YMMV.
Applying this to SS is not simple. A post within the last couple of pages pointed out that the AoA will be ~50deg putting the stagnation point on the nosecone somewhere between the cylinder and the tip. Use your imagination to visualize the radial flow from this point. I'm still working on it.
Each flap will also be facing this environment which leads me to believe they will never be face on square to the flow while hypersonic. The transition from raceways is critical. The MK1 raceways had the leading edge forming a rough tangent to the hull allowing a smooth flow transition. If the fins angle forward if this angle the shock could impinge on them which would rip them apart.
I'm trying to visualize the tiles at the stagnation point without much luck yet. If there is packing between them there shouldn't be much problem but without packing (I'm wandering into Wonderland here) there might be flow underneath the tiles. The flow is hot from compression which is not a good thing but at least the tiles would still protect from the plasma's radiative heating. If the flow is supersonic I'm not sure of its impact on the mounting pins and tile edges but I can't see anything good coming of it.
My conclusion is that turbulence, in the traditional sense, should not be a problem but without a robust packing scheme there could be other problems. My understanding really only approached amateur level on this so YMMV.
Phil
Guess I should have explained my concern better - will there be enough turbulence during those periods of peak heating that would rip a tile off. Based on your explanation, probably not. Bigger issue with hot gases getting between and under the tiles causing thermal rather than pure mechanical damage. Right?
For sure more than one pass coming back to Earth. To Mars could maybe work single pass, but two passes probably wise.
But where are the tri-pins here, ha! Three plasma true bungs?Odd that they selected three pin arrangement (-Surprised Pikachu), all three pin tiles at SN5 were fractured, but still attached
The three-pin arrangement assures three-sided symmetry of the tile which simplifies the production process a lot: the tiles basically have no fixed orientation but can be turned "any way you may wish".
Three plasma true bungs?
The tile design is not there yet.
The tile design is not there yet.
vibration from a single engine shattering tile?
Think of 6 at once.
Maybe when they attach the vacuum bells to the skirt it wont vibrate as much?
The tile design is not there yet.
I don't see evidence of shattering in that picture, just a missing tile.We don't see skirt's metal wall, we see a white hexagon that can be felt pad, adhesive or the inner insulator of the tile.
Might be worth investigating a large heat shield glove formed in a mold as a possibility... Mass reproducible, simpler, repairable, replaceable, less fragile and labor intensive... IMHO
Large section heat shield material was specified for the Boeing X-20 Dyna-Soar and we are now almost six decades advanced in material science since then... What I have in mind would add structural integrity for the vehicle as well...YMMVMight be worth investigating a large heat shield glove formed in a mold as a possibility... Mass reproducible, simpler, repairable, replaceable, less fragile and labor intensive... IMHO
Larger sections would probably be more fragile, if anything.
Large section heat shield material was specified for the Boeing X-20 Dyna-Soar and we are now almost six decades advanced in material science since then... What I have in mind would add structural integrity for the vehicle as well...YMMVMight be worth investigating a large heat shield glove formed in a mold as a possibility... Mass reproducible, simpler, repairable, replaceable, less fragile and labor intensive... IMHO
Larger sections would probably be more fragile, if anything.
Tile broke, adhesive held, felt isolation pad held. Tile insulation blocks have very little strength.
StarShip is still only a concept...Large section heat shield material was specified for the Boeing X-20 Dyna-Soar and we are now almost six decades advanced in material science since then... What I have in mind would add structural integrity for the vehicle as well...YMMVMight be worth investigating a large heat shield glove formed in a mold as a possibility... Mass reproducible, simpler, repairable, replaceable, less fragile and labor intensive... IMHO
Larger sections would probably be more fragile, if anything.
Maybe not the best/most valid example, as it is predate all the experience with the shuttle....
Nice concept, but a concept only.....
Large section heat shield material was specified for the Boeing X-20 Dyna-Soar and we are now almost six decades advanced in material science since then... What I have in mind would add structural integrity for the vehicle as well...YMMVMight be worth investigating a large heat shield glove formed in a mold as a possibility... Mass reproducible, simpler, repairable, replaceable, less fragile and labor intensive... IMHO
Larger sections would probably be more fragile, if anything.
Maybe not the best/most valid example, as it is predate all the experience with the shuttle....
Nice concept, but a concept only.....
Tile broke, adhesive held, felt isolation pad held. Tile insulation blocks have very little strength.
Hmm. Why is the white hex so much smaller than the surrounding tiles?
It looks like the black exterior shell has some thickness, perhaps 0.5 to 0.75 inch, and is probably a more structural material then the white tile interior which is mainly insulation. So ISTM that the high-temp adhesive was primarily holding the black shell, and when the adhesive failed around the edges, the while interior material also fractured and most of the tile fell off.
I stated is the other StarShip thread some time back that as currently envisioned the structure is not up to repeated cycling and reentry forces and "may" need additional stiffeners such as longerons IMHO. Thus the heat shield structure that I suggest is what will provide that just as I suggested the "Grid-Fins" 10 years back. They are learning as they go, time will tell what the vehicle evolves into... I continue to enjoy sitting back and observing the process... :)Large section heat shield material was specified for the Boeing X-20 Dyna-Soar and we are now almost six decades advanced in material science since then... What I have in mind would add structural integrity for the vehicle as well...YMMVMight be worth investigating a large heat shield glove formed in a mold as a possibility... Mass reproducible, simpler, repairable, replaceable, less fragile and labor intensive... IMHO
Larger sections would probably be more fragile, if anything.
Maybe not the best/most valid example, as it is predate all the experience with the shuttle....
Nice concept, but a concept only.....
It's similar to how the heat shields on Orion, Starliner, Dragon, etc work: the TPS tiles are attached to a substructure, and that subassembly is then attached to the vehicle primary structure / pressure vessel. Or the TPS is directly integrated into a composite secondary structure like the avcoat injected cells on Apollo and the initial Orion shield.
Shuttle went the route of attaching the TPs directly to the vehicle primary structure. At the scale of Shuttle and Starship, the mass penalty for a second structure is probably a significant negative factor.
I stated is the other StarShip thread some time back that as currently envisioned the structure is not up to repeated cycling and reentry forces and "may" need additional stiffeners such as longerons IMHO. Thus the heat shield structure that I suggest is what will provide that just as I suggested the "Grid-Fins" 10 years back. They are learning as they go, time will tell what the vehicle evolves into... I continue to enjoy sitting back and observing the process... :)
It would not be the first structure or vehicle that did not perform as envisioned by designers. Engineering history texts are full of what to be wary of and I pass that on to my students. It will have to prove itself in test flights and operation as have other vehicles... The design has changed before by SpaceX and "may" change again as they are breaking new ground... IMHO
I stated is the other StarShip thread some time back that as currently envisioned the structure is not up to repeated cycling and reentry forces and "may" need additional stiffeners such as longerons IMHO. Thus the heat shield structure that I suggest is what will provide that just as I suggested the "Grid-Fins" 10 years back. They are learning as they go, time will tell what the vehicle evolves into... I continue to enjoy sitting back and observing the process... :)
Are you saying that SpaceX has not analyzed and design their vehicle tank structure correctly? I don't understand why you think that their pressure stabilized tank structure is inadequate for reentry. Care to elaborate?
John
I would not be the first structure or vehicle that did not perform as envisioned by designers. Engineering history texts are full of what to be wary of and I pass that on to my students. It will have to prove itself in test flights and operation as have other vehicles... The design has changed before by SpaceX and "may" change again as they are breaking new ground... IMHO
I stated is the other StarShip thread some time back that as currently envisioned the structure is not up to repeated cycling and reentry forces and "may" need additional stiffeners such as longerons IMHO. Thus the heat shield structure that I suggest is what will provide that just as I suggested the "Grid-Fins" 10 years back. They are learning as they go, time will tell what the vehicle evolves into... I continue to enjoy sitting back and observing the process... :)
Are you saying that SpaceX has not analyzed and design their vehicle tank structure correctly? I don't understand why you think that their pressure stabilized tank structure is inadequate for reentry. Care to elaborate?
John
I stated is the other StarShip thread some time back that as currently envisioned the structure is not up to repeated cycling and reentry forces and "may" need additional stiffeners such as longerons IMHO. Thus the heat shield structure that I suggest is what will provide that just as I suggested the "Grid-Fins" 10 years back. They are learning as they go, time will tell what the vehicle evolves into... I continue to enjoy sitting back and observing the process... :)Large section heat shield material was specified for the Boeing X-20 Dyna-Soar and we are now almost six decades advanced in material science since then... What I have in mind would add structural integrity for the vehicle as well...YMMVMight be worth investigating a large heat shield glove formed in a mold as a possibility... Mass reproducible, simpler, repairable, replaceable, less fragile and labor intensive... IMHO
Larger sections would probably be more fragile, if anything.
Maybe not the best/most valid example, as it is predate all the experience with the shuttle....
Nice concept, but a concept only.....
It's similar to how the heat shields on Orion, Starliner, Dragon, etc work: the TPS tiles are attached to a substructure, and that subassembly is then attached to the vehicle primary structure / pressure vessel. Or the TPS is directly integrated into a composite secondary structure like the avcoat injected cells on Apollo and the initial Orion shield.
Shuttle went the route of attaching the TPs directly to the vehicle primary structure. At the scale of Shuttle and Starship, the mass penalty for a second structure is probably a significant negative factor.
John, without boring folks too much on the wrong thread I don't see the load paths though the structure stressed skin without a keel structure from the control fins on a reusable vehicle as envisioned by Elon... They are tackling the design by "first principles" so it is evolutionary process by nature... For example Columbia and Challenger were overbuilt and later vehicle were lighter as the database grew. I rather take weight out and simplify through flight test and production. It just a different approach... If the design succeeds as is I'm happy to have learned something new that has been added to the aerospace database... :)I would not be the first structure or vehicle that did not perform as envisioned by designers. Engineering history texts are full of what to be wary of and I pass that on to my students. It will have to prove itself in test flights and operation as have other vehicles... The design has changed before by SpaceX and "may" change again as they are breaking new ground... IMHO
I stated is the other StarShip thread some time back that as currently envisioned the structure is not up to repeated cycling and reentry forces and "may" need additional stiffeners such as longerons IMHO. Thus the heat shield structure that I suggest is what will provide that just as I suggested the "Grid-Fins" 10 years back. They are learning as they go, time will tell what the vehicle evolves into... I continue to enjoy sitting back and observing the process... :)
Are you saying that SpaceX has not analyzed and design their vehicle tank structure correctly? I don't understand why you think that their pressure stabilized tank structure is inadequate for reentry. Care to elaborate?
John
- I agree, structure has to be tested in flight. I also agree that the design has changed and will continue to, but you made a very specific claim:
...." the structure is not up to repeated cycling and reentry forces and "may" need additional stiffeners such as longerons"....
Why do you think the current structure is inadequate for repeated cycling and reentry forces?
John
Tile broke, adhesive held, felt isolation pad held. Tile insulation blocks have very little strength.None thing I don't understand about this picture. Where are the welded pins? Was this tile only glued to the surface?
Tile broke, adhesive held, felt isolation pad held. Tile insulation blocks have very little strength.None thing I don't understand about this picture. Where are the welded pins? Was this tile only glued to the surface?
Tile broke, adhesive held, felt isolation pad held. Tile insulation blocks have very little strength.None thing I don't understand about this picture. Where are the welded pins? Was this tile only glued to the surface?
It looks like this tile was a test of glued only. We have seen tiles that are stud pinned and seen a cracked remnant.
John, without boring folks too much on the wrong thread I don't see the load paths though the structure stressed skin without a keel structure from the control fins on a reusable vehicle as envisioned by Elon... They are tackling the design by "first principles" so it is evolutionary process by nature... For example Columbia and Challenger were overbuilt and later vehicle were lighter as the database grew. I rather take weight out and simplify through flight test and production. It just a different approach... If the design succeeds as is I'm happy to have learned something new that has been added to the aerospace database... :)
- I agree, structure has to be tested in flight. I also agree that the design has changed and will continue to, but you made a very specific claim:
...." the structure is not up to repeated cycling and reentry forces and "may" need additional stiffeners such as longerons"....
Why do you think the current structure is inadequate for repeated cycling and reentry forces?
John
Thats a lot of weld on studs! Good task for a robot.Stud weld point locations are marked with pen and ruler (or straightedge with slight curve ; ) so not a robot work, yet?
So, most (or all?) of the tile fastening tests were performed at the skirt of SS.Vibration/acoustic stress should be the worst there, and the skirt might even experience large-scale flexing. Especially during landing, on short legs, the engine bay must have a lot of low-frequency resonances. I wish we could see high-speed footage.
Do you think this is because there the most stresses, e.g. from vibrations, are?
John, I make no accusations of SpaceX "winging it". I'm only quoting Elon's design philosophy of working from "first principles of physics" thus writing their own textbook as they progress though development. Competitors will go through years of engineering analysis before ever considering bending metal to the point of paralysis. Elon prefers to bend metal and engineer as you go...They continue to go where other aerospace giants fear to tread which I think is awesome... :)John, without boring folks too much on the wrong thread I don't see the load paths though the structure stressed skin without a keel structure from the control fins on a reusable vehicle as envisioned by Elon... They are tackling the design by "first principles" so it is evolutionary process by nature... For example Columbia and Challenger were overbuilt and later vehicle were lighter as the database grew. I rather take weight out and simplify through flight test and production. It just a different approach... If the design succeeds as is I'm happy to have learned something new that has been added to the aerospace database... :)
- I agree, structure has to be tested in flight. I also agree that the design has changed and will continue to, but you made a very specific claim:
...." the structure is not up to repeated cycling and reentry forces and "may" need additional stiffeners such as longerons"....
Why do you think the current structure is inadequate for repeated cycling and reentry forces?
John
- I agree, early development vehicles are designed with more robustness to cover uncertainty in the loads and stress models. As flight data is gathered the design is refined to better match reality. The point I want to make is that the loads and stress models exist before the vehicle is built, even development vehicles. I am sure its not your intent, but you make it sound like SpaceX is winging it. I am positive they have full computer models of the loads and stresses for the entire vehicle throughout the flight envelope.
- Forward and aft flap actuators are the only points which apply a spanwise moment to the vehicle. We definitely have seen the forward internal structural ring which transmits flap torque through the nose cone. I am pretty sure we have seen the aft internal structural ring as well.
- What would the keel structure do? The Flap torque goes across the vehicle. A keel would resist lengthwise moments and is not needed since the pressurized tanks provide all the lengthwise bending strength needed.
- I am still confused as to your concern. A diagram might help.
John
Thats a lot of weld on studs! Good task for a robot.Stud weld point locations are marked with pen and ruler (or straightedge with slight curve ; ) so not a robot work, yet?
I'm fairly confident the pins were stud welded by one of the new robots. Right after the attached photo we started to see the bulk install of pins and heat shield patterns.Thats a lot of weld on studs! Good task for a robot.Stud weld point locations are marked with pen and ruler (or straightedge with slight curve ; ) so not a robot work, yet?
Thats a lot of weld on studs! Good task for a robot.Stud weld point locations are marked with pen and ruler (or straightedge with slight curve ; ) so not a robot work, yet?
...Edit: All the TPS tiles fell off!Not surprising because just a static fire fractured one of them.
...Edit: All the TPS tiles fell off!Not surprising because just a static fire fractured one of them.
I also wonder if the tile mounting compound (I think that's what it is) that we see in the pics (the white) could also have some ablative thermal properties of its own, or could be made to have, so that it could protect the steel below enough for one survivable reentry in case of the loss of a tile. Far better than LOV, if so.
I think any burn through = LOV. As soon as there is a hole pressurised gas or liquid will be ejected from the hole acting like an RCS. During re-entry forces on the skin near the hole and pressure from inside would also probably cause a major tear / rupture....Edit: All the TPS tiles fell off!Not surprising because just a static fire fractured one of them.
Looks to me like they have some major problems regarding that method of tile mount. I hope the pinned tiles (which these are not) fare better.
I'm wondering if they are having a resonance problem; perhaps the shape, size, and composition of the tiles makes them prone to resonance issues in the acoustic environment they experience.
I also wonder if the tile mounting compound (I think that's what it is) that we see in the pics (the white) could also have some ablative thermal properties of its own, or could be made to have, so that it could protect the steel below enough for one survivable reentry in case of the loss of a tile. Far better than LOV, if so.
Would anyone happen to know how critical a prop tank burn-through would be during reentry? I know Starship relies on tank pressure for some of its structural strength, but is that strength crucial for reentry and landing? The reason I ask is that if it is, a single burn-through on a tank skin is LOV. If not, the loss of a single may be survivable.
I think there's a misconception here. Maybe mine, maybe yours. My take is that the white is not the bonding. The bonding goo was green. This looks like the tile delaminated and the white is the layer under the black face....Edit: All the TPS tiles fell off!Not surprising because just a static fire fractured one of them.
Looks to me like they have some major problems regarding that method of tile mount. I hope the pinned tiles (which these are not) fare better.
I'm wondering if they are having a resonance problem; perhaps the shape, size, and composition of the tiles makes them prone to resonance issues in the acoustic environment they experience.
I also wonder if the tile mounting compound (I think that's what it is) that we see in the pics (the white) could also have some ablative thermal properties of its own, or could be made to have, so that it could protect the steel below enough for one survivable reentry in case of the loss of a tile. Far better than LOV, if so.
Would anyone happen to know how critical a prop tank burn-through would be during reentry? I know Starship relies on tank pressure for some of its structural strength, but is that strength crucial for reentry and landing? The reason I ask is that if it is, a single burn-through on a tank skin is LOV. If not, the loss of a single may be survivable.
And yeah, I have to go with the crowd. A burn through is LOM.
Looks to me like they have some major problems regarding that method of tile mount. I hope the pinned tiles (which these are not) fare better.I think there's a misconception here. Maybe mine, maybe yours. My take is that the white is not the bonding. The bonding goo was green. This looks like the tile delaminated and the white is the layer under the black face.
I'm wondering if they are having a resonance problem; perhaps the shape, size, and composition of the tiles makes them prone to resonance issues in the acoustic environment they experience.
I also wonder if the tile mounting compound (I think that's what it is) that we see in the pics (the white) could also have some ablative thermal properties of its own, or could be made to have, so that it could protect the steel below enough for one survivable reentry in case of the loss of a tile. Far better than LOV, if so.
Would anyone happen to know how critical a prop tank burn-through would be during reentry? I know Starship relies on tank pressure for some of its structural strength, but is that strength crucial for reentry and landing? The reason I ask is that if it is, a single burn-through on a tank skin is LOV. If not, the loss of a single may be survivable.
I'm waiting for a closeup to see if it delaminated immediately under the surface layer or across the bottom. I think I saw a closeup from after the static fire and that white layer looked real thin. If this is right the bonding worked like a champ and the tile couldn't take it. Maybe vibration, maybe differential thermal expansion.
And yeah, I have to go with the crowd. A burn through is LOM.
When the attachment system fails, is half a tile (bonded) better than no tile(clips)?
John,
I find that strength issue and your comment that it looks similar to the shuttle tile very concerning - If you don’t mind taking a shot at the question, what’s to avoid the brittleness and general extreme fussiness (stemming in significant part from the fragility, I think) that plagued the shuttle tiles?
John,
I find that strength issue and your comment that it looks similar to the shuttle tile very concerning - If you don’t mind taking a shot at the question, what’s to avoid the brittleness and general extreme fussiness (stemming in significant part from the fragility, I think) that plagued the shuttle tiles?
Another closeup of busted heat shield tiles from the photos and updates thread.Do we know for sure that the tiles fell off?
Another closeup of busted heat shield tiles from the photos and updates thread.Do we know for sure that the tiles fell off?
It's possible they were removed after flight for inspection.
John,
I find that strength issue and your comment that it looks similar to the shuttle tile very concerning - If you don’t mind taking a shot at the question, what’s to avoid the brittleness and general extreme fussiness (stemming in significant part from the fragility, I think) that plagued the shuttle tiles?
The TUFROC system is supposed to provide greater tile strength by embedding the silica/alumina ceramic in a fiber matrix.
The fractured tiles show no sign of that in the fracture zone so either it is not TUFROC or the fibers are very short and only provide very localised support. There could still be a long way to go on the tile development front but at least they are learning of the issues at an early stage.
Personally I think they could adopt an ablative tile system like PICA-X for early flights until the ceramic tiles have reached sufficient maturity. SpaceX have stated numerous times that the Dragon heatshield is barely damaged by re-entry and could be used many times. It would be feasible to say replace heat affected tiles on the center line of the windward side of tankers after five flights and the complete set of tiles after ten flights and still perform the Artemis and Dear Moon missions for example.
true. That I meant was more whether a half thick tile is better than no tile?When the attachment system fails, is half a tile (bonded) better than no tile(clips)?
The attachment did not fail, the tile did. It wasn't strong enough.
John
This looks very much similar to Shuttle tile. The white appears to be fractured insulation tile which is white. The black outer covering is paper thin glass like coating to toughen the outer layer of the fragile insulation block.I found the pic and had it queued up but MECO beat me to it. There is a tan layer under the white. This could be the felt layer and reinforces my earlier speculation that the problem might be vibration.
They look like they are even mounted on a felt pad, but maybe not.
John
When the attachment system fails, is half a tile (bonded) better than no tile(clips)?If they can get the problem down to a low roar, it might be ok for a 'one EDL only'. Maybe.
It wont hurt and might be enough. Looking at the properties* of 304L it seems like it might start annealing and loosing the full-hard strength around 680-700K so the goal is likely to for the tiles to keep it below that. The steel should however be able to take maybe 300-400K more before rupturing (if the tanks are pressurized to a little over 1 atm, i.e. 1/8 of maximum pressure).true. That I meant was more whether a half thick tile is better than no tile?When the attachment system fails, is half a tile (bonded) better than no tile(clips)?
The attachment did not fail, the tile did. It wasn't strong enough.
John
Taking the number of tiles (studs for now) on SN8 and the announced 20km hop, the exclusion zone under the trajectory will be an interesting place.
Nomadd should be able to collect some tile samples from the beach after. :)
A bit more seriously: given the latest results (some tiles hold, but its not guaranteed) will they risk that hop with numerous tiles? Tile fragments landing in the ocean may not a problem, but they can end up with debris cleaning/pickup teams at the beach, if not for environmental than for ITAR.
Taking the number of tiles (studs for now) on SN8 and the announced 20km hop, the exclusion zone under the trajectory will be an interesting place.
Nomadd should be able to collect some tile samples from the beach after. :)
A bit more seriously: given the latest results (some tiles hold, but its not guaranteed) will they risk that hop with numerous tiles? Tile fragments landing in the ocean may not a problem, but they can end up with debris cleaning/pickup teams at the beach, if not for environmental than for ITAR.
I would say SN8 will only have test tile locations. SN8 will be subsonic and not even close to requiring tiles.
Taking the number of tiles (studs for now) on SN8 and the announced 20km hop, the exclusion zone under the trajectory will be an interesting place.
Nomadd should be able to collect some tile samples from the beach after. :)
A bit more seriously: given the latest results (some tiles hold, but its not guaranteed) will they risk that hop with numerous tiles? Tile fragments landing in the ocean may not a problem, but they can end up with debris cleaning/pickup teams at the beach, if not for environmental than for ITAR.
I would say SN8 will only have test tile locations. SN8 will be subsonic and not even close to requiring tiles.
I think you want to put on a good number of tiles. Especially in areas of concern, such as those areas that bridge cryogenic to ambient temperature, control surface transitions etc.
The leading edges of terminating tiles might be important too.
Was that heavy pin pattern, on SN8 or 9, I try find it again at update thread but it is bit too dense.
[Edit] Ok, Mary's photo of SN8 have a tri-pin pattern but I don't see pins. Do they test stud welds effect to the skin of the ship? And the pin picture part is for SN9. (?)
https://forum.nasaspaceflight.com/index.php?topic=51332.1420
I can't see it would be that much of an issue. The launch area, beach and immediate sea lanes will be cleared before launch. So what if a few silica tiles fall off and flutter into the sea or onto the beach. I would have thought the worst restriction that might be imposed would be to ensure the beach was tidied up afterwards.Was that heavy pin pattern, on SN8 or 9, I try find it again at update thread but it is bit too dense.
[Edit] Ok, Mary's photo of SN8 have a tri-pin pattern but I don't see pins. Do they test stud welds effect to the skin of the ship? And the pin picture part is for SN9. (?)
https://forum.nasaspaceflight.com/index.php?topic=51332.1420
Maybe the pins are there but not visible from this angle. Its a low res image on the specific area.
But if you are right, and its only the pattern, than I got my answer: the pins was there but removed, presumably to avoid risk/debris on the wider area (20km hop).
Edit: SN8 was also booked for a 150m hop If i remember correctly, but now it goes directly for the 20km. It makes sense: they can accept falling tiles on those 150m (affecting the pad area only), but cannot take the risk (or get approval) for the same on a 20km flight, with a much longer downrange.
I can't see it would be that much of an issue. The launch area, beach and immediate sea lanes will be cleared before launch. So what if a few silica tiles fall off and flutter into the sea or onto the beach. I would have thought the worst restriction that might be imposed would be to ensure the beach was tidied up afterwards.Was that heavy pin pattern, on SN8 or 9, I try find it again at update thread but it is bit too dense.
[Edit] Ok, Mary's photo of SN8 have a tri-pin pattern but I don't see pins. Do they test stud welds effect to the skin of the ship? And the pin picture part is for SN9. (?)
https://forum.nasaspaceflight.com/index.php?topic=51332.1420
Maybe the pins are there but not visible from this angle. Its a low res image on the specific area.
But if you are right, and its only the pattern, than I got my answer: the pins was there but removed, presumably to avoid risk/debris on the wider area (20km hop).
Edit: SN8 was also booked for a 150m hop If i remember correctly, but now it goes directly for the 20km. It makes sense: they can accept falling tiles on those 150m (affecting the pad area only), but cannot take the risk (or get approval) for the same on a 20km flight, with a much longer downrange.
I can't see it would be that much of an issue. The launch area, beach and immediate sea lanes will be cleared before launch. So what if a few silica tiles fall off and flutter into the sea or onto the beach. I would have thought the worst restriction that might be imposed would be to ensure the beach was tidied up afterwards.Was that heavy pin pattern, on SN8 or 9, I try find it again at update thread but it is bit too dense.
[Edit] Ok, Mary's photo of SN8 have a tri-pin pattern but I don't see pins. Do they test stud welds effect to the skin of the ship? And the pin picture part is for SN9. (?)
https://forum.nasaspaceflight.com/index.php?topic=51332.1420
Maybe the pins are there but not visible from this angle. Its a low res image on the specific area.
But if you are right, and its only the pattern, than I got my answer: the pins was there but removed, presumably to avoid risk/debris on the wider area (20km hop).
Edit: SN8 was also booked for a 150m hop If i remember correctly, but now it goes directly for the 20km. It makes sense: they can accept falling tiles on those 150m (affecting the pad area only), but cannot take the risk (or get approval) for the same on a 20km flight, with a much longer downrange.
Its silica (not only) tiles and insulation pads (what is the matetial for that?). Issues can be personal safety, ITAR, environmental.
It could be a no go by either causing a real issue, or by simply lenghtening the approval process. For example insulation pad material needs additional paperwork for environmental assesment. But any combination of those factors could be enough to skip this test from the first flight.
I think we would see some shadows if the pins were there.Was that heavy pin pattern, on SN8 or 9, I try find it again at update thread but it is bit too dense.
[Edit] Ok, Mary's photo of SN8 have a tri-pin pattern but I don't see pins. Do they test stud welds effect to the skin of the ship? And the pin picture part is for SN9. (?)
https://forum.nasaspaceflight.com/index.php?topic=51332.1420 (https://forum.nasaspaceflight.com/index.php?topic=51332.1420)
Maybe the pins are there but not visible from this angle. Its a low res image on the specific area.
But if you are right, and its only the pattern, than I got my answer: the pins was there but removed, presumably to avoid risk/debris on the wider area (20km hop).
Edit: SN8 was also booked for a 150m hop If i remember correctly, but now it goes directly for the 20km. It makes sense: they can accept falling tiles on those 150m (affecting the pad area only), but cannot take the risk (or get approval) for the same on a 20km flight, with a much longer downrange.
Hmm, perhaps better leave the job to the experts...
Hmm, perhaps better leave the job to the experts...
Since when has that stopped anyone on this forum (myself included) sharing our "wisdom"? ;D
I am beginning to fear that the damn' tiles may be the long pole in Starship development.emphasis mine
Starship has such a nice, regular 50.-cal bullet shape that they could probably pull a huge heat-resistant textile sock over the whole thing and stitch all the tiles onto that (with some other method covering the body flaps).
Hmm, perhaps better leave the job to the experts...
I am beginning to fear that the damn' tiles may be the long pole in Starship development.emphasis mine
Starship has such a nice, regular 50.-cal bullet shape that they could probably pull a huge heat-resistant textile sock over the whole thing and stitch all the tiles onto that (with some other method covering the body flaps).
Hmm, perhaps better leave the job to the experts...
We have seen this before, some 4 decades ago. Be it "old" or "new", one constant is that "space is hard".
I remember Columbia shedding her tiles from a simple ferry flight on the back of the SCA...I am beginning to fear that the damn' tiles may be the long pole in Starship development.emphasis mine
Starship has such a nice, regular 50.-cal bullet shape that they could probably pull a huge heat-resistant textile sock over the whole thing and stitch all the tiles onto that (with some other method covering the body flaps).
Hmm, perhaps better leave the job to the experts...
We have seen this before, some 4 decades ago. Be it "old" or "new", one constant is that "space is hard".
I remember Columbia shedding her tiles from a simple ferry flight on the back of the SCA...Good memory. It was due to flying through a rainstorm, and the water forced over 250 tiles to be replaced. Not sure if any were actually shed.
Starlink launching not so much though, unless they go expendable for the Starship part, and I don't think they want to do that. Although it might be worth it to waste a stripped down cargo Starship second stage to yeet up 400 Starlinks at a time.
The good thing is that their Artemis contribution doesn't require a heat shield, so if the tiles take longer it doesn't threaten that potential contract.
Ditto for Dear Moon, if they are willing to bring down the passengers in a Dragon at the end of the journey.
If the tiles prove too troublesome might we see a return to transpirational cooling?Transpiration cooling is really massive and complicated.
The advantages would be that the perforated transpirational layer should survive vibration, easy to conform to the curves, contract when cold closing the pores and opening them when warm when needed.
The advantages would be that the perforated transpirational layer should survive vibration, easy to conform to the curves, contract when cold closing the pores and opening them when warm when needed.
Here is the event I'm speaking of...I remember Columbia shedding her tiles from a simple ferry flight on the back of the SCA...Good memory. It was due to flying through a rainstorm, and the water forced over 250 tiles to be replaced. Not sure if any were actually shed.
Here's a detailed and readable document (https://spaceflight.nasa.gov/shuttle/archives/sts-107/investigation/tps_safety.pdf) about the shuttle TPS safety issues and maintenance. Of note, the biggest chronic problems kept being the RTV (silicon rubber adhesive), especially with regards to dealing with rain or other chemicals (like waterproofing, cleaners, or incidental chemical spills) I can imagine that Starship's mechanical pin fastener strategy would sidestep much of that chronic problem.
Holes in a material expand when the material itself expands. This is how thermal shrink-fit collets work.The advantages would be that the perforated transpirational layer should survive vibration, easy to conform to the curves, contract when cold closing the pores and opening them when warm when needed.
I think transpiration pores will get wider upon cooling, and smaller with heating.
The good thing is that their Artemis contribution doesn't require a heat shield, so if the tiles take longer it doesn't threaten that potential contract.
In principle, yes, they could fly both the HLS lander and CLPS deliveries without reentry and landing on Earth. But it would require expending half a dozen or so tankers for each payload flight.Quote from: MandellaDitto for Dear Moon, if they are willing to bring down the passengers in a Dragon at the end of the journey.
Also requires expending several tankers. Even more tankers than for the HLS and CLPS missions, even; if you can't trust the heatshield, then you need to do propulsive braking into LEO when returning from the Moon, instead of aerobraking, which requires even more propellant (and likely doing a second refuelling while en route towards the Moon).
So, practically speaking, I find it unlikely. It would increase their costs quite a lot. But they may do it even if EDL hasn't been perfected. Even if one out of three tanker landings fail, it would still bring down their costs quite a lot; but on the other hand, it requires them to have manufacturing up to speed, so they have enough new tankers available to replace those that are lost.
I think they really need 6 raptors on Starship to get into orbit.The good thing is that their Artemis contribution doesn't require a heat shield, so if the tiles take longer it doesn't threaten that potential contract.
In principle, yes, they could fly both the HLS lander and CLPS deliveries without reentry and landing on Earth. But it would require expending half a dozen or so tankers for each payload flight.Quote from: MandellaDitto for Dear Moon, if they are willing to bring down the passengers in a Dragon at the end of the journey.
Also requires expending several tankers. Even more tankers than for the HLS and CLPS missions, even; if you can't trust the heatshield, then you need to do propulsive braking into LEO when returning from the Moon, instead of aerobraking, which requires even more propellant (and likely doing a second refuelling while en route towards the Moon).
So, practically speaking, I find it unlikely. It would increase their costs quite a lot. But they may do it even if EDL hasn't been perfected. Even if one out of three tanker landings fail, it would still bring down their costs quite a lot; but on the other hand, it requires them to have manufacturing up to speed, so they have enough new tankers available to replace those that are lost.
I need to write that on my hand, since for some reason I keep forgetting that orbital refueling needs tankers.
:-[
So yeah, possible if using expendable tankers, but it changes things.
Still, a stripped down "Starship" which is really hardly a Starship at all, lacking all body flaps and landing gear and running nothing but vacuum Raptors might not be much more costly than the existing Falcon 9 second stage, could get the job done. Be interesting to see a real cost breakdown of it, but we'd have to know internal financial figures that we don't have access to to be anywhere close to accurate.
In any case, getting far from the subject of heat shields. Theoretical expendable Starships probably needs its own thread.
I think they really need 6 raptors on Starship to get into orbit.The good thing is that their Artemis contribution doesn't require a heat shield, so if the tiles take longer it doesn't threaten that potential contract.
In principle, yes, they could fly both the HLS lander and CLPS deliveries without reentry and landing on Earth. But it would require expending half a dozen or so tankers for each payload flight.Quote from: MandellaDitto for Dear Moon, if they are willing to bring down the passengers in a Dragon at the end of the journey.
Also requires expending several tankers. Even more tankers than for the HLS and CLPS missions, even; if you can't trust the heatshield, then you need to do propulsive braking into LEO when returning from the Moon, instead of aerobraking, which requires even more propellant (and likely doing a second refuelling while en route towards the Moon).
So, practically speaking, I find it unlikely. It would increase their costs quite a lot. But they may do it even if EDL hasn't been perfected. Even if one out of three tanker landings fail, it would still bring down their costs quite a lot; but on the other hand, it requires them to have manufacturing up to speed, so they have enough new tankers available to replace those that are lost.
I need to write that on my hand, since for some reason I keep forgetting that orbital refueling needs tankers.
:-[
So yeah, possible if using expendable tankers, but it changes things.
Still, a stripped down "Starship" which is really hardly a Starship at all, lacking all body flaps and landing gear and running nothing but vacuum Raptors might not be much more costly than the existing Falcon 9 second stage, could get the job done. Be interesting to see a real cost breakdown of it, but we'd have to know internal financial figures that we don't have access to to be anywhere close to accurate.
In any case, getting far from the subject of heat shields. Theoretical expendable Starships probably needs its own thread.
But it would require expending half a dozen or so tankers for each payload flight.
...
Also requires expending several tankers.
I know what you mean, but the heat shield can't be omitted - at least not on this thread ;)But it would require expending half a dozen or so tankers for each payload flight.
...
Also requires expending several tankers.
The things that are expended needn't be full "tankers" per-se. The heatshield, body flaps, payload interface, and payload fairing can be omitted. Maybe tack on a small nose cone. Some launches will no doubt double as test flights and therefore require a full vehicle, but this provides an option to augment that flight rate if needed.
Do I expect SpaceX to do this? No, not in the default case. Is it an option available to reduce the cost penalty in case they run into R&D delays? Sure.
I know what you mean, but the heat shield can't be omitted - at least not on this thread ;)But it would require expending half a dozen or so tankers for each payload flight.
...
Also requires expending several tankers.
The things that are expended needn't be full "tankers" per-se. The heatshield, body flaps, payload interface, and payload fairing can be omitted. Maybe tack on a small nose cone. Some launches will no doubt double as test flights and therefore require a full vehicle, but this provides an option to augment that flight rate if needed.
Do I expect SpaceX to do this? No, not in the default case. Is it an option available to reduce the cost penalty in case they run into R&D delays? Sure.
Sorry, an obscure joke of mine, I should know better - we are wandering slightly off topic - we cant omit the heat shield on a Starship heat shield thread (without going off topic).I know what you mean, but the heat shield can't be omitted - at least not on this thread ;)But it would require expending half a dozen or so tankers for each payload flight.
...
Also requires expending several tankers.
The things that are expended needn't be full "tankers" per-se. The heatshield, body flaps, payload interface, and payload fairing can be omitted. Maybe tack on a small nose cone. Some launches will no doubt double as test flights and therefore require a full vehicle, but this provides an option to augment that flight rate if needed.
Do I expect SpaceX to do this? No, not in the default case. Is it an option available to reduce the cost penalty in case they run into R&D delays? Sure.
Not sure what you mean.
Just pointing out that it isn't required to expend tankers, as claimed. What you do with this information is up to you. :)
I think it's possible that they'll fly expendable Starships to launch Starlink.
But expendable tankers to support a Dear Moon or NASA lunar landings? I find that much harder to believe. Dear Moon isn't on any kind of deadline, so it can just wait until they've ironed out the problems. And NASA lunar landings are planned for 2024 at the earliest. It seems hard to believe that they couldn't come up with some kind of working TPS solution in the next four years.
Note also that by expendable Starships I mean expendable in the same sense that early Falcon 9 first stages were expendable -- with every flight being used as an experiment to work on getting recover to work, even if on a particular flight there was no realistic hope of actual recovery.
Some launches will no doubt double as test flights and therefore require a full vehicle, but this provides an option to augment that flight rate if needed. (Naturally if it's not needed, you don't do it. :) )
Do I expect SpaceX to do this? No, not in the default case. Is it an option available to reduce the cost penalty in case they run into R&D delays? Sure.
Note also that by expendable Starships I mean expendable in the same sense that early Falcon 9 first stages were expendable -- with every flight being used as an experiment to work on getting recover to work, even if on a particular flight there was no realistic hope of actual recovery.I think that this is exactly what they'll do. The primary mission of a tanker is getting fuel into another Starship; the EDL side is an experimental bonus.
Just found this new SpaceX Job posting on linkedin (7 hours ago)not sure if posted here already, but if not
"
MATERIALS ENGINEER, STARSHIP (HEATSHIELD)
This role would be on the materials engineering team, supporting alloy and process design. The materials engineering team supports materials across SpaceX via identification, development and implementation of advanced materials and processes. This role will be part of a team of engineers and process specialists developing new materials and processing solutions for different projects, including an early stage project to develop a metallic heat shield for Starship.
"
Moving away from the ceramic heat tiles toward a metallic heat shield? I'm confused
Although it may seem like corporate heresy, the option to use a disposable/repairable heat shield EARLY ON in Starship flights exists. SpaceX gets each Starship back for refurbishment for subsequent flight(s) and gets valuable flight data while gradual improvements are made to the heat shield design, OR that particular design approach is abandoned because it cannot lead to eventual re-usability.
Although it may seem like corporate heresy, the option to use a disposable/repairable heat shield EARLY ON in Starship flights exists. SpaceX gets each Starship back for refurbishment for subsequent flight(s) and gets valuable flight data while gradual improvements are made to the heat shield design, OR that particular design approach is abandoned because it cannot lead to eventual re-usability.Might as well make the whole ship (besides booster) disposable, then.
Minimum viable product to achieve the Starlink Launcher or Tanker or whatever missions.
Just more expensive and resource intensive than the long term goal, but gets 'em flyin'.
Adding 10 tonnes or a couple 10 tonnes to an EARLY 100-150 tonne payload Starship still allows flights.Minimum viable product is expending the Starship upper stage.
For example, if payload of Starship is "only" 100 tonnes, TEMPORARILY adding 20 tonnes extra of prototype heat-shield allows 80 tonnes to orbit with refurbishment re-use. Totally within the start off with a minimum viable product solution space.
They might have to go with some sort of secondary structure to attach the heatshield to, but I definitely don't see them going away from a reusable heatshield.I think the most up to date statements we have are still:
Because a Mars mission requires a reusable heatshield. Has to be used for both Mars entry and Mars return. Yeah, it's possible in principle to develop a dual-heat-pulse ablative shield, but that's actually a fairly low TRL solution, not standard proven technology. (And note this is partly why they went away from attempting to reuse PICA-X: it's actually very non-trivial to reuse an ablative heatshield because it becomes brittle after the first use.)
Starship will enter Mars’ atmosphere at 7.5 kilometers per second and decelerate aerodynamically. The vehicle’s heat shield is designed to withstand multiple entries, but given that the vehicle is coming into Mars' atmosphere so hot, we still expect to see some ablation of the heat shield (similar to wear and tear on a brake pad)...There are two interesting points:
Nope, that's an old statement from when they were still using PICA-X. Look it up, they haven't changed that.They might have to go with some sort of secondary structure to attach the heatshield to, but I definitely don't see them going away from a reusable heatshield.I think the most up to date statements we have are still:
Because a Mars mission requires a reusable heatshield. Has to be used for both Mars entry and Mars return. Yeah, it's possible in principle to develop a dual-heat-pulse ablative shield, but that's actually a fairly low TRL solution, not standard proven technology. (And note this is partly why they went away from attempting to reuse PICA-X: it's actually very non-trivial to reuse an ablative heatshield because it becomes brittle after the first use.)Quote from: SpaceX websiteStarship will enter Mars’ atmosphere at 7.5 kilometers per second and decelerate aerodynamically. The vehicle’s heat shield is designed to withstand multiple entries, but given that the vehicle is coming into Mars' atmosphere so hot, we still expect to see some ablation of the heat shield (similar to wear and tear on a brake pad)......
Adding 10 tonnes or a couple 10 tonnes to an EARLY 100-150 tonne payload Starship still allows flights.
For example, if payload of Starship is "only" 100 tonnes, TEMPORARILY adding 20 tonnes extra of prototype heat-shield allows 80 tonnes to orbit with refurbishment re-use. Totally within the start off with a minimum viable product solution space.
SpaceX can accomplish a lot of their early goals without (successful) EDL, but they need refuelling for almost everything.
Just found this new SpaceX Job posting on linkedin (7 hours ago)not sure if posted here already, but if not
"
MATERIALS ENGINEER, STARSHIP (HEATSHIELD)
This role would be on the materials engineering team, supporting alloy and process design. The materials engineering team supports materials across SpaceX via identification, development and implementation of advanced materials and processes. This role will be part of a team of engineers and process specialists developing new materials and processing solutions for different projects, including an early stage project to develop a metallic heat shield for Starship.
"
Moving away from the ceramic heat tiles toward a metallic heat shield? I'm confused
Adding 10 tonnes or a couple 10 tonnes to an EARLY 100-150 tonne payload Starship still allows flights.Minimum viable product is expending the Starship upper stage.
For example, if payload of Starship is "only" 100 tonnes, TEMPORARILY adding 20 tonnes extra of prototype heat-shield allows 80 tonnes to orbit with refurbishment re-use. Totally within the start off with a minimum viable product solution space.
All you're asking them to do is to develop their heatshield TWICE, which makes development twice as expensive.
Yeah, I'll concede that it is likely a lazy repeat of previous statements for the carbon fiber version (and the video is the old one). I think it might technically be correct ::) as the "latest" with regard to Mars entry (and Elon did talk about the tiles "acting as sensors" by ablating when too hot in the same time frame) but this is probably just indicative of the lack of Mars TPS specific updates...Nope, that's an old statement from when they were still using PICA-X. Look it up, they haven't changed that.They might have to go with some sort of secondary structure to attach the heatshield to, but I definitely don't see them going away from a reusable heatshield.I think the most up to date statements we have are still:
Because a Mars mission requires a reusable heatshield. Has to be used for both Mars entry and Mars return. Yeah, it's possible in principle to develop a dual-heat-pulse ablative shield, but that's actually a fairly low TRL solution, not standard proven technology. (And note this is partly why they went away from attempting to reuse PICA-X: it's actually very non-trivial to reuse an ablative heatshield because it becomes brittle after the first use.)Quote from: SpaceX websiteStarship will enter Mars’ atmosphere at 7.5 kilometers per second and decelerate aerodynamically. The vehicle’s heat shield is designed to withstand multiple entries, but given that the vehicle is coming into Mars' atmosphere so hot, we still expect to see some ablation of the heat shield (similar to wear and tear on a brake pad)......
I don't think Starlink is really a "goal" for SpaceX, it is more a way of funding their goals.SpaceX can accomplish a lot of their early goals without (successful) EDL, but they need refuelling for almost everything.
They don't need refueling for Starlink launches, and Starlink launches are almost everything in terms of early need for Starship.
They need refueling for lunar and martian missions, but those are longer term.
I don't think Starlink is really a "goal" for SpaceX, it is more a way of funding their goals.SpaceX can accomplish a lot of their early goals without (successful) EDL, but they need refuelling for almost everything.
They don't need refueling for Starlink launches, and Starlink launches are almost everything in terms of early need for Starship.
They need refueling for lunar and martian missions, but those are longer term.
Regardless, EDL isn't required for Starlink either, it just makes it cheaper by allowing for Starship reuse.
This is all wandering away from what I was trying to get at though, which was that (imho) SpaceX will want to launch tankers to practice refuelling even if they don't yet have the heatshields to return them.
Starlink is viable even when launched 60 at a time on an expendable Falcon second stage. It will be even more viable if launched 600 at a time on a potentially-expendable Starship. Reuse just makes it even cheaper still.I don't think Starlink is really a "goal" for SpaceX, it is more a way of funding their goals.SpaceX can accomplish a lot of their early goals without (successful) EDL, but they need refuelling for almost everything.
They don't need refueling for Starlink launches, and Starlink launches are almost everything in terms of early need for Starship.
They need refueling for lunar and martian missions, but those are longer term.
Regardless, EDL isn't required for Starlink either, it just makes it cheaper by allowing for Starship reuse.
This is all wandering away from what I was trying to get at though, which was that (imho) SpaceX will want to launch tankers to practice refuelling even if they don't yet have the heatshields to return them.
I strongly disagree with that.
I believe that SpaceX will definitely make the heat shield work before even starting on tankers.
Once they have cheap reuse of Starship, they can launch lots of Starlink satellites cheaply. As you say, that funds everything else. Why would getting huge amounts of funding as soon as possible not be a priority?
Cheap reuse of Starship also allows them to shift everything else Falcon 9 launches to Starship as soon as possible. Some customers will be conservative and have to see Starship in action for a while before they make the leap. But whatever it takes to get a particular customer to switch to Starship, that path doesn't start until Starship is being successfully reused cheaply.
Cheap reuse also allows them to be much more effective much more quickly with their orbital refueling development. It would be much, much more expensive for SpaceX to try to do orbital refueling development if they have to throw away the tanker on every test flight.
I find the “Responsibilities” section interesting:
Work closely with product design engineering teams to define requirements
Work with materials engineers to assess best in class approaches for powder metal processing consolidating and data analysis
Develop laboratory capabilities and analysis methods to implement such approaches and collaborate with vendors and external labs to augment internal capabilities
Specify, design, install, commission and/or validate metal processing equipment to support techniques such as melting, forging, rolling, and heat treating
Lead process development of developmental materials and processing techniques through parameter optimization, DOE experiments, and trials to support alloy design activities
Complete high heat flux experiments to evaluate material performance
Ensure developed materials meet all material design requirements
Sent from my iPhone using Tapatalk
Reusable metallic heat shields have been a holy grail in TPS technology since I first started working in that area during the Space Shuttle conceptual design period (1969-late 1971). My lab developed prototype metallic heat shields fabricated from niobium (aka columbium) coated with various ceramic oxides for increased oxidation resistance. We tested them up to 3000F (1649C) in specialized furnaces at air pressures typical of entry into the Earth's atmosphere. Mechanical tension and flexing loads were applied during these tests to determine the adhesion characteristics of the coatings. These samples could do a hundred simulated Shuttle entries without losing the coating.
See https://ntrs.nasa.gov/citations/19730024093
Nearly 25 years later in 1995 I worked on a NASA Langley contract to develop metallic heat shields for the X-33.
https://ntrs.nasa.gov/citations/20040095922
Interest in metallic heat shields has run hot and cold for the past 50 years. Maybe SpaceX can find a use for some of the previous work and develop a metallic heat shield that actually flies on a real spacecraft.
Does anybody have employee numbers for BC? I'm going to take a BOE stab at marginal costs for one SS with an eye to the economics of expendable on early launches. Or has this already been done somewhere?
Excuse my ignorance. Has any work been done on tungsten? I have a memory of using tungsten steel a long time ago. For a metal heat shield I imagine tungsten as being the best material, it is used to make light bulb filaments so can be made into wire. It has a melting point 3410 C. Is there a reason tungsten is not used?
Excuse my ignorance. Has any work been done on tungsten? I have a memory of using tungsten steel a long time ago. For a metal heat shield I imagine tungsten as being the best material, it is used to make light bulb filaments so can be made into wire. It has a melting point 3410 C. Is there a reason tungsten is not used?
Excuse my ignorance. Has any work been done on tungsten? I have a memory of using tungsten steel a long time ago. For a metal heat shield I imagine tungsten as being the best material, it is used to make light bulb filaments so can be made into wire. It has a melting point 3410 C. Is there a reason tungsten is not used?
Just found this new SpaceX Job posting on linkedin (7 hours ago)MrWeezy's find, SpX is already searching different paths for TPS.
"
MATERIALS ENGINEER, STARSHIP (HEATSHIELD)
This role would be on the materials engineering team, supporting alloy and process design. The materials engineering team supports materials across SpaceX via identification, development and implementation of advanced materials and processes. This role will be part of a team of engineers and process specialists developing new materials and processing solutions for different projects, including an early stage project to develop a metallic heat shield for Starship.
"
Moving away from the ceramic heat tiles toward a metallic heat shield? I'm confused
Philw1776 raised the issue of ablative as a temporary expedient and didn't exactly get shot down but he did get some flak.
One counter was the cost of developing two systems. There is some R&D overlap and reusing a (WAG) $5m ship will pay for a fair chunk of R&D. I actually doubt if it would come in under $10m. An ablative will inform on heat patterns and intensity for a more sophisticated system and may end up as a field repair technique.
Rafael uses 10 tons as the current estimate and another 10-20 tons will not be a a good thing but it is less bad than not flying or flying disposable. I can see this offset mass putting limitations on a landing profile but not driving it into the impossible. There is a lot of control authority in those raptors. Just takes more propellant, and loss of payload capacity. ISTM that getting 50 tons to reusable LEO is better than getting 100 throwaway tons, or worse yet, not flying at all.
On the nuts and bolts end, the stainless substructure hints at a lighter ablative construction than a traditional capsule. The thick insulating honeycomb needed to protect an aluminum shell can be much thinner, and maybe could go away.
AIUI, the Mercury capsule used a resinous material. This suggests that a spray on might work. Removal and replacement after each flight violates the principal of fast turnaround. So what. It's an expedient. Fast turnaround isn't going to show up all at once so any particular launch cadence will demand a fleet pipeline of some particular depth. If heat shield servicing lengthens the turnaround time that pipeline will have to get longer. It isn't as if SX won't have a long term use for a bunch of ships.
It may turn out that the long term fix is already in hand as a contingency plan and will show itself to be more than adequate and economical. If it's not, a less than ideal quick and dirty looks like a good way to get starlink up, nail refueling, gain flight experience, and show progress on HLS.
I didn't know that foamed titanium was a thing and found this: [size=78%]https://en.m.wikipedia.org/wiki/Titanium_foam (https://en.m.wikipedia.org/wiki/Titanium_foam)[/size]Excuse my ignorance. Has any work been done on tungsten? I have a memory of using tungsten steel a long time ago. For a metal heat shield I imagine tungsten as being the best material, it is used to make light bulb filaments so can be made into wire. It has a melting point 3410 C. Is there a reason tungsten is not used?
For TPS materials, not only melting point matters, but also weight and thermal conductivity. I think metal foam might be a good candidate. The foamy structure allows the thermal conductivity to be reduced tenfold. There are high melting point alloy / metal foams such as nickel-iron (1400-1450 ° C) or titanium (1668 ° C). In terms of weight, titanium foam is probably the best choice.
https://www.samaterials.com/465-foam-metal (https://www.samaterials.com/465-foam-metal)
Maybe spray-on Teflon could work as a temporary expedient. It wouldn't be nearly enough by itself as it is too difficult to make it thick enough if you spray it on, but maybe it could be applied to hot spots as additional protection. Of course that wouldn't help if the problem was tiles crumbling or falling off because of vibration.And tractor beams slide right off. Seriously, I don't know how they do it with frying pans but I once worked with a special glue for Teflon. It might have been a precursor to superglue. I was not impressed.
My bad on putting the word ablative in your mouth. It's more narrow than what you were saying.Philw1776 raised the issue of ablative as a temporary expedient and didn't exactly get shot down but he did get some flak.
One counter was the cost of developing two systems. There is some R&D overlap and reusing a (WAG) $5m ship will pay for a fair chunk of R&D. I actually doubt if it would come in under $10m. An ablative will inform on heat patterns and intensity for a more sophisticated system and may end up as a field repair technique.
Rafael uses 10 tons as the current estimate and another 10-20 tons will not be a a good thing but it is less bad than not flying or flying disposable. I can see this offset mass putting limitations on a landing profile but not driving it into the impossible. There is a lot of control authority in those raptors. Just takes more propellant, and loss of payload capacity. ISTM that getting 50 tons to reusable LEO is better than getting 100 throwaway tons, or worse yet, not flying at all.
On the nuts and bolts end, the stainless substructure hints at a lighter ablative construction than a traditional capsule. The thick insulating honeycomb needed to protect an aluminum shell can be much thinner, and maybe could go away.
AIUI, the Mercury capsule used a resinous material. This suggests that a spray on might work. Removal and replacement after each flight violates the principal of fast turnaround. So what. It's an expedient. Fast turnaround isn't going to show up all at once so any particular launch cadence will demand a fleet pipeline of some particular depth. If heat shield servicing lengthens the turnaround time that pipeline will have to get longer. It isn't as if SX won't have a long term use for a bunch of ships.
It may turn out that the long term fix is already in hand as a contingency plan and will show itself to be more than adequate and economical. If it's not, a less than ideal quick and dirty looks like a good way to get starlink up, nail refueling, gain flight experience, and show progress on HLS.
Here is what I said...
"the option to use a disposable/repairable heat shield EARLY ON in Starship flights exists. SpaceX gets each Starship back for refurbishment for subsequent flight(s) and gets valuable flight data while gradual improvements are made to the heat shield design, OR that particular design approach is abandoned because it cannot lead to eventual re-usability."
Clarification.
I wasn't thinking about ablative, although that is a possibility. Simply suggested a "not ready for full repeated re-use without refurbishment" which some posters took to mean total TPS changeout, ablative, or whatever.
To be more clear, I stand by my stated prediction that minimum viable product re-flights will start out with portions of the heat shield, whatever technology, being disposed/repaired/replaced. And that initial design will evolve to a final design, just like recoverable boosters did, only more rapidly. We've already seen tile attachment designs fail with replacements undoubtedly in the works.
The R-512E (Si-20Cr-20Fe) fused slurry silicide coating process was optimized to coat full size (20" x 20") single face rib and corrugation stiffened panels fabricated from FS-85 columbium alloy for 100 mission Space Shuttle heat shield applications. Structural life under simulated Space Shuttle lift-off stresses and reentry conditions demonstrated reuse capability well beyond 100 flights for R-512E coated FS-85 columbium heat shield panels.
And tractor beams slide right off. Seriously, I don't know how they do it with frying pans but I once worked with a special glue for Teflon. It might have been a precursor to superglue. I was not impressed.
So I looked a bit more at those studies I references earlier on metallic heatshields.Ceramic is WAY lighter, and Shuttle had very little payload. It weighed 78 tons dry and originally could get almost no payload to higher orbits like ISS. It took a few upgrades like the MUCH lighter external tank (which eventually saved 8.5 tons over the original tank) to get payload to ISS up to 16 tons. So using metallic TPS could eliminated the entire payload to many orbits that Shuttle used.
For the people talking about materials, niobium (previously known as columbium) with a ceramic-oxide coating seems to be a great candidate.
QuoteThe R-512E (Si-20Cr-20Fe) fused slurry silicide coating process was optimized to coat full size (20" x 20") single face rib and corrugation stiffened panels fabricated from FS-85 columbium alloy for 100 mission Space Shuttle heat shield applications. Structural life under simulated Space Shuttle lift-off stresses and reentry conditions demonstrated reuse capability well beyond 100 flights for R-512E coated FS-85 columbium heat shield panels.
Reading this, I'm now kind of curious why NASA went with the ceramic tiles for the Shuttle. The results from this testing sounds very promising.
...
Based on your sort of vague description of your idea, either:Philw1776 raised the issue of ablative as a temporary expedient and didn't exactly get shot down but he did get some flak.
One counter was the cost of developing two systems. There is some R&D overlap and reusing a (WAG) $5m ship will pay for a fair chunk of R&D. I actually doubt if it would come in under $10m. An ablative will inform on heat patterns and intensity for a more sophisticated system and may end up as a field repair technique.
Rafael uses 10 tons as the current estimate and another 10-20 tons will not be a a good thing but it is less bad than not flying or flying disposable. I can see this offset mass putting limitations on a landing profile but not driving it into the impossible. There is a lot of control authority in those raptors. Just takes more propellant, and loss of payload capacity. ISTM that getting 50 tons to reusable LEO is better than getting 100 throwaway tons, or worse yet, not flying at all.
On the nuts and bolts end, the stainless substructure hints at a lighter ablative construction than a traditional capsule. The thick insulating honeycomb needed to protect an aluminum shell can be much thinner, and maybe could go away.
AIUI, the Mercury capsule used a resinous material. This suggests that a spray on might work. Removal and replacement after each flight violates the principal of fast turnaround. So what. It's an expedient. Fast turnaround isn't going to show up all at once so any particular launch cadence will demand a fleet pipeline of some particular depth. If heat shield servicing lengthens the turnaround time that pipeline will have to get longer. It isn't as if SX won't have a long term use for a bunch of ships.
It may turn out that the long term fix is already in hand as a contingency plan and will show itself to be more than adequate and economical. If it's not, a less than ideal quick and dirty looks like a good way to get starlink up, nail refueling, gain flight experience, and show progress on HLS.
Here is what I said...
"the option to use a disposable/repairable heat shield EARLY ON in Starship flights exists. SpaceX gets each Starship back for refurbishment for subsequent flight(s) and gets valuable flight data while gradual improvements are made to the heat shield design, OR that particular design approach is abandoned because it cannot lead to eventual re-usability."
Clarification.
I wasn't thinking about ablative, although that is a possibility. Simply suggested a "not ready for full repeated re-use without refurbishment" which some posters took to mean total TPS changeout, ablative, or whatever.
To be more clear, I stand by my stated prediction that minimum viable product re-flights will start out with portions of the heat shield, whatever technology, being disposed/repaired/replaced. And that initial design will evolve to a final design, just like recoverable boosters did, only more rapidly. We've already seen tile attachment designs fail with replacements undoubtedly in the works.
Based on your sort of vague description of your idea, either:Philw1776 raised the issue of ablative as a temporary expedient and didn't exactly get shot down but he did get some flak.
One counter was the cost of developing two systems. There is some R&D overlap and reusing a (WAG) $5m ship will pay for a fair chunk of R&D. I actually doubt if it would come in under $10m. An ablative will inform on heat patterns and intensity for a more sophisticated system and may end up as a field repair technique.
Rafael uses 10 tons as the current estimate and another 10-20 tons will not be a a good thing but it is less bad than not flying or flying disposable. I can see this offset mass putting limitations on a landing profile but not driving it into the impossible. There is a lot of control authority in those raptors. Just takes more propellant, and loss of payload capacity. ISTM that getting 50 tons to reusable LEO is better than getting 100 throwaway tons, or worse yet, not flying at all.
On the nuts and bolts end, the stainless substructure hints at a lighter ablative construction than a traditional capsule. The thick insulating honeycomb needed to protect an aluminum shell can be much thinner, and maybe could go away.
AIUI, the Mercury capsule used a resinous material. This suggests that a spray on might work. Removal and replacement after each flight violates the principal of fast turnaround. So what. It's an expedient. Fast turnaround isn't going to show up all at once so any particular launch cadence will demand a fleet pipeline of some particular depth. If heat shield servicing lengthens the turnaround time that pipeline will have to get longer. It isn't as if SX won't have a long term use for a bunch of ships.
It may turn out that the long term fix is already in hand as a contingency plan and will show itself to be more than adequate and economical. If it's not, a less than ideal quick and dirty looks like a good way to get starlink up, nail refueling, gain flight experience, and show progress on HLS.
Here is what I said...
"the option to use a disposable/repairable heat shield EARLY ON in Starship flights exists. SpaceX gets each Starship back for refurbishment for subsequent flight(s) and gets valuable flight data while gradual improvements are made to the heat shield design, OR that particular design approach is abandoned because it cannot lead to eventual re-usability."
Clarification.
I wasn't thinking about ablative, although that is a possibility. Simply suggested a "not ready for full repeated re-use without refurbishment" which some posters took to mean total TPS changeout, ablative, or whatever.
To be more clear, I stand by my stated prediction that minimum viable product re-flights will start out with portions of the heat shield, whatever technology, being disposed/repaired/replaced. And that initial design will evolve to a final design, just like recoverable boosters did, only more rapidly. We've already seen tile attachment designs fail with replacements undoubtedly in the works.
1) It's essentially what they're already doing
or
2) It'll require a bunch of extra engineering.
Just to get it to work a single time takes a LOT of engineering time. So either you're describing their current plan or you're describing almost a doubling of engineering work into their heatshield.
So I looked a bit more at those studies I references earlier on metallic heatshields.Ceramic is WAY lighter, and Shuttle had very little payload. It weighed 78 tons dry and originally could get almost no payload to higher orbits like ISS. It took a few upgrades like the MUCH lighter external tank (which eventually saved 8.5 tons over the original tank) to get payload to ISS up to 16 tons. So using metallic TPS could eliminated the entire payload to many orbits that Shuttle used.
For the people talking about materials, niobium (previously known as columbium) with a ceramic-oxide coating seems to be a great candidate.
QuoteThe R-512E (Si-20Cr-20Fe) fused slurry silicide coating process was optimized to coat full size (20" x 20") single face rib and corrugation stiffened panels fabricated from FS-85 columbium alloy for 100 mission Space Shuttle heat shield applications. Structural life under simulated Space Shuttle lift-off stresses and reentry conditions demonstrated reuse capability well beyond 100 flights for R-512E coated FS-85 columbium heat shield panels.
Reading this, I'm now kind of curious why NASA went with the ceramic tiles for the Shuttle. The results from this testing sounds very promising.
...
Also, we hadn't had experiences with all the headaches the more brittle ceramic tiles caused.
The unit masses of the current SA/HC metallic TPS and the AETB-8 tiles are quite similar over the entire heating range.
Ceramic tiles, including AETB-8, were the only TPS that could withstand the highest heating, highest temperature
conditions studied. The advanced metallic TPS concept demonstrated the lowest mass over most of the heating
range, and the benefits of using efficient multilayer insulation are most evident at the higher heat loads. While
this advanced metallic TPS concept has not undergone rigorous design and testing, these results indicate that
metallic TPS have the potential to be mass competitive with blanket TPS concepts at moderate heating levels and
significantly lighter than ceramic tiles over their applicable temperature ranges.
There is no quick, easy fix for a large and lightweight thermal protection system, reparable or disposable or whathaveyou. It requires careful engineering. Just the way things are in aerospace.Based on your sort of vague description of your idea, either:Philw1776 raised the issue of ablative as a temporary expedient and didn't exactly get shot down but he did get some flak.
One counter was the cost of developing two systems. There is some R&D overlap and reusing a (WAG) $5m ship will pay for a fair chunk of R&D. I actually doubt if it would come in under $10m. An ablative will inform on heat patterns and intensity for a more sophisticated system and may end up as a field repair technique.
Rafael uses 10 tons as the current estimate and another 10-20 tons will not be a a good thing but it is less bad than not flying or flying disposable. I can see this offset mass putting limitations on a landing profile but not driving it into the impossible. There is a lot of control authority in those raptors. Just takes more propellant, and loss of payload capacity. ISTM that getting 50 tons to reusable LEO is better than getting 100 throwaway tons, or worse yet, not flying at all.
On the nuts and bolts end, the stainless substructure hints at a lighter ablative construction than a traditional capsule. The thick insulating honeycomb needed to protect an aluminum shell can be much thinner, and maybe could go away.
AIUI, the Mercury capsule used a resinous material. This suggests that a spray on might work. Removal and replacement after each flight violates the principal of fast turnaround. So what. It's an expedient. Fast turnaround isn't going to show up all at once so any particular launch cadence will demand a fleet pipeline of some particular depth. If heat shield servicing lengthens the turnaround time that pipeline will have to get longer. It isn't as if SX won't have a long term use for a bunch of ships.
It may turn out that the long term fix is already in hand as a contingency plan and will show itself to be more than adequate and economical. If it's not, a less than ideal quick and dirty looks like a good way to get starlink up, nail refueling, gain flight experience, and show progress on HLS.
Here is what I said...
"the option to use a disposable/repairable heat shield EARLY ON in Starship flights exists. SpaceX gets each Starship back for refurbishment for subsequent flight(s) and gets valuable flight data while gradual improvements are made to the heat shield design, OR that particular design approach is abandoned because it cannot lead to eventual re-usability."
Clarification.
I wasn't thinking about ablative, although that is a possibility. Simply suggested a "not ready for full repeated re-use without refurbishment" which some posters took to mean total TPS changeout, ablative, or whatever.
To be more clear, I stand by my stated prediction that minimum viable product re-flights will start out with portions of the heat shield, whatever technology, being disposed/repaired/replaced. And that initial design will evolve to a final design, just like recoverable boosters did, only more rapidly. We've already seen tile attachment designs fail with replacements undoubtedly in the works.
1) It's essentially what they're already doing
or
2) It'll require a bunch of extra engineering.
Just to get it to work a single time takes a LOT of engineering time. So either you're describing their current plan or you're describing almost a doubling of engineering work into their heatshield.
Almost certainly not double. If it were double they would just go straight for the finished/final article. The point being made is that its possible that they will go for a quick and easy method to get to a MVP...
Yeah, agreed there have been advances. I was just answering the question of why they went with ceramic originally for Shuttle (which was developed in the 1970s).So I looked a bit more at those studies I references earlier on metallic heatshields.Ceramic is WAY lighter, and Shuttle had very little payload. It weighed 78 tons dry and originally could get almost no payload to higher orbits like ISS. It took a few upgrades like the MUCH lighter external tank (which eventually saved 8.5 tons over the original tank) to get payload to ISS up to 16 tons. So using metallic TPS could eliminated the entire payload to many orbits that Shuttle used.
For the people talking about materials, niobium (previously known as columbium) with a ceramic-oxide coating seems to be a great candidate.
QuoteThe R-512E (Si-20Cr-20Fe) fused slurry silicide coating process was optimized to coat full size (20" x 20") single face rib and corrugation stiffened panels fabricated from FS-85 columbium alloy for 100 mission Space Shuttle heat shield applications. Structural life under simulated Space Shuttle lift-off stresses and reentry conditions demonstrated reuse capability well beyond 100 flights for R-512E coated FS-85 columbium heat shield panels.
Reading this, I'm now kind of curious why NASA went with the ceramic tiles for the Shuttle. The results from this testing sounds very promising.
...
Also, we hadn't had experiences with all the headaches the more brittle ceramic tiles caused.
True, but that second study does say that the masses of the newer, honeycomb shields are comparable to regular TPS. Even beter, actually
QuoteThe unit masses of the current SA/HC metallic TPS and the AETB-8 tiles are quite similar over the entire heating range.
Ceramic tiles, including AETB-8, were the only TPS that could withstand the highest heating, highest temperature
conditions studied. The advanced metallic TPS concept demonstrated the lowest mass over most of the heating
range, and the benefits of using efficient multilayer insulation are most evident at the higher heat loads. While
this advanced metallic TPS concept has not undergone rigorous design and testing, these results indicate that
metallic TPS have the potential to be mass competitive with blanket TPS concepts at moderate heating levels and
significantly lighter than ceramic tiles over their applicable temperature ranges.
So the super light stuff may not have been around for the Shuttle, but it would seem that there could actually be mass savings for Starship if this were employed.
There is no quick, easy fix for a large and lightweight thermal protection system, reparable or disposable or whathaveyou. It requires careful engineering. Just the way things are in aerospace.The only thing I know about all this is that I'd struggle to imagine a better platform for experimenting with heatshield materials and designs than Starship.
Why not?And tractor beams slide right off. Seriously, I don't know how they do it with frying pans but I once worked with a special glue for Teflon. It might have been a precursor to superglue. I was not impressed.
I misremembered reading that Teflon had been used on X-15, though not very successfully. In fact it was something called MA-25S. I do think Teflon has been used before, maybe on early warheads. One potential advantage would be that it ablates cleanly. Or maybe I'm misremembering again.
BTW: this is all theoretical, they probably won't be using spray-on materials even as a temporary expedient.
One should point out that Shuttle lost a lot of tiles after the first few flights, too. NASA was *a lot* more careful with STS-1 and STS-2 than SpaceX has been with Starship hops, obviously, but also it was too late for them to switch. SpaceX has the luxury of being extremely aggressive with early fly-and-try-and-redesign-and-build-and-repeat, so they're able to learn their lesson with ceramic maybe being a bad choice earlier than Shuttle did.
As far as why they didn't just take Shuttle's lessons to heart, well, there's always a certain amount of hubris and naivete when doing a new, grand project like this on an aggressive timescale, and the key is always to be quick to correct mistakes. Sometimes the old wisdom is wrong or obsolete, so sometimes you should just try it (even if 9 times out of 10 the accepted wisdom is right).
Still, as Jeff Greason said, "It's always amazing how six months on the test stand can save you a few hours in the library."
Maybe I'm under thinking it. ISTM a lot of lessons (engineering effort) from an interim less than ideal design would cross over. There is the obvious thermal lessons but issues around the hinges will become much clearer. That's a BIG thing. If the early design is tiles or panels of some sort it teaches how to work with compound curves and attachment points.There is no quick, easy fix for a large and lightweight thermal protection system, reparable or disposable or whathaveyou. It requires careful engineering. Just the way things are in aerospace.Based on your sort of vague description of your idea, either:Philw1776 raised the issue of ablative as a temporary expedient and didn't exactly get shot down but he did get some flak.
One counter was the cost of developing two systems. There is some R&D overlap and reusing a (WAG) $5m ship will pay for a fair chunk of R&D. I actually doubt if it would come in under $10m. An ablative will inform on heat patterns and intensity for a more sophisticated system and may end up as a field repair technique.
Rafael uses 10 tons as the current estimate and another 10-20 tons will not be a a good thing but it is less bad than not flying or flying disposable. I can see this offset mass putting limitations on a landing profile but not driving it into the impossible. There is a lot of control authority in those raptors. Just takes more propellant, and loss of payload capacity. ISTM that getting 50 tons to reusable LEO is better than getting 100 throwaway tons, or worse yet, not flying at all.
On the nuts and bolts end, the stainless substructure hints at a lighter ablative construction than a traditional capsule. The thick insulating honeycomb needed to protect an aluminum shell can be much thinner, and maybe could go away.
AIUI, the Mercury capsule used a resinous material. This suggests that a spray on might work. Removal and replacement after each flight violates the principal of fast turnaround. So what. It's an expedient. Fast turnaround isn't going to show up all at once so any particular launch cadence will demand a fleet pipeline of some particular depth. If heat shield servicing lengthens the turnaround time that pipeline will have to get longer. It isn't as if SX won't have a long term use for a bunch of ships.
It may turn out that the long term fix is already in hand as a contingency plan and will show itself to be more than adequate and economical. If it's not, a less than ideal quick and dirty looks like a good way to get starlink up, nail refueling, gain flight experience, and show progress on HLS.
Here is what I said...
"the option to use a disposable/repairable heat shield EARLY ON in Starship flights exists. SpaceX gets each Starship back for refurbishment for subsequent flight(s) and gets valuable flight data while gradual improvements are made to the heat shield design, OR that particular design approach is abandoned because it cannot lead to eventual re-usability."
Clarification.
I wasn't thinking about ablative, although that is a possibility. Simply suggested a "not ready for full repeated re-use without refurbishment" which some posters took to mean total TPS changeout, ablative, or whatever.
To be more clear, I stand by my stated prediction that minimum viable product re-flights will start out with portions of the heat shield, whatever technology, being disposed/repaired/replaced. And that initial design will evolve to a final design, just like recoverable boosters did, only more rapidly. We've already seen tile attachment designs fail with replacements undoubtedly in the works.
1) It's essentially what they're already doing
or
2) It'll require a bunch of extra engineering.
Just to get it to work a single time takes a LOT of engineering time. So either you're describing their current plan or you're describing almost a doubling of engineering work into their heatshield.
Almost certainly not double. If it were double they would just go straight for the finished/final article. The point being made is that its possible that they will go for a quick and easy method to get to a MVP...
One should point out that Shuttle lost a lot of tiles after the first few flights, too. NASA was *a lot* more careful with STS-1 and STS-2 than SpaceX has been with Starship hops, obviously, but also it was too late for them to switch. SpaceX has the luxury of being extremely aggressive with early fly-and-try-and-redesign-and-build-and-repeat, so they're able to learn their lesson with ceramic maybe being a bad choice earlier than Shuttle did.No hard evidence but the impression I've got is they couldn't get the numbers to work out on everything else and sort of backed into ceramic by default because in theory, the numbers worked. We all know about 'in theory.'
As far as why they didn't just take Shuttle's lessons to heart, well, there's always a certain amount of hubris and naivete when doing a new, grand project like this on an aggressive timescale, and the key is always to be quick to correct mistakes. Sometimes the old wisdom is wrong or obsolete, so sometimes you should just try it (even if 9 times out of 10 the accepted wisdom is right).
Still, as Jeff Greason said, "It's always amazing how six months on the test stand can save you a few hours in the library."
Based on your sort of vague description of your idea, either:Philw1776 raised the issue of ablative as a temporary expedient and didn't exactly get shot down but he did get some flak.
One counter was the cost of developing two systems. There is some R&D overlap and reusing a (WAG) $5m ship will pay for a fair chunk of R&D. I actually doubt if it would come in under $10m. An ablative will inform on heat patterns and intensity for a more sophisticated system and may end up as a field repair technique.
Rafael uses 10 tons as the current estimate and another 10-20 tons will not be a a good thing but it is less bad than not flying or flying disposable. I can see this offset mass putting limitations on a landing profile but not driving it into the impossible. There is a lot of control authority in those raptors. Just takes more propellant, and loss of payload capacity. ISTM that getting 50 tons to reusable LEO is better than getting 100 throwaway tons, or worse yet, not flying at all.
On the nuts and bolts end, the stainless substructure hints at a lighter ablative construction than a traditional capsule. The thick insulating honeycomb needed to protect an aluminum shell can be much thinner, and maybe could go away.
AIUI, the Mercury capsule used a resinous material. This suggests that a spray on might work. Removal and replacement after each flight violates the principal of fast turnaround. So what. It's an expedient. Fast turnaround isn't going to show up all at once so any particular launch cadence will demand a fleet pipeline of some particular depth. If heat shield servicing lengthens the turnaround time that pipeline will have to get longer. It isn't as if SX won't have a long term use for a bunch of ships.
It may turn out that the long term fix is already in hand as a contingency plan and will show itself to be more than adequate and economical. If it's not, a less than ideal quick and dirty looks like a good way to get starlink up, nail refueling, gain flight experience, and show progress on HLS.
Here is what I said...
"the option to use a disposable/repairable heat shield EARLY ON in Starship flights exists. SpaceX gets each Starship back for refurbishment for subsequent flight(s) and gets valuable flight data while gradual improvements are made to the heat shield design, OR that particular design approach is abandoned because it cannot lead to eventual re-usability."
Clarification.
I wasn't thinking about ablative, although that is a possibility. Simply suggested a "not ready for full repeated re-use without refurbishment" which some posters took to mean total TPS changeout, ablative, or whatever.
To be more clear, I stand by my stated prediction that minimum viable product re-flights will start out with portions of the heat shield, whatever technology, being disposed/repaired/replaced. And that initial design will evolve to a final design, just like recoverable boosters did, only more rapidly. We've already seen tile attachment designs fail with replacements undoubtedly in the works.
1) It's essentially what they're already doing
or
2) It'll require a bunch of extra engineering.
Just to get it to work a single time takes a LOT of engineering time. So either you're describing their current plan or you're describing almost a doubling of engineering work into their heatshield.
Excuse my ignorance. Has any work been done on tungsten? I have a memory of using tungsten steel a long time ago. For a metal heat shield I imagine tungsten as being the best material, it is used to make light bulb filaments so can be made into wire. It has a melting point 3410 C. Is there a reason tungsten is not used?
For TPS materials, not only melting point matters, but also weight and thermal conductivity. I think metal foam might be a good candidate. The foamy structure allows the thermal conductivity to be reduced tenfold. There are high melting point alloy / metal foams such as nickel-iron (1400-1450 ° C) or titanium (1668 ° C). In terms of weight, titanium foam is probably the best choice.
https://www.samaterials.com/465-foam-metal
Excuse my ignorance. Has any work been done on tungsten? I have a memory of using tungsten steel a long time ago. For a metal heat shield I imagine tungsten as being the best material, it is used to make light bulb filaments so can be made into wire. It has a melting point 3410 C. Is there a reason tungsten is not used?
For TPS materials, not only melting point matters, but also weight and thermal conductivity. I think metal foam might be a good candidate. The foamy structure allows the thermal conductivity to be reduced tenfold. There are high melting point alloy / metal foams such as nickel-iron (1400-1450 ° C) or titanium (1668 ° C). In terms of weight, titanium foam is probably the best choice.
https://www.samaterials.com/465-foam-metal
Excuse my ignorance. Has any work been done on tungsten? I have a memory of using tungsten steel a long time ago. For a metal heat shield I imagine tungsten as being the best material, it is used to make light bulb filaments so can be made into wire. It has a melting point 3410 C. Is there a reason tungsten is not used?
For TPS materials, not only melting point matters, but also weight and thermal conductivity. I think metal foam might be a good candidate. The foamy structure allows the thermal conductivity to be reduced tenfold. There are high melting point alloy / metal foams such as nickel-iron (1400-1450 ° C) or titanium (1668 ° C). In terms of weight, titanium foam is probably the best choice.
https://www.samaterials.com/465-foam-metal
I really like the idea of foamed titanium (https://www.samaterials.com/foam-metal/1816-titanium-foam.html) with a protective very thin titanium solid metal overlayer (kind of like a metal foam sandwich). Thermal resistance (melting point) of 1670 degC, against a full duration re-entry profile of Tmax of 1400 degC (?) (https://en.m.wikipedia.org/wiki/Titanium_foam)
We use mirror insulation on my site, a thin metal outer sheet (razor sharp edges!) and a concertina folded sheet metal interior or a foamed metal interior (kind of looks "scintered").
From https://forum.nasaspaceflight.com/index.php?topic=50049.msg2042556#msg2042556, total heat shield area should be around 774.72m2. The density quoted at ~0.3 g/cm3 (300 kg/m3) for a total TPS volume of 23.34 m3 (I think this assumed a 3 cm thick tile) leads to a TPS total weight of about 7 tonnes, excluding mounting pins and a very thin metal layer - should be possible for around the original 10 tonne TPS estimate?
Easy to calculate, difficult to test I guess!
Titanium, even remotely close to its melting point is incompatible with oxygen containing air (it's also incompatible with LOX and with few bar oxygen even at room temperature). Data from Columbia disaster has shown higher than expected burn-up of titanium elements. Some titanium pieces almost completely vanished while directly attached aluminum parts remained.
I find it interesting that the place we have seen tile loss is on the engine skirt. Have we seen tiles elsewhere and were they lost?I believe they will fire the engines at sea level when Starship lands retropropulsively.
For the orbital starship they will never fire engines at sea level air pressure. The engines will start for the first time at stage separation. The much lower pressure air will transmit sound at a much lower level and cause much less vibration in the engine skirt. So possibly we are seeing tile loss in an area which wont be a problem with the orbital launches.
EDIT: of course this doesn't account for the vac raptors closer to the skirt.
I find it interesting that the place we have seen tile loss is on the engine skirt. Have we seen tiles elsewhere and were they lost?SN4 had a 7-tile test patch near the bottom of the CH4 tank. It lasted as long as SN4 did...
I find it interesting that the place we have seen tile loss is on the engine skirt. Have we seen tiles elsewhere and were they lost?
For the orbital starship they will never fire engines at sea level air pressure. The engines will start for the first time at stage separation. The much lower pressure air will transmit sound at a much lower level and cause much less vibration in the engine skirt. So possibly we are seeing tile loss in an area which wont be a problem with the orbital launches.
EDIT: of course this doesn't account for the vac raptors closer to the skirt.
Anyway, they also put some test heat shield tiles on hopper, which, IIRC, were just fine after the test.
Titanium, even remotely close to its melting point is incompatible with oxygen containing air (it's also incompatible with LOX and with few bar oxygen even at room temperature). Data from Columbia disaster has shown higher than expected burn-up of titanium elements. Some titanium pieces almost completely vanished while directly attached aluminum parts remained.
So I looked a bit more at those studies I references earlier on metallic heatshields.So did I. Thanks for finding those.
For the people talking about materials, niobium (previously known as columbium) with a ceramic-oxide coating seems to be a great candidate.
Reading this, I'm now kind of curious why NASA went with the ceramic tiles for the Shuttle. The results from this testing sounds very promising.
https://ntrs.nasa.gov/citations/19730024093
This study looked primarily at honeycomb structures, particularly titanium and Inconel. Someone mentioned metal foam earlier and I wonder if that would work in the same way.
https://ntrs.nasa.gov/citations/20040095922
Both studies also did lots of stress testing on the tiles outside of just simulated reentries.
I misremembered reading that Teflon had been used on X-15, though not very successfully. In fact it was something called MA-25S. I do think Teflon has been used before, maybe on early warheads. One potential advantage would be that it ablates cleanly. Or maybe I'm misremembering again.I can't recall the reference (may have been a early Apollo radome) but Teflon has been used as an ablator and on some reentry vehicles. It burns off clean but it's burn off temperature is quite low, about 400c IIRC>
BTW: this is all theoretical, they probably won't be using spray-on materials even as a temporary expedient.
Was that heavy pin pattern, on SN8 or 9, I try find it again at update thread but it is bit too dense.
[Edit] Ok, Mary's photo of SN8 have a tri-pin pattern but I don't see pins. Do they test stud welds effect to the skin of the ship? And the pin picture part is for SN9. (?)
https://forum.nasaspaceflight.com/index.php?topic=51332.1420
https://twitter.com/cnunezimages/status/1309125893097480197QuoteSN8 Aft Flap / Up close Pano / Click to Expand -
@elonmusk #bocachicatomars #SN8 #SpaceX #iCANimagine LLC @SpaceIntellige3
- CNunezIMAGES.com
There is no way in hell that you can attach TPS to such a surface. Most probably another expedient stand in for testing.I'm half expecting another big surprise with the fins. Since they're not pressurized or protecting delicate stuff inside, it seems like you wouldn't want to use the same scheme the tanks will.
John
There is no way in hell that you can attach TPS to such a surface. Most probably another expedient stand in for testing.I'm half expecting another big surprise with the fins. Since they're not pressurized or protecting delicate stuff inside, it seems like you wouldn't want to use the same scheme the tanks will.
John
There is no way in hell that you can attach TPS to such a surface. Most probably another expedient stand in for testing.I'm half expecting another big surprise with the fins. Since they're not pressurized or protecting delicate stuff inside, it seems like you wouldn't want to use the same scheme the tanks will.
John
It looks like a thin crooked cookie sheet
The leading side could be much different than the trailing size. It would seem that it could be thinner toward the outer edge as well, the fins look kind of fat.
Just gotta start flying and iterating.
https://twitter.com/cnunezimages/status/1309125893097480197QuoteSN8 Aft Flap / Up close Pano / Click to Expand -
@elonmusk #bocachicatomars #SN8 #SpaceX #iCANimagine LLC @SpaceIntellige3
- CNunezIMAGES.com
There is no way in hell that you can attach TPS to such a surface. Most probably another expedient stand in for testing.
John
The fins appear to be another expedient prototype for testing. No way you can attach TPS to those panels. They will have to either go to honeycomb or fluted/corrugated surface (ala SR-71) panels to keep them from oil canning. They could do the tops with wrinkles, but not the bottoms.
John
https://twitter.com/cnunezimages/status/1309125893097480197QuoteSN8 Aft Flap / Up close Pano / Click to Expand -
@elonmusk #bocachicatomars #SN8 #SpaceX #iCANimagine LLC @SpaceIntellige3
- CNunezIMAGES.com
There is no way in hell that you can attach TPS to such a surface. Most probably another expedient stand in for testing.
John
The fins appear to be another expedient prototype for testing. No way you can attach TPS to those panels. They will have to either go to honeycomb or fluted/corrugated surface (ala SR-71) panels to keep them from oil canning. They could do the tops with wrinkles, but not the bottoms.
John
The fins appear to be another expedient prototype for testing. No way you can attach TPS to those panels. They will have to either go to honeycomb or fluted/corrugated surface (ala SR-71) panels to keep them from oil canning. They could do the tops with wrinkles, but not the bottoms.
John
Thinking about that a bit deeper: an airtight skin under the TPS has no real purpose (other than providing a mounting surface for the TPS). So they might try to integrate those functions/eliminate the skin completely. A grid like support structure with a bit more sturdy tiles or whatever.
If they do so, what we see now is a coplete dead end/strictly temporary solution.
Hopper was more like 14mm.Anyway, they also put some test heat shield tiles on hopper, which, IIRC, were just fine after the test.
So that points to the skirt being too "flimsy". Hopper was what 10 mm? starship is 4 mm.
Also hopper had longer legs.
The fins appear to be another expedient prototype for testing. No way you can attach TPS to those panels. They will have to either go to honeycomb or fluted/corrugated surface (ala SR-71) panels to keep them from oil canning. They could do the tops with wrinkles, but not the bottoms.Is there a chance there won't be any TPS -tiles- on the fins? Just the starship body and wing root covers?
John
Maybe they plan to make the flaps from inconel or similar?The main tank has to be there to contain the propellants, but does there need to be a continuous surface under the fins heat shield? Wouldn't an open framework of attachment points work?
The flaps for all suborbital testing might just need the right shape for now.
And the big differences between the main body and the flaps are that the surface doesnt need to bear all forces, and does not experience cryogenic temperatures.
Maybe just a thin layer of inconel on some kind of felt, on top of a stainless steel structure?
Maybe they plan to make the flaps from inconel or similar?The main tank has to be there to contain the propellants, but does there need to be a continuous surface under the fins heat shield? Wouldn't an open framework of attachment points work?
The flaps for all suborbital testing might just need the right shape for now.
And the big differences between the main body and the flaps are that the surface doesnt need to bear all forces, and does not experience cryogenic temperatures.
Maybe just a thin layer of inconel on some kind of felt, on top of a stainless steel structure?
Maybe they plan to make the flaps from inconel or similar?The main tank has to be there to contain the propellants, but does there need to be a continuous surface under the fins heat shield? Wouldn't an open framework of attachment points work?
The flaps for all suborbital testing might just need the right shape for now.
And the big differences between the main body and the flaps are that the surface doesnt need to bear all forces, and does not experience cryogenic temperatures.
Maybe just a thin layer of inconel on some kind of felt, on top of a stainless steel structure?
It seems like an open grid would allow superheated air to enter and overheat the structure.
Here's an interesting comment on metallic heatshields from /u/flshr19 on reddit:
QuoteReusable metallic heat shields have been a holy grail in TPS technology since I first started working in that area during the Space Shuttle conceptual design period (1969-late 1971). My lab developed prototype metallic heat shields fabricated from niobium (aka columbium) coated with various ceramic oxides for increased oxidation resistance. We tested them up to 3000F (1649C) in specialized furnaces at air pressures typical of entry into the Earth's atmosphere. Mechanical tension and flexing loads were applied during these tests to determine the adhesion characteristics of the coatings. These samples could do a hundred simulated Shuttle entries without losing the coating.
See https://ntrs.nasa.gov/citations/19730024093
Nearly 25 years later in 1995 I worked on a NASA Langley contract to develop metallic heat shields for the X-33.
https://ntrs.nasa.gov/citations/20040095922
Interest in metallic heat shields has run hot and cold for the past 50 years. Maybe SpaceX can find a use for some of the previous work and develop a metallic heat shield that actually flies on a real spacecraft.
Comment source: https://www.reddit.com/r/spacex/comments/inkzwp/starship_development_thread_14/g5v3786/
One of my questions reading the paper was how the weight of the niobium alloy panels compares to the weight of a ceramic tile. I'm still not sure of the answer, but it sounds like it might be lighter.
Thermal protection system design involves balancing a whole bunch of variables to to deliver multiple constraints.
Now look at material densities in terms of specific gravity relative to water.
Silica at 100% of theoretical density 2.65
Niobium 8.5
Molybdenum 10.56
Tantalum 12
Tungsten 20
And the Silica tiles were 95% air.
To do as well you'd have to build those panels out of very thin material. The ones that Rohr delivered to the X33 programme were foil thickness, rather than what most people think of as sheet. :(
The problem with flaps is not heating so much but airflow leakage through the hinge from the lower to the upper surface. That needs AFAP an air tight seal.
The starship body will provide the vast majority of the braking force on reentry. During peak heat load, The fins could be swept back extremely far to the point where the steel structure would be sufficient. We know the leeward side won't have tiles TPS after all. Even swept back to being nearly parallel to airstream should provide some control authority.
After peak heating they could be gradually extended into the airstream to provide greater deceleration and control.
Even if it is determined that the fins can not survive without -any- TPS, a different type of TPS could be used, such as an ablative coating designed to last dozens of flights.It's a reasonable idea.
Refurbishment of consumable TPS on flaps alone could be done off the vehicle. If a flap is getting towards the end of useful life, swap it out. Starships keep flying and send the old flap back for refurbishment.
All good points, thanks.The problem with flaps is not heating so much but airflow leakage through the hinge from the lower to the upper surface. That needs AFAP an air tight seal.
The starship body will provide the vast majority of the braking force on reentry. During peak heat load, The fins could be swept back extremely far to the point where the steel structure would be sufficient. We know the leeward side won't have tiles TPS after all. Even swept back to being nearly parallel to airstream should provide some control authority.
After peak heating they could be gradually extended into the airstream to provide greater deceleration and control.
Very large seal x very high temperature --> Massive PITA
At high altitudes air is so thin you can use Newton's model of air, which is like light beams. So imagine the airflow is a light source and see which parts of a model are (literally) in shadow.
The problems are at the leading edges of any structure in the airflow. That's where the air slows down and dumps its heat.
BTW the Shuttle rudder (at around a 45 deg entry angle to the flow) was mostly ineffective and the pilot had to rely on RCS authority until they were relatively low in the atmosphere. Projects had looked at a V tail to improve this. If SS is coming in steeper any surface in shadow will have less control authority.Quote from: AstroWareEven if it is determined that the fins can not survive without -any- TPS, a different type of TPS could be used, such as an ablative coating designed to last dozens of flights.It's a reasonable idea.
Refurbishment of consumable TPS on flaps alone could be done off the vehicle. If a flap is getting towards the end of useful life, swap it out. Starships keep flying and send the old flap back for refurbishment.
As a general point I'll note the issues with coatings shown up by the gold coating of the SSME turbine blades.
The coating has to be perfect or the underlying material will start to be attacked immediately
The coating has to be inspected regularly to make sure it has not been damaged.
If damaged a process must exist for the coating to be either a)Stripped off or b) "Touched up" without damaging the part (or in the case of a touch up weakening the rest of the coating)
The ideal solution is find an underlying material that does not need a coating at all. :)
Failing that the ideal coating is one that is impossible to damage under the exposure conditions throughout its life.
In principle that eliminate all the inspection, stripping, re-coating issues in one move. Lifetime protection.
Finding such a coating (depending on the process conditions involved) that meets all of the actual requirements, can be quite difficult.
As for the hinge, the wing roots could be designed so that they extend beyond the hinge so the hinge is always in "shadow". May still have to deal against indirect airflow, but that should be easier then being in the main flow.
Then the "leading edge" of the body flaps is nearly parallel to the airstream, and somewhere along the flap surface instead of the hinge.
(Warning poor sketch ahead )
(https://uploads.tapatalk-cdn.com/20200925/84fa265b21d63ecc96e78a5a973017cd.jpg)
As for the hinge, the wing roots could be designed so that they extend beyond the hinge so the hinge is always in "shadow". May still have to deal against indirect airflow, but that should be easier then being in the main flow.
Then the "leading edge" of the body flaps is nearly parallel to the airstream, and somewhere along the flap surface instead of the hinge.
(Warning poor sketch ahead )
(https://uploads.tapatalk-cdn.com/20200925/84fa265b21d63ecc96e78a5a973017cd.jpg)
That is a very fine sketch.
I disagree. This is s good sketch. :)
Wouldn't the starship flaps act more like a V-tail then the Shuttle vertical stabilizer? The shuttle stabilizer was far away from the airstream, whereas the starship body flaps are tangential. Using the shadow analogy, body flaps seem much more likely to have an effect earlier. Enough control? No idea. But starship will also have an RCS system. It would seem like a good trade study to look at reducing TPS on the fins by using RCS.
As for the hinge, the wing roots could be designed so that they extend beyond the hinge so the hinge is always in "shadow". May still have to deal against indirect airflow, but that should be easier then being in the main flow.
Then the "leading edge" of the body flaps is nearly parallel to the airstream, and somewhere along the flap surface instead of the hinge.
(Warning poor sketch ahead )
(https://uploads.tapatalk-cdn.com/20200925/84fa265b21d63ecc96e78a5a973017cd.jpg)
It appears that SpaceX has solidified some of the heat shield processes for Starship. New equipment has been added to the Cape Canaveral facility with evidence of more to come. Similar tanks were seen at Cidco Rd indicating some processes may occur there as well. #Starship
Coima builds dust-collectors and filtration systems, mainly for woodworking industry. Does mass-production of silica tiles emit dust? Or are they going back to the PICA-X (-3)?QuoteIt appears that SpaceX has solidified some of the heat shield processes for Starship. New equipment has been added to the Cape Canaveral facility with evidence of more to come. Similar tanks were seen at Cidco Rd indicating some processes may occur there as well. #Starship
Depends if the tiles are baked to near net shape or if they are baked in bigger pieces and cut into sections, and of course how much final machining each section gets.Coima builds dust-collectors and filtration systems, mainly for woodworking industry. Does mass-production of silica tiles emit dust? Or are they going back to the PICA-X (-3)?QuoteIt appears that SpaceX has solidified some of the heat shield processes for Starship. New equipment has been added to the Cape Canaveral facility with evidence of more to come. Similar tanks were seen at Cidco Rd indicating some processes may occur there as well. #Starship
All good points, thanks.True. The classic trade is Bigger flaps --> more control authority --> less RCS propellant usage.
Wouldn't the starship flaps act more like a V-tail then the Shuttle vertical stabilizer? The shuttle stabilizer was far away from the airstream, whereas the starship body flaps are tangential. Using the shadow analogy, body flaps seem much more likely to have an effect earlier. Enough control? No idea. But starship will also have an RCS system. It would seem like a good trade study to look at reducing TPS on the fins by using RCS.
As for the hinge, the wing roots could be designed so that they extend beyond the hinge so the hinge is always in "shadow". May still have to deal against indirect airflow, but that should be easier then being in the main flow.You draw a fair hand. CAD is great for changes to a design but somewhat excessive for early work, along with the discipline needed to translate into "CADese"
Then the "leading edge" of the body flaps is nearly parallel to the airstream, and somewhere along the flap surface instead of the hinge.
https://twitter.com/julia_bergeron/status/1309617081181233153Maybe we can get *Julia to take photos of warning labels (or lack of them)?QuoteIt appears that SpaceX has solidified some of the heat shield processes for Starship. New equipment has been added to the Cape Canaveral facility with evidence of more to come. Similar tanks were seen at Cidco Rd indicating some processes may occur there as well. #Starship
Maybe we can get Julia to take photos of warning labels (or lack of them)?Wholia?
The problem with flaps is not heating so much but airflow leakage through the hinge from the lower to the upper surface. That needs AFAP an air tight seal.
The starship body will provide the vast majority of the braking force on reentry. During peak heat load, The fins could be swept back extremely far to the point where the steel structure would be sufficient. We know the leeward side won't have tiles TPS after all. Even swept back to being nearly parallel to airstream should provide some control authority.
After peak heating they could be gradually extended into the airstream to provide greater deceleration and control.
Very large seal x very high temperature --> Massive PITA
At high altitudes air is so thin you can use Newton's model of air, which is like light beams. So imagine the airflow is a light source and see which parts of a model are (literally) in shadow.
The problems are at the leading edges of any structure in the airflow. That's where the air slows down and dumps its heat.
The problem with flaps is not heating so much but airflow leakage through the hinge from the lower to the upper surface. That needs AFAP an air tight seal.
I don't understand why airflow leakage to the upper surface is a problem. If this aerosurface were a flap for a wing meant to generate lift, I get that you need a low pressure region behind the upper surface. But the elonerons (flings? call them what you will) are drag surfaces.Welcome to the site. Cal them what you like. I quite like Elorons. They are designed to exert a force on the vehicle. When high speed air flow is slowed down it gets hot. Under ordinary entry conditions that from 7800m/s to zero. From mars it will be much higher.
SS obviously can't have thermal heating in the hinge area or near it on the upper surface, so some amount of a seal combined with cold gas injection at high pressure will help. But it's not clear to me why an air tight seal is important for SS. You could just extend the aerosurface out by a fraction of a degree more to compensate for any lost drag due to air leakage through the hinge. If that simplifies the design of the seal, it seems it would be well worth it.The honest answer is it may not be.
Can you explain for novices like me? Thanks!
The problem with flaps is not heating so much but airflow leakage through the hinge from the lower to theWe certainly will.
Elon himself proposed purging the hinge area with gas, to exclude hot gas from entering.
https://twitter.com/elonmusk/status/1228400791880269824
I believe this, combined with the geometry detailed in AstroWare's excellent diagram, will be the ultimate solution.
....
I think the key issue shown in Astorware's diagram is wheather they are limited to being no more than 90deg to the body. If so you can keep the actual hinges out of direct airflow.
I don't understand why airflow leakage to the upper surface is a problem. If this aerosurface were a flap for a wing meant to generate lift, I get that you need a low pressure region behind the upper surface. But the elonerons (flings? call them what you will) are drag surfaces.Welcome to the site. Cal them what you like. I quite like Elorons. They are designed to exert a force on the vehicle. When high speed air flow is slowed down it gets hot. Under ordinary entry conditions that from 7800m/s to zero. From mars it will be much higher.
The issues are pressure leaks mean a less effective surface. Bigger surface --> more mass to carry to mars and back. And remember Musk didn't want any surfaces like this to begin with.
Hot air flow also attacks the attachment points for those surfaces and the associated actuator hardware driving them, which will be working pretty hard.
So what's easier? Harden the area around the pivot and drive or stop the airflow from getting there int eh first place?Quote from: OvertoneSS obviously can't have thermal heating in the hinge area or near it on the upper surface, so some amount of a seal combined with cold gas injection at high pressure will help. But it's not clear to me why an air tight seal is important for SS. You could just extend the aerosurface out by a fraction of a degree more to compensate for any lost drag due to air leakage through the hinge. If that simplifies the design of the seal, it seems it would be well worth it.The honest answer is it may not be.
Can you explain for novices like me? Thanks!
Like a lot of these design questions the devils in the details. :( Avoiding the problem (of hot airflow leakage) opens up your choice of materials for the pivot and actuator area and should cut your cooling requirements to those areas.
OTOH hardening those areas and swallowing the increased surface area may be the lighter option.
I think SX have run (and will continue to run) a lot of simulations in this area to balance surface mass, TPS mass, coolant mass and RCS propellant mass.
And some of those masses are "better" than others. Propellants and coolants could be made at mars and reloaded but hardware has to be carried all the way to mars and back.
Never forget SS is an upper stage.
Every unit of mass added to the structure (or propellant assigned to RCS, OMS or landing) means 1 unit off the payload.
On a booster 1 unit of additional booster mass cuts the payload (IE the US mass) by between 1/6 and 1/13 of that unit).
I don't there is the option of counting on folding the fins back during re-entry. The fins may need to be extended out to compensate for where the Center of Mass ends up. The fins need to both give control and to compensate for adjusting center of drag to the center of mass, and the center of mass may end up in quite a large range depending on payload etc.Exactly. Depending on the center of mass, a re-entry could in theory happen with the fins fully extended or completely folded. (Or anywhere in between) Which does make the joints a very critical part of the TPS design.
- Flaps will have to extend for control, so they will be protected by TPS.Exactly.
- SpaceX can keep the hinges out of the direct flow as shown in Astorware's sketch of the fairing, but you cannot keep the hinge out of the indirect air that will expand (Prandtl Meyer expansion) into the hinge area.
John
I'm a bit adrift here. Harking back to AstroWare's pic and with subsonic speeds, I would expect any local flow across the hinge gap to cause low pressure and suction at the gap, not flow into it. At hypersonic speeds I'd expect the hot (but not killer hot) surface flow within the shock wave standoff to do something similar. Or is it killer hot and I'm also missing something? Wouldn't be the first time.A couple of things. The straight line Newton approximation is for very low pressure in the high atmosphere. As atmospheric density rises there is a huge increase in the interactions between air molecules and Prandtl–Meyer expansion (https://en.wikipedia.org/wiki/Prandtl%E2%80%93Meyer_expansion_fan) develops as the flows comes round that corner, filling up that triangular shaped space with hot air to push through the gap.
Perhaps this has been discussed and I didn't realize it as there has been terminology I'm not familiar with.
[snip]
Ideally you slowly lose most of your velocity in the high atmosphere then glide down to earth at sub mach speeds. This is unworkable because the wing area needed to keep a vehicle in orbit by winged lift alone at these altitudes would be huge.
[snip]
Ideally you slowly lose most of your velocity in the high atmosphere then glide down to earth at sub mach speeds. This is unworkable because the wing area needed to keep a vehicle in orbit by winged lift alone at these altitudes would be huge.
Not quite decelerating to subsonic speeds, but ISTM a mild version of this is what was meant by the Dragon wing idea Musk was toying with earlier. Large surface area hot metal TPS. Large single-layer stainless skin to minimizes mass-per-area and radiate heat from both sides (the dragon wing "membrane"), structurally supported by periodic ribs (the dragon wing "fingers").
High lift to drag and modest peak heating means it can bleed of speed high in Earth's atmosphere for a nice gentle reentry heating profile. On Mars it has plenty of lift so it can aerocapture at a reasonably high altitude and low heating rate, increasing landed mass and/or allowing for faster Mars transits.
Ultimately they went with the current ceramic tile TPS, but if that TPS solution becomes a delaying factor the hot metal Dragon wing TPS could swing back to 51% and suddenly become the new "plan of record."
https://twitter.com/elonmusk/status/1117563679099240449?lang=en
Using the numbers for SS304 (SG 7.805) and shim thickness of 0.1mm (4 mils) gives you about 128 m^2 for a 100Kg (not including the deployment mechanism or ribs). Let's say that adds 25Kg. Or 0.78125kg/m^2
Not quite decelerating to subsonic speeds, but ISTM a mild version of this is what was meant by the Dragon wing idea Musk was toying with earlier. Large surface area hot metal TPS. Large single-layer stainless skin to minimizes mass-per-area and radiate heat from both sides (the dragon wing "membrane"), structurally supported by periodic ribs (the dragon wing "fingers").
High lift to drag and modest peak heating means it can bleed of speed high in Earth's atmosphere for a nice gentle reentry heating profile. On Mars it has plenty of lift so it can aerocapture at a reasonably high altitude and low heating rate, increasing landed mass and/or allowing for faster Mars transits.
IMHO Starship TPS development is the "Grand Challenge" of TPS this decade. It will (if it has not already done so) attract the most qualified TPS developers, and whoever leads it will be the goto person for TPS development for a decade afterward.What really intrigues me about this idea is that SpaceX have also already demonstrated two things about Starship development...
[snip]
Ideally you slowly lose most of your velocity in the high atmosphere then glide down to earth at sub mach speeds. This is unworkable because the wing area needed to keep a vehicle in orbit by winged lift alone at these altitudes would be huge.
Not quite decelerating to subsonic speeds, but ISTM a mild version of this is what was meant by the Dragon wing idea Musk was toying with earlier. Large surface area hot metal TPS. Large single-layer stainless skin to minimizes mass-per-area and radiate heat from both sides (the dragon wing "membrane"), structurally supported by periodic ribs (the dragon wing "fingers").
High lift to drag and modest peak heating means it can bleed of speed high in Earth's atmosphere for a nice gentle reentry heating profile. On Mars it has plenty of lift so it can aerocapture at a reasonably high altitude and low heating rate, increasing landed mass and/or allowing for faster Mars transits.
Ultimately they went with the current ceramic tile TPS, but if that TPS solution becomes a delaying factor the hot metal Dragon wing TPS could swing back to 51% and suddenly become the new "plan of record."
https://twitter.com/elonmusk/status/1117563679099240449?lang=en
This is one reason I personally prefer "Dragging Wings" to "Elonerons."
But traditional aviation flaps are exactly not drag surfaces.[snip]
Ideally you slowly lose most of your velocity in the high atmosphere then glide down to earth at sub mach speeds. This is unworkable because the wing area needed to keep a vehicle in orbit by winged lift alone at these altitudes would be huge.
Not quite decelerating to subsonic speeds, but ISTM a mild version of this is what was meant by the Dragon wing idea Musk was toying with earlier. Large surface area hot metal TPS. Large single-layer stainless skin to minimizes mass-per-area and radiate heat from both sides (the dragon wing "membrane"), structurally supported by periodic ribs (the dragon wing "fingers").
High lift to drag and modest peak heating means it can bleed of speed high in Earth's atmosphere for a nice gentle reentry heating profile. On Mars it has plenty of lift so it can aerocapture at a reasonably high altitude and low heating rate, increasing landed mass and/or allowing for faster Mars transits.
Ultimately they went with the current ceramic tile TPS, but if that TPS solution becomes a delaying factor the hot metal Dragon wing TPS could swing back to 51% and suddenly become the new "plan of record."
https://twitter.com/elonmusk/status/1117563679099240449?lang=en
This is one reason I personally prefer "Dragging Wings" to "Elonerons."
I guess I'm the only one who prefers to call them what Elon Musk chooses to calls them: "body flaps."
They're flaps (deployable drag structures). They're on the body, not the wing. Body flaps.
But traditional aviation flaps are exactly not drag surfaces.[snip]
Ideally you slowly lose most of your velocity in the high atmosphere then glide down to earth at sub mach speeds. This is unworkable because the wing area needed to keep a vehicle in orbit by winged lift alone at these altitudes would be huge.
Not quite decelerating to subsonic speeds, but ISTM a mild version of this is what was meant by the Dragon wing idea Musk was toying with earlier. Large surface area hot metal TPS. Large single-layer stainless skin to minimizes mass-per-area and radiate heat from both sides (the dragon wing "membrane"), structurally supported by periodic ribs (the dragon wing "fingers").
High lift to drag and modest peak heating means it can bleed of speed high in Earth's atmosphere for a nice gentle reentry heating profile. On Mars it has plenty of lift so it can aerocapture at a reasonably high altitude and low heating rate, increasing landed mass and/or allowing for faster Mars transits.
Ultimately they went with the current ceramic tile TPS, but if that TPS solution becomes a delaying factor the hot metal Dragon wing TPS could swing back to 51% and suddenly become the new "plan of record."
https://twitter.com/elonmusk/status/1117563679099240449?lang=en
This is one reason I personally prefer "Dragging Wings" to "Elonerons."
I guess I'm the only one who prefers to call them what Elon Musk chooses to calls them: "body flaps."
They're flaps (deployable drag structures). They're on the body, not the wing. Body flaps.
Speed brakes are. Located in different places and operate very differently.
You can skip the aviation analogy all together and say they're flaps in the "uneducated" simple English literal sense of the word, as if you're naming them from scratch. "Flaps" because they flap. No relation to airplane flaps.
Flaps extend the trailing edge, flow continues across them and remains attached, in fact the flaps allow the wing to increase the AoA without flow separation. The added drag is "lift drag".But traditional aviation flaps are exactly not drag surfaces.
This is one reason I personally prefer "Dragging Wings" to "Elonerons."
I guess I'm the only one who prefers to call them what Elon Musk chooses to calls them: "body flaps."
They're flaps (deployable drag structures). They're on the body, not the wing. Body flaps.
Speed brakes are. Located in different places and operate very differently.
You can skip the aviation analogy all together and say they're flaps in the "uneducated" simple English literal sense of the word, as if you're naming them from scratch. "Flaps" because they flap. No relation to airplane flaps.
Flaps on aircraft are intended to increase lift. They do also increase drag, but that it is not a problem at low speeds where they are used. A flap is basically the same as a retractable wing, but viewed from the opposite direction.
The body flaps on Starship would also increase lift, as well as drag, depending on angle of attack. AIUI at the angle of entry of Starship, it's a bit moot, lift and drag are acting in the same direction.
.... AIUI at the angle of entry of Starship, it's a bit moot, lift and drag are acting in the same direction.
.... AIUI at the angle of entry of Starship, it's a bit moot, lift and drag are acting in the same direction.
By definition, lift is always perpendicular to drag.
John
We're drifting, but even though "lift is lift", there's a fundamental difference between lift that's cause by differences in attached flow on either side of a surface (wing, flap) and lift that's generated by kinetic momentum change of the air (brakes, simple kites, barn doors).... AIUI at the angle of entry of Starship, it's a bit moot, lift and drag are acting in the same direction.
By definition, lift is always perpendicular to drag.
John
Also, Starship spends the majority of hypersonic reentry into the atmosphere at ~60 degree AoA, where the body flaps are certainly producing both lift and drag.
It's only in the transonic/subsonic descent stage where it's falling straight down at 90 degrees AoA (skydiver mode) that the flaps do not produce any net lift.
We're drifting, but even though "lift is lift", there's a fundamental difference between lift that's cause by differences in attached flow on either side of a surface (wing, flap) and lift that's generated by kinetic momentum change of the air (brakes, simple kites, barn doors)
The end result is similar, but the mechanism in which it is produced is fundamentally important.We're drifting, but even though "lift is lift", there's a fundamental difference between lift that's cause by differences in attached flow on either side of a surface (wing, flap) and lift that's generated by kinetic momentum change of the air (brakes, simple kites, barn doors)
Nah, lift in both cases is generated by imparting momentum to the air in the opposite direction of your lift vector.
I think that collector is for PICA production but it's not for SS, It's speed-run iteration and re-qualification for Crew Dragon heat shield.Coima builds dust-collectors and filtration systems, mainly for woodworking industry. Does mass-production of silica tiles emit dust? Or are they going back to the PICA-X (-3)?QuoteIt appears that SpaceX has solidified some of the heat shield processes for Starship. New equipment has been added to the Cape Canaveral facility with evidence of more to come. Similar tanks were seen at Cidco Rd indicating some processes may occur there as well. #Starship
....
The two cases are distinguishable, inherently - you can look at the airflow around a flap and a brake and tell which is which, even without checking the part number...
Well at a high AoA the entire wing will stall too, right?....
The two cases are distinguishable, inherently - you can look at the airflow around a flap and a brake and tell which is which, even without checking the part number...
A flap at high AoA, say greater than 45 degrees, is completely separated on the leeward side. It is producing both lift and drag. How is this fundamentally different than the SS body flap?
John
Well at a high AoA the entire wing will stall too, right?....
The two cases are distinguishable, inherently - you can look at the airflow around a flap and a brake and tell which is which, even without checking the part number...
A flap at high AoA, say greater than 45 degrees, is completely separated on the leeward side. It is producing both lift and drag. How is this fundamentally different than the SS body flap?
John
But the purpose of the flap is to allow the flow to remain attached at higher AoAs (and lower speeds) than would otherwise be possible.
The purpose of the SS control surfaces is to operate like brakes - stick out into the flow with no intention of having it attached. If there's lift generated it is simply because they're not at 90 degrees, but absence of any type of lift was not the criteria.
The difference between flaps and brakes is not whether they generate any kind of lift, but how the air is supposed to behave around them.
In an airplane. Which starship is not.
So why not stop trying to justify the name based on airplane analogies? They don't work, and it doesn't matter, since this is not an airplane.
We're drifting, but even though "lift is lift", there's a fundamental difference between lift that's cause by differences in attached flow on either side of a surface (wing, flap) and lift that's generated by kinetic momentum change of the air (brakes, simple kites, barn doors).... AIUI at the angle of entry of Starship, it's a bit moot, lift and drag are acting in the same direction.
By definition, lift is always perpendicular to drag.
John
Also, Starship spends the majority of hypersonic reentry into the atmosphere at ~60 degree AoA, where the body flaps are certainly producing both lift and drag.
It's only in the transonic/subsonic descent stage where it's falling straight down at 90 degrees AoA (skydiver mode) that the flaps do not produce any net lift.
Hey good point about his being the wrong thread.. quote this elsewhere (where?) To continue there...We're drifting, but even though "lift is lift", there's a fundamental difference between lift that's cause by differences in attached flow on either side of a surface (wing, flap) and lift that's generated by kinetic momentum change of the air (brakes, simple kites, barn doors).... AIUI at the angle of entry of Starship, it's a bit moot, lift and drag are acting in the same direction.
By definition, lift is always perpendicular to drag.
John
Also, Starship spends the majority of hypersonic reentry into the atmosphere at ~60 degree AoA, where the body flaps are certainly producing both lift and drag.
It's only in the transonic/subsonic descent stage where it's falling straight down at 90 degrees AoA (skydiver mode) that the flaps do not produce any net lift.
In hypersonic regime the "kite lift" is the primary lift as compression in front of the wing dominates any effects from underpressure behind it (this also indicates/explains why hypersonic L:D almost invariably sucks).
It's Elon's game and he gets to call things whatever he wants but fins is only four characters. If anybody comes across me referring to SS fins, I'm using shorthand for body flaps.[snip]
Ideally you slowly lose most of your velocity in the high atmosphere then glide down to earth at sub mach speeds. This is unworkable because the wing area needed to keep a vehicle in orbit by winged lift alone at these altitudes would be huge.
Not quite decelerating to subsonic speeds, but ISTM a mild version of this is what was meant by the Dragon wing idea Musk was toying with earlier. Large surface area hot metal TPS. Large single-layer stainless skin to minimizes mass-per-area and radiate heat from both sides (the dragon wing "membrane"), structurally supported by periodic ribs (the dragon wing "fingers").
High lift to drag and modest peak heating means it can bleed of speed high in Earth's atmosphere for a nice gentle reentry heating profile. On Mars it has plenty of lift so it can aerocapture at a reasonably high altitude and low heating rate, increasing landed mass and/or allowing for faster Mars transits.
Ultimately they went with the current ceramic tile TPS, but if that TPS solution becomes a delaying factor the hot metal Dragon wing TPS could swing back to 51% and suddenly become the new "plan of record."
https://twitter.com/elonmusk/status/1117563679099240449?lang=en (https://twitter.com/elonmusk/status/1117563679099240449?lang=en)
This is one reason I personally prefer "Dragging Wings" to "Elonerons."
I guess I'm the only one who prefers to call them what Elon Musk chooses to calls them: "body flaps."
They're flaps (deployable drag structures). They're on the body, not the wing. Body flaps.
Before launch I would expect some flapping... :)
Edit: if I'm in an expansive mood I may waste a character and call them flaps - even if they don't flap. They don't do that, do they? ::)Isn't it generally considered a really bad sign (at least in aerospace) if your flaps are flapping?
No? For example, when plummeting like a stone, lift and drag are collinear. In fact, they're the same force..... AIUI at the angle of entry of Starship, it's a bit moot, lift and drag are acting in the same direction.
By definition, lift is always perpendicular to drag.
John
It's not. The entire purpose of a flap is to keep airflow attached to the leeward side of the wing by allowing some of the high pressure air under the wing to energize the low pressure side. That allows the wing to operate at a higher angle of attack, and produce more lift before stalling. It also causes the wing to produce more drag.....
The two cases are distinguishable, inherently - you can look at the airflow around a flap and a brake and tell which is which, even without checking the part number...
A flap at high AoA, say greater than 45 degrees, is completely separated on the leeward side. It is producing both lift and drag. How is this fundamentally different than the SS body flap?
John
No? For example, when plummeting like a stone, lift and drag are collinear. In fact, they're the same force..... AIUI at the angle of entry of Starship, it's a bit moot, lift and drag are acting in the same direction.
By definition, lift is always perpendicular to drag.
John
I think we need the lift a heatshield sighting would impart. The lack of it is really dragging this thread down.I think you're creating a flap.
A thin Carbon/SiC composite shell is good to ~1600 C. Metals cannot compete. Fill the shell with insulation and mechanically attach.
John
Welcome to the site.
hi I'm new to the forum, I found this document on the subject space heat material:
https://www.researchgate.net/publication/227221472_Carbon_Fibre_Reinforced_Silicon_Carbide_Composites_CSiC_CC-SiC
A thin Carbon/SiC composite shell is good to ~1600 C. Metals cannot compete. Fill the shell with insulation and mechanically attach.That sounds like a single use temperature rather than cyclic to me.
John
I tried Googling for Carbon/SiC composites and the closest I got was this:This stuff is for use in vacuum furnaces. I'm guessing the issue is miss match of TCE causes cracking of the skin and exposure of the graphite, at which point the graphite becomes "Designer coal." :(
https://www.sglcarbon.com/en/markets-solutions/material/sigrasic-carbon-fiber-reinforced-silicon-carbide/
Working temperature in vacuum/inert gas of 1200 degC, in oxygen 450 degC, which probably means it really doesn't like oxidation, and doesn't form a passivization layer.
Any example data sheets we could look at?
A thin Carbon/SiC composite shell is good to ~1600 C. Metals cannot compete. Fill the shell with insulation and mechanically attach.That sounds like a single use temperature rather than cyclic to me.
John
hi I'm new to the forum, I found this document on the subject space heat material:
https://www.researchgate.net/publication/227221472_Carbon_Fibre_Reinforced_Silicon_Carbide_Composites_CSiC_CC-SiC
Due to the anisotropic coefficient of thermal expansion (CTE) of C/C, C/SiC and C/CSiC, the
oxidation protection of these composites is more difficult than it is for non-reinforced
carbon or graphite bulk materials. The mismatch of CTE between the CVD-SiC coating and
the carbon fibre reinforcement creates cracks in the SiC coating during the cooling-down
period after deposition. Crack formation starts at approximately 100 ◦C below the CVD
coating temperature. Therefore, CVD-SiC coated composites show the highest oxidation
rate at about 800 ◦C, the maximum between crack opening and oxidation kinetics. As a result,
sophisticated oxidation and corrosion coatings can only reduce the material degradation in
a certain temperature interval under static conditions, but all available protection coatings
are not able to prevent oxidation completely under dynamic conditions.
Using the specially equipped laminar water tunnel at the University of Stuttgart in Germany, Professor Bruecker and Professor Rist (University of Stuttgart) have tested the hypothesis of a transition (drag) delay by experimenting with a smooth flat plate and a flat plate covered with biomimetic fish scale arrays.
Their surprising research outcome runs counter to the common belief that roughness promotes by-pass transition. Instead, the scales largely increase the stability of the base flow similar to an array of vortex generators.
A technical realization of such patterns on aerodynamic surfaces will pave the way towards the drastic reduction in fuel consumption and future zero-emission flight.
Possible to use the scale idea on it's own as a passive system, or to try to manipulate the effect with strategic vortex enhancement. Possibly even a two level system where one is almost a back up, or both are required for only one sort of flight profile.
Very interesting research. The work was inspired by flow in water. The testing was done in water. My gut says that optimization of the scales length/width ratio will be heavily dependent on fluid viscosity. As viscosity goes down the optimal length will increase. In a gas environment the optimum scales will resemble ... feathers!
The issue with ceramic heat shield tiles is their fragility, rigidity, and the difficulty in attaching them to a substrate. In particular, if they flex they will break.
Niobium alloys with a thin silica-rich coating (to protect it from oxidation) can bend and are even elastic. But a niobium alloy with its coating weighs more than comparable ceramic heat shield tiles assuming a niobium alloy thickness greater than that of a foil.
Another advantage the niobium has is that micrometeorites that would shatter part of a ceramic heat shield tile will have a negligible impact on the heat shielding capacity of the niobium alloy.
In comparing the two, we also need to include the weight of the systems needed to attach the two materials to the stainless steel skin of the Starship. Since niobium alloys can be welded to niobium alloys I wonder if it might also be possible to spot weld them to stainless steel.
Niobium alloys are light enough that they were seriously considered for the Space Shuttle. Now as I understand it there was no insulation under that double niobium layer that was tested for the Space Shuttle. Two thin layers of niobium sheet by themselves were enough to protect the aluminum structure underneath.
It could be that niobium alloy is the better solution on the parts of the Starship skin where bending and flexing can be anticipated, as for instance the skirt.
In addition I wonder about combining the niobium alloy with methane cooling since the niobium can so easily be given corrugations and other three dimensional structure.
Since the niobium alloy can be readily formed to make channels, the sheet could be used to simultaneously guide the methane gas to where it is needed and to serve as heat shielding at the same time.
The issue with ceramic heat shield tiles is their fragility, rigidity, and the difficulty in attaching them to a substrate. In particular, if they flex they will break.
Niobium alloys with a thin silica-rich coating (to protect it from oxidation) can bend and are even elastic. But a niobium alloy with its coating weighs more than comparable ceramic heat shield tiles assuming a niobium alloy thickness greater than that of a foil.
Another advantage the niobium has is that micrometeorites that would shatter part of a ceramic heat shield tile will have a negligible impact on the heat shielding capacity of the niobium alloy.
In comparing the two, we also need to include the weight of the systems needed to attach the two materials to the stainless steel skin of the Starship. Since niobium alloys can be welded to niobium alloys I wonder if it might also be possible to spot weld them to stainless steel.
Niobium alloys are light enough that they were seriously considered for the Space Shuttle. Now as I understand it there was no insulation under that double niobium layer that was tested for the Space Shuttle. Two thin layers of niobium sheet by themselves were enough to protect the aluminum structure underneath.
It could be that niobium alloy is the better solution on the parts of the Starship skin where bending and flexing can be anticipated, as for instance the skirt.
In addition I wonder about combining the niobium alloy with methane cooling since the niobium can so easily be given corrugations and other three dimensional structure.
Since the niobium alloy can be readily formed to make channels, the sheet could be used to simultaneously guide the methane gas to where it is needed and to serve as heat shielding at the same time.
- C/SiC composites are pretty tough. They are used in turbine engines. Mounting appears to use felt pad to isolate tile from structure.
- I don't believe two layers of metal are going to protect an aluminum structure from reentry heat. Do you have a reference document about the work? Probably used insulation as well.
John
The issue with ceramic heat shield tiles is their fragility, rigidity, and the difficulty in attaching them to a substrate. In particular, if they flex they will break.
Niobium alloys with a thin silica-rich coating (to protect it from oxidation) can bend and are even elastic. But a niobium alloy with its coating weighs more than comparable ceramic heat shield tiles assuming a niobium alloy thickness greater than that of a foil.
Another advantage the niobium has is that micrometeorites that would shatter part of a ceramic heat shield tile will have a negligible impact on the heat shielding capacity of the niobium alloy.
In comparing the two, we also need to include the weight of the systems needed to attach the two materials to the stainless steel skin of the Starship. Since niobium alloys can be welded to niobium alloys I wonder if it might also be possible to spot weld them to stainless steel.
Niobium alloys are light enough that they were seriously considered for the Space Shuttle. Now as I understand it there was no insulation under that double niobium layer that was tested for the Space Shuttle. Two thin layers of niobium sheet by themselves were enough to protect the aluminum structure underneath.
It could be that niobium alloy is the better solution on the parts of the Starship skin where bending and flexing can be anticipated, as for instance the skirt.
In addition I wonder about combining the niobium alloy with methane cooling since the niobium can so easily be given corrugations and other three dimensional structure.
Since the niobium alloy can be readily formed to make channels, the sheet could be used to simultaneously guide the methane gas to where it is needed and to serve as heat shielding at the same time.
- C/SiC composites are pretty tough. They are used in turbine engines. Mounting appears to use felt pad to isolate tile from structure.
- I don't believe two layers of metal are going to protect an aluminum structure from reentry heat. Do you have a reference document about the work? Probably used insulation as well.
John
Rereading the paper again that inspired these thoughts, see https://ntrs.nasa.gov/citations/19730024093, I do wonder if I'm seeing the full context. I find no mention of any insulation, other than than the two layers of niobium alloy, one flat and one corrugated, and coated with a thin fused silicon/chromium/iron coating.
But maybe there actually is such a thing and the authors simply assumed that the people reading it would know that from the context.
The issue with ceramic heat shield tiles is their fragility, rigidity, and the difficulty in attaching them to a substrate. In particular, if they flex they will break.
Niobium alloys with a thin silica-rich coating (to protect it from oxidation) can bend and are even elastic. But a niobium alloy with its coating weighs more than comparable ceramic heat shield tiles assuming a niobium alloy thickness greater than that of a foil.
Another advantage the niobium has is that micrometeorites that would shatter part of a ceramic heat shield tile will have a negligible impact on the heat shielding capacity of the niobium alloy.
In comparing the two, we also need to include the weight of the systems needed to attach the two materials to the stainless steel skin of the Starship. Since niobium alloys can be welded to niobium alloys I wonder if it might also be possible to spot weld them to stainless steel.
Niobium alloys are light enough that they were seriously considered for the Space Shuttle. Now as I understand it there was no insulation under that double niobium layer that was tested for the Space Shuttle. Two thin layers of niobium sheet by themselves were enough to protect the aluminum structure underneath.
It could be that niobium alloy is the better solution on the parts of the Starship skin where bending and flexing can be anticipated, as for instance the skirt.
In addition I wonder about combining the niobium alloy with methane cooling since the niobium can so easily be given corrugations and other three dimensional structure.
Since the niobium alloy can be readily formed to make channels, the sheet could be used to simultaneously guide the methane gas to where it is needed and to serve as heat shielding at the same time.
- C/SiC composites are pretty tough. They are used in turbine engines. Mounting appears to use felt pad to isolate tile from structure.
- I don't believe two layers of metal are going to protect an aluminum structure from reentry heat. Do you have a reference document about the work? Probably used insulation as well.
John
Rereading the paper again that inspired these thoughts, see https://ntrs.nasa.gov/citations/19730024093, I do wonder if I'm seeing the full context. I find no mention of any insulation, other than than the two layers of niobium alloy, one flat and one corrugated, and coated with a thin fused silicon/chromium/iron coating.
But maybe there actually is such a thing and the authors simply assumed that the people reading it would know that from the context.
(The VentureStar metallic TPS dimensions came from "Reusable metallic thermal protection systems development"
by Max L. Blosser, Carl J. Martin, Kamran Daryabeigi, and Carl C. Poteet)
Here are the dimensions for the metallic thermal protection system proposed for theThe study you cited for the niobium heat shield is as John mentioned just for a single wind facing surface layer, not a complete heat shield. Other studies (like this one https://ntrs.nasa.gov/citations/19770015587) looked at the whole system.
VentureStar.
0.4 mm titanium outer facesheet
6.4 mm deep Inconel 617 and titanium honeycomb sandwich
0.4 mm titanium inner facesheet
50.6 mm Saffil insulation
0.4 mm titanium foil
9.5 mm air gap
And it's all mounted with four screws per panel on an aluminum substructure.
That's a total depth of 2.67 inches, including the air gap, or 2.29 inches excluding the air
gap.
In contrast the simple two layer niobium alloy foil sandwich proposed for the space shuttle
had a total depth of about 14.7 mm (0.58") which includes about 14 mm of enclosed air.
I had been picturing the niobium alloy as a metal sheet, but assuming I have the dimensions
correct now, it is really just a foil, some 0.3 mm thick plus the 3 mil depth (6 mil total) of
the fused silicon/chromium/iron coating.
This niobium alloy foil can be welded to itself, but the idea of spot welding this to
stainless steel probably doesn't make sense.
Unlike with the VentureStar paper, there is no discussion in the Space Shuttle paper of how
the niobium foil would be mounted on the aluminum substrate.
It is striking that the thickness of the niobium alloy foil is about the same thickness
as the titanium foil and that the depth of the Inconel 617 and titanium sandwich is a little less
than half the depth of the two layers of niobium alloy that were to be welded together for the
space shuttle.
We only need to add a 40 mm layer of insulation to the two layers of niobium alloy and the
two systems would have had the same overall dimensions (about 2.67" deep).
I feel like it was an oversight to not include the mounting system in the many tests of durability
of the niobium foil panels that were done for the space shuttle study as surely those mount points
would have had an impact on the durability.
Now the fact that the substructure is stainless steel on the Starship and not aluminum will surely
decrease the thickness of the needed insulation. Or maybe it can be completely replaced with
an air gap, and this would surely be the case if it's being supplemented by methane cooling.
(The VentureStar metallic TPS dimensions came from "Reusable metallic thermal protection systems development"
by Max L. Blosser, Carl J. Martin, Kamran Daryabeigi, and Carl C. Poteet)
(Edited: Some corrections after re-reading.)
Interesting new twist on the tile attachment studs. The bottom center stud is definitely different. Some cute new fastening scheme?
John
Interesting new twist on the tile attachment studs. The bottom center stud is definitely different. Some cute new fastening scheme?
John
One pin seems to be missing, but there's a mark there. I wonder if they stress test them after welding.
Those caps are bigger and more uneven than in tent build Model 3. And one tile is already broken... You're instilling me with a lot of confidence, Doc.Could be. And at least one of those tiles is either seriously discolored, cracked or has a very uneven surface.
Ok, it's not actual heat shield. It's a structural and bonding test of the tiles.
The issue with ceramic heat shield tiles is their fragility, rigidity, and the difficulty in attaching them to a substrate. In particular, if they flex they will break.
Niobium alloys with a thin silica-rich coating (to protect it from oxidation) can bend and are even elastic. But a niobium alloy with its coating weighs more than comparable ceramic heat shield tiles assuming a niobium alloy thickness greater than that of a foil.
Another advantage the niobium has is that micrometeorites that would shatter part of a ceramic heat shield tile will have a negligible impact on the heat shielding capacity of the niobium alloy.
In comparing the two, we also need to include the weight of the systems needed to attach the two materials to the stainless steel skin of the Starship. Since niobium alloys can be welded to niobium alloys I wonder if it might also be possible to spot weld them to stainless steel.
Niobium alloys are light enough that they were seriously considered for the Space Shuttle. Now as I understand it there was no insulation under that double niobium layer that was tested for the Space Shuttle. Two thin layers of niobium sheet by themselves were enough to protect the aluminum structure underneath.
It could be that niobium alloy is the better solution on the parts of the Starship skin where bending and flexing can be anticipated, as for instance the skirt.
In addition I wonder about combining the niobium alloy with methane cooling since the niobium can so easily be given corrugations and other three dimensional structure.
Since the niobium alloy can be readily formed to make channels, the sheet could be used to simultaneously guide the methane gas to where it is needed and to serve as heat shielding at the same time.
- C/SiC composites are pretty tough. They are used in turbine engines. Mounting appears to use felt pad to isolate tile from structure.
- I don't believe two layers of metal are going to protect an aluminum structure from reentry heat. Do you have a reference document about the work? Probably used insulation as well.
John
The issue with ceramic heat shield tiles is their fragility, rigidity, and the difficulty in attaching them to a substrate. In particular, if they flex they will break.
Niobium alloys with a thin silica-rich coating (to protect it from oxidation) can bend and are even elastic. But a niobium alloy with its coating weighs more than comparable ceramic heat shield tiles assuming a niobium alloy thickness greater than that of a foil.
Another advantage the niobium has is that micrometeorites that would shatter part of a ceramic heat shield tile will have a negligible impact on the heat shielding capacity of the niobium alloy.
In comparing the two, we also need to include the weight of the systems needed to attach the two materials to the stainless steel skin of the Starship. Since niobium alloys can be welded to niobium alloys I wonder if it might also be possible to spot weld them to stainless steel.
Niobium alloys are light enough that they were seriously considered for the Space Shuttle. Now as I understand it there was no insulation under that double niobium layer that was tested for the Space Shuttle. Two thin layers of niobium sheet by themselves were enough to protect the aluminum structure underneath.
It could be that niobium alloy is the better solution on the parts of the Starship skin where bending and flexing can be anticipated, as for instance the skirt.
In addition I wonder about combining the niobium alloy with methane cooling since the niobium can so easily be given corrugations and other three dimensional structure.
Since the niobium alloy can be readily formed to make channels, the sheet could be used to simultaneously guide the methane gas to where it is needed and to serve as heat shielding at the same time.
- C/SiC composites are pretty tough. They are used in turbine engines. Mounting appears to use felt pad to isolate tile from structure.
- I don't believe two layers of metal are going to protect an aluminum structure from reentry heat. Do you have a reference document about the work? Probably used insulation as well.
John
The SIC/SIC components in gas turbines are actually quite chunky. One of the big issues is dealing with the difficulty of forming them into useful shapes and how to attach them to metallic components.
Most components in a gas turbine are also held in position very loosely by entrapment with other components that are assembled in afterwards until you get to a casing flange
The SIC/SIC components in gas turbines are actually quite chunky. One of the big issues is dealing with the difficulty of forming them into useful shapes and how to attach them to metallic components.Which suggest the big issue is not their fragility after firing but making sure they are fired all the way through properly to begin with. It also makes them sound heavy. Shuttle tiles won because they are actually about 95% pore and 5% tile, but were very fragile.
Very thin C/SiC can be laid up, a few thousandths of of an inch.True, but that does not appear to be the case here, and very labor intensive. I think they are using some kind of casting approach.
John
The SIC/SIC components in gas turbines are actually quite chunky. One of the big issues is dealing with the difficulty of forming them into useful shapes and how to attach them to metallic components.Which suggest the big issue is not their fragility after firing but making sure they are fired all the way through properly to begin with. It also makes them sound heavy. Shuttle tiles won because they are actually about 95% pore and 5% tile, but were very fragile.Very thin C/SiC can be laid up, a few thousandths of of an inch.True, but that does not appear to be the case here, and very labor intensive. I think they are using some kind of casting approach.
John
I'm finding it difficult to judge size of these tiles. They have substantial thickness so I'd say at least 1cm but maybe closer to an inch? Shuttle standard (after the cracking issues) was about 6" wide, which IIRC gave them a tile job of about 24 000 tiles (which would be some bathroom :) )
- Space X tiles are ~.31 m across and ~4 cm thick,Like my old college landladies home-made pizza :)
- They have been examining many alternatives.Yes the design space (even for just ceramic based systems) is huge.
- We have seen that the outer shell appears to be a thin coated material over insulation. Some of those shells appeared to be rather brittle, suggesting thin ceramic. Others appear to be more substantial, suggesting something with some strength.Pretty much the TUFROC patent. Not so much a patent for a set of materials to make a TPS but an architecture for a TPS, although (unlike the patent) I'm not sure the top surface skin goes down the sides in order to protect from plasma ingress (which otherwise needed all those fiddly little gap filling bits).
- They have experimented with both mechanical and bonded attachment. Mechanical attachment seems to have worked out better. Mechanical attachment experimentation is apparent and appears to still be evolving.When you consider every scenario (and what you've got to do to support that scenario, like a repair paste that you can use in deep space or on the surface of mars etc) mechanical fastening (especially given that TCE for steel is 1/3 that of aluminum) seems the better way to go.
- Mechanical attachment of outer shell through weaker insulation to studs has been seen.Pretty much the TUFROC patent
- insulation maybe solid or batt, mounted on what appears to be a felt pad to spread localized stresses and for protection between tile.That's the attraction of this architecture. You can keep the insulation inside the "top hat" and it can be pretty fragile. That means low density --> lower conductivity.
- This leads me to speculate on some form of coated Carbon/SiC composite shell filled with insulation, backed with felt, mechanically attached. Automating the layup of a thin C/SiC shell should be possible.Do you mean backed with felt to retain the insulation inside a rigid 5 sized box or as a mounting material of the tile to the skin? On Shuttle the felt isolation pads (I picture it as being like a thin layer of wadded up nylon stocking material) was necessary to cope with the high CTE of the aluminum skin and because of expected mass of a fastener based solution.
John
....
Do you mean backed with felt to retain the insulation inside a rigid 6 sized box or as a mounting material of the tile to the skin? On Shuttle the felt isolation pads (I picture it as being like a thin layer of wadded up nylon stocking material) was necessary to cope with the high CTE of the aluminum skin and because of expected mass of a fastener based solution.
This just leaves tile vibration induced by air loads as a reason to include some kind of felt pad.
When you consider the scale SS is expected to operate on any solution will have to allow automation. Robots cope better with rigid materials and fixed locations to move a part to so I think they will try to avoid felt or batting. Ideally you'd like any material failure to be very obvious, like a color change or a highly visible crack once it's above it's safe stress level. Worst case something you can see through the helmet of a space suit. :(
A trickier question is whether the shell should just be the top surface or have sides as well. The latter gives you a box you can put very fragile (loft or foamed zirconia type) insulation into.
On the downside mass production of a fiber reinforced ceramic hexagon box shape is likely to be quite tricky. This is also now a fixed component. You don't have a material you can cut to shape otherwise you lose the benefits of the side walls (insulation containment and protection from water ingress on the ground and plasma getting between the tiles during entry).
That's not important if the same design can cope with all parts of the vehicle but that's unlikely to be the case for leading edges of the control surfaces. How many spares to carry to mars (and will they survive 26 months of martian weather)?
- Felt is composed of teased or needled together fibers. I believe fibers used for shuttle were Nomex. Felt is made in a wide range of thicknesses. I would expect a thickness in the range of 5 - 10 mm. I believe its use would be for vibration damping and fitting against a structure which changes shape due to oil canning etc. The same felt could be molded to protect the space between the tile. The felt part is flexible, and precisely trimmable. Don't see why placement and attachment to the tile could not be automated. The tile could be manufactured with the felt already attached, ready for attachment to the Starship.Felting looks to be a quite a useful way to make materials that are very difficult to weave into larger structures. They can be used for vibration damping but I think the issue with shuttle TPS was because the tiles were bonded, creating an extended joint area between the tiles and the skin. Once you go to a point mounting (and a skin that expands and contracts 1/3 that of aluminum for the same change in temperature) things get much easier.
- The tile shell is going to need side walls and sealed in some sense against water vapor. I don't see this as "tricky". Its basically a flat layup of a few layers, then blocked in a form ready for firing.
- The felt would not be used for attaching tile. Tile are mechanically attached.
- Felt could be used to retain batting inside the tile shell, but I suspect they might want something less permeable to water, though maybe hydrophobic felt.
- Certainly a significant design and development problem, but I don't see road blocks WRT to automation. Automating layup of the tile shell, coating tile shell, filling with insulation, sealing tiles against water vapor, or attaching felt to tile. These types of operations are automated now.
- Uniquely shaped replacement parts will need to be fabricated onboard for repairs, but these would be one use items.
John
Felting looks to be a quite a useful way to make materials that are very difficult to weave into larger structures. They can be used for vibration damping but I think the issue with shuttle TPS was because the tiles were bonded, creating an extended joint area between the tiles and the skin. Once you go to a point mounting (and a skin that expands and contracts 1/3 that of aluminum for the same change in temperature) things get much easier.
I can see your point but I think moving from an area to a point attachment (and the move to SS) makes a lot of those issues much smaller. OTOH I could see vibration of the tiles hitting the skin could be an issue. In that case having a cushion material seems like a pretty good idea.
Felting looks to be a quite a useful way to make materials that are very difficult to weave into larger structures. They can be used for vibration damping but I think the issue with shuttle TPS was because the tiles were bonded, creating an extended joint area between the tiles and the skin. Once you go to a point mounting (and a skin that expands and contracts 1/3 that of aluminum for the same change in temperature) things get much easier.
C/SiC has good strength but it is brittle. If it was just thermal expansion, I would agree with you, but in certain areas the Starship structure going to move and distort. I think SpaceX will want a compliance layer between them.
John
Space Exploration Technologies Corp. (SpaceX) of Hawthorne, Californiahttps://www.nasa.gov/directorates/spacetech/2020_NASA_Announcement_of_Collaboration_Opportunity_ACO_Selections
SpaceX will partner with Langley to capture imagery and thermal measurements of its Starship vehicle during orbital re-entry over the Pacific Ocean. With the data, the company plans to advance a reusable thermal protection system, which protects the vehicle from aerodynamic heating, for missions returning from low-Earth orbit, the Moon, and Mars.
Why would you want to shield them from debris? Debris impact was one of *the* problems for the shuttle heat shield and if you have expected debris, you’d better be able to handle them!
Why would you want to shield them from debris? Debris impact was one of *the* problems for the shuttle heat shield and if you have expected debris, you’d better be able to handle them!
Alright, so nobody's posted on the new TPS photos, so I'll have a go.
Mary's most recent shot, post static fire:
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=51332.0;attach=1988280;image
To me, it looks like we learn two things from this:
1. Haven't solved the issue with vibration damage to the tiles.
2. There's some additional Y-shaped structure that I don't think we've seen before. I don't know enough about this stuff to say anything smart about it.
The pessimist in me is thinking it's bad they can't figure out how to attach these things without them breaking/falling off. The optimist in me is thinking that the other ones aren't broken, and that's better than some previous static fires where they've all fallen off. Perhaps they are again testing different types of tiles/fasteners, and here we see 8/9 remaining attached? If the pessimist is right, an 8/9 pass rate is far too low (obviously). If the optimist is right, it's plausible they've solved the issue, or at least have come close to doing so.
What do you all think?
Edit: on a second note, maybe 8/9 is too generous. Looks like there might be chips/damage to some other tiles, not sure the degree to which this could/would be incapacitating.
Alright, so nobody's posted on the new TPS photos, so I'll have a go.
Mary's most recent shot, post static fire:
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=51332.0;attach=1988280;image
To me, it looks like we learn two things from this:
1. Haven't solved the issue with vibration damage to the tiles.
2. There's some additional Y-shaped structure that I don't think we've seen before. I don't know enough about this stuff to say anything smart about it.
The pessimist in me is thinking it's bad they can't figure out how to attach these things without them breaking/falling off. The optimist in me is thinking that the other ones aren't broken, and that's better than some previous static fires where they've all fallen off. Perhaps they are again testing different types of tiles/fasteners, and here we see 8/9 remaining attached? If the pessimist is right, an 8/9 pass rate is far too low (obviously). If the optimist is right, it's plausible they've solved the issue, or at least have come close to doing so.
What do you all think?
Edit: on a second note, maybe 8/9 is too generous. Looks like there might be chips/damage to some other tiles, not sure the degree to which this could/would be incapacitating.
This thing is supposed to be able to land on unimproved surfaces on Mars with its heatshield. I would bet its not debris. It probably isnt thermal expansion of the tank during cycling. The brackets look like they should prevent the tiles from being damaged by that. Its probably vibration issues during engine firing. They will have to figure out how to design a bracket that can hold the tiles, dampen the vibrations, be highly heat resistant, lightweight, and securely hold the tiles so they do not easily fall off or break.Exactly (and that's not a full list) . :(
Could be we've never seen it before. Could be because this is the first time it's been there to see.
To me, it looks like we learn two things from this:
1. Haven't solved the issue with vibration damage to the tiles.
2. There's some additional Y-shaped structure that I don't think we've seen before. I don't know enough about this stuff to say anything smart about it.
Could be the tile breakage problem is all related to ground affected acoustics and once the SS is securely mounted on top of a Superheavy 50 m off the pad this will all be no problem.I think that tiles mounted on the skirt during the landing (especially with the current short legs) represent by far the worst case with regard to the mechanical stresses on the mounting system, perhaps followed by three engine static fire. The fact that many of the tiles survived on SN5 makes me think they might have been ok for flight (with the thermal environment during reentry adding a different dimension). It seems like it is the strength of the tile material that is the current weak point and that the pin mounting method isolates them to some degree as the ones that appeared glued in place all sheared of completely.
I think that tiles mounted on the skirt during the landing (especially with the current short legs) represent by far the worst case with regard to the mechanical stresses on the mounting system, perhaps followed by three engine static fire.And hence the ideal location to test design quickly. Most early designs may fail, but the 2nd and 3rd generation designs should be good for the whole vehicle without further failure.
It is probably easy to make the tiles stronger by making them denser but the strength has to increase disproportionately since the forces scale as the mass and denser tiles need to be even thicker to provide the same insulation (further increasing the weight of the whole TPS). There is likely a lot of iteration with regard to material composition as well as micro and macro scale structure in tandem with the more obvious ones with different mounting methods.Avoiding that mass increase (or minimizing it if that's not possible) is what makes this tricky. :(
Could be the tile breakage problem is all related to ground affected acoustics and once the SS is securely mounted on top of a Superheavy 50 m off the pad this will all be no problem.
Per Mary's newest pics of SN9 being lifted outside of the High Bay, it looks like it has quite a few heatshield tiles on it, and possibly thousands of the 3-pronged mounts on the methane tank section!
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52205.0;attach=1989053;image
SpaceX does absolutely not want an over-engineered solution for the TPS. A main point of going for stainless was to enable a lighter TPS. Consequently it makes sense for them to "work their way up", i.e. see which easy, minimal solutions stick (literally) and which don't. They are going through those solutions at the moment and will "work their way up" to the minimal solution which is both reliable, cheap and easy to maintain. Conclusion: we are going to see a lot of tiles failing in different failure modes and, presumably, by the time they will be needed SpaceX will have a great solution.
Some close-up shots.Certainly looks like they have a system they want to test on a larger scale. 73 tiles on the LOX tank with 10 truncated to form a straight line (but no beveling or other transition). Tile attachment pins on the forward and common dome sections with the later seeming to have better weld settings. It seems like compensating for the overlap when stacking the sections is still on the To-Do list.
Some close-up shots.Certainly looks like they have a system they want to test on a larger scale. 73 tiles on the LOX tank with 10 truncated to form a straight line (but no beveling or other transition). Tile attachment pins on the forward and common dome sections with the later seeming to have better weld settings. It seems like compensating for the overlap when stacking the sections is still on the To-Do list.
Some close-up shots.Certainly looks like they have a system they want to test on a larger scale. 73 tiles on the LOX tank with 10 truncated to form a straight line (but no beveling or other transition). Tile attachment pins on the forward and common dome sections with the later seeming to have better weld settings. It seems like compensating for the overlap when stacking the sections is still on the To-Do list.
Bolding mine for emphasis.
Almost sounds like a system for the join line in the heat shield of a detachable nose section! ;D
Better, but still; if those were floor tiles I'll would fire the contractor and send tiles back to manufacturer...
Better, but still; if those were floor tiles I'll would fire the contractor and send tiles back to manufacturer...I believe "large" tile gaps are for thermal dilatation.
Even in terms of regular old not-smacking-into-the-Straosphere aerodynamic effects that amount of surface unevenness is not great.It will not be a problem with regard to aerodynamics - have you seen the rivets, bolts, corrugations and external fittings and pipes on other launch vehicles?
Even in terms of regular old not-smacking-into-the-Straosphere aerodynamic effects that amount of surface unevenness is not great.It will not be a problem with regard to aerodynamics - have you seen the rivets, bolts, corrugations and external fittings and pipes on other launch vehicles?
The question is how it will affect the boundary layer transition and the resulting increase in heating during reentry. Only SpaceX knows what their models say - they might be right at the limit where even the 2.5 mm difference between flat and curved tiles matter. Or they could have plenty of margin even with the equivalent of missing tiles. And nobody will take the model output as more than a rough guide line untill they are validated with plenty of real data.
Hey, welcome to the forum. You jump in with both feet.Some close-up shots.Certainly looks like they have a system they want to test on a larger scale. 73 tiles on the LOX tank with 10 truncated to form a straight line (but no beveling or other transition). Tile attachment pins on the forward and common dome sections with the later seeming to have better weld settings. It seems like compensating for the overlap when stacking the sections is still on the To-Do list.
Bolding mine for emphasis.
Almost sounds like a system for the join line in the heat shield of a detachable nose section! ;D
I still don't believe that. There are plenty of other reasons to have truncated tiles (flaps, body-flap interfaces, bottom of the ship). It seems absurd to me that such a fundamental element of design has never once been mentioned unambiguously in the updates or by Elon on Twitter or shown in renders. It also seems unreasonably complex, heavy and risky for little benefit
Better, but still; if those were floor tiles I'll would fire the contractor and send tiles back to manufacturer...
It will not be a problem with regard to aerodynamics - have you seen the rivets, bolts, corrugations and external fittings and pipes on other launch vehicles?Going up, no. It's the coming back down again that this is likely to cause trouble for.
The question is how it will affect the boundary layer transition and the resulting increase in heating during reentry. Only SpaceX knows what their models say - they might be right at the limit where even the 2.5 mm difference between flat and curved tiles matter. Or they could have plenty of margin even with the equivalent of missing tiles. And nobody will take the model output as more than a rough guide line untill they are validated with plenty of real data.True.
Boundary layer will transition very quickly. I would assume nearly complete turbulent flow once you get into significant atmosphere.Given that turbulent boundary layers transfer heat to the skin 4x or more faster than laminar I think they'd like to try to keep it laminar as AFAP. And then there are possible shock/shock interactions between the canards and the body and canards and other aerosurfaces.
John
One thing I hadn't noticed before. There are 2 different kinds of tile mount. The fairly substantial "posts" at about the middle of the tile width (but too many of them to be just at the actual center) and the edge ones which look sort of like tuning forks.
I guess you want to "provoke" a response? There are a couple of principles involved. One of them is, if you must fail, it's better to fail early. Doesn't mean you want to fail but in an enterprise like this, some failures are inevitable. Another principle is to start with what you think is the minimal successful design. There will be many factors to minimize such as weight, cost, ease of manufacture, durability etc. You may not be minimizing all of them at once but rather systematically working through the possibilities. And if there is a failure you may have to move to a less than optimal design. You do as few trade-offs as possible to get something that works.
If you believe it is better to "fail early" then you shouldn't just hope for failures, you should provoke them.
Was it discussed why the edges of the tiles look thick but only thin black layer inside its middle?They seem to follow the same concept as the Space Shuttle tiles: The body of the tile is a low density porous white ceramic with a tougher black glaze-like layer on the sides and top surface. We have not seen any sign that they black surface layer extends to the bottom and most of the failures seem to stem from the white bulk material not being strong enough to stay attached to the supports.
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=51332.0;attach=1988280;image
Why are people expecting the heat shield to looks smooth as bathroom tile? If you look at photos of the heat shield on the space shuttle they also have considerable variation:The Shuttle tiles were (nominally) smoother than most bathroom floors - the top surfaces were just as flat and level and the gaps were relatively narrow (although generally not "grouted"). That not to say that it had to be perfect, they often had minor (or not so minor) surface damage and gap fillers stickling out a few mm. Some of the last flights even tested the effect of a deliberate protrusion up to 0.5 inch.
If you believe it is better to "fail early" then you shouldn't just hope for failures, you should provoke them.That's FINE, but you would no doubt want to have the system heavily instrumented in the areas where you want to "provoke" failures, and probably have the areas for provocation stacked towards the end of a test flight, so you can collect as much useful data as possible with each mission.
Unfortunately that didn't take much to cause damage to the tiles.....The earliest photos of the this tile arrangement on SN9 show that tile to have some damage. At this time, I don’t think we can postulate that the movement around the worksite caused this damage.
Just moving the tank portion of SN9 around a bit and placing it on a couple of different surfaces caused one of the tiles to crack and lose a bit of the black coating.
Image below clipped from BocaChicGal's most recent uploads.
Tuning forks on the outside make sense to deal with thermal expansion.In this context possibly more like toasting forks. :)
Yes it's clearer that the are all the same.One thing I hadn't noticed before. There are 2 different kinds of tile mount. The fairly substantial "posts" at about the middle of the tile width (but too many of them to be just at the actual center) and the edge ones which look sort of like tuning forks.
I don't think so. There are three posts per tile, each of which is a pair of triangular spikes, each 120° from the other.
I guess you want to "provoke" a response? There are a couple of principles involved. One of them is, if you must fail, it's better to fail early. Doesn't mean you want to fail but in an enterprise like this, some failures are inevitable. Another principle is to start with what you think is the minimal successful design. There will be many factors to minimize such as weight, cost, ease of manufacture, durability etc. You may not be minimizing all of them at once but rather systematically working through the possibilities. And if there is a failure you may have to move to a less than optimal design. You do as few trade-offs as possible to get something that works.Ideally yes, but given the potential number of parameters and the number variants that could be a very big list. Time to run a design-of-experiements matrix to identify the minimum number of samples you need to collect maximum data
That's FINE, but you would no doubt want to have the system heavily instrumented in the areas where you want to "provoke" failures, and probably have the areas for provocation stacked towards the end of a test flight, so you can collect as much useful data as possible with each mission.In an ideal world yes, and that patch might well be heavily instrumented.
Then, if possible, stack the possible/intended failures in "increasing likelihood of catastrophic failure" to test your various system hypotheses up to the departure of controlled flight (or telemetry downlink).If possible, yes. If not you have a choice. a) Test it some other way. b) Ensure this situation never happens. Ever.
Why are people expecting the heat shield to looks smooth as bathroom tile? If you look at photos of the heat shield on the space shuttle they also have considerable variation:Maybe you should show image before the first flight to be fair. I think Endeavour's tiles would put any floor tile installer in shame. (Don' look forward RCS it's seems to be mock up but rest of the tiles...)
Even post-flight, the tiles may be discoloured but the surface roughness is extremely low.Why are people expecting the heat shield to looks smooth as bathroom tile? If you look at photos of the heat shield on the space shuttle they also have considerable variation:Maybe you should show image before the first flight to be fair. I think Endeavour's tiles would put any floor tile installer in shame. (Don' look forward RCS it's seems to be mock up but rest of the tiles...)
And another reminder. On this design wrapping the body (constant single axis of curvature) is the easier bit of this design. The leading edges and root-to-body transition areas are going to be much trickier. They would probably scale down the individual tiles to wrap them better. Might be enough to do the job.Not disagreeing with you on this, but recently Elon has mentioned that evaporative cooling is still a possibility in some locations. He said that ITAR prevented discussion of the details.
Unfortunately that didn't take much to cause damage to the tiles.....
Just moving the tank portion of SN9 around a bit and placing it on a couple of different surfaces caused one of the tiles to crack and lose a bit of the black coating.
Image below clipped from BocaChicGal's most recent uploads.
Not disagreeing with you on this, but recently Elon has mentioned that evaporative cooling is still a possibility in some locations. He said that ITAR prevented discussion of the details.Reaction Engines have known for years that their canards will need active cooling due to shock interference between them and either the wings or the main body. IRC they estimated it will take about 400Kg of LH2. In terms of re entry SS is not that different.
Not disagreeing with you on this, but recently Elon has mentioned that evaporative cooling is still a possibility in some locations. He said that ITAR prevented discussion of the details.Reaction Engines have known for years that their canards will need active cooling due to shock interference between them and either the wings or the main body. IRC they estimated it will take about 400Kg of LH2. In terms of re entry SS is not that different.
Obviously SS won't have that and of course I'm quite sure the design team are working furiously to avoid any liquid cooling. Might be possible. Might not.
The appearance of the first SS after the first flight to 50 Kft will make very interesting viewing.
I don't find crumpled tinfoil that interesting myself.... ;)As John Carmack and Armadillo Aerospace showed the exact way they crumple can be very instructive about what loads they were under and what they can survive.
SpaceX Toughened Unipiece Fibrous Insulation (TUFI) Slurry
MANUFACTURER: Space Exploration Technologies
8550 Astronaut Blvd.
Cape Canaveral, FL 32920
INTENDED USE: Thermal Protection Insulation
SpaceX Reaction Cured Glass (RCG)
MANUFACTURER: Space Exploration Technologies
8550 Astronaut Blvd.
Cape Canaveral, FL 32920
INTENDED USE: Thermal Protection Tile Coating
Seems like additional/alternative methods will be tested, involving sprayed/coated heat shield material. The attached document is an environmental permit (registration) for a coating process at SpaceX Boca Chica site. Among a ton of administrative details two materials to be used described:QuoteSpaceX Toughened Unipiece Fibrous Insulation (TUFI) Slurry
MANUFACTURER: Space Exploration Technologies
8550 Astronaut Blvd.
Cape Canaveral, FL 32920
INTENDED USE: Thermal Protection InsulationQuoteSpaceX Reaction Cured Glass (RCG)
MANUFACTURER: Space Exploration Technologies
8550 Astronaut Blvd.
Cape Canaveral, FL 32920
INTENDED USE: Thermal Protection Tile Coating
8550 Astronaut at Canaveral is their "Starship Tile Facility".
SpaceX is proposing unenclosed surface coating operations at the site (EPN SURF-1). Carbon steel
(i.e., A36, A500, A572, etc.) materials will be coated within a painting tent with the option to vent
directly to the atmosphere or through a three-walled water wash filter. Coatings will be applied
using high-volume low-pressure (HVLP) spray guns (assuming a transfer efficiency of 65%) and
will be allowed to air dry once applied. Emissions calculations have conservatively been
estimated assuming no control from the water wash filter.
Emissions will include volatile organic compounds (VOCs), particulate matter (PM), and
hazardous air pollutants (HAPs).
The facility employs approximately 20 people and has been operating at this location since 2019. Operating
hours are 24 hours a day, seven days a week working three shifts. Brevard County provides potable water and
sanitary sewer services. The property is owned by Cape Canaveral Joint Venture, 516 Delannoy Ave., Cocoa, Florida 32922.
INSPECTION HISTORY
The facility has never been inspected by the Department for compliance with state and federal hazardous waste
regulations.
Process Description:
An opening conference was held to discuss the purpose of the inspection, and processes performed and wastes
generated at the facility.
The facility operates in a 40,000 square-foot unit of the building to manufacture heat-shield tiles for Space
Exploration Technologies Corp's Starship vehicle. Current facility operations are performing process
improvements of the tiles. Production of the final tiles is slated for end of year 2020.
Processes at the facility include:
- Slurry Mix-casting billets, one billet will make two tiles;
- Cast-sintering billets;
- Machining-create tiles from billet and shape tiles into desired form;
- Coatings-apply two coatings to tiles;
- Kiln-dry tiles;
- Water proofing-drive out water from tiles and apply a coating; and
- Hardware-final assembly of tile.
INSPECTION NARRATIVE
The inspection began in Casting. Purified silicon is added to a tank where a slurry is made. When the slurry is
at the proper consistency it is distributed to the casting molds to create the billet. A vacuum is applied to the
case to remove excess water. The water is reused to make slurry.
A kiln is used to dry the billet. After drying, the billet is split in two pieces thereby creating the rudimentary tiles.
The tiles are shaped to the desired form using a router. A shop vacuum is used to clean up silicone from the
router. In this area were satellite accumulation areas: one for a 30-gallon drum of hazardous waste isopropyl
alcohol (IPA) solids, one for a 55-gallon drum of hazardous waste aerosol cans, and one for a 55-gallon drum of
hazardous waste two-part epoxy. The drums were properly labeled "Hazardous Waste" and were closed. None
of the containers were marked with the hazards of the contents [40 CFR 262.15(a)(5)(ii)]. Also in the area was a
55-gallon drum of non-hazardous waste petroleum contact solids.
Emergency equipment noted in the area included a spill kit and eye wash station.
A coating is manufactured and applied to the tiles. An automated machine applies the coating. The final coating
that will be applied to the tiles is still undergoing development. In this area were satellite accumulation areas:
one for a 55-gallon drum of hazardous waste paint liquids and another for a 55-gallon drum of hazardous waste
paint solids. The drums were properly labeled "Hazardous Waste", marked with the hazards of the contents,
and were closed. The wastes are generated from maintenance of the coating equipment. Also in the area was
a 55-gallon drum of non-hazardous waste petroleum contact solids and a 30-gallon drum of non-hazardous
waste frit and water. The petroleum contact solids are an oily debris waste generated from equipment
maintenance. The frit and water are generated from drying slurry.
In the water proofing process, a mixture of methyl-trimethoxy silane (MTMS) and acetic acid is applied to seal
the tiles.
More evidence that SpaceX is planning on mechanically attached, shuttle and X-37 derived tile. They appear to be co-curing mechanical attachment fittings into the AETB blocks.
Attached a good summary of variations of tile and leading edge systems derived from shuttle and currently used on X-37.
John
TRL=Technology Readiness LevelAlternatively (from https://www.granttremblay.com/blog/trls)..
The higher the number, the more mature a technology is.
https://en.wikipedia.org/wiki/Technology_readiness_level
At this point is it safe to say that the heat shield is the most difficult technical problem remaining on Starship?I'd say so. My biggest concern was engines restarting after all the acrobatics, but that seems to have gone pretty well.
The aerodynamics have been shown to work and the flight envelope can be expanded, but dealing with actual re-entry heating is still unproven.
At this point is it safe to say that the heat shield is the most difficult technical problem remaining on Starship?I'd say so. My biggest concern was engines restarting after all the acrobatics, but that seems to have gone pretty well.
The aerodynamics have been shown to work and the flight envelope can be expanded, but dealing with actual re-entry heating is still unproven.
Other that the heat shield, just about everything else seems to be details.
Someone had suggested that the flaps/elonerons might not need tiles if they were folded when reentering the atmosphere. This photo taken during the flip gives a clear view of airflow crossing the supporting structures and the flaps at low speed.
Someone had suggested that the flaps/elonerons might not need tiles if they were folded when reentering the atmosphere. This photo taken during the flip gives a clear view of airflow crossing the supporting structures and the flaps at low speed.
Someone had suggested that the flaps/elonerons might not need tiles if they were folded when reentering the atmosphere. This photo taken during the flip gives a clear view of airflow crossing the supporting structures and the flaps at low speed.
That is missing the point, though.... they will not be folded all the way during re-entry. Depending on the payload and mass distribution during re-entry, and the phases of flight, the fins could be folded back all the way or extended all the way.
At this point is it safe to say that the heat shield is the most difficult technical problem remaining on Starship?I'd say so. My biggest concern was engines restarting after all the acrobatics, but that seems to have gone pretty well.
The aerodynamics have been shown to work and the flight envelope can be expanded, but dealing with actual re-entry heating is still unproven.
Other that the heat shield, just about everything else seems to be details.
Replying to @PPathole @ErcXspace @SpaceX
I still have a soft spot in my heart for transpiration cooking. In theory, it would use more mass than a tile heatshield, but that remains to be seen.
Replying to @PPathole @ErcXspace @SpaceX
*cooling haha
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Elon Musk Elon Musk
@elonmusk
7h
The shuttle had a moving tail flap. So there is already an existence proof of at least one way to solve moving reentry parts
If that's the case, sealing the flap-hinge gap is probably the hardest remaining problem for StarshipJust a layman's idea: if there was a pressurised layer behind the tiles then instead of plasma pushing in you could get cold gas pushing out and thus get concentrated transpiration cooling on just that crack.. which presumably would only use a very small budget of gas if an entire-hull transpiration based system is even halfway plausible.
Would be very interesting to get a general sense of how tolerant of limited tile failures, tile gaps, imperfect reentry AoA, etc Starship will be with a ~100% steel hull.
The shuttle had a moving tail flap. So there is already an existence proof of at least one way to solve moving reentry parts
Wasn’t the tail of the shuttle almost completely occluded from the airstream due tue the entry angle? Whereas Starship will require the heat shield to be directly exposed to the airstream for the entire entry duration.
If that's the case, sealing the flap-hinge gap is probably the hardest remaining problem for StarshipJust a layman's idea: if there was a pressurised layer behind the tiles then instead of plasma pushing in you could get cold gas pushing out and thus get concentrated transpiration cooling on just that crack.. which presumably would only use a very small budget of gas if an entire-hull transpiration based system is even halfway plausible.
Would be very interesting to get a general sense of how tolerant of limited tile failures, tile gaps, imperfect reentry AoA, etc Starship will be with a ~100% steel hull.
Another good image of the tiles during flight, this one from just before the shut down of the first engine. Credit: NickyX15A on YouTube.
The brackets have an interesting asymmetrical structure to them. The plates/fins have inconsistent thickness along their length. It looks to me as though they are meant to bend toward each other to facilitate insertion and then spring back into a home position that captures a female receptacle.I'd assumed the opposite, but the tips are ramped on the outside and the inside, so it's hard to tell. I'm trying to picture some sort of double capture mechanism.
Of particular interest, to me, is what the heck are those asymmetrically positioned posts that protrude into the space between the plates/fins?
[...]Where do you see those? The pins in Jurvetsons photo are all the symmetrical groupings of 3 spaced every 30 cm (long diameter).
Of particular interest, to me, is what the heck are those asymmetrically positioned posts that protrude into the space between the plates/fins?
[...]Where do you see those? The pins in Jurvetsons photo are all the symmetrical groupings of 3 spaced every 30 cm (long diameter).
Of particular interest, to me, is what the heck are those asymmetrically positioned posts that protrude into the space between the plates/fins?
Ah, sorry - I read through that too quickly and thought you were talking about extra pins (posts) in between the tiles (plates).[...]Where do you see those? The pins in Jurvetsons photo are all the symmetrical groupings of 3 spaced every 30 cm (long diameter).
Of particular interest, to me, is what the heck are those asymmetrically positioned posts that protrude into the space between the plates/fins?
I'm talking specifically on a single mounting pin, not the grouping of three. If you look at the zoomed in picture I posted, you'll see that it consists of two blades/fins parallel to one another. Each blade has several surface features of interest.
The first is that there are chamfered protrusions extending outwards from each blade/fin. To my eye, it looks as though they are intended to lock the tile in place by bending inwards until some female receptacle captures them and subsequently allow the blades to spring back to their parallel position.
The second is that there are small horizontally opposed pins/cylinders that extend toward the opposing blade from the inside. They are asymmetrically mounted. I'm curious about what their purpose is.
The third is that there are small cutaways in the bracket plane, near the top, when you look at them from the side.
Hard to tell exactly how long these blades/pins are, but it seems about 5 centimeters or so. If they latch to an internal structure inside the tile and don't reach the surface of the tile, that implies the tiles are a bit thicker than the blades/pins are long, which is surprising, because early prototypes looked thinner than that. Or else, the tiles might not actually be in contact with the tank but that seems unlikely because they would vibrate.There is (or was at one point at least) a "marshmallows-looking" rope seal in between the bottom of the tiles and surface.
Thoughts?
It looks to me as though the outer sides of the pins engage the inside of a metal ring in the tile; some sets of pins seem at random orientations making it hard to see how a bar between the pins would be gripped. The tiles are fairly thick and there may be a gap between the tile inner surface and the steel hull.
I'm thinking snap fit arrangement of some kind. The two "spades" wrapping around a bar of ceramic. Since ceramics are very stiff pretty much any bending would have to be taken up by the metal parts.[...]Where do you see those? The pins in Jurvetsons photo are all the symmetrical groupings of 3 spaced every 30 cm (long diameter).
Of particular interest, to me, is what the heck are those asymmetrically positioned posts that protrude into the space between the plates/fins?
I'm talking specifically on a single mounting pin, not the grouping of three. If you look at the zoomed in picture I posted, you'll see that it consists of two blades/fins parallel to one another. Each blade has several surface features of interest.
The first is that there are chamfered protrusions extending outwards from each blade/fin. To my eye, it looks as though they are intended to lock the tile in place by bending inwards until some female receptacle captures them and subsequently allow the blades to spring back to their parallel position.
The second is that there are small horizontally opposed pins/cylinders that extend toward the opposing blade from the inside. They are asymmetrically mounted. I'm curious about what their purpose is.
The third is that there are small cutaways in the bracket plane, near the top, when you look at them from the side.
it looks to me like each of the pins in a set of 3 pins are orientated 120 deg from each otherThey are.
Not sure if it has been discussed here before but it looks like SN10 fin has some attachment points for heatshield tiles.
Credit: Nomadd
Not sure if it has been discussed here before but it looks like SN10 fin has some attachment points for heatshield tiles.
Credit: Nomadd
Yes and if I’m decoding those triangle patterns correctly it looks as if it might get two different kinds of tile. At least I think I see two sizes of triangles.
It looks to me as though the outer sides of the pins engage the inside of a metal ring in the tile; some sets of pins seem at random orientations making it hard to see how a bar between the pins would be gripped. The tiles are fairly thick and there may be a gap between the tile inner surface and the steel hull.
Pretty sure they sit on a felt pad.
John
Not sure if it has been discussed here before but it looks like SN10 fin has some attachment points for heatshield tiles.
Credit: Nomadd
Not sure if it has been discussed here before but it looks like SN10 fin has some attachment points for heatshield tiles.
Credit: Nomadd
Someone had mentioned why they were on the leeward side if fin and not the heating side.
This is a test of the mechanics of attachment to the Elonerons and not a test of protection.
Testing tile connections on leeward side is to test vibration intensity during launch and ascent.
Leeward side may also protects the tile vibration results from face on airflow during descent .
Incremental testing of each test case. When they’re happy with the vibration and durability test, they will put them on windward side.
My 2 cents
Perhaps there would be less risk of damage to the leading edge (windward side) if a tile would fall off and impact the lower fin.Perhaps there's less effect on the airflow over the fin, so less turbulence. The whole of Starship is a bit of a balancing act so they might well want to avoid extra turbulence especially on the control surfaces.
Sent from my Redmi Note 7 using Tapatalk
Just for reminder, broken tile from SN8. We can see structure inside tile where tile-side weld stud lock sits:So it looks like the "spades" grasp those short cross bars.
(Did falling tile fractures take the felt pad with them, or is it missing at all)
Felt pad inside the tile. OK that makes sens but these things are starting to get really complex. :( :(It looks to me as though the outer sides of the pins engage the inside of a metal ring in the tile; some sets of pins seem at random orientations making it hard to see how a bar between the pins would be gripped. The tiles are fairly thick and there may be a gap between the tile inner surface and the steel hull.
Pretty sure they sit on a felt pad.
John
A felt pad makes sense since the backing should be somewhat compressible. In order to latch, the hook needs to reach a bit beyond the bar it hooks onto, then settle back, and still be snug to not vibrate. Also this allows some variation in tolerances, including due to thermal expansion, and still latch reliably.
Felt pad inside the tile. OK that makes sens but these things are starting to get really complex. :( :(
There are probably fifty factors I'm not considering, but I can see where it could be harder keeping tiles on the leeward side of the flaps if turbulance is a major issue.
As long as the structure a) Doesn't have serious weight limits b) Doesn't have to hold one (or more) l atmospheres of pressure, c) Operate with an inside to outside delta T of up to 1200-1400c d) Has no exposure to high speed air flow that will cause buffeting and could cause resonance then I'd agree with you.Quote from: John Smith 19Felt pad inside the tile. OK that makes sens but these things are starting to get really complex. :( :(
Tile has been layered over a surface that decouples movement of the underlying structure from the tiles for thousands of years.
Not that complicated
I don't see felt pad here, only uncoated white part of the tile. It is possible that the y-shaped structure (seen inside of the broken tile) is designed to take strain of the silicon tile and no felt pad is needed?
The picture is saturated. What's the white material on the backside of the tiles?I don't see felt pad here, only uncoated white part of the tile. It is possible that the y-shaped structure (seen inside of the broken tile) is designed to take strain of the silicon tile and no felt pad is needed?
And other tiles look like there is felt (at least as gap filler) around the outside.
John
The picture is saturated. What's the white material on the backside of the tiles?I don't see felt pad here, only uncoated white part of the tile. It is possible that the y-shaped structure (seen inside of the broken tile) is designed to take strain of the silicon tile and no felt pad is needed?
And other tiles look like there is felt (at least as gap filler) around the outside.
John
The black tiles are quite regular, whereas the white layer is quite irregular and doesn't always match up well with the edges of the black part. To my eye, it looks like these layers are in fact two separate items: the outer layer consists of the black tiles that appear to be consistently identical to a reasonable tolerance, whereas the inner layer consists of separate white felt (?) pads that are quite roughly cut out and only approximately match the footprint of their corresponding tiles.The picture is saturated. What's the white material on the backside of the tiles?I don't see felt pad here, only uncoated white part of the tile. It is possible that the y-shaped structure (seen inside of the broken tile) is designed to take strain of the silicon tile and no felt pad is needed?
And other tiles look like there is felt (at least as gap filler) around the outside.
John
The black tiles are quite regular, whereas the white layer is quite irregular and doesn't always match up well with the edges of the black part. To my eye, it looks like these layers are in fact two separate items: the outer layer consists of the black tiles that appear to be consistently identical to a reasonable tolerance, whereas the inner layer consists of separate white felt (?) pads that are quite roughly cut out and only approximately match the footprint of their corresponding tiles.The picture is saturated. What's the white material on the backside of the tiles?I don't see felt pad here, only uncoated white part of the tile. It is possible that the y-shaped structure (seen inside of the broken tile) is designed to take strain of the silicon tile and no felt pad is needed?
And other tiles look like there is felt (at least as gap filler) around the outside.
John
That's what it looks like to me anyway. As to why one would do it this way, or if this even makes any sense, I leave to those who know what they're actually talking about.
I have to wonder about a tile test rig that could reproduce all flight conditions. It just doesn't seem reasonable that they should have to wait for test flights to discover the tiles aren't holding. Maybe figuring hull flex/vibration/temperature/whatever conditions isn't that easy.
You'd think re-entry would be the hardest, but I still remember that the worst tile loss the Shuttle ever had was on a 747 transport flight.
I have to wonder about a tile test rig that could reproduce all flight conditions. It just doesn't seem reasonable that they should have to wait for test flights to discover the tiles aren't holding. Maybe figuring hull flex/vibration/temperature/whatever conditions isn't that easy.Backside of this steel plate is one intern splashing liquid nitrogen on it, and another one giving it good blows with the hammer. (Third intern takes notes, so it is Science)
You'd think re-entry would be the hardest, but I still remember that the worst tile loss the Shuttle ever had was on a 747 transport flight.
I have to wonder about a tile test rig that could reproduce all flight conditions. It just doesn't seem reasonable that they should have to wait for test flights to discover the tiles aren't holding. Maybe figuring hull flex/vibration/temperature/whatever conditions isn't that easy.Were they lost during that first delivery mission, or simply shipped without tiles so they would be installed for STS-1? There's sources for either scenario.
You'd think re-entry would be the hardest, but I still remember that the worst tile loss the Shuttle ever had was on a 747 transport flight.
I have to wonder about a tile test rig that could reproduce all flight conditions. It just doesn't seem reasonable that they should have to wait for test flights to discover the tiles aren't holding. Maybe figuring hull flex/vibration/temperature/whatever conditions isn't that easy.Were they lost during that first delivery mission, or simply shipped without tiles so they would be installed for STS-1? There's sources for either scenario.
You'd think re-entry would be the hardest, but I still remember that the worst tile loss the Shuttle ever had was on a 747 transport flight.
The robot in the windbreak is presumably for fixing tile studs to the cone? Is the metal rig to provide a firm backing when they do that?I was thinking that the frame might be a jig for the new larger nosecone panels and the robot arm might be to weld them together. It might be for the pins or maybe both.
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2002958;image
Photo credit: Nomadd
Latest video from Mary has a few shots that show heat shield tiles removed from SN5 or SN6.
There is white residue in perfectly hexagonal shapes, maybe some form of adhesive.
From these photos
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=50748.0;attach=2002130;image
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=50748.0;attach=1989664;image
it seems to me like some (or all) of the white material on the back of the tiles was probably viscous at the time of tile placement, because of:
1. Very irregular appearance around the edges
2. Somewhat irregular tile placement
3. White material here and there and inside some tile gaps (maybe alternate explanation of defective/cracked tiles?)
...(They mention heat shields for aerospace industry as one of the applications)I am pretty sure that means near hot engine parts, and not re-entry vehicles...
Even if the the intended use is around engines there might be application for this or something similar, if protected from direct hypersonic flow. The black glassy surface layer does that. The tile gaps may be of too small a scale for local flow to enter. They will be buried in either the stagnation or the relatively slow surface flow. I think....(They mention heat shields for aerospace industry as one of the applications)I am pretty sure that means near hot engine parts, and not re-entry vehicles...
"Nearly four years later on March 8, 1979, Columbia rolled out of the Palmdale facility to begin its multi-day journey across the nation to its launch site, the Kennedy Space Center (KSC) in Florida. The first step was an overland haul to the NASA Dryden Flight Research Center at Edwards Air Force Base (AFB) 36 miles away. Two days later, workers there hoisted Columbia onto the Shuttle Carrier Aircraft (SCA), a Boeing 747 aircraft modified to transport Space Shuttle orbiters. During a test flight, thousands of the orbiter’s temporary thermal protection system tiles fell off. Columbia was returned to the hanger where over 100 men and women worked for nine days reapplying the tiles. Weather then delayed Columbia’s departure until March 20, when the SCA/Shuttle duo flew from Dryden to Biggs AFB in El Paso, Texas, since weather prevented them from reaching their planned refueling stop at Kelly AFB in San Antonio, Texas, until the next day. About 200,000 people went to view the shuttle during its overnight layover in San Antonio. Astronaut Donald K. “Deke” Slayton, program manager for Shuttle Flight Test Operations, was interviewed. After another overnight stop at Eglin AFB in Florida, Columbia atop the SCA touched down at KSC’s Shuttle Landing Facility on March 24."I have to wonder about a tile test rig that could reproduce all flight conditions. It just doesn't seem reasonable that they should have to wait for test flights to discover the tiles aren't holding. Maybe figuring hull flex/vibration/temperature/whatever conditions isn't that easy.Were they lost during that first delivery mission, or simply shipped without tiles so they would be installed for STS-1? There's sources for either scenario.
You'd think re-entry would be the hardest, but I still remember that the worst tile loss the Shuttle ever had was on a 747 transport flight.
My recollection is that the initial delivery of Columbia to KSC was with the tiles
installed. There was horror at how many were lost on that delivery flight
and it took a long time to repair the damage.
Carl
Tiles on aft flapooo! Very good!
Credit: BocaChicaGal
Tiles on aft flapooo! Very good!
Credit: BocaChicaGal
Anyone see any large sections of heatshield on any of the Starships past SN9?
A few TPS tiles on the nosecone barrel section.
SN11 nosecone was hooked up to the crane for a while.
SN15 common dome section stacked in the mid bay.
https://twitter.com/nickyx15a/status/1355214865221246977QuoteSN10 has begun rolling to the street!!!
@SpaceflightIns
Interesting. Maybe some kind of high temperature foamed silicone based system? One problem with bonding is applying pressure consistently during cure.
John
They're probably thinking about field repair. Hard to do with adhesive.
They're probably thinking about field repair. Hard to do with adhesive.
With completely mechanical/fastener-based tile attachment, it might even be possible to do last minute on-orbit replacement. Something as simple as chiseling out the old tile while on EVA and snapping a new one in its place that you got from the pile of identical spares in the cargo hold could make the difference between a normal EDL and another Columbia. I could imagine Starships being accompanied by extendable boom cameras or even free-flying RCS drones that inspect their bellies for damage periodically.
That doesn’t really change his point. A heatshield failure on another spot on the vehicle could’ve also caused the same result. Which is also why NASA developed a method for on-orbit repair of heatshield tiles after Columbia. Basically the same thing he’s talking about.They're probably thinking about field repair. Hard to do with adhesive.
With completely mechanical/fastener-based tile attachment, it might even be possible to do last minute on-orbit replacement. Something as simple as chiseling out the old tile while on EVA and snapping a new one in its place that you got from the pile of identical spares in the cargo hold could make the difference between a normal EDL and another Columbia. I could imagine Starships being accompanied by extendable boom cameras or even free-flying RCS drones that inspect their bellies for damage periodically.
Columbia was due to damaged Reinforced Carbon-Carbon panels on the wing's leading edge.
That doesn’t really change his point. A heatshield failure on another spot on the vehicle could’ve also caused the same result. Which is also why NASA developed a method for on-orbit repair of heatshield tiles after Columbia. Basically the same thing he’s talking about.They're probably thinking about field repair. Hard to do with adhesive.
With completely mechanical/fastener-based tile attachment, it might even be possible to do last minute on-orbit replacement. Something as simple as chiseling out the old tile while on EVA and snapping a new one in its place that you got from the pile of identical spares in the cargo hold could make the difference between a normal EDL and another Columbia. I could imagine Starships being accompanied by extendable boom cameras or even free-flying RCS drones that inspect their bellies for damage periodically.
Columbia was due to damaged Reinforced Carbon-Carbon panels on the wing's leading edge.
Interesting. Maybe some kind of high temperature foamed silicone based system? One problem with bonding is applying pressure consistently during cure.Maybe a two part fast setup mix with a cooperative robot arm to apply pressure for a couple moments. Maybe UV curing like at the dentist? Maybe start the curing without the tile then add the tile with a thin coat of something that reactivates a thin layer of the marshmallow?
John
They're probably thinking about field repair. Hard to do with adhesive.You can fix just about anything with a P38, green 100mph tape and C-rat peanut butter. Two of the three are adhesive.
And it only needs to work one time.That doesn’t really change his point. A heatshield failure on another spot on the vehicle could’ve also caused the same result. Which is also why NASA developed a method for on-orbit repair of heatshield tiles after Columbia. Basically the same thing he’s talking about.They're probably thinking about field repair. Hard to do with adhesive.
With completely mechanical/fastener-based tile attachment, it might even be possible to do last minute on-orbit replacement. Something as simple as chiseling out the old tile while on EVA and snapping a new one in its place that you got from the pile of identical spares in the cargo hold could make the difference between a normal EDL and another Columbia. I could imagine Starships being accompanied by extendable boom cameras or even free-flying RCS drones that inspect their bellies for damage periodically.
Columbia was due to damaged Reinforced Carbon-Carbon panels on the wing's leading edge.
It's important to be accurate with history. In any case, I don't agree that an adhesive based repair method would be obsolete. When a fastener bolt breaks, replacing a tile without adhesive would be hard.
Of note: SN9 did not appear to lose any tiles on the test flight.
At least not until the last moment...
Of note: SN9 did not appear to lose any tiles on the test flight.
At least not until the last moment...
Looking at the frost line on that picture you can see why they put the tiles where they did.
Of note: SN9 did not appear to lose any tiles on the test flight.
At least not until the last moment...
Looking at the frost line on that picture you can see why they put the tiles where they did.
I'm not that concerned with them shedding tiles on these flights. They are really gentle. Being launched on top of a SH and orbital re-entry, that could be the shocker.
The typical hexagon tiles in a field layout seem straight forward enough to make and attach. The specialty tiles around the edges, nose cone and control surfaces. Those will be interesting.
This is going to be a fun year to watch.
I'm not that concerned with them shedding tiles on these flights. They are really gentle. Being launched on top of a SH and orbital re-entry, that could be the shocker.
The lowermost attachment variant ('full height' RCG coating, thin white felt, red RTV silicone) looks very STS. Would be amusing if that ended up being the most successful variant after all!
Compare the 'rippled' red substance to the rippled red RTV silicone of the STS tile mounting system (images attached). With the structure of the tiles themselves being close to identical (other than being 6-sided rather than 4-sided), it it makes sense to test alternate attachment mechanisms vs. a 'known working' mechanism.The lowermost attachment variant ('full height' RCG coating, thin white felt, red RTV silicone) looks very STS. Would be amusing if that ended up being the most successful variant after all!
To me the red stuff looks more like a board of some kind, perhaps some kind of cement board? Although I don’t see how that makes any sense, so you’re probably right.
Original Image credit: Bocachicagal.
February 7th 2021 Updates: Starship priorities
https://twitter.com/elonmusk/status/1358594029101879298
Tweet Contents: What’s your biggest priority with Starship right now? What currently feels like the most uphill battle or most urgent problem to solve?
1. Orbital launch tower that can stack
2. Enough Raptors for orbit booster
3. Improve ship & booster mass
On Mary's pic, the top three sub sized tiles have an interesting structure. This is on SN10, the patch of tiles just below the big patch.I wonder...with these sub-sized tiles, are they planning on using them in combination to create a tesselation up the ogive?
February 7th 2021 Updates: Starship priorities
https://twitter.com/elonmusk/status/1358594029101879298
Tweet Contents: What’s your biggest priority with Starship right now? What currently feels like the most uphill battle or most urgent problem to solve?
1. Orbital launch tower that can stack
2. Enough Raptors for orbit booster
3. Improve ship & booster mass
Somewhat reassuring that Elon doesn't put the heat shield problem in his current top 3 urgent-problems-to-solve list. I think it's been the problem I've be most anxious about with Starship...
Most likely they're testing the adhesion and resilience of various size tiles. There are probably all sorts of cost/ease/sturdiness tradeoffs at every size and they need good data to make a good choice.On Mary's pic, the top three sub sized tiles have an interesting structure. This is on SN10, the patch of tiles just below the big patch.I wonder...with these sub-sized tiles, are they planning on using them in combination to create a tesselation up the ogive?
On the other hand, these tiles ARE the perfect ratio to produce an ogive....I wonder...with these sub-sized tiles, are they planning on using them in combination to create a tesselation up the ogive?Most likely they're testing the adhesion and resilience of various size tiles. There are probably all sorts of cost/ease/sturdiness tradeoffs at every size and they need good data to make a good choice.
On the other hand, these tiles ARE the perfect ratio to produce an ogive....I wonder...with these sub-sized tiles, are they planning on using them in combination to create a tesselation up the ogive?Most likely they're testing the adhesion and resilience of various size tiles. There are probably all sorts of cost/ease/sturdiness tradeoffs at every size and they need good data to make a good choice.
As long as those gaps are small enough that the stainless steel backing can redistribute the heat, that should be survivable.On the other hand, these tiles ARE the perfect ratio to produce an ogive....I wonder...with these sub-sized tiles, are they planning on using them in combination to create a tesselation up the ogive?Most likely they're testing the adhesion and resilience of various size tiles. There are probably all sorts of cost/ease/sturdiness tradeoffs at every size and they need good data to make a good choice.
I'm not seeing it 100%. With perfectly hexagonal tiles like this, aren't there going to be a zillion tiny gaps everywhere? Even accounting for the fact that I edited that diagram on a flat surface in MS paint as opposed to mapped onto a curved surface in 3D space, it's very clear that there will be substantial gaps when you start trying to get the tiles to tessellate perfectly.
As long as those gaps are small enough that the stainless steel backing can redistribute the heat, that should be survivable.On the other hand, these tiles ARE the perfect ratio to produce an ogive....I wonder...with these sub-sized tiles, are they planning on using them in combination to create a tesselation up the ogive?Most likely they're testing the adhesion and resilience of various size tiles. There are probably all sorts of cost/ease/sturdiness tradeoffs at every size and they need good data to make a good choice.
I'm not seeing it 100%. With perfectly hexagonal tiles like this, aren't there going to be a zillion tiny gaps everywhere? Even accounting for the fact that I edited that diagram on a flat surface in MS paint as opposed to mapped onto a curved surface in 3D space, it's very clear that there will be substantial gaps when you start trying to get the tiles to tessellate perfectly.
Insufficient data. I think the relevant numbers would be the steel's heat conductivity and emission to the inside, over whatever the duration and temperature of reentry (given the gaps), and the temperature that removes the "cold rolled" effect that the tanks are taking advantage of. If the gaps are small enough that no part of the hull passes the threshold temperature, (which is an open question, but is what I assume with my post) then there shouldn't be a problem.As long as those gaps are small enough that the stainless steel backing can redistribute the heat, that should be survivable.On the other hand, these tiles ARE the perfect ratio to produce an ogive....I wonder...with these sub-sized tiles, are they planning on using them in combination to create a tesselation up the ogive?Most likely they're testing the adhesion and resilience of various size tiles. There are probably all sorts of cost/ease/sturdiness tradeoffs at every size and they need good data to make a good choice.
I'm not seeing it 100%. With perfectly hexagonal tiles like this, aren't there going to be a zillion tiny gaps everywhere? Even accounting for the fact that I edited that diagram on a flat surface in MS paint as opposed to mapped onto a curved surface in 3D space, it's very clear that there will be substantial gaps when you start trying to get the tiles to tessellate perfectly.
Survivable throughout the lifetime of a given Starship... citation needed?
Its simply not possible to tessellate a tapering curved surface with a single size of hexagonal tile. the gaps and mismatches will grow row upon row. This was discussed right at the start of this thread on page 1.As long as those gaps are small enough that the stainless steel backing can redistribute the heat, that should be survivable.On the other hand, these tiles ARE the perfect ratio to produce an ogive....I wonder...with these sub-sized tiles, are they planning on using them in combination to create a tesselation up the ogive?Most likely they're testing the adhesion and resilience of various size tiles. There are probably all sorts of cost/ease/sturdiness tradeoffs at every size and they need good data to make a good choice.
I'm not seeing it 100%. With perfectly hexagonal tiles like this, aren't there going to be a zillion tiny gaps everywhere? Even accounting for the fact that I edited that diagram on a flat surface in MS paint as opposed to mapped onto a curved surface in 3D space, it's very clear that there will be substantial gaps when you start trying to get the tiles to tessellate perfectly.
February 7th 2021 Updates: Starship priorities
*snip tweet*
Tweet Contents: What’s your biggest priority with Starship right now? What currently feels like the most uphill battle or most urgent problem to solve?
1. Orbital launch tower that can stack
2. Enough Raptors for orbit booster
3. Improve ship & booster mass
Somewhat reassuring that Elon doesn't put the heat shield problem in his current top 3 urgent-problems-to-solve list. I think it's been the problem I've be most anxious about with Starship...
Just means that he's willing to run them as expendables while putting up starlink.
The bolded leads me to believe you have lost the current thread of discussion.Its simply not possible to tessellate a tapering curved surface with a single size of hexagonal tile. the gaps and mismatches will grow row upon row. This was discussed right at the start of this thread on page 1.As long as those gaps are small enough that the stainless steel backing can redistribute the heat, that should be survivable.On the other hand, these tiles ARE the perfect ratio to produce an ogive....I wonder...with these sub-sized tiles, are they planning on using them in combination to create a tesselation up the ogive?Most likely they're testing the adhesion and resilience of various size tiles. There are probably all sorts of cost/ease/sturdiness tradeoffs at every size and they need good data to make a good choice.
I'm not seeing it 100%. With perfectly hexagonal tiles like this, aren't there going to be a zillion tiny gaps everywhere? Even accounting for the fact that I edited that diagram on a flat surface in MS paint as opposed to mapped onto a curved surface in 3D space, it's very clear that there will be substantial gaps when you start trying to get the tiles to tessellate perfectly.
But with two sizes of hexagonal tile in the same ratio currently shown on SN10, you can tesselate an ogive quite efficiently.As long as those gaps are small enough that the stainless steel backing can redistribute the heat, that should be survivable.Its simply not possible to tessellate a tapering curved surface with a single size of hexagonal tile. the gaps and mismatches will grow row upon row. This was discussed right at the start of this thread on page 1.
As effective as the pattern is, I suspect SpaceX will not be putting the weakest part of the pattern, right on the midline where the heating will be the greatest. Perhaps if you offset by half a pattern-width?But with two sizes of hexagonal tile in the same ratio currently shown on SN10, you can tesselate an ogive quite efficiently.As long as those gaps are small enough that the stainless steel backing can redistribute the heat, that should be survivable.Its simply not possible to tessellate a tapering curved surface with a single size of hexagonal tile. the gaps and mismatches will grow row upon row. This was discussed right at the start of this thread on page 1.
I went ahead and wrapped the tile pattern around an ogive with the same proportions as Starship. The largest gaps are only a little larger than the existing gaps between the smaller tiles pictured on SN10 currently, and that's without any rotation of the tiles themselves. If you rotate the tiles then you can have substantially more coverage. You could also have a single uniquely-shaped "keystone" tile to fill the largest gap.
The point is that the exact same pattern can be repeated indefinitely. So you have two tile shapes (max of 3) rather than continuously-shrinking tiles.
If the problem is that they need more shapes of tiles it will be solved eventually...It has already been solved. One potential solution is shown on page 1 of this thread and there are plenty more using multiple tile types. The real questions are how few types you can get away with and how much gap is acceptable. I don't know the answers although I suspect they approximate "to quite a lot" and "not very much" respectively.
Maybe gaps just might be ok with a stainless steel backing, but gaps are not ok for high mach. The tiles will peal off like shingles in a hurricane.It's probably been covered further back but at high mach numbers the air density will be very low and therefore much lower forces on anything even slightly streamlined.
After looking at this image repeatedly I realized there are actually three different sizes of tiles here.
In the Joe Rogan interview with Elon, he points out, that “get the gaps just right” is one of the major problems at this point. I wonder why they can not overlap. Nature came up with this solution a number of times.I think attachment and replacement become problems with overlap. Especially with a dragonskin-style overlap -- you'd have to remove a thousand tiles just to replace one broken one.
Overlapping scales cause problems when not aligned to airflow, and Starship is exposed to airflow in 3 orientations (and 4 directions):
- Aligned along the long axis, nose forward (during launch)
- 70° angle of attack (during entry)
- 90° angle of attack (during skydive)
- Aligned along the long axis, tail first (during landing)
In nature, creatures with overlapping scales either have them aligned to a single axis of flow (swimming creatures), replace scaled areas with membrane areas (pterosaurs, gliding lizards, etc), or evolve those scales in very high aspect ratio feathers that can interlock rather than just layer and whose axis can be reoriented by muscles under the skin (birds).
On top of that, the tiles are 'thick' compared to their other two dimensions: they have a very low aspect ratio. They have a minimum thickness to make them effective as a TPS, and if you make them larger they are both harder to fabricate and more brittle.
Not only size, there was pentagonal tiles on SN9.
Overlapping scales cause problems when not aligned to airflow, and Starship is exposed to airflow in 3 orientations (and 4 directions):
- Aligned along the long axis, nose forward (during launch)
- 70° angle of attack (during entry)
- 90° angle of attack (during skydive)
- Aligned along the long axis, tail first (during landing)
In nature, creatures with overlapping scales either have them aligned to a single axis of flow (swimming creatures), replace scaled areas with membrane areas (pterosaurs, gliding lizards, etc), or evolve those scales in very high aspect ratio feathers that can interlock rather than just layer and whose axis can be reoriented by muscles under the skin (birds).
On top of that, the tiles are 'thick' compared to their other two dimensions: they have a very low aspect ratio. They have a minimum thickness to make them effective as a TPS, and if you make them larger they are both harder to fabricate and more brittle.
Airflow in subsonic or even transonic flight has got to be completely irrelevant. Of the three stages of EDL ypu listed, only the reenty part will have concerning aero forces on the shell. What isn't trivial though, is winds experienced on ascent. Surface finish has a huge effect on drag, and overlapping scales would probably cut into payload capacity for that reason.
Overlapping scales cause problems when not aligned to airflow, and Starship is exposed to airflow in 3 orientations (and 4 directions):
- Aligned along the long axis, nose forward (during launch)
- 70° angle of attack (during entry)
- 90° angle of attack (during skydive)
- Aligned along the long axis, tail first (during landing)
In nature, creatures with overlapping scales either have them aligned to a single axis of flow (swimming creatures), replace scaled areas with membrane areas (pterosaurs, gliding lizards, etc), or evolve those scales in very high aspect ratio feathers that can interlock rather than just layer and whose axis can be reoriented by muscles under the skin (birds).
On top of that, the tiles are 'thick' compared to their other two dimensions: they have a very low aspect ratio. They have a minimum thickness to make them effective as a TPS, and if you make them larger they are both harder to fabricate and more brittle.
Airflow in subsonic or even transonic flight has got to be completely irrelevant. Of the three stages of EDL ypu listed, only the reenty part will have concerning aero forces on the shell. What isn't trivial though, is winds experienced on ascent. Surface finish has a huge effect on drag, and overlapping scales would probably cut into payload capacity for that reason.
If you want my prediction, I think SpaceX will be filling those gaps with specialty tiles. This isn't the space shuttle. It won't be the end of the world if they end up needing to make two kinds of hinge tile, two kinds of flap edge tile, six or seven types of gap tile for the nose, and a nose tile. There's a big difference between producing that versus 24,000 unique individual tiles.
Overlapping scales cause problems when not aligned to airflow, and Starship is exposed to airflow in 3 orientations (and 4 directions):
- Aligned along the long axis, nose forward (during launch)
- 70° angle of attack (during entry)
- 90° angle of attack (during skydive)
- Aligned along the long axis, tail first (during landing)
In nature, creatures with overlapping scales either have them aligned to a single axis of flow (swimming creatures), replace scaled areas with membrane areas (pterosaurs, gliding lizards, etc), or evolve those scales in very high aspect ratio feathers that can interlock rather than just layer and whose axis can be reoriented by muscles under the skin (birds).
On top of that, the tiles are 'thick' compared to their other two dimensions: they have a very low aspect ratio. They have a minimum thickness to make them effective as a TPS, and if you make them larger they are both harder to fabricate and more brittle.
Airflow in subsonic or even transonic flight has got to be completely irrelevant. Of the three stages of EDL ypu listed, only the reenty part will have concerning aero forces on the shell. What isn't trivial though, is winds experienced on ascent. Surface finish has a huge effect on drag, and overlapping scales would probably cut into payload capacity for that reason.
If you want my prediction, I think SpaceX will be filling those gaps with specialty tiles. This isn't the space shuttle. It won't be the end of the world if they end up needing to make two kinds of hinge tile, two kinds of flap edge tile, six or seven types of gap tile for the nose, and a nose tile. There's a big difference between producing that versus 24,000 unique individual tiles.
Have you seen what a tornado will do to shingles on the roof of a house? Even the most powerful tornados are low speed subsonic, very comparable to the terminal velocity of Starship at the end of its belly flop maneuver when it flips to upright to land. Don't underestimate aerodynamic forces.
In the Joe Rogan interview with Elon, he points out, that “get the gaps just right” is one of the major problems at this point. I wonder why they can not overlap. Nature came up with this solution a number of times.
In the Joe Rogan interview with Elon, he points out, that “get the gaps just right” is one of the major problems at this point. I wonder why they can not overlap. Nature came up with this solution a number of times.I think attachment and replacement become problems with overlap. Especially with a dragonskin-style overlap -- you'd have to remove a thousand tiles just to replace one broken one.
Overlap also creates problems with thickness and edge exposure. Do you make the tiles half as thick as they need to be and do two layers? What happens to the ones with an edge exposed to the re-entry plasma?
But not orthogonal flow, as in ascent.Overlapping scales cause problems when not aligned to airflow, and Starship is exposed to airflow in 3 orientations (and 4 directions):
- Aligned along the long axis, nose forward (during launch)
- 70° angle of attack (during entry)
- 90° angle of attack (during skydive)
- Aligned along the long axis, tail first (during landing)
In nature, creatures with overlapping scales either have them aligned to a single axis of flow (swimming creatures), replace scaled areas with membrane areas (pterosaurs, gliding lizards, etc), or evolve those scales in very high aspect ratio feathers that can interlock rather than just layer and whose axis can be reoriented by muscles under the skin (birds).
On top of that, the tiles are 'thick' compared to their other two dimensions: they have a very low aspect ratio. They have a minimum thickness to make them effective as a TPS, and if you make them larger they are both harder to fabricate and more brittle.
Airflow in subsonic or even transonic flight has got to be completely irrelevant. Of the three stages of EDL ypu listed, only the reenty part will have concerning aero forces on the shell. What isn't trivial though, is winds experienced on ascent. Surface finish has a huge effect on drag, and overlapping scales would probably cut into payload capacity for that reason.
If you want my prediction, I think SpaceX will be filling those gaps with specialty tiles. This isn't the space shuttle. It won't be the end of the world if they end up needing to make two kinds of hinge tile, two kinds of flap edge tile, six or seven types of gap tile for the nose, and a nose tile. There's a big difference between producing that versus 24,000 unique individual tiles.
Have you seen what a tornado will do to shingles on the roof of a house? Even the most powerful tornados are low speed subsonic, very comparable to the terminal velocity of Starship at the end of its belly flop maneuver when it flips to upright to land. Don't underestimate aerodynamic forces.
The angle of attack is only 70 degrees or better on Starship, and roofing tiles aren't equivalent to house tiles. Besides, I'm just saying that those stages of EDL aren't relevant. If the tiles can stand escape-velocity-plus-C3 speeds at 70 degrees, of course they can withstand 0.9 mach at 90 degrees or 30 meters per second during the landing flip.
But not orthogonal flow, as in ascent.Overlapping scales cause problems when not aligned to airflow, and Starship is exposed to airflow in 3 orientations (and 4 directions):
- Aligned along the long axis, nose forward (during launch)
- 70° angle of attack (during entry)
- 90° angle of attack (during skydive)
- Aligned along the long axis, tail first (during landing)
In nature, creatures with overlapping scales either have them aligned to a single axis of flow (swimming creatures), replace scaled areas with membrane areas (pterosaurs, gliding lizards, etc), or evolve those scales in very high aspect ratio feathers that can interlock rather than just layer and whose axis can be reoriented by muscles under the skin (birds).
On top of that, the tiles are 'thick' compared to their other two dimensions: they have a very low aspect ratio. They have a minimum thickness to make them effective as a TPS, and if you make them larger they are both harder to fabricate and more brittle.
Airflow in subsonic or even transonic flight has got to be completely irrelevant. Of the three stages of EDL ypu listed, only the reenty part will have concerning aero forces on the shell. What isn't trivial though, is winds experienced on ascent. Surface finish has a huge effect on drag, and overlapping scales would probably cut into payload capacity for that reason.
If you want my prediction, I think SpaceX will be filling those gaps with specialty tiles. This isn't the space shuttle. It won't be the end of the world if they end up needing to make two kinds of hinge tile, two kinds of flap edge tile, six or seven types of gap tile for the nose, and a nose tile. There's a big difference between producing that versus 24,000 unique individual tiles.
Have you seen what a tornado will do to shingles on the roof of a house? Even the most powerful tornados are low speed subsonic, very comparable to the terminal velocity of Starship at the end of its belly flop maneuver when it flips to upright to land. Don't underestimate aerodynamic forces.
The angle of attack is only 70 degrees or better on Starship, and roofing tiles aren't equivalent to house tiles. Besides, I'm just saying that those stages of EDL aren't relevant. If the tiles can stand escape-velocity-plus-C3 speeds at 70 degrees, of course they can withstand 0.9 mach at 90 degrees or 30 meters per second during the landing flip.
Lapped structures are flow optimal only in one axis, and get progressively worse as you deviate from that axis. Starship experiences dense flow at high velocities (high subsonic and above supersonic) on orthogonal axes.
Nocapesoverlap!
Covering this section with sheets of ?
(https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2013503;image)
I'm not entirely certain, but I believe that the material on this starship section is Kaowool. It's an amazingly insulative material that I have personal experience with using in metal foundries, and it can handle sustained temperatures in excess of 1,000° C.
If you would like to know more, here is a useful website that goes into greater detail about its properties: https://www.foundryservice.com/product/kaowool-blanket-products-1800of-2600of-insulation-blankets/kaowool-blanket/ (https://www.foundryservice.com/product/kaowool-blanket-products-1800of-2600of-insulation-blankets/kaowool-blanket/)
Covering this section with sheets of ?
(https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2013503;image)
Looks like liner for tiles to me. Could be the first SN in the works to get a full heat shield.
Red silicone.The lowermost attachment variant ('full height' RCG coating, thin white felt, red RTV silicone) looks very STS. Would be amusing if that ended up being the most successful variant after all!
To me the red stuff looks more like a board of some kind, perhaps some kind of cement board? Although I don’t see how that makes any sense, so you’re probably right.
Original Image credit: Bocachicagal.
I find it curious that they might be doing a full heatshield (might being the key word here) yet we haven't seen any tiles on any nosecones yet (or have I missed it?). For that matter, we haven't spotted tiles either on aero covers or close to any hinge points. Who knows, they might just go for it assuming they are confident enough in the fastening mechanism to fix tiles everywhere by now. Perhaps getting tiles so stay on the tank section during multiple regimes is the hardest part.I know that Elon says he does the hard parts first. But these body tiles may be "hard enough". Once they can get the tiles to stay on the cylinder, they can try using a similar technique on flaps and conical sections. Going the other way might not help since the specialty applications may be more difficult than necessary when applied to the cylinder. Also just thinking out loud. :)
Just thinking out loud here.
So my eye balling guess is the that the fins are about 1/3 of the cross sectional area?Peak heat flux and total heat load both scale roughly as (ballistic coefficient)1/2 for convective heating. So peak temperature would go as (BC)1/8.
Anybody else actually calculated it from the dimensions?
So what is the formula for ballistic coefficient to peak heating? Total heat load? I thought there was a square term somewhere in there.
So I am trying to get an idea of how much the lower ballistic coefficient helps?
thanks.So my eye balling guess is the that the fins are about 1/3 of the cross sectional area?Peak heat flux and total heat load both scale roughly as (ballistic coefficient)1/2 for convective heating. So peak temperature would go as (BC)1/8.
Anybody else actually calculated it from the dimensions?
So what is the formula for ballistic coefficient to peak heating? Total heat load? I thought there was a square term somewhere in there.
So I am trying to get an idea of how much the lower ballistic coefficient helps?
The flaps will increase the effective radius of the cylindrical body when deployed beyond the Mach angle so their contribution will be larger than just their projected area. My guess is that there has been "a few" simulation runs to figure out how far they can deploy them before impacting lift and stability.
An interesting consequence of having larger aft flaps is that the max payload reentries might have a slightly disproportionate increase in ballistic coefficient...
[...]I have found this useful for back-of-the-envelope (or wolframalpha) calculations (PDF): https://tfaws.nasa.gov/TFAWS12/Proceedings/Aerothermodynamics%20Course.pdf
I found this formula for peak heat flux.
qdot = 1.83E-4*v^3*sqrt(rho/radius)
v=velocity
rho=atmospheric density kg/m^3
radius of nose
qdot=watts/m^2
So my eye balling guess is the that the fins are about 1/3 of the cross sectional area?I calculated the projected areas from dimensions as best we know:
Anybody else actually calculated it from the dimensions?
So what is the formula for ballistic coefficient to peak heating? Total heat load? I thought there was a square term somewhere in there.
So I am trying to get an idea of how much the lower ballistic coefficient helps?
So my eye balling guess is the that the fins are about 1/3 of the cross sectional area?I calculated the projected areas from dimensions as best we know:
Anybody else actually calculated it from the dimensions?
So what is the formula for ballistic coefficient to peak heating? Total heat load? I thought there was a square term somewhere in there.
So I am trying to get an idea of how much the lower ballistic coefficient helps?
cylinder + nosecone= 412 m2
Forward fins +aft fins+ the root chines at 90 deg AoA=160m2
Looking at SN11 the shielded area is roughly double, at this rate we'll have to wait for SN20 or more to get a full heatshield that can face re-entry.
SN11 has 360 tiles on the body, unsure if any on the flaps. SN10 had 246. Interesting to watch it grow over time.I'm confused - what advantage would there be in having the greater number of tiles?
SN11 has 360 tiles on the body, unsure if any on the flaps. SN10 had 246. Interesting to watch it grow over time.I'm confused - what advantage would there be in having the greater number of tiles?
Yes, that's what I assumed they meant.SN11 has 360 tiles on the body, unsure if any on the flaps. SN10 had 246. Interesting to watch it grow over time.I'm confused - what advantage would there be in having the greater number of tiles?
I think they mean more coverage of the prototypes, not a greater number of tiles for a full heatshield.
You get more practice installing them and better statistics on the installation processes and mechanical/thermal performance.Yes, that's what I assumed they meant.SN11 has 360 tiles on the body, unsure if any on the flaps. SN10 had 246. Interesting to watch it grow over time.I'm confused - what advantage would there be in having the greater number of tiles?
I think they mean more coverage of the prototypes, not a greater number of tiles for a full heatshield.
But why have more tiles on the prototypes? What does the larger patch tell you that the smaller one doesn't?
And maybe as prototypes are built and SX sees the likelihood of each crashing shrink they're willing to install more tiles.You get more practice installing them and better statistics on the installation processes and mechanical/thermal performance.Yes, that's what I assumed they meant.SN11 has 360 tiles on the body, unsure if any on the flaps. SN10 had 246. Interesting to watch it grow over time.I'm confused - what advantage would there be in having the greater number of tiles?
I think they mean more coverage of the prototypes, not a greater number of tiles for a full heatshield.
But why have more tiles on the prototypes? What does the larger patch tell you that the smaller one doesn't?
But if the justification is practice and data gathering, why not just put on the full set?And maybe as prototypes are built and SX sees the likelihood of each crashing shrink they're willing to install more tiles.You get more practice installing them and better statistics on the installation processes and mechanical/thermal performance.Yes, that's what I assumed they meant.SN11 has 360 tiles on the body, unsure if any on the flaps. SN10 had 246. Interesting to watch it grow over time.I'm confused - what advantage would there be in having the greater number of tiles?
I think they mean more coverage of the prototypes, not a greater number of tiles for a full heatshield.
But why have more tiles on the prototypes? What does the larger patch tell you that the smaller one doesn't?
Cost? and of course they don't really need the full heatshield for actually protecting the vehicle until probably >SN15 so might as well work your way upBut if the justification is practice and data gathering, why not just put on the full set?And maybe as prototypes are built and SX sees the likelihood of each crashing shrink they're willing to install more tiles.You get more practice installing them and better statistics on the installation processes and mechanical/thermal performance.Yes, that's what I assumed they meant.SN11 has 360 tiles on the body, unsure if any on the flaps. SN10 had 246. Interesting to watch it grow over time.I'm confused - what advantage would there be in having the greater number of tiles?
I think they mean more coverage of the prototypes, not a greater number of tiles for a full heatshield.
But why have more tiles on the prototypes? What does the larger patch tell you that the smaller one doesn't?
Yep, OK. So that means they need to use the smallest area they can.Cost? and of course they don't really need the full heatshield for actually protecting the vehicle until probably >SN15 so might as well work your way upBut if the justification is practice and data gathering, why not just put on the full set?And maybe as prototypes are built and SX sees the likelihood of each crashing shrink they're willing to install more tiles.Yes, that's what I assumed they meant.You get more practice installing them and better statistics on the installation processes and mechanical/thermal performance.
But why have more tiles on the prototypes? What does the larger patch tell you that the smaller one doesn't?
I have also been wondering if they will get better or worse landing profiles with more of the heat shield installed as, the additional mass of the heatshield moves the center of mass of Starship ( in the X-Y plane ) away from the geometric centerline of the vehicle. I had a hard time finding reliable guestimates of the heatshield mass, but a 15t heatshield would make a 662kN*m moment arm.
If the landing is to be on two engines, it seems like you want to prioritize moving the CoM towards the thrust vector of the primary landing engines. That would minimize the off axis gimbal angle needed for the asymetric CoM. Would it even be possible to move the centroid three center raptors slightly towards the asymetic CG to have better control in nominal & off nominal landings?
I'm trying to figure out if anyone has a theory on why SN11 has more than SN10.
I'll throw in a theory of my own, just to move the discussion on: they have a fixed "budget" for tiles on each prototype, and they are getting better at installing them so the same budget lets them install more tiles.
Yep, though you could argue that manufacturing capacity is just how they determine the "tile budget" for each SN, so it's basically a variant.I'm trying to figure out if anyone has a theory on why SN11 has more than SN10.
I'll throw in a theory of my own, just to move the discussion on: they have a fixed "budget" for tiles on each prototype, and they are getting better at installing them so the same budget lets them install more tiles.
They might still be trying out slightly different tile manufacturing / ramping up manufacturing. Wasn't there something about that in a job ad?
Didn't SN10 also have a significant area of unused attachment studs? They might not have had enough tiles to populate it. Or it was just the stud robot going nuts. :)
I'm not at all sure either why the amount of heat shield would increase but not so quickly.
Why do they use half-tiles on the top and bottom, but not the left and right?They will have to use half tiles at the bottom at least, but need not used half tiles at the sides (although they might)
Can you imagine Elon letting them build it (the "final" version) without straight sides? He wants his spaceships to look good.Why do they use half-tiles on the top and bottom, but not the left and right?They will have to use half tiles at the bottom at least, but need not used half tiles at the sides (although they might)
IIRC, SN10 had tiles on the body and flaps. My guess is that they're testing various points to see how they behave during ascent and landing (vibration, etc.). At some point I imagine the heat shield engineers will say, how about successfully landing one of these beasts so we can take a look at the results! :)Yes, that's what I assumed they meant.SN11 has 360 tiles on the body, unsure if any on the flaps. SN10 had 246. Interesting to watch it grow over time.I'm confused - what advantage would there be in having the greater number of tiles?
I think they mean more coverage of the prototypes, not a greater number of tiles for a full heatshield.
But why have more tiles on the prototypes? What does the larger patch tell you that the smaller one doesn't?
Looking at Nomadd's photos (and others'), there are regularly spaced holes in the flap fairings - has this been seen on past SN's? Is it possible they'll vent the engine chill gases through these holes behind tiles to cool the harder-to-shield complex moving flap interface?
Nomadd's photo here.
What we haven't seen is tiles on the hard parts. My first take on images of 11 coming out of the high bay was that they had some patches on the nose. Closer examination showed it to be the lifting shackles.I'm trying to figure out if anyone has a theory on why SN11 has more than SN10.
I'll throw in a theory of my own, just to move the discussion on: they have a fixed "budget" for tiles on each prototype, and they are getting better at installing them so the same budget lets them install more tiles.
They might still be trying out slightly different tile manufacturing / ramping up manufacturing. Wasn't there something about that in a job ad?
Didn't SN10 also have a significant area of unused attachment studs? They might not have had enough tiles to populate it. Or it was just the stud robot going nuts. :)
My completely uninformed guess is that the heat shield-attaching processes are being worked out, but it's not a high priority because you want to adjust things in response to high-fidelity real data about how it performs in use, which they only get so much of in these tests where there's no heat to shield. There's no incentive to spend a lot of time optimizing things for an objective you haven't tested yet.To ease into the changes more tiles make in handling?
I'm not at all sure either why the amount of heat shield would increase but not so quickly.
Looking at Nomadd's photos (and others'), there are regularly spaced holes in the flap fairings - has this been seen on past SN's? Is it possible they'll vent the engine chill gases through these holes behind tiles to cool the harder-to-shield complex moving flap interface?
Nomadd's photo here.
They allow access to the aerocover frame fixings. See this image from bocachicagal of some delivered last month.
https://twitter.com/cooper_hime/status/1369016118459965443Further up thread someone mentioned it looked similar to Kaowool
That white layer looks like a felt pad to me. What do you guys think?
Further up thread someone mentioned it looked similar to Kaowool
I'm starting to think of the tiles as a way to protect the Kaowool from wind and keep it in place mechanically.
i.e. the tile's function is mechanical, not really insulation. Of course it has to survive insane amounts of heat to do its job, so some insulation properties are needed to protect the connection point to the hull.
A quick edit I made showing the progression between the amounts of heat shield tiles on #Starship SNs 8-11. #SpaceX has definitely been piling them on as of late!
And to think, we could soon see one with a full TPS layout. 👀
📸: Me, @thejackbeyer
I'm starting to think of the tiles as a way to protect the Kaowool from wind and keep it in place mechanically.
i.e. the tile's function is mechanical, not really insulation. Of course it has to survive insane amounts of heat to do its job, so some insulation properties are needed to protect the connection point to the hull.
Even crazier idea: If Kaowool is the main insulator and we just need a mechanical system to keep it in place and prevent it from blowing away in a Mach 2.5 wind (max Q), why not just keep it place with a high temperature wire mesh?
For example a Tungsten wire mesh. https://metalcutting.com/knowledge-center/properties-applications-tungsten-wire/
I suspect there are weaving machines that could mass produce a wire mesh.
Question is whether a tungsten mesh could be made light enough is a good question. Off to hit the calculator.
EDIT: actual tungsten meshes (and inconel): https://nickel-wiremesh.com/material/tungsten-mesh/
Better, but still; if those were floor tiles I'll would fire the contractor and send tiles back to manufacturer...
https://twitter.com/cnunezimages/status/1369389055826419716Ha, that dude just took picture of his bathroom tiles... And you can't tell me otherwise
How does the heatshield handle water trapped and absorbed from rain? especially the felt or wool, but also the ceramic tiles? how did the shuttle handle this issue?
How does the heatshield handle water trapped and absorbed from rain? especially the felt or wool, but also the ceramic tiles? how did the shuttle handle this issue?
How does the heatshield handle water trapped and absorbed from rain? especially the felt or wool, but also the ceramic tiles? how did the shuttle handle this issue?
Given its flying up to vaccum, any water would probably vaporise once in orbit and then escape if not completely sealed in.
Impregnated with what? Shuttle and Starship.How does the heatshield handle water trapped and absorbed from rain? especially the felt or wool, but also the ceramic tiles? how did the shuttle handle this issue?
Shuttle tiles were impregnated. And had to be re-impregnated after every flight because re-entry evaporated the stuff.
According to environmental statement info for Starship tile production (the same facility where Shuttle tiles were made, in fact) the Starship tiles are impregnated too (using similar, but different substance).
I don't know what the do (if anything) for that insulating under-tile mat, though.
How does the heatshield handle water trapped and absorbed from rain? especially the felt or wool, but also the ceramic tiles? how did the shuttle handle this issue?
Shuttle tiles were impregnated. And had to be re-impregnated after every flight because re-entry evaporated the stuff.
According to environmental statement info for Starship tile production (the same facility where Shuttle tiles were made, in fact) the Starship tiles are impregnated too (using similar, but different substance).
I don't know what the do (if anything) for that insulating under-tile mat, though.
How does the heatshield handle water trapped and absorbed from rain? especially the felt or wool, but also the ceramic tiles? how did the shuttle handle this issue?
Shuttle tiles were impregnated. And had to be re-impregnated after every flight because re-entry evaporated the stuff.
According to environmental statement info for Starship tile production (the same facility where Shuttle tiles were made, in fact) the Starship tiles are impregnated too (using similar, but different substance).
I don't know what the do (if anything) for that insulating under-tile mat, though.
I undestand the Shuttle had an under-tile mat or felt as well. Do you know if/how was that protected from rainwater?
Wow, this is a super-simple tile application technique. Is that all that is required, or does it need to be welded into place somehow?From what we have seen so far it does look like it is that simple:
[Tweet]
Wow, this is a super-simple tile application technique. Is that all that is required, or does it need to be welded into place somehow?From what we have seen so far it does look like it is that simple:
[Tweet]
Robot welds studs onto the barrel. Studs have two tapered prongs with some kind of hooking/latching protrusion at the end. Three studs per tile.
High temperature mineral/refractory cheramic fiber mats are fitted to the barrel side and the studs are pressed through. No sign of further fastening but it is not ruled out.
Tiles are pressed fitted onto the studs, slightly compressing the mat until looked in place.
Cracked or faulty tiles can be removed by piercing the tile with a sharp metal object at the location of the three studs (likely just breaking the tile around the attachment points).
I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
Better not let AI drive cars then ;DI'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
Generally there is rule of thump for automation. If human cannot do task blindfolded you should not do robotization of that process.
Oh - I thought the rule of thump was if at first it doesn’t fit, thump it in...I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
Generally there is rule of thump for automation. If human cannot do task blindfolded you should not do robotization of that process.
I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
I would agree - The step requiring the most time and precision, welding the studs, is already automated (at least for the barrel sections).I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.Elon has already made the mistake of over-automating, it doesn’t work. People are far superior to machines when it comes to work like this. What may be simple to humans can be complex for machines vice versa.
I would agree - The step requiring the most time and precision, welding the studs, is already automated (at least for the barrel sections).I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.Elon has already made the mistake of over-automating, it doesn’t work. People are far superior to machines when it comes to work like this. What may be simple to humans can be complex for machines vice versa.
From the videos it takes two SpaceXers 4 minutes to install ~4 m2 of insulation blanket/mat and ~10 s for one person to attach one tile. Rounding a bit that is ~5 person-minutes/m2 for blanket+tile installation which extrapolates to < 80 person-hours of slightly variable and delicate (but not especially physically demanding or difficult) work for the whole ~800 m2 heat shield. Hardly seems like a prime target for automation even if you add a magnitude for overhead and any finicky bits...
Oh - I thought the rule of thump was if at first it doesn’t fit, thump it in...I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
Generally there is rule of thump for automation. If human cannot do task blindfolded you should not do robotization of that process.
But if you plan to build at least 100 Starships you can afford to invest $1m in automation for it.I would agree - The step requiring the most time and precision, welding the studs, is already automated (at least for the barrel sections).I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.Elon has already made the mistake of over-automating, it doesn’t work. People are far superior to machines when it comes to work like this. What may be simple to humans can be complex for machines vice versa.
From the videos it takes two SpaceXers 4 minutes to install ~4 m2 of insulation blanket/mat and ~10 s for one person to attach one tile. Rounding a bit that is ~5 person-minutes/m2 for blanket+tile installation which extrapolates to < 80 person-hours of slightly variable and delicate (but not especially physically demanding or difficult) work for the whole ~800 m2 heat shield. Hardly seems like a prime target for automation even if you add a magnitude for overhead and any finicky bits...
Less than $10,000 in labor per Starship if we assume even a $50/hr cost. Literally peanuts. Plus they can perform QA at the same time.
But if you plan to build at least 100 Starships you can afford to invest $1m in automation for it.I would agree - The step requiring the most time and precision, welding the studs, is already automated (at least for the barrel sections).I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.Elon has already made the mistake of over-automating, it doesn’t work. People are far superior to machines when it comes to work like this. What may be simple to humans can be complex for machines vice versa.
From the videos it takes two SpaceXers 4 minutes to install ~4 m2 of insulation blanket/mat and ~10 s for one person to attach one tile. Rounding a bit that is ~5 person-minutes/m2 for blanket+tile installation which extrapolates to < 80 person-hours of slightly variable and delicate (but not especially physically demanding or difficult) work for the whole ~800 m2 heat shield. Hardly seems like a prime target for automation even if you add a magnitude for overhead and any finicky bits...
Less than $10,000 in labor per Starship if we assume even a $50/hr cost. Literally peanuts. Plus they can perform QA at the same time.
True - though this task looks (ultimately) tailor made for automation.But if you plan to build at least 100 Starships you can afford to invest $1m in automation for it.I would agree - The step requiring the most time and precision, welding the studs, is already automated (at least for the barrel sections).I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.Elon has already made the mistake of over-automating, it doesn’t work. People are far superior to machines when it comes to work like this. What may be simple to humans can be complex for machines vice versa.
From the videos it takes two SpaceXers 4 minutes to install ~4 m2 of insulation blanket/mat and ~10 s for one person to attach one tile. Rounding a bit that is ~5 person-minutes/m2 for blanket+tile installation which extrapolates to < 80 person-hours of slightly variable and delicate (but not especially physically demanding or difficult) work for the whole ~800 m2 heat shield. Hardly seems like a prime target for automation even if you add a magnitude for overhead and any finicky bits...
Less than $10,000 in labor per Starship if we assume even a $50/hr cost. Literally peanuts. Plus they can perform QA at the same time.
Automation doesn't always work better than people.
But if you plan to build at least 100 Starships you can afford to invest $1m in automation for it.I would agree - The step requiring the most time and precision, welding the studs, is already automated (at least for the barrel sections).I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.Elon has already made the mistake of over-automating, it doesn’t work. People are far superior to machines when it comes to work like this. What may be simple to humans can be complex for machines vice versa.
From the videos it takes two SpaceXers 4 minutes to install ~4 m2 of insulation blanket/mat and ~10 s for one person to attach one tile. Rounding a bit that is ~5 person-minutes/m2 for blanket+tile installation which extrapolates to < 80 person-hours of slightly variable and delicate (but not especially physically demanding or difficult) work for the whole ~800 m2 heat shield. Hardly seems like a prime target for automation even if you add a magnitude for overhead and any finicky bits...
Less than $10,000 in labor per Starship if we assume even a $50/hr cost. Literally peanuts. Plus they can perform QA at the same time.
A significant number of drivers would do no worse blindfolded. :'(Better not let AI drive cars then ;DI'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
Generally there is rule of thump for automation. If human cannot do task blindfolded you should not do robotization of that process.
I suspect that once they've fully tiled a Starship and verified that the mounting process is robust they will invest in automation of it. For the moment they don't actually know whether they'll stick with this method, so any investment would be at risk.
I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
Elon has already made the mistake of over-automating, it doesn’t work. People are far superior to machines when it comes to work like this. What may be simple to humans can be complex for machines vice versa.
You have to wonder why drive-up ATMs have braille on the keypads.... ;)A significant number of drivers would do no worse blindfolded. :'(Better not let AI drive cars then ;DI'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
Generally there is rule of thump for automation. If human cannot do task blindfolded you should not do robotization of that process.
I suspect that once they've fully tiled a Starship and verified that the mounting process is robust they will invest in automation of it. For the moment they don't actually know whether they'll stick with this method, so any investment would be at risk.
But if you plan to build at least 100 Starships you can afford to invest $1m in automation for it.I would agree - The step requiring the most time and precision, welding the studs, is already automated (at least for the barrel sections).I'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.Elon has already made the mistake of over-automating, it doesn’t work. People are far superior to machines when it comes to work like this. What may be simple to humans can be complex for machines vice versa.
From the videos it takes two SpaceXers 4 minutes to install ~4 m2 of insulation blanket/mat and ~10 s for one person to attach one tile. Rounding a bit that is ~5 person-minutes/m2 for blanket+tile installation which extrapolates to < 80 person-hours of slightly variable and delicate (but not especially physically demanding or difficult) work for the whole ~800 m2 heat shield. Hardly seems like a prime target for automation even if you add a magnitude for overhead and any finicky bits...
Less than $10,000 in labor per Starship if we assume even a $50/hr cost. Literally peanuts. Plus they can perform QA at the same time.
I agree. Over a decade ago I developed vision systems/sensor suites for use with Kuka robots that did a very similar operation. The pick-and-place operation moved at a little bit faster than one second per installation. Not only was it more than ten times faster than a human could do it, the error rate was non-existent because the sensing systems did post-placement inspection, eliminating the need for separate QA. The cost of this system was significantly less than one million dollars.
Better not let AI drive cars then ;DI'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
Generally there is rule of thump for automation. If human cannot do task blindfolded you should not do robotization of that process.
I suspect that once they've fully tiled a Starship and verified that the mounting process is robust they will invest in automation of it. For the moment they don't actually know whether they'll stick with this method, so any investment would be at risk.
Better not let AI drive cars then ;DI'm surprised to see workers mounting tiles manually. It looks simple to automate and that might happen later.
Generally there is rule of thump for automation. If human cannot do task blindfolded you should not do robotization of that process.
I suspect that once they've fully tiled a Starship and verified that the mounting process is robust they will invest in automation of it. For the moment they don't actually know whether they'll stick with this method, so any investment would be at risk.
Not even a risk. At current conceptual stage that would even be completely pointless and waste of resources. Sure they could throw ideas around and do mini test or two. So yeah
Later when u got everything set and proved trough orbital test, they will probably take o look into:
-assembly automation
-AI scanning after flight
-repair and its replacement
-reusability and take a look Mars robot version
Wow, this is a super-simple tile application technique. Is that all that is required, or does it need to be welded into place somehow?From what we have seen so far it does look like it is that simple:
[Tweet]
Robot welds studs onto the barrel. Studs have two tapered prongs with some kind of hooking/latching protrusion at the end. Three studs per tile.
High temperature mineral/refractory cheramic fiber mats are fitted to the barrel side and the studs are pressed through. No sign of further fastening but it is not ruled out.
Tiles are pressed fitted onto the studs, slightly compressing the mat until looked in place.
Cracked or faulty tiles can be removed by piercing the tile with a sharp metal object at the location of the three studs (likely just breaking the tile around the attachment points).
I am surprised that there is no overlap between blankets. Might be something we will see in future.
May also see longer blanket in the future. Might be awkward working with longer blankets in the horizontal direction but perhaps vertically starting from the top could be fairly easy.
Set up a scaffold while one worker is pushing the blanket over the studs a worker on the level above could be installing the tiles.
Isn't it true that each tile has an embedded, trilaterally-symmetric metal "Y" shaped skeleton to stiffen it? I swear I saw that sonewhere. Removing tiles might mean just whacking over the stud points with a hammer until enough of the ceramic is chipped away that you can directly get at the backside of the skeleton. Then the studs can be unclipped and the tile removed without having to be completely destroyed. You could even do this on-orbit, clicking spare tiles into place to save your skin.
Isn't it true that each tile has an embedded, trilaterally-symmetric metal "Y" shaped skeleton to stiffen it? I swear I saw that sonewhere. Removing tiles might mean just whacking over the stud points with a hammer until enough of the ceramic is chipped away that you can directly get at the backside of the skeleton. Then the studs can be unclipped and the tile removed without having to be completely destroyed. You could even do this on-orbit, clicking spare tiles into place to save your skin.
I am surprised that there is no overlap between blankets. Might be something we will see in future.
May also see longer blanket in the future. Might be awkward working with longer blankets in the horizontal direction but perhaps vertically starting from the top could be fairly easy.
Set up a scaffold while one worker is pushing the blanket over the studs a worker on the level above could be installing the tiles.
I've installed more than the average vacation homeowner's share of siding. Process Looks pretty similar. I find it amusing that that SpaceX has figured out a system that hundreds of thousands in the light construction trade could install.
Having the fastener hidden and quick to install is brilliant, as with houses, the fastener is the weak point of any protective covering, especially if you have a house in an area that gets 50 inches of rain per year like I do. (hint: The rot nearly always starts at a fastener penetration). Gluing on siding or window trim is not something I would care to try. I don't even like waiting for caulk to set (if you do things right you don't need caulk, but that's too far off topic)
The blanket is analagous to building paper/tar paper or polypropylene rain screen. Taller doesn't get it installed much faster, it just increases the awkward time and error rate.
I am surprised that there is no overlap between blankets.Either an overlap, half-thickness pads with a full lap, or go along the seams with a block of felting needles to incorporate the two pieces.
I am surprised that there is no overlap between blankets.Either an overlap, half-thickness pads with a full lap, or go along the seams with a block of felting needles to incorporate the two pieces.
It'll be interesting to see the order of operations:
- Apply TPS to a barrel section, then stack barrels. Near-ground-level work for TPS application, but risks damage to TPS from handling and welding process, and still requires some elevated work to apply the TPS over joins.
- Stack barrels (with studs in place) then apply TPS. Lower risk of damage (just bent studs) and TPS application can be continuous, but requires lots of working at high elevations - even without any safety issues, hauling tiles up batch by batch on cherrypickers is going to slow things down a lot, as is trying to handle moderately fragile tiles and floppy rockwool-like sheets while literally flapping in the breeze.
Didn't we see support rails for a vertical access platform in the high bay?I am surprised that there is no overlap between blankets.Either an overlap, half-thickness pads with a full lap, or go along the seams with a block of felting needles to incorporate the two pieces.
It'll be interesting to see the order of operations:
- Apply TPS to a barrel section, then stack barrels. Near-ground-level work for TPS application, but risks damage to TPS from handling and welding process, and still requires some elevated work to apply the TPS over joins.
- Stack barrels (with studs in place) then apply TPS. Lower risk of damage (just bent studs) and TPS application can be continuous, but requires lots of working at high elevations - even without any safety issues, hauling tiles up batch by batch on cherrypickers is going to slow things down a lot, as is trying to handle moderately fragile tiles and floppy rockwool-like sheets while literally flapping in the breeze.
The smartest most skilled robot is still a human working robotically...Sounds like you haven't met some of the humans I have :-)
The smartest most skilled robot is still a human working robotically...
Incomparable at this point for the level of technology and low production number...The smartest most skilled robot is still a human working robotically...
Unfortunately, that's probably also the most error prone.
....
I always thought that application of tiles on rings and then stack was not going to be precise enough for the 1mm(?) gap between tiles after the stacks are connected. So tiling the whole vehicle after assembly was going to the only way.
.....
....
I always thought that application of tiles on rings and then stack was not going to be precise enough for the 1mm(?) gap between tiles after the stacks are connected. So tiling the whole vehicle after assembly was going to the only way.
.....
Was my impression too, actually wrote several post arguing along the same lines. But based on what we see now the section (3-4 rings) based method is their way.
- stacking and barrel section buildup done that way, and production of rocket body seems kind a matured process
- they have a stud welder robot cell/station for such sections
- i think we seen pinned sections mated/stacked later on (not with tiles however)
So I guess they can stack with adequate precision, in which case tiles can be installed before stackink. Actually the tiles itself can be used as a stacking guide to provide alignment (or not, if too fraigle. But special ones made of metal to be used through the stacking and replaced later are still a possibility)
The smartest most skilled robot is still a human working robotically...
....
I always thought that application of tiles on rings and then stack was not going to be precise enough for the 1mm(?) gap between tiles after the stacks are connected. So tiling the whole vehicle after assembly was going to the only way.
.....
Was my impression too, actually wrote several post arguing along the same lines. But based on what we see now the section (3-4 rings) based method is their way.
- stacking and barrel section buildup done that way, and production of rocket body seems kind a matured process
- they have a stud welder robot cell/station for such sections
- i think we seen pinned sections mated/stacked later on (not with tiles however)
So I guess they can stack with adequate precision, in which case tiles can be installed before stackink. Actually the tiles itself can be used as a stacking guide to provide alignment (or not, if too fraigle. But special ones made of metal to be used through the stacking and replaced later are still a possibility)
....
So missed the temporary metal tile placeholder on first reading...
So maybe one row of temp metal tiles on each section that are to be mated.
So something like this maybe:
Do the mate and alignment.
Remove temp metal tiles to weld.
Put on final tiles.
What are the chances that one of those guys installing was an engineer? Maybe the one who will program the robot.I am surprised that there is no overlap between blankets. Might be something we will see in future.
May also see longer blanket in the future. Might be awkward working with longer blankets in the horizontal direction but perhaps vertically starting from the top could be fairly easy.
Set up a scaffold while one worker is pushing the blanket over the studs a worker on the level above could be installing the tiles.
I've installed more than the average vacation homeowner's share of siding. Process Looks pretty similar. I find it amusing that that SpaceX has figured out a system that hundreds of thousands in the light construction trade could install.
Having the fastener hidden and quick to install is brilliant, as with houses, the fastener is the weak point of any protective covering, especially if you have a house in an area that gets 50 inches of rain per year like I do. (hint: The rot nearly always starts at a fastener penetration). Gluing on siding or window trim is not something I would care to try. I don't even like waiting for caulk to set (if you do things right you don't need caulk, but that's too far off topic)
The blanket is analagous to building paper/tar paper or polypropylene rain screen. Taller doesn't get it installed much faster, it just increases the awkward time and error rate.
The barrels look better with each ship and over time the top/bottom variance on the rings has shrunk to near insignificance. (Haven't seen any of those labels in a while) I think they're confident enough in their assembly that the barrel join will be a non issue, or they expect it to be by the time the tiles actually have to do their job.....
I always thought that application of tiles on rings and then stack was not going to be precise enough for the 1mm(?) gap between tiles after the stacks are connected. So tiling the whole vehicle after assembly was going to the only way.
.....
Was my impression too, actually wrote several post arguing along the same lines. But based on what we see now the section (3-4 rings) based method is their way.
- stacking and barrel section buildup done that way, and production of rocket body seems kind a matured process
- they have a stud welder robot cell/station for such sections
- i think we seen pinned sections mated/stacked later on (not with tiles however)
So I guess they can stack with adequate precision, in which case tiles can be installed before stackink. Actually the tiles itself can be used as a stacking guide to provide alignment (or not, if too fraigle. But special ones made of metal to be used through the stacking and replaced later are still a possibility)
They still need to do the weld between barrel sections. So I would guess one row of custom fit tiles. You got to cover the weld! Not too bad. It also allows tiling to occur on many barrels at the same time.
Yes, but not at "this point in time"... Let's see if the current theoretical iteration makes it through the "proof of concept" EDL multiple times successfully before any thoughts of robotic installation...The smartest most skilled robot is still a human working robotically...
Until they get tired or take a lunch break.
Robotic application has to be near the top of Elon's want list. Even the unusual one off tiles near the flaps, nose and at terminal edges.
The hexagon tiles that are all identical are not nearly as big of a concern as those special ones. Those are the ones I really want to see.
Yes, but not at "this point in time"... Let's see if the current theoretical iteration makes it through the "proof of concept" EDL multiple times successfully before any thoughts of robotic installation...The smartest most skilled robot is still a human working robotically...
Until they get tired or take a lunch break.
Robotic application has to be near the top of Elon's want list. Even the unusual one off tiles near the flaps, nose and at terminal edges.
The hexagon tiles that are all identical are not nearly as big of a concern as those special ones. Those are the ones I really want to see.
Edit ti add:
Yes once again that is based on that this will be a successful design as is... TBD...Yes, but not at "this point in time"... Let's see if the current theoretical iteration makes it through the "proof of concept" EDL multiple times successfully before any thoughts of robotic installation...The smartest most skilled robot is still a human working robotically...
Until they get tired or take a lunch break.
Robotic application has to be near the top of Elon's want list. Even the unusual one off tiles near the flaps, nose and at terminal edges.
The hexagon tiles that are all identical are not nearly as big of a concern as those special ones. Those are the ones I really want to see.
Edit ti add:
AIUI, the pins are already welded on robotically, so its already partially automated. Not a big stretch from there to applying the tiles in the same way.
Yes, IIRC Tesla actually overdid the automation at one point hand reverted some of the tasks to people. Automation needs to go in at the right point. Not to early and not too late.Yes, but not at "this point in time"... Let's see if the current theoretical iteration makes it through the "proof of concept" EDL multiple times successfully before any thoughts of robotic installation...The smartest most skilled robot is still a human working robotically...
Until they get tired or take a lunch break.
Robotic application has to be near the top of Elon's want list. Even the unusual one off tiles near the flaps, nose and at terminal edges.
The hexagon tiles that are all identical are not nearly as big of a concern as those special ones. Those are the ones I really want to see.
Edit ti add:
Yes, IIRC Tesla actually overdid the automation at one point hand reverted some of the tasks to people. Automation needs to go in at the right point. Not to early and not too late.
Absolutely, though with robots continually getting more sophisticated and works continually getting more expensive....Yes, IIRC Tesla actually overdid the automation at one point hand reverted some of the tasks to people. Automation needs to go in at the right point. Not to early and not too late.
"Render unto [ROBOTS] those things which are [ROBOTS]'s, render unto [WORKERS] those things which are [WORKERS]'s"
Yes, IIRC Tesla actually overdid the automation at one point hand reverted some of the tasks to people. Automation needs to go in at the right point. Not to early and not too late.
Yes, IIRC Tesla actually overdid the automation at one point hand reverted some of the tasks to people. Automation needs to go in at the right point. Not to early and not too late.
And one of the things that was over automated was:
Placement of insulating mat over the battery pack.
It turned out that robots like rigid thins but have problems with floppy things.
Another example was cable routing.
So at tesla they developed some kind of semi rigid cable system so robots could deal with it. Not sure if they have put it into production yet.
Yes, IIRC Tesla actually overdid the automation at one point hand reverted some of the tasks to people. Automation needs to go in at the right point. Not to early and not too late.
And one of the things that was over automated was:
Placement of insulating mat over the battery pack.
It turned out that robots like rigid thins but have problems with floppy things.
Another example was cable routing.
So at tesla they developed some kind of semi rigid cable system so robots could deal with it. Not sure if they have put it into production yet.
Hi everyone,
I have a question regarding the heat shield. How will windward thrusters integrate into the tile mesh? Will they cut holes on some of the tiles where they can poke out a thruster? I assume those thrusters would be made out of some very temp tolerant material.
Hi everyone,And welcome to the forum.
I have a question regarding the heat shield. How will windward thrusters integrate into the tile mesh? Will they cut holes on some of the tiles where they can poke out a thruster? I assume those thrusters would be made out of some very temp tolerant material.
They still need to do the weld between barrel sections. So I would guess one row of custom fit tiles. You got to cover the weld! Not too bad. It also allows tiling to occur on many barrels at the same time.
Tiles on the flap(s), is this discussed here? I didn't find it. Two sizes and same pattern as in SN10 body.
Tiles on the flap(s), is this discussed here? I didn't find it. Two sizes and same pattern as in SN10 body.
And they are on the wrong side (leeward nor windward). Was similar arrangement on SN10. Guess they want to test the tiles, but dont want to mess with aerodinamics of the flaps (yet).
Tiles on the flap(s), is this discussed here? I didn't find it. Two sizes and same pattern as in SN10 body.
And they are on the wrong side (leeward nor windward). Was similar arrangement on SN10. Guess they want to test the tiles, but dont want to mess with aerodinamics of the flaps (yet).
...
It might not be feasible to test the tiles on the windward side without making a full heatshield for at least the fin. The problem is that without the proper pieces on the edges, the tiles are not very aerodynamic, and so subjecting them to the airflow could easily rip them all off like shingles in a tornado.
.....
That seems troubling, as I'd think the static fire would be less stress than actually flying. (Or am I wrong about that?)
The heat shield is my big concern for Starship meeting its goals (with Raptor reliability/maintenance being second). It will need to do vastly better than Shuttle level of maintenance "finicky-ness", and much better than the demonstrated safety/reliability (1 reentry-related fatal accident out of 135 flights) as well, to meet its goals.
Do we know why the transpiration cooling was abandoned?
That seems troubling, as I'd think the static fire would be less stress than actually flying. (Or am I wrong about that?)Remember that this is a prototype used for a variety of testing. The large central bank of tiles all appear to be attached via the push fit two prong system and I suspect will be used for most of the tiling. But the smaller patches seem to have a different attachment mechanism, perhaps something they were testing to see if it worked better (it doesn't) or might be suitable for certain areas (it isn't). So probably useful info for them.
The heat shield is my big concern for Starship meeting its goals (with Raptor reliability/maintenance being second). It will need to do vastly better than Shuttle level of maintenance "finicky-ness", and much better than the demonstrated safety/reliability (1 reentry-related fatal accident out of 135 flights) as well, to meet its goals.
Do we know why the transpiration cooling was abandoned?
Large chunks out of two tiles broke off during the static fire, the larger patch also had small chips in several tiles.
Photo credit: Nomadd
Do we know why the transpiration cooling was abandoned?
Both fractured tile(s) -batches are bond with red adhesive, and have felt pads. Interesting to see that Y-like structure inside the tile is not some space-time-spring-suspended-contraption but three metal fasteners from local hardware store...
Both fractured tile(s) -batches are bond with red adhesive, and have felt pads. Interesting to see that Y-like structure inside the tile is not some space-time-spring-suspended-contraption but three metal fasteners from local hardware store...The mounting Y is just buried in that crumbly white part with holes to the attachment points. The white stuff is giving way when they break. It's almost chalk like, but much lighter.
Both fractured tile(s) -batches are bond with red adhesive, and have felt pads. Interesting to see that Y-like structure inside the tile is not some space-time-spring-suspended-contraption but three metal fasteners from local hardware store...The mounting Y is just buried in that crumbly white part with holes to the attachment points. The white stuff is giving way when they break. It's almost chalk like, but much lighter.
I don't know if the smaller tiles, or the ones with the red stuff which don't seem to be failing, are made the same way. But they're obviously testing variations and not just sticking the same thing up every time. Even if they get a batch with no failures, they'll probably keep trying new materials, construction and mountings, so assuming they can't figure it out is unwarranted.
Finding new ways to break them is just more data.
I can see where static fires with the ship being held down by those six mounting points might flex the hull more than flying.
Both fractured tile(s) -batches are bond with red adhesive, and have felt pads. Interesting to see that Y-like structure inside the tile is not some space-time-spring-suspended-contraption but three metal fasteners from local hardware store...The mounting Y is just buried in that crumbly white part with holes to the attachment points. The white stuff is giving way when they break. It's almost chalk like, but much lighter.
I don't know if the smaller tiles, or the ones with the red stuff which don't seem to be failing, are made the same way. But they're obviously testing variations and not just sticking the same thing up every time. Even if they get a batch with no failures, they'll probably keep trying new materials, construction and mountings, so assuming they can't figure it out is unwarranted.
Finding new ways to break them is just more data.
I can see where static fires with the ship being held down by those six mounting points might flex the hull more than flying.
Lighter than chalk? That's amazingly fragile.
Both fractured tile(s) -batches are bond with red adhesive, and have felt pads. Interesting to see that Y-like structure inside the tile is not some space-time-spring-suspended-contraption but three metal fasteners from local hardware store...
It could be that the tile below that one has its upper-right corner torn off.
On launch the ship needs to be held down ~1 sec as the engines build thrust. Don't most rockets hold down until the engines reach equilibrium? That'd be ~3 sec, which is about the timing of a static fire.Both fractured tile(s) -batches are bond with red adhesive, and have felt pads. Interesting to see that Y-like structure inside the tile is not some space-time-spring-suspended-contraption but three metal fasteners from local hardware store...The mounting Y is just buried in that crumbly white part with holes to the attachment points. The white stuff is giving way when they break. It's almost chalk like, but much lighter.
I don't know if the smaller tiles, or the ones with the red stuff which don't seem to be failing, are made the same way. But they're obviously testing variations and not just sticking the same thing up every time. Even if they get a batch with no failures, they'll probably keep trying new materials, construction and mountings, so assuming they can't figure it out is unwarranted.
Finding new ways to break them is just more data.
I can see where static fires with the ship being held down by those six mounting points might flex the hull more than flying.
8kg per m^2, that's the TPS density? If so, the whole heat shield is only 5t or so, pretty light...That's only for the white stuff. The black glassy outer surface and the metal 'Y' hardware will bump this up. Guesstimates generally come in at 10t.
They still need to do the weld between barrel sections. So I would guess one row of custom fit tiles. You got to cover the weld! Not too bad. It also allows tiling to occur on many barrels at the same time.
Based on photos, there is a fibrous mat below the tiles which appears to be semi-continuous (not per-tile). May complicate matters as it is not simply attaching a tile to points on the SS skin.
They still need to do the weld between barrel sections. So I would guess one row of custom fit tiles. You got to cover the weld! Not too bad. It also allows tiling to occur on many barrels at the same time.
Based on photos, there is a fibrous mat below the tiles which appears to be semi-continuous (not per-tile). May complicate matters as it is not simply attaching a tile to points on the SS skin.
The mounting studs welded to the SS skin poke right through the fiber pad. There's a video in the Production Updates thread somewhere of the installation process. The workers just push the pads on over the studs.
They still need to do the weld between barrel sections. So I would guess one row of custom fit tiles. You got to cover the weld! Not too bad. It also allows tiling to occur on many barrels at the same time.
Based on photos, there is a fibrous mat below the tiles which appears to be semi-continuous (not per-tile). May complicate matters as it is not simply attaching a tile to points on the SS skin.
The mounting studs welded to the SS skin poke right through the fiber pad. There's a video in the Production Updates thread somewhere of the installation process. The workers just push the pads on over the studs.
The original question for this set of replies was.
1. pre tile barrels and then figure out how to join them barrels so that tiles line up with their 1-2mm gap.
2. Wait till whole ship is assembled and then tile the whole thing.
Leaning towards number 1. Should be interesting how they will line up tiles between barrels.
It's for the complete tile, hardware, black stuff and all. No idea about underlayment or blue stuff.8kg per m^2, that's the TPS density? If so, the whole heat shield is only 5t or so, pretty light...That's only for the white stuff. The black glassy outer surface and the metal 'Y' hardware will bump this up.
Part of the problem is cost so they probably want to try the cheapest solutions first and only start experimenting with more costly or complex set ups if they have to. I would expect to see a range of different options being tested out as time goes on.
Transpiration cooling is still in the waiting in the wings if needed, but it is inherently inefficient as it will use consumables and its probably also involves more complexity and cost. I predict that either we won't see it or if we do it will be a lot later on the high energy areas after they have tried a lot of other options.
Here's an interesting clip, SpaceX workers working on the damaged tile. Nice sense of scale of the tile and detail of the back while they're holding it. Photo is a screen grab from the video.Tiles are hollow?
Here's an interesting clip, SpaceX workers working on the damaged tile. Nice sense of scale of the tile and detail of the back while they're holding it. Photo is a screen grab from the video.Tiles are hollow?
Like A or B?
Like A or B?A. At least for one out of several types they've tried.
They still need to do the weld between barrel sections. So I would guess one row of custom fit tiles. You got to cover the weld! Not too bad. It also allows tiling to occur on many barrels at the same time.
Based on photos, there is a fibrous mat below the tiles which appears to be semi-continuous (not per-tile). May complicate matters as it is not simply attaching a tile to points on the SS skin.
The mounting studs welded to the SS skin poke right through the fiber pad. There's a video in the Production Updates thread somewhere of the installation process. The workers just push the pads on over the studs.
The original question for this set of replies was.
1. pre tile barrels and then figure out how to join them barrels so that tiles line up with their 1-2mm gap.
2. Wait till whole ship is assembled and then tile the whole thing.
Leaning towards number 1. Should be interesting how they will line up tiles between barrels.
They would have to at least leave a single band of slots on the top and bottom of the circumference of each ring before stacking. What with the shims they use to line up the sections and all. And I haven't paid too much attention to how those things are welded together, but you can't tell me that they don't need access to that seam from the outside.
No direct evidence but ISTM they've got the tolerances down fine enough that any gap variance between sections would be within reach of the rope caulking that's been discussed. No need for fiddly sizing. Worst case, a little banging on the prongs could give 1-2mm without screwing things up. Not meant as a long term solution.They still need to do the weld between barrel sections. So I would guess one row of custom fit tiles. You got to cover the weld! Not too bad. It also allows tiling to occur on many barrels at the same time.
Based on photos, there is a fibrous mat below the tiles which appears to be semi-continuous (not per-tile). May complicate matters as it is not simply attaching a tile to points on the SS skin.
The mounting studs welded to the SS skin poke right through the fiber pad. There's a video in the Production Updates thread somewhere of the installation process. The workers just push the pads on over the studs.
The original question for this set of replies was.
1. pre tile barrels and then figure out how to join them barrels so that tiles line up with their 1-2mm gap.
2. Wait till whole ship is assembled and then tile the whole thing.
Leaning towards number 1. Should be interesting how they will line up tiles between barrels.
They would have to at least leave a single band of slots on the top and bottom of the circumference of each ring before stacking. What with the shims they use to line up the sections and all. And I haven't paid too much attention to how those things are welded together, but you can't tell me that they don't need access to that seam from the outside.
3: Hybrid model. Tile all but the ends of each section, then hand-tile one or two rows around where the sections join after assembly. I think there's 6 section joins so that's not that many tiles, and when a section join occurs there's already scaffolding or other infrastructure to make working on the joint easy
Build small amounts of tiles in -2, -1, +1, +2 mm size increments to deal with the variance in the size of the gaps where the sections are joined.
SN15 have bigger patch of tiles than ever, but hard shadows don't help at all...
Since these test vehicles won't be hitting the atmosphere (yet) they could simply not be caring about levelling the tiles yet....
Since these test vehicles won't be hitting the atmosphere (yet) they could simply not be caring about levelling the tiles yet....
A bit crazy idea: what if this uneven surface somehow help in insulation (so intentional)?
At much smaller scale and speed small dents and hills on a surface can create local turbulence which in turn cushioning the surface from laminar flow. Or something similar.
Turbulence massively increases teat transport across the flow (i.e. from the bow shock to the skin), se for example Wayne Hale's excellent blog posts.Since these test vehicles won't be hitting the atmosphere (yet) they could simply not be caring about levelling the tiles yet....
A bit crazy idea: what if this uneven surface somehow help in insulation (so intentional)?
At much smaller scale and speed small dents and hills on a surface can create local turbulence which in turn cushioning the surface from laminar flow. Or something similar.
I don’t think the uneven surface is intentional but your idea makes sense: increasing the distance to the shockwave by having turbulent flow on the surface of the spacecraft increasing the boundary layer.
Turbulence massively increases teat transport across the flow (i.e. from the bow shock to the skin), se for example Wayne Hale's excellent blog posts.
https://blogs.nasa.gov/waynehalesblog/2009/01/22/post_1232662169255/
https://blogs.nasa.gov/waynehalesblog/2009/01/29/post_1233082616008/
2.4 Silica Purification Process
The Cidco facility also includes a silica purification process. Bales of silica fibers are treated to be used in the manufacture of light-weight “bricks” used on the exterior of spacecraft. These bricks are manufactured at a separate SpaceX facility. Bales of silica fiber are delivered to the Cidco facility for processing and purification before being used as raw material for brick production. Bales weigh approximately 25 kilograms and are stored in a covered storage pavilion. To begin processing, bales are loaded manually into an insulation blower which cuts the fibers into small pieces before blowing the silica into a series of heated tanks of nitric acid. SpaceX can process a single bale in 10-15 minutes. The series of nitric acid tanks are fed by a 68% nitric acid solution delivered to the Cidco facility by truck. The solution is diluted to 15% nitric acid solution in the first tank with hot water produced by a series of four (4) natural gas-fired hot water heaters. Each natural gas heater has a maximum heat input capacity of 0.199 MMBtu/hr. Hot water generated using the hot water heaters is also circulated in coils around tanks to maintain the tanks at a target temperature. The nitric acid concentration is diluted in each progressive tank. After passing through the final tank, the silica-acid solution is discharged with a concentration of 1.5% nitric acid solution into a rotary drum which separates the silica slurry from the solution. The silica slurry is shipped to another SpaceX facility located in Cape Canaveral and the acid solution is neutralized to a pH between 6 and 8 and sent to an evaporation tower. The evaporation tower has a maximum heat input capacity of 7.5 MMBtu/hr and combusts natural gas to heat and evaporate the wastewater generated in the silica preparation process.7 Emissions of PM resulting from dissolved solids in the wastewater are controlled by the tower’s packed bed mist eliminators.
It appears that there are at least two variations in TPS attachment on SN15. A portion seems to have the insulating felt blanket, but a portion does not.
John
It appears that there are at least two variations in TPS attachment on SN15. A portion seems to have the insulating felt blanket, but a portion does not.I think the whole thing has felt, but it is really hard to see in some areas. I circled where it can be seen poking out in the blown-up image that BocaChicaGal posted. I have included a cropped version of the original. The image source goes to BocaChicaGal.
John
Here it is without the tiles: (Some reason I remembered it having a product name in big blue letters on...)It appears that there are at least two variations in TPS attachment on SN15. A portion seems to have the insulating felt blanket, but a portion does not.I think the whole thing has felt, but it is really hard to see in some areas. I circled where it can be seen poking out in the blown-up image that BocaChicaGal posted. I have included a cropped version of the original. The image source goes to BocaChicaGal.
John
Little different angle.It appears that there are at least two variations in TPS attachment on SN15. A portion seems to have the insulating felt blanket, but a portion does not.I think the whole thing has felt, but it is really hard to see in some areas. I circled where it can be seen poking out in the blown-up image that BocaChicaGal posted. I have included a cropped version of the original. The image source goes to BocaChicaGal.
John
Little different angle.Maybe a test of "good enough (at least for now)"?
The tiles don't seem to sit very flush.
Little different angle.Bit of forced perspective with false colors from 70s, it not look so bad.
The tiles don't seem to sit very flush.
Maybe. It just irks me because now my brain has to wonder if it's pin placement, brackets in the tiles, fuzzy backing getting caught in the clip or hull irregularities. Like it wasn't busy enough trying to figure out why people watch curling.Little different angle.Maybe a test of "good enough (at least for now)"?
The tiles don't seem to sit very flush.
Maybe. It just irks me because now my brain has to wonder if it's pin placement, brackets in the tiles, fuzzy backing getting caught in the clip or hull irregularities. Like it wasn't busy enough trying to figure out why people watch curling.Little different angle.Maybe a test of "good enough (at least for now)"?
The tiles don't seem to sit very flush.
Here it is without the tiles: (Some reason I remembered it having a product name in big blue letters on...)It appears that there are at least two variations in TPS attachment on SN15. A portion seems to have the insulating felt blanket, but a portion does not.I think the whole thing has felt, but it is really hard to see in some areas. I circled where it can be seen poking out in the blown-up image that BocaChicaGal posted. I have included a cropped version of the original. The image source goes to BocaChicaGal.
John
Also video:
Here it is without the tiles: (Some reason I remembered it having a product name in big blue letters on...)It appears that there are at least two variations in TPS attachment on SN15. A portion seems to have the insulating felt blanket, but a portion does not.I think the whole thing has felt, but it is really hard to see in some areas. I circled where it can be seen poking out in the blown-up image that BocaChicaGal posted. I have included a cropped version of the original. The image source goes to BocaChicaGal.
John
Also video:
Hmm. Looking at the process, I'm betting it's the insulation layer they're putting on here that's causing all the unevenness in the tiles. It's going on a bit wrinkly and uneven, if you will.
Thankfully, this is pretty clearly just a result of the way they're applying it by hand. I don't believe it will be that hard to make a machine that can smoothly press pieces of insulation to the hull - I'm picturing some sort of thing vaguely like a big paint roller - but of course they're not going to make such a machine until they have the tile (and insulation) design close to finalized so that the machine's requirements are known.
Short term, I feel like if they punched the holes in the insulation for the pins before laying it on, it would go on a lot easier. There are many industries where cutting forms out of large sheets of various materials is needed, so a machine capable of doing this should be readily available.
Why do they cut that top & bottom row of tiles?Because when they do the real thing, some of them will need to be trimmed. They need to test those too since the mounting won't be the same.
What is the significance of tile placement on the prototypes? Big rectangular area near the middle (with a corner missing on SN15) and the small clusters near the top and bottom that are located differently on each ship. I assume they're testing the adhesion method. Are there differences in tank temperature or some other properties of the tank at those specific locations?
https://twitter.com/cnunezimages/status/1380337952111403011
Hexagons are Bestagons!
You need the straight edge tiles for stuff like the edge of the heat shield at the transition between the shielded half of Starship and the bare stainless half of Starship as well as the bottom edge of the skirt.
Carbon-carbon?You need the straight edge tiles for stuff like the edge of the heat shield at the transition between the shielded half of Starship and the bare stainless half of Starship as well as the bottom edge of the skirt.
Good point on the edge tiles.
The transition tiles for the flaps and the nose cone are of the utmost interest. I'm sure we'll see them soon.
Hexagons are Bestagons!But can you trust a man who can't tell ICBM apart from SLBM?
Going back to those 5 sided tiles. It was mentioned that the hexagonal shape was to prevent a straight lines for the plasma to get into. It seems as though the 5 sided version will leave a continuous line with whatever they 'mate' with, thereby leaving a path for the plasma to follow. How would that be addressed?
Starship with full tile set! Augmented reality, by editing my render onto a pic by @BocaChicaGal . Looks so surreal.
I'm still confounded by an apparent incongruity between what's being done in terms of the single layer hexagonal tiles and the notion that:
- losing a single tile would jeopardize the vehicle:
- worst case burn through the metal hull, a better case being damage to the frame, precluding any reuse (Buran, apparently losing 3 adjacent tiles under the wing with a _titanium structure)
- losing a tile would lead to zipping off more
- that many tiles with a large gap without filler may compound the problem
- there is no materials science magic for tiles if lost even when made of TUFROC
then again the space shuttle probably survived many tile damages and ? tile losses apart from STS-27 with an aluminium frame only.
Gut feeling is that a 2nd layer say of an ablative material wrapped over or better under the tiles may be a good idea
Here's an interesting clip, SpaceX workers working on the damaged tile. Nice sense of scale of the tile and detail of the back while they're holding it. Photo is a screen grab from the video.
https://www.youtube.com/watch?v=eny57M5sxHk
I wonder why he wasn't using a jig, or just another tile with cork glued to the raised parts to push that replacement tile on. Maybe they're required to fix the issue if they don't snap on easily instead of forcing them. They're pretty fragile. Or the original tile popped off because it was wedged in too tight, so the same size replacement was also a bad fit.Photogrammetry would be ideal for measuring 3D motion and deformation (tiles are too homogenous, so they'd need to pain or stick on a 'speckle' pattern to track).
I'm picturing a bunch of those strips they test crank bearing clearances with shoved between tiles to see how cryo testing and engine firing messes with the gaps. Or really good camera pointed at them.
I'm still confounded by an apparent incongruity between what's being done in terms of the single layer hexagonal tiles and the notion that:
- losing a single tile would jeopardize the vehicle:
- worst case burn through the metal hull, a better case being damage to the frame, precluding any reuse (Buran, apparently losing 3 adjacent tiles under the wing with a _titanium structure)
- losing a tile would lead to zipping off more
- that many tiles with a large gap without filler may compound the problem
- there is no materials science magic for tiles if lost even when made of TUFROC
then again the space shuttle probably survived many tile damages and ? tile losses apart from STS-27 with an aluminium frame only.
Gut feeling is that a 2nd layer say of an ablative material wrapped over or better under the tiles may be a good idea
- losing a single tile could jeopardize the vehicle, but maybe not, because you have a insulating blanket under the tile and a shear layer will form over the cavity formed by the missing tile. Only testing will tell.
- losing a tile could lead to zipping off more, but I'm sure they will analyze and test to make sure it doesn't.
- loss of many tiles with large gap without filler (are you referring to the insulating blanket?) will definitely compound the problem. They will do their darndest to make sure this does not happen.
John
Why not use a kind of "water cannon" inside the tanks which is guided by an infrared system? In case of a tile failure the camera would sense the temperature increase and spray fuel onto the affected surface.::)
Awe, give it a couple reentries and it'll all smooth out. And get back to working that broom.Maybe. It just irks me because now my brain has to wonder if it's pin placement, brackets in the tiles, fuzzy backing getting caught in the clip or hull irregularities. Like it wasn't busy enough trying to figure out why people watch curling.Little different angle.Maybe a test of "good enough (at least for now)"?
The tiles don't seem to sit very flush.
https://twitter.com/bojay_stellar/status/1380189540653105153 (https://twitter.com/bojay_stellar/status/1380189540653105153)That pic is worth passing along. Has a muscle car feel. Or steam punk. Or something. Credits as given.QuoteStarship with full tile set! Augmented reality, by editing my render onto a pic by @BocaChicaGal . Looks so surreal.
I'm still confounded by an apparent incongruity between what's being done in terms of the single layer hexagonal tiles and the notion that:Gotta walk before you run. This is not the finished product.
- losing a _single tile would jeopardize the vehicle:
- worst case burn through the metal hull, a better case being damage to the frame, precluding any reuse (Buran, apparently losing 3 adjacent tiles under the wing with a _titanium structure)
- losing a tile would lead to zipping off more
- that many tiles with a large gap without filler may compound the problem
- there is no materials science magic for tiles if lost even when made of TUFROC
then again the space shuttle probably survived many tile damages and ? tile losses apart from STS-27 with an aluminium frame only.
Gut feeling is that a 2nd layer say of an ablative material wrapped over or better under the tiles may be a good idea
IIUC, what you're saying is the unsupported tile corners need to be pre loaded? Makes sense.Here's an interesting clip, SpaceX workers working on the damaged tile. Nice sense of scale of the tile and detail of the back while they're holding it. Photo is a screen grab from the video.
https://www.youtube.com/watch?v=eny57M5sxHk (https://www.youtube.com/watch?v=eny57M5sxHk)
Thanks for that.
It seems the force distribution through the possible flextural and resonance modes is not stable and low enough in levels, throughout the entire envelope of possible motion and stressing.
The suggestion is to have a small raised area on the back of the tile, furthest out at the three open corners. something that fits the stressing potentials. This, once the optimum pressing upon the thermal pad is figured out.
This would cancel one possible resonance mode and also drain those tips of unwanted collecting energies. Possibly enough to keep the tile out of fracture range, and shifting in it's position. Basically one is playing two modes, one against the other (in and out) and having motion potential, and with respect to mounting torsion being damped.
Again, reiterating... right now, undesirable mechanical energies would gather at those open unsupported tips. And the slight redesign of the backing, adding protrusions of some minimal sort, would possibly alleviate some mounting and stressing problems.
It all depends on the fragility of the tile, design of the backing, and so on.....but the video seen, does hint strongly at a problem area re energetic damping, stressing, and drainage.
If that is not sufficient, then there are other KISS related possibilities.
Just an idea (lots of work with fairly finicky wideband vibration control and dealing with flextural modes, mounting systems, etc, in the past 30 years).
I wonder why he wasn't using a jig, or just another tile with cork glued to the raised parts to push that replacement tile on. Maybe they're required to fix the issue if they don't snap on easily instead of forcing them. They're pretty fragile. Or the original tile popped off because it was wedged in too tight, so the same size replacement was also a bad fit.That stuff is plastigauge. ISTM the gaps will be a lot larger. If big enough for rope caulking, maybe 3-4mm. Any chance you've been close enough to see?
I'm picturing a bunch of those strips they test crank bearing clearances with shoved between tiles to see how cryo testing and engine firing messes with the gaps. Or really good camera pointed at them.
The problem is that when the tank warms up the gas pressure inside will rise until the tank ruptures. It is conceivable that this sort of arrangement might save the ship under a few very specific circumstances, but any extended heating would destroy the ship fairly rapidly. Adding a fair amount of mass and complexity to every flight in order to save the ship from a small subset of situations that occur very infrequently is not SpaceX style. They would rather spend the mass in making the tile system more robust so the problem doesn't occur in the first place.I'm still confounded by an apparent incongruity between what's being done in terms of the single layer hexagonal tiles and the notion that:
- losing a single tile would jeopardize the vehicle:
- worst case burn through the metal hull, a better case being damage to the frame, precluding any reuse (Buran, apparently losing 3 adjacent tiles under the wing with a _titanium structure)
- losing a tile would lead to zipping off more
- that many tiles with a large gap without filler may compound the problem
- there is no materials science magic for tiles if lost even when made of TUFROC
then again the space shuttle probably survived many tile damages and ? tile losses apart from STS-27 with an aluminium frame only.
Gut feeling is that a 2nd layer say of an ablative material wrapped over or better under the tiles may be a good idea
- losing a single tile could jeopardize the vehicle, but maybe not, because you have a insulating blanket under the tile and a shear layer will form over the cavity formed by the missing tile. Only testing will tell.
- losing a tile could lead to zipping off more, but I'm sure they will analyze and test to make sure it doesn't.
- loss of many tiles with large gap without filler (are you referring to the insulating blanket?) will definitely compound the problem. They will do their darndest to make sure this does not happen.
John
Why not use a kind of "water cannon" inside the tanks which is guided by an infrared system? In case of a tile failure the camera would sense the temperature increase and spray fuel onto the affected surface.
I'm still confounded by an apparent incongruity between what's being done in terms of the single layer hexagonal tiles and the notion that:
- losing a single tile would jeopardize the vehicle:
- worst case burn through the metal hull, a better case being damage to the frame, precluding any reuse (Buran, apparently losing 3 adjacent tiles under the wing with a _titanium structure)
- losing a tile would lead to zipping off more
- that many tiles with a large gap without filler may compound the problem
- there is no materials science magic for tiles if lost even when made of TUFROC
then again the space shuttle probably survived many tile damages and ? tile losses apart from STS-27 with an aluminium frame only.
Gut feeling is that a 2nd layer say of an ablative material wrapped over or better under the tiles may be a good idea
- losing a single tile could jeopardize the vehicle, but maybe not, because you have a insulating blanket under the tile and a shear layer will form over the cavity formed by the missing tile. Only testing will tell.
- losing a tile could lead to zipping off more, but I'm sure they will analyze and test to make sure it doesn't.
- loss of many tiles with large gap without filler (are you referring to the insulating blanket?) will definitely compound the problem. They will do their darndest to make sure this does not happen.
John
Why not use a kind of "water cannon" inside the tanks which is guided by an infrared system? In case of a tile failure the camera would sense the temperature increase and spray fuel onto the affected surface.
IIUC, what you're saying is the unsupported tile corners need to be pre loaded? Makes sense.Here's an interesting clip, SpaceX workers working on the damaged tile. Nice sense of scale of the tile and detail of the back while they're holding it. Photo is a screen grab from the video.
https://www.youtube.com/watch?v=eny57M5sxHk (https://www.youtube.com/watch?v=eny57M5sxHk)
Thanks for that.
It seems the force distribution through the possible flextural and resonance modes is not stable and low enough in levels, throughout the entire envelope of possible motion and stressing.
The suggestion is to have a small raised area on the back of the tile, furthest out at the three open corners. something that fits the stressing potentials. This, once the optimum pressing upon the thermal pad is figured out.
This would cancel one possible resonance mode and also drain those tips of unwanted collecting energies. Possibly enough to keep the tile out of fracture range, and shifting in it's position. Basically one is playing two modes, one against the other (in and out) and having motion potential, and with respect to mounting torsion being damped.
Again, reiterating... right now, undesirable mechanical energies would gather at those open unsupported tips. And the slight redesign of the backing, adding protrusions of some minimal sort, would possibly alleviate some mounting and stressing problems.
It all depends on the fragility of the tile, design of the backing, and so on.....but the video seen, does hint strongly at a problem area re energetic damping, stressing, and drainage.
If that is not sufficient, then there are other KISS related possibilities.
Just an idea (lots of work with fairly finicky wideband vibration control and dealing with flextural modes, mounting systems, etc, in the past 30 years).
Beware of wear on the lip face. It might need a stainless insert. Which might rub through the batting and then the hull. Crap! No wonder they say space is hard.
A thought. We've taken the goal of an inexpensive heatshield, added rapid turnaround then collectively shuddered at all the tile problems the shuttle had. Maybe is just isn't possible to do a lifetime heatshield with current technology. We shouldn't let perfect be the enemy of good.
Would a periodic rebuild of the tile system be all that bad a thing? Testing will give us a number but might it be done every 5th reentry? Would it be a deal killer if it were every 3rd? The airframes are, as rockets go, not all that expensive. Needing even 20% extra doesn't cost too much. The engines swap out easy enough.
Ship goes into maintenance for its 5 flight service, the engines and heatshield get stripped off. Engines get any TLC needed and go onto a ship finishing up servicing. In the meantime the ship gets a good inspection and the heatshield gets a rebuild.
The problem is that when the tank warms up the gas pressure inside will rise until the tank ruptures. It is conceivable that this sort of arrangement might save the ship under a few very specific circumstances, but any extended heating would destroy the ship fairly rapidly. Adding a fair amount of mass and complexity to every flight in order to save the ship from a small subset of situations that occur very infrequently is not SpaceX style. They would rather spend the mass in making the tile system more robust so the problem doesn't occur in the first place.
Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.Straight drill or a cookie cutter?
It'd have to be a core drill if they don't want to mangle the attachment clips.Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.Straight drill or a cookie cutter?
Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.I'd guessed earlier that's what you'd do instead of breaking the whole tile off. Do you think one day those holes will get drilled out on-orbit during an EVA for emergency tile replscement?
It seems easy enough. A jig you could set up in your garage. I imagine procedures will evolve with the tiles. Like, what to do if one of the clips pops off or gets mangled.Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.I'd guessed earlier that's what you'd do instead of breaking the whole tile off. Do you think one day those holes will get drilled out on-orbit during an EVA for emergency tile replscement?
It seems easy enough. A jig you could set up in your garage. I imagine procedures will evolve with the tiles. Like, what to do if one of the clips pops off or gets mangled.Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.I'd guessed earlier that's what you'd do instead of breaking the whole tile off. Do you think one day those holes will get drilled out on-orbit during an EVA for emergency tile replscement?
I watched a long documentary on the development of an electric wrench for Hubble repair. I'm fairly sure SpaceX won't need to spend that much time and money on it.
That video made me wonder if the underlayment puffed out when the tile disappeared, causing the difficulty in putting the new one on.
Yeah, I have to imagine that the inserts for the clips have grooves for the clips to slide out of, so that when they're aligned properly as when a tile is installed, the clips snap in and are locked like normal, but if you rotate the insert (i.e. by removing the rest of the tile so that it can rotate freely), by about 60 or 90 degrees, then the, uh, springy part of the clips? will line up with the grooves and can just be slid off.It'd have to be a core drill if they don't want to mangle the attachment clips.Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.Straight drill or a cookie cutter?
It'd have to be a core drill if they don't want to mangle the attachment clips.Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.Straight drill or a cookie cutter?
It seems easy enough. A jig you could set up in your garage. I imagine procedures will evolve with the tiles. Like, what to do if one of the clips pops off or gets mangled.Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.I'd guessed earlier that's what you'd do instead of breaking the whole tile off. Do you think one day those holes will get drilled out on-orbit during an EVA for emergency tile replscement?
I watched a long documentary on the development of an electric wrench for Hubble repair. I'm fairly sure SpaceX won't need to spend that much time and money on it.
That video made me wonder if the underlayment puffed out when the tile disappeared, causing the difficulty in putting the new one on.
In the latest photo of the large section of tiles by bocachicagal and RGV Aerial, there are a column of tiles with very noticeable gaps. Looking at some of these tiles even closer reveals that some of the tiles are not same the exact same size and thus the gaps.
Do we know why they are not all the same size or does that not really matter for these early prototypes? Is it hard to make them all the exact same size?
Also how will they size the tiles to fit the tapering nose?
In the latest photo of the large section of tiles by bocachicagal and RGV Aerial, there are a column of tiles with very noticeable gaps. Looking at some of these tiles even closer reveals that some of the tiles are not same the exact same size and thus the gaps.
Do we know why they are not all the same size or does that not really matter for these early prototypes? Is it hard to make them all the exact same size?
Also how will they size the tiles to fit the tapering nose?
The tiles are likely so brittle and frangible that you don't need a drill to remove one, just a hand-pushed cookie cutter punch. The alignment jig is a good idea though, since bent mounting pins are a more labor intensive problem than replacing a tile.Only makes me wonder how an astronaut is going to be able to hold onto the belly of a SS when trying to remove or install a tile up there. You push into the tile, and start moving back... what arrests your motion? Not a whole lot out there to hang onto. Maybe some kind of MMU system is needed.
Only makes me wonder how an astronaut is going to be able to hold onto the belly of a SS when trying to remove or install a tile up there. You push into the tile, and start moving back... what arrests your motion? Not a whole lot out there to hang onto. Maybe some kind of MMU system is needed.
The tiles are likely so brittle and frangible that you don't need a drill to remove one, just a hand-pushed cookie cutter punch. The alignment jig is a good idea though, since bent mounting pins are a more labor intensive problem than replacing a tile.Only makes me wonder how an astronaut is going to be able to hold onto the belly of a SS when trying to remove or install a tile up there. You push into the tile, and start moving back... what arrests your motion? Not a whole lot out there to hang onto. Maybe some kind of MMU system is needed.
In the latest photo of the large section of tiles by bocachicagal and RGV Aerial, there are a column of tiles with very noticeable gaps. Looking at some of these tiles even closer reveals that some of the tiles are not same the exact same size and thus the gaps.All of the main body tiles should be the same (within certain tolerances and a few exceptions). But the nose cones will need numerous different shaped tiles unless they go for a different solution for the nose. But assuming they stay with the hex based tiles one solution is illustrated in the second post of this thread. It would require a different tile shape for each ring of tiles around the nose plus a nose cap.
Do we know why they are not all the same size or does that not really matter for these early prototypes? Is it hard to make them all the exact same size?
Also how will they size the tiles to fit the tapering nose?
Sintering silica-fibre billets then milling the billets to size (before RCG coating) was how the STS tiles were made. If I were SpaceX and I wanted to mass produce effectively the same tiles but at a vastly lower cost, I would try and avoid that milling step entirely: achieve dimensional accuracy by correctly sizing the wet mould to account for shrinkage, and control shrinkage through controlling initial moisture content, bakeout time, and bakeout temperature (and temperature over time). Variance in those parameters risks an oversize or undersize tile, but avoiding post machining means you can come out ahead even if you occasionally need to toss out a bad patch.In the latest photo of the large section of tiles by bocachicagal and RGV Aerial, there are a column of tiles with very noticeable gaps. Looking at some of these tiles even closer reveals that some of the tiles are not same the exact same size and thus the gaps.
Do we know why they are not all the same size or does that not really matter for these early prototypes? Is it hard to make them all the exact same size?
Also how will they size the tiles to fit the tapering nose?
As we know, for tile manufacturing first some billets casted, than tiles machined to final shape from those billets. The precision of a machining operation should be in the sub mm range. So I would say the tiles are exactly the same size (or at least the white core of them).
Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.
John
Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.
John
Not feasible. At least from mine experience with ceramic grinding processes. But u can be very creative with tungsten or similar inserts afterwards.
The tiles are likely so brittle and frangible that you don't need a drill to remove one, just a hand-pushed cookie cutter punch. The alignment jig is a good idea though, since bent mounting pins are a more labor intensive problem than replacing a tile.
Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.
John
Not feasible. At least from mine experience with ceramic grinding processes. But u can be very creative with tungsten or similar inserts afterwards.
I was thinking of inserting something like C/Sic attachment skeleton into mold before sintering silica insulation block. Can you explain what the the problems are? Thanks.
What kind of telemetry would SpaceX want for reentry? With the addition of a Starlink antenna that can get real time data out from behind the plasma bow shock, it would be very useful to have telemetry on the tiles.
Since temperature sensors with bluetooth or wifi are cheap, why not embed one in each tile, and run a series of antennas under the white cladding?
Any loss of communication means a tile loss. The temperature sensor can sense how hot the tile is getting (might be good to have a sensor on all 6 corners)
It will be very difficult to debug a burned up Starship without real time telemetry. What are some other ideas on how to get real time telemetry of the tile performance?
Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.
John
Not feasible. At least from mine experience with ceramic grinding processes. But u can be very creative with tungsten or similar inserts afterwards.
..... Interesting to see that Y-like structure inside the tile is not some space-age-spring-suspended-contraption but three metal fasteners from local hardware store...https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=50748.0;attach=2021315;sess=52467
I appears that they have marked several tiles that are touching or very close to their neighbours. Perhaps these need to be refitted?
what problem
Heh fascinating KISS problem to have. I had too much free time. SO i made mock-up how they could approach that problem. From conceptual level ofcThink your image is similar to what SpaceX is doing, only the pin is not directly into the tile base-edge material, but into an internal support structure (not at the edge). Per previous discussion-images show that.
I was recently able to see Endeavor at the California Science Center and got a really close look at the tile arrangement at the elevons. I was wondering if anyone knows how the heating regime of Starships flaps differ from the Shuttle. Is the heating completely different or are there any lessons learned from Shuttle (elevons) that are directly or indirectly applicable to Starship?
I was recently able to see Endeavor at the California Science Center and got a really close look at the tile arrangement at the elevons. I was wondering if anyone knows how the heating regime of Starships flaps differ from the Shuttle. Is the heating completely different or are there any lessons learned from Shuttle (elevons) that are directly or indirectly applicable to Starship?
Interesting question. Doesn't bluntness (in case of SS aft flaps higher AoA) actually helps in lowering the overall heat flux transfer due "bow shock wave"? Does anyone has more knowledge about it. Or at least educated guess.
Heh fascinating KISS problem to have. I had too much free time. SO i made mock-up how they could approach that problem. From conceptual level ofcThink your image is similar to what SpaceX is doing, only the pin is not directly into the tile base-edge material, but into an internal support structure (not at the edge). Per previous discussion-images show that.
In the latest photo of the large section of tiles by bocachicagal and RGV Aerial, there are a column of tiles with very noticeable gaps. Looking at some of these tiles even closer reveals that some of the tiles are not same the exact same size and thus the gaps.
Do we know why they are not all the same size or does that not really matter for these early prototypes? Is it hard to make them all the exact same size?
Working once doesn't mean they don't have to worry about it. Working 20 times doesn't mean they don't have to worry about it. They need to know exactly what's going on because they can't test every possible combination of variables.
Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.The STS tiles were sintered at 1260°C. Being a near identical tile, I would expect the Starship tile sintering to occur at a similar temperature. Titanium might be fine, but that's uncomfortably 'squishy' for Steel or Nickel alloys. The huge difference in CTE could be a big problem unless the tile cavity for the insert could be sized to allow the insert to slide within the cavity without cracking or falling out (at the expense of positioning accuracy). Inserting the internal frame afterwards seems like less hassle.
John
But the flaps on Starship does have one benefit compared to Shuttle... They will never extend beyond level. So this means that the underside can extend out extra and give extra protection to the joint. (see quick and dirty sketch)
Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.The STS tiles were sintered at 1260°C. Being a near identical tile, I would expect the Starship tile sintering to occur at a similar temperature. Titanium might be fine, but that's uncomfortably 'squishy' for Steel or Nickel alloys. The huge difference in CTE could be a big problem unless the tile cavity for the insert could be sized to allow the insert to slide within the cavity without cracking or falling out (at the expense of positioning accuracy). Inserting the internal frame afterwards seems like less hassle.
John
Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.The STS tiles were sintered at 1260°C. Being a near identical tile, I would expect the Starship tile sintering to occur at a similar temperature. Titanium might be fine, but that's uncomfortably 'squishy' for Steel or Nickel alloys. The huge difference in CTE could be a big problem unless the tile cavity for the insert could be sized to allow the insert to slide within the cavity without cracking or falling out (at the expense of positioning accuracy). Inserting the internal frame afterwards seems like less hassle.
John
Thanks for the sinter temperature. C/SiC can handle that.
John
Will it? Seems to me to be about the same. But leading edges probably will have lower peak heating as they won't be angled directly into the airstream as on shuttle.Interesting question. Doesn't bluntness (in case of SS aft flaps higher AoA) actually helps in lowering the overall heat flux transfer due "bow shock wave"? Does anyone has more knowledge about it. Or at least educated guess.
Starship will be "fluffier" than Shuttle, thus reducing peak heat flux; SS flaps contribute to that.
Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.The STS tiles were sintered at 1260°C. Being a near identical tile, I would expect the Starship tile sintering to occur at a similar temperature. Titanium might be fine, but that's uncomfortably 'squishy' for Steel or Nickel alloys. The huge difference in CTE could be a big problem unless the tile cavity for the insert could be sized to allow the insert to slide within the cavity without cracking or falling out (at the expense of positioning accuracy). Inserting the internal frame afterwards seems like less hassle.
John
Thanks for the sinter temperature. C/SiC can handle that.
John
...
A lot of tiles show a color discontinuity where a clip is expected. I'm wondering if one line of testing is tiles with a through hole with a step for the clips to grab and a relatively thin plug to cover the hole. This would facilitate repair by allowing a straight carbide or diamond drill like used for ceramic tiles, and leave an unambiguous mark where to drill. No measurement necessary. If it works out.It'd have to be a core drill if they don't want to mangle the attachment clips.Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.Straight drill or a cookie cutter?
This has been discussed. My favorite is acoustic. Standard method of testing a grinding wheel for hairline cracks is to support it in the middle and give it a tap. A cracked wheel sounds very different. Hmm. A robot drone with a clip on pickup and a BB gun?It seems easy enough. A jig you could set up in your garage. I imagine procedures will evolve with the tiles. Like, what to do if one of the clips pops off or gets mangled.Fun fact...When they remove a tile on purpose, they bore 1/2" holes over the three attachment points so they can release the clips.I'd guessed earlier that's what you'd do instead of breaking the whole tile off. Do you think one day those holes will get drilled out on-orbit during an EVA for emergency tile replscement?
I watched a long documentary on the development of an electric wrench for Hubble repair. I'm fairly sure SpaceX won't need to spend that much time and money on it.
That video made me wonder if the underlayment puffed out when the tile disappeared, causing the difficulty in putting the new one on.
I didn't realize they were making them easy to replace in space. That sure makes mars takeoffs less of a concern.
Does anyone know if the is small, maybe handheld existing tech to quickly scan the tiles for hairline cracks or fractures while in space? Be it xray, or infra red, or super high res photos.
I'm imagining them sending out a person, or small drone to do a spacewalk around the ship and inspect every tile before each landing. What fun, I would do that job for free. lol
Suction cups? :oOnly makes me wonder how an astronaut is going to be able to hold onto the belly of a SS when trying to remove or install a tile up there. You push into the tile, and start moving back... what arrests your motion? Not a whole lot out there to hang onto. Maybe some kind of MMU system is needed.
All of the starship-in-space problems are solved by having even more starships. So naturally in this case you have couple of orbiting starships as stations, which can pull up on the side when requested, so you can stand on it while doing the repairs.
Suction cups? :oOnly makes me wonder how an astronaut is going to be able to hold onto the belly of a SS when trying to remove or install a tile up there. You push into the tile, and start moving back... what arrests your motion? Not a whole lot out there to hang onto. Maybe some kind of MMU system is needed.All of the starship-in-space problems are solved by having even more starships. So naturally in this case you have couple of orbiting starships as stations, which can pull up on the side when requested, so you can stand on it while doing the repairs.
So far it seems impossible to avoid some unique shapes on the nose and around the fins. Bummer. For in flight repairs it's no big thing to have a supply of the widely used hex tiles, but what about the odd shapes?Sintering silica-fibre billets then milling the billets to size (before RCG coating) was how the STS tiles were made. If I were SpaceX and I wanted to mass produce effectively the same tiles but at a vastly lower cost, I would try and avoid that milling step entirely: achieve dimensional accuracy by correctly sizing the wet mould to account for shrinkage, and control shrinkage through controlling initial moisture content, bakeout time, and bakeout temperature (and temperature over time). Variance in those parameters risks an oversize or undersize tile, but avoiding post machining means you can come out ahead even if you occasionally need to toss out a bad patch.In the latest photo of the large section of tiles by bocachicagal and RGV Aerial, there are a column of tiles with very noticeable gaps. Looking at some of these tiles even closer reveals that some of the tiles are not same the exact same size and thus the gaps.
Do we know why they are not all the same size or does that not really matter for these early prototypes? Is it hard to make them all the exact same size?
Also how will they size the tiles to fit the tapering nose?
As we know, for tile manufacturing first some billets casted, than tiles machined to final shape from those billets. The precision of a machining operation should be in the sub mm range. So I would say the tiles are exactly the same size (or at least the white core of them).
We know from the Astronaut Blvd FDEP. report that "After drying, the billet is split in two pieces thereby creating the rudimentary tiles. The tiles are shaped to the desired form using a router". I expect the split is face-to-face, to allow the backside cavities to be formed as part of the mould and to allow a single cutting op to face two tiles (rather than one at a time). That router's days are numbered!
Elon tweeted something about rope filler between tiles. Besides blocking physical and thermal intrusion it would help damp out edge vibration. To allow this a minimum gap is needed. Allowing vibrating and buzzing tiles to touch seems to be inviting trouble. But yes, for now they need to play with it to find minimum and maximum allowable gap.I appears that they have marked several tiles that are touching or very close to their neighbours. Perhaps these need to be refitted?
It's good at this stage to have tiles a mixed distance away from each other. If they don't lose the tightly nested tiles, then they don't have to worry about that later. If they do, then they know to enforce a minimum separation tolerance.
How would differential expansion be dealt with, in any technique?Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.The STS tiles were sintered at 1260°C. Being a near identical tile, I would expect the Starship tile sintering to occur at a similar temperature. Titanium might be fine, but that's uncomfortably 'squishy' for Steel or Nickel alloys. The huge difference in CTE could be a big problem unless the tile cavity for the insert could be sized to allow the insert to slide within the cavity without cracking or falling out (at the expense of positioning accuracy). Inserting the internal frame afterwards seems like less hassle.
John
Haha kind of hard to get good suction with no external pressureSuction cups? :oOnly makes me wonder how an astronaut is going to be able to hold onto the belly of a SS when trying to remove or install a tile up there. You push into the tile, and start moving back... what arrests your motion? Not a whole lot out there to hang onto. Maybe some kind of MMU system is needed.
All of the starship-in-space problems are solved by having even more starships. So naturally in this case you have couple of orbiting starships as stations, which can pull up on the side when requested, so you can stand on it while doing the repairs.
Does anyone have information on the possibility of co-curing the mechanical attachment structure into the silica ceramic insulation block? I am assuming that is what they are doing, but have no evidence.The STS tiles were sintered at 1260°C. Being a near identical tile, I would expect the Starship tile sintering to occur at a similar temperature. Titanium might be fine, but that's uncomfortably 'squishy' for Steel or Nickel alloys. The huge difference in CTE could be a big problem unless the tile cavity for the insert could be sized to allow the insert to slide within the cavity without cracking or falling out (at the expense of positioning accuracy). Inserting the internal frame afterwards seems like less hassle.
John
Thanks for the sinter temperature. C/SiC can handle that.
John
I think, visuals don't really match that (see attached), but please correct me if I am wrong.
Also, we suspect that they experimenting with multiple types/methods: so your C/Sic solution can be the working one, where we cannot observe broken ones.
Photo credit for Nomadd, cropped by HVM, this post:...
Elon tweeted something about rope filler between tiles. Besides blocking physical and thermal intrusion it would help damp out edge vibration. To allow this a minimum gap is needed. Allowing vibrating and buzzing tiles to touch seems to be inviting trouble. But yes, for now they need to play with it to find minimum and maximum allowable gap.I appears that they have marked several tiles that are touching or very close to their neighbours. Perhaps these need to be refitted?
It's good at this stage to have tiles a mixed distance away from each other. If they don't lose the tightly nested tiles, then they don't have to worry about that later. If they do, then they know to enforce a minimum separation tolerance.
I can just picture the greenest intern hanging down the side of the SS with a mallet, rope and wooden drift, just like pounding oakum on a wooden ship. LOL ;D
....
I think, visuals don't really match that (see attached), but please correct me if I am wrong.
Also, we suspect that they experimenting with multiple types/methods: so your C/Sic solution can be the working one, where we cannot observe broken ones.
Photo credit for Nomadd, cropped by HVM, this post:...
I missed this picture. The last one I saw appeared to be round and ceramic. It is hard to tell, but that one looks metallic and could have been slid in from the corners. I would love to get more info on their production.
John
ehh, maybe a little physics recap so we don't end up in a fantasy world:That's not how insulative TPS works: the goal is not to delay soak-through (that just means your structure melts during descent and landing rather than entry) but to reject heat. Usually through re-radiation, but the time you reach tick enough atmosphere at a slow enough velocity for convection to be a factor your TPS will have mostly cooled off.
Thermal insulation only slows down heat transfer, you still need to take that heat somewhere from the other side, only slower if you have better insulation
Lots of repair concepts generated in the STS era. Replacement TPS has no requirement to resemble standard TPS: its only requirements are to adhere (not necessarily via original anchoring method) and work once. All other requirements (e.g. mass, reusability, unit cost) go out the window for an emergency patch.So far it seems impossible to avoid some unique shapes on the nose and around the fins. Bummer. For in flight repairs it's no big thing to have a supply of the widely used hex tiles, but what about the odd shapes?Sintering silica-fibre billets then milling the billets to size (before RCG coating) was how the STS tiles were made. If I were SpaceX and I wanted to mass produce effectively the same tiles but at a vastly lower cost, I would try and avoid that milling step entirely: achieve dimensional accuracy by correctly sizing the wet mould to account for shrinkage, and control shrinkage through controlling initial moisture content, bakeout time, and bakeout temperature (and temperature over time). Variance in those parameters risks an oversize or undersize tile, but avoiding post machining means you can come out ahead even if you occasionally need to toss out a bad patch.In the latest photo of the large section of tiles by bocachicagal and RGV Aerial, there are a column of tiles with very noticeable gaps. Looking at some of these tiles even closer reveals that some of the tiles are not same the exact same size and thus the gaps.
Do we know why they are not all the same size or does that not really matter for these early prototypes? Is it hard to make them all the exact same size?
Also how will they size the tiles to fit the tapering nose?
As we know, for tile manufacturing first some billets casted, than tiles machined to final shape from those billets. The precision of a machining operation should be in the sub mm range. So I would say the tiles are exactly the same size (or at least the white core of them).
We know from the Astronaut Blvd FDEP. report that "After drying, the billet is split in two pieces thereby creating the rudimentary tiles. The tiles are shaped to the desired form using a router". I expect the split is face-to-face, to allow the backside cavities to be formed as part of the mould and to allow a single cutting op to face two tiles (rather than one at a time). That router's days are numbered!
Just for a working number let's say there are 30 different shapes. It could be much higher or a bit lower. The only options I can come up with are an onboard supply, onboard fabrication capability or a temporary one time use substitution.
A problem with an onboard inventory is how many of each shape. Some positions will have a higher wear rate, so more of them. But how many? It will take many reentries to develop a reliable statistical model with expected variance. The loss of a ship because of heatshield failure is lamentable but for a crewed mission it is unacceptable. Maybe a reliable model will be in hand before crew flights.
Onboard fabrication has its own difficulties. Unless the fab facility is large, production will be slow. If production is modeled on earth based production, 0G introduces a variable that needs to be explored before it can be considered reliable. Additive manufacturing shares this problem.
A temporary one use fix has promise. What comes to mind is a spray on or caulked ablative. It's not sexy but it promises to be quick, simple and reliable. If loss of one tile does not threaten LOM, orbital launches could substitute ablative material for one tile. It would still need on orbit installation testing and a tryout with direct entry velocities.
I would have thought taking a supply of regular tiles and modifying them in orbit would be possible as an emergency measure. If my proposed tile solution was used (see picture at the very top of page 1 of this thread) all tiles would be hexagonal but the nose tiles would need a single cut at an angle dependant on their placement. Perhaps a small rotary cutter in a jig sealed in a tile sized box would work? Cut edges could be coated with some ablative paint. At the end of the day it just needs to get back down once.So far it seems impossible to avoid some unique shapes on the nose and around the fins. Bummer. For in flight repairs it's no big thing to have a supply of the widely used hex tiles, but what about the odd shapes?Sintering silica-fibre billets then milling the billets to size (before RCG coating) was how the STS tiles were made. If I were SpaceX and I wanted to mass produce effectively the same tiles but at a vastly lower cost, I would try and avoid that milling step entirely: achieve dimensional accuracy by correctly sizing the wet mould to account for shrinkage, and control shrinkage through controlling initial moisture content, bakeout time, and bakeout temperature (and temperature over time). Variance in those parameters risks an oversize or undersize tile, but avoiding post machining means you can come out ahead even if you occasionally need to toss out a bad patch.In the latest photo of the large section of tiles by bocachicagal and RGV Aerial, there are a column of tiles with very noticeable gaps. Looking at some of these tiles even closer reveals that some of the tiles are not same the exact same size and thus the gaps.
Do we know why they are not all the same size or does that not really matter for these early prototypes? Is it hard to make them all the exact same size?
Also how will they size the tiles to fit the tapering nose?
As we know, for tile manufacturing first some billets casted, than tiles machined to final shape from those billets. The precision of a machining operation should be in the sub mm range. So I would say the tiles are exactly the same size (or at least the white core of them).
We know from the Astronaut Blvd FDEP. report that "After drying, the billet is split in two pieces thereby creating the rudimentary tiles. The tiles are shaped to the desired form using a router". I expect the split is face-to-face, to allow the backside cavities to be formed as part of the mould and to allow a single cutting op to face two tiles (rather than one at a time). That router's days are numbered!
Just for a working number let's say there are 30 different shapes. It could be much higher or a bit lower. The only options I can come up with are an onboard supply, onboard fabrication capability or a temporary one time use substitution.
A problem with an onboard inventory is how many of each shape. Some positions will have a higher wear rate, so more of them. But how many? It will take many reentries to develop a reliable statistical model with expected variance. The loss of a ship because of heatshield failure is lamentable but for a crewed mission it is unacceptable. Maybe a reliable model will be in hand before crew flights.
Onboard fabrication has its own difficulties. Unless the fab facility is large, production will be slow. If production is modeled on earth based production, 0G introduces a variable that needs to be explored before it can be considered reliable. Additive manufacturing shares this problem.
A temporary one use fix has promise. What comes to mind is a spray on or caulked ablative. It's not sexy but it promises to be quick, simple and reliable. If loss of one tile does not threaten LOM, orbital launches could substitute ablative material for one tile. It would still need on orbit installation testing and a tryout with direct entry velocities.
Today we saw new tiles placed on sn15, now the patch is more sqare-ish.Maybe that's how the scheduling/manpower/road closure/tile availability/rocket god puzzle shook out.
Any idea of why to put tiles one after rollout? As we know this operation takes very little time.
Today we saw new tiles placed on sn15, now the patch is more sqare-ish.There's no need to delay rollout if all the tiles aren't available right away. Maybe because some cracked on on install or they didn't have enough for any other reason. Or, they did it on purpose or just decided to add some. They usually have more clips welded on than tiles installed.
Any idea of why to put tiles one after rollout? As we know this operation takes very little time.
Today we saw new tiles placed on sn15, now the patch is more sqare-ish.There's no need to delay rollout if all the tiles aren't available right away. Maybe because some cracked on on install or they didn't have enough for any other reason. Or, they did it on purpose or just decided to add some. They usually have more clips welded on than tiles installed.
Any idea of why to put tiles one after rollout? As we know this operation takes very little time.
Today we saw new tiles placed on sn15, now the patch is more sqare-ish.Maybe that's how the scheduling/manpower/road closure/tile availability/rocket god puzzle shook out.
Any idea of why to put tiles one after rollout? As we know this operation takes very little time.
I think I found the mythical heat tile graveyard near the SN11 landing site. All small pieces.
I was going to post a picture, but a terrible apparition arose and said "I am the demon ITAR. Put down the camera or suffer the consequences"
I think I found the mythical heat tile graveyard near the SN11 landing site. All small pieces. I thought of gathering enough to make a smoker, but I suppose it would turn out they outgassed cyanide when they got hot or something.
It looks like the tiles don't have a Y shaped metal bracket inside like I thought, but three individual brackets.
I was going to post a picture, but a terrible apparition arose and said "I am the demon ITAR. Put down the camera or suffer the consequences"
I think I found the mythical heat tile graveyard near the SN11 landing site. All small pieces. I thought of gathering enough to make a smoker, but I suppose it would turn out they outgassed cyanide when they got hot or something.Heat it above 103°C to flash off the Methyltrimethoxysilane waterproofing agent (fumes are flammable, and don't huff them), and you'll have an inert silica fibre brick with a borosilicate glass coating. A flat chunk would make for a nice trivet.
It looks like the tiles don't have a Y shaped metal bracket inside like I thought, but three individual brackets.
I was going to post a picture, but a terrible apparition arose and said "I am the demon ITAR. Put down the camera or suffer the consequences"
A fun fact of geometry:
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
Yes, there would be elongated holes and some mobility. Have we seen this, or ruled it out?A fun fact of geometry:
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
Good idea, but this require free movement of nuts along the length of the Y elements (legs?).
Something like elongated holes on the back of the tile, freely moving legs in their voids. The elongated holes should be observable.
Yes, there would be elongated holes and some mobility. Have we seen this, or ruled it out?A fun fact of geometry:
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
Good idea, but this require free movement of nuts along the length of the Y elements (legs?).
Something like elongated holes on the back of the tile, freely moving legs in their voids. The elongated holes should be observable.
It looks like there might be some elongation, but if so, it’s very slight.Yes, there would be elongated holes and some mobility. Have we seen this, or ruled it out?A fun fact of geometry:
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
Good idea, but this require free movement of nuts along the length of the Y elements (legs?).
Something like elongated holes on the back of the tile, freely moving legs in their voids. The elongated holes should be observable.
Not enough data I think. I have these images, cropped from a video (several page upthread), but not the best resolution. The hole seems round (not elongated).
A fun fact of geometry:While the tile position is fully constrained, it is not constant. In particular, orientation is not retained as pins move, which means tiles can attempt to self-intersect (read: crush each other into bits) for offset pin geometries. Anisotropic expansion could also result in lateral tile displacement (e.g. a surface constrained axially by stringers but free to expand radially would cause tiles to shift up or down depending on pin triangle orientation).
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
A fun fact of geometry:While the tile position is fully constrained, it is not constant. In particular, orientation is not retained as pins move, which means tiles can attempt to self-intersect (read: crush each other into bits) for offset pin geometries. Anisotropic expansion could also result in lateral tile displacement (e.g. a surface constrained axially by stringers but free to expand radially would cause tiles to shift up or down depending on pin triangle orientation).
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
That's the hole in the tile material. It's hard to drill an oblong hole, and machining or punching might not work that well. The hole in the bracket is about 5x3.Not enough data I think. I have these images, cropped from a video (several page upthread), but not the best resolution.Yes, there would be elongated holes and some mobility. Have we seen this, or ruled it out?A fun fact of geometry:Good idea, but this require free movement of nuts along the length of the Y elements (legs?).
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
Something like elongated holes on the back of the tile, freely moving legs in their voids. The elongated holes should be observable.
The hole seems round (not elongated).
Yes. My assumption, based on what we see, is that inter-tile spacing can be large enough to accommodate manufacturing tolerances, in-flight deformation, etc., while avoiding inter-tile collisions, but that the pin-tile contacts need to be tight (no rattling!) and are by nature potentially more sensitive to misalignments that would apply stress to tiles. What the Y-constraint kinematics say is that allowing Y-arm-aligned pin compliance (or pin/tile displacement) is enough to accommodate substantial tolerances, deformation, etc., while both retaining tight coupling and avoiding tile stress. Which is kind of cool as an engineering principle, and maybe as a SpaceX design feature.A fun fact of geometry:While the tile position is fully constrained, it is not constant. In particular, orientation is not retained as pins move, which means tiles can attempt to self-intersect (read: crush each other into bits) for offset pin geometries. Anisotropic expansion could also result in lateral tile displacement [...]
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
The hole in the bracket is about 5x3.Picture, or ITAR?
I'm starting to warm up to ITAR. You can use that as an excuse for anything.The hole in the bracket is about 5x3.Picture, or ITAR?
Mmmph. Barn doors, horses. (Still confusing, maybe obsolete.)I'm starting to warm up to ITAR. You can use that as an excuse for anything.The hole in the bracket is about 5x3.Picture, or ITAR?
"Where's that circular saw you borrowed six months ago?"
"Sorry, ITAR prevents me from talking about that."
Just for reminder, broken tile from SN8. We can see structure inside tile where tile-side weld stud lock sits:
That's much heavier than I thought it would be. Hefty stuff. I'd like to hear more about it. Does it fray/rip easily? How compressible is it? What does it smell like? :-)
Glass fiber I assume. So it's not quite sniffing friendly. :)
Yes, the Strain Isolation Pads (SIP) were made of Nomex-felt. The orbiter skin-to-SIP and SIP-TPS tile interfaces used an adhesive which I believe to be an RTV silicone, no mounting pins.Glass fiber I assume. So it's not quite sniffing friendly. :)
I believe the Shuttle used Nomex felt pads.
John
Yes, the Strain Isolation Pads (SIP) were made of Nomex-felt. The orbiter skin-to-SIP and SIP-TPS tile interfaces used an adhesive which I believe to be an RTV silicone, no mounting pins.Glass fiber I assume. So it's not quite sniffing friendly. :)
I believe the Shuttle used Nomex felt pads.
John
A fun fact of geometry:Oh my god! Kinematic coupling! I read a Hackaday article on the concept ages ago and was trying to remember the name of the it so I could find the article again and keep learning more. Thank you so much. Sorry if this comment is technically OT. Yes it makes tons of sense for those tiles.
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
A section with well over ten heat tiles hiding in the corner of Tent 3, and what looks like the underlayment.Ten? What are you talking about? I count at least fourteen.
A section with well over ten heat tiles hiding in the corner of Tent 3, and what looks like the underlayment.I don't think that second photo is the underlayment. There's a pair of flanges sticking out, so probably some variety of flippy-flappy-aerosurface.
https://twitter.com/MarcusHouse/status/1385776584645177344
Seems like sn17 will have a big heat shield. Could we see a complete one before sn20? IMO it is reasonable, because they will habe to know how a complete heat shield performs (since we saw broken tiles)
A section with well over ten heat tiles hiding in the corner of Tent 3, and what looks like the underlayment.I don't think that second photo is the underlayment. There's a pair of flanges sticking out, so probably some variety of flippy-flappy-aerosurface.
Team - General Heat Shield question regarding SN15:
Was there any obvious damage from the static fire?
(Thank you in advance!)
SN15 suffered a few broken tiles during the static fire test.
Team - General Heat Shield question regarding SN15:
Was there any obvious damage from the static fire?
(Thank you in advance!)
What are the chances it's as much the size of the patch as the location? Topmost small patch had no dings but it's a good ways from the energy source. The big main patch seemed to have no problems. Only the two lower small patches lost tiles.
Speculations from a slightly more than nodding familiarity with acoustics. Adding a tile should drop the local resonant frequency. The padding acts as a high frequency damper between the skin and the tile and soak up some of the acoustic energy. The pins are a fairly straight acoustic conduit but the padding should drop delivered amplitude a bit. The mass and stiffness of the tile should force a local drop in harmonic frequency at the risk of cracking the tile around the pin.
A large array of tiles might have a this problem around the edge but it should be more acoustically benign inward from the edge. Or, and here is where I am adrift, the large patch might establish a large low frequency resonance area that encompasses the edge and protects it from high frequency vibrations.
Keep in mind that there is no math behind what I'm speculating but overall, ISTM the more tiles, the more acoustically benign the environment. The nosecone, raceways and flaps will not be easy. Nor will the edge condition of the engine bay bottom or the abrupt change at the top and bottom dome weld lines.
What are the chances it's as much the size of the patch as the location? Topmost small patch had no dings but it's a good ways from the energy source. The big main patch seemed to have no problems. Only the two lower small patches lost tiles.It seems both tiles lost from both sections were on the lower row adjacent to smaller tiles directly below them. Not sur eif this is relevant?
Speculations from a slightly more than nodding familiarity with acoustics. Adding a tile should drop the local resonant frequency. The padding acts as a high frequency damper between the skin and the tile and soak up some of the acoustic energy. The pins are a fairly straight acoustic conduit but the padding should drop delivered amplitude a bit. The mass and stiffness of the tile should force a local drop in harmonic frequency at the risk of cracking the tile around the pin.
A large array of tiles might have a this problem around the edge but it should be more acoustically benign inward from the edge. Or, and here is where I am adrift, the large patch might establish a large low frequency resonance area that encompasses the edge and protects it from high frequency vibrations.
Keep in mind that there is no math behind what I'm speculating but overall, ISTM the more tiles, the more acoustically benign the environment. The nosecone, raceways and flaps will not be easy. Nor will the edge condition of the engine bay bottom or the abrupt change at the top and bottom dome weld lines.
Making some of the lower tiles more robust (reinforced? densified? cushioned?) wouldn’t be the end of the world in terms of vehicle mass or complexity (same shape, some delta in production, one more type).
Good thing Starship is not a SSTO and Super Heavy doesn't have tiles, so in the actual launch there shouldn't be this kind of kick of static fire so close to the ground.
But they sill need those static fires to test new Starships, so how about adding tiles to the lower parts only after they are done with static fires?
However, this may still be a problem on Mars. Imagine launching to Earth and losing tiles before you even leave the Martian atmosphere...
Those tiles look like they might have individual pieces of blanket. But then again it really looks more like their mounted on a pad of French cream filling, so what do I know.Making some of the lower tiles more robust (reinforced? densified? cushioned?) wouldn’t be the end of the world in terms of vehicle mass or complexity (same shape, some delta in production, one more type).
From the look of the tiles removed, I don't see the white blanket under the lower two section of tiles that experienced tile fractures. There is a blanket on the large section:
https://forum.nasaspaceflight.com/index.php?topic=53509.msg2229139#msg2229139 (https://forum.nasaspaceflight.com/index.php?topic=53509.msg2229139#msg2229139)
Not sure what that means, except maybe the blanket helps.
I can just imagine this conversation inside spacex.Obviously they need to mount the dishes on the car. Never know what you'll learn until you try. 8)
Heat shield engineer: Can't you make the skirt sturdier so it doesn't vibrate so much. I have a car with steel panels that doesn't vibrate.
Skirt engineer: Can't you make those ceramic pottery things stronger so they don't break. I have dishes at home I can drop on the floor and they don't break.(corelle)
Those tiles look like they might have individual pieces of blanket. But then again it really looks more like their mounted on a pad of French cream filling, so what do I know.Making some of the lower tiles more robust (reinforced? densified? cushioned?) wouldn’t be the end of the world in terms of vehicle mass or complexity (same shape, some delta in production, one more type).
From the look of the tiles removed, I don't see the white blanket under the lower two section of tiles that experienced tile fractures. There is a blanket on the large section:
https://forum.nasaspaceflight.com/index.php?topic=53509.msg2229139#msg2229139 (https://forum.nasaspaceflight.com/index.php?topic=53509.msg2229139#msg2229139)
Not sure what that means, except maybe the blanket helps.
If there is going to be a problem with the heat shield, best place for it would be on the skirt, right?
We haven't seen those yet. And they will both need to be specialized parts, so might use different technology and perhaps have a little more lea way on cost.If there is going to be a problem with the heat shield, best place for it would be on the skirt, right?
Possible, but IMO the worst places are the leading edges of the elonerons and the nose cone tip. Skirt could be a problem if tiles keep breaking.
No missing tiles? Perfect flight.
No missing tiles? Perfect flight.https://twitter.com/RGVaerialphotos/status/1390382784720605185
No missing tiles? Perfect flight.https://twitter.com/RGVaerialphotos/status/1390382784720605185 (https://twitter.com/RGVaerialphotos/status/1390382784720605185)
No missing tiles? Perfect flight.https://twitter.com/RGVaerialphotos/status/1390382784720605185 (https://twitter.com/RGVaerialphotos/status/1390382784720605185)
One is not bad at all! and at an edge!
The shiny side of the Starship who lived.Looks like only one damaged tile on the back of SN15's aft flap. Harder to tell with the tiles on the forward flap being in deep shadow but I would expect that damage would be visible if there was any.
No missing tiles? Perfect flight.https://twitter.com/RGVaerialphotos/status/1390382784720605185 (https://twitter.com/RGVaerialphotos/status/1390382784720605185)
One is not bad at all! and at an edge!
Behind that missing tile, I expected to see an insulation blanket.
Edit: Or perhaps the blanket is there and we are just seeing the mounting material that is part of the missing tile?
I can just imagine this conversation inside spacex.
Heat shield engineer: Can't you make the skirt sturdier so it doesn't vibrate so much. I have a car with steel panels that doesn't vibrate.
Skirt engineer: Can't you make those ceramic pottery things stronger so they don't break. I have dishes at home I can drop on the floor and they don't break.(corelle)
However, this may still be a problem on Mars. Imagine launching to Earth and losing tiles before you even leave the Martian atmosphere...Stick them back on in Earth orbit?
Behind that missing tile, I expected to see an insulation blanket.
Edit: Or perhaps the blanket is there and we are just seeing the mounting material that is part of the missing tile?
Yes the blanket is still there... Note that the blanket section extends beyond the entire tiled area.
I wonder if we'll see a high emissivity applied to the inside of the propellant tanks to increase radiative heat transfer from the windward tank side to the leeward side. It would be like how the Space Shuttle leading edges used cross-radiation within the U-shaped RRC panels. I suppose the trick would be finding a lox and hot oxygen compatible high emissivity coating that's also simple to apply to the large steel plates before they are welded into rings, or even better after stacking. That or you could just let a relatively high emissivity oxide film develop as the lox tank walls heat up during the first re-entry.
I definitely expect to see some high emissivity inner coating applied to the flaps.
Edit: noob image posting question: I made the attached image in Preview, saved as png. The forum preview is quite blurry, but clicking through it seems fine. Is there a better format/encoding to post in so that the image is small/compressed yet not blurry in the forum preview, so that casual readers don't have to click through to get the gist of the post?There's nothing you can do. The preview is always blurry.
I wonder if we'll see a high emissivity applied to the inside of the propellant tanks to increase radiative heat transfer from the windward tank side to the leeward side. It would be like how the Space Shuttle leading edges used cross-radiation within the U-shaped RRC panels. I suppose the trick would be finding a lox and hot oxygen compatible high emissivity coating that's also simple to apply to the large steel plates before they are welded into rings, or even better after stacking.A sodium dichromate wash applied to one side of the steel before coiling produces a robust black burnished surface and doesn't affect welding. The surface burnish doesn't flake and it's compatable with pure oxygen. It's actually even used to passify stainless steel to make it more corrosion and chemical resistant. I do not know if it has any problem with methane, but as far as I can tell it'd be OK.
I wonder if we'll see a high emissivity applied to the inside of the propellant tanks to increase radiative heat transfer from the windward tank side to the leeward side. It would be like how the Space Shuttle leading edges used cross-radiation within the U-shaped RRC panels. I suppose the trick would be finding a lox and hot oxygen compatible high emissivity coating that's also simple to apply to the large steel plates before they are welded into rings, or even better after stacking.A sodium dichromate wash applied to one side of the steel before coiling produces a robust black burnished surface and doesn't affect welding. The surface burnish doesn't flake and it's compatable with pure oxygen. It's actually even used to passify stainless steel to make it more corrosion and chemical resistant. I do not know if it has any problem with methane, but as far as I can tell it'd be OK.
Sodum dichromate is really nasty stuff to handle but it's also something that would be applied offsite by the stainless steel mill during production. It would likely need a custom treatment method to treat one side of the sheet but not the other (so it's not quite as simple as running the steel through a chemical bath like most passivization methods).
It is not at all practical to apply to the inside of the rings after manufacture; sodium dichromate is just too nasty to spray or wipe in place.
I wonder if we'll see a high emissivity applied to the inside of the propellant tanks to increase radiative heat transfer from the windward tank side to the leeward side. It would be like how the Space Shuttle leading edges used cross-radiation within the U-shaped RRC panels. I suppose the trick would be finding a lox and hot oxygen compatible high emissivity coating that's also simple to apply to the large steel plates before they are welded into rings, or even better after stacking.A sodium dichromate wash applied to one side of the steel before coiling produces a robust black burnished surface and doesn't affect welding. The surface burnish doesn't flake and it's compatable with pure oxygen. It's actually even used to passify stainless steel to make it more corrosion and chemical resistant. I do not know if it has any problem with methane, but as far as I can tell it'd be OK.
Sodum dichromate is really nasty stuff to handle but it's also something that would be applied offsite by the stainless steel mill during production. It would likely need a custom treatment method to treat one side of the sheet but not the other (so it's not quite as simple as running the steel through a chemical bath like most passivization methods).
It is not at all practical to apply to the inside of the rings after manufacture; sodium dichromate is just too nasty to spray or wipe in place.
All the bolded sounds like it would drive up the cost of materials, so I dont think SpaceX will pursue this approach until and unless they feel the reward will match the cost.
With the most recent photos from the SpaceX Flickr, we can conclude that the post-landing damage on the upper-of-the-lower tile sections (don't know how to refer to it, see attached image) happened sometime post-launch. There was damage in these sections following static fire, so we know that's a harsh environment for the tiles. Launch itself doesn't appear to have damaged the tiles, so it must be something in the ascent, belly-flop, flip, or landing phases that resulted in damage. My bet would be on landing.
However, I'd expect that if they were damaged upon landing, we'd be able to see some debris on/near the pad. I've looked at several of RGV's aerial shots directly after landing, and I can't find any solid evidence of that. Not exactly dispositive, but there's that. I don't know if there are sufficiently high resolution shots available of the landing burn to determine if the tiles were already damaged by the time SN15 got below the clouds again.
Edit: noob image posting question: I made the attached image in Preview, saved as png. The forum preview is quite blurry, but clicking through it seems fine. Is there a better format/encoding to post in so that the image is small/compressed yet not blurry in the forum preview, so that casual readers don't have to click through to get the gist of the post?
With the most recent photos from the SpaceX Flickr, we can conclude that the post-landing damage on the upper-of-the-lower tile sections (don't know how to refer to it, see attached image) happened sometime post-launch. There was damage in these sections following static fire, so we know that's a harsh environment for the tiles. Launch itself doesn't appear to have damaged the tiles, so it must be something in the ascent, belly-flop, flip, or landing phases that resulted in damage. My bet would be on landing.
However, I'd expect that if they were damaged upon landing, we'd be able to see some debris on/near the pad. I've looked at several of RGV's aerial shots directly after landing, and I can't find any solid evidence of that. Not exactly dispositive, but there's that. I don't know if there are sufficiently high resolution shots available of the landing burn to determine if the tiles were already damaged by the time SN15 got below the clouds again.
Edit: noob image posting question: I made the attached image in Preview, saved as png. The forum preview is quite blurry, but clicking through it seems fine. Is there a better format/encoding to post in so that the image is small/compressed yet not blurry in the forum preview, so that casual readers don't have to click through to get the gist of the post?
Has the RGV's flyover happened befrore crews approached sn15? In the other someone may have picked up the tiles.
But I would think the damage didn't happen at the landing, since it was pretty gentle and the force on the tile is only the deceleration due to its (small) weight. I'd rather think that the damage happened during raptos re-light, the most shockfull (does this word exist? It means full of shocks ) part of the flight, maybe after the launch. The the tile part fell from over 500 m and nearly polverized.
With the most recent photos from the SpaceX Flickr, we can conclude that the post-landing damage on the upper-of-the-lower tile sections (don't know how to refer to it, see attached image) happened sometime post-launch. There was damage in these sections following static fire, so we know that's a harsh environment for the tiles. Launch itself doesn't appear to have damaged the tiles, so it must be something in the ascent, belly-flop, flip, or landing phases that resulted in damage. My bet would be on landing.
However, I'd expect that if they were damaged upon landing, we'd be able to see some debris on/near the pad. I've looked at several of RGV's aerial shots directly after landing, and I can't find any solid evidence of that. Not exactly dispositive, but there's that. I don't know if there are sufficiently high resolution shots available of the landing burn to determine if the tiles were already damaged by the time SN15 got below the clouds again.
Edit: noob image posting question: I made the attached image in Preview, saved as png. The forum preview is quite blurry, but clicking through it seems fine. Is there a better format/encoding to post in so that the image is small/compressed yet not blurry in the forum preview, so that casual readers don't have to click through to get the gist of the post?
Has the RGV's flyover happened befrore crews approached sn15? In the other someone may have picked up the tiles.
But I would think the damage didn't happen at the landing, since it was pretty gentle and the force on the tile is only the deceleration due to its (small) weight. I'd rather think that the damage happened during raptos re-light, the most shockfull (does this word exist? It means full of shocks ) part of the flight, maybe after the launch. The the tile part fell from over 500 m and nearly polverized.
I couldn't see any tile debris from the spacex livestream shots right after landing either, so I agree that the damage-on-landing hypothesis is not supported. I suppose I'd guess the raptor relight would be my second guess, and the tile debris would have fallen quite far if that's the case. I wonder if Nomadd or BocaChicaGal have come across any tile debris in their various wanderings. I doubt they'd be utterly destroyed falling from that height, they should be fairly light with a lot of drag, so more like a block of foam than a pane of glass while falling.
I wonder if we'll see a high emissivity applied to the inside of the propellant tanks to increase radiative heat transfer from the windward tank side to the leeward side. It would be like how the Space Shuttle leading edges used cross-radiation within the U-shaped RRC panels. I suppose the trick would be finding a lox and hot oxygen compatible high emissivity coating that's also simple to apply to the large steel plates before they are welded into rings, or even better after stacking. That or you could just let a relatively high emissivity oxide film develop as the lox tank walls heat up during the first re-entry.
I definitely expect to see some high emissivity inner coating applied to the flaps.
I wonder if we'll see a high emissivity applied to the inside of the propellant tanks to increase radiative heat transfer from the windward tank side to the leeward side. It would be like how the Space Shuttle leading edges used cross-radiation within the U-shaped RRC panels. I suppose the trick would be finding a lox and hot oxygen compatible high emissivity coating that's also simple to apply to the large steel plates before they are welded into rings, or even better after stacking. That or you could just let a relatively high emissivity oxide film develop as the lox tank walls heat up during the first re-entry.
I definitely expect to see some high emissivity inner coating applied to the flaps.
You don't want heat transfer between the propellant and the rest of the vehicle. That stuff is cryogenic, and has to stay very cold at all times. If anything, you might consider adding insulation to further reduce heat transfer.
Any ideas what could be the next step to solve the cracking problem?
Better vibration isolation (maybe something in the brackets)?
Different materials for the actual tiles?
We know they were testing some metallic tiles before they switched to ceramics.
Given that the tiles on the orbital prototype will be in a different vibrational environment from those on the prototypes seen to date. I wouldn't be surprised to see them try exactly the same unmodified tiles across the entire windward surface on SN20 just to see if it works.Any ideas what could be the next step to solve the cracking problem?
Better vibration isolation (maybe something in the brackets)?
Different materials for the actual tiles?
We know they were testing some metallic tiles before they switched to ceramics.
I think that better brakets is the way to go. But I would be carefull speaking of the braking problem until we see a full TPS. Nearly all tile broken are in the edges.
I'm curious whether there is a way to get data while the Starship prototype is reentering? I know normally there is the plasma generated that makes communication hard, if not impossible, which could make it hard to tell if a failure on reentry is the heat shield, or control system, or what.They're gonna using the NASA plane chartered fr Vandenberg to collect the reentry data over the Pacific
Do we know if they can communicate with Cargo or Crew dragon during reentry now?
I'm curious whether there is a way to get data while the Starship prototype is reentering? I know normally there is the plasma generated that makes communication hard, if not impossible, which could make it hard to tell if a failure on reentry is the heat shield, or control system, or what.I thought that was the point of using a Starlink terminal for comms on Starship; it is on the "back" of the vehicle, pointing upwards through the gap in the plasma behind the vehicle.
Do we know if they can communicate with Cargo or Crew dragon during reentry now?
I'm curious whether there is a way to get data while the Starship prototype is reentering? I know normally there is the plasma generated that makes communication hard, if not impossible, which could make it hard to tell if a failure on reentry is the heat shield, or control system, or what.
Do we know if they can communicate with Cargo or Crew dragon during reentry now?
They can use NASA TDRS as an orbital relay to transmit through the plasma hole behind the vehicle.
Is this fact or surmise?I'm curious whether there is a way to get data while the Starship prototype is reentering? I know normally there is the plasma generated that makes communication hard, if not impossible, which could make it hard to tell if a failure on reentry is the heat shield, or control system, or what.They're gonna using the NASA plane chartered fr Vandenberg to collect the reentry data over the Pacific
Do we know if they can communicate with Cargo or Crew dragon during reentry now?
My guess is slight extrapolation from the 2020 ACO selections: (https://www.nasa.gov/directorates/spacetech/2020_NASA_Announcement_of_Collaboration_Opportunity_ACO_Selections)Is this fact or surmise?I'm curious whether there is a way to get data while the Starship prototype is reentering? I know normally there is the plasma generated that makes communication hard, if not impossible, which could make it hard to tell if a failure on reentry is the heat shield, or control system, or what.They're gonna using the NASA plane chartered fr Vandenberg to collect the reentry data over the Pacific
Do we know if they can communicate with Cargo or Crew dragon during reentry now?
Space Exploration Technologies Corp. (SpaceX) of Hawthorne, California
SpaceX will partner with Langley to capture imagery and thermal measurements of its Starship vehicle during orbital re-entry over the Pacific Ocean. With the data, the company plans to advance a reusable thermal protection system, which protects the vehicle from aerodynamic heating, for missions returning from low-Earth orbit, the Moon, and Mars.
It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.This is true if the tiles must abut each other with no gaps, but if small gaps are allowed between the tiles, that's the same as inserting arbitrary small polygons. This is a bit like a "Missing-Square Puzzle (https://en.wikipedia.org/wiki/Missing_square_puzzle)." The question is how large the gaps can be and still have a workable heat shield.
There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)
This is true if the tiles must abut each other with no gaps, but if small gaps are allowed between the tiles, that's the same as inserting arbitrary small polygons.I don’t see how this can work on a nosecone with substantial curvature.
I tried to understand this more mathematical discussion, but it was a bit too complicate for me, but it is actually very intersting.I think these issues have already been discussed several times on this thread. It is sometimes difficult to visualize what is being discussed, but I suggest my original (simplified) tile picture in post 1 of this thread is probably still a reasonable guess as to a likely configuration for the nose cone (I would be interested if anyone thinks it wouldn't work and why). If this pattern is chosen then the manufacturing of each latitude type of tile is just a matter of milling / cutting two opposite edges at an angle suitable for that latitude. If needed it would also be possible to reduce the length of the tiles as well but this would require more cuts.
My questions are:
1)does this need for many different tiles in the nosecone kill the principia of having everywere the same tiles onto SS, to simplify installation and eventual repairs (so not having to carry one exact copy of every tile, like if evry tille was different)?
2)How could having a lot of different tiles impact their manufacturing?
The scheme you show is geometrically sound, but the proportions don’t reflect the large ratio between a (reasonable) nose-cap circumference and the (actual) bottom-of-cone circumference. A large ratio would force the tiles near the top to be much slimmer than those near the bottom. Any of several schemes could remedy this, but would require breaking the alignment of hexagons at various latitude lines. The trapezoid scheme drops alignment completely at all latitudes.I tried to understand this more mathematical discussion, but it was a bit too complicate for me, but it is actually very intersting.I think these issues have already been discussed several times on this thread. It is sometimes difficult to visualize what is being discussed, but I suggest my original (simplified) tile picture in post 1 of this thread is probably still a reasonable guess as to a likely configuration for the nose cone (I would be interested if anyone thinks it wouldn't work and why). If this pattern is chosen then the manufacturing of each latitude type of tile is just a matter of milling / cutting two opposite edges at an angle suitable for that latitude. If needed it would also be possible to reduce the length of the tiles as well but this would require more cuts.
My questions are:
1)does this need for many different tiles in the nosecone kill the principia of having everywere the same tiles onto SS, to simplify installation and eventual repairs (so not having to carry one exact copy of every tile, like if evry tille was different)?
2)How could having a lot of different tiles impact their manufacturing?
Yes correct my scheme only shows a small fragment of the required circumference to save space. And also true that the tiles near the top would be a lot narrower all other things being equal. But this arrangement allows a uniform gap between tiles to be maintained under all circumstances.The scheme you show is geometrically sound, but the proportions don’t reflect the large ratio between a (reasonable) nose-cap circumference and the (actual) bottom-of-cone circumference. A large ratio would force the tiles near the top to be much slimmer than those near the bottom. Any of several schemes could remedy this, but would require breaking the alignment of hexagons at various latitude lines. The trapezoid scheme drops alignment completely at all latitudes.I tried to understand this more mathematical discussion, but it was a bit too complicate for me, but it is actually very intersting.I think these issues have already been discussed several times on this thread. It is sometimes difficult to visualize what is being discussed, but I suggest my original (simplified) tile picture in post 1 of this thread is probably still a reasonable guess as to a likely configuration for the nose cone (I would be interested if anyone thinks it wouldn't work and why). If this pattern is chosen then the manufacturing of each latitude type of tile is just a matter of milling / cutting two opposite edges at an angle suitable for that latitude. If needed it would also be possible to reduce the length of the tiles as well but this would require more cuts.
My questions are:
1)does this need for many different tiles in the nosecone kill the principia of having everywere the same tiles onto SS, to simplify installation and eventual repairs (so not having to carry one exact copy of every tile, like if evry tille was different)?
2)How could having a lot of different tiles impact their manufacturing?
In any of these schemes, the number of distinct tile shapes on the nosecone can be substantially less the number of rows, which is a far cry from the thousands upon thousands of unique tiles on Shuttle.
The ugly sketch below illustrates features of a trapezoid scheme showing 4 rows with 2 tile shapes. Actual fits could be better -- perfect if N(tile-shapes) = N(rows).
If we allow one shape per row (as in your hex-tile illustration), the trapezoidal scheme likewise allows uniform gaps.
Yes correct my scheme only shows a small fragment of the required circumference to save space. And also true that the tiles near the top would be a lot narrower all other things being equal. But this arrangement allows a uniform gap between tiles to be maintained under all circumstances.
Your pattern does allow some flexibility in how the tiles may be used but at the cost of variable tile gaps and the potential risk of vertical gap alignments between latitude rings.
Oh I'm not saying all the tiles have to be the same or even that they all have to be hexagons. I'm just saying that if there is at least some allowable amount of gap then you can reduce the number of unique tiles simply by tolerating some amount of gap. You appear to be saying much the same thing in a different way.This is true if the tiles must abut each other with no gaps, but if small gaps are allowed between the tiles, that's the same as inserting arbitrary small polygons.I don’t see how this can work on a nosecone with substantial curvature.
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Trapezoidal tiles can avoid this problem because they don’t have to align in all directions. . . . Tiling a cone does require a range of shapes with different convergence angles, but if we allow small gaps, each shape can be used in rows that cover a moderate range of latitudes.
Hexagons can’t do this because they must align side-to-side with neighbors in all directions: “lines of latitude” are jagged and force alignments that stretch from equator to pole -- in effect, lines of longitude.
Hexagons + pentagons + heptagons can do the job, covering curved surfaces with some trade-off of number of shapes vs. uniformity of gaps. If straight channels are out, then this kind of scheme might be attractive.
To avoid the problem of long channels, I wonder if someone can accomplish much the same thing your trapezoids do with a limited set of (say) hexagons and pentagons? Again, a key question is how much gap can be tolerated.
Hexagons + pentagons + heptagons can do the job, covering curved surfaces with some trade-off of number of shapes vs. uniformity of gaps. If straight channels are out, then this kind of scheme might be attractive.
To avoid the problem of long channels, I wonder if someone can accomplish much the same thing your trapezoids do with a limited set of (say) hexagons and pentagons? Again, a key question is how much gap can be tolerated.
The pentagons and heptagons go together as follows:
Oh I'm not saying all the tiles have to be the same or even that they all have to be hexagons. I'm just saying that if there is at least some allowable amount of gap then you can reduce the number of unique tiles simply by tolerating some amount of gap. You appear to be saying much the same thing in a different way.This is true if the tiles must abut each other with no gaps, but if small gaps are allowed between the tiles, that's the same as inserting arbitrary small polygons.I don’t see how this can work on a nosecone with substantial curvature.
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Trapezoidal tiles can avoid this problem because they don’t have to align in all directions. . . . Tiling a cone does require a range of shapes with different convergence angles, but if we allow small gaps, each shape can be used in rows that cover a moderate range of latitudes.
Hexagons can’t do this because they must align side-to-side with neighbors in all directions: “lines of latitude” are jagged and force alignments that stretch from equator to pole -- in effect, lines of longitude.
Your picture with the trapezoids is a nice illustration of one way to do it with, as you say, N unique shapes for the nose (hopefully N < 10 or so) plus (presumably) one shape (a square?) for the body and a unique tile for the nose.
To avoid the problem of long channels, I wonder if someone can accomplish much the same thing your trapezoids do with a limited set of (say) hexagons and pentagons? Again, a key question is how much gap can be tolerated.
It's actually mathematically impossible to tile a rounded cone with any sort of uniform warped hexagon. If you try it, you'll find that it works alright at the beginning, but as the surface continues curving, your hexagons will become more and more distorted until you're forced to add pentagons to the mix. This is a direct consequence of the Euler Identity.This is true if the tiles must abut each other with no gaps, but if small gaps are allowed between the tiles, that's the same as inserting arbitrary small polygons. This is a bit like a "Missing-Square Puzzle (https://en.wikipedia.org/wiki/Missing_square_puzzle)." The question is how large the gaps can be and still have a workable heat shield.
There's just no way to avoid requiring a large number of different tile shapes when trying to tile a surface with non-zero curvature. (A cylinder has, mathematically speaking, zero curvature, just to be clear on this. Not so for a rounded cone)
Hexagons + pentagons + heptagons can do the job, covering curved surfaces with some trade-off of number of shapes vs. uniformity of gaps. If straight channels are out, then this kind of scheme might be attractive.
To avoid the problem of long channels, I wonder if someone can accomplish much the same thing your trapezoids do with a limited set of (say) hexagons and pentagons? Again, a key question is how much gap can be tolerated.
The pentagons and heptagons go together as follows:
they can't be big because of different thermal expansion coefficient of steel and tile material.
they can't be big because of different thermal expansion coefficient of steel and tile material.
Their brittleness and low strength also limits their size.
John
[tiles] can't be big because of different thermal expansion coefficient of steel and tile material.
A fun fact of geometry:
Y-shaped grooves (uniquely) accommodate arbitrary mounting-pin displacements: For any pin displacement, there is a tile position that fits and is fully constrained. With this constraint system, expansion and bending of mounting surfaces neither stress nor loosen tiles.
https://en.wikipedia.org/wiki/Kinematic_coupling (https://en.wikipedia.org/wiki/Kinematic_coupling)
they can't be big because of different thermal expansion coefficient of steel and tile material.
Their brittleness and low strength also limits their size.
John
Note that that kinematic relationship only holds for planar expansion.Why?
I don't think it would work as drawn because the areas of hexagons to either side of centre line T won't tessellate on a curved surface. One way round that would be to have additional non hexagonal tiles at intervals around the circumference (possibly what you intended?) but regular pentagons and heptagons won't fit. Irregular pentagons and heptagons could fit, but as the curvature of the nose changes and becomes steeper the pentagons and heptagons will need to change in shape to accommodate the change in geometry.Hexagons + pentagons + heptagons can do the job, covering curved surfaces with some trade-off of number of shapes vs. uniformity of gaps. If straight channels are out, then this kind of scheme might be attractive.
To avoid the problem of long channels, I wonder if someone can accomplish much the same thing your trapezoids do with a limited set of (say) hexagons and pentagons? Again, a key question is how much gap can be tolerated.
The pentagons and heptagons go together as follows:
Yes, with the scheme above there is still a trade-off between reducing the number of tile shapes and reducing the variation in gap widths. Three shapes is probably not enough to provide a good fit, and as you suggest, the optimal pentagons and heptagons would in any case be asymmetric to fit their asymmetric contexts. To improve the fit, the next tiles to distort would probably be hexagons that touch both a pentagon and heptagon.I don't think it would work as drawn because the areas of hexagons to either side of centre line T won't tessellate on a curved surface. One way round that would be to have additional non hexagonal tiles at intervals around the circumference (possibly what you intended?) but regular pentagons and heptagons won't fit. Irregular pentagons and heptagons could fit, but as the curvature of the nose changes and becomes steeper the pentagons and heptagons will need to change in shape to accommodate the change in geometry.Hexagons + pentagons + heptagons can do the job, covering curved surfaces with some trade-off of number of shapes vs. uniformity of gaps. If straight channels are out, then this kind of scheme might be attractive.
To avoid the problem of long channels, I wonder if someone can accomplish much the same thing your trapezoids do with a limited set of (say) hexagons and pentagons? Again, a key question is how much gap can be tolerated.
The pentagons and heptagons go together as follows:
I must say I am intrigued by your diagram, but I can’t visualize it in its finished form. The trouble is that 3 dimensional tiling geometry is not easy (at least not for me).Yes, with the scheme above there is still a trade-off between reducing the number of tile shapes and reducing the variation in gap widths. Three shapes is probably not enough to provide a good fit, and as you suggest, the optimal pentagons and heptagons would in any case be asymmetric to fit their asymmetric contexts. To improve the fit, the next tiles to distort would probably be hexagons that touch both a pentagon and heptagon.I don't think it would work as drawn because the areas of hexagons to either side of centre line T won't tessellate on a curved surface. One way round that would be to have additional non hexagonal tiles at intervals around the circumference (possibly what you intended?) but regular pentagons and heptagons won't fit. Irregular pentagons and heptagons could fit, but as the curvature of the nose changes and becomes steeper the pentagons and heptagons will need to change in shape to accommodate the change in geometry.Hexagons + pentagons + heptagons can do the job, covering curved surfaces with some trade-off of number of shapes vs. uniformity of gaps. If straight channels are out, then this kind of scheme might be attractive.
To avoid the problem of long channels, I wonder if someone can accomplish much the same thing your trapezoids do with a limited set of (say) hexagons and pentagons? Again, a key question is how much gap can be tolerated.
The pentagons and heptagons go together as follows:
--------------------------
There is, however, a different heptagon/pentagon tweak that fits well with your initial all-hex diagram and allows uniform gaps -- no trade-off -- with about the same number of tile shapes. If aligned gaps (forming long, straight grooves) must be avoided, this hybrid scheme would be my current favorite. It is almost as tidy as a one-shape-per-row trapezoid scheme, but all the grooves zig-zag.The very ugly diagram below shows the geometric principle: Rows of hexagons continue from north to south, growing wider until a tile-width reset, which requires one row of heptagons and one row of alternating hexagons and pentagons before hexagons resume.
(The 5-6-7 width-reset bands would be high up the side where the circumference starts to shrink rapidly.)
I must say I am intrigued by your diagram, but I can’t visualize it in its finished form. The trouble is that 3 dimensional tiling geometry is not easy (at least not for me).Here’s an attempt at a description:
If you can describe it very clearly in words I will try to build a paper model. Note there should be gaps in between some of the tiles in a 2D projection as the circumference decreases towards the top of the nose so each “latitude” of tiles will need fewer tiles or smaller tiles.
they can't be big because of different thermal expansion coefficient of steel and tile material.
Their brittleness and low strength also limits their size.
John
Would it be possible to reinforce the tiles with some sort of embedded glass fibre mesh to reduce it's brittleness? IIRC glass fibre could withstand up to 1,200 C temperature, not sure if that's sufficient for reinforcing heat tiles.
The Shuttle tiles are like that, but I thought these tiles were much denser and thinner.they can't be big because of different thermal expansion coefficient of steel and tile material.
Their brittleness and low strength also limits their size.
John
Would it be possible to reinforce the tiles with some sort of embedded glass fibre mesh to reduce it's brittleness? IIRC glass fibre could withstand up to 1,200 C temperature, not sure if that's sufficient for reinforcing heat tiles.
They are made up of silica fibers (and small amounts of other elements) sparsely bonded together so that their volume is ~90% void. They are weak and light because they are mostly made up of nothing.
John
The Shuttle tiles are like that, but I thought these tiles were much denser and thinner.they can't be big because of different thermal expansion coefficient of steel and tile material.
Their brittleness and low strength also limits their size.
John
Would it be possible to reinforce the tiles with some sort of embedded glass fibre mesh to reduce it's brittleness? IIRC glass fibre could withstand up to 1,200 C temperature, not sure if that's sufficient for reinforcing heat tiles.
They are made up of silica fibers (and small amounts of other elements) sparsely bonded together so that their volume is ~90% void. They are weak and light because they are mostly made up of nothing.
John
Still brittle, but not styrofoam.
I think I can visualize what you are trying to do now but I suspect there will be many more tile sizes than you think. Won’t the hexagons in the lowest layer be slightly larger than those in the next layer up? And won’t the hexagons in that layer be slightly larger than those in the next layer above that (the hexagon / pentagon layer)?I must say I am intrigued by your diagram, but I can’t visualize it in its finished form. The trouble is that 3 dimensional tiling geometry is not easy (at least not for me).Here’s an attempt at a description:
If you can describe it very clearly in words I will try to build a paper model. Note there should be gaps in between some of the tiles in a 2D projection as the circumference decreases towards the top of the nose so each “latitude” of tiles will need fewer tiles or smaller tiles.
Imagine that all the polygons are neatened up to be identical along latitude-rows (which form circular arcs in the diagram). Extend the pattern to add more meridians (the radial lines in the diagram) and latitude rows (where there is a choice of 6, 7, and (5,6) rows). Imagine that the pattern is printed on a rubber sheet. Stretch the sheet around the nosecone, revising it to place the 7+(5,6) bands at latitudes where the hexagons would become too crowded toward the nose or to stretched toward the bottom. (Note that the hexagons toward the center of the diagram span twice as many lines of longitude as the hexagons further out.)
Does that make a useful mental image?
To make a non-stretchable paper model would of course require translating this geometry into polygon dimensions that fit the varying circumference and convergence-angles of longitude-lines as they run up the side.
I think I can visualize what you are trying to do now but I suspect there will be many more tile sizes than you think. Won’t the hexagons in the lowest layer be slightly larger than those in the next layer up? And won’t the hexagons in that layer be slightly larger than those in the next layer above that (the hexagon / pentagon layer)?Yes. The taper of the nosecone requires different tile widths at different heights. Almost the same number of tile-types would be required by this scheme and the all-hex scheme that you presented at the top of the thread: One type per row (aside from using two types in a few (5,6) rows).
Apologies if this has already been suggested and discounted - I've lost track in this and possibly other threads...Well yes I think it works from a tile tessellation perspective. Equilateral triangles on their own would also work on the main cylindrical body of starship, but they have decided to use hexagons instead. I wonder if triangles pose breakage problems with their acute angles?
What is the problem with simply using equilateral and slightly narrower isosceles triangles on the ogive? If the equilaterals are "A" or "V" and the narrower isosc triangles are v then at the bottom (near cylinder) you could us a tessellation like:
AVAVAVAVAVAvAVAVAVAVAVAVAVAVAVAVAVAvAVAVAVAVAVA (for example)
whereas next to the nose you might use:
AvAvAvAvAvAvAv (again, as an example).
You'd pick the width of the isosc triangle such that it perfectly fits alongside the circumference of the nose protector. You then use fewer isosc triangles as you progress down towards the cylinder part of the ogive as the angle of curvature loosens off.
Sorry for poor terminology but hopefully you get what I mean. You might be able to get the packing close enough such that there aren't circumferential gap lines??
edited for some missing "V"s in my first illustration!
Apologies if this has already been suggested and discounted - I've lost track in this and possibly other threads...
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Yes good point its not just straight lines down the vehicle, straight lines around the vehicle might also pose a problem.Apologies if this has already been suggested and discounted - I've lost track in this and possibly other threads...
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Musk is quoted as wanting to avoid straight paths where gas could accelerate:
https://www.digitaltrends.com/cool-tech/spacex-hexagon-heat-shield-tiles/
Edit: and I'm sure his team is mathematically inclined and there has been work work on the mathematics of tiling:
https://en.m.wikipedia.org/wiki/Penrose_tiling
Try that in your bathroom first :-)
What are your guys' thoughts regarding the way this section is tiled? It appears that a large straight gap was left between the tiles of the two barrel sections, rather than it being covered with standard hexagonal tiles.Interesting. It looks to me like the straight line is on a circumferential weld, and you can see one of the tie-down fittings for the recovery transporter (do we have a name for that thing yet? Megagrabber?), so I think this is the boundary between the leg skirt and the aft dome section. At the wide gap you can see a reinforcing band which I presume is the band reinforcement for the area where the aft dome joins the barrel section. It seems to me that they're all in of tiling these things section-by-section prior to joining, and now they're working out how to the bridge the gaps in the TPS once the section are joined together.
Image credit: Bocachicagal
What are your guys' thoughts regarding the way this section is tiled? It appears that a large straight gap was left between the tiles of the two barrel sections, rather than it being covered with standard hexagonal tiles.It could also be a SN17 thrust section, since the SN20 actual aft dome section is spotted
Image credit: Bocachicagal
What are your guys' thoughts regarding the way this section is tiled? It appears that a large straight gap was left between the tiles of the two barrel sections, rather than it being covered with standard hexagonal tiles.
Image credit: Bocachicagal
What are your guys' thoughts regarding the way this section is tiled? It appears that a large straight gap was left between the tiles of the two barrel sections, rather than it being covered with standard hexagonal tiles.
Image credit: Bocachicagal
One thing noticeable is the partial tiles abutting the gap are large enough to all have three studs.What are your guys' thoughts regarding the way this section is tiled? It appears that a large straight gap was left between the tiles of the two barrel sections, rather than it being covered with standard hexagonal tiles.Interesting. It looks to me like the straight line is on a circumferential weld, and you can see one of the tie-down fittings for the recovery transporter (do we have a name for that thing yet? Megagrabber?), so I think this is the boundary between the leg skirt and the aft dome section. At the wide gap you can see a reinforcing band which I presume is the band reinforcement for the area where the aft dome joins the barrel section. It seems to me that they're all in of tiling these things section-by-section prior to joining, and now they're working out how to the bridge the gaps in the TPS once the section are joined together.
Image credit: Bocachicagal
They do have the white thermal blanket covering the weld, so maybe they figure the gap between tiles is small enough to get away with? As long as it survives re-entry at all, perhaps that's good enough for now, this likely being a single use vehicle and all? Maybe they'll stuff ablative thermal goo into the gap? As for the bigger gap, presumably they'll weld on some studs and tile that area.
I guess what I'm saying is it you want answers, ask someone who has a clue ... right now, that's not me!
So why is there a circular area of damaged tiles in this picture by bocachicagal?That is a hole cut right through the metal skin. The black area is not tiles its inside the tank
Seems like a weird bit of damage. The blanket is intact.
So why is there a circular area of damaged tiles in this picture by bocachicagal?That is a hole cut right through the metal skin. The black area is not tiles its inside the tank
Seems like a weird bit of damage. The blanket is intact.
So why is there a circular area of damaged tiles in this picture by bocachicagal?That is a hole cut right through the metal skin. The black area is not tiles its inside the tank
Seems like a weird bit of damage. The blanket is intact.
your eyes, better than mine.
I have to think that's a test article then, that's one ugly shaped hole.
Yes its scrap. they must have wanted a particular skin section for test purposes. I think there was even a high contrast picture on one of the threads showing the inside although I can't find it now. As someone said on another thread - just cut a hole in it... how big and what shape hole? Yes and do it quickly.So why is there a circular area of damaged tiles in this picture by bocachicagal?That is a hole cut right through the metal skin. The black area is not tiles its inside the tank
Seems like a weird bit of damage. The blanket is intact.
your eyes, better than mine.
I have to think that's a test article then, that's one ugly shaped hole.
Nosecone barrel section moved in front of the windbreak.A layer of some sort of mesh scrim is being added to a section of SN16, between the tiles and the mineral wool underlay.
Working on the TPS.
Hello
How complex is it to manufacture such heat tiles???
I mean, how many different materials are needed?
How many production steps and how long do they take?
Highly automatable or not?
Do they need intensive testing after production or is the production reliable (high yield)?
...
Thanks
Have we seen tiles for anything but flap and tank surfaces yet?We've seen the complete set- Hexes, half hexes, and two different sizes of smaller hexes. With the smaller hexes, they can tile the nose cone in a way that leaves only small gaps, and with the half hexes they can be flush with the wing roots and other moving parts.
I’d expect to see a more complete set of heat shield components fly before SpaceX tests atmospheric entry.
https://twitter.com/starshipgazer/status/1401708724100730882QuoteSpaceX got a special delivery while I was there today. Looks like pallets of equipment to build a "Mini-Bakery" at Starbase. "The Bakery" is what they call the heat shield manufacturing facility in Cape Canaveral Florida. Now they can make heat shield tiles at Starbase also. 😃
Have we seen tiles for anything but flap and tank surfaces yet?We've seen the complete set- Hexes, half hexes, and two different sizes of smaller hexes. With the smaller hexes, they can tile the nose cone in a way that leaves only small gaps, and with the half hexes they can be flush with the wing roots and other moving parts.
I’d expect to see a more complete set of heat shield components fly before SpaceX tests atmospheric entry.
The half-hexes definitely help. Is there a diagram (better: photo!) showing how large + small hexes can cover a double-curved nosecone? The geometry isn’t obvious to me unless there are many sizes, and maybe additional shapes. Half-hexes could help cover a double-curved surface by providing straight(-ish) lines along which tiles can be out of register -- this can relax the nasty global distortions that result from wrapping a two-dimensional grid of aligned tiles over a curved surface.Have we seen tiles for anything but flap and tank surfaces yet?We've seen the complete set- Hexes, half hexes, and two different sizes of smaller hexes. With the smaller hexes, they can tile the nose cone in a way that leaves only small gaps, and with the half hexes they can be flush with the wing roots and other moving parts.
I’d expect to see a more complete set of heat shield components fly before SpaceX tests atmospheric entry.
Several examples across the posts on this page: https://forum.nasaspaceflight.com/index.php?topic=50748.900The half-hexes definitely help. Is there a diagram (better: photo!) showing how large + small hexes can cover a double-curved nosecone? The geometry isn’t obvious to me unless there are many sizes, and maybe additional shapes. Half-hexes could help cover a double-curved surface by providing straight(-ish) lines along which tiles can be out of register -- this can relax the nasty global distortions that result from wrapping a two-dimensional grid of aligned tiles over a curved surface.Have we seen tiles for anything but flap and tank surfaces yet?We've seen the complete set- Hexes, half hexes, and two different sizes of smaller hexes. With the smaller hexes, they can tile the nose cone in a way that leaves only small gaps, and with the half hexes they can be flush with the wing roots and other moving parts.
I’d expect to see a more complete set of heat shield components fly before SpaceX tests atmospheric entry.
All of these examples look pretty bad to me. There are large gaps that won’t go away.Several examples across the posts on this page: https://forum.nasaspaceflight.com/index.php?topic=50748.900 (https://forum.nasaspaceflight.com/index.php?topic=50748.900)The half-hexes definitely help. Is there a diagram (better: photo!) showing how large + small hexes can cover a double-curved nosecone? The geometry isn’t obvious to me unless there are many sizes, and maybe additional shapes. Half-hexes could help cover a double-curved surface by providing straight(-ish) lines along which tiles can be out of register -- this can relax the nasty global distortions that result from wrapping a two-dimensional grid of aligned tiles over a curved surface.Have we seen tiles for anything but flap and tank surfaces yet?We've seen the complete set- Hexes, half hexes, and two different sizes of smaller hexes. With the smaller hexes, they can tile the nose cone in a way that leaves only small gaps, and with the half hexes they can be flush with the wing roots and other moving parts.
I’d expect to see a more complete set of heat shield components fly before SpaceX tests atmospheric entry.
(it was further back than I thought!)
It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.All of these examples look pretty bad to me. There are large gaps that won’t go away.Several examples across the posts on this page: https://forum.nasaspaceflight.com/index.php?topic=50748.900 (https://forum.nasaspaceflight.com/index.php?topic=50748.900)The half-hexes definitely help. Is there a diagram (better: photo!) showing how large + small hexes can cover a double-curved nosecone? The geometry isn’t obvious to me unless there are many sizes, and maybe additional shapes. Half-hexes could help cover a double-curved surface by providing straight(-ish) lines along which tiles can be out of register -- this can relax the nasty global distortions that result from wrapping a two-dimensional grid of aligned tiles over a curved surface.Have we seen tiles for anything but flap and tank surfaces yet?We've seen the complete set- Hexes, half hexes, and two different sizes of smaller hexes. With the smaller hexes, they can tile the nose cone in a way that leaves only small gaps, and with the half hexes they can be flush with the wing roots and other moving parts.
I’d expect to see a more complete set of heat shield components fly before SpaceX tests atmospheric entry.
(it was further back than I thought!)
The pattern illustrated in this post (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2190404#msg2190404) is close to one that would work, but fixing it would require back-to-back half-hex tiles to relieve the alignment problem that I mentioned. (Look at the jagged gaps between row 5 and row 6, then imagine a straight line-of-latitude, half-hex interface instead.)
It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.Yes, but it’s not difficult to get much better packing with a hex + half-hex pattern, schematically something like this:
As you correctly identify there would be alignment problems. Having just a few tile shapes would lead to many gaps and using back to back half tiles would cause straight lines of sizable length that we know need to be avoided as they act as plasma channels.All of these examples look pretty bad to me. There are large gaps that won’t go away.Several examples across the posts on this page: https://forum.nasaspaceflight.com/index.php?topic=50748.900 (https://forum.nasaspaceflight.com/index.php?topic=50748.900)The half-hexes definitely help. Is there a diagram (better: photo!) showing how large + small hexes can cover a double-curved nosecone? The geometry isn’t obvious to me unless there are many sizes, and maybe additional shapes. Half-hexes could help cover a double-curved surface by providing straight(-ish) lines along which tiles can be out of register -- this can relax the nasty global distortions that result from wrapping a two-dimensional grid of aligned tiles over a curved surface.Have we seen tiles for anything but flap and tank surfaces yet?We've seen the complete set- Hexes, half hexes, and two different sizes of smaller hexes. With the smaller hexes, they can tile the nose cone in a way that leaves only small gaps, and with the half hexes they can be flush with the wing roots and other moving parts.
I’d expect to see a more complete set of heat shield components fly before SpaceX tests atmospheric entry.
(it was further back than I thought!)
The pattern illustrated in this post (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2190404#msg2190404) is close to one that would work, but fixing it would require back-to-back half-hex tiles to relieve the alignment problem that I mentioned. (Look at the jagged gaps between row 5 and row 6, then imagine a straight line-of-latitude, half-hex interface instead.)
One other issue as I mentioned above, is the straight line issue between the x's in your diagram.It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.Yes, but it’s not difficult to get much better packing with a hex + half-hex pattern, schematically something like this:
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
...but shifted to fit bumps into hollows, and allowing sheer/misalignment across the ⌫⌦ lines.
Things still get funny near the tip of the cone (see Slarty’s first post in this thread).
One other issue as I mentioned above, is the straight line issue between the x's in your diagram.It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.Yes, but it’s not difficult to get much better packing with a hex + half-hex pattern, schematically something like this:
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
...but shifted to fit bumps into hollows, and allowing sheer/misalignment across the ⌫⌦ lines.
Things still get funny near the tip of the cone (see Slarty’s first post in this thread).
I fear not. Try it with pencil and paper...One other issue as I mentioned above, is the straight line issue between the x's in your diagram.It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.Yes, but it’s not difficult to get much better packing with a hex + half-hex pattern, schematically something like this:
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
...but shifted to fit bumps into hollows, and allowing sheer/misalignment across the ⌫⌦ lines.
Things still get funny near the tip of the cone (see Slarty’s first post in this thread).
Stagger them?
Compared to some of the big-gap designs posted earlier, this seems not so bad!One other issue as I mentioned above, is the straight line issue between the x's in your diagram.It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.Yes, but it’s not difficult to get much better packing with a hex + half-hex pattern, schematically something like this:
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
...but shifted to fit bumps into hollows, and allowing sheer/misalignment across the ⌫⌦ lines.
Things still get funny near the tip of the cone (see Slarty’s first post in this thread).
I believe the only reason for the half tiles is for areas like the bottom of the skirt. Its a "straight line" (alright its a circle but...) and it doesn't matter about plasma here as its the edge of the ship. I would be very suprised to see these half tiles used anywhere other than this sort of edge situation.Compared to some of the big-gap designs posted earlier, this seems not so bad!One other issue as I mentioned above, is the straight line issue between the x's in your diagram.It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.Yes, but it’s not difficult to get much better packing with a hex + half-hex pattern, schematically something like this:
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
...but shifted to fit bumps into hollows, and allowing sheer/misalignment across the ⌫⌦ lines.
Things still get funny near the tip of the cone (see Slarty’s first post in this thread).
But trying to make sense of the engineering constraints, what about the straight line (=circumferential) grooves between back-to-back rows of half-hex tiles elsewhere on the vehicle? Unless I’m mistaken, these are part of the current design.
I also expect to see more tile sizes and shapes.
conical fairingWhere?
...
But we will see. It is perhaps possible they will have some other solution for the nose that does only include a few tile sizes and perhaps some filler or other clever device or perhaps bigger gaps don't matter, but IMO more tile sizes are more likely.
.Not that it changes your argument much but I believe that the second image is s simulation of the gas flow inside the wing resulting from the breached RCC panel.
[...]
Concerning airflow channels in the heat shield, here's an image from a simulation of surface air speeds against the heatshield of Columbia during its ill fated reentry after the leading edge was damaged. We can see that the resulting surface air speed in the area behind the damaged spot increased by an order of magnitude. This ultimately resulted in erosion and burn through and loss of vehicle and crew.
[...]
So the choices seem to be:
a) big gaps, or
b) straight channels, or
c) several (many?) more tile shapes, or
d) ??
So the choices seem to be:
a) big gaps, or
b) straight channels, or
c) several (many?) more tile shapes, or
d) ??
Would RCC panels like were used on the curved nose and wing leading edges work for the curved nose? You can form complicates curved shapes and they’re reusable
Would RCC panels like were used on the curved nose and wing leading edges work for the curved nose? You can form complicates curved shapes and they’re reusable
Technically yes, but they would need to be replaced after each flight, or if not every flight, at regular intervals.
They disspate heat through ablation
While they were indeed limited by oxidation they were rated for something like 50-100 flights depending on location according to the CAIB report.
Would RCC panels like were used on the curved nose and wing leading edges work for the curved nose? You can form complicates curved shapes and they’re reusable
Technically yes, but they would need to be replaced after each flight, or if not every flight, at regular intervals.
They disspate heat through ablation
I thought the RCC panels were coated with silicon carbide to reduce oxidation and allow them to be reusable. They weren’t ablative.
I know they were incredible expensive, but my comment was more around non-tile TPS for complicated surfaces
I strongly believe that Starship will have "perfect tiling", i.e. there will be no intentional gaps beyond those required by thermal contraction/expansion, vibrations and placement tolerances. It is going to need more types of tiles but it should be on the order of a few hundred with a decent number of tiles for most of them. For the nose cone I am personally a fan of the tapered hexagons suggested on the first page of this thread, with each row being identical. My addition would be a doubling once the tiles get wide enough which would require a handful of rows to use two mirrored pentagonal tile types instead.The narrowing hexagon approach on page 1 shows promise but will potentially suffer from narrow tiles towards the nose tip. So I'm interested in your double pentagon tile idea but I can't quite imagine them. Would these tiles have a some concave edges? And how would they link up with the hexagonal tiles? I note that the hex "grain" on starship runs around the circumference rather than vertically up the side. Any chance of a diagram?
Paraphrasing Elon in the Joe Rogan podcast:
You have to get the gaps just right, if it gets too big you get plasma in the crack (and that's bad) and if it's too small they are going to bang together.
If cm scale gaps were ok they would hardly be concerned about differential thermal expansion and vibrations. Sure, Starship would likely survive with big gaps or even missing tiles. The blankets are made from similar materials and could survive similar temperatures as the tiles (if not higher depending on composition) but turbulence, shock impingement and lower emissivity would lead to higher temperatures. The steel can get quite hot before failing but will start to anneal and lose the hardening at a significantly lower temperature - fine for survivability but likely instant scrapping if it happens in the tanks.
Also remember that re-entries from LEO, while being by far the most common case, represent the lower end of the performance envelope. I am really curious as to how far they can take the reusable tiles or whether they will need ablative solutions for high energy tankers or lunar/Mars returns.
Does anyone know (or have an estimate of) the curve function of the current nose? If the rate of change of tangent angle is relatively constant (Sphere, cone, or Ogive should satisfy that) you can use a single tapered tile design to tile the entire nose. If it changes (e.g. curvature increases with height, e.g. a Parabolic curve) then several 'steps' would be needed with increasing tapers, depending on the allowable tolerance.I believe it is an ogive curve with a variable rate of curvature. A separate tile shape will be needed for each line of latitude of the nose if the intention is to make it a snug fit (which seems to be very likely).
This also may be the reason the nose is 'pointier than necessary': By reducing the curvature, you reduce the number of tile variants needed for a given tolerance.
"... is it enough?" is probably a question SX has too. For SX, good enough next week is better than perfect in three years.It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.All of these examples look pretty bad to me. There are large gaps that won’t go away.Several examples across the posts on this page: https://forum.nasaspaceflight.com/index.php?topic=50748.900 (https://forum.nasaspaceflight.com/index.php?topic=50748.900)The half-hexes definitely help. Is there a diagram (better: photo!) showing how large + small hexes can cover a double-curved nosecone? The geometry isn’t obvious to me unless there are many sizes, and maybe additional shapes. Half-hexes could help cover a double-curved surface by providing straight(-ish) lines along which tiles can be out of register -- this can relax the nasty global distortions that result from wrapping a two-dimensional grid of aligned tiles over a curved surface.Have we seen tiles for anything but flap and tank surfaces yet?We've seen the complete set- Hexes, half hexes, and two different sizes of smaller hexes. With the smaller hexes, they can tile the nose cone in a way that leaves only small gaps, and with the half hexes they can be flush with the wing roots and other moving parts.
I’d expect to see a more complete set of heat shield components fly before SpaceX tests atmospheric entry.
(it was further back than I thought!)
The pattern illustrated in this post (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2190404#msg2190404) is close to one that would work, but fixing it would require back-to-back half-hex tiles to relieve the alignment problem that I mentioned. (Look at the jagged gaps between row 5 and row 6, then imagine a straight line-of-latitude, half-hex interface instead.)
The half tiles are really larger than half. They are big enough to cover three pins. To butt flat to flat either the apex to flat dimension is the same as a normal tiles apex to apex, or the pin pattern would have to change. If used only as edging, this problem goes away.I believe the only reason for the half tiles is for areas like the bottom of the skirt. Its a "straight line" (alright its a circle but...) and it doesn't matter about plasma here as its the edge of the ship. I would be very suprised to see these half tiles used anywhere other than this sort of edge situation.Compared to some of the big-gap designs posted earlier, this seems not so bad!One other issue as I mentioned above, is the straight line issue between the x's in your diagram.It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.Yes, but it’s not difficult to get much better packing with a hex + half-hex pattern, schematically something like this:
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
...but shifted to fit bumps into hollows, and allowing sheer/misalignment across the ⌫⌦ lines.
Things still get funny near the tip of the cone (see Slarty’s first post in this thread).
But trying to make sense of the engineering constraints, what about the straight line (=circumferential) grooves between back-to-back rows of half-hex tiles elsewhere on the vehicle? Unless I’m mistaken, these are part of the current design.
I also expect to see more tile sizes and shapes.
So the choices seem to be:
a) big gaps, or
b) straight channels, or
c) several (many?) more tile shapes, or
d) ??
It's actually pretty important that the heatshield have a smooth surface. You need laminar airflow beneath it, and if it becomes turbulent, the surface temperature will rise drastically.The dramatic heating was downstream of the protuberance. The heating around the elavon gap was less pronounce but it may have been more dramatic if it hadn't run out of airframe. Still, the impact of a channel isn't quite the same as something sticking up into the laminar flow. Surely there is some relationship between the laminar flow mach number and the gap dimensions. If there isn't, no gap is acceptable, including that formed by the slightly rounded edges of the tiles even if butted tight together.
Here we can see an image of the heat shield of STS 128, in which they intentionally raised one of the tiles about a quarter inch above the surrounding tiles as part of an experiment concerning heat shield peak heating. Notice how turbulence from that single slightly raised tile caused a large area around it to experience significantly greater heating.
Concerning airflow channels in the heat shield, here's an image from a simulation of surface air speeds against the heatshield of Columbia during its ill fated reentry after the leading edge was damaged. We can see that the resulting surface air speed in the area behind the damaged spot increased by an order of magnitude. This ultimately resulted in erosion and burn through and loss of vehicle and crew.
It should be clear that the small scale aerodynamics around the heat shield are very sensitive, and the gaps between tiles have to be carefully dealt with. The "rough fit" suggestions I see are honestly probably worse than no head shield at all, since at least if you don't have a heat shield, you have a nice smooth body with laminar flow, and the peak heating will drop by a good 500C degrees from turbulent flow that a rough heat shield would cause. Or possible the heat difference could be much more. The laminar flow region is providing a protective shield against the air in the shockwave, which will be in the 5000C degrees range, hot enough to vaporize every material known to mankind. Disturb the flow separation at your own risk!
[zubenelgenubi: Attach image files. Do not embed them.]
So the choices seem to be:
a) big gaps, or
b) straight channels, or
c) several (many?) more tile shapes, or
d) ??
Hemispherical nose cone could allow for tiling via a Goldberg polyhedron, which would have relatively few tile shapes. Would probably require the use of an extensible drag-reducing aerospike for launch, and retesting the control system for the belly flop.
If there are many tiles between the pentagons, then there must be hexagons of many different sizes and shapes: Regular grid, meet spherical distortion.So the choices seem to be:
a) big gaps, or
b) straight channels, or
c) several (many?) more tile shapes, or
d) ??
Hemispherical nose cone could allow for tiling via a Goldberg polyhedron, which would have relatively few tile shapes. Would probably require the use of an extensible drag-reducing aerospike for launch, and retesting the control system for the belly flop.
So if I read that correctly then a there are 3 tile shapes and sizes? gp(3,0)
https://en.wikipedia.org/wiki/Goldberg_polyhedron (https://en.wikipedia.org/wiki/Goldberg_polyhedron)
The apex to flat is 133 pixels. Apex to apex is 169. In both cases the vertical side is 83 pixels. These flats are the same as the full hex except they're cut off from the 10 o'clock to the 2 o'clock apexes. They are for edges. If used anywhere else the pin pattern would have to change. Not impossible.The half tiles are really larger than half. They are big enough to cover three pins. To butt flat to flat either the apex to flat dimension is the same as a normal tiles apex to apex, or the pin pattern would have to change. If used only as edging, this problem goes away.I believe the only reason for the half tiles is for areas like the bottom of the skirt. Its a "straight line" (alright its a circle but...) and it doesn't matter about plasma here as its the edge of the ship. I would be very suprised to see these half tiles used anywhere other than this sort of edge situation.Compared to some of the big-gap designs posted earlier, this seems not so bad!One other issue as I mentioned above, is the straight line issue between the x's in your diagram.It may look bad, but the question is, is it enough? The hot structure concept means that you dont need 100% coverage, so some large games may be fine if they are otherwise supported.Yes, but it’s not difficult to get much better packing with a hex + half-hex pattern, schematically something like this:
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
⌦⎔⎔⎔⌫⌦⎔⎔⌫
...but shifted to fit bumps into hollows, and allowing sheer/misalignment across the ⌫⌦ lines.
Things still get funny near the tip of the cone (see Slarty’s first post in this thread).
But trying to make sense of the engineering constraints, what about the straight line (=circumferential) grooves between back-to-back rows of half-hex tiles elsewhere on the vehicle? Unless I’m mistaken, these are part of the current design.
I also expect to see more tile sizes and shapes.
I think apex to flat is a smaller than apex to apex. Sigh, time to use a real computer and do some pixel counting.
Very interesting, although unfortunately the nose of Starship has a variable curvature so this would not work as described. That said there might be some scope especially as the tiles only cover half the ship, but I doubt it. We shall see.So the choices seem to be:
a) big gaps, or
b) straight channels, or
c) several (many?) more tile shapes, or
d) ??
Hemispherical nose cone could allow for tiling via a Goldberg polyhedron, which would have relatively few tile shapes. Would probably require the use of an extensible drag-reducing aerospike for launch, and retesting the control system for the belly flop.
So if I read that correctly then a there are 3 tile shapes and sizes? gp(3,0)
https://en.wikipedia.org/wiki/Goldberg_polyhedron
Behold the Diagrams! Quick and dirty with greatly exaggerated differences between rows - if one limits tiles to the same maximum dimensions then a doubling is only needed for every factor of 2 change in nose radius. The one I meant was the first one but the others are options if one wants to avoid the two tile long straight gap at the cost of a notched tile or a smaller insert diamond tile (which can be bigger at the cost of three instead of two types of tiles).I strongly believe that Starship will have "perfect tiling", i.e. there will be no intentional gaps beyond those required by thermal contraction/expansion, vibrations and placement tolerances. It is going to need more types of tiles but it should be on the order of a few hundred with a decent number of tiles for most of them. For the nose cone I am personally a fan of the tapered hexagons suggested on the first page of this thread, with each row being identical. My addition would be a doubling once the tiles get wide enough which would require a handful of rows to use two mirrored pentagonal tile types instead.The narrowing hexagon approach on page 1 shows promise but will potentially suffer from narrow tiles towards the nose tip. So I'm interested in your double pentagon tile idea but I can't quite imagine them. Would these tiles have a some concave edges? And how would they link up with the hexagonal tiles? I note that the hex "grain" on starship runs around the circumference rather than vertically up the side. Any chance of a diagram?
Paraphrasing Elon in the Joe Rogan podcast:
You have to get the gaps just right, if it gets too big you get plasma in the crack (and that's bad) and if it's too small they are going to bang together.
If cm scale gaps were ok they would hardly be concerned about differential thermal expansion and vibrations. Sure, Starship would likely survive with big gaps or even missing tiles. The blankets are made from similar materials and could survive similar temperatures as the tiles (if not higher depending on composition) but turbulence, shock impingement and lower emissivity would lead to higher temperatures. The steel can get quite hot before failing but will start to anneal and lose the hardening at a significantly lower temperature - fine for survivability but likely instant scrapping if it happens in the tanks.
Also remember that re-entries from LEO, while being by far the most common case, represent the lower end of the performance envelope. I am really curious as to how far they can take the reusable tiles or whether they will need ablative solutions for high energy tankers or lunar/Mars returns.
It would be handy if there was just one tile for the entire ship, but there won't be. Its no big deal its not the shuttle. There seems to be a fixation on the idea that there has to be just a handful of tile types. There doesn't.
Behold the Diagrams! Quick and dirty with greatly exaggerated differences between rows - if one limits tiles to the same maximum dimensions then a doubling is only needed for every factor of 2 change in nose radius. The one I meant was the first one but the others are options if one wants to avoid the two tile long straight gap at the cost of a notched tile or a smaller insert diamond tile (which can be bigger at the cost of three instead of two types of tiles).
Go ahead and work out the number of up/down lift movements, operator reaches, choice mistakes, at 40 meters in the air while dealing with 3 parts. Now do that for 30 parts. It'll be an order of magnitude more difficult for the 30 parts version.But what if there is just one kind of tile per row, or two at most? The complexity seems pretty low (very repetitive work), and tiles can be stenciled with row numbers and this-side-up arrows.
Go ahead and work out the number of up/down lift movements, operator reaches, choice mistakes, at 40 meters in the air while dealing with 3 parts. Now do that for 30 parts. It'll be an order of magnitude more difficult for the 30 parts version.But what if there is just one kind of tile per row, or two at most? The complexity seems pretty low (very repetitive work), and tiles can be stenciled with row numbers and this-side-up arrows.
One or two shapes per row is enough to enable a perfect fit over the whole structure, but using fewer and fewer tile-shapes leads to worse and worse gaps. I’ve seen no good solution with regular hexagons regardless of shape. The reasons seem inherent in the geometry of the surface.
Cover a sphere with lines of latitude and longitude, and note that the rectangle-like grid will have different shapes at every latitude (and triangles around the poles). Show me how a few tile shapes can cover a sphere, and I’ll be happy and amazed. Show me how two sizes of hexagons can do the job, and I’ll be astounded.Go ahead and work out the number of up/down lift movements, operator reaches, choice mistakes, at 40 meters in the air while dealing with 3 parts. Now do that for 30 parts. It'll be an order of magnitude more difficult for the 30 parts version.But what if there is just one kind of tile per row, or two at most? The complexity seems pretty low (very repetitive work), and tiles can be stenciled with row numbers and this-side-up arrows.
One or two shapes per row is enough to enable a perfect fit over the whole structure, but using fewer and fewer tile-shapes leads to worse and worse gaps. I’ve seen no good solution with regular hexagons regardless of shape. The reasons seem inherent in the geometry of the surface.
There is a good solution involving non-hexagons in the thread just above. Picture #1 and Picture #2 look workable, and there's 4 different tiles total.
with unique tiles per row, after every row, the picker machine (or human) must unload and reload their feeder. Furthermore you can only work on about 2-3 rows at at a time (depending on how many rows per type), which requires horizontal movements. doable on a scaffolding or rotating stand but possibly inefficient if the robot or human's reach is more than 3 rows , but vertical movements are far easier on a lift than horizontal movements around a circle.
The nosecone from a drawing I found is 14 meters, so that's 20-40 tile types you are talking about. Inventory management is going to be so fun. The "ooops we dropped one and ran out" problem means an extra two tiles, x 30, versus a handful of extras if there's a handful of tile types. Not to mention storage area, the tiles will look pretty similar between rows leading to confusion.
I'm sure I'm forgetting about another half dozen reasons why "no part is the best part" and "the fewer parts the better"
The arguments are asymmetrical, it's much more difficult to talk someone out of extra parts than to talk someone into an extra part. So "no part is the best part" was the mantra we used in manufacturing, just like Elon, and any vaguely looking tie in a design argument automatically went to the solution with less parts, without further discussion. Engineering managers ruthlessly enforced this discipline.
In other words the burden of proof is on the engineer asking for the extra part (that'd be you). Maybe you should point out why the 3-5 part solutions in this thread are lacking. Some of them do not involve extra gaps.
Is there a limit on the size and shape of the tile? Is there a reason they can't make a single piece, to cover the entire nose cone?
Cover a sphere with lines of latitude and longitude, and note that the rectangle-like grid will have different shapes at every latitude (and triangles around the poles). Show me how a few tile shapes can cover a sphere, and I’ll be happy and amazed. Show me how two sizes of hexagons can do the job, and I’ll be astounded.Goldberg Polyhedra (https://en.wikipedia.org/wiki/Goldberg_polyhedron) were referenced jsut a few posts back. One tiling uses two sizes of hex and one size of pentagon to seamlessly tile a sphere. The Starship case is easier than a sphere: because only tiling a partial surface is required and the edge conditions are undefined (i.e. you don't need to match up to an exact line) there may be even more efficient tiling's available. For example, one that uses two hex sizes plus a dedicated TPS application for the tip of the nose.
Shuttle used carbon-carbon at leading edges and nose, and X-37B uses TUFROC is same purpose. Maybe we see long rumored TUFROCX at SS nose and bodyflaps...Is there a limit on the size and shape of the tile? Is there a reason they can't make a single piece, to cover the entire nose cone?
tiles are quite fragile, so big size are worse for vibration, and in case of damage you can't repair only one tile.
A large (many-tile) triangular facet (the corners are in the pentagons) cannot be accurately tiled with regular hexagons, much less by hexagons of a single size. Think of a sheet of paper with a regular hexagonal grid printed on it. Paste it on a sphere, get creases. Precise tiling can’t work because geometry. Full stop.Cover a sphere with lines of latitude and longitude, and note that the rectangle-like grid will have different shapes at every latitude (and triangles around the poles). Show me how a few tile shapes can cover a sphere, and I’ll be happy and amazed. Show me how two sizes of hexagons can do the job, and I’ll be astounded.Goldberg Polyhedra (https://en.wikipedia.org/wiki/Goldberg_polyhedron) were referenced jsut a few posts back. One tiling uses two sizes of hex and one size of pentagon to seamlessly tile a sphere. The Starship case is easier than a sphere: because only tiling a partial surface is required and the edge conditions are undefined (i.e. you don't need to match up to an exact line) there may be even more efficient tiling's available. For example, one that uses two hex sizes plus a dedicated TPS application for the tip of the nose.
A large (many-tile) triangular facet (the corners are in the pentagons) cannot be accurately tiled with regular hexagons, much less by hexagons of a single size.
Why two sizes, not one or twenty? In harsh, immutable, geometric reality, a set of polygons with only two or three shapes can form only curved polyhedral surfaces with very few facets compared to the number of tiles on the SS nosecone. I invite anyone to try to find an actual example of a few shapes tiling a sphere with an unbounded number of facets. The claims that posters have made regarding Goldberg polyhedra are mistaken.A large (many-tile) triangular facet (the corners are in the pentagons) cannot be accurately tiled with regular hexagons, much less by hexagons of a single size.
I don't think there's any suggestion that the hexagons on the surface of a Goldberg polyhedron are the same size, or even regular. GPs have three rules: faces must be pentagonal or hexagonal, they must meet at 3-cornered vertices, and they have icosahedral symmetry. Nothing in there about regular polygons - although I expect the pentagons are regular, and the hexagons are sometimes regular.
So the previous post, which said that one arrangement had pentagons and two sizes of hexagon, seems perfectly reasonable to me.
Why two sizes, not one or twenty? In harsh, immutable, geometric reality, a set of polygons with only two or three shapes can form only curved polyhedral surfaces with very few facets compared to the number of tiles on the SS nosecone. I invite anyone to try to find an actual example of a few shapes tiling a sphere with an unbounded number of facets. The claims that posters have made regarding Goldberg polyhedra are mistaken.A large (many-tile) triangular facet (the corners are in the pentagons) cannot be accurately tiled with regular hexagons, much less by hexagons of a single size.
I don't think there's any suggestion that the hexagons on the surface of a Goldberg polyhedron are the same size, or even regular. GPs have three rules: faces must be pentagonal or hexagonal, they must meet at 3-cornered vertices, and they have icosahedral symmetry. Nothing in there about regular polygons - although I expect the pentagons are regular, and the hexagons are sometimes regular.
So the previous post, which said that one arrangement had pentagons and two sizes of hexagon, seems perfectly reasonable to me.
Many people apparently have strong but misleading intuitions about this kind of question. (Intuition test:
Why are there no more than 5 Platonic solids and 13 Archimedean solids (https://en.wikipedia.org/wiki/Archimedean_solid)?
In harsh, immutable, geometric reality, a set of polygons with only two or three shapes can form only curved polyhedral surfaces with very few facets compared to the number of tiles on the SS nosecone.Luckily Starship only needs to fly in the upper atmosphere rather than in a world of perfect polyhedra, so it is acceptable to have varying gaps between tiles, varying tile tangents, and incomplete tilings (stick all your singularities on the back where you aren't applying any tiles) as long as they are within acceptable tolerances.
Why two sizes, not one or twenty? In harsh, immutable, geometric reality, a set of polygons with only two or three shapes can form only curved polyhedral surfaces with very few facets compared to the number of tiles on the SS nosecone. I invite anyone to try to find an actual example of a few shapes tiling a sphere with an unbounded number of facets. The claims that posters have made regarding Goldberg polyhedra are mistaken.A large (many-tile) triangular facet (the corners are in the pentagons) cannot be accurately tiled with regular hexagons, much less by hexagons of a single size.
I don't think there's any suggestion that the hexagons on the surface of a Goldberg polyhedron are the same size, or even regular. GPs have three rules: faces must be pentagonal or hexagonal, they must meet at 3-cornered vertices, and they have icosahedral symmetry. Nothing in there about regular polygons - although I expect the pentagons are regular, and the hexagons are sometimes regular.
So the previous post, which said that one arrangement had pentagons and two sizes of hexagon, seems perfectly reasonable to me.
Many people apparently have strong but misleading intuitions about this kind of question. (Intuition test:
Why are there no more than 5 Platonic solids and 13 Archimedean solids (https://en.wikipedia.org/wiki/Archimedean_solid)?
In harsh, immutable, geometric reality, a set of polygons with only two or three shapes can form only curved polyhedral surfaces with very few facets compared to the number of tiles on the SS nosecone.Luckily Starship only needs to fly in the upper atmosphere rather than in a world of perfect polyhedra, so it is acceptable to have varying gaps between tiles, varying tile tangents, and incomplete tilings (stick all your singularities on the back where you aren't applying any tiles) as long as they are within acceptable tolerances.
In harsh, immutable, geometric reality, a set of polygons with only two or three shapes can form only curved polyhedral surfaces with very few facets compared to the number of tiles on the SS nosecone.Luckily Starship only needs to fly in the upper atmosphere rather than in a world of perfect polyhedra, so it is acceptable to have varying gaps between tiles, varying tile tangents, and incomplete tilings (stick all your singularities on the back where you aren't applying any tiles) as long as they are within acceptable tolerances.
This times 1000. They’ll get most of the way there and then fudge as needed.
I still think it’s interesting to ask what basic approach they’ll take before they fudge their way to the finish line (that’s not intended as a criticism) - tiling a cone with curved sides is not easily done without a lot of tile variation or comparatively complex (and irregular, with regard to the tiles appearing along a slice in the direction of airflow) tilings.
I imagine this has been covered in this thread (there’s a lot here...), but the basic approach the shuttle took to its curved surfaces is just tons and tons of tiles of differing sizes, right?
I’m not sure what word to use, but I mean something like “geometric features that would correspond to closely-fit tiles that cover a sphere”. (Thanks, I’ve fixed the link.)Why two sizes, not one or twenty? In harsh, immutable, geometric reality, a set of polygons with only two or three shapes can form only curved polyhedral surfaces with very few facets compared to the number of tiles on the SS nosecone. I invite anyone to try to find an actual example of a few shapes tiling a sphere with an unbounded number of facets. The claims that posters have made regarding Goldberg polyhedra are mistaken.A large (many-tile) triangular facet (the corners are in the pentagons) cannot be accurately tiled with regular hexagons, much less by hexagons of a single size.
I don't think there's any suggestion that the hexagons on the surface of a Goldberg polyhedron are the same size, or even regular. GPs have three rules: faces must be pentagonal or hexagonal, they must meet at 3-cornered vertices, and they have icosahedral symmetry. Nothing in there about regular polygons - although I expect the pentagons are regular, and the hexagons are sometimes regular.
So the previous post, which said that one arrangement had pentagons and two sizes of hexagon, seems perfectly reasonable to me.
Many people apparently have strong but misleading intuitions about this kind of question. (Intuition test:
Why are there no more than 5 Platonic solids and 13 Archimedean solids (https://en.wikipedia.org/wiki/Archimedean_solid)? (https://en.wikipedia.org/wiki/Archimedean_solid)?)
You’ll want to add a space before the closing parenthesis or it becomes part of the link.
Can you explain the use/meaning of the “facets” in the sentence above? Does it refer to the tiles? It sounds like it refers to facets of the sphere, which doesn’t make sense (at least to me).
I’m not sure what word to use, but I mean something like “geometric features that would correspond to closely-fit tiles that cover a sphere”. (Thanks, I’ve fixed the link.)Why two sizes, not one or twenty? In harsh, immutable, geometric reality, a set of polygons with only two or three shapes can form only curved polyhedral surfaces with very few facets compared to the number of tiles on the SS nosecone. I invite anyone to try to find an actual example of a few shapes tiling a sphere with an unbounded number of facets. The claims that posters have made regarding Goldberg polyhedra are mistaken.A large (many-tile) triangular facet (the corners are in the pentagons) cannot be accurately tiled with regular hexagons, much less by hexagons of a single size.
I don't think there's any suggestion that the hexagons on the surface of a Goldberg polyhedron are the same size, or even regular. GPs have three rules: faces must be pentagonal or hexagonal, they must meet at 3-cornered vertices, and they have icosahedral symmetry. Nothing in there about regular polygons - although I expect the pentagons are regular, and the hexagons are sometimes regular.
So the previous post, which said that one arrangement had pentagons and two sizes of hexagon, seems perfectly reasonable to me.
Many people apparently have strong but misleading intuitions about this kind of question. (Intuition test:
Why are there no more than 5 Platonic solids and 13 Archimedean solids (https://en.wikipedia.org/wiki/Archimedean_solid)? (https://en.wikipedia.org/wiki/Archimedean_solid)?)
You’ll want to add a space before the closing parenthesis or it becomes part of the link.
Can you explain the use/meaning of the “facets” in the sentence above? Does it refer to the tiles? It sounds like it refers to facets of the sphere, which doesn’t make sense (at least to me).
Yes, there are some strong opinions about the allowable size of the set of tile types - 1 being a common suggestion ::)I imagine this has been covered in this thread (there’s a lot here...), but the basic approach the shuttle took to its curved surfaces is just tons and tons of tiles of differing sizes, right?Yes, and that took an estimated 300 man-years to install on Columbia (see earlier post), so I think the people in this thread are hoping there is a better solution. There are a lot of smart people in NSF, so it is possible they will even come up with an idea that SpaceX has not thought of. Until they read this thread. :)
The 5 Platonic solids are about angles and angle defects. When you stick shapes with more than N sides together in the manner of a Platonic solid, you need some leftover angle to make the tiling non-flat (and at least 3 sides meeting). The corner angle of a 6 sided polygon is 132 degrees, so you can’t put 3 of them in to 360 degrees.The extension of this to the 13 Archimedean Solids is pretty straightforward. Does this answer your question: https://ywhmaths.webs.com/Geometry/ArchimedeanSolids.pdf
I would be curious to hear an intuitive explanation of the Archimedean solids, I can’t see one, but I never studied topology either.
This is the principle of the Goldberg polyhedra mentioned above (and geodesic domes which are their mathematical duals). The result will be very nice looking surfaces covered with almost regular polygons of similar sizes (can be chosen to be mostly hexagons with some pentagons and/or diamonds) - but each tile will more or less be unique.It can be quite a lot less than unique, e.g. 5 hexagon variants and one pentagon variant (http://dmccooey.com/polyhedra/DualGeodesicIcosahedron13.html). Even better, many of those variants have edge lengths within 1% of each other, so those 5 variants could be covered by 3 or maybe 2 variants depending on acceptable gap variance. But on top of that, you do not need to perfectly tile Starship, you only need a partial tiling, which means many of the problems encountered in perfect sphere tilings simply are not problems in the first place.
The issue with the half tile pentagon is that it leaves "channels" running circumferentially around the starship. Folks have *claimed* that such unimpeded plasma paths would be Very Bad and so I think we've mostly avoided using them.
I asked a question earlier about laminar flow velocity in relation to groove dimension and got no reply. There must be some spherical cow relationship for a starting point in figuring out what depth, width and angle relationships might introduce turbulence. I can't even figure out search terms to look this up without the search itself becoming a research project.The issue with the half tile pentagon is that it leaves "channels" running circumferentially around the starship. Folks have *claimed* that such unimpeded plasma paths would be Very Bad and so I think we've mostly avoided using them.
One of those "folks" is Elon himself.
Given that SpaceX are undisputed experts at Computational Fluid Dynamics (CFD) simulations, I'm inclined to believe him.
Yes, for a sphere you have the inherent symmetry of the base polyhedron around each of the original vertices. The problem is when you deform it into a ogive surface so that the symmetry is only preserved perpendicular to the rotational axis...This is the principle of the Goldberg polyhedra mentioned above (and geodesic domes which are their mathematical duals). The result will be very nice looking surfaces covered with almost regular polygons of similar sizes (can be chosen to be mostly hexagons with some pentagons and/or diamonds) - but each tile will more or less be unique.It can be quite a lot less than unique, e.g. 5 hexagon variants and one pentagon variant (http://dmccooey.com/polyhedra/DualGeodesicIcosahedron13.html). Even better, many of those variants have edge lengths within 1% of each other, so those 5 variants could be covered by 3 or maybe 2 variants depending on acceptable gap variance. But on top of that, you do not need to perfectly tile Starship, you only need a partial tiling, which means many of the problems encountered in perfect sphere tilings simply are not problems in the first place.
Just to add some ballpark numbers:
Height: Radius: # of tiles
8m 4.00m 33
9m 3.85m 31
10m 3.68m 30
11m 3.49m 28
12m 3.27m 27
13m 3.04m 25
14m 2.78m 23
15m 2.51m 20
16m 2.20m 18
17.24m 1.80m 15
Here’s a re-drawn illustration that shows the geometric principle of a scheme that can double/halve the number of tiles in a circumferential band (imagine this on paper wrapped around a cone). This is directly comparable to schemes illustrated by other posters above, but the tile shapes are closer to hexagonal. Also, it’s cool and looks like 5-7 defects in graphene.It would help if you labeled each tile size/shape - think I count 7?
Just to add some ballpark numbers:SpaceX have very nicely simplified our pixel counting by providing a ruler - many of the barrel sections have the circumference labeled in increments of 20 cm, see for example this post from SN10 (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2185904#msg2185904).
From https://forum.nasaspaceflight.com/index.php?topic=51474.msg2111091#msg2111091 we have an estimate of tile being 35cm-40cm, presumably across the flats (not point to point). I'm going to use 38.5cm as the flat-to-flat distance, because it makes 6 rows fit exactly in 2m, which is convenient for this estimate. (Two rows fit in 1.5 x the point-to-point height because of the way the hexagons tile.)
[...]
The 5 Platonic solids are about angles and angle defects. When you stick shapes with more than N sides together in the manner of a Platonic solid, you need some leftover angle to make the tiling non-flat (and at least 3 sides meeting). The corner angle of a 6 sided polygon is 132 degrees, so you can’t put 3 of them in to 360 degrees.The extension of this to the 13 Archimedean Solids is pretty straightforward. Does this answer your question: https://ywhmaths.webs.com/Geometry/ArchimedeanSolids.pdf
I would be curious to hear an intuitive explanation of the Archimedean solids, I can’t see one, but I never studied topology either.
I asked a question earlier about laminar flow velocity in relation to groove dimension and got no reply. There must be some spherical cow relationship for a starting point in figuring out what depth, width and angle relationships might introduce turbulence. I can't even figure out search terms to look this up without the search itself becoming a research project.The issue with the half tile pentagon is that it leaves "channels" running circumferentially around the starship. Folks have *claimed* that such unimpeded plasma paths would be Very Bad and so I think we've mostly avoided using them.
One of those "folks" is Elon himself.
Given that SpaceX are undisputed experts at Computational Fluid Dynamics (CFD) simulations, I'm inclined to believe him.
There are 5 shapes shown -- each all-hexagon band has a single, bilaterally symmetric tile shape.Here’s a re-drawn illustration that shows the geometric principle of a scheme that can double/halve the number of tiles in a circumferential band (imagine this on paper wrapped around a cone). This is directly comparable to schemes illustrated by other posters above, but the tile shapes are closer to hexagonal. Also, it’s cool and looks like 5-7 defects in graphene.It would help if you labeled each tile size/shape - think I count 7?
Indeed, for a flat cone you can re-use the same tapered hexagons whenever the radius doubles but for a ogive each row is unique as the surface angle changes as well. It should however be possible to use the same hexagon (upside down) for the bottom row and the first transition row by tweaking the pentagons and heptagons.There are 5 shapes shown -- each all-hexagon band has a single, bilaterally symmetric tile shape.Here’s a re-drawn illustration that shows the geometric principle of a scheme that can double/halve the number of tiles in a circumferential band (imagine this on paper wrapped around a cone). This is directly comparable to schemes illustrated by other posters above, but the tile shapes are closer to hexagonal. Also, it’s cool and looks like 5-7 defects in graphene.It would help if you labeled each tile size/shape - think I count 7?
BTW, the role of the illustrated pattern is the same as the role of the patterns in eriblo’s diagrams here (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2250067#msg2250067). The number of shapes required for a whole nosecone depends less on the doubling/halving bands than it does on the tolerance for gap variations in the more numerous bands of tapered hexagons. Hexagon shapes can be reused if gaps are allowed to vary a bit, but perfect tiling requires one shape per row.
Still, you can print this out and cut it out and tape it together and see how smooth/lumpy it ends up.These will not be nice:
Yes, but your 5-6-7 pattern will be almost the same. The vertex angle is related to how much you are reducing the circumference. I'm doing "1 hex flat-to-flat width in one row", your 5-6-7 pattern reduces the circumference 2 hex widths in 3(ish) rows. So the polyhedron vertex angle is much the same.Still, you can print this out and cut it out and tape it together and see how smooth/lumpy it ends up.These will not be nice:
Try what you suggested above, starting with just a small, single-diamond region if you want: Cut it out, tape it together, and post a photo.Yes, but your 5-6-7 pattern will be almost the same. The vertex angle is related to how much you are reducing the circumference. I'm doing "1 hex flat-to-flat width in one row", your 5-6-7 pattern reduces the circumference 2 hex widths in 3(ish) rows. So the polyhedron vertex angle is much the same.Still, you can print this out and cut it out and tape it together and see how smooth/lumpy it ends up.These will not be nice:
You can snub the vertex to smooth it out by using a larger composite tile at the vertex. In the diamond defect case you can do this just by fusing the diamond to one or all of the adjacent hexagons -- and you'd still only have two tile shapes.
Your version effectively uses five tile shapes to snub the vertex in a slightly different way.
But the real improvement would be a scheme to reduce the circumference by a small fraction of a full flat-to-flat width. The would increase the number of vertices in the polyhedral approximation.
The inescapable conclusion from the last couple of pages is that they'll just have to ditch the sexy 50-cal bullet shape of Starship and transmogrify it into a tubby cylinder with a half-sphere on top. A heavy but necessary sacrifice on the altar of geometry...Or maybe use 1/100 as many distinct tile shapes as there are distinct components in a Raptor (to pick a ratio out of Mars-thin air). Horrors!
Try what you suggested above, starting with just a small, single-diamond region if you want: Cut it out, tape it together, and post a photo.I'd like to encourage you to do the same: expand your 5-6-7 into a full nose cone. You'll see that each 5-6-7 places a vertex in a polyhedron approximation of the nose cone, and you'll have plenty of 6-6-6 "normal hexes" in between (because the nose cone does not taper all that quickly).
Also, in the 5-7 tilt.jpg image above, there are no vertices in the sense that I think you mean. The defects tilt the adjacent regions rather than forcing conical protrusions (5 + 7 = 6 + 6).Tilting adjacent faces makes a vertex.
I’ve suggested that you make a physical model of a small patch, not “a full nose cone”. You will find that it is a hopeless non-starter. I have nothing more to say. Here is the pattern again, a detail pulled from your large diagram:Try what you suggested above, starting with just a small, single-diamond region if you want: Cut it out, tape it together, and post a photo.I'd like to encourage you to do the same: expand your 5-6-7 into a full nose cone.
The problem with these designs (and with the original on page 1) is that each row of tiles requires a different shape. In these examples there are 4 rows and 4 or more tile types. The top row is not compatible with the bottom row as the hexagon side lengths are different.Behold the Diagrams! Quick and dirty with greatly exaggerated differences between rows - if one limits tiles to the same maximum dimensions then a doubling is only needed for every factor of 2 change in nose radius. The one I meant was the first one but the others are options if one wants to avoid the two tile long straight gap at the cost of a notched tile or a smaller insert diamond tile (which can be bigger at the cost of three instead of two types of tiles).I strongly believe that Starship will have "perfect tiling", i.e. there will be no intentional gaps beyond those required by thermal contraction/expansion, vibrations and placement tolerances. It is going to need more types of tiles but it should be on the order of a few hundred with a decent number of tiles for most of them. For the nose cone I am personally a fan of the tapered hexagons suggested on the first page of this thread, with each row being identical. My addition would be a doubling once the tiles get wide enough which would require a handful of rows to use two mirrored pentagonal tile types instead.The narrowing hexagon approach on page 1 shows promise but will potentially suffer from narrow tiles towards the nose tip. So I'm interested in your double pentagon tile idea but I can't quite imagine them. Would these tiles have a some concave edges? And how would they link up with the hexagonal tiles? I note that the hex "grain" on starship runs around the circumference rather than vertically up the side. Any chance of a diagram?
Paraphrasing Elon in the Joe Rogan podcast:
You have to get the gaps just right, if it gets too big you get plasma in the crack (and that's bad) and if it's too small they are going to bang together.
If cm scale gaps were ok they would hardly be concerned about differential thermal expansion and vibrations. Sure, Starship would likely survive with big gaps or even missing tiles. The blankets are made from similar materials and could survive similar temperatures as the tiles (if not higher depending on composition) but turbulence, shock impingement and lower emissivity would lead to higher temperatures. The steel can get quite hot before failing but will start to anneal and lose the hardening at a significantly lower temperature - fine for survivability but likely instant scrapping if it happens in the tanks.
Also remember that re-entries from LEO, while being by far the most common case, represent the lower end of the performance envelope. I am really curious as to how far they can take the reusable tiles or whether they will need ablative solutions for high energy tankers or lunar/Mars returns.
Well perhaps fixation was the wrong word - I'm sorry. And I suspect that we don't even disagree. In fact I think everyone is in agreement that:
It would be handy if there was just one tile for the entire ship, but there won't be. Its no big deal its not the shuttle. There seems to be a fixation on the idea that there has to be just a handful of tile types. There doesn't.
There is a not a fixation, there are those of us with manufacturing engineering experience that know that "less parts is better". We "fixated" on having at most one type of fastener for an oscilloscope assembly (a specific example in my past).
The reasons are not just inventory management, though that is important, it's the ability of an operator to easily deal with more than one handful of parts at a time. It is difficult to have more than 5-10 types of parts on hand at a manufacturing station in a building while sitting and reaching for the parts, and even more difficult while 40 meters in the air on a lift. The more similar looking the parts, the lower the practical number, due to human cognition limitations.
Go ahead and work out the number of up/down lift movements, operator reaches, choice mistakes, at 40 meters in the air while dealing with 3 parts. Now do that for 30 parts. It'll be an order of magnitude more difficult for the 30 parts version.
Yes, I believe this is the best you can do without gaps on a compound curve.The problem with these designs (and with the original on page 1) is that each row of tiles requires a different shape. In these examples there are 4 rows and 4 or more tile types. The top row is not compatible with the bottom row as the hexagon side lengths are different.Behold the Diagrams! Quick and dirty with greatly exaggerated differences between rows - if one limits tiles to the same maximum dimensions then a doubling is only needed for every factor of 2 change in nose radius. The one I meant was the first one but the others are options if one wants to avoid the two tile long straight gap at the cost of a notched tile or a smaller insert diamond tile (which can be bigger at the cost of three instead of two types of tiles).I strongly believe that Starship will have "perfect tiling", i.e. there will be no intentional gaps beyond those required by thermal contraction/expansion, vibrations and placement tolerances. It is going to need more types of tiles but it should be on the order of a few hundred with a decent number of tiles for most of them. For the nose cone I am personally a fan of the tapered hexagons suggested on the first page of this thread, with each row being identical. My addition would be a doubling once the tiles get wide enough which would require a handful of rows to use two mirrored pentagonal tile types instead.The narrowing hexagon approach on page 1 shows promise but will potentially suffer from narrow tiles towards the nose tip. So I'm interested in your double pentagon tile idea but I can't quite imagine them. Would these tiles have a some concave edges? And how would they link up with the hexagonal tiles? I note that the hex "grain" on starship runs around the circumference rather than vertically up the side. Any chance of a diagram?
Paraphrasing Elon in the Joe Rogan podcast:
You have to get the gaps just right, if it gets too big you get plasma in the crack (and that's bad) and if it's too small they are going to bang together.
If cm scale gaps were ok they would hardly be concerned about differential thermal expansion and vibrations. Sure, Starship would likely survive with big gaps or even missing tiles. The blankets are made from similar materials and could survive similar temperatures as the tiles (if not higher depending on composition) but turbulence, shock impingement and lower emissivity would lead to higher temperatures. The steel can get quite hot before failing but will start to anneal and lose the hardening at a significantly lower temperature - fine for survivability but likely instant scrapping if it happens in the tanks.
Also remember that re-entries from LEO, while being by far the most common case, represent the lower end of the performance envelope. I am really curious as to how far they can take the reusable tiles or whether they will need ablative solutions for high energy tankers or lunar/Mars returns.
Here’s a re-drawn illustration that shows the geometric principle of a scheme that can double/halve the number of tiles in a circumferential band (imagine this on paper wrapped around a cone). This is directly comparable to schemes illustrated by other posters above, but the tile shapes are closer to hexagonal. Also, it’s cool and looks like 5-7 defects in graphene.I like this a lot. It is clearly repeatable; the "top" row becoming the bottom row of the next repeat of the same pattern.
Sorry I have not read all posts above.... but....
Everyone seems to be trying to cover the conical-ish nose as we see it, that is with horizontal (perpendicular to the long axis of the SS), meaning each band has a squeezed top in comparison to its bottom, and assuming one long horizontal seam is not allowed, gives rise to these beautiful, complex geometric designs.
However a cone is not a complex curve, and can be bent out of flat sheet! Therefore if it is tiled in rows of standard hexagons AS IF IT WERE STILL A FLAT SHEET then there should be no difficult gaps!
Unfortunately the nose is not a perfect cone, and much worse there is the transition from the cylinder, to the cone-ish, and the transition to the nose.
Leaving aside these issues, such a pattern would create a beautiful "bow up" on the belly of the nose, sweeping in a (seeming) smooth curve to the Elonerons!
That said I remain open minded to some solution being found. The most interesting so far is the Goldberg polyhedra concept. It works on a sphere with constant change in radius, but I don't think it works on a variable radius nose cone like Starship. Then again only half the ship needs tiling... Still trying to visualize this one.
It's important to remember that they have more flexibility than some of the purely geometric speculation allows for, because they're only goin half-way around. That gives them a lot of wiggle room at the (literal) edges, which can simplify things on the "belly".
How did they design the tiles for the Shuttle?Did they use some kind of algorithm?
Could be possible for SpaceX to code a program exploring a lot of possible tiling schems to find the best? Or is this a non automatable problem, that needs the human mind?
It's important to remember that they have more flexibility than some of the purely geometric speculation allows for, because they're only goin half-way around. That gives them a lot of wiggle room at the (literal) edges, which can simplify things on the "belly".
This doesn't make a difference here. Any area of non-zero curvature will not be tilable by constant shapes. All only having to deal with a portion of the curved area does is allow us to distort a flat tiling and not end up with singularities due to different topology. However, a distorted tiling means different types of tiles, so it's not going to solve our problem.
Yes, for a sphere you have the inherent symmetry of the base polyhedron around each of the original vertices. The problem is when you deform it into a ogive surface so that the symmetry is only preserved perpendicular to the rotational axis...This is the principle of the Goldberg polyhedra mentioned above (and geodesic domes which are their mathematical duals). The result will be very nice looking surfaces covered with almost regular polygons of similar sizes (can be chosen to be mostly hexagons with some pentagons and/or diamonds) - but each tile will more or less be unique.It can be quite a lot less than unique, e.g. 5 hexagon variants and one pentagon variant (http://dmccooey.com/polyhedra/DualGeodesicIcosahedron13.html). Even better, many of those variants have edge lengths within 1% of each other, so those 5 variants could be covered by 3 or maybe 2 variants depending on acceptable gap variance. But on top of that, you do not need to perfectly tile Starship, you only need a partial tiling, which means many of the problems encountered in perfect sphere tilings simply are not problems in the first place.
Seems like SX will be interested in flight data on this. What would the instrumentation look like? What I come up with is infrared imaging from inside the tank or maybe acoustic. Maybe both to check against each other. Anything else besides a ridiculously big array of thermocouples?I asked a question earlier about laminar flow velocity in relation to groove dimension and got no reply. There must be some spherical cow relationship for a starting point in figuring out what depth, width and angle relationships might introduce turbulence. I can't even figure out search terms to look this up without the search itself becoming a research project.The issue with the half tile pentagon is that it leaves "channels" running circumferentially around the starship. Folks have *claimed* that such unimpeded plasma paths would be Very Bad and so I think we've mostly avoided using them.
One of those "folks" is Elon himself.
Given that SpaceX are undisputed experts at Computational Fluid Dynamics (CFD) simulations, I'm inclined to believe him.
There should be some empirical rules of thumb, but understanding the transition between laminar and turbulent flow in general is literally one of the most important open problems in mechanics.
Maybe variable gaps would be a good thing for a first flight. Get some data on limits.There are 5 shapes shown -- each all-hexagon band has a single, bilaterally symmetric tile shape.Here’s a re-drawn illustration that shows the geometric principle of a scheme that can double/halve the number of tiles in a circumferential band (imagine this on paper wrapped around a cone). This is directly comparable to schemes illustrated by other posters above, but the tile shapes are closer to hexagonal. Also, it’s cool and looks like 5-7 defects in graphene.It would help if you labeled each tile size/shape - think I count 7?
BTW, the role of the illustrated pattern is the same as the role of the patterns in eriblo’s diagrams here (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2250067#msg2250067). The number of shapes required for a whole nosecone depends less on the doubling/halving bands than it does on the tolerance for gap variations in the more numerous bands of tapered hexagons. Hexagon shapes can be reused if gaps are allowed to vary a bit, but perfect tiling requires one shape per row.
Why not use a rotational hexagonal pattern for the nose heatshield? I’ve seen somewhere a render that used this pattern
Edit: added render
Why not use a rotational hexagonal pattern for the nose heatshield? I’ve seen somewhere a render that used this pattern
Edit: added render
It leaves no space between tiles but leaves rough edges that would need a different type of tiles
How did they design the tiles for the Shuttle?Did they use some kind of algorithm?
Could be possible for SpaceX to code a program exploring a lot of possible tiling schems to find the best? Or is this a non automatable problem, that needs the human mind?
This is a very much automatable problem. We're looking at the field of "geometry processing" and "geometric design". I have seen several papers in this field that look at the problem of covering a freeform shape (the nosecone here, but these works have architecture in mind) with flat panel of as few as possible different types. If time permits, I'll try to dig these papers and put links here. (maybe google for 'computational architecture').
[...]
I'd really appreciate the links if you can dig them up. I found this yesterday:
https://www.researchgate.net/publication/227280537_A_Note_on_Planar_Hexagonal_Meshes
Which goes over several ways to create hex tilings. It boils down to an optimization problem, and the optimizer could be given "identical tile shapes" as a goal.
[...]
More to the point, that is just a CGI texture map; it ignores physical constraints. See this section here for example, where you can see a number of implausible tile boundaries.
The more detailed renders are mostly examples of the approach mentioned earlier - wrap the nose cone in a shape with simple curvature (in this case likely a cone) and adjust each point to the correct surface. This is a standard graphics texture approach and produces very nice looking tiling - but each of those tiles are likely unique. No problem for computers but complicated in real life...More to the point, that is just a CGI texture map; it ignores physical constraints. See this section here for example, where you can see a number of implausible tile boundaries.
I’m only addressing the tiling of a double curvature surface, the flap-body interface is another problem.
Also, I haven’t said it before but this pattern is asymmetric. I don’t know if that messes up the aerodynamics
I'd really appreciate the links if you can dig them up. I found this yesterday:I think that for the first flights they will go with the "same latitude same tile " approach, because there won't be crewed flights for a while. They will gain experience and I'm confidente they will be able to point out if it is better to change approach and how much spare tiles to bring in orbit.
https://www.researchgate.net/publication/227280537_A_Note_on_Planar_Hexagonal_Meshes
Which goes over several ways to create hex tilings. It boils down to an optimization problem, and the optimizer could be given "identical tile shapes" as a goal.
Personally I'm optimistic that a mixture of hexes and regular pentagons with the same edge length *could* do the job.
But the neglected issue here is automation and that robot stud welder. So far we've seen regular grids. It may be that SpaceX "optimizes for manufacturability" here by using one tile shape per "latitude" (cf the first post in this thread) because it allows the stud attachment points to be on a regular grid, even if the tile shapes are different. The metal attachment brackets could also be substantially the same for every tile. OTOH that makes tile manufacturing more involved, with about 30 different tile shapes to juggle. And as folks have noted, the tile sizes probably need to shrink at the tip of the nose, so you're going to have variations in your attachment grid in any case.
Seems we have only seen 4 tile types so far. The cut end hexagons (assumed to be for the base of Starship) and three sizes of hexagon. I was wondering why they need three sizes of hexagons and how these could be incorporated into the page one scheme.
Perhaps they are necessary to reduce the length of the tiles to help prevent them getting excessively narrow towards the nose tip. This could also make successive tile layers smaller to help cope with increased curvature.
There still needs to be one type of tile per nose layer, but the 3 hexagonal ones we have seen may be the 3 basic sizes they use. All the others are simply cut down on two sides.
There still needs to be one type of tile per nose layer, but the 3 hexagonal ones we have seen may be the 3 basic sizes they use. All the others are simply cut down on two sides.
I guess a really important question about different tile shapes is what's involved in manufacturing the varients. It they each need seperate molds, etc, then managing a large number of tile types will not be fun. On the other hand, if they can start with a handful of different types of blanks (needed for large/small tiles where you might have to have the attachment points closer or further apart), and then for a specific tile, just put the correct size blank in the CNC and set it to grind the blank into the specific shape you need, things will be far easier.
Presumably would be a couple steps post CNC involving coating layers, but you're still looking at cutting the "Bad news: Bill accidentally dropped the entire palette of pattern 72 tiles while lifting them, and, needless to say, we don't have enough spares to cover that. We need replacments ASAP" delay to a very quick program change on the CNC and some amount of post processing, followed by overnight shipping, as opposed to a lengthy lay-up starting from scratch.
The discussion here is too focused on hexagonality, when probably straight gaps between rows of the tiles is not the issue anymore as we saw them on SN15-16.Spoilsport. Allowing rows of trapezoids makes it too easy.
The discussion here is too focused on hexagonality, when probably straight gaps between rows of the tiles is not the issue anymore as we saw them on SN15-16.
Some observations and a first-flight speculation:
1) General objective: Test atmospheric entry.
2) Specific objective: Test tile attachment, robustness, aerodynamics, effectiveness.
3) Problem: Tiling the nose looks like a pain, and prototype attachment (etc.) systems may be replaced.
4) Solution: For initial flights, slap a layer of ablative TPS material on the nose (could be a spray-on, heavy is OK), test tiles on cylindrical surfaces, later adapt a successful design to the nose geometry.
Occam's razor really suggests the straight line latitude strips. That matches the "home plate" pentagons we've already seen mounted, requires no changes to mounting stud pattern, etc. A custom gap filler of some sort at intervals is probably sufficient to break up the flow along the latitude lines, if that is indeed a problem.Have we seen any pentagonal tiles on any SN?
But it's much much more fun to consider the soccer-ball or crystallographic tilings. :)
Really, we should be worried about tiling the flap-to-body interface and the flap leading edges.
There are “half hexagons” that look like standard tiles truncated to line up with the edge of a skirt: Technically pentagons, but not useful for a 5-6-7 scheme. I’ve seen no tiles that seem suitable for fitting double-curved surfaces. This makes me think that the initial orbital flights might use a quick-and-dirty ablative material on the nose while validating tile attachment (etc.) on the body where they’re easier to apply.Occam's razor really suggests the straight line latitude strips. That matches the "home plate" pentagons we've already seen mounted, requires no changes to mounting stud pattern, etc. A custom gap filler of some sort at intervals is probably sufficient to break up the flow along the latitude lines, if that is indeed a problem.Have we seen any pentagonal tiles on any SN?
But it's much much more fun to consider the soccer-ball or crystallographic tilings. :)
Really, we should be worried about tiling the flap-to-body interface and the flap leading edges.
Might it not be easier to consider the way to vary the shape of the tiles is that they are curved rather than many different size/number of sides?Making the tiles curved (curved to more accurately fit the nosecone) might help make the structure smoother which might help with reentry but at the cost of making the tile manufacture more complex and expensive. However it would not really effect the number of tiles required or the number of sides they would have as the tiles would still need to tesselate across the surface of the nosecone.
Would this reduce the number of variants required?
That is a standardised 'curved' tile for the nose section?
IMO they will try to build a complete heat shield for the entire vehicle. They will then iteratively refine that heat shield until they can get Starship down into the ocean in one piece. After that when they can get it back to Boca Chica or a platform further refinements should be easier as they will be able to examine it.It doesn’t look like NC18 has studs for the heat shield tiles, so maybe it’s just another orphan destined for the scrap yard?Or early expendable and single-use orbital prototypes may use an ablative TPS material on the nose. This would allow testing of tile systems where the geometry is easy (cylindrical surfaces) and postpone the difficulties of tiling double-curved geometries (which require multiple tile shapes) until risks associated with attachment, robustness, aerodynamics, and effectiveness have been retired.
🤔
It's probably a bad assumption to say they can just slap on a proven heatshield tecnology to Starship's nose without much effort. First, there's still quite a bit of developing and tooling involved in making the material into the new shape, but, more importantly, there are various reasons that such a heatshield could fail. Adhesives could burn under the hot body/ thin heat shield design of Starship. If they make the shield thicker to compensate, it won't match the tiled section, and the discontinuity will cause all sorts of exciting shockwave impringement problems, making very hot spots. Indeed, just the nature of a ablative heatshield compared to the tiles could easily result in such a discontinuity all on its own.
There is a separate thread for the heatshield
https://forum.nasaspaceflight.com/index.php?topic=50748.1520
(https://forum.nasaspaceflight.com/index.php?topic=50748.1520)
Might it not be easier to consider the way to vary the shape of the tiles is that they are curved rather than many different size/number of sides?Making the tiles curved (curved to more accurately fit the nosecone) might help make the structure smoother which might help with reentry but at the cost of making the tile manufacture more complex and expensive. However it would not really effect the number of tiles required or the number of sides they would have as the tiles would still need to tesselate across the surface of the nosecone.
Would this reduce the number of variants required?
That is a standardised 'curved' tile for the nose section?
I do not think it will.Might it not be easier to consider the way to vary the shape of the tiles is that they are curved rather than many different size/number of sides?Making the tiles curved (curved to more accurately fit the nosecone) might help make the structure smoother which might help with reentry but at the cost of making the tile manufacture more complex and expensive. However it would not really effect the number of tiles required or the number of sides they would have as the tiles would still need to tesselate across the surface of the nosecone.
Would this reduce the number of variants required?
That is a standardised 'curved' tile for the nose section?
I wasn't really expecting it would reduce either then number of tiles or the number of sides the tiles would have.
I was thinking it could possibly reduce the number of different tile shapes required...
Just throwing it out there.. if you really want to cover a doubly curved surface with just one tile shape.. you could go with scale mail 8)The comment of your second link seems to assume that the tiles would be different... as in the dome at the end
https://en.wikipedia.org/wiki/Scale_armour
Or..
https://discourse.mcneel.com/t/paneling-double-curved-surface-roof-tiles/82634
I will let myself out..
Heat Tiles: SN8-SN16
It is also possible they will rethink the exact curvature of their nose cone to minimize tiling complexity. There may be a tradeoff between easy nose cone shape in stainless steel versus minimum number of tile shapes to cover the nose cone.I’m pretty sure that all ogives are about the same w.r.t. the curvature problem, in other words, that there’s little to be gained by fine-tuning the shape.
Continuing to refine an idea that may or may not have net merit compared to other options:The trouble is the sequences of multiple hexagons will not match the 3D surface. Also we have only seen hexagonal tiles of various sizes being tested.
Covering a double-curved surface with well-fitted arrays of tiles is non-trivial, and the main systematic approaches discussed here have either varied tile shapes for each “latitude band” (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2251117#msg2251117) or (less explored to above) found a way to taper “longitude gores” (bands and gores are illustrated below).
If hexagon-like patterns are worth pursuing (avoiding aligned grooves, looking pretty, etc.), and the number of tile-shapes should be sharply limited, then the longitude-gore scheme below looks pretty good. In particular, there is no problem with tiles tending to narrow towards the tip and requiring doubling-bands to compensate. This scheme does require special design methods to do well (see below), and requires flexible programming of mounting-pin placement.
I present this scheme and diagram for consideration by people who can make sense of 2D --> 3D diagrams, and can imagine the effect of playing with the distribution of curvature-enabling 5-7 tile pairs.
Note that the nosecone taper can vary arbitrarily, and small variations in the spacing of identical hexagons can accommodate residual curvature between clusters containing 5-7 tile pairs and a few distorted near-neighbor hexagons. Shapes adjacent to the tip-cap and flaps are special cases in any scheme.
Design method:
• Parametric definition of 5, 7, and a few kinds of 6 sided tile shapes.
• Distance and orientation of tiles constrained to the nosecone surface.
• Use elastic restraints between adjacent tile edges to distribute gaps.
• Fiddle 5-7 positions and tile shapes to fit the surface nicely.
(No, we probably won’t see this, but it’s cool.)
[Edit: Unless the gap-to-tile ratio is increased (same gap, smaller tiles) the conditions for small numbers of tiles seem too stringent for this scheme. I’d vote to deal with aligned grooves and use trapezoids, which can fit better than these (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2240019#msg2240019).]
The trouble is the sequences of multiple hexagons will not match the 3D surface. Also we have only seen hexagonal tiles of various sizes being tested.Think of areas of regular hexagons as flexible sheets that can be stretched only slightly (like paper). Stretching = varying gap sizes. Split the nosecone into gores and cover it like a globe (often made by wrapping paper gores around a sphere). The problems are at the seams where the regular hexagonal grids collide. At those seams, colliding grids can be trimmed to leave gaps that can be filled with tastefully arranged 5-7 pairs and distorted hexagons. This actually works, with enough tiles, and maybe not too many.
How about a cylinder where the nose is a diagonal slice. :)It is also possible they will rethink the exact curvature of their nose cone to minimize tiling complexity. There may be a tradeoff between easy nose cone shape in stainless steel versus minimum number of tile shapes to cover the nose cone.I’m pretty sure that all ogives are about the same w.r.t. the curvature problem, in other words, that there’s little to be gained by fine-tuning the shape.
Vostok would like to have a word...How about a cylinder where the nose is a diagonal slice. :)It is also possible they will rethink the exact curvature of their nose cone to minimize tiling complexity. There may be a tradeoff between easy nose cone shape in stainless steel versus minimum number of tile shapes to cover the nose cone.I’m pretty sure that all ogives are about the same w.r.t. the curvature problem, in other words, that there’s little to be gained by fine-tuning the shape.
I can think of some variations not quite that bad, but also keeping the windward side a cylindrical section.
I still wonder (as a layman, and ignoring the fact they have no doubt simulated this over and over) if this is really the final hull shape. Even a small lip, I would have thought, would push the plasma stream away from the sides. Every other reentry shape I am aware of has gone with a flatter bottom.
Vostok would like to have a word...Interesting! (but the exception proves the rule)
How about a cylinder where the nose is a diagonal slice. :)It is also possible they will rethink the exact curvature of their nose cone to minimize tiling complexity. There may be a tradeoff between easy nose cone shape in stainless steel versus minimum number of tile shapes to cover the nose cone.I’m pretty sure that all ogives are about the same w.r.t. the curvature problem, in other words, that there’s little to be gained by fine-tuning the shape.
I can think of some variations not quite that bad, but also keeping the windward side a cylindrical section.
I still wonder (as a layman, and ignoring the fact they have no doubt simulated this over and over) if this is really the final hull shape. Even a small lip, I would have thought, would push the plasma stream away from the sides. Every other reentry shape I am aware of has gone with a flatter bottom.
or how about a cone for the nose cone and then a diagonal slice of the cone.Cones are more easily tiled, but a full cone would sacrifice volume. I’m not picturing the diagonal slice, but a flat surface would sacrifice structural efficiency. SpaceX seems committed to ogives.
Yes minimising the number of tiles is useful but secondary to other issues of finding the best geometry to cope with reentry and hypersonic flight.or how about a cone for the nose cone and then a diagonal slice of the cone.Cones are more easily tiled, but a full cone would sacrifice volume. I’m not picturing the diagonal slice, but a flat surface would sacrifice structural efficiency. SpaceX seems committed to ogives.
Exactly - and an arbitrary ogive is only ~10% of the total number of tile types unless they really optimize the fin fairings (especially the forward ones). Even the simple flat fins might add a similar or larger number of tile types unless they are optimized (which should be much more forgiving aerodynamically). Added a standard tile tiling to Rafael's SN8 fin estimates - as can be seen an optimal combination of orientation and edge angles might have ~15 tile types per fin while an arbitrary choice can easily double or triple the number.Yes minimising the number of tiles is useful but secondary to other issues of finding the best geometry to cope with reentry and hypersonic flight.or how about a cone for the nose cone and then a diagonal slice of the cone.Cones are more easily tiled, but a full cone would sacrifice volume. I’m not picturing the diagonal slice, but a flat surface would sacrifice structural efficiency. SpaceX seems committed to ogives.
Yes minimising the number of tiles is useful but secondary to other issues of finding the best geometry to cope with reentry and hypersonic flight.or how about a cone for the nose cone and then a diagonal slice of the cone.Cones are more easily tiled, but a full cone would sacrifice volume. I’m not picturing the diagonal slice, but a flat surface would sacrifice structural efficiency. SpaceX seems committed to ogives.
You have your priorities right.Yes minimising the number of tiles is useful but secondary to other issues of finding the best geometry to cope with reentry and hypersonic flight.or how about a cone for the nose cone and then a diagonal slice of the cone.Cones are more easily tiled, but a full cone would sacrifice volume. I’m not picturing the diagonal slice, but a flat surface would sacrifice structural efficiency. SpaceX seems committed to ogives.
"You literally told them to make the Starship more pointy because of the movie 'The Dictator?'" a chuckling Rogan asked.
"Yep. And they know it, too," Musk replied with a laugh. "It's not like they're unaware of it. I thought it would be funny to make it more pointy, so we did.
"Rogan then asked if pointiness gives Starship an aerodynamic edge. "It's arguably slightly worse," Musk said, spurring laughter from both men. But, he added, "it looks cooler."
Are we sure that this possible new nose cone design won't affect payload mass distribution and aerodinamics during launch?That is possible.. ;)
Just stepping back a bit....I think its an assumption. But if they don't use tiles what else is there that meets their requirements? And if they did have a material X that meets those requirements and is good for the nose, then why not use that across the whole ship instead of tiles?
Why are we convinced they are going to be using tiles on the nose?
Just stepping back a bit....
Why are we convinced they are going to be using tiles on the nose?
Just stepping back a bit....I think its an assumption. But if they don't use tiles what else is there that meets their requirements? And if they did have a material X that meets those requirements and is good for the nose, then why not use that across the whole ship instead of tiles?
Why are we convinced they are going to be using tiles on the nose?
Because both TUFROC and carbon-carbon are much heavier than Silicon tiles.Shuttle used carbon-carbon at leading edges and nose, and X-37B uses TUFROC is same purpose. Maybe we see long rumored TUFROCX at SS nose and bodyflaps...Is there a limit on the size and shape of the tile? Is there a reason they can't make a single piece, to cover the entire nose cone?
tiles are quite fragile, so big size are worse for vibration, and in case of damage you can't repair only one tile.
Still are we sure that transpiration cooling is really more efficient per W/m^2 of kg of taken payload pen?I don't think that is being debated. SpaceX has explicitly said that it turned out heavier, when they changed their decision away from transpiration to tiles. (sorry could not find reference)
Still are we sure that transpiration cooling is really more efficient per W/m^2 of kg of taken payload pen?I don't think that is being debated. SpaceX has explicitly said that it turned out heavier, when they changed their decision away from transpiration to tiles. (sorry could not find reference)
Elon Musk said they could use it in spots where heating was a problem. It seems unlikely that they would use it on a wide area just to avoid different tile shapes.. but who knows. What if the work of maintaining tiles in tricky spots was just such a bother that they did put up with a more massive solution for a smallish fraction of the hull. I keep hearing it is more about price than weight.
https://twitter.com/elonmusk/status/1107380559834046465?lang=en
Exactly - and an arbitrary ogive is only ~10% of the total number of tile types unless they really optimize the fin fairings (especially the forward ones). Even the simple flat fins might add a similar or larger number of tile types unless they are optimized (which should be much more forgiving aerodynamically). Added a standard tile tiling to Rafael's SN8 fin estimates - as can be seen an optimal combination of orientation and edge angles might have ~15 tile types per fin while an arbitrary choice can easily double or triple the number.Yes minimising the number of tiles is useful but secondary to other issues of finding the best geometry to cope with reentry and hypersonic flight.or how about a cone for the nose cone and then a diagonal slice of the cone.Cones are more easily tiled, but a full cone would sacrifice volume. I’m not picturing the diagonal slice, but a flat surface would sacrifice structural efficiency. SpaceX seems committed to ogives.
https://youtu.be/FlYKVpOVrcMQuoteScheduled for 19 Jun 2021
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In this week's episode, NASASpaceflight's John "Das" Galloway and Chris Gebhardt will speak with Jean Wright, a worker on the Space Shuttle's Thermal Protection Systems (TPS).
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but as long as cutting them doesn't harm their performance, you can bulk manufacture the standard type.Aby cutting must occur before the RCG stage, or the sides will be left uncoated.
but as long as cutting them doesn't harm their performance, you can bulk manufacture the standard type.Aby cutting must occur before the RCG stage, or the sides will be left uncoated.
The problem is not so much manufacture of the tiles themselves (that's an almost arbitrary choice of shape). It's the logistics of handling thousands of unique tiles rather than thousands of identical tiles. You can't just manufacture 10k 'Starship tiles', ship them by the pallet, and install them in the order you pick them up out of the crate. At the extreme, each is a unique shape and you must ensure that unique tile makes its way from manufacture to installation without being damaged, misplaced, installed one stud over, etc. If that happens, you then need to manufacture another unique tile (or manufacture at least two of every unique tile to start with, and have near 50% overhead).
Until someone drops/chips/etc that second unique tile, and now an entire vehicle is waiting on the total lead time for a new tile to be manufactured and shipped, rather than on the lead-time for someone to grab the next tile in the pile.but as long as cutting them doesn't harm their performance, you can bulk manufacture the standard type.Aby cutting must occur before the RCG stage, or the sides will be left uncoated.
The problem is not so much manufacture of the tiles themselves (that's an almost arbitrary choice of shape). It's the logistics of handling thousands of unique tiles rather than thousands of identical tiles. You can't just manufacture 10k 'Starship tiles', ship them by the pallet, and install them in the order you pick them up out of the crate. At the extreme, each is a unique shape and you must ensure that unique tile makes its way from manufacture to installation without being damaged, misplaced, installed one stud over, etc. If that happens, you then need to manufacture another unique tile (or manufacture at least two of every unique tile to start with, and have near 50% overhead).
There is no overhead here. Unused ‘spare’ tiles are simply part of the stock for future builds.
I'm reminded of a segment of Eric Berger's book, Liftoff, where Falcon 1 testing is cut short by LOX shortage often enough that Elon throws out dire threats if there is ever a shortage again.Until someone drops/chips/etc that second unique tile, and now an entire vehicle is waiting on the total lead time for a new tile to be manufactured and shipped, rather than on the lead-time for someone to grab the next tile in the pile.but as long as cutting them doesn't harm their performance, you can bulk manufacture the standard type.Aby cutting must occur before the RCG stage, or the sides will be left uncoated.
The problem is not so much manufacture of the tiles themselves (that's an almost arbitrary choice of shape). It's the logistics of handling thousands of unique tiles rather than thousands of identical tiles. You can't just manufacture 10k 'Starship tiles', ship them by the pallet, and install them in the order you pick them up out of the crate. At the extreme, each is a unique shape and you must ensure that unique tile makes its way from manufacture to installation without being damaged, misplaced, installed one stud over, etc. If that happens, you then need to manufacture another unique tile (or manufacture at least two of every unique tile to start with, and have near 50% overhead).
There is no overhead here. Unused ‘spare’ tiles are simply part of the stock for future builds.
To be honest, I have a hard time imagining how a few dozen extra tile shapes could be more difficult to deal with than a complicated cooling manifold supplying methane over a large curved surface. We're talking about different shaped tiles for each row up the nose, not every single tile custom like in the Shuttle. Also, the Shuttle had the additional rather big problem of having to carefully chisel out the old tile, since they couldn't be detached otherwise, with enough precision to fit the replacement tile with hair's breadth gaps.It was just an offhand thought that perhaps these tiles might prove similarly time consuming to the shuttle.. or only 10x easier instead of the 100x or 1000x we need.. but the problem gets solved by some brilliant, practically AI refurbishment tool that slides up the cylindrical portion of the starship in an hour or so, intensely inspecting each tile and replacing if necessary.
Keeping the unique tile count down is a good thing. One shape would be great but reality intrudes. What number are we looking at? Twenty? 50? 150? My uninformed guess is somewhere between 100 and 150, plus some monolithic pieces around the nose and fin edges. Keeping track of it all, from manufacture to installation, is an issue, but this is a known and well exercised process.but as long as cutting them doesn't harm their performance, you can bulk manufacture the standard type.Aby cutting must occur before the RCG stage, or the sides will be left uncoated.
The problem is not so much manufacture of the tiles themselves (that's an almost arbitrary choice of shape). It's the logistics of handling thousands of unique tiles rather than thousands of identical tiles. You can't just manufacture 10k 'Starship tiles', ship them by the pallet, and install them in the order you pick them up out of the crate. At the extreme, each is a unique shape and you must ensure that unique tile makes its way from manufacture to installation without being damaged, misplaced, installed one stud over, etc. If that happens, you then need to manufacture another unique tile (or manufacture at least two of every unique tile to start with, and have near 50% overhead).
With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?I'm reminded of a segment of Eric Berger's book, Liftoff, where Falcon 1 testing is cut short by LOX shortage often enough that Elon throws out dire threats if there is ever a shortage again.Until someone drops/chips/etc that second unique tile, and now an entire vehicle is waiting on the total lead time for a new tile to be manufactured and shipped, rather than on the lead-time for someone to grab the next tile in the pile.but as long as cutting them doesn't harm their performance, you can bulk manufacture the standard type.Aby cutting must occur before the RCG stage, or the sides will be left uncoated.
The problem is not so much manufacture of the tiles themselves (that's an almost arbitrary choice of shape). It's the logistics of handling thousands of unique tiles rather than thousands of identical tiles. You can't just manufacture 10k 'Starship tiles', ship them by the pallet, and install them in the order you pick them up out of the crate. At the extreme, each is a unique shape and you must ensure that unique tile makes its way from manufacture to installation without being damaged, misplaced, installed one stud over, etc. If that happens, you then need to manufacture another unique tile (or manufacture at least two of every unique tile to start with, and have near 50% overhead).
There is no overhead here. Unused ‘spare’ tiles are simply part of the stock for future builds.
It seems like the solution here is to create a batch of, say, 50 of each "unique" tile, and after 30-40 are used, review the stock and decide if you need to run up another batch.
Top priority is successful EDL. Second priority is making it inexpensive.
1 | Minimize Part Count
Reducing the number of parts in a product is the quickest way to reduce cost because you are reducing the amount of material required, the amount of engineering, production, labor, all the way down to shipping costs.
2 | Standaradize Parts and Materials
Personalization and customization are expensive and time-consuming. Using quality standardized parts can shorten time to production as such parts are typically available and you can be more certain of their consistency.
That's all well and good, but the unequivocal top priority for the heat shield is still to make EDL survivable. Without a functional heat shield, it really doesn't matter how manufacturable the whole spacecraft it is. If this ends up needing 150 unique tile shapes, so be it.Top priority is successful EDL. Second priority is making it inexpensive.
Top priority is designing the machine that designs the machine. That is ten times harder than the actual item that is being built.
It would be helpful to do some reading on Design For Manufacturability. Those proposing 10s or 100s of types of tiles are violating the first principle of DFM:Quote1 | Minimize Part Count
Reducing the number of parts in a product is the quickest way to reduce cost because you are reducing the amount of material required, the amount of engineering, production, labor, all the way down to shipping costs.
As well as the second:Quote2 | Standaradize Parts and Materials
Personalization and customization are expensive and time-consuming. Using quality standardized parts can shorten time to production as such parts are typically available and you can be more certain of their consistency.
https://news.ewmfg.com/blog/manufacturing/dfm-design-for-manufacturing
That's all well and good, but the unequivocal top priority for the heat shield is still to make EDL survivable. Without a functional heat shield, it really doesn't matter how manufacturable the whole spacecraft it is. If this ends up needing 150 unique tile shapes, so be it.
While some may argue that SS could be a commercially successful super heavy lift LV even flying expendable, that misses the point. "Colonize Mars" is the reason SpaceX exists, and for that EDL is non-negotiable.
Obviously it must be manufacturable and it must survive EDL. I don't think anyone is saying it must survive on the first try, nor did I mean to imply anything about what gets optimized when. While I think I see the points your making, there can be a big difference between "manufacturable" and "optimally manufacturable". They could tile the thing with 5,000 unique shapes and it wouldn't be un-buildable, it would just be an expensive pain in the backside. I suspect both parameters here will have room for further optimization after the first craft survives.
That's all well and good, but the unequivocal top priority for the heat shield is still to make EDL survivable. Without a functional heat shield, it really doesn't matter how manufacturable the whole spacecraft it is. If this ends up needing 150 unique tile shapes, so be it.
While some may argue that SS could be a commercially successful super heavy lift LV even flying expendable, that misses the point. "Colonize Mars" is the reason SpaceX exists, and for that EDL is non-negotiable.
Confusing with 'it must survive EDL the first time" with "it must survive EDL after 10-15 iterations" leads to neglect of manufacturability. In software engineering we call this "premature optimization of a non-primary metric".
SpaceX, if they follow prior work, will make it "probably good enough on the CFD simulation" and as simple as possible, and iterate from there. My guess is 10 Starships burn up before success. (i.e. twice as many prototypes as the flip n burn)
"we can't manufacture it" is worse than "it doesn't survive EDL", because the first problem prevents you from iterating to fix the second problem.
The problem faced is the nature of geometry itself not a desire to violate the first principles of DFM. I don't think anyone is in any doubt that ideally there would be just one type of tile. Yet we have already seen SpaceX deviate from the first principles of DFM by using multiple tile sizes. I would be interested to know how you think the tiles should be arranged on Starship?Top priority is successful EDL. Second priority is making it inexpensive.
Top priority is designing the machine that designs the machine. That is ten times harder than the actual item that is being built.
It would be helpful to do some reading on Design For Manufacturability. Those proposing 10s or 100s of types of tiles are violating the first principle of DFM:Quote1 | Minimize Part Count
Reducing the number of parts in a product is the quickest way to reduce cost because you are reducing the amount of material required, the amount of engineering, production, labor, all the way down to shipping costs.
As well as the second:Quote2 | Standaradize Parts and Materials
Personalization and customization are expensive and time-consuming. Using quality standardized parts can shorten time to production as such parts are typically available and you can be more certain of their consistency.
https://news.ewmfg.com/blog/manufacturing/dfm-design-for-manufacturing
Someone already demonstrated how SpaceX's 3 tile sizes could be used to tile a nosecone. y'all complained about gaps, without ever proving that the gaps in question were showstoppers. Y'all have since used gap-gate to justify throwing out all evidence of SpaceX's solution in favor of geometicly perfect shields with hundreds of specialized tiles.The problem faced is the nature of geometry itself not a desire to violate the first principles of DFM. I don't think anyone is in any doubt that ideally there would be just one type of tile. Yet we have already seen SpaceX deviate from the first principles of DFM by using multiple tile sizes. I would be interested to know how you think the tiles should be arranged on Starship?Top priority is successful EDL. Second priority is making it inexpensive.
Top priority is designing the machine that designs the machine. That is ten times harder than the actual item that is being built.
It would be helpful to do some reading on Design For Manufacturability. Those proposing 10s or 100s of types of tiles are violating the first principle of DFM:Quote1 | Minimize Part Count
Reducing the number of parts in a product is the quickest way to reduce cost because you are reducing the amount of material required, the amount of engineering, production, labor, all the way down to shipping costs.
As well as the second:Quote2 | Standaradize Parts and Materials
Personalization and customization are expensive and time-consuming. Using quality standardized parts can shorten time to production as such parts are typically available and you can be more certain of their consistency.
https://news.ewmfg.com/blog/manufacturing/dfm-design-for-manufacturing
With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
Well that is a fair point. If they can accept gaps then they must have considered just using one type of tile... but presumably that was a step too far (gaps too big) and SpaceX have settled on 3 types of tile for the majority of the surfaces in order to optimise the number of tiles v size of the gaps trade. We should see with SN20 if they have settled for a neat many tiled approach or a slightly disordered 3 tile approach.Someone already demonstrated how SpaceX's 3 tile sizes could be used to tile a nosecone. y'all complained about gaps, without ever proving that the gaps in question were showstoppers. Y'all have since used gap-gate to justify throwing out all evidence of SpaceX's solution in favor of geometicly perfect shields with hundreds of specialized tiles.The problem faced is the nature of geometry itself not a desire to violate the first principles of DFM. I don't think anyone is in any doubt that ideally there would be just one type of tile. Yet we have already seen SpaceX deviate from the first principles of DFM by using multiple tile sizes. I would be interested to know how you think the tiles should be arranged on Starship?Top priority is successful EDL. Second priority is making it inexpensive.
Top priority is designing the machine that designs the machine. That is ten times harder than the actual item that is being built.
It would be helpful to do some reading on Design For Manufacturability. Those proposing 10s or 100s of types of tiles are violating the first principle of DFM:Quote1 | Minimize Part Count
Reducing the number of parts in a product is the quickest way to reduce cost because you are reducing the amount of material required, the amount of engineering, production, labor, all the way down to shipping costs.
As well as the second:Quote2 | Standaradize Parts and Materials
Personalization and customization are expensive and time-consuming. Using quality standardized parts can shorten time to production as such parts are typically available and you can be more certain of their consistency.
https://news.ewmfg.com/blog/manufacturing/dfm-design-for-manufacturing
At this point, we pretty much know what SN20's shield will look like. (unless SN20 goes shieldless, just to see how far it gets...). It might or might not work, not even spaceX knows. And SpaceX will iterate from there... probably with a 4th tile shape specifically for the single biggest repeating gap in the existing pattern, keyhole shaped.
(https://forum.nasaspaceflight.com/assets/50748.0/2011621.jpg)
They could tile the thing with 5,000 unique shapes and it wouldn't be un-buildable, it would just be an expensive pain in the backside. I suspect both parameters here will have room for further optimization after the first craft survives.
they don't need to be attached by hand. Just look to electronics manufacturing. A scaled up pick and place machine could attach tiles very quickly.They could tile the thing with 5,000 unique shapes and it wouldn't be un-buildable, it would just be an expensive pain in the backside. I suspect both parameters here will have room for further optimization after the first craft survives.
No, they could not be successful with 5,000 unique shapes because it would take far too long to place them, and they would then not be able to iterate quickly enough.
Iteration speed is proportional to manufacturing speed and iteration speed is everything in a program like this.
they don't need to be attached by hand. Just look to electronics manufacturing. A scaled up pick and place machine could attach tiles very quickly.They could tile the thing with 5,000 unique shapes and it wouldn't be un-buildable, it would just be an expensive pain in the backside. I suspect both parameters here will have room for further optimization after the first craft survives.
No, they could not be successful with 5,000 unique shapes because it would take far too long to place them, and they would then not be able to iterate quickly enough.
Iteration speed is proportional to manufacturing speed and iteration speed is everything in a program like this.
OK, 5000 was perhaps slightly exaggerated, but I stand by my point. I also think I hear what you're saying, and don't necessarily disagree, but I think we're talking about somewhat different stages in the whole process, and I think we're also somewhat out of sync semantically speaking. I'm pretty sure if we were discussing this over a beer, we'd agree on a lot more than not. In any case, I believe they will start with the simplest, most manufacturable design they think they can get away with that also has at least a chance of surviving EDL. Even though the first few tries will almost certainly crash and burn (or more correctly, burn then crash), they will not go launching a bunch of prototypes that they know are doomed to certain failure just because they are easier to build.They could tile the thing with 5,000 unique shapes and it wouldn't be un-buildable, it would just be an expensive pain in the backside. I suspect both parameters here will have room for further optimization after the first craft survives.
No, they could not be successful with 5,000 unique shapes because it would take far too long to place them, and they would then not be able to iterate quickly enough.
Iteration speed is proportional to manufacturing speed and iteration speed is everything in a program like this.
Cdebuhr was just grabbing a number at he extreme to make a point. The engineering works but the economics suck.They could tile the thing with 5,000 unique shapes and it wouldn't be un-buildable, it would just be an expensive pain in the backside. I suspect both parameters here will have room for further optimization after the first craft survives.
No, they could not be successful with 5,000 unique shapes because it would take far too long to place them, and they would then not be able to iterate quickly enough.
Iteration speed is proportional to manufacturing speed and iteration speed is everything in a program like this.
I dont know either, but recall that they seriously looked at deleting the heat shield entirely and rely just on the thermal mass of the steel. They dont need a whole lot of thermal protection, IIRC just enough to drop the peak heating by a sixth or so, below a thousand degrees.
The point was made that until we know what gaps are acceptable, we don't have a clue about tile layout. My methane producing gut says that Rakaydos's pattern is too open but what do I know.
I dont know either, but recall that they seriously looked at deleting the heat shield entirely and rely just on the thermal mass of the steel. They dont need a whole lot of thermal protection, IIRC just enough to drop the peak heating by a sixth or so, below a thousand degrees.
The point was made that until we know what gaps are acceptable, we don't have a clue about tile layout. My methane producing gut says that Rakaydos's pattern is too open but what do I know.
They also have a history of starting with less than the accepted minimum, just to see what the real minimum is. Given the tiles seem, I wouldnt be suprised if SN24 had keyhole specialty tiles, but if SN 20 enters without them, dont expect SpaceX to pony up for an extra tile manufacturing line.
I dont know either, but recall that they seriously looked at deleting the heat shield entirely and rely just on the thermal mass of the steel. They dont need a whole lot of thermal protection, IIRC just enough to drop the peak heating by a sixth or so, below a thousand degrees.
The point was made that until we know what gaps are acceptable, we don't have a clue about tile layout. My methane producing gut says that Rakaydos's pattern is too open but what do I know.
They also have a history of starting with less than the accepted minimum, just to see what the real minimum is. Given the tiles seem, I wouldnt be suprised if SN24 had keyhole specialty tiles, but if SN 20 enters without them, dont expect SpaceX to pony up for an extra tile manufacturing line.
I do love how SpaceX finds the minimum. However, with a heatshield there is a prerequisite that they survive re-entry.
No doubt they've modeled this 1000's of times and have a good idea of the minimum requirement. For most of the heat shield it's probably a debate over small thicknesses and gaps.
Specialty areas and transitions should be the areas of biggest concern. The nose, transitions to the uncovered areas, areas by the flaps, even the edge along the engine bay.
Throw on a ton of instrumentation and start flying!
I can't wait to see what they do to SN20.
Long straight seams need to be avoided to keep the plasma from accelerating in the gaps, but what about long curved seams?Long curved seams might help with plasma at the margins but unfortunately won't help with the tessellation fit / number of tiles problem. And we have only seen 4 tile types from SpaceX so far. Three sizes of regular hexagon and a truncated hexagon (presumably for around the bottom of the skirt).
particularly this makes me think of Dragon 2's heat shield.
image from this thread: https://forum.nasaspaceflight.com/index.php?topic=41016.0 (https://forum.nasaspaceflight.com/index.php?topic=41016.0)
The tiling pattern discussion is beyond me but as to your second point, to me, that doesn't signify much. After all, we haven't seen any of the leading edge tiles or wing root tiles (or whatever they'll use in those places). We've also never seen any of the current tiles to date on the nose, so we can't be sure they'll use the same tiles there.Long straight seams need to be avoided to keep the plasma from accelerating in the gaps, but what about long curved seams?Long curved seams might help with plasma at the margins but unfortunately won't help with the tessellation fit / number of tiles problem. And we have only seen 4 tile types from SpaceX so far. Three sizes of regular hexagon and a truncated hexagon (presumably for around the bottom of the skirt).
particularly this makes me think of Dragon 2's heat shield.
image from this thread: https://forum.nasaspaceflight.com/index.php?topic=41016.0 (https://forum.nasaspaceflight.com/index.php?topic=41016.0)
I dont know either, but recall that they seriously looked at deleting the heat shield entirely and rely just on the thermal mass of the steel. They dont need a whole lot of thermal protection, IIRC just enough to drop the peak heating by a sixth or so, below a thousand degrees.
The point was made that until we know what gaps are acceptable, we don't have a clue about tile layout. My methane producing gut says that Rakaydos's pattern is too open but what do I know.
They also have a history of starting with less than the accepted minimum, just to see what the real minimum is. Given the tiles seen, I wouldnt be suprised if SN24 had keyhole specialty tiles, but if SN 20 enters without them, dont expect SpaceX to pony up for an extra tile manufacturing line.
All true so the design from page 1 is still a contender as are many of the others that have been posted.The tiling pattern discussion is beyond me but as to your second point, to me, that doesn't signify much. After all, we haven't seen any of the leading edge tiles or wing root tiles (or whatever they'll use in those places). We've also never seen any of the current tiles to date on the nose, so we can't be sure they'll use the same tiles there.Long straight seams need to be avoided to keep the plasma from accelerating in the gaps, but what about long curved seams?Long curved seams might help with plasma at the margins but unfortunately won't help with the tessellation fit / number of tiles problem. And we have only seen 4 tile types from SpaceX so far. Three sizes of regular hexagon and a truncated hexagon (presumably for around the bottom of the skirt).
particularly this makes me think of Dragon 2's heat shield.
image from this thread: https://forum.nasaspaceflight.com/index.php?topic=41016.0 (https://forum.nasaspaceflight.com/index.php?topic=41016.0)
It will be interesting to see what SN20 looks like. There have been many suggestions here in the “minimize the gaps” v “minimize the tile types” debate. I have previously focused on minimize the gaps, but as rakaydos and others have pointed out, we don’t know what is an acceptable gap and SpaceX have only tested three different sizes of hexagonal tile. With that in mind I will suggest another nosecone tile arrangement with gaps that uses tiles touching side by side around the circumference but leaves variable gaps between the rows.If large gaps are OK, then wouldn’t smaller tiles and larger gaps reduce the total mass of tiles by reducing the area covered? This isn’t what we see. Or maybe large gaps are OK in places, if offset by a thicker blanket, but accepting a mass penalty in those areas.
I'm not sure that's entirely fair, unless you turn the burner off before throwing the peas in. Clearly, heat is going to transfer to the water faster than it's going to transfer along the surface of the steel, but there's still a decent heat transfer that way.I dont know either, but recall that they seriously looked at deleting the heat shield entirely and rely just on the thermal mass of the steel. They dont need a whole lot of thermal protection, IIRC just enough to drop the peak heating by a sixth or so, below a thousand degrees.
The point was made that until we know what gaps are acceptable, we don't have a clue about tile layout. My methane producing gut says that Rakaydos's pattern is too open but what do I know.
They also have a history of starting with less than the accepted minimum, just to see what the real minimum is. Given the tiles seen, I wouldnt be suprised if SN24 had keyhole specialty tiles, but if SN 20 enters without them, dont expect SpaceX to pony up for an extra tile manufacturing line.
With the raw stainless steel exposed, hot spots are a huge problem because SS doesn't distribute heat well.
As I'm reminded every time I throw frozen peas into a stainless steel pan of barely boiling water, which burns my hand after the water furiously boils from being raised 1/2" by the peas and the waves from dropping the peas.. The sides of the pan 1/2" up from the water are at higher temperature than boiling water, because SS doesn't conduct heat very well.
Jam a tile into a too-small space and it will break. Clip a tile into a too-large space and it leaves wide gaps. Check for broken tiles or wide gaps, and remove and replace as needed. Tell Joe to drink more coffee.You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
An assembly where you have 10 unique but visually near-identical part variants, where all variants will physically fit in the location of any other variant, where variant-to-variant dimension deltas are of similar scale to within-variant tolerance, and removing a misplaced part (if discovered) is destructive to the part and potentially to the fixture? You're not manufacturing a product, you're manufacturing a headache.
Again, the actual manufacture of large number of unique fit-to-size tiles is not at issue. We know it can be done, STS did it decades ago. Figuring out ways to do it is attaching the wrong problem: the issue is whether you need to jump through that enormous number of dancing flying hoops in the first place.
Jam a tile into a too-small space and it will break. Clip a tile into a too-large space and it leaves wide gaps. Check for broken tiles or wide gaps, and remove and replace as needed. Tell Joe to drink more coffee.You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
An assembly where you have 10 unique but visually near-identical part variants, where all variants will physically fit in the location of any other variant, where variant-to-variant dimension deltas are of similar scale to within-variant tolerance, and removing a misplaced part (if discovered) is destructive to the part and potentially to the fixture? You're not manufacturing a product, you're manufacturing a headache.
Again, the actual manufacture of large number of unique fit-to-size tiles is not at issue. We know it can be done, STS did it decades ago. Figuring out ways to do it is attaching the wrong problem: the issue is whether you need to jump through that enormous number of dancing flying hoops in the first place.
I don’t see a big problem here. Use as many tile shapes are are needed to fit the shape of the vehicle.
Jam a tile into a too-small space and it will break. Clip a tile into a too-large space and it leaves wide gaps. Check for broken tiles or wide gaps, and remove and replace as needed. Tell Joe to drink more coffee.You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
An assembly where you have 10 unique but visually near-identical part variants, where all variants will physically fit in the location of any other variant, where variant-to-variant dimension deltas are of similar scale to within-variant tolerance, and removing a misplaced part (if discovered) is destructive to the part and potentially to the fixture? You're not manufacturing a product, you're manufacturing a headache.
Again, the actual manufacture of large number of unique fit-to-size tiles is not at issue. We know it can be done, STS did it decades ago. Figuring out ways to do it is attaching the wrong problem: the issue is whether you need to jump through that enormous number of dancing flying hoops in the first place.
I don’t see a big problem here. Use as many tile shapes are are needed to fit the shape of the vehicle.
The Space shuttle used as many tiles as were needed, and look how long it took to maintain those...
In the 'unique tile' edge case, "all tiles installed one position to the left, because one tile was installed incorectly and then used as datum for the rest" = "entire heat shield scrapped and a new one manufactured" due to the destructive nature of tile removal.Jam a tile into a too-small space and it will break. Clip a tile into a too-large space and it leaves wide gaps. Check for broken tiles or wide gaps, and remove and replace as needed. Tell Joe to drink more coffee.You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
An assembly where you have 10 unique but visually near-identical part variants, where all variants will physically fit in the location of any other variant, where variant-to-variant dimension deltas are of similar scale to within-variant tolerance, and removing a misplaced part (if discovered) is destructive to the part and potentially to the fixture? You're not manufacturing a product, you're manufacturing a headache.
Again, the actual manufacture of large number of unique fit-to-size tiles is not at issue. We know it can be done, STS did it decades ago. Figuring out ways to do it is attaching the wrong problem: the issue is whether you need to jump through that enormous number of dancing flying hoops in the first place.
I don’t see a big problem here. Use as many tile shapes are are needed to fit the shape of the vehicle.
In the 'unique tile' edge case, "all tiles installed one position to the left, because one tile was installed incorrectly and then used as datum for the rest" = "entire heat shield scrapped and a new one manufactured" due to the destructive nature of tile removal. --In the 'unique tile' edge case, "all tiles installed one position to the left, because one tile was installed incorectly and then used as datum for the rest" = "entire heat shield scrapped and a new one manufactured" due to the destructive nature of tile removal.Jam a tile into a too-small space and it will break. Clip a tile into a too-large space and it leaves wide gaps. Check for broken tiles or wide gaps, and remove and replace as needed. Tell Joe to drink more coffee.You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
An assembly where you have 10 unique but visually near-identical part variants, where all variants will physically fit in the location of any other variant, where variant-to-variant dimension deltas are of similar scale to within-variant tolerance, and removing a misplaced part (if discovered) is destructive to the part and potentially to the fixture? You're not manufacturing a product, you're manufacturing a headache.
Again, the actual manufacture of large number of unique fit-to-size tiles is not at issue. We know it can be done, STS did it decades ago. Figuring out ways to do it is attaching the wrong problem: the issue is whether you need to jump through that enormous number of dancing flying hoops in the first place.
I don’t see a big problem here. Use as many tile shapes are are needed to fit the shape of the vehicle.
Quick temporary bodges are anathema to Starship thus far. The goal of the development program has been developing the systems and techniques to efficiently and economically manufacture Starship. Designing 'one off' temporary heatshields or heat-shield designs that require two-man-rule or robots to install correctly are not manufacturable solutions. If there is a manufacturable solution to the TPS, then skip the time and money wasted on a temporary version and go for the one you actually want to use. This is why SpaceX have been happy to roll Starships off of the assembly line and straight into a back lot or scrap pile: the Starship itself isn't the goal, manufacturing one is. There is no value in constructing a TPS that you know is going to be replaced by a more manufacturable design.
Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
And if sharpie- guy fucked it up?In the 'unique tile' edge case, "all tiles installed one position to the left, because one tile was installed incorrectly and then used as datum for the rest" = "entire heat shield scrapped and a new one manufactured" due to the destructive nature of tile removal. --In the 'unique tile' edge case, "all tiles installed one position to the left, because one tile was installed incorectly and then used as datum for the rest" = "entire heat shield scrapped and a new one manufactured" due to the destructive nature of tile removal.Jam a tile into a too-small space and it will break. Clip a tile into a too-large space and it leaves wide gaps. Check for broken tiles or wide gaps, and remove and replace as needed. Tell Joe to drink more coffee.You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
An assembly where you have 10 unique but visually near-identical part variants, where all variants will physically fit in the location of any other variant, where variant-to-variant dimension deltas are of similar scale to within-variant tolerance, and removing a misplaced part (if discovered) is destructive to the part and potentially to the fixture? You're not manufacturing a product, you're manufacturing a headache.
Again, the actual manufacture of large number of unique fit-to-size tiles is not at issue. We know it can be done, STS did it decades ago. Figuring out ways to do it is attaching the wrong problem: the issue is whether you need to jump through that enormous number of dancing flying hoops in the first place.
I don’t see a big problem here. Use as many tile shapes are are needed to fit the shape of the vehicle.
Quick temporary bodges are anathema to Starship thus far. The goal of the development program has been developing the systems and techniques to efficiently and economically manufacture Starship. Designing 'one off' temporary heatshields or heat-shield designs that require two-man-rule or robots to install correctly are not manufacturable solutions. If there is a manufacturable solution to the TPS, then skip the time and money wasted on a temporary version and go for the one you actually want to use. This is why SpaceX have been happy to roll Starships off of the assembly line and straight into a back lot or scrap pile: the Starship itself isn't the goal, manufacturing one is. There is no value in constructing a TPS that you know is going to be replaced by a more manufacturable design.
How does this happen if tiles are labelled and positions are numbered (scribbled on steel with a Sharpy) and double-checked? A worker puts labelled-tile 1233 in numbered-position 1232, then puts labelled-tile 1234 in numbered-position 1233, etc., etc.? How often would this happen? (Maybe a robot would do it, but only once.)
How often would this happen?All the time.
“How does this happen if tiles are labelled and positions are numbered (scribbled on steel with a Sharpy) and double-checked?”And if sharpie- guy fucked it up?In the 'unique tile' edge case, "all tiles installed one position to the left, because one tile was installed incorrectly and then used as datum for the rest" = "entire heat shield scrapped and a new one manufactured" due to the destructive nature of tile removal. --In the 'unique tile' edge case, "all tiles installed one position to the left, because one tile was installed incorectly and then used as datum for the rest" = "entire heat shield scrapped and a new one manufactured" due to the destructive nature of tile removal.Jam a tile into a too-small space and it will break. Clip a tile into a too-large space and it leaves wide gaps. Check for broken tiles or wide gaps, and remove and replace as needed. Tell Joe to drink more coffee.You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
An assembly where you have 10 unique but visually near-identical part variants, where all variants will physically fit in the location of any other variant, where variant-to-variant dimension deltas are of similar scale to within-variant tolerance, and removing a misplaced part (if discovered) is destructive to the part and potentially to the fixture? You're not manufacturing a product, you're manufacturing a headache.
Again, the actual manufacture of large number of unique fit-to-size tiles is not at issue. We know it can be done, STS did it decades ago. Figuring out ways to do it is attaching the wrong problem: the issue is whether you need to jump through that enormous number of dancing flying hoops in the first place.
I don’t see a big problem here. Use as many tile shapes are are needed to fit the shape of the vehicle.
Quick temporary bodges are anathema to Starship thus far. The goal of the development program has been developing the systems and techniques to efficiently and economically manufacture Starship. Designing 'one off' temporary heatshields or heat-shield designs that require two-man-rule or robots to install correctly are not manufacturable solutions. If there is a manufacturable solution to the TPS, then skip the time and money wasted on a temporary version and go for the one you actually want to use. This is why SpaceX have been happy to roll Starships off of the assembly line and straight into a back lot or scrap pile: the Starship itself isn't the goal, manufacturing one is. There is no value in constructing a TPS that you know is going to be replaced by a more manufacturable design.
How does this happen if tiles are labelled and positions are numbered (scribbled on steel with a Sharpy) and double-checked? A worker puts labelled-tile 1233 in numbered-position 1232, then puts labelled-tile 1234 in numbered-position 1233, etc., etc.? How often would this happen? (Maybe a robot would do it, but only once.)
All the time. --How often would this happen?All the time.
Sharpie number is wrong. Sharpie number is ambiguous because of handwriting. Sharpie was cleaned off or obscured. Tile number is wrong. Tile number is ambiguous (e.g. off-by-one or transposable or invertible). Installer is tired. Installer is distracted. Installer shift changes. Install is two-handing to speed up operation, grabs tile N and N+1, reads number on N+1 and installs N in that position (and/or vice versa). Installer installs first tile wrong (for whatever reason), and installs all subsequent tiles wrong based on that tile location (because tiles were stacked in order of install, and install pattern is known) and this behaviour is rewarded due to increased productivity when installing before an error occurs. Checker makes any of the same mistakes as installer. Checker is looking for tiles to match, not looking for tiles to not match. Checker cannot see sharpie number (obscured by tile) so goes by relative tile position, or by map referencing (prone to error).
And those are just failure modes though of off the top of my head during the writing of that paragraph. When your protection against human error is "well, don't make an error then!" you have no error protection.
As for robots, those can be just as prone to human error due to humans needing to program and direct the robot. e.g. if the work coordinate system is based on the barrel being clocked in the fixture correctly, the barrel may be clocked in the fixture incorrectly. If it's based on using a specific stud as a datum, the wrong stud could be used. Stick a barcode under every stud pattern rather than sharpie? Whoops, wrong barcode was applied. Or the barcode printer has a bug and applies the same barcode to all spots. Or the barcode printer is iterating correctly, but one barcode got stuck in the applicator so every barcode is off by one. Etc.
The tempering. We've not heard, or maybe more accurately, we haven't discussed this in quite a while. There's so much incidental welding, is this still a thing? Probably is but I wonder. Would SS work if unhardened?I dont know either, but recall that they seriously looked at deleting the heat shield entirely and rely just on the thermal mass of the steel. They dont need a whole lot of thermal protection, IIRC just enough to drop the peak heating by a sixth or so, below a thousand degrees.
The point was made that until we know what gaps are acceptable, we don't have a clue about tile layout. My methane producing gut says that Rakaydos's pattern is too open but what do I know.
They also have a history of starting with less than the accepted minimum, just to see what the real minimum is. Given the tiles seem, I wouldnt be suprised if SN24 had keyhole specialty tiles, but if SN 20 enters without them, dont expect SpaceX to pony up for an extra tile manufacturing line.
I do love how SpaceX finds the minimum. However, with a heatshield there is a prerequisite that they survive re-entry.
No doubt they've modeled this 1000's of times and have a good idea of the minimum requirement. For most of the heat shield it's probably a debate over small thicknesses and gaps.
Specialty areas and transitions should be the areas of biggest concern. The nose, transitions to the uncovered areas, areas by the flaps, even the edge along the engine bay.
Throw on a ton of instrumentation and start flying!
I can't wait to see what they do to SN20.
From my notes stainless steel loses it's temper at 800C and melts at 1500C so that is a big enough gap that we should be getting SS back with steel that has lost its temper but is still intact enough to land.
So the ship won't refly but it will inform to where the heat shield needs to do better.
The shuttle... Let's think of the shuttle as a heatshield pathfinder. It taught us what not to do. It didn't teach us to not use tiles. It taught us keep the airframe shape as simple as possible. It taught us to pay attention to fastening. It taught us to really pay attention to reusability - not lip service.Jam a tile into a too-small space and it will break. Clip a tile into a too-large space and it leaves wide gaps. Check for broken tiles or wide gaps, and remove and replace as needed. Tell Joe to drink more coffee.You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
An assembly where you have 10 unique but visually near-identical part variants, where all variants will physically fit in the location of any other variant, where variant-to-variant dimension deltas are of similar scale to within-variant tolerance, and removing a misplaced part (if discovered) is destructive to the part and potentially to the fixture? You're not manufacturing a product, you're manufacturing a headache.
Again, the actual manufacture of large number of unique fit-to-size tiles is not at issue. We know it can be done, STS did it decades ago. Figuring out ways to do it is attaching the wrong problem: the issue is whether you need to jump through that enormous number of dancing flying hoops in the first place.
I don’t see a big problem here. Use as many tile shapes are are needed to fit the shape of the vehicle.
The Space shuttle used as many tiles as were needed, and look how long it took to maintain those...
Um, well yeah. The only problem is they don't really quite know what they need. Slap it together. See what didn't work. Fix. Repeat.In the 'unique tile' edge case, "all tiles installed one position to the left, because one tile was installed incorectly and then used as datum for the rest" = "entire heat shield scrapped and a new one manufactured" due to the destructive nature of tile removal.Jam a tile into a too-small space and it will break. Clip a tile into a too-large space and it leaves wide gaps. Check for broken tiles or wide gaps, and remove and replace as needed. Tell Joe to drink more coffee.You can uniquely label, use keyed fittings, and implement double- or triple-checking all you want. It will not stop someone hammering your IMU in upside-down, or connecting your TVC backwards.With clear labeling on the back of the tiles even a few hundred tile type should not really be much of an issue. It might even be possible to create a jig to allow standard tiles to be very precisely cut to create some of the specialist shapes in a hurry. They would need to be able to coat the cut edge, not sure how hard that would be?Clearly labeling the tiles at manufacturing time (maybe stenciling on the front surface with ablatable white ink) and writing numbers on the skin and double-checking before adding the tile should be enough to allow reliable placement even by tired workers.
An assembly where you have 10 unique but visually near-identical part variants, where all variants will physically fit in the location of any other variant, where variant-to-variant dimension deltas are of similar scale to within-variant tolerance, and removing a misplaced part (if discovered) is destructive to the part and potentially to the fixture? You're not manufacturing a product, you're manufacturing a headache.
Again, the actual manufacture of large number of unique fit-to-size tiles is not at issue. We know it can be done, STS did it decades ago. Figuring out ways to do it is attaching the wrong problem: the issue is whether you need to jump through that enormous number of dancing flying hoops in the first place.
I don’t see a big problem here. Use as many tile shapes are are needed to fit the shape of the vehicle.
Quick temporary bodges are anathema to Starship thus far. The goal of the development program has been developing the systems and techniques to efficiently and economically manufacture Starship. Designing 'one off' temporary heatshields or heat-shield designs that require two-man-rule or robots to install correctly are not manufacturable solutions. If there is a manufacturable solution to the TPS, then skip the time and money wasted on a temporary version and go for the one you actually want to use. This is why SpaceX have been happy to roll Starships off of the assembly line and straight into a back lot or scrap pile: the Starship itself isn't the goal, manufacturing one is. There is no value in constructing a TPS that you know is going to be replaced by a more manufacturable design.
Edzieba, I am curious, how do you think the tiles should be applied to Starship and how many types do you think there should be?How often would this happen?All the time.
Sharpie number is wrong. Sharpie number is ambiguous because of handwriting. Sharpie was cleaned off or obscured. Tile number is wrong. Tile number is ambiguous (e.g. off-by-one or transposable or invertible). Installer is tired. Installer is distracted. Installer shift changes. Install is two-handing to speed up operation, grabs tile N and N+1, reads number on N+1 and installs N in that position (and/or vice versa). Installer installs first tile wrong (for whatever reason), and installs all subsequent tiles wrong based on that tile location (because tiles were stacked in order of install, and install pattern is known) and this behaviour is rewarded due to increased productivity when installing before an error occurs. Checker makes any of the same mistakes as installer. Checker is looking for tiles to match, not looking for tiles to not match. Checker cannot see sharpie number (obscured by tile) so goes by relative tile position, or by map referencing (prone to error).
And those are just failure modes though of off the top of my head during the writing of that paragraph. When your protection against human error is "well, don't make an error then!" you have no error protection.
As for robots, those can be just as prone to human error due to humans needing to program and direct the robot. e.g. if the work coordinate system is based on the barrel being clocked in the fixture correctly, the barrel may be clocked in the fixture incorrectly. If it's based on using a specific stud as a datum, the wrong stud could be used. Stick a barcode under every stud pattern rather than sharpie? Whoops, wrong barcode was applied. Or the barcode printer has a bug and applies the same barcode to all spots. Or the barcode printer is iterating correctly, but one barcode got stuck in the applicator so every barcode is off by one. Etc.
Again, the question is how many tile the design actually needs. This is more than 5, but a small fraction of the total number of tiles. And whatever it is, that’s what it is. The question is how to (1) minimize requirements, then (2) meet those requirements. Yes?
Not a temporary bodge, just doing the actual job.
We are still mulling over the tiling of the SS nosecone, so I might suggest another variation of Slarty1080's initial design. One option could be a tile pattern whereby hexagonal tiles are stretched to become “six-sided polygons,” to better fit the surface of the nose cone.I'm not sure how this is different from the scheme on page one. Those tiles are irregular hexagonal polygons with non parallel sides and are not equal in length and there is one tile type per row.
Six-sided polygon means each side of a tile doesn’t have to be exactly parallel to its opposite side, or even equal in length. If we allow this variation, then we could employ rows of tiles on the nose of SS where the width of each tile is more narrow at the top than across its bottom. Tiles along the top row of the nose could be much more narrow than the bottom row to adapt to the much reduced circumference of the SS nose tip. In this approach, tiles could continue to be made flat and still approximate the curvature of the nose on different rows.
From what we know so far, nothing in the present manufacturing of tiles would preclude this variation in tile design.
Objectives of the this approach would be:
(1) Limit the number of tile shapes to one per row.
(2) Better approximate nose curvature using flat tiles.
(3) Better maintain consistent expansion gaps between tiles.
To exemplify how this might work, the sketch below shows a sample section of a nose cone subdivided into areas wherein tiles would be installed. As suggested by tile sample A, each area along the bottom of the nose cone is 30cm wide at the bottom and tiles inside these areas would intersect with the top edges of 30cm hexagon tiles running across the barrel section. The top edges of these nose tiles are slightly more narrow at the top and would intersect with the bottom edges of tiles in the next row above. Tiles in each row would be identical with each other, but slightly different from the tiles in the row above it. [Note that the slope of the example nose cone is not the same as actual SS nose cone.]
The whole sample section of areas would accommodate 20 tiles in each row. From the bottom of the nose section to the top, the sample section would contain twenty rows with a constant height of20cm30cm for each row. However, each row would be less wide as the nose narrows toward the top, from 30 cm to 15cm, and the ratio of widths from bottom to top would be 2:1. Therefore a sample tile from the middle row would have an average width of 22.5cm and tile shape B would fit within it. A sample area from the top row would have a width of 15cm along the top edge and tile shape C would fit within it.
Correction: wrong number
Notes:
(1)There are inaccuracies in the example. An area should not lie directly above another area, but each row should be staggered to allows tiles in each row to intersect with tiles above and below. (My laziness in drawing)
(2) Areas are not projected to be viewed in direct overhead perspective.
Yes, you had the idea first. This variation just emphasizes one type of tile per row on the nose..
I'm not sure how this is different from the scheme on page one. Those tiles are irregular hexagonal polygons with non parallel sides and are not equal in length and there is one tile type per row.
This was updated in post #1541 to show how three basic tile types might be used to stop the tile becoming too long and thin.
Unless the current application method (pushpin) turns out to have issues, it is a reasonable attachment method for repeatable and reliable installation. Chemical adhesives have known issues with adhesion and application time, application is vulnerable to small chemistry variants (e.g. the issues STS had with spitting in the silicone mix to retard curing, or waterproofing sprays degrading the silicone) and require technical skill for successful application.Edzieba, I am curious, how do you think the tiles should be applied to Starship and how many types do you think there should be?How often would this happen?All the time.
Sharpie number is wrong. Sharpie number is ambiguous because of handwriting. Sharpie was cleaned off or obscured. Tile number is wrong. Tile number is ambiguous (e.g. off-by-one or transposable or invertible). Installer is tired. Installer is distracted. Installer shift changes. Install is two-handing to speed up operation, grabs tile N and N+1, reads number on N+1 and installs N in that position (and/or vice versa). Installer installs first tile wrong (for whatever reason), and installs all subsequent tiles wrong based on that tile location (because tiles were stacked in order of install, and install pattern is known) and this behaviour is rewarded due to increased productivity when installing before an error occurs. Checker makes any of the same mistakes as installer. Checker is looking for tiles to match, not looking for tiles to not match. Checker cannot see sharpie number (obscured by tile) so goes by relative tile position, or by map referencing (prone to error).
And those are just failure modes though of off the top of my head during the writing of that paragraph. When your protection against human error is "well, don't make an error then!" you have no error protection.
As for robots, those can be just as prone to human error due to humans needing to program and direct the robot. e.g. if the work coordinate system is based on the barrel being clocked in the fixture correctly, the barrel may be clocked in the fixture incorrectly. If it's based on using a specific stud as a datum, the wrong stud could be used. Stick a barcode under every stud pattern rather than sharpie? Whoops, wrong barcode was applied. Or the barcode printer has a bug and applies the same barcode to all spots. Or the barcode printer is iterating correctly, but one barcode got stuck in the applicator so every barcode is off by one. Etc.
Yes, you had the idea first. This variation just emphasizes one type of tile per row on the nose..
I'm not sure how this is different from the scheme on page one. Those tiles are irregular hexagonal polygons with non parallel sides and are not equal in length and there is one tile type per row.
This was updated in post #1541 to show how three basic tile types might be used to stop the tile becoming too long and thin.
Yes, this might work for the first few rows on the nose. But the curvature of the nose becomes more severe as you go up the rows and the fit between wide flat tiles and the nose surface becomes worse.Yes, you had the idea first. This variation just emphasizes one type of tile per row on the nose..
I'm not sure how this is different from the scheme on page one. Those tiles are irregular hexagonal polygons with non parallel sides and are not equal in length and there is one tile type per row.
This was updated in post #1541 to show how three basic tile types might be used to stop the tile becoming too long and thin.
Depending on how big the gaps could be, you might get away with a shape spanning multiple rows rather than one shape per row.
The photos of the hot gas thrusters, presumably for fit checks, seem to show them in pods on the *outside* of the ring. That's one more weird shape to accommodate with a heat shield.
How many tile shapes does dragon use? It has a shield around its thrusters as well...
SpX is addressing the issue of varying expansion gaps between tiles.
Considering how the robotic arm welds the tile attachment pins to the SS surface, ISTM the arm would require frequent adjustments to maintain equal distance between each group of three pins. For one thing, the circumferential surface receiving the pins is based on a (presumed) SS radius of 450.0cm, whereas the underside of each tile is separated from that surface by an additional insulating blanket of 2 to 3 cm. This tiny increase in effective radius might cause differences in location to accumulate across rows. There could also be small irregularities, such as warping of the surface or small differences in tile dimensions, that could accumulate across rows.
It is likely they are incorporating methods to accurately measure and adjust the location of each group of three pins before they are welded in place.
I've worked with robots with a matched and dedicated controller for each motor. The factory burns a controller ROM that maps periodic errors. Once that sucker knows where it is it's dead on for a goodly excursion.SpX is addressing the issue of varying expansion gaps between tiles.
Considering how the robotic arm welds the tile attachment pins to the SS surface, ISTM the arm would require frequent adjustments to maintain equal distance between each group of three pins. For one thing, the circumferential surface receiving the pins is based on a (presumed) SS radius of 450.0cm, whereas the underside of each tile is separated from that surface by an additional insulating blanket of 2 to 3 cm. This tiny increase in effective radius might cause differences in location to accumulate across rows. There could also be small irregularities, such as warping of the surface or small differences in tile dimensions, that could accumulate across rows.
It is likely they are incorporating methods to accurately measure and adjust the location of each group of three pins before they are welded in place.
I expect they're using some sort of fixed reference point(s) to let the arm calibrate itself. It wouldn't be *that* hard to use a computer vision system to measure position to a sub-millimeter level based on triangulating from some reference marks, and they might not even need that (i.e., calibrate to the mm level for tile placement, and only have sub-mm for the three pins for a tile relative to each other).
Nosecone and barrel section in front of windbreak.
B3 in high bay.
GSE 5 mid #2 outside the tents.
Stargate sign.
Is there any likelihood that ice/frost accumulates under the tiles when fueling on the pad? I don't have a good sense of how well air can permeate the matting under the tiles. If ice/frost does form, what eventually happens to it?
Is there any likelihood that ice/frost accumulates under the tiles when fueling on the pad? I don't have a good sense of how well air can permeate the matting under the tiles. If ice/frost does form, what eventually happens to it?
It was first spotted at the start of June (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2248077#msg2248077), doesn't appear to have been touched since.
In one of Mary's latest shots you can see some heat shield tiles on the flap aero covers.
image credit: bocachicagal
Well, this answers one question. SX seems willing to do customized tile to some extent. What that extent is, is at yet unknown.
The curve is definitely a customization. What about the vitrified black? It normally covers the edge and only part way down the side. Here we see it covering the entire side. A customization or a change of plan?
There are what look like pins along the aft edge. A few off to the right of the top tile. Maybe not pins?
What is the black strip curling back over from the windward side? The edge will be one of the hot spots. Some special treatment or just the way the light is hitting the stainless?
Ohhh! So many questions.
Edit: went back and looked again. That black doesn't look like a lighting artifact.
I followed up through the O'c layout but I'm not sure about the other tile your matching against. Could you post a pic with both sets of tiles and highlight the one you're pointing out?Well, this answers one question. SX seems willing to do customized tile to some extent. What that extent is, is at yet unknown.
The curve is definitely a customization. What about the vitrified black? It normally covers the edge and only part way down the side. Here we see it covering the entire side. A customization or a change of plan?
There are what look like pins along the aft edge. A few off to the right of the top tile. Maybe not pins?
What is the black strip curling back over from the windward side? The edge will be one of the hot spots. Some special treatment or just the way the light is hitting the stainless?
Ohhh! So many questions.
Edit: went back and looked again. That black doesn't look like a lighting artifact.
OTV, I'm curious to know your take on something I "think" I see on the close up of the image that Mary took. Bear with me here as I try to articulate this.
If you consider the apex of each point of the hex shape of the tiles as 2, 4, 6, 8, 10, and 12 o'clock, then the 8 o'c/10 o'c edge of the lower of the two full tiles shown seems to match up with the 2 o'c/4 o'c edge of a tile further away on the windward face of the cowling. In other words, it (barely) looks to me like a pattern of tiles. The view angle doesn't allow gaps or spacing to be determined, but it just seems to me that there is the possibility of several tiles of similar shape being attached in that area. Absence of the felt and netting is obvious, maybe because it isn't necessary, as others have noted above. I am intrigued by this new design step, to say the least.
I am pretty sure there are some lower temperature areas on the leeward side of the shuttle that are protected by teased Nomex felt bonded and coated with high temperature silicone adhesive. Only good to about 1100 F, if I remember right. If not, I'm sure someone will correct me. ;^)John, could you straighten me out on a point? AIUI the large circular cross section puts the shortest distance between the hull and shock front at the stagnation line, the windward center line. This is unlike a capsule where the tightest point is around the periphery. AIUI, the closest point is where compressive heating is greatest. I know radiative heating is there too, but I'm only asking about compressive.
John
I am pretty sure there are some lower temperature areas on the leeward side of the shuttle that are protected by teased Nomex felt bonded and coated with high temperature silicone adhesive. Only good to about 1100 F, if I remember right. If not, I'm sure someone will correct me. ;^)John, could you straighten me out on a point? AIUI the large circular cross section puts the shortest distance between the hull and shock front at the stagnation line, the windward center line. This is unlike a capsule where the tightest point is around the periphery. AIUI, the closest point is where compressive heating is greatest. I know radiative heating is there too, but I'm only asking about compressive.
John
Do I have this right?
That's actually what was in mind behind the question. Looks like there might be some positioning limits on the fins during that part of EDL, which leads to another question.I am pretty sure there are some lower temperature areas on the leeward side of the shuttle that are protected by teased Nomex felt bonded and coated with high temperature silicone adhesive. Only good to about 1100 F, if I remember right. If not, I'm sure someone will correct me. ;^)John, could you straighten me out on a point? AIUI the large circular cross section puts the shortest distance between the hull and shock front at the stagnation line, the windward center line. This is unlike a capsule where the tightest point is around the periphery. AIUI, the closest point is where compressive heating is greatest. I know radiative heating is there too, but I'm only asking about compressive.
John
Do I have this right?
Yes, but also the shock will be pretty close at the edges of the control surface edges. This would be similar to the edges of a capsule where heating is also high.
John
Control comes from shifting center of pressure around relative to center of gravity. It's exactly the same as skydiving (except...)Yeah, but if the flow behind the shock is nil what are the fins acting on? Part of the question was about gas transfer through the shock. No flow=nothing for the fins to act against. At the other extreme is the gas flow behind the shock going supersonic. This has its own problems. I'm trying to mental model the stagnation region in greater granularity than what we've seen yet.
Control comes from shifting center of pressure around relative to center of gravity. It's exactly the same as skydiving (except...)Yeah, but if the flow behind the shock is nil what are the fins acting on? Part of the question was about gas transfer through the shock. No flow=nothing for the fins to act against. At the other extreme is the gas flow behind the shock going supersonic. This has its own problems. I'm trying to mental model the stagnation region in greater granularity than what we've seen yet.
Last night the nosecone sections were stacked.Nose to the right of shot has studs and tiles applied.
I was typing, trying to explain how I understand it, but I don't have training in hypersonic aerodynamics so don't want misinform. However I think there's a simplification that answers your question:Control comes from shifting center of pressure around relative to center of gravity. It's exactly the same as skydiving (except...)Yeah, but if the flow behind the shock is nil what are the fins acting on? Part of the question was about gas transfer through the shock. No flow=nothing for the fins to act against. At the other extreme is the gas flow behind the shock going supersonic. This has its own problems. I'm trying to mental model the stagnation region in greater granularity than what we've seen yet.
Last night the nosecone sections were stacked.Nose to the right of shot has studs and tiles applied.
I noticed something interesting in this picture of S20's leg skirt. If you look closely, 1/3 of the TPS tile attachment studs are a lighter color than the rest. I've attached a picture highlighting some of the differently colored studs.
A slightly more substantial stud related observation: The studs seen on this nose cone appears to follow the standard pattern but upside down for all but one row visible. This suggests either "unique rows" or "regular with some gaps" tiling with some type dependent variation in stud orientation (to fit a different shape or to avoid installation mixup?).Here's what I'm seeing.
<snip>
Good observation. If a straight seam is ok they could just use two rows of the truncated "pentagonal" tiles with one of them upside down. That would be two tile types for part of the nose at the cost of larger vertical gaps: Starting at 4.5 m radius one missing tile on half the circumference would be ~4 mm of extra gap. It increases ~linearly with decreasing radius but most of the nose cone area has relatively large radius.A slightly more substantial stud related observation: The studs seen on this nose cone appears to follow the standard pattern but upside down for all but one row visible. This suggests either "unique rows" or "regular with some gaps" tiling with some type dependent variation in stud orientation (to fit a different shape or to avoid installation mixup?).Here's what I'm seeing.
<snip>
The inverted row of studs lines up with the lower hex pattern, but not the upper hex pattern. This suggests that the upper hex pattern is using the same size tiles as the lower hex pattern, just with different placement to accommodate the ogive, and there's some sort of "transition" row for bridging the inevitable gap.
It could be something as simple as this....
If a straight seam is okIf straight seams can work, this greatly simplifies the design problem and reduces requirements for peculiar tiles. It would be worth some seam-engineering effort to make this true.
Elon has mentioned that the reason they don’t want straight seams generally is that hot plasma can accelerate up the seam. But if there are only a few places with a straight seam, then perhaps they can put additional thermal cloth underneath those particular areas.If a straight seam is okIf straight seams can work, this greatly simplifies the design problem and reduces requirements for peculiar tiles. It would be worth some seam-engineering effort to make this true.
If a straight seam is ok they could just use two rows of the truncated "pentagonal" tiles with one of them upside down. That would be two tile types for part of the nose at the cost of larger vertical gaps: Starting at 4.5 m radius one missing tile on half the circumference would be ~4 mm of extra gap. It increases ~linearly with decreasing radius but most of the nose cone area has relatively large radius.Without any clever pixel counting, just eyeballing it, we seem to have about 19 tiles on the lower layer for every 18 tiles on the upper layer. So that should give us an idea of how large of a vertical gap they’ll be dealing with.
I wonder, it looks like you could alternate the pentagon on the top or bottom of the seam, and so interupt the seam with (unmatching) hexagons on both sides.A slightly more substantial stud related observation: The studs seen on this nose cone appears to follow the standard pattern but upside down for all but one row visible. This suggests either "unique rows" or "regular with some gaps" tiling with some type dependent variation in stud orientation (to fit a different shape or to avoid installation mixup?).Here's what I'm seeing.
<snip>
The inverted row of studs lines up with the lower hex pattern, but not the upper hex pattern. This suggests that the upper hex pattern is using the same size tiles as the lower hex pattern, just with different placement to accommodate the ogive, and there's some sort of "transition" row for bridging the inevitable gap.
It could be something as simple as this....
I wonder, it looks like you could alternate the pentagon on the top or bottom of the seam, and so interupt the seam with (unmatching) hexagons on both sides.
Like you, I've no training in hypersonics. A shockwave is an interesting thing. Confusing, but interesting. The ship is moving faster than the air can get out of the way. It piles up. I wonder what an ambient pressure reading would be behind the shock front. I'm guessing high.I was typing, trying to explain how I understand it, but I don't have training in hypersonic aerodynamics so don't want misinform. However I think there's a simplification that answers your question:Control comes from shifting center of pressure around relative to center of gravity. It's exactly the same as skydiving (except...)Yeah, but if the flow behind the shock is nil what are the fins acting on? Part of the question was about gas transfer through the shock. No flow=nothing for the fins to act against. At the other extreme is the gas flow behind the shock going supersonic. This has its own problems. I'm trying to mental model the stagnation region in greater granularity than what we've seen yet.
Consider that the ship is coming in from space and hitting the atmosphere. it's slamming into gas atoms and pushing them out of the way. Now, whatever happens upstream(shock fronts, boundary layers, etc) doesn't really change the fact that the ship is still moving through the atmosphere hitting gas atoms and pushing them out of the way. So that's what the fins are acting against.
That would work but ISTM to be too complicated for production. IIUC, every few rows there is one row where all but one tile is custom to match the progressively out of phase zig zag. No two in the row duplicate. When the working guy gathers materials there might be coding of some sort but no easy eyeball verification. Multiple checks needed to make sure tile xyz isn't going into the slot for xyq.I wonder, it looks like you could alternate the pentagon on the top or bottom of the seam, and so interupt the seam with (unmatching) hexagons on both sides.
The problem is that the hexagons on top and bottom don't (in general) line up. So you'd need to have custom tile shapes to account for the local "slip" between top and bottom. But (a) you can fix the slip at 0 on the centerline, so a standard center pair can be used, and (b) the bottom pentagon can always have a zig in a fixed spot, so you only need a "full custom" tile above that, and (c) if you're patient and tolerances are loose enough, you could just wait until the slip gets to a known amount and put in the tile zigs at that point. Depending on how flexible you are about how long the straight line seams can get and how closely the zigs must match.
To be clear, based on those photos, my strong lean is that "long straight channels don't matter (much)" aka that they will find a different way to break up the flow (if flow in the circumferential direction even "matters"). Each row will be a regular hex, of one of the three-ish sizes we've seen, presumably smaller as you approach the nose, and when the radius has decreased "enough" there will be a pair of half-hex/pentagon rows to allow the rows to slip along the channel and the radius to decrease. Hexes won't be appreciably rounded until you switch to full-custom at the tip of the nose/on the flap fairings/etc.My prediction: Rows of back-to-back truncated hexes where needed to solve phase problems, a straight-channel gap-filler/insulator between them if needed. All tiles in a row identical, several increments of increasingly tapered tiles moving up toward the strongly tapered part of the ogive. More distinct tapered shapes if fit is important, fewer shapes if fit is less important. Bar codes optional.
If each hexagon is matched to a flat-topped pentagon, they dont have to match up. The point on the hexagon just has to be somewhere along the edge of the pentagonal tile.I wonder, it looks like you could alternate the pentagon on the top or bottom of the seam, and so interupt the seam with (unmatching) hexagons on both sides.
The problem is that the hexagons on top and bottom don't (in general) line up. So you'd need to have custom tile shapes to account for the local "slip" between top and bottom. But (a) you can fix the slip at 0 on the centerline, so a standard center pair can be used, and (b) the bottom pentagon can always have a zig in a fixed spot, so you only need a "full custom" tile above that, and (c) if you're patient and tolerances are loose enough, you could just wait until the slip gets to a known amount and put in the tile zigs at that point. Depending on how flexible you are about how long the straight line seams can get and how closely the zigs must match.
If each hexagon is matched to a flat-topped pentagon, they dont have to match up. The point on the hexagon just has to be somewhere along the edge of the pentagonal tile.Oh, yes, I like this. Very simple, very clean, and very difficult to mess up.
--v-v-v--
^-^^-^
Edit: an MS paint edit of the original proposal.
I'm boning up on non Newtonian flow. It's gonna be slow.If each hexagon is matched to a flat-topped pentagon, they dont have to match up. The point on the hexagon just has to be somewhere along the edge of the pentagonal tile.I wonder, it looks like you could alternate the pentagon on the top or bottom of the seam, and so interupt the seam with (unmatching) hexagons on both sides.
The problem is that the hexagons on top and bottom don't (in general) line up. So you'd need to have custom tile shapes to account for the local "slip" between top and bottom. But (a) you can fix the slip at 0 on the centerline, so a standard center pair can be used, and (b) the bottom pentagon can always have a zig in a fixed spot, so you only need a "full custom" tile above that, and (c) if you're patient and tolerances are loose enough, you could just wait until the slip gets to a known amount and put in the tile zigs at that point. Depending on how flexible you are about how long the straight line seams can get and how closely the zigs must match.
--v-v-v--
^-^ ^-^
Edit: an MS paint edit of the original proposal.
I still think there's just a straight line. As you pointed out, it can be broken up with a "real" hexagon periodically when the rows line up. I bet that's enough, combined with a bit of filler in the straight channel.Like this?
ISTM the width of gaps between tiles must lie within a certain range (tolerance). If gaps were too narrow tiles could rub together and crack. If the gap were too wide, supersonic flow across tile surfaces during atmospheric entry could dip into the crack and create a super-hot spot. To avoid this, a standard gap tolerance range should be established.
Despite the need for a standard gap tolerance, it seems unlikely that pins could be placed on a row so perfectly that one standard tile could fit perfectly across the entire row. Each tile would have to maintain the standard gap tolerance on all six sides of itself, despite variations in the surface of SS, variations in the insulation layer, and variable adjustments made in the locations of the other tiles. As tiles were emplaced across a row of pins it seems likely that small errors would accumulate so there would be a space somewhere that was sufficiently irregular so that a standard tile would not fit. A method of accommodating this situation would be needed.
To help illustrate one approach, I copied the excellent rendering of tiles (double row E) posted above by sevenperforce. I copied the bottom rows, inverted them, and placed them above the bottom rows, so that almost all tiles would have the same close-fitted tile gaps.
I expect that the first tile on each row (from left or from right) would be easier to fit perfectly because only two of its edges have to match the edges of two tiles on the row below (if working bottom up). If pinning each row from the left or right tile and working toward the middle, each tile has to match three sides with adjacent tiles and maintain the standard tile gap. If the pinning procedure begins from both ends, then there would be a place in the middle where one tile must match four edges (two from the same row and two from the row below). ISTM unlikely that a standard tile would fit exactly in this space, so a nonstandard (special) tile would usually be produced to fit this space. Each row on the barrel section of SS would utilize 18 standard-shaped tiles and one special tile.
Once a special tile was produced for any row, it seems probable that another special tile would be required in the next row above to match one side of the first special tile.
In the image below, the row of tiles lying over a weld line may require more special tiles. This is because the pinning of tiles on the upper and lower ring segments stops short of the two metal edges of the segments. Bare metal edges along the join line are welded together, followed by pinning one or two rows of tiles that cover the weld line. This procedure introduces the likelihood of additional mismatches between tiles in the top segment and tiles in the bottom segment and adjustments made by producing more special tiles. Ideally, one special tile could accommodate location errors in both X and Y directions, as indicated.
Image credit to Ocean CamYes, and the main argument against using enough different tile shapes to actually fit the shape of the vehicle seems to be “Sleepy workers will mislabel the tiles or switch them around, and then -- Oh noes! Doom or cost explosion! It’s better to have gaps.”
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
I'm guessing that flaps not having a cryogenic propellant inside them will have a smaller range of thermal expansion, so tiles there probably don't need empty gaps between them and using filler might be okay.
The tank will have larger temperature range and therefore also larger thermal expansion range, so instead of using filler they went with the blanket underneath - something that maybe isn't needed on those parts of the ship where the filler can be used.
I mean, it IS better to have gaps, if you CAN have gaps. That is the question that only SpaceX can answer.Image credit to Ocean CamYes, and the main argument against using enough different tile shapes to actually fit the shape of the vehicle seems to be “Sleepy workers will mislabel the tiles or switch them around, and then -- Oh noes! Doom or cost explosion! It’s better to have gaps.”
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
Or am I missing something?
I'm guessing that flaps not having a cryogenic propellant inside them will have a smaller range of thermal expansion, so tiles there probably don't need empty gaps between them and using filler might be okay.
The tank will have larger temperature range and therefore also larger thermal expansion range, so instead of using filler they went with the blanket underneath - something that maybe isn't needed on those parts of the ship where the filler can be used.
I believe the estimated temp on reentry is 3500C in the hot spots. Compare that to -182C(90K) boiling for LOX.
Not much difference in temp range.
Image credit to Ocean CamYes, and the main argument against using enough different tile shapes to actually fit the shape of the vehicle seems to be “Sleepy workers will mislabel the tiles or switch them around, and then -- Oh noes! Doom or cost explosion! It’s better to have gaps.”
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
Or am I missing something?
The leading edge tiles are thicker, too.
An arrangement of pentagonal and hexagonal tiles has been mentioned on this forum this year along with other options. We will have to see. Avoiding a single piece RCC section on the nosecone is what they will try avoid.ISTM the width of gaps between tiles must lie within a certain range (tolerance). If gaps were too narrow tiles could rub together and crack. If the gap were too wide, supersonic flow across tile surfaces during atmospheric entry could dip into the crack and create a super-hot spot. To avoid this, a standard gap tolerance range should be established.
Despite the need for a standard gap tolerance, it seems unlikely that pins could be placed on a row so perfectly that one standard tile could fit perfectly across the entire row. Each tile would have to maintain the standard gap tolerance on all six sides of itself, despite variations in the surface of SS, variations in the insulation layer, and variable adjustments made in the locations of the other tiles. As tiles were emplaced across a row of pins it seems likely that small errors would accumulate so there would be a space somewhere that was sufficiently irregular so that a standard tile would not fit. A method of accommodating this situation would be needed.
To help illustrate one approach, I copied the excellent rendering of tiles (double row E) posted above by sevenperforce. I copied the bottom rows, inverted them, and placed them above the bottom rows, so that almost all tiles would have the same close-fitted tile gaps.
I expect that the first tile on each row (from left or from right) would be easier to fit perfectly because only two of its edges have to match the edges of two tiles on the row below (if working bottom up). If pinning each row from the left or right tile and working toward the middle, each tile has to match three sides with adjacent tiles and maintain the standard tile gap. If the pinning procedure begins from both ends, then there would be a place in the middle where one tile must match four edges (two from the same row and two from the row below). ISTM unlikely that a standard tile would fit exactly in this space, so a nonstandard (special) tile would usually be produced to fit this space. Each row on the barrel section of SS would utilize 18 standard-shaped tiles and one special tile.
Once a special tile was produced for any row, it seems probable that another special tile would be required in the next row above to match one side of the first special tile.
In the image below, the row of tiles lying over a weld line may require more special tiles. This is because the pinning of tiles on the upper and lower ring segments stops short of the two metal edges of the segments. Bare metal edges along the join line are welded together, followed by pinning one or two rows of tiles that cover the weld line. This procedure introduces the likelihood of additional mismatches between tiles in the top segment and tiles in the bottom segment and adjustments made by producing more special tiles. Ideally, one special tile could accommodate location errors in both X and Y directions, as indicated.
Starting from the center line should eliminate the special tile.
But I believe we are going to see truncated hexes(pentagons) between the barrel sections giving a straight line gap between barrel sections. Probably also a special size to them to match the barrels slight misplacement between barrels.
Zig Zag is a better tile gap but if the gap is small enough and deep enough straight line gaps should be acceptable. I think straight line gaps every so often for the nose cone will be the way they solve curvature problem of the nose.
Thanks. I stand corrected!The leading edge tiles are thicker, too.
- This is not a leading edge. It is a hinge line. It is cylindrical to maintain a small gap to help in sealing air from flowing through the hinge.
John
Image credit to Ocean CamYes, and the main argument against using enough different tile shapes to actually fit the shape of the vehicle seems to be “Sleepy workers will mislabel the tiles or switch them around, and then -- Oh noes! Doom or cost explosion! It’s better to have gaps.”
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
Or am I missing something?
The actual argument is it significantly increases cost and complexity to have lots of kinds of tiles, for pretty obvious reasons already discussed in this thread. It’s not impossible or undoable, but damn it sure would be nice to avoid.
Starship is a significantly simpler and more uniform shape than Shuttle so do not worry about the massive numbers of unique tile shapes it required, which I suspect is the nightmare lurking in the back of people's minds, possibly subconsiously.
Image credit to Ocean CamYes, and the main argument against using enough different tile shapes to actually fit the shape of the vehicle seems to be “Sleepy workers will mislabel the tiles or switch them around, and then -- Oh noes! Doom or cost explosion! It’s better to have gaps.”
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
Or am I missing something?
The actual argument is it significantly increases cost and complexity to have lots of kinds of tiles, for pretty obvious reasons already discussed in this thread. It’s not impossible or undoable, but damn it sure would be nice to avoid.
Nice to avoid, well.... SpaceX is eminently capable of producing different-shaped tiles and keeping track of them during production and spacecraft assembly. Those challenges are rather small compared to all the other challenges they are dealing with. I think the pragmatic thing is just to produce the tiles needed instead of jumping through hoops and leaving gaps in order to increase production uniformity. Yeah, there might be 50 different tiles instead of five. No big deal.
Image credit to Ocean Cam
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
More wide gaps, less mass. Wide gaps everywhere?I mean, it IS better to have gaps, if you CAN have gaps. That is the question that only SpaceX can answer.Image credit to Ocean CamYes, and the main argument against using enough different tile shapes to actually fit the shape of the vehicle seems to be “Sleepy workers will mislabel the tiles or switch them around, and then -- Oh noes! Doom or cost explosion! It’s better to have gaps.”
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
Or am I missing something?
:) Very good idea I didn't think of....
...
In the image below, the row of tiles lying over a weld line may require more special tiles. This is because the pinning of tiles on the upper and lower ring segments stops short of the two metal edges of the segments. Bare metal edges along the join line are welded together, followed by pinning one or two rows of tiles that cover the weld line. This procedure introduces the likelihood of additional mismatches between tiles in the top segment and tiles in the bottom segment and adjustments made by producing more special tiles. Ideally, one special tile could accommodate location errors in both X and Y directions, as indicated.
Starting from the center line should eliminate the special tile.
...
...
It is hard to tell with perspective, etc...do the curved pentagonal edge tiles get larger and larger as you move down the flap root? Or are they all the same size? If they are getting larger and larger then we are getting tiles which are completely non-interchangeable.Image credit to Ocean Cam
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
With Mary's photos, that's even clearer. In particular, check out these cap-like tiles forming a full ring around one of the flap's cylindrical endpoints. Not only are they nothing like any other tile visible, they're also different than the tiles on the other end. SpaceX clearly has no qualms with - or bottlenecks preventing - the creation of a diverse range of tile shapes.
It looks like all the edge tiles are bonded to a thin metal underlayment that is also separate from the main flap structure. I think they can potentially install/remove large sections of these more intricate tile arrangements in a single go.The tile thickness transition is cool. It really looks like they used computer modeling to say “here is where we need special tiles, and here is how they are shaped, and here is how they fit into the ordinary tiles we use everywhere else.”
See attached image crop, originally posted by Dave G in the prototype thread … which I couldn’t figure out how to quote directly so I hope this satisfies citation responsibilities.
Edit: moved from prototype thread to here. :)
Also it appears that some of the tiles got damaged during the transport to Starbase. I see one chipped tile and missing tiles to the left (back of the end of the flap) where the white insulation is. It does seem the tiles are somewhat fragile.
...the flap edge view showing only plain-text ID info.
These photo show pins along the bottom of the fin for more tiles.But wait, wait! There's more. A lot of interesting things in that pic. Not only does SX show us that they're not shy about curving tiles to match the surface they're working with, they show us that they are not shy about shaping the tile to match the edge limits of the underlying geometry. More interesting is that the are willing to modify the Z axis to keep the gap constant on a radius position. It's starting to look a bit shuttle like (do I have to start dodging thrown fruit?) but with a simpler geometry that will result in MUCH fewer tiles.
Looks like they're using they're using the backing insulation as filler on the hinge tiles?
https://twitter.com/StarshipGazer/status/1416111047015116806? (https://twitter.com/StarshipGazer/status/1416111047015116806?)
I said something in that direction but not as extreme as you put it. The point I was making was that having a series of tiles, each progressively slightly different than the previous is not a good thing. Better to have each row on the ogive (for example) have all the same tile and each row differ as necessary. There are places where different tile shapes are needed because the underlying shape changes abruptly. Hard to miss a cue like that even 11 hours into the shift with sweat running into your eyes. Been there. Done that.Image credit to Ocean CamYes, and the main argument against using enough different tile shapes to actually fit the shape of the vehicle seems to be “Sleepy workers will mislabel the tiles or switch them around, and then -- Oh noes! Doom or cost explosion! It’s better to have gaps.”
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
Or am I missing something?
I'm seeing a pragmatic compromise between "every tile is unique" and "there is only one tile shape". For example, the "rim" tiles are full custom, but they did arrange it so there are an integral number of identical rim tiles. Similarly, the cylindrical hinge tiles appear to be uniquely curved in each row -- but then the same four or so tile shapes repeat all down the hinge and transition to what looks like the standard hex grid on the flat surface. So "as few as possible" tile shapes, but they haven't compromised in tile thickness or gap width just to have fewer shapes, and they are definitely not afraid of throwing in a custom shape where the geometry requires. But once they have a custom shape, they try to reuse it as many times as they can."As few (tile shapes) as possible, and no fewer."
LATER: On the end of the fin (not yet covered) I'd bet dollars to donuts they reuse the flat-sided pentagon tiles for the majority of that top edge, with just one or two custom tiles at the hinge end to follow the circular profile.
sevenperforce: Because starship is steel, they could very readily design numerous small inspection robots with magnetic feet to crawl the exterior and photograph tiles.Ah, too bad.
The skin is 304L stainless, which at a glance, is considered to be either non-magnetic, or only weakly magnetic. So a mag crawler wouldn't be my top guess for an on-orbit inspection method.
I'm seeing a pragmatic compromise between "every tile is unique" and "there is only one tile shape". For example, the "rim" tiles are full custom, but they did arrange it so there are an integral number of identical rim tiles. Similarly, the cylindrical hinge tiles appear to be uniquely curved in each row -- but then the same four or so tile shapes repeat all down the hinge and transition to what looks like the standard hex grid on the flat surface. So "as few as possible" tile shapes, but they haven't compromised in tile thickness or gap width just to have fewer shapes, and they are definitely not afraid of throwing in a custom shape where the geometry requires. But once they have a custom shape, they try to reuse it as many times as they can.
sevenperforce: Because starship is steel, they could very readily design numerous small inspection robots with magnetic feet to crawl the exterior and photograph tiles.I think the obvious long term answer to inspecting atmosphere-borne spacecraft bellies is using highly nimble and compact RCS drones, and autonomous ones at that. In the near term, unmanned missions could be uninspected and manned missions could involve EVA of some kind. There's also the possibility of cameras on booms (spinoff technology to deployable solar arrays?) but I don't see that as thorough enough.
The skin is 304L stainless, which at a glance, is considered to be either non-magnetic, or only weakly magnetic. So a mag crawler wouldn't be my top guess for an on-orbit inspection method.
Image credit to Ocean CamYes, and the main argument against using enough different tile shapes to actually fit the shape of the vehicle seems to be “Sleepy workers will mislabel the tiles or switch them around, and then -- Oh noes! Doom or cost explosion! It’s better to have gaps.”
Has the debate over whether SpaceX is willing to produce a more diverse array of heat shield sizes and shapes been solved yet? I think this image of the heat shielding for the forward flaps really adds to the argument that they are willing to sacrifice greater simplicity in manufacturing and tile placement for simpler patterns. Note how these tiles appear to be far smaller than ones we've seen before and how they they abruptly cut off the tile on the far left.
Or am I missing something?
The actual argument is it significantly increases cost and complexity to have lots of kinds of tiles, for pretty obvious reasons already discussed in this thread. It’s not impossible or undoable, but damn it sure would be nice to avoid.
The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
2. Would they keep an inventory of tiles for repair on each manned SS and train at least one of the crewmembers in repair? Or would it be simpler to send up another SS with "mechanics" to rescue the crew and repair the damaged SS?
3. Would it be worthwhile to even try to repair a damaged but unmanned SS in orbit?
The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
2. Would they keep an inventory of tiles for repair on each manned SS and train at least one of the crewmembers in repair? Or would it be simpler to send up another SS with "mechanics" to rescue the crew and repair the damaged SS?
3. Would it be worthwhile to even try to repair a damaged but unmanned SS in orbit?
Don't forget that they wish send a huge number of people to Mars and an even larger number for P2P. Projects of such scale are infeasible with an unreliable heat shield, which has to be checked and, maybe, repair.
The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
Lets try the 2003 NASA Space Shuttle Columbia leading edge failure that killed seven Astronauts for starters...
The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
So if you can demonstrate that they don't fail, there is no need for inspections to verify they haven't failed? That seems like a reasonable way to look at most things; are there general rules that you still inspect things which, if they fail it's a loss of vehicle?
Skittishness over past experience with HRSI tiles.The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
Skittishness over past experience with HRSI tiles.The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
No debris shedding on launch, but the structure and method for manufacture (described in one of the environmental docs for the Astronaut Blvd. site) are almost identical to HRSI: sintered pure silica fibres, reaction-cured Borosilicate glass coating, then impregnated with acetic acid & a waterproofing agent. The only change is the waterproofing agent (methyl-trimethoxy silane rather than dimethylethoxy silane) and the shape.Skittishness over past experience with HRSI tiles.The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
These aren't HRSI and are not in a debris shedding environment.
The moral arc of the universe is long, but it bends toward "Starship is Shuttle reincarnated." ;)No debris shedding on launch, but the structure and method for manufacture (described in one of the environmental docs for the Astronaut Blvd. site) are almost identical to HRSI: sintered pure silica fibres, reaction-cured Borosilicate glass coating, then impregnated with acetic acid & a waterproofing agent. The only change is the waterproofing agent (methyl-trimethoxy silane rather than dimethylethoxy silane) and the shape.Skittishness over past experience with HRSI tiles.The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
These aren't HRSI and are not in a debris shedding environment.
No debris shedding on launch, but the structure and method for manufacture (described in one of the environmental docs for the Astronaut Blvd. site) are almost identical to HRSI: sintered pure silica fibres, reaction-cured Borosilicate glass coating, then impregnated with acetic acid & a waterproofing agent. The only change is the waterproofing agent (methyl-trimethoxy silane rather than dimethylethoxy silane) and the shape.
I don't believe SpaceX is using PICA-X anywhere on Starship.No debris shedding on launch, but the structure and method for manufacture (described in one of the environmental docs for the Astronaut Blvd. site) are almost identical to HRSI: sintered pure silica fibres, reaction-cured Borosilicate glass coating, then impregnated with acetic acid & a waterproofing agent. The only change is the waterproofing agent (methyl-trimethoxy silane rather than dimethylethoxy silane) and the shape.
Not PICAX?
No sign of it so far (or SPAM). Using an ablator wouldn't match with their desire for rapid reuse with minimal refurbishment.No debris shedding on launch, but the structure and method for manufacture (described in one of the environmental docs for the Astronaut Blvd. site) are almost identical to HRSI: sintered pure silica fibres, reaction-cured Borosilicate glass coating, then impregnated with acetic acid & a waterproofing agent. The only change is the waterproofing agent (methyl-trimethoxy silane rather than dimethylethoxy silane) and the shape.
Not PICAX?
Note also that tile inspection & repair became a topic for the Shuttle because of the unsolvable foam shredding problem of the External Tank. Fortunately, there is no ET for Starship.
Note also that tile inspection & repair became a topic for the Shuttle because of the unsolvable foam shredding problem of the External Tank. Fortunately, there is no ET for Starship.
No external tank, but a collision with a bird is still possible, it happens everyday around the world with airplanes.
Note also that tile inspection & repair became a topic for the Shuttle because of the unsolvable foam shredding problem of the External Tank. Fortunately, there is no ET for Starship.
No external tank, but a collision with a bird is still possible, it happens everyday around the world with airplanes.
I think the biggest cause for an orbital shield inspection is reactionary- that is, if the crew reports a sharp impact and slew, (a debris strike), there should be onboard means to see if they should come home, or wait for rescue.
I think that might have been regarding MMOD once in orbit. Accelerometers/microphones attached to the structure would likely pick up any significant impact and for birds during launch you would also have ground imagery.I think the biggest cause for an orbital shield inspection is reactionary- that is, if the crew reports a sharp impact and slew, (a debris strike), there should be onboard means to see if they should come home, or wait for rescue.
A 1 kg bit of debris is not going to slew a 5,000,000 kg rocket. And crew won't hear much of anything over the 33 Raptors burning 100 m away.
Well, MMOD on orbit isn’t going to produce any noticeable signal or sensation to the crew. They won’t hear, see, or feel anything. But cryo-proofed microphones inside the tanks and attached to the steel inner skin would definitely be able to pick up the “ping” from an MMOD strike to the heat shield. They would probably be able to triangulate it as well.I think that might have been regarding MMOD once in orbit. Accelerometers/microphones attached to the structure would likely pick up any significant impact and for birds during launch you would also have ground imagery.I think the biggest cause for an orbital shield inspection is reactionary- that is, if the crew reports a sharp impact and slew, (a debris strike), there should be onboard means to see if they should come home, or wait for rescue.
A 1 kg bit of debris is not going to slew a 5,000,000 kg rocket. And crew won't hear much of anything over the 33 Raptors burning 100 m away.
Tiles can potentially break or come off on ascent so debris could be an issue.
MMOD damage would seem to be the most serious potential issue that would require inspection on orbit.
The worst-case scenario would be a low-angle hypervelocity impact that shreds several tiles in a row and sends shrapnel from those tiles into adjacent tiles.
MMOD damage would seem to be the most serious potential issue that would require inspection on orbit.
No, it isn't an issue.
Interesting. Is this because it is deemed statistically unlike to happen in the time frame of a flight, likely to be survivable, or something else? It certainly came to my (layman) mind.
There were notably less ASWS debris in orbit when shuttle was flying.
Interesting. Is this because it is deemed statistically unlike to happen in the time frame of a flight, likely to be survivable, or something else? It certainly came to my (layman) mind.
Did you know of any issues from it for the shuttle program?
Interesting. Is this because it is deemed statistically unlike to happen in the time frame of a flight, likely to be survivable, or something else? It certainly came to my (layman) mind.
Did you know of any issues from it for the shuttle program?
From memory I believe that one of the orbiters windows was hit by something - probably a fleck of paint. It didn't penetrate but I think the window had to be replaced.
Interesting. Is this because it is deemed statistically unlike to happen in the time frame of a flight, likely to be survivable, or something else? It certainly came to my (layman) mind.
Did you know of any issues from it for the shuttle program?
From memory I believe that one of the orbiters windows was hit by something - probably a fleck of paint. It didn't penetrate but I think the window had to be replaced.
Fair enough.I was referring to tiles. The radiators took damage too.
From memory I believe that one of the orbiters windows was hit by something - probably a fleck of paint. It didn't penetrate but I think the window had to be replaced.
Tiles can potentially break or come off on ascent so debris could be an issue.
No, debris isn't the issue, tiles coming off is. One doesn't worrying about secondary effects.
Because:The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
Because:The increasing number of unique tiles got me thinking about operations:
1. Anyone heard of an inspection protocol for the SS tiles in orbit? I guess it mostly matters for manned missions and since those will be a small fraction of total SS missions, it could be minimized.
Why is there a need to inspect on orbit?
1. The tiles critical to survival of the ship/astronauts
2. There are thousands of tiles and any one of them could fail on launch
3. We can actually do things now if one or more fail (this isn't the Shuttle)
Item 3 is the most important one. Starships will be relatively "plentiful" compared to the Shuttle. Instead of telling the crew on an injured ship "you're screwed" because there are so few shuttles and it takes a long time to get one ready to launch, SpaceX could fire up another SS for a rescue/repair in days.
Anyway, in thinking about this some more, the only time you'd need a dedicated inspection device that floats around the ship would be for joyrides, where the SS simply goes into orbit and returns to Earth. Every other SS mission will docking in LEO with another SS (tankers, etc.). So, you could simply have a couple of ultra high res cameras on an SS looking outwards, have the ascending SS approach and roll to expose the tiles to the cameras.
No, the tiles are critical to survival. The mineral wool alone is not a sufficient TPS, even if it were to be arbitrarily anchored above the tank skin without any penetrations. The RCG layer on the outside of the tiles does a lot of work reradiating the energy dumped into the tiles by the plasma, and the low density tile body avoids conducting heat to the backer. Without those, you have a moderate-at-best insulator and little re-radiation.Tiles can potentially break or come off on ascent so debris could be an issue.
No, debris isn't the issue, tiles coming off is. One doesn't worrying about secondary effects.
Tiles coming off isn't an issue unless the mineral wool layer also peels back exposing the stainless steel to plasma or intense IR.
Looking back through SNx tile damage pics, almost all the damaged tiles show the bracket is still intact.
The tile material is there to protect the bracket that holds down the mineral wool which protects the stainless steel.
Multiple layers have to fail in one spot in order to risk vehicle loss. As it should be for any well engineered vehicle.
Not sure what the multiple layers are at the flap edges, unless as someone mentioned above there's a metal layer below the tile. presumably a high temp metal.
ause:
1. The tiles critical to survival of the ship/astronauts
2. There are thousands of tiles and any one of them could fail on launch
3. We can actually do things now if one or more fail (this isn't the Shuttle)
No, the tiles are critical to survival. The mineral wool alone is not a sufficient TPS, even if it were to be arbitrarily anchored above the tank skin without any penetrations. The RCG layer on the outside of the tiles does a lot of work reradiating the energy dumped into the tiles by the plasma, and the low density tile body avoids conducting heat to the backer. Without those, you have a moderate-at-best insulator and little re-radiation.Tiles can potentially break or come off on ascent so debris could be an issue.
No, debris isn't the issue, tiles coming off is. One doesn't worrying about secondary effects.
Tiles coming off isn't an issue unless the mineral wool layer also peels back exposing the stainless steel to plasma or intense IR.
Looking back through SNx tile damage pics, almost all the damaged tiles show the bracket is still intact.
The tile material is there to protect the bracket that holds down the mineral wool which protects the stainless steel.
Multiple layers have to fail in one spot in order to risk vehicle loss. As it should be for any well engineered vehicle.
Not sure what the multiple layers are at the flap edges, unless as someone mentioned above there's a metal layer below the tile. presumably a high temp metal.
I’m happy to take your word for it, but it still prompts the further question: how large would a piece of debris need to be, traveling at a relative speed of eight or 9 km/s, to penetrate an entire tile?
That is not the way it happens. The micrometeoroid wouldn't last going through the top fused layer of the first tile.
You know what is used to collect micrometeoroids? Aerogel. Silica.
Wow, I hope those things are in a museum or at least in good care right now. If that's the first ever example of spacecraft radiators being holed by a high velocity impact it could be of historical importance, considering the eventuality of powering spacecraft with closed cycle heat engines and the tactical importance of radiators being a large target. I digress from the discussion by several decades though...
From memory I believe that one of the orbiters windows was hit by something - probably a fleck of paint. It didn't penetrate but I think the window had to be replaced.
I was referring to tiles. The radiators took damage too.
3. No, just as screwed if it is a lunar or mars mission.Is it? The tile system on Starship seems much more practical to carry a few spares in case an inspection discovers a problem returning home. And if more than one starship is returning from mars during a synod, it's plausable to dock and abandon an unsalvagable ship, spreading the payload and fuel among the other ships of the return fleet.
The big question is how likely is it that a tile will be broken v just have a small hole drilled through it? A 0.1 inch hole is one thing, a missing tile is something else entirely. Bigger debris that might supply enough energy to break a tile are less likely and might also puncture the surface of the tank below. So the inspect every tile and carry spares back up plan falls somewhere between "it doesn't matter" and "it won't work". Not sure how big this eventuality space is but it might be very small indeed.3. No, just as screwed if it is a lunar or mars mission.Is it? The tile system on Starship seems much more practical to carry a few spares in case an inspection discovers a problem returning home. And if more than one starship is returning from mars during a synod, it's plausable to dock and abandon an unsalvagable ship, spreading the payload and fuel among the other ships of the return fleet.
The big question is how likely is it that a tile will be broken v just have a small hole drilled through it? A 0.1 inch hole is one thing, a missing tile is something else entirely. Bigger debris that might supply enough energy to break a tile are less likely and might also puncture the surface of the tank below. So the inspect every tile and carry spares back up plan falls somewhere between "it doesn't matter" and "it won't work". Not sure how big this eventuality space is but it might be very small indeed.Not sure if it's a real problem but I'm less worried about debris than simply fatigue or other stresses causing tile(s) to crack. I'm not sure Shuttle didn't have some of that. I'm of the opinion inspection/repair will be very necessary.
[No, the tiles are critical to survival. The mineral wool alone is not a sufficient TPS,
True for thermal. What about mechanical? It's not a kind environment.[No, the tiles are critical to survival. The mineral wool alone is not a sufficient TPS,
Data?
Mineral wool, while very fragile, has a melting point of 1250-1450 degC depending on which kind.
All sorts here: https://www.amazon.com/Forge-Insulation/s?k=Forge+Insulation (https://www.amazon.com/Forge-Insulation/s?k=Forge+Insulation)
The front flaperons (or whatever they´re called this week) could be a source of high-speed turbulent airflow or debris which could damage the Starship TPS downstream.ISTM that if there is such a problem they would have discovered that withsimulations months ago.
True for thermal. What about mechanical? It's not a kind environment.[No, the tiles are critical to survival. The mineral wool alone is not a sufficient TPS,
Data?
Mineral wool, while very fragile, has a melting point of 1250-1450 degC depending on which kind.
All sorts here: https://www.amazon.com/Forge-Insulation/s?k=Forge+Insulation (https://www.amazon.com/Forge-Insulation/s?k=Forge+Insulation)
The front flaperons (or whatever they´re called this week) could be a source of high-speed turbulent airflow or debris which could damage the Starship TPS downstream.ISTM that if there is such a problem they would have discovered that withsimulations months ago.
Which way do you think that airflow goes after hitting the flaps? There's not really any TPS to damage on the lee side of the ship.
Ascent environment should be much gentler: the goal is to get out of the atmosphere as soon as possible and before significant acceleration.Which way do you think that airflow goes after hitting the flaps? There's not really any TPS to damage on the lee side of the ship.
During ascent it would primarily go straight down below the flaperons, along the edge of the TPS. There would also be shockwave effects travelling across the skin of the ship. SpaceX indubitably had their super-computers simulate the effects, but they will only get real data in flight, obviously.
Agreed. Max-Q is going to happen at either subsonic or low-supersonic speeds; not anywhere near enough to damage these tiles.During ascent it would primarily go straight down below the flaperons, along the edge of the TPS. There would also be shockwave effects travelling across the skin of the ship. SpaceX indubitably had their super-computers simulate the effects, but they will only get real data in flight, obviously.Ascent environment should be much gentler: the goal is to get out of the atmosphere as soon as possible and before significant acceleration.
Irrelevant. It does you no good whatsoever as a TPS if the mineral wool survives to >1000°C if it also does not act as an effective insulator and allows the steel behind it to also heat to >1000°C. That melting point is also for nice sedate conditions inside a furnace, not subjected to hypersonic plasma flow.[No, the tiles are critical to survival. The mineral wool alone is not a sufficient TPS,
Data?
Mineral wool, while very fragile, has a melting point of 1250-1450 degC depending on which kind.
All sorts here: https://www.amazon.com/Forge-Insulation/s?k=Forge+Insulation
Irrelevant. It does you no good whatsoever as a TPS if the mineral wool survives to >1000°C if it also does not act as an effective insulator and allows the steel behind it to also heat to >1000°C. That melting point is also for nice sedate conditions inside a furnace, not subjected to hypersonic plasma flow.[No, the tiles are critical to survival. The mineral wool alone is not a sufficient TPS,
Data?
Mineral wool, while very fragile, has a melting point of 1250-1450 degC depending on which kind.
All sorts here: https://www.amazon.com/Forge-Insulation/s?k=Forge+Insulation
If the wool alone were sufficient, then it would be far simpler to use just the wool, and sew it down to the surface with mineral fibre thread (such that no steel component protrudes above the wool) rather than bothering with tiles in the first place.
Irrelevant. It does you no good whatsoever as a TPS if the mineral wool survives to >1000°C if it also does not act as an effective insulator and allows the steel behind it to also heat to >1000°C. That melting point is also for nice sedate conditions inside a furnace, not subjected to hypersonic plasma flow.[No, the tiles are critical to survival. The mineral wool alone is not a sufficient TPS,
Data?
Mineral wool, while very fragile, has a melting point of 1250-1450 degC depending on which kind.
All sorts here: https://www.amazon.com/Forge-Insulation/s?k=Forge+Insulation
If the wool alone were sufficient, then it would be far simpler to use just the wool, and sew it down to the surface with mineral fibre thread (such that no steel component protrudes above the wool) rather than bothering with tiles in the first place.
Are you talking about losing a tile or a few tiles, or losing hundreds? Those are quite different cases. The flowstream will be different, as will the heat sinks.
To give you an idea of the insulation factor of rock wool, look at these ovens and the internal vs. external temperature on page 7 of this heater specification with the use of Watlow ceramic fiber. at 3 inches thick a 1200 degC chamber is about 190degC on the outside. BTU K factor of about 1.5.Insualtion vs. direct conduction (heater bonded to pad) and very low intensity radiation vs. via hypersonic plasma flow are two VERY different regimes. If you want to claim that mineral wool is suitable for TPS, then I would suggest finding some evidence for it, such as hypersonic wind-tunnel tests like those undergone for all existing and proposed TPS types.
https://thermalsolutionsoftexas.com/pdfs/heaters/specifications/heater-ceramic-high-temp.pdf
Since you are arguing against the very thing that InterestedEngineer said he was not suggesting in the part of the post you omitted to quote I will take your post to mean that high-temperature mineral wool can not be used as insulation in any high temperature applications and that its use on Starship is purely aesthetic in nature ;)To give you an idea of the insulation factor of rock wool, look at these ovens and the internal vs. external temperature on page 7 of this heater specification with the use of Watlow ceramic fiber. at 3 inches thick a 1200 degC chamber is about 190degC on the outside. BTU K factor of about 1.5.Insualtion vs. direct conduction (heater bonded to pad) and very low intensity radiation vs. via hypersonic plasma flow are two VERY different regimes. If you want to claim that mineral wool is suitable for TPS, then I would suggest finding some evidence for it, such as hypersonic wind-tunnel tests like those undergone for all existing and proposed TPS types.
https://thermalsolutionsoftexas.com/pdfs/heaters/specifications/heater-ceramic-high-temp.pdf
For example, that chart in that linked PDF shows performance for heating in the watts/square inch vs. peak temperature. The Watts/square inch range goes up to ~ 40, and shows the material is beyond safe operating limits at 1200°C above 12W/square inch. If it were to represent radiative heating for re-entry regimes, the chart would need to go to above 400 watts/square inch.
Merely having a melting point above 1200°C tells you nothing about its performance as a TPS for re-entry.
Only if you like making up imaginary strawmen to defeat rather than actual discourse.Since you are arguing against the very thing that InterestedEngineer said he was not suggesting in the part of the post you omitted to quote I will take your post to mean that high-temperature mineral wool can not be used as insulation in any high temperature applications and that its use on Starship is purely aesthetic in nature ;)To give you an idea of the insulation factor of rock wool, look at these ovens and the internal vs. external temperature on page 7 of this heater specification with the use of Watlow ceramic fiber. at 3 inches thick a 1200 degC chamber is about 190degC on the outside. BTU K factor of about 1.5.Insualtion vs. direct conduction (heater bonded to pad) and very low intensity radiation vs. via hypersonic plasma flow are two VERY different regimes. If you want to claim that mineral wool is suitable for TPS, then I would suggest finding some evidence for it, such as hypersonic wind-tunnel tests like those undergone for all existing and proposed TPS types.
https://thermalsolutionsoftexas.com/pdfs/heaters/specifications/heater-ceramic-high-temp.pdf
For example, that chart in that linked PDF shows performance for heating in the watts/square inch vs. peak temperature. The Watts/square inch range goes up to ~ 40, and shows the material is beyond safe operating limits at 1200°C above 12W/square inch. If it were to represent radiative heating for re-entry regimes, the chart would need to go to above 400 watts/square inch.
Merely having a melting point above 1200°C tells you nothing about its performance as a TPS for re-entry.
Even one tile is a large hole in the TPS that will result in local heating. Stainless Steel has a higher melting point than Aluminium alloys, but still not high enough to survive a large patch exposed with minimal protection (and the wool offers minimal protection without the tiles over the top). Remember that Starship is a monocoque design, the tank walls are the superstructure, and the vehicle is pressure stabilised. A hole compromises both of those, which is not good news for the dynamic high-load flip manoeuvre performed before landing.
Remember, it's no good just having the wool happily survive >1000°C glowing red hot while also allowing the steel behind it to heat up. It has one job as a TPS: to prevent the steel heating up. If it does not accomplish that, it is worthless as a TPS even if the wool itself survives (in nice sheets gently floating down above the debris cloud). Even the 'low' temperature ceramic fibre mats of STS had a metallic coating rather than just being bare wool to deal with radiant heating and convection. Contact conduction is not the primary heating method during entry, and conduction is where these types of ceramic fibre mats work as insulators.
[...]I agree that the mineral wool looks like it is a nice solution to multiple problems: It provides part of the thermal insulation, it is part of the mechanical attachment system for the tiles and it forms a barrier preventing hot gas from getting beneath the tiles.
The presence of a mineral wool backer is to reduce conduction of heat from the backside of the tiles, and allow for variance between the tile back surface and the tank outer wall (and to provide some 'preload' when latching the tiles internal metal frame the the stud-clips, so the tiles can be pressed 'in' ~a mm past the clip latch fingers, then released to seat the latches).
"A few tiles, no flow disruption" are two mutually exclusive statements. If a whole tile is gone and the underlaying mineral wool exposed, that's a major disruption to the TPS, not a small ignorable hole.
"A few tiles, no flow disruption" are two mutually exclusive statements. If a whole tile is gone and the underlaying mineral wool exposed, that's a major disruption to the TPS, not a small ignorable hole.
For example, that chart in that linked PDF shows performance for heating in the watts/square inch vs. peak temperature. The Watts/square inch range goes up to ~ 40, and shows the material is beyond safe operating limits at 1200°C above 12W/square inch. If it were to represent radiative heating for re-entry regimes, the chart would need to go to above 400 watts/square inch.
Merely having a melting point above 1200°C tells you nothing about its performance as a TPS for re-entry.
I also agree that it can not do the whole job by itself even if it is made from similar (or even identical) materials as the bulk of the tiles: It can not support the glass coating which provides the emissivity, chemical resistance/passivity and surface finish needed.
Indeed, going hotter will usually beat emissivity but it does become relevant when you want to operate as close to the material limits as possible. The chemical reactivity/passivity is regarding the resistance to attack by dissociated nitrogen and oxygen as well as the catalytic heat transfer (reactive species recombining on the surface). If you can handle the heat the other properties are more of a reuse 100+ times issue and unlikely to be that important in an emergency.I also agree that it can not do the whole job by itself even if it is made from similar (or even identical) materials as the bulk of the tiles: It can not support the glass coating which provides the emissivity, chemical resistance/passivity and surface finish needed.
emissivity is a bit overrated. In the Boltzmann equation, T is to the fourth power and emissivity is linear. I small increase in working temperature of the insulator will cover a lower emissivity quite easily.
SuperWool Xtra also has really good chemical resistance (possibly better than the tiles, for example with water). I'm pretty sure they have to use some nasty chemicals to make the tiles not absorb stuff like water from the surrounding environment.
But yeah, surface finish and robustness facing Max-Q, SuperWool Xtra isn't going to cut it at all. The "wool is a backup plan" only works on the way down *once*, you would not want to re-launch with missing tiles. I'd also be a bit worried about what happens when they drop from hypersonic to supersonic or barely subsonic on the way down with missing tiles, missing tiles might cause the surface to unravel like a zipper when the airflow starts impinging directly on the surface. Refurbishment would be more expensive than planned. That's what test flights are for.
Fixing missing tiles at the launchpad is easy, fortunately.
Even one tile is a large hole in the TPS that will result in local heating. Stainless Steel has a higher melting point than Aluminium alloys, but still not high enough to survive a large patch exposed with minimal protection (and the wool offers minimal protection without the tiles over the top). Remember that Starship is a monocoque design, the tank walls are the superstructure, and the vehicle is pressure stabilised. A hole compromises both of those, which is not good news for the dynamic high-load flip manoeuvre performed before landing.Your comment about STS mats having a metallic coating was a memory tickler for the grid overlay we've seen a couple of times on the SS matting. No impact on thermal properties but it might be a hint about mechanical properties.
Remember, it's no good just having the wool happily survive >1000°C glowing red hot while also allowing the steel behind it to heat up. It has one job as a TPS: to prevent the steel heating up. If it does not accomplish that, it is worthless as a TPS even if the wool itself survives (in nice sheets gently floating down above the debris cloud). Even the 'low' temperature ceramic fibre mats of STS had a metallic coating rather than just being bare wool to deal with radiant heating and convection. Contact conduction is not the primary heating method during entry, and conduction is where these types of ceramic fibre mats work as insulators.
Loosing a tile is definitely not a good thing and it's reasonable that the wool matting will give no thermal protection. BUT... How much impact the loss of one tile will have during the worst of EDL is an open question.Only if you like making up imaginary strawmen to defeat rather than actual discourse.Since you are arguing against the very thing that InterestedEngineer said he was not suggesting in the part of the post you omitted to quote I will take your post to mean that high-temperature mineral wool can not be used as insulation in any high temperature applications and that its use on Starship is purely aesthetic in nature ;)To give you an idea of the insulation factor of rock wool, look at these ovens and the internal vs. external temperature on page 7 of this heater specification with the use of Watlow ceramic fiber. at 3 inches thick a 1200 degC chamber is about 190degC on the outside. BTU K factor of about 1.5.Insualtion vs. direct conduction (heater bonded to pad) and very low intensity radiation vs. via hypersonic plasma flow are two VERY different regimes. If you want to claim that mineral wool is suitable for TPS, then I would suggest finding some evidence for it, such as hypersonic wind-tunnel tests like those undergone for all existing and proposed TPS types.
https://thermalsolutionsoftexas.com/pdfs/heaters/specifications/heater-ceramic-high-temp.pdf (https://thermalsolutionsoftexas.com/pdfs/heaters/specifications/heater-ceramic-high-temp.pdf)
For example, that chart in that linked PDF shows performance for heating in the watts/square inch vs. peak temperature. The Watts/square inch range goes up to ~ 40, and shows the material is beyond safe operating limits at 1200°C above 12W/square inch. If it were to represent radiative heating for re-entry regimes, the chart would need to go to above 400 watts/square inch.
Merely having a melting point above 1200°C tells you nothing about its performance as a TPS for re-entry.
The presence of a mineral wool backer is to reduce conduction of heat from the backside of the tiles, and allow for variance between the tile back surface and the tank outer wall (and to provide some 'preload' when latching the tiles internal metal frame the the stud-clips, so the tiles can be pressed 'in' ~a mm past the clip latch fingers, then released to seat the latches).
"A few tiles, no flow disruption" are two mutually exclusive statements. If a whole tile is gone and the underlaying mineral wool exposed, that's a major disruption to the TPS, not a small ignorable hole.
There is a reasonable chance that SX engineers are scratching their heads over just these points. They've got their models, now they need some real world data to see how good the models are. With how fast they move it's even money they have 2-3 alternatives in the bag.[...]I agree that the mineral wool looks like it is a nice solution to multiple problems: It provides part of the thermal insulation, it is part of the mechanical attachment system for the tiles and it forms a barrier preventing hot gas from getting beneath the tiles.
The presence of a mineral wool backer is to reduce conduction of heat from the backside of the tiles, and allow for variance between the tile back surface and the tank outer wall (and to provide some 'preload' when latching the tiles internal metal frame the the stud-clips, so the tiles can be pressed 'in' ~a mm past the clip latch fingers, then released to seat the latches).
"A few tiles, no flow disruption" are two mutually exclusive statements. If a whole tile is gone and the underlaying mineral wool exposed, that's a major disruption to the TPS, not a small ignorable hole.
I also agree that it can not do the whole job by itself even if it is made from similar (or even identical) materials as the bulk of the tiles: It can not support the glass coating which provides the emissivity, chemical resistance/passivity and surface finish needed.
However, I do believe that the margin between "zero refurbishment" and catastrophic failure is large enough (literally many hundreds of degrees as envy887 points out) that it should be possible to fit the loss of a single (or possibly a few) tile(s) in there.
SpaceX has designed the system from the ground up and that they decide the size and thickness of the tiles and the underlying felt. If Starship can not survive a tile loss with the current tile size - but could do it with tiles of say half the size - then they would have to be awfully confident in the probability of tile loss not to sacrifice a few days of installation time and one or two percent of payload mass just to be sure. It is worth noting that they have tried out even larger tiles than the current standard ones...
Any thought about TPS alignment on the nose cone inside the tent?Moving from top to bottom, the rows of tile studs are as follows:
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2048017;image
Any thought about TPS alignment on the nose cone inside the tent?I was just looking at the same thing but got ninja'd by sevenperforce ;) It looks like it follows on what we have seen before with studs in an inverted standard triangle pattern with most rows pointing "up" (red) and a few pointing "down" (green). We can see 38 rows with rows 1, 4, 7, 12, 16, 21 and 27 from the top being "down" with the pattern suggesting a seam with changing spacing above each "down" row. There is also a few missing studs along the center line of the image which might be the mid line of the nose cone: 2 triangles on row 8 and 1 triangle on rows 16 and 33. This might not be related to the heat shield directly but to allow for mounting/welding something on the inside at a later stage.
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2048017;image
The spacing of the "down" rows is about what I would expect for intervals where "dropping a tile" is necessary as the radius shrinks. Less frequently at the bottom, more frequently near the nose.It is interesting that there is a four-row followed by a three-row followed by a four-row. I wonder if that three-row and everything beneath is standard-hex and the ones above it are all tapered tiles or something. Or perhaps it is just how the math worked out.
I agree with previous posters that the down rows are.probably where we get pentagons flat-to-flat to let the tiling pattern slip to adjust to the new radius.
I also find the missing studs on the centerline interesting. My first thought was that we'd get custom tiles there to break up the horizontal channels, but the missing studs don't seem to match up with the "down" rows in the way I'd expect. I'll go with the "internal features on the centerline which require special support" suggestion for now.Are they approximately at the lift points? Because that’s a good reason to have a gap. Ultimately they will have to come up with a different way to lift for rapid reusability, but for now it seems that they are going to stick with the same internal-member lift point approach.
https://twitter.com/StarshipGazer/status/1420464483366051848
https://twitter.com/StarshipGazer/status/1420464483366051848
A lot going on these days. In the photos from StarShip Gazer we can see the nose cone starting to be covered in heat shielding material. But what exactly are they doing? The nose appears black (perhaps just paint or a whole new type of shielding?) and they are attaching felt on top of this black part of the nose cone. Are we seeing new materials or just the part before they attach tiles?
What appears to be paint might actually just be shadow due to the curvature. As for the felt it looks like its some sort of test and rather haphazard. Irregular patches almost as if they were going to use a giant form of paper mache in felt!https://twitter.com/StarshipGazer/status/1420464483366051848
A lot going on these days. In the photos from StarShip Gazer we can see the nose cone starting to be covered in heat shielding material. But what exactly are they doing? The nose appears black (perhaps just paint or a whole new type of shielding?) and they are attaching felt on top of this black part of the nose cone. Are we seeing new materials or just the part before they attach tiles?
The reflection of the door looks pretty faint, as if from a dark, non-metallic surface.What appears to be paint might actually just be shadow due to the curvature. As for the felt it looks like its some sort of test and rather haphazard. Irregular patches almost as if they were going to use a giant form of paper mache in felt!https://twitter.com/StarshipGazer/status/1420464483366051848 (https://twitter.com/StarshipGazer/status/1420464483366051848)
A lot going on these days. In the photos from StarShip Gazer we can see the nose cone starting to be covered in heat shielding material. But what exactly are they doing? The nose appears black (perhaps just paint or a whole new type of shielding?) and they are attaching felt on top of this black part of the nose cone. Are we seeing new materials or just the part before they attach tiles?
So there's definitely a straight horizontal seam. there also appears to be some diamond shaped tiles, though it also kinda looks like hex tiles that are just broken where there's a dimple in the skin.It sure looks like they have implemented several of our suggestions ;) Now we just have to wait for a better angle to settle the question about multiple tile types or just a few with gaps...
There's also that black liner inside the hinge, which is interesting.
The felt insulation looks very haphazard? they seem to be using some particularly small offcuts in places. waste not, want not?
Pics from Mary: https://forum.nasaspaceflight.com/index.php?topic=52398.msg2269074#msg2269074
Wild guess. They have a computer generated design of nose tiling. they divided the design in areas and cut the white felt in the shape of the areas. Perhaps the cutting was done by computer and included the holes of the attachment pins. Now they are applying the felt to the nose to test the fit. The patches are small because the felt is flat and needs to be stretched to match the curvature of the nose. Next step, they will have computer generated tiles for each felt area and they will test the fit of the tiles. As the entire process (cutting felt and cutting tiles) is computer generated, we may see a great variety of shapes. Possibly the tiles from each area are individually cut from material blanks matching the curvature of the nose (we saw precisely fitting tiles on the flaps) and they will prefer random shapes instead of trying to limit the variety of shapes of individual tiles on the nose. As I said, wild guess! But Taylor’s use a similar process when designing clothing…I was going to say "it all looks very haphazard" but I think there is method in the madness there. Looking at the photo above again in close up the felt areas mostly cover up to the edge and just beyond the studded areas. The odd shaped lines are probably due to the boundary line on the edge of the heat shield combined with other obstructions like the RCS vents. I assume they will just trim the excess felt after the tiles have been applied. It doesn't look as through the boundary line is going to be a neat "half way" demarcation line.
Wild guess. They have a computer generated design of nose tiling. they divided the design in areas and cut the white felt in the shape of the areas. Perhaps the cutting was done by computer and included the holes of the attachment pins. Now they are applying the felt to the nose to test the fit. The patches are small because the felt is flat and needs to be stretched to match the curvature of the nose. Next step, they will have computer generated tiles for each felt area and they will test the fit of the tiles. As the entire process (cutting felt and cutting tiles) is computer generated, we may see a great variety of shapes. Possibly the tiles from each area are individually cut from material blanks matching the curvature of the nose (we saw precisely fitting tiles on the flaps) and they will prefer random shapes instead of trying to limit the variety of shapes of individual tiles on the nose. As I said, wild guess! But Taylor’s use a similar process when designing clothing…
So there's definitely a straight horizontal seam. there also appears to be some diamond shaped tiles, though it also kinda looks like hex tiles that are just broken where there's a dimple in the skin.Closeups attached.
Indeed, going hotter will usually beat emissivity but it does become relevant when you want to operate as close to the material limits as possible. The chemical reactivity/passivity is regarding the resistance to attack by dissociated nitrogen and oxygen as well as the catalytic heat transfer (reactive species recombining on the surface). If you can handle the heat the other properties are more of a reuse 100+ times issue and unlikely to be that important in an emergency.I also agree that it can not do the whole job by itself even if it is made from similar (or even identical) materials as the bulk of the tiles: It can not support the glass coating which provides the emissivity, chemical resistance/passivity and surface finish needed.
emissivity is a bit overrated. In the Boltzmann equation, T is to the fourth power and emissivity is linear. I small increase in working temperature of the insulator will cover a lower emissivity quite easily.
SuperWool Xtra also has really good chemical resistance (possibly better than the tiles, for example with water). I'm pretty sure they have to use some nasty chemicals to make the tiles not absorb stuff like water from the surrounding environment.
But yeah, surface finish and robustness facing Max-Q, SuperWool Xtra isn't going to cut it at all. The "wool is a backup plan" only works on the way down *once*, you would not want to re-launch with missing tiles. I'd also be a bit worried about what happens when they drop from hypersonic to supersonic or barely subsonic on the way down with missing tiles, missing tiles might cause the surface to unravel like a zipper when the airflow starts impinging directly on the surface. Refurbishment would be more expensive than planned. That's what test flights are for.
Fixing missing tiles at the launchpad is easy, fortunately.
The tiles are just made from insulation fibers that have been chopped up and sintered together - Shuttle tiles were made from pure silica or silica with some aluminoborosilicate and you might be able to do it with a similar composition to SuperWool (silica, alumina and potassium oxide with a bit of other oxides) although I would not be surprised if that mix is designed to prevent the fibers from sticking together at high temperatures.
The problem with water is not chemical, the large surface area just means that significant amount of water can be adsorbed from perspiration or atmospheric moisture. This increases the TPS mass and risks fracturing tiles during cold/hot cycles. How they have (or intend to) solve this problem is actually one of the things I am most curious about!
Yep lots of broken tiles. maybe this is just a practice nosecone?also, note the studs on the windward side of the fin fairing. No studs at the transition, though.
Photo from Mary
https://forum.nasaspaceflight.com/index.php?topic=52398.msg2269397#msg2269397
While having a closer look at all the broken tiles on the nosecone picture taken by Mary (BocaChicaGal), linked below, I saw what I though was a small sized tile in freefall roughly below the work platform beside the nosecone.
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2049191;image
What do you think?
Am I seeing things?
That would be the worst case scenario as the waterproofing on the Shuttle burnt off during reentry and required each individual tile to be injected with 2ml of dimethylethoxysilane by hand after each flight. That would probably take about as long as installing the tiles in the first place...[...]
The problem with water is not chemical, the large surface area just means that significant amount of water can be adsorbed from perspiration or atmospheric moisture. This increases the TPS mass and risks fracturing tiles during cold/hot cycles. How they have (or intend to) solve this problem is actually one of the things I am most curious about!
Similar waterproofing as Shuttle used.
That would be the worst case scenario as the waterproofing on the Shuttle burnt off during reentry and required each individual tile to be injected with 2ml of dimethylethoxysilane by hand after each flight. That would probably take about as long as installing the tiles in the first place...[...]
The problem with water is not chemical, the large surface area just means that significant amount of water can be adsorbed from perspiration or atmospheric moisture. This increases the TPS mass and risks fracturing tiles during cold/hot cycles. How they have (or intend to) solve this problem is actually one of the things I am most curious about!
Similar waterproofing as Shuttle used.
Agreed, esp. about the labour intensive syringe injection of waterproofing. Shuttle tiles in the early days could be installed by an experienced installer at the rate of 1.8 tiles per person per week. Takes a while as there were between 28,000-32,000 tiles per orbiter vehicle in the early days. OV-102 Columbia was delivered to KSC with tile simulators installed in place of real tiles for the delivery/ferry flight atop a Shuttle Carrier Aircraft. The "zipper-effect" of tile loss was feared during delivery. But it works and works now-as that technology has been quite well developed by NASA. The goal is quick turnaround, but a more immediate goal is to get Starship/Starbooster off the ground I'm sure Elon and his posse' have quite a list of Starship "Block-II" ideas and I'd bet the farm that the Starship TPS is on that list.That would be the worst case scenario as the waterproofing on the Shuttle burnt off during reentry and required each individual tile to be injected with 2ml of dimethylethoxysilane by hand after each flight. That would probably take about as long as installing the tiles in the first place...[...]
The problem with water is not chemical, the large surface area just means that significant amount of water can be adsorbed from perspiration or atmospheric moisture. This increases the TPS mass and risks fracturing tiles during cold/hot cycles. How they have (or intend to) solve this problem is actually one of the things I am most curious about!
Similar waterproofing as Shuttle used.
No debris shedding on launch, but the structure and method for manufacture (described in one of the environmental docs for the Astronaut Blvd. site) are almost identical to HRSI: sintered pure silica fibres, reaction-cured Borosilicate glass coating, then impregnated with acetic acid & a waterproofing agent. The only change is the waterproofing agent (methyl-trimethoxy silane rather than dimethylethoxy silane) and the shape.
The felt doesn't look haphazard it looks like a AI derived mesh.I can't find it, but I saw on twitter a day or two ago that someone (supposedly) used CFD to create a render of what the heatshield might look like, and it matched SpaceX's current design perfectly.
And what does the full heat shield look like?The felt doesn't look haphazard it looks like a AI derived mesh.I can't find it, but I saw on twitter a day or two ago that someone (supposedly) used CFD to create a render of what the heatshield might look like, and it matched SpaceX's current design perfectly.
That would be the worst case scenario as the waterproofing on the Shuttle burnt off during reentry and required each individual tile to be injected with 2ml of dimethylethoxysilane by hand after each flight. That would probably take about as long as installing the tiles in the first place...[...]
The problem with water is not chemical, the large surface area just means that significant amount of water can be adsorbed from perspiration or atmospheric moisture. This increases the TPS mass and risks fracturing tiles during cold/hot cycles. How they have (or intend to) solve this problem is actually one of the things I am most curious about!
Similar waterproofing as Shuttle used.
And I think in general the difference between tiling over cryogenic tanks vs the Shuttle orbiter needs to be appreciated.
And what does the full heat shield look like?The felt doesn't look haphazard it looks like a AI derived mesh.I can't find it, but I saw on twitter a day or two ago that someone (supposedly) used CFD to create a render of what the heatshield might look like, and it matched SpaceX's current design perfectly.
And with most of the tiles missingAnd what does the full heat shield look like?The felt doesn't look haphazard it looks like a AI derived mesh.I can't find it, but I saw on twitter a day or two ago that someone (supposedly) used CFD to create a render of what the heatshield might look like, and it matched SpaceX's current design perfectly.
https://twitter.com/AlexSvanArt/status/1420773434305437698?s=20
Only shows the nose regretably
Or take a page out of the early days of Shuttle: use off-the-shelf Scotchguard. It was an effective spray-on waterproofing agent, but degraded the RTV silicone adhesive. Starship is using clips for almost all its tile coverage, so that's a nonissue there. DMES or other waterproofing agent injection can be reserved for the few areas with bonded tiles (so far, seen on the flap leading edges and pivot roots).Maybe the scotch guard can use a different vehicle? Surely the scotch guard itself isn't a solvent. It would be a great coup if it works.
The "squarish" tiles are what we call "pentagons" here. They are a "home plate" shape.
The felt doesn't look haphazard it looks like a AI derived mesh.I can't find it, but I saw on twitter a day or two ago that someone (supposedly) used CFD to create a render of what the heatshield might look like, and it matched SpaceX's current design perfectly.
Alot of people probably laughed at my post. I can't wait until the final production of the towers/catchers/etc are AI/generative driven for structure and manufacturing.
https://twitter.com/ErcXspace/status/1421455365867294722
Seems they need to take a slower ascent profile with the grid fins out. Has the side effect to reduce aero loads on the tiles in denser parts of the atmosphere.
To be honest I was worried they would stay in place at max Q. Still think they have some iterations with the TPS tiles ahead.
Also Elon confirmed that they are not foldable
Also gridfin discussion is offtopic
should it? The fins are pretty broad, and the face of the fins is mostly holes. Which face produces less drag is not immediately obvous.Also Elon confirmed that they are not foldable
Also gridfin discussion is offtopic
But they can be put vertical, which should minimize drag.
Two things...
1. They seem to be increasing the tile size depending on how high a tile is on the nosecone.
2. Square tiles. That's all.
Image credit to @BocaChicaGal with @NASASpaceflight
They probably start with the same size tile at the bottom of each section, and get *smaller* going up each section to fit the curvature. Then when they reset at the straight edges, the larger tiles starting again makes you think they're getting bigger going up.
They do! I have measured three different tile sizes in images, getting smaller towards the top and resetting at the edges
This is what I measured. Looks like three different sizes to me. There are six more tiles below to the next edge so three tiles per section fit
twitter.com/ringwatchers/status/1421674302173294594If you allow straight line seams and a few more tile types, this is the clean solution. Very nice.QuoteTwo things...
1. They seem to be increasing the tile size depending on how high a tile is on the nosecone.
2. Square tiles. That's all.
Image credit to @BocaChicaGal with @NASASpaceflight
https://twitter.com/madeinmurlough/status/1421750411921346564 (https://twitter.com/madeinmurlough/status/1421750411921346564)QuoteThey probably start with the same size tile at the bottom of each section, and get *smaller* going up each section to fit the curvature. Then when they reset at the straight edges, the larger tiles starting again makes you think they're getting bigger going up.
twitter.com/mr__pine/status/1421759231640879110QuoteThey do! I have measured three different tile sizes in images, getting smaller towards the top and resetting at the edges
https://twitter.com/mr__pine/status/1421774506742386690 (https://twitter.com/mr__pine/status/1421774506742386690)QuoteThis is what I measured. Looks like three different sizes to me. There are six more tiles below to the next edge so three tiles per section fit
If you allow straight line seams and a few more tile types, this is the clean solution. Very nice.Yes it did appear at first that straight lines were not allowed, but they are so yes 3 tile types and a few straight line runs seems to do the trick. Lets hope it works!
should it? The fins are pretty broad, and the face of the fins is mostly holes. Which face produces less drag is not immediately obvous.
If you allow straight line seams and a few more tile types, this is the clean solution. Very nice.Yes it did appear at first that straight lines were not allowed, but they are so yes 3 tile types and a few straight line runs seems to do the trick. Lets hope it works!
My best guess is that during peak re-entry, Starship won't be doing a pure belly-flop so much as a lifting-body re-entry, so there will be a significant angle of attack which will mean the plasma flow path is downward relative to latitudinal straight lines.If you allow straight line seams and a few more tile types, this is the clean solution. Very nice.Yes it did appear at first that straight lines were not allowed, but they are so yes 3 tile types and a few straight line runs seems to do the trick. Lets hope it works!
We were told that straight lines were to be avoided, to prevent hot gases gaining velocity in a long seam. That makes sense, but it now appears that latitudinal straight lines are fine.
I'm surprised, as I'd expect a Starship doing a belly-flop reentry would have streamlines going that way; but I'm happy to be wrong.
My best guess is that during peak re-entry, Starship won't be doing a pure belly-flop so much as a lifting-body re-entry, so there will be a significant angle of attack which will mean the plasma flow path is downward relative to latitudinal straight lines.If you allow straight line seams and a few more tile types, this is the clean solution. Very nice.Yes it did appear at first that straight lines were not allowed, but they are so yes 3 tile types and a few straight line runs seems to do the trick. Lets hope it works!
We were told that straight lines were to be avoided, to prevent hot gases gaining velocity in a long seam. That makes sense, but it now appears that latitudinal straight lines are fine.
I'm surprised, as I'd expect a Starship doing a belly-flop reentry would have streamlines going that way; but I'm happy to be wrong.
Very crude drawing of said re-entry and flow paths attached. You can see that longitudinal straight lines would be in the flow path but latitudinal ones are not.
Once Starship is through re-entry, it pitches farther forward to nearly a full belly-flop to achieve the highest possible drag and thus get the lowest terminal velocity before the kick-flip.
Oh, plasma will absolutely flow around the sides during re-entry. I mean that the flow path around the sides will be at an angle. If you look at the pattern of heat shield tiles "spilling" around the flaps, you'll see that it forms an oblique angle to the flap root axis.My best guess is that during peak re-entry, Starship won't be doing a pure belly-flop so much as a lifting-body re-entry, so there will be a significant angle of attack which will mean the plasma flow path is downward relative to latitudinal straight lines.
Very crude drawing of said re-entry and flow paths attached. You can see that longitudinal straight lines would be in the flow path but latitudinal ones are not.
Once Starship is through re-entry, it pitches farther forward to nearly a full belly-flop to achieve the highest possible drag and thus get the lowest terminal velocity before the kick-flip.
Why wouldn’t the plasma flow around the sides? Why would the flow be only vertical?
Oh, plasma will absolutely flow around the sides during re-entry. I mean that the flow path around the sides will be at an angle. If you look at the pattern of heat shield tiles "spilling" around the flaps, you'll see that it forms an oblique angle to the flap root axis.My best guess is that during peak re-entry, Starship won't be doing a pure belly-flop so much as a lifting-body re-entry, so there will be a significant angle of attack which will mean the plasma flow path is downward relative to latitudinal straight lines.
Very crude drawing of said re-entry and flow paths attached. You can see that longitudinal straight lines would be in the flow path but latitudinal ones are not.
Once Starship is through re-entry, it pitches farther forward to nearly a full belly-flop to achieve the highest possible drag and thus get the lowest terminal velocity before the kick-flip.
Why wouldn’t the plasma flow around the sides? Why would the flow be only vertical?
But this flow path will be at an angle to any latitudinal seams, which would seem to explain why they will be okay.
The tiles were falling off, so they taped them.You know perfectly well that those tapes are there before adhesive cures.
I know a guy who knows a guy and he told me.
Elon mentioned some time back that they were still considering doing transpirational cooling for specific high heat load locations. If this is still the case, the tip of the nose, and indeed specific areas on the leading edges of fins where we haven't seen studs, are likely spots.Interesting, but that would add a lot of complexity. As many said, probably SpaceX will add complexity only if the current design fails. But maybe the current design implies traspirational cooling.
This could mean they're intending to put a distribution manifold layer over the existing cone, and then attach the tiles to the outside of this, possibly still using studs.
A single-piece RCC nosecone seems more likely to me.Elon mentioned some time back that they were still considering doing transpirational cooling for specific high heat load locations. If this is still the case, the tip of the nose, and indeed specific areas on the leading edges of fins where we haven't seen studs, are likely spots.Interesting, but that would add a lot of complexity. As many said, probably SpaceX will add complexity only if the current design fails. But maybe the current design implies traspirational cooling.
This could mean they're intending to put a distribution manifold layer over the existing cone, and then attach the tiles to the outside of this, possibly still using studs.
Ship 20 emerges from the midbay! #starship
How many tiles are there ;)
We've just counted a flap - we get 778 or 777 depending on whether there's a little triangular tile up on the edge of the flap where it meets the hinge.
Or maybe 779... Just seen @AustinDeSisto's photo of the other flap...
Or more! Just spotted that the edges might be two tiles deep. More to come then!
I counted about 5,000 for the rest of the tank section of S20 plus or minus 200 tiles.
One thing about the flap-count is that we've counted the blank spots as well as the actual tiles.
5000 seems low to me... We'll have to count when there are some more photos of it...
On a lighter note- Folks are free to do what they want with their free time, but could someone please give me a valid reason why knowing the number of tiles on starship is of importance. How much time does it take to count tiles into the thousands?
Some tiles are getting placed on studs that have been welded to the steel skin. Other tiles are being placed on smooth steel with some kind of adhesive. With adhesive, it would seem that replacing a broken tile would be difficult because of adhesive build up. Is anyone familiar with the kind of adhesive that might be used in this situation, and whether it could be removed easily with a solvent?Shuttle had RTV and what became branded Gorrilla Glue (I know Scot Manley recently referenced the latter in a recent video). I might be forgetting others.
Also, tiles on the root section of the body flaps seem to have a filler between them while tiles on the face of the flap do not. Any reasons for this? Will a filler come later?
On a lighter note- Folks are free to do what they want with their free time, but could someone please give me a valid reason why knowing the number of tiles on starship is of importance. How much time does it take to count tiles into the thousands?
On a lighter note- Folks are free to do what they want with their free time, but could someone please give me a valid reason why knowing the number of tiles on starship is of importance. How much time does it take to count tiles into the thousands?
I’ll be the MOTO and point out # of tiles is a (pretty) unambiguous metric with which to calculate complexity/labor/cost of the heat shield.
Some tiles are getting placed on studs that have been welded to the steel skin. Other tiles are being placed on smooth steel with some kind of adhesive. With adhesive, it would seem that replacing a broken tile would be difficult because of adhesive build up. Is anyone familiar with the kind of adhesive that might be used in this situation, and whether it could be removed easily with a solvent?Shuttle had RTV and what became branded Gorrilla Glue (I know Scot Manley recently referenced the latter in a recent video). I might be forgetting others.
Also, tiles on the root section of the body flaps seem to have a filler between them while tiles on the face of the flap do not. Any reasons for this? Will a filler come later?
On a lighter note- Folks are free to do what they want with their free time, but could someone please give me a valid reason why knowing the number of tiles on starship is of importance. How much time does it take to count tiles into the thousands?
I’ll be the MOTO and point out # of tiles is a (pretty) unambiguous metric with which to calculate complexity/labor/cost of the heat shield.
Number of tiles is far from unambiguous in guessing complexity, labor, or cost here.
...
I'm trying to figure out how they get each of all of those tiles in the right place.The vast majority of tiles are installed onto machine welded mounting posts. It's a relatively small number that are glued on by hand. Alignment is taken care of before the first tiles is even taken out of the box.
I've tried something like this,
and a small error in final tile position here and a small error in final tile position there,
and soon the rows do not go straight around, but rather start to curve up,
and then down when a correction is attempted with the placement of later tiles.
For example, try to install roofing shingles (or floor tiles) just by laying them next to
each other, without any overall alignment guides and they will probably not go straight.
Experienced roofers can tell just by eyeballing the shingles, but that only comes with the experience.
There seems to be no pattern or markings on the starship they use for alignment purposes.
And then Spacex will place tiles that seem to wander up a diagonal on the side of the starship,
and later fill in on both sides, and they seem to all fit.
I've not seen any type of, for example, laser alignment tool or survey equipment.
I'm not seeing any kind of spacers being used to get uniform separation between tiles.
I'm not seeing any cutting or trimming of tiles.
Edited.
I'm trying to figure out how they get each of all of those tiles in the right place.
I've tried something like this,
and a small error in final tile position here and a small error in final tile position there,
and soon the rows do not go straight around, but rather start to curve up,
and then down when a correction is attempted with the placement of later tiles.
For example, try to install roofing shingles (or floor tiles) just by laying them next to
each other, without any overall alignment guides and they will probably not go straight.
Experienced roofers can tell just by eyeballing the shingles, but that only comes with the experience.
There seems to be no pattern or markings on the starship they use for alignment purposes.
And then Spacex will place tiles that seem to wander up a diagonal on the side of the starship,
and later fill in on both sides, and they seem to all fit.
I've not seen any type of, for example, laser alignment tool or survey equipment.
I'm not seeing any kind of spacers being used to get uniform separation between tiles.
I'm not seeing any cutting or trimming of tiles.
Edited.
I'm trying to figure out how they get each of all of those tiles in the right place.
I've tried something like this,
and a small error in final tile position here and a small error in final tile position there,
and soon the rows do not go straight around, but rather start to curve up,
and then down when a correction is attempted with the placement of later tiles.
For example, try to install roofing shingles (or floor tiles) just by laying them next to
each other, without any overall alignment guides and they will probably not go straight.
Experienced roofers can tell just by eyeballing the shingles, but that only comes with the experience.
There seems to be no pattern or markings on the starship they use for alignment purposes.
And then Spacex will place tiles that seem to wander up a diagonal on the side of the starship,
and later fill in on both sides, and they seem to all fit.
I've not seen any type of, for example, laser alignment tool or survey equipment.
I'm not seeing any kind of spacers being used to get uniform separation between tiles.
I'm not seeing any cutting or trimming of tiles.
Edited.
I'm trying to figure out how they get each of all of those tiles in the right place.
I've tried something like this,
and a small error in final tile position here and a small error in final tile position there,
and soon the rows do not go straight around, but rather start to curve up,
and then down when a correction is attempted with the placement of later tiles.
For example, try to install roofing shingles (or floor tiles) just by laying them next to
each other, without any overall alignment guides and they will probably not go straight.
Experienced roofers can tell just by eyeballing the shingles, but that only comes with the experience.
There seems to be no pattern or markings on the starship they use for alignment purposes.
And then Spacex will place tiles that seem to wander up a diagonal on the side of the starship,
and later fill in on both sides, and they seem to all fit.
I've not seen any type of, for example, laser alignment tool or survey equipment.
I'm not seeing any kind of spacers being used to get uniform separation between tiles.
I'm not seeing any cutting or trimming of tiles.
Edited.
The tiles go on studs. The studs are welded on by robotic arms which, when set up properly, will be locate them properly to a fraction of a millimeter.
I'm trying to figure out how they get each of all of those tiles in the right place.
I've tried something like this,
and a small error in final tile position here and a small error in final tile position there,
and soon the rows do not go straight around, but rather start to curve up,
and then down when a correction is attempted with the placement of later tiles.
For example, try to install roofing shingles (or floor tiles) just by laying them next to
each other, without any overall alignment guides and they will probably not go straight.
Experienced roofers can tell just by eyeballing the shingles, but that only comes with the experience.
There seems to be no pattern or markings on the starship they use for alignment purposes.
And then Spacex will place tiles that seem to wander up a diagonal on the side of the starship,
and later fill in on both sides, and they seem to all fit.
I've not seen any type of, for example, laser alignment tool or survey equipment.
I'm not seeing any kind of spacers being used to get uniform separation between tiles.
I'm not seeing any cutting or trimming of tiles.
Edited.
The tiles go on studs. The studs are welded on by robotic arms which, when set up properly, will be locate them properly to a fraction of a millimeter.
How do they control the contour of the tanks themselves? You can locate where the tiles ought to be in space, but what you are attaching them to are off tolerance.
I'm trying to figure out how they get each of all of those tiles in the right place.
I've tried something like this,
and a small error in final tile position here and a small error in final tile position there,
and soon the rows do not go straight around, but rather start to curve up,
and then down when a correction is attempted with the placement of later tiles.
For example, try to install roofing shingles (or floor tiles) just by laying them next to
each other, without any overall alignment guides and they will probably not go straight.
Experienced roofers can tell just by eyeballing the shingles, but that only comes with the experience.
There seems to be no pattern or markings on the starship they use for alignment purposes.
And then Spacex will place tiles that seem to wander up a diagonal on the side of the starship,
and later fill in on both sides, and they seem to all fit.
I've not seen any type of, for example, laser alignment tool or survey equipment.
I'm not seeing any kind of spacers being used to get uniform separation between tiles.
I'm not seeing any cutting or trimming of tiles.
Edited.
The tiles go on studs. The studs are welded on by robotic arms which, when set up properly, will be locate them properly to a fraction of a millimeter.
How do they control the contour of the tanks themselves? You can locate where the tiles ought to be in space, but what you are attaching them to are off tolerance.
So very little room for error, but hopefully very little room is still enough room.I'm trying to figure out how they get each of all of those tiles in the right place.
I've tried something like this,
and a small error in final tile position here and a small error in final tile position there,
and soon the rows do not go straight around, but rather start to curve up,
and then down when a correction is attempted with the placement of later tiles.
For example, try to install roofing shingles (or floor tiles) just by laying them next to
each other, without any overall alignment guides and they will probably not go straight.
Experienced roofers can tell just by eyeballing the shingles, but that only comes with the experience.
There seems to be no pattern or markings on the starship they use for alignment purposes.
And then Spacex will place tiles that seem to wander up a diagonal on the side of the starship,
and later fill in on both sides, and they seem to all fit.
I've not seen any type of, for example, laser alignment tool or survey equipment.
I'm not seeing any kind of spacers being used to get uniform separation between tiles.
I'm not seeing any cutting or trimming of tiles.
Edited.
The tiles go on studs. The studs are welded on by robotic arms which, when set up properly, will be locate them properly to a fraction of a millimeter.
How do they control the contour of the tanks themselves? You can locate where the tiles ought to be in space, but what you are attaching them to are off tolerance.
One thing to consider is that even if the body is slightly off shape, all the error in a local area will be in the same direction, and that globally, the amount of absolute error will change very slowly (since rapidly changing error is easily visible as bumps and dents). This means that although the tile mest may slide across the surface where it's slightly out of position, globally, the error gets absorbed through slight variations in tile spacing. You can think of it as projecting an ideal perfect mesh onto a slightly imperfect surface. So long as that surface is still "close enough" to the ideal surface, the projected mesh will still be close to perfect. When placing the pins, you conceptually (the actual algoritm the machine uses might be slightly different, but it's the same idea) start a bit outside the absolute mesh position, then move inward until you reach the surface, which might be a few milimeters in front of or behind where it was supposed to be, but is still good enough.
Special care still has to be taken in certain locations, such as around the areas where the flaps interface with the body. These cannot tolerate error relative to the actual shape. The simplest solution here is to measure the absolute location of these places as the rocket sits on the assembly stand, then feed this information into a computer solver, which figures out how to distort the target mesh a little bit to get a best fit where the critical points to line up with the measured physical error. The tweaked absolute mesh positions are then fed into the stud welding machine, which welds the studs accordingly.
Not exactly 100% accurate, but a quick artistic representation of Starship 20's nosecone heatshield, based on the latest pics we've seen. will update as soon as they're done with it and we have better pictures.
There's actually probably more room for error than it would seem. In the same way as a number of small errors can accumulate to a large error, a large error can be removed though a number of small local errors. The key is that they can position tiles in absolute space, rather than relative to nearby tiles, which removes the cumulative term.So very little room for error, but hopefully very little room is still enough room.I'm trying to figure out how they get each of all of those tiles in the right place.
I've tried something like this,
and a small error in final tile position here and a small error in final tile position there,
and soon the rows do not go straight around, but rather start to curve up,
and then down when a correction is attempted with the placement of later tiles.
For example, try to install roofing shingles (or floor tiles) just by laying them next to
each other, without any overall alignment guides and they will probably not go straight.
Experienced roofers can tell just by eyeballing the shingles, but that only comes with the experience.
There seems to be no pattern or markings on the starship they use for alignment purposes.
And then Spacex will place tiles that seem to wander up a diagonal on the side of the starship,
and later fill in on both sides, and they seem to all fit.
I've not seen any type of, for example, laser alignment tool or survey equipment.
I'm not seeing any kind of spacers being used to get uniform separation between tiles.
I'm not seeing any cutting or trimming of tiles.
Edited.
The tiles go on studs. The studs are welded on by robotic arms which, when set up properly, will be locate them properly to a fraction of a millimeter.
How do they control the contour of the tanks themselves? You can locate where the tiles ought to be in space, but what you are attaching them to are off tolerance.
One thing to consider is that even if the body is slightly off shape, all the error in a local area will be in the same direction, and that globally, the amount of absolute error will change very slowly (since rapidly changing error is easily visible as bumps and dents). This means that although the tile mest may slide across the surface where it's slightly out of position, globally, the error gets absorbed through slight variations in tile spacing. You can think of it as projecting an ideal perfect mesh onto a slightly imperfect surface. So long as that surface is still "close enough" to the ideal surface, the projected mesh will still be close to perfect. When placing the pins, you conceptually (the actual algoritm the machine uses might be slightly different, but it's the same idea) start a bit outside the absolute mesh position, then move inward until you reach the surface, which might be a few milimeters in front of or behind where it was supposed to be, but is still good enough.
Special care still has to be taken in certain locations, such as around the areas where the flaps interface with the body. These cannot tolerate error relative to the actual shape. The simplest solution here is to measure the absolute location of these places as the rocket sits on the assembly stand, then feed this information into a computer solver, which figures out how to distort the target mesh a little bit to get a best fit where the critical points to line up with the measured physical error. The tweaked absolute mesh positions are then fed into the stud welding machine, which welds the studs accordingly.
Elon mentioned some time back that they were still considering doing transpirational cooling for specific high heat load locations. If this is still the case, the tip of the nose, and indeed specific areas on the leading edges of fins where we haven't seen studs, are likely spots.Interesting, but that would add a lot of complexity. As many said, probably SpaceX will add complexity only if the current design fails. But maybe the current design implies traspirational cooling.
This could mean they're intending to put a distribution manifold layer over the existing cone, and then attach the tiles to the outside of this, possibly still using studs.
Could it be possible that they are using reinforced carbon-carbon for the tip of the nose? It would make some sense given that that's where peak heating is likely to be. That's where was used on the space shuttle afterall.STS also had it all along the leading edges of the wings comprised of 22 panels per wing, in addition to the nose cap for temps exceeding 1,260°C(2,300 °F). .
https://twitter.com/fael097/status/1422611449977970694QuoteNot exactly 100% accurate, but a quick artistic representation of Starship 20's nosecone heatshield, based on the latest pics we've seen. will update as soon as they're done with it and we have better pictures.
We know SpaceX at one point intended to use TUFROC
"No straight lines" was a made-up rule, or rather a rule we erroneously interpreted as having no possible exceptions instead of a mere guideline. Listen to Elon's interview with Tim Dodd and take step 1 of his 5-step process to heart.If I remember correctly there was an Elon Musk quote to the effect that they did not want straight lines for the plasma to be channeled through.
The tile horizontal lines follow the weld horizontal lines for the simple reason that both are constructed as conical segment approximations to the complex ideal surface. It's not surprising that the number of conical segments requires for the tiles to adequately approximate the surface is exactly the same as the number of conical segments required for the steel to adequately approximate the surface.
And of course there are practical benefits to aligning the conical segments. Conical-segment tiles will naturally lay better if they are being placed on a matching cone, and otherwise the weld lines would be particularly tricky spots, etc.
It is interesting that the sectioned tile scheme on this first ship is breaking one of the design rules we thought were set by Elon (no straight channels in the direction of expected reentry plasma flow).I think any entry angle significantly off 90 degrees will prevent plasma channeling through circumferential seams. There are no longitudinal seams.
What are the chances this was an early prototype decision to simplify the tiling and not a permanent choice? Maybe the gap is small enough or the entry attack angle is enough to avoid the plasma channeling. If angle of attack is a factor, how critical might this attack angle margin be?
We know SpaceX at one point intended to use TUFROCNo. There was a single connection between SpaceX and TUFROC: a Space Act Agreement for knowledge transfer of TPS technology, mentioned as one among many technologies that NASA were providing SpaceX information on. In addition, TUFROC is not some magical super-material as people seem to think it is: it's a sintered silica tile (as SpaceX are currently using, LI-900 in all but branding) with an RCC cap on top.
"Step 1: make your requirements less dumb.""No straight lines" was a made-up rule, or rather a rule we erroneously interpreted as having no possible exceptions instead of a mere guideline. Listen to Elon's interview with Tim Dodd and take step 1 of his 5-step process to heart.If I remember correctly there was an Elon Musk quote to the effect that they did not want straight lines for the plasma to be channeled through.
The tile horizontal lines follow the weld horizontal lines for the simple reason that both are constructed as conical segment approximations to the complex ideal surface. It's not surprising that the number of conical segments requires for the tiles to adequately approximate the surface is exactly the same as the number of conical segments required for the steel to adequately approximate the surface.
And of course there are practical benefits to aligning the conical segments. Conical-segment tiles will naturally lay better if they are being placed on a matching cone, and otherwise the weld lines would be particularly tricky spots, etc.
"No straight lines" was a made-up rule, or rather a rule we erroneously interpreted as having no possible exceptions instead of a mere guideline. Listen to Elon's interview with Tim Dodd and take step 1 of his 5-step process to heart.If I remember correctly there was an Elon Musk quote to the effect that they did not want straight lines for the plasma to be channeled through.
The tile horizontal lines follow the weld horizontal lines for the simple reason that both are constructed as conical segment approximations to the complex ideal surface. It's not surprising that the number of conical segments requires for the tiles to adequately approximate the surface is exactly the same as the number of conical segments required for the steel to adequately approximate the surface.
And of course there are practical benefits to aligning the conical segments. Conical-segment tiles will naturally lay better if they are being placed on a matching cone, and otherwise the weld lines would be particularly tricky spots, etc.
No straight path for hot gas to accelerate through the gaps
"No straight lines" was a made-up rule, or rather a rule we erroneously interpreted as having no possible exceptions instead of a mere guideline. Listen to Elon's interview with Tim Dodd and take step 1 of his 5-step process to heart.If I remember correctly there was an Elon Musk quote to the effect that they did not want straight lines for the plasma to be channeled through.
The tile horizontal lines follow the weld horizontal lines for the simple reason that both are constructed as conical segment approximations to the complex ideal surface. It's not surprising that the number of conical segments requires for the tiles to adequately approximate the surface is exactly the same as the number of conical segments required for the steel to adequately approximate the surface.
And of course there are practical benefits to aligning the conical segments. Conical-segment tiles will naturally lay better if they are being placed on a matching cone, and otherwise the weld lines would be particularly tricky spots, etc.
It was this tweet, in response to "why hexagons".QuoteNo straight path for hot gas to accelerate through the gaps
https://twitter.com/elonmusk/status/1107379727302451200?
"No straight lines" was a made-up rule, or rather a rule we erroneously interpreted as having no possible exceptions instead of a mere guideline. Listen to Elon's interview with Tim Dodd and take step 1 of his 5-step process to heart.If I remember correctly there was an Elon Musk quote to the effect that they did not want straight lines for the plasma to be channeled through.
The tile horizontal lines follow the weld horizontal lines for the simple reason that both are constructed as conical segment approximations to the complex ideal surface. It's not surprising that the number of conical segments requires for the tiles to adequately approximate the surface is exactly the same as the number of conical segments required for the steel to adequately approximate the surface.
And of course there are practical benefits to aligning the conical segments. Conical-segment tiles will naturally lay better if they are being placed on a matching cone, and otherwise the weld lines would be particularly tricky spots, etc.
It was this tweet, in response to "why hexagons".QuoteNo straight path for hot gas to accelerate through the gaps
https://twitter.com/elonmusk/status/1107379727302451200?
"No straight lines" was a made-up rule, or rather a rule we erroneously interpreted as having no possible exceptions instead of a mere guideline. Listen to Elon's interview with Tim Dodd and take step 1 of his 5-step process to heart.If I remember correctly there was an Elon Musk quote to the effect that they did not want straight lines for the plasma to be channeled through.
The tile horizontal lines follow the weld horizontal lines for the simple reason that both are constructed as conical segment approximations to the complex ideal surface. It's not surprising that the number of conical segments requires for the tiles to adequately approximate the surface is exactly the same as the number of conical segments required for the steel to adequately approximate the surface.
And of course there are practical benefits to aligning the conical segments. Conical-segment tiles will naturally lay better if they are being placed on a matching cone, and otherwise the weld lines would be particularly tricky spots, etc.
A third possibility. When Elon said no straight lines... he thought his would include circumferential and the ongoing R&D showed it weren't so. His statement of design goal still stands but the specific solution being noodled at the time proved to be overkill. He made the requirements less dumb."No straight lines" was a made-up rule, or rather a rule we erroneously interpreted as having no possible exceptions instead of a mere guideline. Listen to Elon's interview with Tim Dodd and take step 1 of his 5-step process to heart.If I remember correctly there was an Elon Musk quote to the effect that they did not want straight lines for the plasma to be channeled through.
The tile horizontal lines follow the weld horizontal lines for the simple reason that both are constructed as conical segment approximations to the complex ideal surface. It's not surprising that the number of conical segments requires for the tiles to adequately approximate the surface is exactly the same as the number of conical segments required for the steel to adequately approximate the surface.
And of course there are practical benefits to aligning the conical segments. Conical-segment tiles will naturally lay better if they are being placed on a matching cone, and otherwise the weld lines would be particularly tricky spots, etc.
It was this tweet, in response to "why hexagons".QuoteNo straight path for hot gas to accelerate through the gaps
https://twitter.com/elonmusk/status/1107379727302451200? (https://twitter.com/elonmusk/status/1107379727302451200?)
To my mind, there are two possibilities:
1) The SN20 layout is inconsistent with this tweet. This implies the rational/design changed, which is not crazy to imagine.
2) The SN20 layout is consistent with this tweet. Perhaps only vertical straight gaps matter? There are still non of those.
Agreed, this is what I mean by the first possibility - design changed, was less dumb. We see this all the time with Starship, so it's not that surprising.A third possibility. When Elon said no straight lines... he thought his would include circumferential and the ongoing R&D showed it weren't so. His statement of design goal still stands but the specific solution being noodled at the time proved to be overkill. He made the requirements less dumb."No straight lines" was a made-up rule, or rather a rule we erroneously interpreted as having no possible exceptions instead of a mere guideline. Listen to Elon's interview with Tim Dodd and take step 1 of his 5-step process to heart.If I remember correctly there was an Elon Musk quote to the effect that they did not want straight lines for the plasma to be channeled through.
The tile horizontal lines follow the weld horizontal lines for the simple reason that both are constructed as conical segment approximations to the complex ideal surface. It's not surprising that the number of conical segments requires for the tiles to adequately approximate the surface is exactly the same as the number of conical segments required for the steel to adequately approximate the surface.
And of course there are practical benefits to aligning the conical segments. Conical-segment tiles will naturally lay better if they are being placed on a matching cone, and otherwise the weld lines would be particularly tricky spots, etc.
It was this tweet, in response to "why hexagons".QuoteNo straight path for hot gas to accelerate through the gaps
https://twitter.com/elonmusk/status/1107379727302451200? (https://twitter.com/elonmusk/status/1107379727302451200?)
To my mind, there are two possibilities:
1) The SN20 layout is inconsistent with this tweet. This implies the rational/design changed, which is not crazy to imagine.
2) The SN20 layout is consistent with this tweet. Perhaps only vertical straight gaps matter? There are still non of those.
Or did some other SpaceX-TUFROC connection appear somewhere and I missed it?
No. There was a single connection between SpaceX and TUFROC: a Space Act Agreement for knowledge transfer of TPS technology, mentioned as one among many technologies that NASA were providing SpaceX information on.
In addition, TUFROC is not some magical super-material as people seem to think it is: it's a sintered silica tile (as SpaceX are currently using, LI-900 in all but branding) with an RCC cap on top.
Starship has a continued and recurring absence of RCC. Even high thermal load areas like the nose and flap edges have been tiled with the same totally-not-HRSI sintered silica tiles as the rest of the body.
How do we know SpaceX is using LI-900 sintered silica tiles, and more specifically 'totally-not-HRSI'. Are there visual clues?An environmental protection report (https://prodenv.dep.state.fl.us/DepNexus/public/electronic-documents/FLR000231449/facility!search) on the Astronaut Blvd. site (tile production site) described the raw materials and manufacturing process, matching the description for HRSI:
Sintered Silica fibre base, reaction-cured-glass coating, then Silane + Acetic acid waterproofing (methyl-trimethoxy silane rather than dimethylethoxy silane though).
New info from Jean Wright on the NSF livestream:I was thinking the same thing. Also, it looked like they were using red RTV adhesive for the nose cone, which can go up to 343C, or roughly aluminum. (Although the tiles being attached look thick and therefore insulating, like Shuttle tiles and not like the thinner tiles on most of the rest of the body, so the heat on thick-tile backside may not be a problem.)
She claims that the white blanket is apparently SIP (Stress/Strain Isolation Pad) made of Nomex felt.
However, according to Wikipedia: This white, flexible fabric offered protection at up to 371 °C (700 °F).
This is a temperature much closer to what aluminium can sustain than stainless steel, so it's a quite confusing choice of material in the context of this Elon's tweet:
https://twitter.com/elonmusk/status/1154194820929212419
Or she just misunderstood the question and thought that NSF guys were asking about the white blankets on the Shuttle?
New info from Jean Wright on the NSF livestream:I was thinking the same thing. Also, it looked like they were using red RTV adhesive for the nose cone, which can go up to 343C, or roughly aluminum. (Although the tiles being attached look thick and therefore insulating, like Shuttle tiles and not like the thinner tiles on most of the rest of the body, so the heat on thick-tile backside may not be a problem.)
She claims that the white blanket is apparently SIP (Stress/Strain Isolation Pad) made of Nomex felt.
However, according to Wikipedia: This white, flexible fabric offered protection at up to 371 °C (700 °F).
This is a temperature much closer to what aluminium can sustain than stainless steel, so it's a quite confusing choice of material in the context of this Elon's tweet:
https://twitter.com/elonmusk/status/1154194820929212419
Or she just misunderstood the question and thought that NSF guys were asking about the white blankets on the Shuttle?
But I think a lot of these decisions are made for sake of expediency. Also, it might be okay if the Nomex felt degrades on reentry.
(IF it's actually Nomex.)
Also, 370C is pretty high for aluminum. You lose the vast majority of aluminum's strength at 370C or even 343C whereas stainless retains most of its strength, so even still at the fabric or adhesive maximum temperatures, stainless is much stronger than aluminum.
Oh, also, in areas of the underside of the tank, you might have cryo propellant that could help keep the stainless cold. And the ullage gas will be transporting the very high heat away via convection in other areas, as well as the radiation others have mentioned (which becomes quite significant at ~800-1000C or so due to the fourth power of radiation). So that gives you a bit of resiliency to lost tiles.
The graph you posted is especially interesting when compared to Elon's claim that Stainless Steel can sustain 1 177 °C (1450 K / 2 150 °F).Another consideration, aside from loss of strength at temperature, is loss of strength after cooling as a result of changes in the metal due to annealing:
A 304L-type austenitic stainless steel was subjected to plate rolling at ambient temperature and at 573 K to total strains of 3 and then annealed at temperatures of 873, 973 and 1073 K. The structural changes during annealing were associated with the austenite reversal (for the cold rolled samples), recrystallization and grain growth, which depended significantly on the annealing temperature. The grain growth exponent of 4 and 5 was obtained after annealing at 973 K/1073 K for the cold and warm rolled samples, whereas very sluggish grain coarsening took place at 873 K....The grain coarsening during annealing was accompanied by gradual softening.
(Annealing behavior of a 304L stainless steel processed by large strain cold and warm rolling (https://www.sciencedirect.com/science/article/abs/pii/S0921509317302344))
People have wondered how these guys could have enough experience to do such a good job placing the tiles. It seems to me that there's been plenty of opportunity to practice this glue and fit process on the very complex shapes on the flaps.
Someone had to do those and I bet they have just spent the last few days in man-baskets placing tiles.
Another thought I had was does SpaceX have some limited ability to produce tiles in Boca Chica? And if so, how long is the production process? A few hours? They could be placing tiles and when they get to something that doesn't fit right a quick couple of pictures sent to Lisa the CAD girl, followed by a quick call and she has the water jet cutting a new shape 10 minutes later. Squirt it with some stuff, bake it and give it to Albert to run out to the rocket.
The odd missing tiles indicated to me that it wasn't quite a same day turnaround, though. By the time they had a replacement for the broken tile they'd moved the scaffolding to another area or whatever, since there are lots of little one-off gaps. I'm sure they'll get filled at some point, but that suggested to me that there was a lead time to getting a replacement.I doubt the missing tiles are missing due to not having enough tiles. More likely the pins were damaged or needed some sort of cleaning before the new tile was applied and they didn't have time. Also it looks like they just didn't have enough time as there are some largish areas with no tiles. Also some sort of special alignment procedure might be required for some of the edge cases - again out of time.
I still think refractory metal tiles are a good way to go. Niobium based alloys can go to same temperature as shuttle heatshield tiles, or 1260C or so.Remember that the temperature the tile surface can tolerate is fairly far down the list of important properties to act as a TPS (as long as it doesn't ablate before you complete entry). It's not much good having a TPS that can tolerate 1500K if it allows the structure behind it to also heat up to 1500K. In that regard, Niobium is annoyingly conductive. Workable if you have a 'hot-structure' vehicle, not so great if your structure is also a cryogenic tank wall or right next to squishy flammable meat-bags.
People have wondered how these guys could have enough experience to do such a good job placing the tiles. It seems to me that there's been plenty of opportunity to practice this glue and fit process on the very complex shapes on the flaps.There's also an army of veteran STS tile installers that could be hired to train current installers, at least for the RTV + felt technique.
Remember that the temperature the tile surface can tolerate is fairly far down the list of important properties to act as a TPS (as long as it doesn't ablate before you complete entry). It's not much good having a TPS that can tolerate 1500K if it allows the structure behind it to also heat up to 1500K. In that regard, Niobium is annoyingly conductive. Workable if you have a 'hot-structure' vehicle, not so great if your structure is also a cryogenic tank wall or right next to squishy flammable meat-bags.
maybe calm down and not overinterpret thingsYeah lets just chill, nobody really knows. But that doesn't stop people from inventing theories (ha!). My theory is the fit check is needed and they can't continue with other things like testing the booster and ship until its done.
The odd missing tiles indicated to me that it wasn't quite a same day turnaround, though. By the time they had a replacement for the broken tile they'd moved the scaffolding to another area or whatever, since there are lots of little one-off gaps. I'm sure they'll get filled at some point, but that suggested to me that there was a lead time to getting a replacement.Elon provides some evidence that the issue is lead time:
twitter.com/nicansuini/status/1423296366273462286QuoteAnyone have some spare tiles that SN20 can borrow? She’s a few short…
#Spacexnews #spacex #starbase #starship
https://twitter.com/elonmusk/status/1423387961362501634QuoteRemaining tiles are on their way!
People have wondered how these guys could have enough experience to do such a good job placing the tiles. It seems to me that there's been plenty of opportunity to practice this glue and fit process on the very complex shapes on the flaps.Brownsville, Texas by jet (Elon and SpaceX have a few) is only about 3 hours away from their Florida site and 4 hours away from their California site. Probably not worth trying to get another facility up and running unless they were already planning on it.
Someone had to do those and I bet they have just spent the last few days in man-baskets placing tiles.
Another thought I had was does SpaceX have some limited ability to produce tiles in Boca Chica? And if so, how long is the production process? A few hours? They could be placing tiles and when they get to something that doesn't fit right a quick couple of pictures sent to Lisa the CAD girl, followed by a quick call and she has the water jet cutting a new shape 10 minutes later. Squirt it with some stuff, bake it and give it to Albert to run out to the rocket.
People have wondered how these guys could have enough experience to do such a good job placing the tiles. It seems to me that there's been plenty of opportunity to practice this glue and fit process on the very complex shapes on the flaps.Brownsville, Texas by jet (Elon and SpaceX have a few) is only about 3 hours away from their Florida site and 4 hours away from their California site. Probably not worth trying to get another facility up and running unless they were already planning on it.
Someone had to do those and I bet they have just spent the last few days in man-baskets placing tiles.
Another thought I had was does SpaceX have some limited ability to produce tiles in Boca Chica? And if so, how long is the production process? A few hours? They could be placing tiles and when they get to something that doesn't fit right a quick couple of pictures sent to Lisa the CAD girl, followed by a quick call and she has the water jet cutting a new shape 10 minutes later. Squirt it with some stuff, bake it and give it to Albert to run out to the rocket.
The total weight of Shuttle’s tiles and TPS was about 8.5 tons. Assuming Starship is similar, and the SpaceX private jet has a payload capacity of about 2.8 tons, it takes just 3 flights to send all the tiles by jet. Or, about a third or a fourth of a Starship worth of tiles can be sent via SpaceX’s Gulfstream G550.
The odd missing tiles indicated to me that it wasn't quite a same day turnaround, though. By the time they had a replacement for the broken tile they'd moved the scaffolding to another area or whatever, since there are lots of little one-off gaps. I'm sure they'll get filled at some point, but that suggested to me that there was a lead time to getting a replacement.Elon provides some evidence that the issue is lead time:twitter.com/nicansuini/status/1423296366273462286QuoteAnyone have some spare tiles that SN20 can borrow? She’s a few short…
#Spacexnews #spacex #starbase #starship
https://twitter.com/elonmusk/status/1423387961362501634QuoteRemaining tiles are on their way!
So, how confident you think spacex are in the tps tiles if they pop off during transport back to the construction site?To me this does not bode very well, at least for early flights. If they are having tiles pop off moving a mile or 2 per hour on flat ground then I don't want too see how the perform during max q and reentry. Hopefully they can solve this issue in future iterations otherwise it calls into question the viability of Starship as a reusable vehicle
So, how confident you think spacex are in the tps tiles if they pop off during transport back to the construction site?To me this does not bode very well, at least for early flights. If they are having tiles pop off moving a mile or 2 per hour on flat ground then I don't want too see how the perform during max q and reentry. Hopefully they can solve this issue in future iterations otherwise it calls into question the viability of Starship as a reusable vehicle
What does Musk mean by machining? I thought the tiles were cast?I would guess that it means that one take a standard tile and machine/grind it until it fits?
What does Musk mean by machining? I thought the tiles were cast?I would guess that it means that one take a standard tile and machine/grind it until it fits?
They might just cut them with a band saw or similar and then give them their top black coating. Although there are a hundred or so special tiles there are probably only a few dozen special tile types.What does Musk mean by machining? I thought the tiles were cast?I would guess that it means that one take a standard tile and machine/grind it until it fits?
I didn't think the the hex tiles were a single layer, which would preclude that. Could have got that wrong though.
Maybe slightly different make up for shaped tiles? Probably all glued as well so they don't have to machine around a mounting bracket?
I didn't think the the hex tiles were a single layer, which would preclude that. Could have got that wrong though.What does Musk mean by machining? I thought the tiles were cast?I would guess that it means that one take a standard tile and machine/grind it until it fits?
Maybe slightly different make up for shaped tiles? Probably all glued as well so they don't have to machine around a mounting bracket?
I notice that on the untiled band between the nosecone and the cylindrical section there are mounting pins from the edges to the centre, but then a large space where there are no pins at all on the midpoint of that circumference.not sure if they still do this but they used to attach a counterweight to the cone when stacking to balance the weight of the folded fins. Those tabs might be where it's mounted and they just didn't have time to cut them off an install the tile pins.
Its a curious arrangement, especially with the odd bracket smack in the middle. Anyone knowledgeable with thoughts? Is there any clear reason to not
a) stud this section?
b) glue on tiles instead of clipping on?
Clearly there was no problem applying studs this far down the cone.
Picture captured from NSF livestream
What does Musk mean by machining? I thought the tiles were cast?From the EPA report on the tile production site: the sintered silica blanks are cast and fired, then a router used to mill them to the desired profile, then sliced in half thickness-wise to form two tiles. The RCG coating is then applied, followed by waterproofing.
Part 2:
https://youtu.be/SA8ZBJWo73EQuoteJoin me as I take a tour of SpaceX's Starbase facility with Elon Musk as our tour guide! This is part 2 of 3, so stay tuned, there's another one coming!
If you need some notes on this video with key points, check out our article - https://everydayastronaut.com/starbase-tour-and-interview-with-elon-musk/
Need a rundown on Starship? I've got you covered with our "Complete Guide to Starship"
//youtu.be/-8p2JDTd13k
00:00 - Intro
00:45 - Tent 1 // Raptors
05:00 - Failure and the Space Shuttle
08:35 - Launch Escape Systems
10:50 - Tent 2
13:00 - Heat Shield Talk
16:20 - 1st Orbital Test
26:26 - Tent 3 // Nose Cones
37:40 - S20 Nose Cone // Reentry
51:00 - 69.420
From updates
https://twitter.com/BottinPhilip/status/1424098154497064960
While everyone is making videos about how big the fully stacked Starship/Superheavy is I wanted to go into the design of the heat shield. I recorded this on Friday night and by Saturday morning It was already somewhat out of date.
It's not too bad, but @elonmusk revealed a few things I wish I'd known when he talked to @Erdayastronaut
Larger tiles are much more fragile: while individual tile cost may decrease*, the odds are high that cost per unit area will increase once wastage and more complex handling procedures are taken into account.Agree. Months ago I saw being mentioned that too large tiles may have the right oscillation frequency, that one that matches the vibrations of the vehicle.
* Unless a larger tile means you need to construct a brand new sintering oven.
Just recalling Tim's comment to Elon about "dragon scales" -- I wonder, is hexagonal the optimal default shape for most tiles? If they were naturally evolved dragon scales or pterodactyl scales, they wouldn't be hexagonal. I'm imagining they'd be elongated to match the direction of airflow, in a way that prevents them from being dislodged. Bird feathers tend to overlap each other. Should the tile area only included its attachment area, or could it extend somewhat beyond that?
Just recalling Tim's comment to Elon about "dragon scales" -- I wonder, is hexagonal the optimal default shape for most tiles? If they were naturally evolved dragon scales or pterodactyl scales, they wouldn't be hexagonal. I'm imagining they'd be elongated to match the direction of airflow, in a way that prevents them from being dislodged. Bird feathers tend to overlap each other. Should the tile area only included its attachment area, or could it extend somewhat beyond that?Overlapping tiles don't work for Starship, as it encounters flow in multiple directions: hypersonic to supersonic to subsonic belly-first during entry, and subsonic to supersonic to hypersonic nose-first during launch. Unless you add hinge points and actuators to every tile to allow the lapping orientation to change between launch and landing, one or the other of those flight regimes will be attempting to rip the tiles off sideways.
I wonder if they could be lapped (as in lap joint) so that there isn't a direct path between tiles while still having a flat outer profile. However I don't think that 2 half thickness layers behave the same as 1 full thickness layer.Just recalling Tim's comment to Elon about "dragon scales" -- I wonder, is hexagonal the optimal default shape for most tiles? If they were naturally evolved dragon scales or pterodactyl scales, they wouldn't be hexagonal. I'm imagining they'd be elongated to match the direction of airflow, in a way that prevents them from being dislodged. Bird feathers tend to overlap each other. Should the tile area only included its attachment area, or could it extend somewhat beyond that?Overlapping tiles don't work for Starship, as it encounters flow in multiple directions: hypersonic to supersonic to subsonic belly-first during entry, and subsonic to supersonic to hypersonic nose-first during launch. Unless you add hinge points and actuators to every tile to allow the lapping orientation to change between launch and landing, one or the other of those flight regimes will be attempting to rip the tiles off sideways.
Just recalling Tim's comment to Elon about "dragon scales" -- I wonder, is hexagonal the optimal default shape for most tiles? If they were naturally evolved dragon scales or pterodactyl scales, they wouldn't be hexagonal. I'm imagining they'd be elongated to match the direction of airflow, in a way that prevents them from being dislodged. Bird feathers tend to overlap each other. Should the tile area only included its attachment area, or could it extend somewhat beyond that?Overlapping tiles don't work for Starship, as it encounters flow in multiple directions: hypersonic to supersonic to subsonic belly-first during entry, and subsonic to supersonic to hypersonic nose-first during launch. Unless you add hinge points and actuators to every tile to allow the lapping orientation to change between launch and landing, one or the other of those flight regimes will be attempting to rip the tiles off sideways.
Larger tiles are much more fragile: while individual tile cost may decrease*, the odds are high that cost per unit area will increase once wastage and more complex handling procedures are taken into account.
* Unless a larger tile means you need to construct a brand new sintering oven.
Anyone figured out what the mesh is for?I don't want to be too quick to crap on anyone's idea, but...your use of "crazy" here might be an understatement.
Here's a crazy idea: The mesh transports any heat that gets through a tile (cracked or missing) horizontally, distributing the heat over a wider area. Would have to be a material that is highly conductive to heat. (e.g. not stainless steel)
Anyone figured out what the mesh is for?I don't want to be too quick to crap on anyone's idea, but...your use of "crazy" here might be an understatement.
Here's a crazy idea: The mesh transports any heat that gets through a tile (cracked or missing) horizontally, distributing the heat over a wider area. Would have to be a material that is highly conductive to heat. (e.g. not stainless steel)
A wire mesh is just about the worst possible material for transferring heat conductively. You need surface area to do that. There's a reason wire filaments are used in incandescent bulbs.
Here's a later pic of the tile marking from Mary. The red and green show a rough clustering.That's at least what I'm inclined to think. Just on elementary school logic red = bad, green = good, and no tape is an uninspected tile. If the thing in question they're testing is positioning, I wonder by what datum they're measuring said tile positions. You certainly can't just do each tile's location relative to the tiles next to it. Perhaps there are markings between the mounting pins.
Here's some total speculation. If the red is outside of positional tolerance and the green is good positioning this could be showing the robot arms variance at different reaches during pin install.
Or maybe red is off in the up and green in the down or something like that. Unmarked would be something the haven't got to yet or is good.
This is the Erc X rendering of parallel Starship prop transfer Elon retweeted with flame emojis.It looks to me like those tiles in the image were created by a lot of Photoshop transform/stretch/warp/clone operations on just a few tile patterns, to make straight tile images fit the curved nose cone. I see lots of warped repetitions of various "cracked" tile patterns. I would read nothing into this image about how tiles are expected to appear, it's just a poor job of cloning when you pixel peep it.
There seems to be a lot of tile cracking depicted on both ships as if that’s expected and normal. Is that expected?
Fwiw, my guess is:What about no cracks, good fit?
1. Ok = inspected, no problems found
2. Green tape = no cracks on tile, but bad/loose fit (maybe needs stud adjustment, or adjusting mounting holes; I'm guessing fixable without a new tile)
3. Red tape = tile cracked, needs replacement.
4. No marking = not yet inspected.
that's what ok meansNo tape = not inspected,
that's what ok meansNo tape = not inspected,
Red tape = replacement required
Green tape = adjustment required
how is "ok" indicated on the tiles?
I love this place so much.that's what ok meansNo tape = not inspected,
Red tape = replacement required
Green tape = adjustment required
how is "ok" indicated on the tiles?
Writing
Looking closely at this image, I can see many red-marked tiles with visible cracks. None of the green-marked tiles have visible cracks or damage, but many of them do look misaligned.That’s amazingly ugly, and difficult to understand:
My guess is that green means “loose” and red means “broken” and the rest are fine.
It does seem like a lot of inspection work. But when you consider that it took sixteen hours to replace a single Shuttle tile....
Basically the skin is stainless steel so is good at distributing (conducting) any hot point sources of heat leakage passing through the tiled surface. Then the inner surface of the skin is further cooled by sloshing remaining propellant.
Proper pin position + proper tile shape + kinematic coupling* = proper tile position + robustly-minimal stress.
But tlles are misaligned and broken, therefore... ???
-- Mispositioned pins or malformed tiles, hence misalignment?
-- Underconstrained kinematics, hence loose fits?
-- Overconstrained kinematics, hence stress and breakage?
-- Something else?
* A design with 3 pins in 3 grooves could work like a Maxwell coupling (https://en.wikipedia.org/wiki/Kinematic_coupling#Maxwell_coupling), tolerating misalignment (and differential thermal expansion) while providing rigid positioning without internal stress. (Bunch of pictures, lots of variants (https://www.google.com/search?q=maxwell+kinematic+coupling&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiSmIfimKXyAhWGahUIHQnVBzsQ_AUoAXoECAEQAw&biw=1378&bih=689))
Or maybe the rush to fit tiles meant they had to employ more tile fitters and some of them weren't as good as the others?Proper pin position + proper tile shape + kinematic coupling* = proper tile position + robustly-minimal stress.
But tlles are misaligned and broken, therefore... ???
-- Mispositioned pins or malformed tiles, hence misalignment?
-- Underconstrained kinematics, hence loose fits?
-- Overconstrained kinematics, hence stress and breakage?
-- Something else?
* A design with 3 pins in 3 grooves could work like a Maxwell coupling (https://en.wikipedia.org/wiki/Kinematic_coupling#Maxwell_coupling), tolerating misalignment (and differential thermal expansion) while providing rigid positioning without internal stress. (Bunch of pictures, lots of variants (https://www.google.com/search?q=maxwell+kinematic+coupling&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiSmIfimKXyAhWGahUIHQnVBzsQ_AUoAXoECAEQAw&biw=1378&bih=689))
I believe that we do "know" that this is a kinematic coupling that constrains the tile in a way which is tolerant of differential expansion of the tile and the steel. And in *theory* this should precisely constrain the tile and there should never be a "loose" fit.
In practice I'm afraid "tolerance stacking" has struck again, and they've found that the pins are sometimes slightly too big or the grooves are slightly too narrow or the grooves/pins are too far from their ideal positions -- resulting in tile cracking. Or else that the pins are sometimes too small or the grooves are too wide, resulting in an underconstrained tile aka "loose fit".
So it's another iterative round of design (and possibly expedient field repairs) to bring the tolerances back to what they should be.
If I had to guess, I'd expect (a) some slight pin errors on the stud welder, but that these are probably well understood, but (b) much more significant dimensional variance on the tiles, caused by relative humidity, temperature, variance in the kiln drying process, variance in the coating processes, etc. They'll have to figure out what is causing the dimensions to drift after machining and constrain it. Normal "manufacturing precise parts repeatably is hard" stuff.
(And, after hearing Elon Philosophy Of Manufacturing first-hand in the Everyday Astronaut interview, I'd suggest that Elon would say that if you're not throwing away a good # of tiles at this point, you're not trying hard enough to simplify tile manufacturing. No doubt they'll judiciously add back "just enough" complications to the tile bakery process to get the tolerances correct, without adding unnecessary complexity to control for factors that turn out not to matter enough. And Elon's tweet did mention "final tiles" in his things-left-to-do list. I'd interpreted that as "the remaining tiles", but it's also possible that many/some of these are "draft" tiles, and that there are further process improvements that will be made to yield the "final" (version of the) tiles.)
No. /JimAnyone figured out what the mesh is for?I don't want to be too quick to crap on anyone's idea, but...your use of "crazy" here might be an understatement.
Here's a crazy idea: The mesh transports any heat that gets through a tile (cracked or missing) horizontally, distributing the heat over a wider area. Would have to be a material that is highly conductive to heat. (e.g. not stainless steel)
A wire mesh is just about the worst possible material for transferring heat conductively. You need surface area to do that. There's a reason wire filaments are used in incandescent bulbs.
What's worse than crazy?
You ever participated in a creativity session? The point isn't to go directly to a solution to a problem, it's to go indirectly. And not veto someone's crazy idea, but think of it as a riff on the problem and like music creation, figure out what's behind the riff, or let it inspire your own riff.
The problem is heat getting through broken tiles impinges on a small surface area and there's no way to conduct the heat away, because the mineral wool and stainless steel are terrible at heat conduction. The hot spot ultimately damages the stainless steel tank to the point of failure. So how would one conduct the heat away from the hot spot?
The conductivity of tungsten is about 10x that of stainless steel, so the mesh area would have to be > 1/10th that of the stainless steel, and the pictures show the mesh is probably 1/100 area or less, so yeah, it's not the mesh. There's a tiny amount of heat conduction away, which is why I thought of the problem "what is a way to conduct heat away from a hot spot".
Having the entire bottom of the tile be a high temperature conductive metal (instead of just the 'Y' that we can see) might be a possible way to conduct the heat away from the hot spot, assuming the metal can slide over a nearby tiles' metal to create a point of contact for the conduction. (e.g. the dragon scales idea, but the scales are hidden behind the ceramic part of the tile).
Or maybe not possible. But worth thinking about, because parallel-to-the-surface heat conduction might mitigate hot spots enough that a few lost tiles don't matter.
Seems about right, but the variation in tile height (making steps on the surface) looks pretty large, which seems like it might be a symptom of a pin/tile interface design problem (unless the pin-length control is garbage). My guess is that they need to iterate the snap-on interface between the pins and the holes/grooves on the tiles.Proper pin position + proper tile shape + kinematic coupling* = proper tile position + robustly-minimal stress.
But tlles are misaligned and broken, therefore... ???
-- Mispositioned pins or malformed tiles, hence misalignment?
-- Underconstrained kinematics, hence loose fits?
-- Overconstrained kinematics, hence stress and breakage?
-- Something else?
* A design with 3 pins in 3 grooves could work like a Maxwell coupling (https://en.wikipedia.org/wiki/Kinematic_coupling#Maxwell_coupling), tolerating misalignment (and differential thermal expansion) while providing rigid positioning without internal stress. (Bunch of pictures, lots of variants (https://www.google.com/search?q=maxwell+kinematic+coupling&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiSmIfimKXyAhWGahUIHQnVBzsQ_AUoAXoECAEQAw&biw=1378&bih=689))
I believe that we do "know" that this is a kinematic coupling that constrains the tile in a way which is tolerant of differential expansion of the tile and the steel. And in *theory* this should precisely constrain the tile and there should never be a "loose" fit.
In practice I'm afraid "tolerance stacking" has struck again, and they've found that the pins are sometimes slightly too big or the grooves are slightly too narrow or the grooves/pins are too far from their ideal positions -- resulting in tile cracking. Or else that the pins are sometimes too small or the grooves are too wide, resulting in an underconstrained tile aka "loose fit".
So it's another iterative round of design (and possibly expedient field repairs) to bring the tolerances back to what they should be.
If I had to guess, I'd expect (a) some slight pin errors on the stud welder, but that these are probably well understood, but (b) much more significant dimensional variance on the tiles, caused by relative humidity, temperature, variance in the kiln drying process, variance in the coating processes, etc. They'll have to figure out what is causing the dimensions to drift after machining and constrain it. Normal "manufacturing precise parts repeatably is hard" stuff.
(And, after hearing Elon Philosophy Of Manufacturing first-hand in the Everyday Astronaut interview, I'd suggest that Elon would say that if you're not throwing away a good # of tiles at this point, you're not trying hard enough to simplify tile manufacturing. No doubt they'll judiciously add back "just enough" complications to the tile bakery process to get the tolerances correct, without adding unnecessary complexity to control for factors that turn out not to matter enough. And Elon's tweet did mention "final tiles" in his things-left-to-do list. I'd interpreted that as "the remaining tiles", but it's also possible that many/some of these are "draft" tiles, and that there are further process improvements that will be made to yield the "final" (version of the) tiles.)
When I watched a worker hammer a tile in repeatly using a mallet during the Dodd/Musk #2 interview, it struck me that they're not handling tolerances as well as they could.
Seems about right, but the variation in tile height (making steps on the surface) looks pretty large, which seems like it might be a symptom of a pin/tile interface design problem (unless the pin-length control is garbage). My guess is that they need to iterate the snap-on interface between the pins and the holes/grooves on the tiles.
Maybe add a part (no!) between the tiles and pins? -- But if so, then a very small, light, and simple part. Maybe something like a gadget made of springy steel sheet that is preinstalled and slides in a groove on the tile-side with a hole in it for a pin to snap into? Maybe put the snap-on interaction in the springy gadget and simplify the pins to something symmetric with a knob at the end? This would separate the pin snap-on requirement from tile-side mechanical contact and sliding mobility. Annealing in use and loss of springiness would be OK. Probably lots of options, and easy to prototype the geometries and motions. (Thinking while typing here.)
Fwiw, my guess is:A tile can have a bad fit and be cracked. The two might be connected and this would be good to know. None of the tiles have double marking so I'm guessing the two colors are marking variations of one problem.
1. Ok = inspected, no problems found
2. Green tape = no cracks on tile, but bad/loose fit (maybe needs stud adjustment, or adjusting mounting holes; I'm guessing "fixable without a new tile")
3. Red tape = tile cracked, needs replacement.
4. No marking = not yet inspected.
Looking closely at this image, I can see many red-marked tiles with visible cracks. None of the green-marked tiles have visible cracks or damage, but many of them do look misaligned.On close inspection, it's more complicated. Three down and one to the right of the circled tile there is black tape. There's black tape all over the place. Some red tape is short and at a diagonal but only on the periphery. Only a few of the red taped are cracked. I've attached another pic at higher resolution. It was cropped by Philip Bottin on Twitter without attribute.
(https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2051778;image)
My guess is that green means “loose” and red means “broken” and the rest are fine.
It does seem like a lot of inspection work. But when you consider that it took sixteen hours to replace a single Shuttle tile....
I wonder why there don't seem to be two types of studs. One that is fixed in place and two that allow expansion/contraction. It seems like that would allow better placement / alignment and a stronger hold. Just make the top center stud of every tile fixed.The pins are fixed but the "Y" thingie on the back of the tile is where the pins seat into slots. Same effect.
Looking closely at this image, I can see many red-marked tiles with visible cracks. None of the green-marked tiles have visible cracks or damage, but many of them do look misaligned.On close inspection, it's more complicated. Three down and one to the right of the circled tile there is black tape. There's black tape all over the place. Some red tape is short and at a diagonal but only on the periphery. Only a few of the red taped are cracked. I've attached another pic at higher resolution. It was cropped by Philip Bottin on Twitter without attribute.
(https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=52398.0;attach=2051778;image)
My guess is that green means “loose” and red means “broken” and the rest are fine.
It does seem like a lot of inspection work. But when you consider that it took sixteen hours to replace a single Shuttle tile....
On the extreme left is blue tape. I think I remember them using tan masking tape type stuff for holding them in place, but it might have been blue. Some of the black tape is covering glitches but not all, or at not visibly.
WHAT is going on here?
IIRC the plan is to add caulking between tiles. Probably the same stuff as the underlayment. In theory this should allow looser dimensional tolerance. If two tiles are expanding towards each other through a spot where manufacturing tolerances are stacking bad, the caulking would keep them from contacting and allow the thermal creep to push off in the opposite direction where hopefully the tolerances are stacking good. Unless the stacking gets stacked and there isn't enough room in any direction.Proper pin position + proper tile shape + kinematic coupling* = proper tile position + robustly-minimal stress.
But tlles are misaligned and broken, therefore... ???
-- Mispositioned pins or malformed tiles, hence misalignment?
-- Underconstrained kinematics, hence loose fits?
-- Overconstrained kinematics, hence stress and breakage?
-- Something else?
* A design with 3 pins in 3 grooves could work like a Maxwell coupling (https://en.wikipedia.org/wiki/Kinematic_coupling#Maxwell_coupling), tolerating misalignment (and differential thermal expansion) while providing rigid positioning without internal stress. (Bunch of pictures, lots of variants (https://www.google.com/search?q=maxwell+kinematic+coupling&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiSmIfimKXyAhWGahUIHQnVBzsQ_AUoAXoECAEQAw&biw=1378&bih=689))
I believe that we do "know" that this is a kinematic coupling that constrains the tile in a way which is tolerant of differential expansion of the tile and the steel. And in *theory* this should precisely constrain the tile and there should never be a "loose" fit.
In practice I'm afraid "tolerance stacking" has struck again, and they've found that the pins are sometimes slightly too big or the grooves are slightly too narrow or the grooves/pins are too far from their ideal positions -- resulting in tile cracking. Or else that the pins are sometimes too small or the grooves are too wide, resulting in an underconstrained tile aka "loose fit".
So it's another iterative round of design (and possibly expedient field repairs) to bring the tolerances back to what they should be.
If I had to guess, I'd expect (a) some slight pin errors on the stud welder, but that these are probably well understood, but (b) much more significant dimensional variance on the tiles, caused by relative humidity, temperature, variance in the kiln drying process, variance in the coating processes, etc. They'll have to figure out what is causing the dimensions to drift after machining and constrain it. Normal "manufacturing precise parts repeatably is hard" stuff.
(And, after hearing Elon Philosophy Of Manufacturing first-hand in the Everyday Astronaut interview, I'd suggest that Elon would say that if you're not throwing away a good # of tiles at this point, you're not trying hard enough to simplify tile manufacturing. No doubt they'll judiciously add back "just enough" complications to the tile bakery process to get the tolerances correct, without adding unnecessary complexity to control for factors that turn out not to matter enough. And Elon's tweet did mention "final tiles" in his things-left-to-do list. I'd interpreted that as "the remaining tiles", but it's also possible that many/some of these are "draft" tiles, and that there are further process improvements that will be made to yield the "final" (version of the) tiles.)
Sorry if this has been covered but I notice up the belly of SS the tiles seem to be broken into sections with two rows of half tiles giving a distinctive line throughout the heatshield.Lots of previous discussion on this, scroll up (way up).
Initially I thought this might be due to the tiles being fitted prior to stacking, however they don't seem to match the build process - so are this expansion joints?
I was surprised to see, that they had no special tool to apply the tiles. I would have assumed that they would have some vacuum holder, allowing them to place the tile, while making sure no bending during application could break the tile. I might have assumed that would have a tool, to make sure that the placement of the pins is optimal.The Musk process informed by an earlier over automation debacle: Smack en till it hurts. Then tell me what tool you need for the next one.
Since both would have been rather low tech, it came as a surprise seeing one man hammer with his hand on a tile, known to break easily.
They had red, green, and "ok" being put up simultaneously.And once you know that "white smudge at apex of hexagon" means "ok" in the longer-distance shots, you can see tiles marked "ok" pretty early on. Before the stacking, I think, though someone should dig through the archives to check.
I'm assuming heat shield tiles are on the critical path.Mass to orbit will become small & even more complicated architecture. Reentering without encountering a plasma is almost a sci-fi territory
Only things on the critical path are being worked.
Heat shield tiles are being worked.
I'm wondering, why not eliminate the part? That is, heat shield tiles.
Instead, for the first earth-inbound starships, have a tanker meet and refuel the inbound starship,
before the inbound starship reaches earth and use the inbound starship engines to slow the ship down,
eliminating the need for heat shield tiles.
Use early tankers that will be thrown away anyway.
Fuel and tankers will be plentiful.
This even seems less risky.
Continue developing the tiles.
But off the critical path.
Deploy them when they are ready.
And get to mars faster.
Or am I missing something?
This thread is probably only suitable for introducing this idea.
Any suggestion where it should go?
(I know, that's two risky risky questions in a row! :-))
I'm assuming heat shield tiles are on the critical path.
Only things on the critical path are being worked.
Heat shield tiles are being worked.
I'm wondering, why not eliminate the part? That is, heat shield tiles.
Instead, for the first earth-inbound starships, have a tanker meet and refuel the inbound starship,
before the inbound starship reaches earth and use the inbound starship engines to slow the ship down,
eliminating the need for heat shield tiles.
Use early tankers that will be thrown away anyway.
Fuel and tankers will be plentiful.
This even seems less risky.
Continue developing the tiles.
But off the critical path.
Deploy them when they are ready.
And get to mars faster.
Or am I missing something?
This thread is probably only suitable for introducing this idea.
Any suggestion where it should go?
(I know, that's two risky risky questions in a row! :-))
After observing tiles falling off the ship, I think color-coding the tiles that didn't fall off is superfluous. I don't understand it at all. Are they planning on "fixing" the tiles that didn't fall off? Aren't they ignoring the elephant in the room?
Ok, the tape is definitely some sort of pattern. Curtesy of /r/SpaceX Masterrace on Twitter.
Or am I missing something?You are missing that a full SS doesn't have 9km/s of deltaV. You've thrown away 8 tankers and burned up anyway.
Sorry if this has been covered but I notice up the belly of SS the tiles seem to be broken into sections with two rows of half tiles giving a distinctive line throughout the heatshield.Lots of previous discussion on this, scroll up (way up).
Initially I thought this might be due to the tiles being fitted prior to stacking, however they don't seem to match the build process - so are this expansion joints?
Short story is that the radius of a cone shrinks as you approach the tip. The horizonal gaps seem to be whether the hex tiles are allowed to "slip" past each other in order to accommodate the shrinking nose radius. (Or equivalently, where a smaller/larger/differently tapered set of tiles begins.). You'll notice that the vertical sides of the hexes shift their alignment above and below the horizontal gap.
Part 2:At 36:20 you can see stacks upon stacks of crates. At 36:50 you can see a crate open with tiles inside, and from 37:00 you can see empty crates next to the tile installers (which appear to be flat-packed or nested, so the full crates seen earlier must have been full of tiles) and crates up on the cherrypickers with the tile installer.
https://youtu.be/SA8ZBJWo73EQuoteJoin me as I take a tour of SpaceX's Starbase facility with Elon Musk as our tour guide! This is part 2 of 3, so stay tuned, there's another one coming!
If you need some notes on this video with key points, check out our article - https://everydayastronaut.com/starbase-tour-and-interview-with-elon-musk/
Need a rundown on Starship? I've got you covered with our "Complete Guide to Starship"
//youtu.be/-8p2JDTd13k
00:00 - Intro
00:45 - Tent 1 // Raptors
05:00 - Failure and the Space Shuttle
08:35 - Launch Escape Systems
10:50 - Tent 2
13:00 - Heat Shield Talk
16:20 - 1st Orbital Test
26:26 - Tent 3 // Nose Cones
37:40 - S20 Nose Cone // Reentry
51:00 - 69.420
That's interesting. The closeups of the pins seem to show that they have circle shaped tops, which isn't exactly the shape I'd expect for something sharp enough to poke through the backside of the tile.Yeah, not much point in getting too bent out of shape over tiles popping off. Yet.
But it makes me wonder if the "mill out the back" step was one of those "let's see if we can remove this step" experiments. It might have worked ok in the lab, but in the field misalignment when originally pushing in the pins might have caused enough stress when wiggling thing over to expose the actual metal rail to cause the tiles to crack.
This might be wide of the mark. But if my wild guess is correct, fixing the tile cracking might be as "simple" as restoring that tile machining step so that the tiles are aligned correctly on the pins at the start of the "push" and so damage doesn't occur.
OTOH, given that the tiles are intended to be infinitely reusable, it may be that some percentage of failure-on-installation is worth it in exchange for skipping an expensive machining step on a couple of thousand tiles.
That's interesting. The closeups of the pins seem to show that they have circle shaped tops, which isn't exactly the shape I'd expect for something sharp enough to poke through the backside of the tile.The sintered silica tiles are pretty friable, kind of like a fine XPS foam. You could poke into the uncoated portion of one with a determined finger.
Does anyone have a plausible explanation for why tiles end up at different distances from the skin?Probably lots of reasons some cumulative on some occasions. I would put my money on the three biggest ones being:
In other words, why do we see steps on the surface?!?!
I would have expected that this tolerance would be important and easy to keep pretty tight, but I would have been wrong.
Does anyone have a plausible explanation for why tiles end up at different distances from the skin?Probably lots of reasons some cumulative on some occasions. I would put my money on the three biggest ones being:
In other words, why do we see steps on the surface?!?!
I would have expected that this tolerance would be important and easy to keep pretty tight, but I would have been wrong.
minor variation in the pin orientation, they may not all be exactly perpendicular to the surface at all times and may not be exactly positioned with sufficient precision.
Slight distortion in the nose shape from the ideal conic form due to cumulative minor welding discrepancies.
Slight variation tile to tile in the depth and orientation of the fixing points
If pins fit in Y-oriented grooves (or short radially-aligned slots) then the mechanical constraints are such that lateral variations in position (of pins or slots) cannot cause binding. This narrows the possibilities for binding to eitherDoes anyone have a plausible explanation for why tiles end up at different distances from the skin?Probably lots of reasons some cumulative on some occasions. I would put my money on the three biggest ones being:
In other words, why do we see steps on the surface?!?!
I would have expected that this tolerance would be important and easy to keep pretty tight, but I would have been wrong.
minor variation in the pin orientation, they may not all be exactly perpendicular to the surface at all times and may not be exactly positioned with sufficient precision.
Slight distortion in the nose shape from the ideal conic form due to cumulative minor welding discrepancies.
Slight variation tile to tile in the depth and orientation of the fixing points
Some of the tiles seem to be off from the proper seated height by 5 or 10 mm. The tolerances on each component at much tighter than that, but if the pin and hole locations are out of tolerance by only a fraction of 1 mm they might bind up as they try to insert the tile over the pins and it wouldn't seat down all the way.
The solution is probably either to improve the manufacturing tolerances or change the tile/pin design to tolerate a less precise fit without binding.
Could they put the pins into the tile and cover the back with a slightly oversized hexagon of matting and then align and weld attach that as a unit to the ship and surrounding tiles?
Alternatively wait for the new longer form segments (more accurate alignment perhaps?) to be built into a nose cone and try again using refined attachment methods.
Does anyone have a plausible explanation for why tiles end up at different distances from the skin?Speculation: Blanket layers overlapping. Mesh creep. Damaged/misplaced pin. Misaligned 'Y' thingie on the tile. Bad Karma.
In other words, why do we see steps on the surface?!?!
I would have expected that this tolerance would be important and easy to keep pretty tight, but I would have been wrong.
The higher and lower tiles may simply be too much or too little fabric underneath. They just have to be more carefull when putting on the insulating blanket.
Speculation: Blanket layers overlapping. Mesh creep. Damaged/misplaced pin. Misaligned 'Y' thingie on the tile. Bad Karma.If the blankets are uniform (they must be, or SpaceX wouldn’t use them), then they can’t be a cm or so too thick or thin (and lumpy -- thick under one tile but not its neighbor).
It'd be good to have real info.
If the blankets are uniform (they must be, or SpaceX wouldn’t use them), then they can’t be a cm or so too thick or thin (and lumpy -- thick under one tile but not its neighbor).
I think cylindrical sections are just fundamentally easier (regular, etc) than conic sections.
I can't help but feel that 'tapeageddon' is a consequence of rushing the nosecone for the surge. The tank barrel sections have escaped such embellishment. Maybe they've just not inspected that far yet or inspection was done out of sight, before the tank was stacked.
They wouldn't use water, they'd use methane. And Elon has been wanting to do almost exactly this for some time; it's called "transpiration cooling". But the complexity and weight have been prohibitive so far.
This makes sense, especially with a very soft, low-density blanket. It could bunch up (compress from side to side) without getting much thicker, but then the compressed patch would be harder to push down against the surface. Even easier to overlook than an outright wrinkle.If the blankets are uniform (they must be, or SpaceX wouldn’t use them), then they can’t be a cm or so too thick or thin (and lumpy -- thick under one tile but not its neighbor).
No, but they can easily bunch up, especially since you are putting flat rectangular fabric over a comic section, and apparently pushing it manually over the pin array. So if you don't pull "tight enough" when you push the fabric over the pin you get a little wrinkle which eventually causes the tile to sit proud.
They wouldn't use water, they'd use methane. And Elon has been wanting to do almost exactly this for some time; it's called "transpiration cooling". But the complexity and weight have been prohibitive so far.
Water can provide about 3x as much cooling as methane per kg in this application, and hot spots are likely to occur far from where methane or LOX pools in tanks, including on fins, cargo volume, flanks and skirt. Internal radiation may be sufficient to dissipate heat from hot spots in large volumes, but supplementary switchable water cooling is a safer bet.
The water is dead mass. The methane is already present and has done work as hydraulic fluid and pressurant and doesn't require addition weight for tankage.
This trade has been studied. The result (at this point) is heat tiles.
It looks like the sheet has been laid in an approximate way with overlaps in places. Usually that sort of ceramic blanket has flexibility to be squashed.I think the answer to the problem of the ill fitting, overlapping matting might be to cut the matting in the same shapes as the new nosecone gores.
For complex curves eventually moulded sections could be manufactured to fit, including thicker sections etc if needed. This only makes sense as part of finalising those shapes, like the fairing to the top hinge of the flaps, etc. However curved sections for the nose make sense. Just slicing a bit off the roll will always be a compromise!
WRT the difficult of tiling the nosecone, I had a brainwave but I'm not sure if it's ever been seriously considered in the aerospace world. Instead of a surface with varying curvature, could you use two sections of a torus back to back? Then you'd be dealing with a more uniform curvature, where each strip of tiles could be identical to the last.
Is there some aerodynamic/buildability/other disadvantage to such a shape?
WRT the difficult of tiling the nosecone, I had a brainwave but I'm not sure if it's ever been seriously considered in the aerospace world. Instead of a surface with varying curvature, could you use two sections of a torus back to back? Then you'd be dealing with a more uniform curvature, where each strip of tiles could be identical to the last.
Is there some aerodynamic/buildability/other disadvantage to such a shape?
1. Nosecone is a pressure vessel for human starship and in the tip is lox header tank which is another pressure vessel, this shape is just bad for pressure vessels.
2. They just tiled a starship nosecone with no more problems than the rest of ship, where is this difficulty? Aren't you solving a problem that doesn't exist?
The size of the bayonet tip must be small enough to compress smaller than the slot. Once the slot is past the tip the bayonet clip is free to expand to capture the slot. To do this without play calls for close tolerances and replicability. Not that exotic a problem but this install calls for thousands of iterations on a surface with both variable shape and random variations from the ideal. It's not too surprising to see lateral movement, especially in a 'learn as you go' installation process.If pins fit in Y-oriented grooves (or short radially-aligned slots) then the mechanical constraints are such that lateral variations in position (of pins or slots) cannot cause binding. This narrows the possibilities for binding to eitherDoes anyone have a plausible explanation for why tiles end up at different distances from the skin?Probably lots of reasons some cumulative on some occasions. I would put my money on the three biggest ones being:
In other words, why do we see steps on the surface?!?!
I would have expected that this tolerance would be important and easy to keep pretty tight, but I would have been wrong.
minor variation in the pin orientation, they may not all be exactly perpendicular to the surface at all times and may not be exactly positioned with sufficient precision.
Slight distortion in the nose shape from the ideal conic form due to cumulative minor welding discrepancies.
Slight variation tile to tile in the depth and orientation of the fixing points
Some of the tiles seem to be off from the proper seated height by 5 or 10 mm. The tolerances on each component at much tighter than that, but if the pin and hole locations are out of tolerance by only a fraction of 1 mm they might bind up as they try to insert the tile over the pins and it wouldn't seat down all the way.
The solution is probably either to improve the manufacturing tolerances or change the tile/pin design to tolerate a less precise fit without binding.
1) What would seem to be an unnecessarily-constrained geometry (like pins in small holes rather than slots) or
2) A pin/tile incompatibility (crushed fiber-stuff?) that has nothing to do with pin placement or tile geometry.
cylindrical mesh braceDoes anyone have a plausible explanation for why tiles end up at different distances from the skin?Probably lots of reasons some cumulative on some occasions. I would put my money on the three biggest ones being:
In other words, why do we see steps on the surface?!?!
I would have expected that this tolerance would be important and easy to keep pretty tight, but I would have been wrong.
minor variation in the pin orientation, they may not all be exactly perpendicular to the surface at all times and may not be exactly positioned with sufficient precision.
Slight distortion in the nose shape from the ideal conic form due to cumulative minor welding discrepancies.
Slight variation tile to tile in the depth and orientation of the fixing points
They will have internal cameras in the interior volumes of starship to look for hot spots. If they added a payload tank with a few tonnes of water and a distributed array of solenoid controlled spray nozzles at some stand off distance from inner surface of Starship (like center pivot irrigators use) then they could reactively cool any hot spots caused by tile failures etc. That would give them a greater chance of exploring the entire re-entry profile and possibly allow the recovery of hardware to figure out what went wrong (or right). Wouldn't be too hard or time consuming to do, and might speed up Starship development process significantly.You realize what you're talking about is putting water lines, and even water spay nozzles inside a cryogenic storage tank, right? In the unlikely event that the system worked as intended and didn't suffer from a bunch of frozen and/or ruptured water lines, valves, etc., then you'd have a bunch of water droplets in your cryogenic propellant. Water ice is an interesting material in that its hardness is unusually sensitive to temperature. By the time you get into the cryogenic regime, its effectively just another mineral. You'd basically be dumping tons of sand into your propellant supply.
I wonder if a solution would be to mount a piece the blanket to the back of each tile rather than to the body of SS itself?Nifty idea. The backing pad could not extend beyond the tile itself or a slight misalignment would extend the pad into the space for the next pad install. Same problem, different root cause. The rope caulking we haven't heard much about lately would definitely be needed.
WRT the difficult of tiling the nosecone, I had a brainwave but I'm not sure if it's ever been seriously considered in the aerospace world. Instead of a surface with varying curvature, could you use two sections of a torus back to back? Then you'd be dealing with a more uniform curvature, where each strip of tiles could be identical to the last.The edge would allow the plasma an extreme close approach and act as a heat collection point even without the plasma issue.
Is there some aerodynamic/buildability/other disadvantage to such a shape?
They will have internal cameras in the interior volumes of starship to look for hot spots. If they added a payload tank with a few tonnes of water and a distributed array of solenoid controlled spray nozzles at some stand off distance from inner surface of Starship (like center pivot irrigators use) then they could reactively cool any hot spots caused by tile failures etc. That would give them a greater chance of exploring the entire re-entry profile and possibly allow the recovery of hardware to figure out what went wrong (or right). Wouldn't be too hard or time consuming to do, and might speed up Starship development process significantly.You realize what you're talking about is putting water lines, and even water spay nozzles inside a cryogenic storage tank, right? In the unlikely event that the system worked as intended and didn't suffer from a bunch of frozen and/or ruptured water lines, valves, etc., then you'd have a bunch of water droplets in your cryogenic propellant. Water ice is an interesting material in that its hardness is unusually sensitive to temperature. By the time you get into the cryogenic regime, its effectively just another mineral. You'd basically be dumping tons of sand into your propellant supply.
On top of that, this would add a massive amount of complexity for little long term benefit (I would argue no benefit, as I think the idea is sufficiently flawed as to be ... less than useful). They'll just keep trying until they get it right. It's the SpaceX way.
WRT the difficult of tiling the nosecone, I had a brainwave but I'm not sure if it's ever been seriously considered in the aerospace world. Instead of a surface with varying curvature, could you use two sections of a torus back to back? Then you'd be dealing with a more uniform curvature, where each strip of tiles could be identical to the last.
Is there some aerodynamic/buildability/other disadvantage to such a shape?
Yeah - I thought about that too. And anyway you cut it the additional complexity would be ludicrous for what in essence is just early engineering tests anyway. As long as they get some good pre-breakup telemetry, that should be good enough to help them move things along. The idea as presented had enough wrong with it, I figured I'd just hit the highlights and go home.They will have internal cameras in the interior volumes of starship to look for hot spots. If they added a payload tank with a few tonnes of water and a distributed array of solenoid controlled spray nozzles at some stand off distance from inner surface of Starship (like center pivot irrigators use) then they could reactively cool any hot spots caused by tile failures etc. That would give them a greater chance of exploring the entire re-entry profile and possibly allow the recovery of hardware to figure out what went wrong (or right). Wouldn't be too hard or time consuming to do, and might speed up Starship development process significantly.You realize what you're talking about is putting water lines, and even water spay nozzles inside a cryogenic storage tank, right? In the unlikely event that the system worked as intended and didn't suffer from a bunch of frozen and/or ruptured water lines, valves, etc., then you'd have a bunch of water droplets in your cryogenic propellant. Water ice is an interesting material in that its hardness is unusually sensitive to temperature. By the time you get into the cryogenic regime, its effectively just another mineral. You'd basically be dumping tons of sand into your propellant supply.
On top of that, this would add a massive amount of complexity for little long term benefit (I would argue no benefit, as I think the idea is sufficiently flawed as to be ... less than useful). They'll just keep trying until they get it right. It's the SpaceX way.
Even if it were cryogenic propellant, it’d be a terrible idea. Talk about pressure regulation issues! You have hot ullage gas you’d be spraying cold propellant into, having it splash off a wall where it was gaining heat /vaporizing on one side and simultaneously collapsing ullage pressure on parts of the spray that bounced off with little or no heating. Result would be rapid ullage pressure collapse at the beginning followed by rapid over pressurization…or possibly rapid cycling between the two. Recipe for rapid breakup on return.
Yeah - I thought about that too. And anyway you cut it the additional complexity would be ludicrous for what in essence is just early engineering tests anyway. As long as they get some good pre-breakup telemetry, that should be good enough to help them move things along. The idea as presented had enough wrong with it, I figured I'd just hit the highlights and go home.They will have internal cameras in the interior volumes of starship to look for hot spots. If they added a payload tank with a few tonnes of water and a distributed array of solenoid controlled spray nozzles at some stand off distance from inner surface of Starship (like center pivot irrigators use) then they could reactively cool any hot spots caused by tile failures etc. That would give them a greater chance of exploring the entire re-entry profile and possibly allow the recovery of hardware to figure out what went wrong (or right). Wouldn't be too hard or time consuming to do, and might speed up Starship development process significantly.You realize what you're talking about is putting water lines, and even water spay nozzles inside a cryogenic storage tank, right? In the unlikely event that the system worked as intended and didn't suffer from a bunch of frozen and/or ruptured water lines, valves, etc., then you'd have a bunch of water droplets in your cryogenic propellant. Water ice is an interesting material in that its hardness is unusually sensitive to temperature. By the time you get into the cryogenic regime, its effectively just another mineral. You'd basically be dumping tons of sand into your propellant supply.
On top of that, this would add a massive amount of complexity for little long term benefit (I would argue no benefit, as I think the idea is sufficiently flawed as to be ... less than useful). They'll just keep trying until they get it right. It's the SpaceX way.
Even if it were cryogenic propellant, it’d be a terrible idea. Talk about pressure regulation issues! You have hot ullage gas you’d be spraying cold propellant into, having it splash off a wall where it was gaining heat /vaporizing on one side and simultaneously collapsing ullage pressure on parts of the spray that bounced off with little or no heating. Result would be rapid ullage pressure collapse at the beginning followed by rapid over pressurization…or possibly rapid cycling between the two. Recipe for rapid breakup on return.
How about Ceramic Foam https://www.technicalfoamservices.co.uk/product/ceramic-filter-foam/ (https://www.technicalfoamservices.co.uk/product/ceramic-filter-foam/) for a more even liquid/gas disbursion? Light weight and heat resistant.The current tile base material is to the best of our knowledge a porous ceramic foam very similar to that used on the Space Shuttle. It is made from a jumble of cheramic fibers rather than by replicating the more homogeneous pore structure of a "standard" foam in order to minimize heat transfer by thermal radiation through the material.
I have not designed a complete set up in my mind but thing a thin Stainless Steal backing sheet with appropriate holes behind this (something like a kitchen calendar design) is a start. I am not sure how ullage gas or liquid would be fed but I am sure some bright Spacex engineer will work out a simple solution.
Are the current heat shield tiles porous?
IDk if this has been noteb before, but since the tiles on the nose cone tip are glued there isn't any blanket. So, do you think that the tiles in the tip are different (maybe thicker??) to account the lack of the blancket?At the nose interface the glued tiles are about the same thickness as clip-on tiles + blanket while there might be some tapering on the fins (which could just be due to higher heat loading at the hinge). We do not know if the glued tiles are the same composition as the clip-on ones but I do not expect two parallel processes unless it is absolutely necessary.
BTW now we know that the assumption that the tiles existed only to protect the blancket is false.
Do other adhesive with higher max temperature exist and are usable, or probably the will stick with thecurrent one?IDk if this has been noteb before, but since the tiles on the nose cone tip are glued there isn't any blanket. So, do you think that the tiles in the tip are different (maybe thicker??) to account the lack of the blancket?At the nose interface the glued tiles are about the same thickness as clip-on tiles + blanket while there might be some tapering on the fins (which could just be due to higher heat loading at the hinge). We do not know if the glued tiles are the same composition as the clip-on ones but I do not expect two parallel processes unless it is absolutely necessary.
BTW now we know that the assumption that the tiles existed only to protect the blancket is false.
I do not think we can tell if one system is better at insulating than the other - The glued tiles are only used on areas with small curvature/difficult geometry (which generally correspond to higher heating) but the clip-on tiles + blanket are used at the dorsal stagnation point/line.
One interesting point is that if the red glue is a RTV silicone adhesive like that used on the Shuttle then that will be the limiting part of the TPS and the hull temperature can then reach at most 300-320 °C in those areas. While still significantly more than the 175 °C limit for the Shuttle this is quite a bit lower than what the steel can take without any risk annealing and even further from the structural limits.
It's also interesting that the off-the-shelf RTV silicone adhesives that a quick google turned up also have a lower temperature limit of around -55 °C which would seem to preclude it being used on the outsides of the cryo tanks.IDk if this has been noteb before, but since the tiles on the nose cone tip are glued there isn't any blanket. So, do you think that the tiles in the tip are different (maybe thicker??) to account the lack of the blancket?<snip/>
BTW now we know that the assumption that the tiles existed only to protect the blancket is false.
One interesting point is that if the red glue is a RTV silicone adhesive like that used on the Shuttle then that will be the limiting part of the TPS and the hull temperature can then reach at most 300-320 °C in those areas.
<snip/>
The nose, where tiles are glued, is a sharp radius and one of the hottest point on EDL. With the header tank immediately behind them my thoughts turn to the temperature gradient they will face. The header should (WAG) be enough to keep the glue temps good, but that gradient. Wow.IDk if this has been noteb before, but since the tiles on the nose cone tip are glued there isn't any blanket. So, do you think that the tiles in the tip are different (maybe thicker??) to account the lack of the blancket?At the nose interface the glued tiles are about the same thickness as clip-on tiles + blanket while there might be some tapering on the fins (which could just be due to higher heat loading at the hinge). We do not know if the glued tiles are the same composition as the clip-on ones but I do not expect two parallel processes unless it is absolutely necessary.
BTW now we know that the assumption that the tiles existed only to protect the blancket is false.
I do not think we can tell if one system is better at insulating than the other - The glued tiles are only used on areas with small curvature/difficult geometry (which generally correspond to higher heating) but the clip-on tiles + blanket are used at the dorsal stagnation point/line.
One interesting point is that if the red glue is a RTV silicone adhesive like that used on the Shuttle then that will be the limiting part of the TPS and the hull temperature can then reach at most 300-320 °C in those areas. While still significantly more than the 175 °C limit for the Shuttle this is quite a bit lower than what the steel can take without any risk annealing and even further from the structural limits.
IIRC the RTV silicone used on Shuttle (RTV560, an off-the-shelf product) is specced down to -115°C. Addition-cure Silicones alone have a enormous range of properties that be achieved by varying the specific composition, and then you have condensation-cure Silicones and other curing methods (though HTV would not be directly applicable) so you have a lot of latitude to design a silicone mix with the properties you need.
That's interesting.It's also interesting that the off-the-shelf RTV silicone adhesives that a quick google turned up also have a lower temperature limit of around -55 °C which would seem to preclude it being used on the outsides of the cryo tanks.IDk if this has been noteb before, but since the tiles on the nose cone tip are glued there isn't any blanket. So, do you think that the tiles in the tip are different (maybe thicker??) to account the lack of the blancket?<snip/>
BTW now we know that the assumption that the tiles existed only to protect the blancket is false.
One interesting point is that if the red glue is a RTV silicone adhesive like that used on the Shuttle then that will be the limiting part of the TPS and the hull temperature can then reach at most 300-320 °C in those areas.
<snip/>
BTW, why a product that could be bought by everyone, and not customized is called "off the shelf"? It should be called "on[/iz] the shelf" IMO.
Here are some interesting results courtesy of Bing. Perhaps someone should try Google:
https://www.amazon.com/Technicqll-Temperature-Adhesive-Fireplace-Collectors/dp/B006U5K9EQ (https://www.amazon.com/Technicqll-Temperature-Adhesive-Fireplace-Collectors/dp/B006U5K9EQ)
https://www.sauereisen.com/ceramic-assembly/ (https://www.sauereisen.com/ceramic-assembly/)
Further...Here are some interesting results courtesy of Bing. Perhaps someone should try Google:
https://www.amazon.com/Technicqll-Temperature-Adhesive-Fireplace-Collectors/dp/B006U5K9EQ (https://www.amazon.com/Technicqll-Temperature-Adhesive-Fireplace-Collectors/dp/B006U5K9EQ)
https://www.sauereisen.com/ceramic-assembly/ (https://www.sauereisen.com/ceramic-assembly/)
All these are brittle ceramics.
Are you trying to make sense of the English language? Stick with rocket science - it's easier. ::)That's interesting.It's also interesting that the off-the-shelf RTV silicone adhesives that a quick google turned up also have a lower temperature limit of around -55 °C which would seem to preclude it being used on the outsides of the cryo tanks.IDk if this has been noteb before, but since the tiles on the nose cone tip are glued there isn't any blanket. So, do you think that the tiles in the tip are different (maybe thicker??) to account the lack of the blancket?<snip/>
BTW now we know that the assumption that the tiles existed only to protect the blancket is false.
One interesting point is that if the red glue is a RTV silicone adhesive like that used on the Shuttle then that will be the limiting part of the TPS and the hull temperature can then reach at most 300-320 °C in those areas.
<snip/>
BTW, why a product that could be bought by everyone, and not customized is called "off the shelf"? It should be called "on[/iz] the shelf" IMO.
Those contact points with missing tiles are probably electromagnetic contact points for the arms to grab the starship.
Or better, use a silicone adhesive that turns into a ceramic at high temperatures, for example:
3) Bonding to tile: Use a brittle (ceramic?) high temperature adhesive (see quoted post). Expect good adhesion to the porous ceramic tiles, rely on embedding of metal fibers to mechanically interlock the fiber layer with the ceramic layer. Maybe put some ceramic fiber in the adhesive. Maybe treat surfaces in the metal-fiber layer in some clever way before applying adhesive and tiles.
It's because you can literally take it off of a shelf from a store. If it were still there, you never decided to buy it. Kind of like saying how you got this sick roll of 301 stainless steel for free off the back of an unsupervised delivery truck in south Texas. Like taking 10 tons of candy from a baby!That's interesting.It's also interesting that the off-the-shelf RTV silicone adhesives that a quick google turned up also have a lower temperature limit of around -55 °C which would seem to preclude it being used on the outsides of the cryo tanks.IDk if this has been noteb before, but since the tiles on the nose cone tip are glued there isn't any blanket. So, do you think that the tiles in the tip are different (maybe thicker??) to account the lack of the blancket?<snip/>
BTW now we know that the assumption that the tiles existed only to protect the blancket is false.
One interesting point is that if the red glue is a RTV silicone adhesive like that used on the Shuttle then that will be the limiting part of the TPS and the hull temperature can then reach at most 300-320 °C in those areas.
<snip/>
BTW, why a product that could be bought by everyone, and not customized is called "off the shelf"? It should be called "on[/iz] the shelf" IMO.
The nose, where tiles are glued, is a sharp radius and one of the hottest point on EDL. With the header tank immediately behind them my thoughts turn to the temperature gradient they will face. The header should (WAG) be enough to keep the glue temps good, but that gradient. Wow.IDk if this has been noteb before, but since the tiles on the nose cone tip are glued there isn't any blanket. So, do you think that the tiles in the tip are different (maybe thicker??) to account the lack of the blancket?At the nose interface the glued tiles are about the same thickness as clip-on tiles + blanket while there might be some tapering on the fins (which could just be due to higher heat loading at the hinge). We do not know if the glued tiles are the same composition as the clip-on ones but I do not expect two parallel processes unless it is absolutely necessary.
BTW now we know that the assumption that the tiles existed only to protect the blancket is false.
I do not think we can tell if one system is better at insulating than the other - The glued tiles are only used on areas with small curvature/difficult geometry (which generally correspond to higher heating) but the clip-on tiles + blanket are used at the dorsal stagnation point/line.
One interesting point is that if the red glue is a RTV silicone adhesive like that used on the Shuttle then that will be the limiting part of the TPS and the hull temperature can then reach at most 300-320 °C in those areas. While still significantly more than the 175 °C limit for the Shuttle this is quite a bit lower than what the steel can take without any risk annealing and even further from the structural limits.
Edit: dwheeler raises a good point on minimum temps.
...why a product that could be bought by everyone, and not customized is called "off the shelf"? It should be called "on[/iz] the shelf" IMO.
Every time I visit this thread I wonder why an overlapping tile isn't used. Think half-lap or tongue-and-groove, like one might find in flooring. This would solve the groove issues and allow for both thermal expansion and more relaxed location tolerance.
The idea is so obvious that I am sure it was considered and dismissed. Tell me what obvious flaw I am missing?
John
The flow goes in two orthogonal directions, so that overlapping during ascent will be exactly wrong during descent. (Or vice versa.)That's fish- or dragon-scale. Half lapped would present a smooth surface.
This question actually comes up fairly regularly.
While tongue-and-groove does require a special "tongueless" row every so often to allow tile replacement, half-lap does not - assuming we aren't talking about a contact/interference fit (which I assume we are not for any of these schemes, including the current one, due to expansion issues).
These same gaps that prevent contact (where both half laps are something less than the nominal height) also provide an even more effective labyrinthine flow path than the current tile gaps.
BTW, I am assuming rectangular tiles (top laps on two adjacent sides, bottoms on other two) when considering the above issues. Other shapes get more complicated.
Every time I visit this thread I wonder why an overlapping tile isn't used. Think half-lap or tongue-and-groove, like one might find in flooring. This would solve the groove issues and allow for both thermal expansion and more relaxed location tolerance.
The idea is so obvious that I am sure it was considered and dismissed. Tell me what obvious flaw I am missing?
John
Not TUFROC.
TUFROC is HRSI tiles covered with an RCC cap. No SpaceX tile (either those on Starship now nor those seen previously) have had RCC caps. TUFROC was mentioned among a whole bunch of other TPS technologies as part of a Space Act Agreement, and for some bizarre reason it's been latched onto as some sort of perceived super-TPS for no apparent reason.
From the tile manufacture process description from the FDEP inspection document, SpaceX's tiles are almost identical to shuttle-era HRSI tiles, with the main compositional difference being a slightly different waterproofing agent, and the physical difference being the internal attachment frame.
FDEP Documents are here (https://prodenv.dep.state.fl.us/DepNexus/public/electronic-documents/FLR000231449/facility!search), go back in this thread ~ a year and a half (end of 2020) for discussion around them.Not TUFROC.
TUFROC is HRSI tiles covered with an RCC cap. No SpaceX tile (either those on Starship now nor those seen previously) have had RCC caps. TUFROC was mentioned among a whole bunch of other TPS technologies as part of a Space Act Agreement, and for some bizarre reason it's been latched onto as some sort of perceived super-TPS for no apparent reason.
From the tile manufacture process description from the FDEP inspection document, SpaceX's tiles are almost identical to shuttle-era HRSI tiles, with the main compositional difference being a slightly different waterproofing agent, and the physical difference being the internal attachment frame.
Ed,
Can you give a bit more background on the FDEP doc? Maybe a link? I’m just so surprised because I feel like it’s the first I’m hearing of this. It feels like it really went semi-unnoticed here (at least in this thread?).
FDEP Documents are here (https://prodenv.dep.state.fl.us/DepNexus/public/electronic-documents/FLR000231449/facility!search), go back in this thread ~ a year and a half (end of 2020) for discussion around them.Not TUFROC.
TUFROC is HRSI tiles covered with an RCC cap. No SpaceX tile (either those on Starship now nor those seen previously) have had RCC caps. TUFROC was mentioned among a whole bunch of other TPS technologies as part of a Space Act Agreement, and for some bizarre reason it's been latched onto as some sort of perceived super-TPS for no apparent reason.
From the tile manufacture process description from the FDEP inspection document, SpaceX's tiles are almost identical to shuttle-era HRSI tiles, with the main compositional difference being a slightly different waterproofing agent, and the physical difference being the internal attachment frame.
Ed,
Can you give a bit more background on the FDEP doc? Maybe a link? I’m just so surprised because I feel like it’s the first I’m hearing of this. It feels like it really went semi-unnoticed here (at least in this thread?).
FDEP Documents are here (https://prodenv.dep.state.fl.us/DepNexus/public/electronic-documents/FLR000231449/facility!search), go back in this thread ~ a year and a half (end of 2020) for discussion around them.Not TUFROC.
TUFROC is HRSI tiles covered with an RCC cap. No SpaceX tile (either those on Starship now nor those seen previously) have had RCC caps. TUFROC was mentioned among a whole bunch of other TPS technologies as part of a Space Act Agreement, and for some bizarre reason it's been latched onto as some sort of perceived super-TPS for no apparent reason.
From the tile manufacture process description from the FDEP inspection document, SpaceX's tiles are almost identical to shuttle-era HRSI tiles, with the main compositional difference being a slightly different waterproofing agent, and the physical difference being the internal attachment frame.
Ed,
Can you give a bit more background on the FDEP doc? Maybe a link? I’m just so surprised because I feel like it’s the first I’m hearing of this. It feels like it really went semi-unnoticed here (at least in this thread?).
Not TUFROC.
SpaceX's tiles are almost identical to shuttle-era HRSI tiles, with the main compositional difference being a slightly different waterproofing agent, and the physical difference being the internal attachment frame.
FDEP Documents are here (https://prodenv.dep.state.fl.us/DepNexus/public/electronic-documents/FLR000231449/facility!search), go back in this thread ~ a year and a half (end of 2020) for discussion around them.Not TUFROC.
TUFROC is HRSI tiles covered with an RCC cap. No SpaceX tile (either those on Starship now nor those seen previously) have had RCC caps. TUFROC was mentioned among a whole bunch of other TPS technologies as part of a Space Act Agreement, and for some bizarre reason it's been latched onto as some sort of perceived super-TPS for no apparent reason.
From the tile manufacture process description from the FDEP inspection document, SpaceX's tiles are almost identical to shuttle-era HRSI tiles, with the main compositional difference being a slightly different waterproofing agent, and the physical difference being the internal attachment frame.
Ed,
Can you give a bit more background on the FDEP doc? Maybe a link? I’m just so surprised because I feel like it’s the first I’m hearing of this. It feels like it really went semi-unnoticed here (at least in this thread?).
Hmm, site is acting up - does anyone perhaps have a copy? Or I’ll just try again later…
...I knew they were light, but I didn't think so much! It is very impressive.
A year ago discussions were guessing a density for the TPS system of about 13 kg/m^3, with a total system mass of 8,500 to 10,000 kg.
...
Not TUFROC.
TUFROC is HRSI tiles covered with an RCC cap.
...I knew they were light, but I didn't think so much! It is very impressive.
A year ago discussions were guessing a density for the TPS system of about 13 kg/m^3, with a total system mass of 8,500 to 10,000 kg.
...
Thanks. Now the numbers seem more reasonable....I knew they were light, but I didn't think so much! It is very impressive.
A year ago discussions were guessing a density for the TPS system of about 13 kg/m^3, with a total system mass of 8,500 to 10,000 kg.
...
- I think he was off by a decimal point. Tile insulation is similar to AETB. AETB has density in the 7-12 lb/ft^3 range (112-192 kg/m^3)
- This is just the insulation block. You then need to add the toughened outer thin shell and the mechanical attachment embedded inside the tile. These are small but significant mass additions.
John
...I knew they were light, but I didn't think so much! It is very impressive.
A year ago discussions were guessing a density for the TPS system of about 13 kg/m^3, with a total system mass of 8,500 to 10,000 kg.
...
- I think he was off by a decimal point. Tile insulation is similar to AETB. AETB has density in the 7-12 lb/ft^3 range (112-192 kg/m^3)
- This is just the insulation block. You then need to add the toughened outer thin shell and the mechanical attachment embedded inside the tile. These are small but significant mass additions.
John
...I knew they were light, but I didn't think so much! It is very impressive.
A year ago discussions were guessing a density for the TPS system of about 13 kg/m^3, with a total system mass of 8,500 to 10,000 kg.
...
- I think he was off by a decimal point. Tile insulation is similar to AETB. AETB has density in the 7-12 lb/ft^3 range (112-192 kg/m^3)
- This is just the insulation block. You then need to add the toughened outer thin shell and the mechanical attachment embedded inside the tile. These are small but significant mass additions.
John
Surface area of a cylinder: diameter * pi * height.
Surface area of Starship = 1/2 * 9m * 3.14 * 50 = ~700 m^2
depth of tile ~= 0.1m
Volume of tiles = 0.1 * 700 = 70m^3
70m^3 * 150 kg/m^3 ~= 10,000kg
How did others arrive at estimates of 10 tons of tiles?
Not TUFROC.
TUFROC is HRSI tiles covered with an RCC cap. No SpaceX tile (either those on Starship now nor those seen previously) have had RCC caps. TUFROC was mentioned among a whole bunch of other TPS technologies as part of a Space Act Agreement, and for some bizarre reason it's been latched onto as some sort of perceived super-TPS for no apparent reason.
From the tile manufacture process description from the FDEP inspection document, SpaceX's tiles are almost identical to shuttle-era HRSI tiles, with the main compositional difference being a slightly different waterproofing agent, and the physical difference being the internal attachment frame.
What happens if it rains on the Starship? Won't the white thermal insulator (under the tiles) be soaked in water, adding extra mass to the ship? When filled with cryogenic propellants, won't the soaked insulator expand and push the tiles out?
What happens if it rains on the Starship? Won't the white thermal insulator (under the tiles) be soaked in water, adding extra mass to the ship? When filled with cryogenic propellants, won't the soaked insulator expand and push the tiles out?
You're making the assumption that the under-layer is water absorbent. But, it's a good question, one of many that will need answers for before SS becomes operational. Right now I don't *think* they load propellants into F9 if it's raining, since that's a violation of their weather constraints.I agree. But even if they didn't load props when rainin they would need to wait after the thing dries. But this is all useless discussion since we know that the blancket is hydrophobic.
Have a good one,
Mike
You're making the assumption that the under-layer is water absorbent. But, it's a good question, one of many that will need answers for before SS becomes operational. Right now I don't *think* they load propellants into F9 if it's raining, since that's a violation of their weather constraints.I agree. But even if they didn't load props when rainin they would need to wait after the thing dries. But this is all useless discussion since we know that the blancket is hydrophobic.
Have a good one,
Mike
Just stop it, Spacex flies people to the ISS, lands boosters one after another and forgets that sometimes it rains...
falcon 9 booster doesn't even have a heat shield to begin withFalcon 9 has had multiple iteration of base heatshield (the 'dancefloor') from cork and SPAM coated aluminium to a titanium sandwich with water impingement cooling.
falcon 9 booster doesn't even have a heat shield to begin withFalcon 9 has had multiple iteration of base heatshield (the 'dancefloor') from cork and SPAM coated aluminium to a titanium sandwich with water impingement cooling.
falcon 9 booster doesn't even have a heat shield to begin withFalcon 9 has had multiple iteration of base heatshield (the 'dancefloor') from cork and SPAM coated aluminium to a titanium sandwich with water impingement cooling.
Yes you are right, it has heat protection, but not a remotely equivalent one, that was the point. Last iteration was mostly inconel protection, making it reusable. In any case, it relies almost completely on engines creating a plasma barrier, that is the real heat shield falcon 9 has. The inconel is there to resist 300ºC aprox. Protecting against 1500ºC for orbital reentry is orders of magnitude more complex though, and Inconel is useless for it. So to imply that current inconel heat protection is even remotely related to starship's tile technology, that it is remotely conceived for the same situation, and that current experience on inconel 300ºC reusable heat protection and ablative non-reusable heat protection from dragon automatically renders any concerns on shartship's new tile technology meaningless have no sense to me. It's a totally new situation.
previous post video shows upper part of sn20 heat shield tiles which were cracked been marked for replacement.Tiles move independently. The max elongation between pins is in the order of 1-2 tenths of a mm. Plus, the pins design aparently lets the tiles move. It doesnt seem ro be a problem.
Question to ask is ( if not already discussed) why did these tiles crack so badly?
I believe it was soon after the sn20 was lifted onto the bn4 booster and taken off that the cracking was marked and repaired. Why did all those tiles crack?
My theory is that as the sn20 was lifted by the straps at nosecone, the top portion of the craft underwent a certain amount of bending or distortion during the lift, this distortion was enough to crack many many tiles, they are probably quite easily cracked I suspect.
The lower half of the ship was unaffected and not enough distortion of the stainless shell to effect the bottom half tiles.
But this leads me to wonder at lift off, the vibrational forces will be huge, I suspect the tiles will be cracking and falling off all over the place!! during liftoff phase. There would need to be significant testing of how the tiles mounted as they are will respond to liftoff. I would think that the spaces inbetween the tiles need to be filled with a heat resistant flexible silicone or similar which reduce damage to tiles during liftoff. Even static test fires will give an indication how well the tiles will hold up.
If simply lifting the sn20 very slowly and calmly breaks so many tiles, vibration at takeoff will be many times worse outcome.
previous post video shows upper part of sn20 heat shield tiles which were cracked been marked for replacement.
Question to ask is ( if not already discussed) why did these tiles crack so badly?
I believe it was soon after the sn20 was lifted onto the bn4 booster and taken off that the cracking was marked and repaired. Why did all those tiles crack?
My theory is that as the sn20 was lifted by the straps at nosecone, the top portion of the craft underwent a certain amount of bending or distortion during the lift, this distortion was enough to crack many many tiles, they are probably quite easily cracked I suspect.
The lower half of the ship was unaffected and not enough distortion of the stainless shell to effect the bottom half tiles.
But this leads me to wonder at lift off, the vibrational forces will be huge, I suspect the tiles will be cracking and falling off all over the place!! during liftoff phase. There would need to be significant testing of how the tiles mounted as they are will respond to liftoff. I would think that the spaces inbetween the tiles need to be filled with a heat resistant flexible silicone or similar which reduce damage to tiles during liftoff. Even static test fires will give an indication how well the tiles will hold up.
If simply lifting the sn20 very slowly and calmly breaks so many tiles, vibration at takeoff will be many times worse outcome.
previous post video shows upper part of sn20 heat shield tiles which were cracked been marked for replacement.
Question to ask is ( if not already discussed) why did these tiles crack so badly?
I believe it was soon after the sn20 was lifted onto the bn4 booster and taken off that the cracking was marked and repaired. Why did all those tiles crack?
My theory is that as the sn20 was lifted by the straps at nosecone, the top portion of the craft underwent a certain amount of bending or distortion during the lift, this distortion was enough to crack many many tiles, they are probably quite easily cracked I suspect.
The lower half of the ship was unaffected and not enough distortion of the stainless shell to effect the bottom half tiles.
But this leads me to wonder at lift off, the vibrational forces will be huge, I suspect the tiles will be cracking and falling off all over the place!! during liftoff phase. There would need to be significant testing of how the tiles mounted as they are will respond to liftoff. I would think that the spaces inbetween the tiles need to be filled with a heat resistant flexible silicone or similar which reduce damage to tiles during liftoff. Even static test fires will give an indication how well the tiles will hold up.
If simply lifting the sn20 very slowly and calmly breaks so many tiles, vibration at takeoff will be many times worse outcome.
The reasons are haste and shortage of the tiles. The worst affected areas were tiled last and it looks the tiles were damaged during installation.
previous post video shows upper part of sn20 heat shield tiles which were cracked been marked for replacement.
Question to ask is ( if not already discussed) why did these tiles crack so badly?
I believe it was soon after the sn20 was lifted onto the bn4 booster and taken off that the cracking was marked and repaired. Why did all those tiles crack?
My theory is that as the sn20 was lifted by the straps at nosecone, the top portion of the craft underwent a certain amount of bending or distortion during the lift, this distortion was enough to crack many many tiles, they are probably quite easily cracked I suspect.
The lower half of the ship was unaffected and not enough distortion of the stainless shell to effect the bottom half tiles.
But this leads me to wonder at lift off, the vibrational forces will be huge, I suspect the tiles will be cracking and falling off all over the place!! during liftoff phase. There would need to be significant testing of how the tiles mounted as they are will respond to liftoff. I would think that the spaces inbetween the tiles need to be filled with a heat resistant flexible silicone or similar which reduce damage to tiles during liftoff. Even static test fires will give an indication how well the tiles will hold up.
If simply lifting the sn20 very slowly and calmly breaks so many tiles, vibration at takeoff will be many times worse outcome.
The reasons are haste and shortage of the tiles. The worst affected areas were tiled last and it looks the tiles were damaged during installation.
Also this has been tested many times. They have been putting tiles on SS's for a while now in many different places.
Since this is the nose cone, where hex tiles don't exactly line up line they do on a cylinder, my guess is that they have tolerance issues on the nose cone with the tile sizes, pin placement, and movement of the underlying surface all contributing.
Hammering in tiles that wouldn't quite fit probably damaged them. As would lifting causing movement of the underlying surface.
Fix: make some slightly smaller tiles or shape custom ones for the locations that normal tiles won't fit.
You're making the assumption that the under-layer is water absorbent. But, it's a good question, one of many that will need answers for before SS becomes operational. Right now I don't *think* they load propellants into F9 if it's raining, since that's a violation of their weather constraints.I agree. But even if they didn't load props when rainin they would need to wait after the thing dries. But this is all useless discussion since we know that the blancket is hydrophobic.
Have a good one,
Mike
The blanket being waterproof has been confirmed? Usually waterproof insulation blankets have lower temperature rating than normal ones.
But even if the blanket is waterproofed in any form, water can still accumulate between tiles, between the blanket and the steel, find its way into the glue, etc. Even a small amount of water in the correct spot can exert enough force to easily flex a blanket and move tiles in top if it becomes ice when fuelling the ship.
I would say that for testing if it rains they will wait a few days to be sure any pockets of water are gone. When starship becomes commercial I will not find it strange if they keep them under a roof. Freezing water in cracks will never stop being a risk.
A white-pigmented silicon elastomer coating is used to waterproof the felt and provide required thermal and optical properties.
He's using a big soft mushy fist mallet that distributes stress. Stress would collect where the tile touches the pins, and this would be limited by the compressibility of the bayonet. Any force beyond that needed to compress the bayonet (plus a smidge of sliding friction) is too much. It's literally a matter of 'feel'.
The vitrified coating should help distribute impact stress and it will have a limit but higher than the fluffy white. Rock hammers not recommended.
You're making the assumption that the under-layer is water absorbent. But, it's a good question, one of many that will need answers for before SS becomes operational. Right now I don't *think* they load propellants into F9 if it's raining, since that's a violation of their weather constraints.I agree. But even if they didn't load props when rainin they would need to wait after the thing dries. But this is all useless discussion since we know that the blancket is hydrophobic.
Have a good one,
Mike
The blanket being waterproof has been confirmed? Usually waterproof insulation blankets have lower temperature rating than normal ones.
But even if the blanket is waterproofed in any form, water can still accumulate between tiles, between the blanket and the steel, find its way into the glue, etc. Even a small amount of water in the correct spot can exert enough force to easily flex a blanket and move tiles in top if it becomes ice when fuelling the ship.
I would say that for testing if it rains they will wait a few days to be sure any pockets of water are gone. When starship becomes commercial I will not find it strange if they keep them under a roof. Freezing water in cracks will never stop being a risk.
The info we got from Jean Wright on the NSF livestream was that the white blanket was SIP, made of Nomex felt. If that's true, this might be the same thing that Shuttle had.
And this is what NASA says about its waterproofing of FRSI blankets (FELT REUSABLE SURFACE INSULATION) that used the same Nomex material:QuoteA white-pigmented silicon elastomer coating is used to waterproof the felt and provide required thermal and optical properties.
I haven't seen this info anywhere, so I apologize if it has been posted, but has anyone taken the time to see just how many unique tiles are currently being used? That'd be a daunting task but I'm curious as to what the minimum amount of unique tiles are needed for SN20 and then tracking it over time.Somewhere here there is a very good high res photo that shows dozens of tile types around the nose and flaperon. Some of the tiles were written on and if I could find that photo and another of the lower flap area it might be possible to come up with a rough estimate. My google foo is not good enough and there's just too many threads with too much content...
You're making the assumption that the under-layer is water absorbent. But, it's a good question, one of many that will need answers for before SS becomes operational. Right now I don't *think* they load propellants into F9 if it's raining, since that's a violation of their weather constraints.I agree. But even if they didn't load props when rainin they would need to wait after the thing dries. But this is all useless discussion since we know that the blancket is hydrophobic.
Have a good one,
Mike
The blanket being waterproof has been confirmed? Usually waterproof insulation blankets have lower temperature rating than normal ones.
But even if the blanket is waterproofed in any form, water can still accumulate between tiles, between the blanket and the steel, find its way into the glue, etc. Even a small amount of water in the correct spot can exert enough force to easily flex a blanket and move tiles in top if it becomes ice when fuelling the ship.
I would say that for testing if it rains they will wait a few days to be sure any pockets of water are gone. When starship becomes commercial I will not find it strange if they keep them under a roof. Freezing water in cracks will never stop being a risk.
The info we got from Jean Wright on the NSF livestream was that the white blanket was SIP, made of Nomex felt. If that's true, this might be the same thing that Shuttle had.
And this is what NASA says about its waterproofing of FRSI blankets (FELT REUSABLE SURFACE INSULATION) that used the same Nomex material:QuoteA white-pigmented silicon elastomer coating is used to waterproof the felt and provide required thermal and optical properties.
I don't think Star Ship is using FRSI Blankets. The white underlayment we see on Star Ship appears to be a looser batting material. Could be NOMEX or Silica based fiber.
John
You're making the assumption that the under-layer is water absorbent. But, it's a good question, one of many that will need answers for before SS becomes operational. Right now I don't *think* they load propellants into F9 if it's raining, since that's a violation of their weather constraints.I agree. But even if they didn't load props when rainin they would need to wait after the thing dries. But this is all useless discussion since we know that the blancket is hydrophobic.
Have a good one,
Mike
The blanket being waterproof has been confirmed? Usually waterproof insulation blankets have lower temperature rating than normal ones.
But even if the blanket is waterproofed in any form, water can still accumulate between tiles, between the blanket and the steel, find its way into the glue, etc. Even a small amount of water in the correct spot can exert enough force to easily flex a blanket and move tiles in top if it becomes ice when fuelling the ship.
I would say that for testing if it rains they will wait a few days to be sure any pockets of water are gone. When starship becomes commercial I will not find it strange if they keep them under a roof. Freezing water in cracks will never stop being a risk.
The info we got from Jean Wright on the NSF livestream was that the white blanket was SIP, made of Nomex felt. If that's true, this might be the same thing that Shuttle had.
And this is what NASA says about its waterproofing of FRSI blankets (FELT REUSABLE SURFACE INSULATION) that used the same Nomex material:QuoteA white-pigmented silicon elastomer coating is used to waterproof the felt and provide required thermal and optical properties.
Nomex: About 200degC (much above 250degC it just burns)
Stainless Steel: about 600 degC (can go almost double this but loses strength).
Nomex: About 200degC (much above 250degC it just burns)
Stainless Steel: about 600 degC (can go almost double this but loses strength).
Do you have a source for that statement? AFAIK Aramide fibers have temperature ranges up to ~370 degrees C without degradation, beyond that you get a carbonization layer but no active burning.
Nomex: About 200degC (much above 250degC it just burns)
Stainless Steel: about 600 degC (can go almost double this but loses strength).
Do you have a source for that statement? AFAIK Aramide fibers have temperature ranges up to ~370 degrees C without degradation, beyond that you get a carbonization layer but no active burning.
The graph looks like it‘s either for very long exposure (months/years) in an oxidising environment, or it‘s a degree Celsius/Fahrenheit mixup, both would somehow fit.Nomex: About 200degC (much above 250degC it just burns)
Stainless Steel: about 600 degC (can go almost double this but loses strength).
Do you have a source for that statement? AFAIK Aramide fibers have temperature ranges up to ~370 degrees C without degradation, beyond that you get a carbonization layer but no active burning.
I'll note 370degC is still about half of what Stainless steel can handle. So my point still stands.
That being said, here's my source:
https://www.dupont.com/content/dam/dupont/amer/us/en/personal-protection/public/documents/en/Nomex(R)%20Fiber%20Technical%20Guide.pdf
See figure 2.5. I note a contradiction between the text of that figure and the graph of that figure.
It makes sense to put Nomex over Aluminum, but not over stainless steel.
Somewhere here there is a very good high res photo that shows dozens of tile types around the nose and flaperon. Some of the tiles were written on and if I could find that photo and another of the lower flap area it might be possible to come up with a rough estimate. My google foo is not good enough and there's just too many threads with too much content...
They use Nomex in race car suits and firefighter suits for a reason....Racecar drivers may like to go fast, but they do not re-enter at hypervelocity (I suspect some would have been willing to give MOOSE a try, though).
My guess is ceramic/glass felt would have lower vibration tolerance and add inhalation exposure risk for workers, metallic fleece would have higher heat conductivity, thus possible ice-buildup problems on the pad.
Nomex: About 200degC (much above 250degC it just burns)
Stainless Steel: about 600 degC (can go almost double this but loses strength).
Do you have a source for that statement? AFAIK Aramide fibers have temperature ranges up to ~370 degrees C without degradation, beyond that you get a carbonization layer but no active burning.
I'll note 370degC is still about half of what Stainless steel can handle. So my point still stands.
That being said, here's my source:
https://www.dupont.com/content/dam/dupont/amer/us/en/personal-protection/public/documents/en/Nomex(R)%20Fiber%20Technical%20Guide.pdf
See figure 2.5. I note a contradiction between the text of that figure and the graph of that figure.
It makes sense to put Nomex over Aluminum, but not over stainless steel.
I think I must be reading some of this data wrong. The figure also contradicts the text directly above it. What am I missing?
Or just go straight to solving this problem next time and not waste any time on temporary solutions? This is the first orbital prototype, it doesn't matter really, maybe it won't even fly.
I thought we learned from Shuttle days that smoothness is important to prevent shock waves. Remember the gap filler drama? Is SpaceX about to prove us all wrong, again?
Edit: photo credit: bocachicagal
I thought we learned from Shuttle days that smoothness is important to prevent shock waves. Remember the gap filler drama? Is SpaceX about to prove us all wrong, again?
Edit: photo credit: bocachicagal
Gap fillers were critical for Shuttle because the underlying structure was aluminium. The only reason shuttle Atlantis existed beyond STS-27 is because the one tile that sheared off completely happened to be sitting on top of a solid steel equipment mounting plate.
Guess what's sitting underneath Starship's tiles? It ain't easy melty stuff like aluminium for a reason.
Yep, it is the forward -Y (starboard) fin tip fairing, this post (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2270083#msg2270083) shows the same delivery for S20 and this one (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2271518#msg2271518) shows the installation of the +Y one for S20.Aerocovers are for the booster which has no heat shield tiles. Probably just easier to make this way.
These ones are for a Starship though. Note the rounded part which covers the top of the flap hinge.
So they did update the design from smooth to angular. Must help with tiles, I'd think...
I wonder how much of the problem is down to minor irregularities in the underlying steel and pins? Minor warping and buckling due to welding might cause all manner of misalignments. But that should improve as they refine the process of manufacture especially when they use the new gores to make the nosecone. If they can get ship 20 down in one piece (and that's a big if), these improvements would just add to the safety margin. We shall see.
Cross-post, of relevance to the perennial "# of unique tiles" discussion:Yep, it is the forward -Y (starboard) fin tip fairing, this post (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2270083#msg2270083) shows the same delivery for S20 and this one (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2271518#msg2271518) shows the installation of the +Y one for S20.Aerocovers are for the booster which has no heat shield tiles. Probably just easier to make this way.
These ones are for a Starship though. Note the rounded part which covers the top of the flap hinge.
So they did update the design from smooth to angular. Must help with tiles, I'd think...
I wonder how much of the problem is down to minor irregularities in the underlying steel and pins? Minor warping and buckling due to welding might cause all manner of misalignments. But that should improve as they refine the process of manufacture especially when they use the new gores to make the nosecone. If they can get ship 20 down in one piece (and that's a big if), these improvements would just add to the safety margin. We shall see.But we see irregular heights (tile-skin separations), which suggests that either (1) the pins have irregular lengths or (2) the pin lengths don’t determine the heights. Option (2) makes little sense -- what else would determine the heights? But option (1) makes no sense at all. ???
Nothing that a really large orbital sander won't cure...;-)I bet even a suborbital sander would work!
But we see irregular heights (tile-skin separations), which suggests that either (1) the pins have irregular lengths or (2) the pin lengths don’t determine the heights. Option (2) makes little sense -- what else would determine the heights? But option (1) makes no sense at all. ???I'd guess it's basically (2), in that there is variation in how far into each tile the pin "grabs" the tile, and that it is not limited by a hard-stopped socket on the tile side. For example, it could be a slot with some head space above the pin so the vertical position is not locked to just one point. The installer pushes the tile onto the pins. At some point they start engaging with slots in the tiles, maybe like a zip tie that goes one way but not the other without damage. Some tiles go down a bit further on the pins than others, so the tile surfaces don't match. Maybe some tile edges hit each other at points that don't fit as well so some tile cannot be pushed down as far as others.
The tiles on the tip are glued on and don't use the attachment pins that are used elsewhere.But we see irregular heights (tile-skin separations), which suggests that either (1) the pins have irregular lengths or (2) the pin lengths don’t determine the heights. Option (2) makes little sense -- what else would determine the heights? But option (1) makes no sense at all. ???I'd guess it's basically (2), in that there is variation in how far into each tile the pin "grabs" the tile, and that it is not limited by a hard-stopped socket on the tile side. For example, it could be a slot with some head space above the pin so the vertical position is not locked to just one point. The installer pushes the tile onto the pins. At some point they start engaging with slots in the tiles, maybe like a zip tie that goes one way but not the other without damage. Some tiles go down a bit further on the pins than others, so the tile surfaces don't match. Maybe some tile edges hit each other at points that don't fit as well so some tile cannot be pushed down as far as others.
The tiles on the tip are glued on and don't use the attachment pins that are used elsewhere.But we see irregular heights (tile-skin separations), which suggests that either (1) the pins have irregular lengths or (2) the pin lengths don’t determine the heights. Option (2) makes little sense -- what else would determine the heights? But option (1) makes no sense at all. ???I'd guess it's basically (2), in that there is variation in how far into each tile the pin "grabs" the tile, and that it is not limited by a hard-stopped socket on the tile side. For example, it could be a slot with some head space above the pin so the vertical position is not locked to just one point. The installer pushes the tile onto the pins. At some point they start engaging with slots in the tiles, maybe like a zip tie that goes one way but not the other without damage. Some tiles go down a bit further on the pins than others, so the tile surfaces don't match. Maybe some tile edges hit each other at points that don't fit as well so some tile cannot be pushed down as far as others.
The tiles on the tip are glued on and don't use the attachment pins that are used elsewhere.But we see irregular heights (tile-skin separations), which suggests that either (1) the pins have irregular lengths or (2) the pin lengths don’t determine the heights. Option (2) makes little sense -- what else would determine the heights? But option (1) makes no sense at all. ???I'd guess it's basically (2), in that there is variation in how far into each tile the pin "grabs" the tile, and that it is not limited by a hard-stopped socket on the tile side. For example, it could be a slot with some head space above the pin so the vertical position is not locked to just one point. The installer pushes the tile onto the pins. At some point they start engaging with slots in the tiles, maybe like a zip tie that goes one way but not the other without damage. Some tiles go down a bit further on the pins than others, so the tile surfaces don't match. Maybe some tile edges hit each other at points that don't fit as well so some tile cannot be pushed down as far as others.
Good point, RoboGoofers! That process may be a bit uneven now too if it is manual and they don't have jigs and such to help make it consistent.
That makes sense, but what bugs me is: Why?But we see irregular heights (tile-skin separations), which suggests that either (1) the pins have irregular lengths or (2) the pin lengths don’t determine the heights. Option (2) makes little sense -- what else would determine the heights? But option (1) makes no sense at all. ???I'd guess it's basically (2), in that there is variation in how far into each tile the pin "grabs" the tile, and that it is not limited by a hard-stopped socket on the tile side.[...]
I'm looking close at that pin pic and realized everything above is BS. All of a sudden I don't know how those pins work.Yeah. If the Y-bracket-thing had Y-oriented slots (which it seems that it should, if the thing works as a kinematic constraint system), then pins we see would be wide in the wrong (radial) direction to engage with the walls of the slots.
AFAIK we don't have good dimensions on the pins, the "Y" plate or the slots in it. Look at the first two rows or the second and third. The way the Y orients the round thingie I was calling a barb, will not engage the walls of the slot.
The structure below the round thingie looks to be wider than the slot. I think. If so, it would act as a stop. But not a latch. So what's this sucker doing?
I'm looking close at that pin pic and realized everything above is BS. All of a sudden I don't know how those pins work.
AFAIK we don't have good dimensions on the pins, the "Y" plate or the slots in it. Look at the first two rows or the second and third. The way the Y orients the round thingie I was calling a barb, will not engage the walls of the slot.
The structure below the round thingie looks to be wider than the slot. I think. If so, it would act as a stop. But not a latch. So what's this sucker doing?
....
It’s a good rule of thumb to assume that SpaceX designs are good, and that anything that seems wrong is actually very clever. In this case, the huge number of crooked, protruding, and broken tiles suggests a real design problem. /sacrilege
If blanket installation is a problem because of bunching, uneveness, etc.
How about a robot controlled cotton candy machine to form the blankets right on the skin directly. Fiberglass is made this way. Hot molten glass sprayed out and solidifies.
https://en.wikipedia.org/wiki/Glass_fiber#Staple_fiber_process
You might be on to something with a latch mechanism on the tile end. Maybe. Here's Mary's pick cropped down to one pin with a little image voodoo.I'm looking close at that pin pic and realized everything above is BS. All of a sudden I don't know how those pins work.
AFAIK we don't have good dimensions on the pins, the "Y" plate or the slots in it. Look at the first two rows or the second and third. The way the Y orients the round thingie I was calling a barb, will not engage the walls of the slot.
The structure below the round thingie looks to be wider than the slot. I think. If so, it would act as a stop. But not a latch. So what's this sucker doing?
The head of the pin is a ring/hole itself, so there can be a hidden latching mechanism behind/inside the slot, securing that ring in place.
Also the pins seems like cut and bended from a single sheet. Forming a ring perpendicular to the existing ones would be difficult with that technique.
Yes, a major design flaw at this point would be really surprising, but I’m already surprised by the flaws in the product, and it’s hard not to blame the design. Surprise is already baked into the cake. I’m betting that we’ll see another iteration of the fasteners.....
It’s a good rule of thumb to assume that SpaceX designs are good, and that anything that seems wrong is actually very clever. In this case, the huge number of crooked, protruding, and broken tiles suggests a real design problem. /sacrilege
This is their Nth iteration of the pin system: we seen 3 different types tested simultaneously, smaller ones, single pin designs, and also different solutions at the y-socket side. What we see now is most likely a downselected/improved method based on all those. A major design flaw at this point would be really suprising.
[...]
Or they will stop using the current attachment points on the nose and/ or strengthen the nose structure to avoid material deformation during lift.The steel can’t deform enough to cause this kind of problem.
How is it that after all this time we still don't have a GOOD picture of these clips?Do we have a good picture of the Y channel, or whatever it is?
I decided to try to model one up and in the process realized my Sketchup skills are really rusty but here is how I think the clip looks. To me it looks like the loop part is something special, maybe not exactly like my model but in some pictures it does look like the loop is in fact two overlapping loop parts that slide across each other. This design makes sense because it is a simple few steps to punch and press/bend into shape.
However after I put it all together and was going to post I realized that the pin is oriented to the Y chanel part in the tile rotated 90 degrees to what I have here (D'oh)! So now I am confused again.
How is it that after all this time we still don't have a GOOD picture of these clips?Do we have a good picture of the Y channel, or whatever it is?
I decided to try to model one up and in the process realized my Sketchup skills are really rusty but here is how I think the clip looks. To me it looks like the loop part is something special, maybe not exactly like my model but in some pictures it does look like the loop is in fact two overlapping loop parts that slide across each other. This design makes sense because it is a simple few steps to punch and press/bend into shape.
However after I put it all together and was going to post I realized that the pin is oriented to the Y chanel part in the tile rotated 90 degrees to what I have here (D'oh)! So now I am confused again.
Yeah, considering the distances involved I am impressed by what we actually get!Yes, sort of: [Attach images so they don't beak all the posts ;)]How is it that after all this time we still don't have a GOOD picture of these clips?Do we have a good picture of the Y channel, or whatever it is?
I decided to try to model one up and in the process realized my Sketchup skills are really rusty but here is how I think the clip looks. To me it looks like the loop part is something special, maybe not exactly like my model but in some pictures it does look like the loop is in fact two overlapping loop parts that slide across each other. This design makes sense because it is a simple few steps to punch and press/bend into shape.
However after I put it all together and was going to post I realized that the pin is oriented to the Y chanel part in the tile rotated 90 degrees to what I have here (D'oh)! So now I am confused again.
I’d like to see the side that faces the clip. Seeing the top side with material broken away only gives hints about the mechanical interface underneath.How is it that after all this time we still don't have a GOOD picture of these clips?Do we have a good picture of the Y channel, or whatever it is?
I decided to try to model one up and in the process realized my Sketchup skills are really rusty but here is how I think the clip looks. To me it looks like the loop part is something special, maybe not exactly like my model but in some pictures it does look like the loop is in fact two overlapping loop parts that slide across each other. This design makes sense because it is a simple few steps to punch and press/bend into shape.
However after I put it all together and was going to post I realized that the pin is oriented to the Y chanel part in the tile rotated 90 degrees to what I have here (D'oh)! So now I am confused again.
Yes, sort of:
It has to be kinematic, because of CTE mismatch.I'm looking close at that pin pic and realized everything above is BS. All of a sudden I don't know how those pins work.Yeah. If the Y-bracket-thing had Y-oriented slots (which it seems that it should, if the thing works as a kinematic constraint system), then pins we see would be wide in the wrong (radial) direction to engage with the walls of the slots.
AFAIK we don't have good dimensions on the pins, the "Y" plate or the slots in it. Look at the first two rows or the second and third. The way the Y orients the round thingie I was calling a barb, will not engage the walls of the slot.
The structure below the round thingie looks to be wider than the slot. I think. If so, it would act as a stop. But not a latch. So what's this sucker doing?
Also, not stopped and latched.
It’s a good rule of thumb to assume that SpaceX designs are good, and that anything that seems wrong is actually very clever. In this case, the huge number of crooked, protruding, and broken tiles suggests a real design problem. /sacrilege
How is it that after all this time we still don't have a GOOD picture of these clips?Ahhhha, you see ze problem! Join the confusion. We probably haven't seen a really good pin pic because they are small and being backed by stainless, have a confusing welter of light and shadow. Throw in the welding scar and it only gets worse.
I decided to try to model one up and in the process realized my Sketchup skills are really rusty but here is how I think the clip looks. To me it looks like the loop part is something special, maybe not exactly like my model but in some pictures it does look like the loop is in fact two overlapping loop parts that slide across each other. This design makes sense because it is a simple few steps to punch and press/bend into shape.
However after I put it all together and was going to post I realized that the pin is oriented to the Y chanel part in the tile rotated 90 degrees to what I have here (D'oh)! So now I am confused again.
So based on the latest images (thanks guys) no magic on the socket side. The elongated hole in the brackets simply long as the tile head circle diameter (slightly below). And the studs firmly latch in as decribed above. And thus not provide/enable the suspected kinematic coupling.Where are you seeing the arms not joined?
But the Y brackets seems shorter than the half tile axis and the 3 of them seems also independent (not joined), so the kinematic coupling may provided by the metal brackets sliding inside the tile (or not exists at all).
.....
Where are you seeing the arms not joined?
pic posted on previous page showing two broken tiles, not sure if anyone noticed on left side of that pic is nice pic of the clips, you can make out how that version works, very simple clip....pic attached, about as simple as you could possibly make it.I was seeing that too. The leaf spring bears on the top of the leg you mark as 'free', at least on this version.
Thanks for digging out those pics. I was picturing a slot running down each arm, not a hole. Did an early version have a slot? With a hole, the barb orientation makes perfect sense......
Where are you seeing the arms not joined?
I remember some pics of broken tiles, where the remaining arms were rotated. But i cannot find a decisive one. Maybe I am wrong.
On the first, the arms are clearly rotating, but that is an older/now outdated attachment version.
On the second, the arms are in place, but there is a white gap below the uppermost one.
The third is SN17 at the scrapyard, there are many misaligned lines, but can be anything due to low resolution.
All three is from the forum. 1, 2 from BocaChicaGal, the third is Nomadd.
Edit: maybe the SN17 pic give us a hint. Some of the arms are simply missing, while the rest of the tile are in place. That suggest that the arms are independent.
The collar looks like a feature meant to ensure tiles are at a uniform height. I wonder if some of the "older" pins on starship are pre-collar, which would explain some of the unevenness.Pre-collar like the image linked in this post, presumably:
pic posted on previous page showing two broken tiles, not sure if anyone noticed on left side of that pic is nice pic of the clips, you can make out how that version works, very simple clip....pic attached, about as simple as you could possibly make it.Those look like a surprisingly bad idea, and I guess they were.
The collar looks like a feature meant to ensure tiles are at a uniform height. I wonder if some of the "older" pins on starship are pre-collar, which would explain some of the unevenness.
The collar looks like a feature meant to ensure tiles are at a uniform height. I wonder if some of the "older" pins on starship are pre-collar, which would explain some of the unevenness.
There are already a sholuder not far below that collar, acting presumably as a stopper. The colar would be a redundant piece in that function. Seems illogical, why not raise shoulder height, if necessary?
Instead I have two, completely speculative idea.
The collar may act as a release on push mechanism, holding the clip tight for easier tile installation, released by the slot pushing it down. That would enable the springs to push the pin wider, to latch more firmly. Less likely as the collar seems unremovable.
Another function may be to hold the clip tight/straight, to prevent outward deformation. That is a possible failure mode in the prev version. If too much force applied during install, clip legs may bend out (O shape), as they only connected at the top and bottom holding in that direction (springs prevent only invard bending). The collar can be a third, cross bar/reinforcement, against that.
Edit: clarification.
Ps. O style bending can be an explanation for unevennes. If pin legs bend out, that would reduce the pin height. And that is also an installation process related issue.
The collar looks like a feature meant to ensure tiles are at a uniform height. I wonder if some of the "older" pins on starship are pre-collar, which would explain some of the unevenness.
There are already a sholuder not far below that collar, acting presumably as a stopper. The colar would be a redundant piece in that function. Seems illogical, why not raise shoulder height, if necessary?
Instead I have two, completely speculative idea.
The collar may act as a release on push mechanism, holding the clip tight for easier tile installation, released by the slot pushing it down. That would enable the springs to push the pin wider, to latch more firmly. Less likely as the collar seems unremovable.
Another function may be to hold the clip tight/straight, to prevent outward deformation. That is a possible failure mode in the prev version. If too much force applied during install, clip legs may bend out (O shape), as they only connected at the top and bottom holding in that direction (springs prevent only invard bending). The collar can be a third, cross bar/reinforcement, against that.
Edit: clarification.
Ps. O style bending can be an explanation for unevennes. If pin legs bend out, that would reduce the pin height. And that is also an installation process related issue.
I don't think they want the tiles to release, ever. They are not serviceable, and a release mechanism is just a potential mode they don't want happening in flight.
....
Instead I have two, completely speculative idea.
The collar may act as a release on push mechanism, holding the clip tight for easier tile installation, released by the slot pushing it down. That would enable the springs to push the pin wider, to latch more firmly. Less likely as the collar seems unremovable.
....
I don't think they want the tiles to release, ever. They are not serviceable, and a release mechanism is just a potential mode they don't want happening in flight.
Interesting spot. Just happened that one of the tiles got stuck upside down.I see radial slots here. Maybe not as long as folks were expecting -- but what's the expected magnitude of thermal expansion, anyway? A couple of centimeters should do it.
No radial slots therefore no kinematic coupling therefore radial stresses.
Radial metal Y-arms can take radial loads therefore radial stresses need not be applied to fragile glass.
Seems pretty good, actually.
I see radial slots here. Maybe not as long as folks were expecting -- but what's the expected magnitude of thermal expansion, anyway? A couple of centimeters should do it.
Interesting spot. Just happened that one of the tiles got stuck upside down.Looking at the deep hollows across the back surface of that tile, ISTM that much of the insulating capacity has been shifted from the tiles to the blanket. A further evolution in this direction would make the tiles essentially caps that hold the blanket in place and protect it from air flow. In this scenario, tile materials could be optimized for strength and toughness with little concern for thermal conductance. They would likely be thinner and denser -- and what we see may be already, relative to earlier versions.
Interesting spot. Just happened that one of the tiles got stuck upside down.Looking at the deep hollows across the back surface of that tile, ISTM that much of the insulating capacity has been shifted from the tiles to the blanket. A further evolution in this direction would make the tiles essentially caps that hold the blanket in place and protect it from air flow. In this scenario, tile materials could be optimized for strength and toughness with little concern for thermal conductance. They would likely be thinner and denser -- and what we see may be already, relative to earlier versions.
There may be other ways to hold the blanket in place, but there’s a need for a surface that supports aerodynamic forces at high temperatures with joints to accommodate thermal expansion. Ceramic tiles do this, and can provide black, high-emissivity surfaces too. Metal might work, but metal-surfaced TPS options have been been considered and rejected by multiple development teams addressing the same problem. What are the other options, and how are they simpler?That sounds totally wrong to me. If it was just about holding the blanket in place, then that could be done in a much easier way than with tiles. My guess is that the tiles deal with 95+ percent of the heat load.Interesting spot. Just happened that one of the tiles got stuck upside down.Looking at the deep hollows across the back surface of that tile, ISTM that much of the insulating capacity has been shifted from the tiles to the blanket. A further evolution in this direction would make the tiles essentially caps that hold the blanket in place and protect it from air flow. In this scenario, tile materials could be optimized for strength and toughness with little concern for thermal conductance. They would likely be thinner and denser -- and what we see may be already, relative to earlier versions.
Remember that hollow space in a vacuum is a great insulator (think your own double-glazing windows). Combined with the tile in front that hollow would mean that not much heat reaches the blanket.There’s a reason why insulating structures (TPS tiles, house walls) so often fill spaces with fine fibers, not large voids, presumably to suppress convection and impede radiative transfer (keep in mind that hollow spaces fill with gas during entry). Double-glazed windows don’t contain fiber insulation because they must be transparent.
A major function of the tile surface is to be extremely hot and radiate energy away. The insulation plays the part of preventing heat transfer inward to the steel, allowing most energy to go to radiation.
In fact, if you want to keep something thermally insulated in a cryogenic vacuum environment, the strategy is to have a reduced surface of contact with the cryo surfaces with a very low conductivity material.
Those pins are really bugging me. The way the spring thingies work, they load into the base. That makes no sense if the purpose is to keep an expansion tension at the top - unless only one leg is welded. Looking at the pick it looks like at least some of the welding marks do bias to one side.
The blanket is definitely not the main insulator, it's only intended to insulate between the tile backside temperature and the tank wall, and provide some mechanical 'springiness' to back the tiles rather than placing them directly on metal. Unsintered silica fibre is not as insulating as kiln-fired sintered tile, lacks a lightweight waterproofing method, lacks a tightly bonded radiative cap, and is completely mechanically unsuitable to act as the main flow-contacting TPS surface. [...]What counts as the “main insulator” is unclear. The outer surface must deal with the highest temperatures and actual flow contact (which requires a hard surface), but most of the thermal resistance could be in the blanket. I’d call thermal resistance (reducing W/m2K) to be the main insulating function. The tiles being hotter is beside the point -- tile backside temperatures could be quite high and most of the ΔT could be in the somewhat cooler blanket. I don’t think we know.
The blanket is definitely not the main insulator, it's only intended to insulate between the tile backside temperature and the tank wall, and provide some mechanical 'springiness' to back the tiles rather than placing them directly on metal. Unsintered silica fibre is not as insulating as kiln-fired sintered tile, lacks a lightweight waterproofing method, lacks a tightly bonded radiative cap, and is completely mechanically unsuitable to act as the main flow-contacting TPS surface. [...]What counts as the “main insulator” is unclear. The outer surface must deal with the highest temperatures and actual flow contact (which requires a hard surface), but most of the thermal resistance could be in the blanket. I’d call thermal resistance (reducing W/m2K) to be the main insulating function. The tiles being hotter is beside the point -- tile backside temperatures could be quite high and most of the ΔT could be in the somewhat cooler blanket. I don’t think we know.
All else being equal, unsintered fibre should be more insulating. Sintering increases strength and rigidity but also creates paths for thermal conduction. In addition, the mechanical function of sintered tiles calls for substantial density, where blankets can be basically fluff.
What about the heat tolerance of the clips themselves? They stick up beyond the blanket. Is there any high temperature metal that can be welded to stainless steel? What happens if they're heated to the annealing point? They might have to stay as cool as the body of the vehicle.
The blanket is definitely not the main insulator, it's only intended to insulate between the tile backside temperature and the tank wall, and provide some mechanical 'springiness' to back the tiles rather than placing them directly on metal. Unsintered silica fibre is not as insulating as kiln-fired sintered tile, lacks a lightweight waterproofing method, lacks a tightly bonded radiative cap, and is completely mechanically unsuitable to act as the main flow-contacting TPS surface. [...]What counts as the “main insulator” is unclear. The outer surface must deal with the highest temperatures and actual flow contact (which requires a hard surface), but most of the thermal resistance could be in the blanket. I’d call thermal resistance (reducing W/m2K) to be the main insulating function. The tiles being hotter is beside the point -- tile backside temperatures could be quite high and most of the ΔT could be in the somewhat cooler blanket. I don’t think we know.
All else being equal, unsintered fibre should be more insulating. Sintering increases strength and rigidity but also creates paths for thermal conduction. In addition, the mechanical function of sintered tiles calls for substantial density, where blankets can be basically fluff.
An interesting item that traverses layers are the clips that are welded to the tanks. They can heat up to 1300degC (close to melting temperature), but if they are stainless they don't conduct heat well enough to heat the tank itself above 600degC. I think. I didn't actually run the math on that. "Stainless steel as an insulator". heh.Yes, they’re thin enough that the quantity of heat transferred (∝ cross sectional area * conductivity * time * ΔT / length) will be small. Thermal energy will rapidly spread away from the skinny clip with the tank acting as a massive heat sink. So not a problem.
It would be so interesting to see the heat-gradient map supercomputer simulations SpaceX have been doing on their TPS.
Here’s a way to think about why touching a very hot, low-density, low-conductivity material is surprisingly safe. Consider two imaginary cases, then a real one:It would be so interesting to see the heat-gradient map supercomputer simulations SpaceX have been doing on their TPS.
I recall being quite surprised the first time I came across a video of the creation of the ceramic tile material. The technician or researcher or whoever had on thick heat resistant gloves and removed a tile from a very hot furnace with a long handled tongs. He set it on a table, took off the gloves, and picked up the tile bare handed, while it was still glowing red hot. How are these tiles transmitting enough heat to the backside to create significant heat related problems to the TPS substrates and to the ship's skin itself? I ask this with all sincerity, I can't see the problem from my uneducated perspective.
It would be so interesting to see the heat-gradient map supercomputer simulations SpaceX have been doing on their TPS.
I recall being quite surprised the first time I came across a video of the creation of the ceramic tile material. The technician or researcher or whoever had on thick heat resistant gloves and removed a tile from a very hot furnace with a long handled tongs. He set it on a table, took off the gloves, and picked up the tile bare handed, while it was still glowing red hot. How are these tiles transmitting enough heat to the backside to create significant heat related problems to the TPS substrates and to the ship's skin itself? I ask this with all sincerity, I can't see the problem from my uneducated perspective.
True, and we don't know what the pins are made from. Probably steel but it might be a different grade from that used on the skin.It would be so interesting to see the heat-gradient map supercomputer simulations SpaceX have been doing on their TPS.
I recall being quite surprised the first time I came across a video of the creation of the ceramic tile material. The technician or researcher or whoever had on thick heat resistant gloves and removed a tile from a very hot furnace with a long handled tongs. He set it on a table, took off the gloves, and picked up the tile bare handed, while it was still glowing red hot. How are these tiles transmitting enough heat to the backside to create significant heat related problems to the TPS substrates and to the ship's skin itself? I ask this with all sincerity, I can't see the problem from my uneducated perspective.
That video, I believe, was for Space Shuttle tiles, and things have moved on quite a lot since the Space Shuttle.
1. An airframe made of stainless can handle > 2x the temperature of Aluminum in the Space Shuttle
2. Superwool wasn't around in the 1970s.
3. Bracket attachment mechanism instead of glue means there's metal in the tile that will conduct and hold heat.
In short, different design characteristics means different requirements.
I suspect somewhere near the top of the clip the metal slides past each side, its really hard to see exactly how the top of the clip is arranged, really need a super hi res photo of heaps of clips from different angles.
Picture attached black lines indicate very top section might not be one piece but the left and right sides slide over each other, or past each other when spring is compressed. The lower spring section ( green arrow) forces clip apart once in position in tile, the collar simply stops it from expanding too far.
Thought of a reason why they are going to all this trouble: space shuttle issues with broken tiles, I dont think it was possible for the astronauts to replace broken tiles while in space, quite hard to
replace a tile when your in space if need to use glue etc, if it just clips in place, you can fix it before re-entry very simply.
I suspect somewhere near the top of the clip the metal slides past each side, its really hard to see exactly how the top of the clip is arranged, really need a super hi res photo of heaps of clips from different angles.
Picture attached black lines indicate very top section might not be one piece but the left and right sides slide over each other, or past each other when spring is compressed. The lower spring section ( green arrow) forces clip apart once in position in tile, the collar simply stops it from expanding too far.
Thought of a reason why they are going to all this trouble: space shuttle issues with broken tiles, I dont think it was possible for the astronauts to replace broken tiles while in space, quite hard to
replace a tile when your in space if need to use glue etc, if it just clips in place, you can fix it before re-entry very simply.
This is exactly how I had assumed it was working. Nice simple design, easy to manufacture, easy to use.
Digging around a bit, it looks like Superwool (various grades) is inferior to LI-900 (Shuttle) tiles by a mass-efficiency figure of merit (conductivity-1 * density-1, data sources below). On the other hand, the Superwool data is for a material with typical applications in “Chimney insulation, Process heater linings, Pipe wrap, Annealing furnace linings...” none of which call strong efforts to minimize mass.
• Are there higher conductivity-1 * density-1 grades of Superwool or equivalent?
• Do we know what the actual blanket material is on SS?
Using an interim blanket material with an anticipated bespoke upgrade would be plausible. Producing a low-density felt based on a fancier ceramic-fiber feedstock shouldn’t be too capital intensive.
Data sources
Superwool: https://www.morganthermalceramics.com/media/1814/sw_blanket_data_sheet_english_1.pdf
LI-900 Tiles: http://mae-nas.eng.usu.edu/MAE_5420_Web/section3/appendix3.pdf
What about the heat tolerance of the clips themselves? They stick up beyond the blanket. Is there any high temperature metal that can be welded to stainless steel? What happens if they're heated to the annealing point? They might have to stay as cool as the body of the vehicle.
Great question.
You may have answered your own question. The clips probably can be heated to the annealing point, all the way to almost melting (say 1300 degC). The clips once engaged do not need to hold a lot of force, the full strength of stainless steel isn't required.
If I understand the great discussion above on springs in the clips correctly, the springs only compress on installation, so heat effects on spring characteristics don't matter either (though R&R of tiles may require R&R of the clips?)
If that's the same clip I've seen, the tech was very careful to touch only the corners where cooling, even on the short trip from oven to table, would be maximized.Here’s a way to think about why touching a very hot, low-density, low-conductivity material is surprisingly safe. Consider two imaginary cases, then a real one:It would be so interesting to see the heat-gradient map supercomputer simulations SpaceX have been doing on their TPS.
I recall being quite surprised the first time I came across a video of the creation of the ceramic tile material. The technician or researcher or whoever had on thick heat resistant gloves and removed a tile from a very hot furnace with a long handled tongs. He set it on a table, took off the gloves, and picked up the tile bare handed, while it was still glowing red hot. How are these tiles transmitting enough heat to the backside to create significant heat related problems to the TPS substrates and to the ship's skin itself? I ask this with all sincerity, I can't see the problem from my uneducated perspective.
-- If an imaginary material had zero thermal conductivity it would transfer no heat, no matter how hot it was.
-- If an imaginary material had zero heat capacity it would have no heat to transfer, no matter how hot it was.
-- If a real material has very low thermal conductivity and very low heat capacity (both associated with low density), these properties in combination limit transfer to very, very little heat, despite high initial temperatures.
In other words, only heat near the surface matters (low conductivity), and there just isn’t much heat there (low capacity). The surface cools very fast. Fingers are safe because they have relatively high heat capacity and conductivity, and can therefore take up small amounts of heat without getting very hot. What makes the demos even more striking is that silica tiles, being somewhat transparent, can glow red even after the surface has cooled.
Note that the only the low thermal conductivity helps with insulation. Where there’s an effectively unlimited source of external heat (the TPS situation), low heat capacity in the material itself doesn’t help.
Actually, I'm impressed by the quality of some of the shots. Some of those photographers are using some fine (and heavy) glass.I suspect somewhere near the top of the clip the metal slides past each side, its really hard to see exactly how the top of the clip is arranged, really need a super hi res photo of heaps of clips from different angles.
Picture attached black lines indicate very top section might not be one piece but the left and right sides slide over each other, or past each other when spring is compressed. The lower spring section ( green arrow) forces clip apart once in position in tile, the collar simply stops it from expanding too far.
Thought of a reason why they are going to all this trouble: space shuttle issues with broken tiles, I dont think it was possible for the astronauts to replace broken tiles while in space, quite hard to
replace a tile when your in space if need to use glue etc, if it just clips in place, you can fix it before re-entry very simply.
This is exactly how I had assumed it was working. Nice simple design, easy to manufacture, easy to use.
Yeah conceptually it remembers me on this kinda clips. IMO WE need more hq photos to really confirm how exact is that shape.
(https://www.czyh.com/uploadfiles/103.224.250.31/webid233/source/201604/146018683631.jpg)
It would be so interesting to see the heat-gradient map supercomputer simulations SpaceX have been doing on their TPS.We may not find out, this decade, how Sx does overall TPS design & testing in detail, due to the apparent general Sx principle that taking the time to explain things, beyond acute necessity or management mood, puts the schedule in peril.
In fact, if you want to keep something thermally insulated in a cryogenic vacuum environment, the strategy is to have a reduced surface of contact with the cryo surfaces with a very low conductivity material.Too bad that the reentry plasma in front of a blunt body has nothing in common with vacuum.
Stainless steel is one of the least heat-conductive metals. It is typically used as a thermal break, for example on 3d printers or the handle of your frying pan. There are certain grades of stainless which conduct even less heat than others.Whilst true... compared to thermal protection systems 14W /mK is comparatively very heat conductive, insulators are orders of magnitude less conductive. E.g. standard building PIR insulation is down at 0.02 W/mK
Eg thermal conductivity of copper at room temperature is about 400 W/m K. Aluminum is 240 W/m K. Stainless steel is 14 W/m K. Hastelloy C steel gets down to 8.7 W/m K.
Manganese at 7 W/m K and inconel at 15 W/m K are the only real competition among metals.
(To compare: a ceramic coffee mug is about 3.8 W/m K; a glass is 1.1 W/m K. Among ceramics, zirconia is 3 W/m K and Aluminum Nitride is 150 W/m K.)
Comparing the thermal conductivity of the tile and the pin is irrelevant, since they are not in parallel.Yes, where I say “tile”, please read “tile+insulation stack”.
If the pins were in parallel of a perfect insulant, the total heat flow going through the tile would go through them, no matter the conductivity.
If you have to compare the conductivity of the stainless steel pins to anything, it's either the conductivity of the double layer air+insulant or the insulating blanket.
Whatever the case, they are both at least 2 orders of magnitude less conductive than the pins. So they can afford at least 100 times more surface before they become the main thermal path.
Which they hopefully are. Otherwise the pins would be badly designed.
Another thing that could be a concern with the pins would be the heat flow density. They will cause spot heating on the tanks. Which is fine, as long as the heat flow stays low enough.
Ratio of heat flows, pins/tile, approximating pin length = tile thickness (etc.):
A = cross sectional area of component
C = thermal conductivity of component material
(A_pins * C_pins) / ( A_tile * C_tile) ≈ actual importance of heat flow through pins.
Here’s a way to think about why touching a very hot, low-density, low-conductivity material is surprisingly safe. Consider two imaginary cases, then a real one:It would be so interesting to see the heat-gradient map supercomputer simulations SpaceX have been doing on their TPS.
I recall being quite surprised the first time I came across a video of the creation of the ceramic tile material. The technician or researcher or whoever had on thick heat resistant gloves and removed a tile from a very hot furnace with a long handled tongs. He set it on a table, took off the gloves, and picked up the tile bare handed, while it was still glowing red hot. How are these tiles transmitting enough heat to the backside to create significant heat related problems to the TPS substrates and to the ship's skin itself? I ask this with all sincerity, I can't see the problem from my uneducated perspective.
-- If an imaginary material had zero thermal conductivity it would transfer no heat, no matter how hot it was.
-- If an imaginary material had zero heat capacity it would have no heat to transfer, no matter how hot it was.
-- If a real material has very low thermal conductivity and very low heat capacity (both associated with low density), these properties in combination limit transfer to very, very little heat, despite high initial temperatures.
In other words, only heat near the surface matters (low conductivity), and there just isn’t much heat there (low capacity). The surface cools very fast. Fingers are safe because they have relatively high heat capacity and conductivity, and can therefore take up small amounts of heat without getting very hot. What makes the demos even more striking is that silica tiles, being somewhat transparent, can glow red even after the surface has cooled.
Note that the only the low thermal conductivity helps with insulation. Where there’s an effectively unlimited source of external heat (the TPS situation), low heat capacity in the material itself doesn’t help.
It would be so interesting to see the heat-gradient map supercomputer simulations SpaceX have been doing on their TPS.
I recall being quite surprised the first time I came across a video of the creation of the ceramic tile material. The technician or researcher or whoever had on thick heat resistant gloves and removed a tile from a very hot furnace with a long handled tongs. He set it on a table, took off the gloves, and picked up the tile bare handed, while it was still glowing red hot. How are these tiles transmitting enough heat to the backside to create significant heat related problems to the TPS substrates and to the ship's skin itself? I ask this with all sincerity, I can't see the problem from my uneducated perspective.
That video, I believe, was for Space Shuttle tiles, and things have moved on quite a lot since the Space Shuttle.
1. An airframe made of stainless can handle > 2x the temperature of Aluminum in the Space Shuttle
2. Superwool wasn't around in the 1970s.
3. Bracket attachment mechanism instead of glue means there's metal in the tile that will conduct and hold heat.
In short, different design characteristics means different requirements.
[...]I thought ETurner explained it quite clearly...? The demo does not show some magic material that can never burn anything no matter what - it shows hot samples being carefully removed from a furnace and allowed to cool down before being touched. The time needed is just a few seconds due to the combination of low thermal capacity and conductivity but it is not like you could just stick your hand into the furnace and grab it at 2200°F directly.[...][...]
How are these tiles transmitting enough heat to the backside to create significant heat related problems to the TPS substrates and to the ship's skin itself? I ask this with all sincerity, I can't see the problem from my uneducated perspective.
I think midaswelby's point is entirely valid and correct. Post-Shuttle TPS ceramics should have similar-or-better thermal performance to the famous "hold the glowing tile" demo, so where exactly is the backside heat problem? ???
[...]
that shuttle tile video posted by twark main was very interesting.Silica (not Silicone), no binder (the fibres are sintered together by heat), and the coating is Reaction Cured Glass (Borosilicate). STS tile composition manufacture is pretty extensively documented publicly, and the documents we have on the tiles SpaceX are using (Florida EPA report) indicate their tiles are nearly identical apart from dimensions and a slightly different waterproofing agent.
Seems silicone fibres and water ( probably other binding agents I would think), then a thin layer of ceramic material spray painted on top. I wonder what that ceramic coating was made of? thanks for posting that terrific stuff.
[...]I thought ETurner explained it quite clearly...? The demo does not show some magic material that can never burn anything no matter what - it shows hot samples being carefully removed from a furnace and allowed to cool down before being touched. The time needed is just a few seconds due to the combination of low thermal capacity and conductivity but it is not like you could just stick your hand into the furnace and grab it at 2200°F directly.[...][...]
How are these tiles transmitting enough heat to the backside to create significant heat related problems to the TPS substrates and to the ship's skin itself? I ask this with all sincerity, I can't see the problem from my uneducated perspective.
I think midaswelby's point is entirely valid and correct. Post-Shuttle TPS ceramics should have similar-or-better thermal performance to the famous "hold the glowing tile" demo, so where exactly is the backside heat problem? ???
[...]
This is a demo designed to demonstrate material properties, not how it handles reentry.
That demo would be holding it in one hand and heating the other side to the same temperature as the furnace with a torch for 10+ minutes.
BTW, the "backside temperature/heat problem" will most likely never be completely "solved" since it is one of the primary TPS design factors. If the temperature behind the TPS (or one of its layers) is guaranteed to stay far below the limit no matter what it means that your can either expand the envelope or make the TPS lighter.
Everyday Astronaut
How’re the titles gonna stay on during ascent? I’m still a little surprised nature didn’t have the right idea and do the tiles more like scales. On ascent there’d be less room for aerodynamic forces to rip them off and it’d allow for expansion and contraction of the steel
Elon Musk
That said, I’m not entirely convinced that this couldn’t be done with several overlapping scales of metal sheet with an insulator between scale armor & primary structure.
Elon says tile failure was caused by header tank vent:
https://twitter.com/elonmusk/status/1442630681360752640
Also, per LabPadre Rover Cam, pad is mostly clear, with just final few vehicles doing closeouts.
Most vents we have seen seem to be bang-bang controlled (i.e. go over pressure 1 - fully open until below pressure 2) so there might not be any way to decrease the flow.Elon says tile failure was caused by header tank vent:
[tweet]
Also, per LabPadre Rover Cam, pad is mostly clear, with just final few vehicles doing closeouts.
Interesting reason for the tiles blown off.
It seems to me that placing the vent on the wrong side, or not making the tiles attachments such that they can withstand a vent is such a stupid design error that it isn't an error. I throw at you this idea, could be possible that there was an error in the vent controll code configuration, someone forgotten to turn down the mass flow of the vent (below a value they know that does not cause damages, at the expens of a longer vent time), causing the damage?
Elon Musk
That said, I’m not entirely convinced that this couldn’t be done with several overlapping scales of metal sheet with an insulator between scale armor & primary structure.
QuoteElon Musk
That said, I’m not entirely convinced that this couldn’t be done with several overlapping scales of metal sheet with an insulator between scale armor & primary structure.
I have to admit, been pondering this design choice for a while, and wondering why this approach hasn't been pursued, using tungsten as the surface material. Great thermal characteristics, although I don't know how bad the high-temperature oxidation would be. Weight is an obvious issue too, but the toughness problem would be solved.
This is a hard problem. And I think the big reason to be hesitant of these refractory metals isn't that they're heavy but that working with them, and making them into the right shape, is pretty expensive and hard.
QuoteElon Musk
That said, I’m not entirely convinced that this couldn’t be done with several overlapping scales of metal sheet with an insulator between scale armor & primary structure.
I have to admit, been pondering this design choice for a while, and wondering why this approach hasn't been pursued, using tungsten as the surface material. Great thermal characteristics, although I don't know how bad the high-temperature oxidation would be. Weight is an obvious issue too, but the toughness problem would be solved.
Need a high-tech metallurgist to come up with foamed tungsten plate as a primary heat shield surface. Bulletproof!
I have to admit, been pondering this design choice for a while, and wondering why this approach hasn't been pursuedTRL.
I tend to disagree with this sentence. As a matter of fact, during shuttle era, ceramic tiles worked really well for their purposes that were "heat shielding". The Columbia disaster was due to an underestimation of tiles damages by the foam impacting during ascent. And regarding the humongous maintenance necessary to replace them we really hope that SpaceX have found a viable solution. Tiles are not designed to sustain mechanical stresses due to impact with solid objects nor to sustain any pressure gas realeased on them, so to me they are still the best compromise to succeed. I would wait for the first starship to test it before throwing ceramics under the bus.This is a hard problem. And I think the big reason to be hesitant of these refractory metals isn't that they're heavy but that working with them, and making them into the right shape, is pretty expensive and hard.
100% agree with you. But we all know that ceramics, while good at thermal and weight, suck at toughness. Shuttle tiles showed us that was a bad choice for reusability.
What's needed is a metal "scale" that has the thermal tolerance and physical toughness, and then work the engineering and processing to get the weight down.
Inconel isn't really any better than 310 Stainless (not pictured here, but Inconel and SS 310 have basically the same use temperature). Tungsten is a bit more than twice as dense as both, but it is FAR higher temperature. So you may be able to use just a thin section of tungsten, maybe multiple layers with spacers, then an insulator and stainless or whatever beneath that.
Inconel isn't really any better than 310 Stainless (not pictured here, but Inconel and SS 310 have basically the same use temperature). Tungsten is a bit more than twice as dense as both, but it is FAR higher temperature. So you may be able to use just a thin section of tungsten, maybe multiple layers with spacers, then an insulator and stainless or whatever beneath that.
I think you are using the wrong chart for temperature. That chart is for metals that one intends to use under stress - i.e. they keep their physical properties intact.
304 Stainless can go to 1300degC *if* you don't care very much about the strength or corrosion resistance of it. It is likely in the current design that the pins will see close to this, but compared the ceramics, the pins are tough even after annealing.
So what one wants is the metal that has the a sufficiently high melting point with the lowest density while not losing all its corrosion resistance. I don't know what that would be, but I'd bet someone at SpaceX is looking at it.
Physical strength of the metal would be pretty far down the list of requirements for a metal tile.
I tend to disagree with this sentence. [snip]
I wonder why they don't use ablative bolt on plates for the first few flights. SS isn't going to have a rapid turnaround for a while. Maybe they are heavier than ceramics? Seems like the weight penalty for the first few flights with no payload should be acceptable if it allows them to get up to orbit and back. Then figure out what is best for heat shield.
but my point on ceramics was based on the fact that after every shuttle mission, there were significant efforts needed to restore the tiles that were damaged during the mission.STS tile damage was down to two factors:
and tile installers spitting in the silicone to retard curing during applicationYou have got to be kidding me. But a little research shows that, no, you're not. https://www.washingtonpost.com/wp-srv/articles/A38144-2003Feb6.html (https://www.washingtonpost.com/wp-srv/articles/A38144-2003Feb6.html).
I wonder why they don't use ablative bolt on plates for the first few flights. SS isn't going to have a rapid turnaround for a while. Maybe they are heavier than ceramics? Seems like the weight penalty for the first few flights with no payload should be acceptable if it allows them to get up to orbit and back. Then figure out what is best for heat shield.
the main problem is the added r&d
I wonder why they don't use ablative bolt on plates for the first few flights. SS isn't going to have a rapid turnaround for a while. Maybe they are heavier than ceramics? Seems like the weight penalty for the first few flights with no payload should be acceptable if it allows them to get up to orbit and back. Then figure out what is best for heat shield.
the main problem is the added r&d
The main problem is that they learn nothing by chasing a tangent that is not going to be used. Better to learn by trying the approach they actually intend to use, then trouble shooting any problems that arise by analyzing the data.
Does corrosion resistance carry over to chemical resistance to all the species that will be created? The plasma itself won't touch metal but there will be some fierce compression heating and gas migration through the shock wave.Inconel isn't really any better than 310 Stainless (not pictured here, but Inconel and SS 310 have basically the same use temperature). Tungsten is a bit more than twice as dense as both, but it is FAR higher temperature. So you may be able to use just a thin section of tungsten, maybe multiple layers with spacers, then an insulator and stainless or whatever beneath that.
I think you are using the wrong chart for temperature. That chart is for metals that one intends to use under stress - i.e. they keep their physical properties intact.
304 Stainless can go to 1300degC *if* you don't care very much about the strength or corrosion resistance of it. It is likely in the current design that the pins will see close to this, but compared the ceramics, the pins are tough even after annealing.
So what one wants is the metal that has the a sufficiently high melting point with the lowest density while not losing all its corrosion resistance. I don't know what that would be, but I'd bet someone at SpaceX is looking at it.
Physical strength of the metal would be pretty far down the list of requirements for a metal tile.
A while back didn't Elon tweet something about rope like caulking between tiles? The closest we've seen is the blanket. It's the type of thing they might have in the toolbox but don't want to use if they don't have to. It would do a lot for vibration and lateral loads. Mental image: pounding oakum on wooden ships.
I tend to disagree with this sentence. [snip]
I appreciate the perspective, but my point on ceramics was based on the fact that after every shuttle mission, there were significant efforts needed to restore the tiles that were damaged during the mission. Keeping in mind SpaceX's stated goal of high-frequency reusability, a ceramic tile TPS that requires refurbishment flight after flight runs counter to that goal.
Yes, the early TPS is tiles. It's a relatively-cheap, known quantity. But to get the ultimate goal, I think fragile ceramics is a poor choice, and I'd be looking for something more robust. And I'd gently point out that Elon has voiced skepticism on the ceramic tiles, too.
Personally, I think the whole system as it stands is too sketchy to survive re-entry, especially the clip-to-tile interface (works good in compression, not so much with lateral loads). But it's certainly going to be a good show, and I hope SpaceX proves me wrong.
I know Shuttle was the first reentry vehicle to use reusable tiles instead of an ablative shield, but there's another more recent example we could look to as well. Sure, it's much smaller, but the tiles seem much more successful to date.
Stupid tiles >:(If this analysis is correct (and it looks correct) then
Heat shield will be the main challenge of spaceship reusability because tiles were, are, and guaranteed to remain a pain in the ass for some time, imo. But there are no other tested and working reusable alternatives for that size of ships. Anyway the ss 20 test will be crucial . In case of serious issues with the tiles in the re-entry, probably a scheme of a rapid-replaceable ablative will be good to get started prototyping asap. If either tiles or ablative can work, it gives time for R&D on alternatives, that must be aggressive ($$), unless tiles prove to be good (and safe) enough also for the rapid reusable scenario. The biggest issue with the tiles i see even if they work, is fast and reliable inspection and replacement after re-entry and I am not talking just about surface inspection. If you want to relax/remove this step, the only way to be sure is to determine the number of re-entries before inspection and/or replacement. But for this you need statistical analysis and enough consistent real data (including failures), so you can set safe limits. I guess at least 10 ships destructive testing is needed, with the posibility of getting you nowhere, if 1 ship/heatshield of 10 fails on 2nd reentry, you are back on inspections after each reentry if you are not going to risk a 10% probability of failure.
QuoteEveryday Astronaut
How’re the titles gonna stay on during ascent? I’m still a little surprised nature didn’t have the right idea and do the tiles more like scales. On ascent there’d be less room for aerodynamic forces to rip them off and it’d allow for expansion and contraction of the steelQuoteElon Musk
That said, I’m not entirely convinced that this couldn’t be done with several overlapping scales of metal sheet with an insulator between scale armor & primary structure.
https://twitter.com/elonmusk/status/1442636642985160708
If tiles are not super thin, you get hot plasma “waterfalling” off edges of tiles, creating hotspots.
We should also take Elon ambitious plan of "rapid turnaround" with a grain of salt. Look at the F9 that has a record turnaround of dozens of days being suborbital. I would myself take a month as a success for orbital purposes. Surely this would impact an earth to earth use of Starship but frankly speaking I suspect that earth-earth SS is way down below in SpaceX priority list.A while back didn't Elon tweet something about rope like caulking between tiles? The closest we've seen is the blanket. It's the type of thing they might have in the toolbox but don't want to use if they don't have to. It would do a lot for vibration and lateral loads. Mental image: pounding oakum on wooden ships.
I tend to disagree with this sentence. [snip]
I appreciate the perspective, but my point on ceramics was based on the fact that after every shuttle mission, there were significant efforts needed to restore the tiles that were damaged during the mission. Keeping in mind SpaceX's stated goal of high-frequency reusability, a ceramic tile TPS that requires refurbishment flight after flight runs counter to that goal.
Yes, the early TPS is tiles. It's a relatively-cheap, known quantity. But to get the ultimate goal, I think fragile ceramics is a poor choice, and I'd be looking for something more robust. And I'd gently point out that Elon has voiced skepticism on the ceramic tiles, too.
Personally, I think the whole system as it stands is too sketchy to survive re-entry, especially the clip-to-tile interface (works good in compression, not so much with lateral loads). But it's certainly going to be a good show, and I hope SpaceX proves me wrong.
As for tiles being an expedient, you might be right but if the expedient is good enough... Turnaround time might be a place where reality and intentions have to find a compromise.
We saw the first go at mass tile inspection and servicing just a few weeks ago. It was slow but it was only a first try on an early design. If turnaround is 48 hours on a reasonably mature system I'd count that as a win. Aircraft like turnaround sounds great but we are talking rocket ships here.
QuoteEveryday Astronaut
How’re the titles gonna stay on during ascent? I’m still a little surprised nature didn’t have the right idea and do the tiles more like scales. On ascent there’d be less room for aerodynamic forces to rip them off and it’d allow for expansion and contraction of the steelQuoteElon Musk
That said, I’m not entirely convinced that this couldn’t be done with several overlapping scales of metal sheet with an insulator between scale armor & primary structure.
https://twitter.com/elonmusk/status/1442636642985160708
Here's a possible metal candidate for scales:
https://www.neonickel.com/generate-alloy-pdf/?id=42
"maintains strength and oxidation resistance up to 1232°C."
Not quite the 1477 degC needed, but close.
(1477 degC was the requirement for the space shuttle, not sure if SS is less or more for LEO)
BTW "maintain strength" means it was measured. It's likely still well above the 0.4 MPa for ceramic tiles almost all the way to melting.
We should also take Elon ambitious plan of "rapid turnaround" with a grain of salt. Look at the F9 that has a record turnaround of dozens of days being suborbital. I would myself take a month as a success for orbital purposes. Surely this would impact an earth to earth use of Starship but frankly speaking I suspect that earth-earth SS is way down below in SpaceX priority list.A while back didn't Elon tweet something about rope like caulking between tiles? The closest we've seen is the blanket. It's the type of thing they might have in the toolbox but don't want to use if they don't have to. It would do a lot for vibration and lateral loads. Mental image: pounding oakum on wooden ships.
I tend to disagree with this sentence. [snip]
I appreciate the perspective, but my point on ceramics was based on the fact that after every shuttle mission, there were significant efforts needed to restore the tiles that were damaged during the mission. Keeping in mind SpaceX's stated goal of high-frequency reusability, a ceramic tile TPS that requires refurbishment flight after flight runs counter to that goal.
Yes, the early TPS is tiles. It's a relatively-cheap, known quantity. But to get the ultimate goal, I think fragile ceramics is a poor choice, and I'd be looking for something more robust. And I'd gently point out that Elon has voiced skepticism on the ceramic tiles, too.
Personally, I think the whole system as it stands is too sketchy to survive re-entry, especially the clip-to-tile interface (works good in compression, not so much with lateral loads). But it's certainly going to be a good show, and I hope SpaceX proves me wrong.
As for tiles being an expedient, you might be right but if the expedient is good enough... Turnaround time might be a place where reality and intentions have to find a compromise.
We saw the first go at mass tile inspection and servicing just a few weeks ago. It was slow but it was only a first try on an early design. If turnaround is 48 hours on a reasonably mature system I'd count that as a win. Aircraft like turnaround sounds great but we are talking rocket ships here.
Never been done before and never will be done, until it is done and then its obviously just routineWe should also take Elon ambitious plan of "rapid turnaround" with a grain of salt. Look at the F9 that has a record turnaround of dozens of days being suborbital. I would myself take a month as a success for orbital purposes. Surely this would impact an earth to earth use of Starship but frankly speaking I suspect that earth-earth SS is way down below in SpaceX priority list.A while back didn't Elon tweet something about rope like caulking between tiles? The closest we've seen is the blanket. It's the type of thing they might have in the toolbox but don't want to use if they don't have to. It would do a lot for vibration and lateral loads. Mental image: pounding oakum on wooden ships.
I tend to disagree with this sentence. [snip]
I appreciate the perspective, but my point on ceramics was based on the fact that after every shuttle mission, there were significant efforts needed to restore the tiles that were damaged during the mission. Keeping in mind SpaceX's stated goal of high-frequency reusability, a ceramic tile TPS that requires refurbishment flight after flight runs counter to that goal.
Yes, the early TPS is tiles. It's a relatively-cheap, known quantity. But to get the ultimate goal, I think fragile ceramics is a poor choice, and I'd be looking for something more robust. And I'd gently point out that Elon has voiced skepticism on the ceramic tiles, too.
Personally, I think the whole system as it stands is too sketchy to survive re-entry, especially the clip-to-tile interface (works good in compression, not so much with lateral loads). But it's certainly going to be a good show, and I hope SpaceX proves me wrong.
As for tiles being an expedient, you might be right but if the expedient is good enough... Turnaround time might be a place where reality and intentions have to find a compromise.
We saw the first go at mass tile inspection and servicing just a few weeks ago. It was slow but it was only a first try on an early design. If turnaround is 48 hours on a reasonably mature system I'd count that as a win. Aircraft like turnaround sounds great but we are talking rocket ships here.
Whilst I guess it is ambitious, its also, in Musk's own words, absolutely necessary to <24hr turnaround. So they will work and work at it until it works.
Lars-J mentioned a few posts back the tiles have to stay intact during maxQ, well I think a couple of days ago we saw what happens when fast travelling gas hits the tiles, they fly off rather spectacularly. Did spacex purposely direct the gas at the tiles to see what would happen? or was it just an accident which shows what might be a worrying unplanned tile test. I guess the angle of that gas venting plays a role, but as the tiles are at the moment I'm expecting as mass shedding during launch and ascent.
Stupid tiles >:(It's routine to tap a grinder wheel before install to see if it has a hidden crack. It's a very different sound. ISTM this might be adaptable to the already installed tiles and could be robotized. One arm on a lift with a tapper and contact sound transducer could conceivably do an 8x8 section of tiles at a second each. The another 30-45 seconds to reposition for the next section. Call it an overall average of 2 seconds per tile per arm.
Heat shield will be the main challenge of spaceship reusability because tiles were, are, and guaranteed to remain a pain in the ass for some time, imo. But there are no other tested and working reusable alternatives for that size of ships. Anyway the ss 20 test will be crucial . In case of serious issues with the tiles in the re-entry, probably a scheme of a rapid-replaceable ablative will be good to get started prototyping asap. If either tiles or ablative can work, it gives time for R&D on alternatives, that must be aggressive ($$), unless tiles prove to be good (and safe) enough also for the rapid reusable scenario. The biggest issue with the tiles i see even if they work, is fast and reliable inspection and replacement after re-entry and I am not talking just about surface inspection. If you want to relax/remove this step, the only way to be sure is to determine the number of re-entries before inspection and/or replacement. But for this you need statistical analysis and enough consistent real data (including failures), so you can set safe limits. I guess at least 10 ships destructive testing is needed, with the posibility of getting you nowhere, if 1 ship/heatshield of 10 fails on 2nd reentry, you are back on inspections after each reentry if you are not going to risk a 10% probability of failure.
Layering tiles like scales is also complicated by the fact that the tiles won’t just experience airflow in one direction. During the ascent the flow is pretty much perpendicular to the flow during reentry, and you want to avoid tiles being ripped off at Max-Q.And replacement becomes difficult.
I've been struggling with the reason for this turnaround time and what I come up with is the launch surge necessary to refuel an accumulation tanker. I don't have Elon's tweets at hand but could he mean SH and the pad and not SS?We should also take Elon ambitious plan of "rapid turnaround" with a grain of salt. Look at the F9 that has a record turnaround of dozens of days being suborbital. I would myself take a month as a success for orbital purposes. Surely this would impact an earth to earth use of Starship but frankly speaking I suspect that earth-earth SS is way down below in SpaceX priority list.A while back didn't Elon tweet something about rope like caulking between tiles? The closest we've seen is the blanket. It's the type of thing they might have in the toolbox but don't want to use if they don't have to. It would do a lot for vibration and lateral loads. Mental image: pounding oakum on wooden ships.
I tend to disagree with this sentence. [snip]
I appreciate the perspective, but my point on ceramics was based on the fact that after every shuttle mission, there were significant efforts needed to restore the tiles that were damaged during the mission. Keeping in mind SpaceX's stated goal of high-frequency reusability, a ceramic tile TPS that requires refurbishment flight after flight runs counter to that goal.
Yes, the early TPS is tiles. It's a relatively-cheap, known quantity. But to get the ultimate goal, I think fragile ceramics is a poor choice, and I'd be looking for something more robust. And I'd gently point out that Elon has voiced skepticism on the ceramic tiles, too.
Personally, I think the whole system as it stands is too sketchy to survive re-entry, especially the clip-to-tile interface (works good in compression, not so much with lateral loads). But it's certainly going to be a good show, and I hope SpaceX proves me wrong.
As for tiles being an expedient, you might be right but if the expedient is good enough... Turnaround time might be a place where reality and intentions have to find a compromise.
We saw the first go at mass tile inspection and servicing just a few weeks ago. It was slow but it was only a first try on an early design. If turnaround is 48 hours on a reasonably mature system I'd count that as a win. Aircraft like turnaround sounds great but we are talking rocket ships here.
Whilst I guess it is ambitious, its also, in Musk's own words, absolutely necessary to <24hr turnaround. So they will work and work at it until it works.
cork...Sounds like a really expensive way to go - baking in extra launch costs for every launch. Not to mention with the planned flight rate there'd be no cork left in the world in very short order (remember, the goal is thousands of launches, not a few).
Ablative spray on cork is a terrible idea... for a reusable gas-n-go system. Which is the plan with Starship.The TPS is a solution under investigation. There are many possible outcomes. It may be that the cylindrical portion of the rocket will have no problems with the tiles as they are. Other parts may need another solution or special application techniques. And Elon has been clear that cooling with liquid propellant is still on the table. As Lars-J says, "no reason to panic". I do think TPS is one of the most difficult remaining problems, but not the only one.
Tiles make a lot more sense. Easy to inspect, easy to replace. (which should be infrequent) Are the tiles fully finished? Of course not, but there is no reason to panic.
Lots of people dissing tiles... But, if the Shuttle and Starship use tiles... - you know, there may be very good reasons for that. Weight to efficiency ratio is unbeatable (until the day where kryptonite and unobtainium and superconducting force fields come around...).
Lots of people dissing tiles... But, if the Shuttle and Starship use tiles... - you know, there may be very good reasons for that. Weight to efficiency ratio is unbeatable (until the day where kryptonite and unobtainium and superconducting force fields come around...).
Not necessarily "dissing" tiles, but observing that ceramic tiles have a history of fragility, whether by ice impacts or launch vibrations. By their nature, they break easily.
Shuttle used tiles because that was the best that 1970's technology had to offer. I have no inside knowledge of an obvious better solution, but I can certainly make the case that SpaceX would WANT a better solution. Sure, not today. But a year, or five, down the road? Absolutely.
And it won't have to be exceptionally exotic, but it may require some crafty technology to implement. And really, isn't that kind of what SpaceX is pretty good at doing?
Maybe they find a way to make the ceramic much tougher. Or maybe they find a way to make a metal tile. Doesn't have to be a "scale". But it ought to be stout, and highly reusable. And light.
I just think the current tile solution is relatively cheap and fast. And will probably work about as well as anything cheap and fast works.
Shuttle era would have had some access to hot structure and metallic TPS work from X-20, and some other semi-military stuff (what was it called? HAVE REGION or something similar?)
Cheap and fast is the way to go . If the current set up is a bit to cheap and fast then it will need to be less so. Such is life.Lots of people dissing tiles... But, if the Shuttle and Starship use tiles... - you know, there may be very good reasons for that. Weight to efficiency ratio is unbeatable (until the day where kryptonite and unobtainium and superconducting force fields come around...).
Not necessarily "dissing" tiles, but observing that ceramic tiles have a history of fragility, whether by ice impacts or launch vibrations. By their nature, they break easily.
Shuttle used tiles because that was the best that 1970's technology had to offer. I have no inside knowledge of an obvious better solution, but I can certainly make the case that SpaceX would WANT a better solution. Sure, not today. But a year, or five, down the road? Absolutely.
And it won't have to be exceptionally exotic, but it may require some crafty technology to implement. And really, isn't that kind of what SpaceX is pretty good at doing?
Maybe they find a way to make the ceramic much tougher. Or maybe they find a way to make a metal tile. Doesn't have to be a "scale". But it ought to be stout, and highly reusable. And light.
I just think the current tile solution is relatively cheap and fast. And will probably work about as well as anything cheap and fast works.
How about a honeycomb of holes drilled partially through from the inside so that if the steel starts ablating away, instead of rupturing it begins sweating gas in that portion.Steel would soften and melt before ablating.
Well, you would certainly get some if you start venting oxygen through holes in hot metal....How about a honeycomb of holes drilled partially through from the inside so that if the steel starts ablating away, instead of rupturing it begins sweating gas in that portion.Steel would soften and melt before ablating.
Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
https://mobile.twitter.com/elonmusk/status/1314741760568954880 (https://mobile.twitter.com/elonmusk/status/1314741760568954880)
I remember Elon mentioned awhile ago that they're considering using transpiration cooling on some areas. In light of recent tile blowaway event, I wonder if they have completely moved away from that or still have transpiration cooling as an option, at least in areas difficult to cover with heat tiles.
https://mobile.twitter.com/elonmusk/status/1314741760568954880 (https://mobile.twitter.com/elonmusk/status/1314741760568954880)Yep, more than half of the hull area is also the walls of the cryogenic LOX and LCH4. Those 3 mm thick walls are basically being actively cooled from the inside. Therefore, the "only" areas that need extra attention are the nose and the windward forward hull areas covered by the tiles. I suppose a conformal LCH4 "tank" just inside the hull (i.e., double hull, cooling pipes, whatever) and connected to the main tank would do it. The question is how much heat can you store in the LOX and LCH4? there is only enough of the stuff left to land the Starship, and the Raptors need for it to still be liquid.
I remember Elon mentioned awhile ago that they're considering using transpiration cooling on some areas. In light of recent tile blowaway event, I wonder if they have completely moved away from that or still have transpiration cooling as an option, at least in areas difficult to cover with heat tiles.
Lots of people dissing tiles... But, if the Shuttle and Starship use tiles... - you know, there may be very good reasons for that. Weight to efficiency ratio is unbeatable (until the day where kryptonite and unobtainium and superconducting force fields come around...).
Not necessarily "dissing" tiles, but observing that ceramic tiles have a history of fragility, whether by ice impacts or launch vibrations. By their nature, they break easily.
Shuttle used tiles because that was the best that 1970's technology had to offer. I have no inside knowledge of an obvious better solution, but I can certainly make the case that SpaceX would WANT a better solution. Sure, not today. But a year, or five, down the road? Absolutely.
And it won't have to be exceptionally exotic, but it may require some crafty technology to implement. And really, isn't that kind of what SpaceX is pretty good at doing?
Maybe they find a way to make the ceramic much tougher. Or maybe they find a way to make a metal tile. Doesn't have to be a "scale". But it ought to be stout, and highly reusable. And light.
I just think the current tile solution is relatively cheap and fast. And will probably work about as well as anything cheap and fast works.
We don't know if there are going to be problems with the existing tile arrangement or where those issues might be. But if there are, one area of concern was the flaps/hinges. I imagine that venting some methane there could be used to keep them cool. The problem with "storing heat in the LOX and CH4" is pressure increase. If they need extra methane they can easily adapt things so the header tank is a little larger.https://mobile.twitter.com/elonmusk/status/1314741760568954880 (https://mobile.twitter.com/elonmusk/status/1314741760568954880)Yep, more than half of the hull area is also the walls of the cryogenic LOX and LCH4. Those 3 mm thick walls are basically being actively cooled from the inside. Therefore, the "only" areas that need extra attention are the nose and the windward forward hull areas covered by the tiles. I suppose a conformal LCH4 "tank" just inside the hull (i.e., double hull, cooling pipes, whatever) and connected to the main tank would do it. The question is how much heat can you store in the LOX and LCH4? there is only enough of the stuff left to land the Starship, and the Raptors need for it to still be liquid.
I remember Elon mentioned awhile ago that they're considering using transpiration cooling on some areas. In light of recent tile blowaway event, I wonder if they have completely moved away from that or still have transpiration cooling as an option, at least in areas difficult to cover with heat tiles.
...Im am not an engineer. But we know that the tanks are pressurized otherwise the ship would crumple because of the excess weight (and the crew cabin will add weight, to the "blank" ss that iirc would sustain itself without pressurrization). If the tanks have holes, they can't be pressurized. I could be wrong though.
Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
I am dead certain that SpaceX explored all possible and impossible solutions for the TPS before settling on tiles. That they ended up going for tiles, despite their complexity and relative fragility, I think speaks volumes about the benefits of tiles.
...Im am not an engineer. But we know that the tanks are pressurized otherwise the ship would crumple because of the excess weight (and the crew cabin will add weight, to the "blank" ss that iirc would sustain itself without pressurrization). If the tanks have holes, they can't be pressurized. I could be wrong though.
Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
So the tiles blew off from the venting during the cryo test.Pinned on - it looks like the jet from the vents got under the edge of the blanket and created a pressure differential high enough to break and/or detach the tiles on top. This failure mode is much less likely for glued tiles
Do we know if the tiles that blew off were glued or pinned on?
They don't have a choice. The heat that penetrates the TPS in the after half of the hull will enter the LOX or LCH4 through the single-wall stainless steel. The question is what happens next. Sure, boil-off and and transpiration will carry heat away, and that gas can be used in clever ways to carry off even more heat, but the Raptors will still need enough liquid propellant to land safely.We don't know if there are going to be problems with the existing tile arrangement or where those issues might be. But if there are, one area of concern was the flaps/hinges. I imagine that venting some methane there could be used to keep them cool. The problem with "storing heat in the LOX and CH4" is pressure increase. If they need extra methane they can easily adapt things so the header tank is a little larger.https://mobile.twitter.com/elonmusk/status/1314741760568954880 (https://mobile.twitter.com/elonmusk/status/1314741760568954880)Yep, more than half of the hull area is also the walls of the cryogenic LOX and LCH4. Those 3 mm thick walls are basically being actively cooled from the inside. Therefore, the "only" areas that need extra attention are the nose and the windward forward hull areas covered by the tiles. I suppose a conformal LCH4 "tank" just inside the hull (i.e., double hull, cooling pipes, whatever) and connected to the main tank would do it. The question is how much heat can you store in the LOX and LCH4? there is only enough of the stuff left to land the Starship, and the Raptors need for it to still be liquid.
I remember Elon mentioned awhile ago that they're considering using transpiration cooling on some areas. In light of recent tile blowaway event, I wonder if they have completely moved away from that or still have transpiration cooling as an option, at least in areas difficult to cover with heat tiles.
But first you need small holes that go all the way through. I think what you get is either no holes or a big blowout. Not good for transpiration.Well, you would certainly get some if you start venting oxygen through holes in hot metal....How about a honeycomb of holes drilled partially through from the inside so that if the steel starts ablating away, instead of rupturing it begins sweating gas in that portion.Steel would soften and melt before ablating.
To clarify, yes, I was only talking about making a few broken tiles survivable for the crew.. and was assuming some sort of moderately expensive refurbishment of the vehicle eg cutting out an entire segment of the hull/tank and replacing it.Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
This sounds the opposite of reusable... perhaps worth thinking about to increase the odds of humans surviving a heat shield failure, but very far down the road after they have unmanned flight working reliably enough.
STS-1 lost 16 tiles and survived (as well as suffering extensive damage on many others). It’s not impossible Starship could lose some tiles and survive. I expect the first few orbital flights will have something to say on that front one way or another….
IIRC they‘re using transpiration cooling with water on the Falcon 9 first stage heatshield around the engines for reentry.https://mobile.twitter.com/elonmusk/status/1314741760568954880 (https://mobile.twitter.com/elonmusk/status/1314741760568954880)
I remember Elon mentioned awhile ago that they're considering using transpiration cooling on some areas. In light of recent tile blowaway event, I wonder if they have completely moved away from that or still have transpiration cooling as an option, at least in areas difficult to cover with heat tiles.
I think until we see it, it seems like we have to consider it aspirational. Elon achieves amazing stuff but he also throws some ideas at the wall which are actually dramatically harder/lower TRL than they first appear or perhaps he immediately realizes. I suspect transpiration cooling is one such. I don’t think we’ll see it.
Some ideas sound hard but can be done fairly quickly with care and effort. Others are more like research projects and can’t really be rushed much. (I guess I’m kind of just saying “are much lower TRL”.)
IIRC they‘re using transpiration cooling with water on the Falcon 9 first stage heatshield around the engines for reentry.I don't believe that is correct. I don't ever recall hearing anything like that and I think it would get enough airtime to be common knowledge if something like that existed.
Ok, might be evaporation cooling (on the backside of the heatshield) instead of transpiration cooling, but here it is directly from the horses mouth:IIRC they‘re using transpiration cooling with water on the Falcon 9 first stage heatshield around the engines for reentry.I don't believe that is correct. I don't ever recall hearing anything like that and I think it would get enough airtime to be common knowledge if something like that existed.
I know that. If i understood correctly the original post I quoted he meant that the main tanks could be made such that they can survive small holes caused by the local TPS failure....Im am not an engineer. But we know that the tanks are pressurized otherwise the ship would crumple because of the excess weight (and the crew cabin will add weight, to the "blank" ss that iirc would sustain itself without pressurrization). If the tanks have holes, they can't be pressurized. I could be wrong though.
Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
For transpiration cooling you don't directly apply "holes" to the tank wall. Instead you direct small amount of CH4 to manifolds with transpiration "pores" alongsides the ship hull to achieve cooling.
Ship 20 completed its first major test before the Orbital Test Flight. It was loaded with liquid nitrogen, pressurized, and hydraulic rams were used to simulate Raptor engine thrust.This sounds interesting because it means that apart from the tiles that have detached due to tank vent, the others have withstood the vibrations of this test well. Considering that it is the first time that a test of this kind has been done with the windward side entirely covered by tiles, IMO it is an excellent result, and I think there is ample margin for further improvement after the effect of the first reentries from orbital launches on tiles are known and data will be available.
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According to BradyKenniston, in the latest test on S20, in addition to the cryo test, hydraulic rams were used to simulate Raptor thrust.Ship 20 completed its first major test before the Orbital Test Flight. It was loaded with liquid nitrogen, pressurized, and hydraulic rams were used to simulate Raptor engine thrust.This sounds interesting because it means that apart from the tiles that have detached due to tank vent, the others have withstood the vibrations of this test well. Considering that it is the first time that a test of this kind has been done with the windward side entirely covered by tiles, IMO it is an excellent result, and I think there is ample margin for further improvement after the effect of the first reentries from orbital launches on tiles are known and data will be available.
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Well many of us in this topic said. if needed, SpaceX could mount articulated sprinkler system inside tank.Ok, might be evaporation cooling (on the backside of the heatshield) instead of transpiration cooling, but here it is directly from the horses mouth:IIRC they‘re using transpiration cooling with water on the Falcon 9 first stage heatshield around the engines for reentry.I don't believe that is correct. I don't ever recall hearing anything like that and I think it would get enough airtime to be common knowledge if something like that existed.
“We replaced the old composite structure with a high-temperature titanium structure to support rapid reuse,” Musk said. “The base heat shield will also be, in some parts, actively cooled with water.”
https://spaceflightnow.com/2018/05/11/spacex-debuts-an-improved-human-rated-model-of-the-falcon-9-rocket/
I know that. If i understood correctly the original post I quoted he meant that the main tanks could be made such that they can survive small holes caused by the local TPS failure.Yes that is what I meant. I remember hearing that the Starship tanks were not balloon tanks like the Centaur upper stage.. but I guess that does not mean they can land without pressure or support a 100 ton payload.
Ok, might be evaporation cooling (on the backside of the heatshield) instead of transpiration cooling, but here it is directly from the horses mouth:IIRC they‘re using transpiration cooling with water on the Falcon 9 first stage heatshield around the engines for reentry.I don't believe that is correct. I don't ever recall hearing anything like that and I think it would get enough airtime to be common knowledge if something like that existed.
“We replaced the old composite structure with a high-temperature titanium structure to support rapid reuse,” Musk said. “The base heat shield will also be, in some parts, actively cooled with water.”
https://spaceflightnow.com/2018/05/11/spacex-debuts-an-improved-human-rated-model-of-the-falcon-9-rocket/
...Im am not an engineer. But we know that the tanks are pressurized otherwise the ship would crumple because of the excess weight (and the crew cabin will add weight, to the "blank" ss that iirc would sustain itself without pressurrization). If the tanks have holes, they can't be pressurized. I could be wrong though.
Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
This is an interesting concept. This is my first post ever so don't expect this to be a great shower thought but here goes:...Im am not an engineer. But we know that the tanks are pressurized otherwise the ship would crumple because of the excess weight (and the crew cabin will add weight, to the "blank" ss that iirc would sustain itself without pressurrization). If the tanks have holes, they can't be pressurized. I could be wrong though.
Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
Depending on hole size they could hold pressure for quite some time. For example 25cm^2 (for example 5x5cm i.e. 2"x2" for those more used to imperial) hole would lose ~1m^3/s. But this is gas, so losing entire volume of gas would reduce the pressure to 37% not to 0 (because as the gas decompresses unit volume is less of the gas). The smallest tank (Methane) is ~614m^3. It would take over 11 minutes to get it from 3 bar to below sea level (getting below sea level would implode the tank by the end of bellyflop). If the initial pressure would be 6 bar, then it would take >18minutes to get it below sea level.
It his is methane tank, then this of course requires tank pressure control system to concurrently vent oxygen tank to prevent bulkhead inversion.
Welcome to the forum! I would have thought that any hole in the oxygen tank causes by melting would generate a rapid disintegration as large quantities of oxygen gas came in contact with red hot steel leading to a bigger hole...This is an interesting concept. This is my first post ever so don't expect this to be a good shower thought but here goes: Assuming they have terminal velocity in belly flop when the pinhole leak is formed, would the leak pressure PSI start higher than the perceived pressure of the windward pressure front, and essentially protect that spot from any further plasma/heat damage, until internal pressure starts to drop and atmospheric density goes up and some Delta pressure value is reached? The instant after this moment would be just as catastrophic as the list of problems Sebk mentioned....Im am not an engineer. But we know that the tanks are pressurized otherwise the ship would crumple because of the excess weight (and the crew cabin will add weight, to the "blank" ss that iirc would sustain itself without pressurrization). If the tanks have holes, they can't be pressurized. I could be wrong though.
Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
Depending on hole size they could hold pressure for quite some time. For example 25cm^2 (for example 5x5cm i.e. 2"x2" for those more used to imperial) hole would lose ~1m^3/s. But this is gas, so losing entire volume of gas would reduce the pressure to 37% not to 0 (because as the gas decompresses unit volume is less of the gas). The smallest tank (Methane) is ~614m^3. It would take over 11 minutes to get it from 3 bar to below sea level (getting below sea level would implode the tank by the end of bellyflop). If the initial pressure would be 6 bar, then it would take >18minutes to get it below sea level.
It his is methane tank, then this of course requires tank pressure control system to concurrently vent oxygen tank to prevent bulkhead inversion.
Rather than having the steel melt, it seems more feasible to have the small hole plugged by a metal that melts at a lower temperature. A thermal "fuse," essentially.
In early days of developing its recoverable spacecraft, China used ablative Cork heatshields . ( ( Thickness unknown ).Images exist showing several recovered spacecraft with these heatshields with craft intact.
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Could it be exploited ?
Rather than Chinese " copying USA/Russia" let's " copy China" !
Phill
Rather than having the steel melt, it seems more feasible to have the small hole plugged by a metal that melts at a lower temperature. A thermal "fuse," essentially.
How would you get the metal to stop melting? Are there metal pairings where the alloy has a lower melting point than either component?
Eutectoid Alloys:Rather than having the steel melt, it seems more feasible to have the small hole plugged by a metal that melts at a lower temperature. A thermal "fuse," essentially.
How would you get the metal to stop melting? Are there metal pairings where the alloy has a lower melting point than either component?
Welcome to the forum! I would have thought that any hole in the oxygen tank causes by melting would generate a rapid disintegration as large quantities of oxygen gas came in contact with red hot steel leading to a bigger hole...This is an interesting concept. This is my first post ever so don't expect this to be a good shower thought but here goes: Assuming they have terminal velocity in belly flop when the pinhole leak is formed, would the leak pressure PSI start higher than the perceived pressure of the windward pressure front, and essentially protect that spot from any further plasma/heat damage, until internal pressure starts to drop and atmospheric density goes up and some Delta pressure value is reached? The instant after this moment would be just as catastrophic as the list of problems Sebk mentioned....Im am not an engineer. But we know that the tanks are pressurized otherwise the ship would crumple because of the excess weight (and the crew cabin will add weight, to the "blank" ss that iirc would sustain itself without pressurrization). If the tanks have holes, they can't be pressurized. I could be wrong though.
Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
Depending on hole size they could hold pressure for quite some time. For example 25cm^2 (for example 5x5cm i.e. 2"x2" for those more used to imperial) hole would lose ~1m^3/s. But this is gas, so losing entire volume of gas would reduce the pressure to 37% not to 0 (because as the gas decompresses unit volume is less of the gas). The smallest tank (Methane) is ~614m^3. It would take over 11 minutes to get it from 3 bar to below sea level (getting below sea level would implode the tank by the end of bellyflop). If the initial pressure would be 6 bar, then it would take >18minutes to get it below sea level.
It his is methane tank, then this of course requires tank pressure control system to concurrently vent oxygen tank to prevent bulkhead inversion.
...the escaping oxygen gas is about 1,000 C colder than the steel and will cool it down if there's any significant flow. The only energy source is the reentry plasma, and if the escaping gas is pushing the plasma away, it will go cold.
I'm a bit concerned about releasing oxygen to cool the steel. Steel can burn. The ignition temperature of steel is maybe 1350 F, well below its melting point. If you supply oxygen, it will ignite and any hole will expand catastrophically.
The tanks are pressure stabilised for all operations other than standing still while empty, or floating in microgravity. During EDL, they must remain pressurised to flight pressure or the vehicle buckles and fails. Worse, while the tanks have nominal stringers to allow self-supporting when empty and unpressurised, in flight the tanks act as balloon tanks. Holes are contraindicated.
Rather than hoping a failed tile somehow results in merely a pinhole leak (rather than a weakened area the size of a failed tile ready to blow out once weak enough), better to avoid exposing the tank skin to reentry plasma in the first place.
The tanks are pressure stabilised for all operations other than standing still while empty, or floating in microgravity. During EDL, they must remain pressurised to flight pressure or the vehicle buckles and fails. Worse, while the tanks have nominal stringers to allow self-supporting when empty and unpressurised, in flight the tanks act as balloon tanks. Holes are contraindicated.
Rather than hoping a failed tile somehow results in merely a pinhole leak (rather than a weakened area the size of a failed tile ready to blow out once weak enough), better to avoid exposing the tank skin to reentry plasma in the first place.
I'm a bit concerned about releasing oxygen to cool the steel. Steel can burn. The ignition temperature of steel is maybe 1350 F, well below its melting point. If you supply oxygen, it will ignite and any hole will expand catastrophically.
Therein lies the beauty of using a fusible plug. You can choose a low enough melting point to avoid any issues, since you're not depending on the actual steel itself melting.
The tanks are pressure stabilised for all operations other than standing still while empty, or floating in microgravity. During EDL, they must remain pressurised to flight pressure or the vehicle buckles and fails. Worse, while the tanks have nominal stringers to allow self-supporting when empty and unpressurised, in flight the tanks act as balloon tanks. Holes are contraindicated.
Rather than hoping a failed tile somehow results in merely a pinhole leak (rather than a weakened area the size of a failed tile ready to blow out once weak enough), better to avoid exposing the tank skin to reentry plasma in the first place.
...Im am not an engineer. But we know that the tanks are pressurized otherwise the ship would crumple because of the excess weight (and the crew cabin will add weight, to the "blank" ss that iirc would sustain itself without pressurrization). If the tanks have holes, they can't be pressurized. I could be wrong though.
Perhaps the tanks could be designed to survive having some holes since the landing fuel is in the header tanks?
Depending on hole size they could hold pressure for quite some time. For example 25cm^2 (for example 5x5cm i.e. 2"x2" for those more used to imperial) hole would lose ~1m^3/s. But this is gas, so losing entire volume of gas would reduce the pressure to 37% not to 0 (because as the gas decompresses unit volume is less of the gas). The smallest tank (Methane) is ~614m^3. It would take over 11 minutes to get it from 3 bar to below sea level (getting below sea level would implode the tank by the end of bellyflop). If the initial pressure would be 6 bar, then it would take >18minutes to get it below sea level.
It his is methane tank, then this of course requires tank pressure control system to concurrently vent oxygen tank to prevent bulkhead inversion.
I'm a bit concerned about releasing oxygen to cool the steel. Steel can burn. The ignition temperature of steel is maybe 1350 F, well below its melting point. If you supply oxygen, it will ignite and any hole will expand catastrophically.
Therein lies the beauty of using a fusible plug. You can choose a low enough melting point to avoid any issues, since you're not depending on the actual steel itself melting.
That's not the point. It does not matter how the oxygen gets to the surface of the steel: melt plugs, transpiration, whatever. If that surface is above the ignition temperature of steel, it will burn in that oxygen. IMO they will just let the LOX and LCH4 cool the steel from the inside, and then find the best way to move the heat out of the liquid.
The tanks are pressure stabilised for all operations other than standing still while empty, or floating in microgravity. During EDL, they must remain pressurised to flight pressure or the vehicle buckles and fails. Worse, while the tanks have nominal stringers to allow self-supporting when empty and unpressurised, in flight the tanks act as balloon tanks. Holes are contraindicated.
Rather than hoping a failed tile somehow results in merely a pinhole leak (rather than a weakened area the size of a failed tile ready to blow out once weak enough), better to avoid exposing the tank skin to reentry plasma in the first place.
Precisely.
We seem to regularly get discussions crop up that are intellectually interesting but seem (to my eye at least) so far removed from anything that would ever be considered that I can't believe we're actually discussing them. I suppose you have to in order to avoid shutting down the creative process, but OMG they are not going to do this.
Transpiration cooling is one thing. This engineered failure-mode based cooling is off the charts.
Just like catching Super Heavy with a giant tower, right? ::)
Just like catching Super Heavy with a giant tower, right? ::)
No, not really. SpaceX has been public about aspirations to land stages on or near the launch mount for 5 years or so.
They have never mentioned Swiss cheesing the propellant tanks.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???A key point is that having arrays of small holes for your fusible-rivets wouldn’t “swiss-cheese” anything. The amount of metal removed could be very small, and the strength reduction seems negligible. Whether this scheme is, in the end, an actual good idea is of course questionable, but it is at least surprisingly plausible. My vote: Cool!
Just like catching Super Heavy with a giant tower, right? ::)
No, not really. SpaceX has been public about aspirations to land stages on or near the launch mount for 5 years or so.
You're missing the point. People still argued that 'common sense' says not to do that, just like you're arguing above.
Also, the "catching it with arms" concept isn't that old. You're conflating it with "landing on or near the launch mount," which is not the same thing.They have never mentioned Swiss cheesing the propellant tanks.
I'm not arguing that SpaceX is doing this. I'm arguing that SpaceX should do this.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
It doesn't help with the cargo, fin, or skirt sections of the hull, so it's a problem that has to be solved a different way anyway. Might as well solve it for the whole vehicle.
You're missing the point. People still argued that 'common sense' says not to do that, just like you're arguing above.
Also, the "catching it with arms" concept isn't that old. You're conflating it with "landing on or near the launch mount," which is not the same thing.They have never mentioned Swiss cheesing the propellant tanks.
I'm not arguing that SpaceX is doing this. I'm arguing that SpaceX should do this.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
The dynamic off-axis loading of the landing manoeuvre are more strenuous than the loads of launch.The tanks are pressure stabilised for all operations other than standing still while empty, or floating in microgravity. During EDL, they must remain pressurised to flight pressure or the vehicle buckles and fails. Worse, while the tanks have nominal stringers to allow self-supporting when empty and unpressurised, in flight the tanks act as balloon tanks. Holes are contraindicated.
Rather than hoping a failed tile somehow results in merely a pinhole leak (rather than a weakened area the size of a failed tile ready to blow out once weak enough), better to avoid exposing the tank skin to reentry plasma in the first place.
The internal pressure needed to keep the main tanks from buckling during the landing burn is probably quite low compared to the pressure needed to resist ascent loads and feed the Raptors.
Obviously having a hole in the tank is bad, but it's certainly less "contraindicated" than the hull actually melting due to tile loss.A hold is not like the vents in the tanks that nicely allow a controlled pressure release. Note how all the valves and vents on Starship are heavily gusseted: that's not mass added for fun, it's to avoid the tank wall ripping apart.
I'm a bit concerned about releasing oxygen to cool the steel. Steel can burn. The ignition temperature of steel is maybe 1350 F, well below its melting point. If you supply oxygen, it will ignite and any hole will expand catastrophically.
Therein lies the beauty of using a fusible plug. You can choose a low enough melting point to avoid any issues, since you're not depending on the actual steel itself melting.
That's not the point. It does not matter how the oxygen gets to the surface of the steel: melt plugs, transpiration, whatever. If that surface is above the ignition temperature of steel, it will burn in that oxygen. IMO they will just let the LOX and LCH4 cool the steel from the inside, and then find the best way to move the heat out of the liquid.
These are strong points. To keep the idea in the maybe-possibly-viable range would require candidate “rivet” materials that simultaneously meet several maybe-incompatible criteria: low(ish) melting point, compatible-enough thermal expansion coefficient, and OK w.r.t. galvanic corrosion problems. Turning the critic’s hat backward, could small holes (mm-scale) be drilled then filled with a brazing material?It doesn't help with the cargo, fin, or skirt sections of the hull, so it's a problem that has to be solved a different way anyway. Might as well solve it for the whole vehicle.
You're missing the point. People still argued that 'common sense' says not to do that, just like you're arguing above.
Also, the "catching it with arms" concept isn't that old. You're conflating it with "landing on or near the launch mount," which is not the same thing.They have never mentioned Swiss cheesing the propellant tanks.
I'm not arguing that SpaceX is doing this. I'm arguing that SpaceX should do this.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
They'd also be adding (tens of?) thousands of potential leak points to make normal vehicle use more difficult. Now you have thousands of seals that have to hold up in cryo temperatures, high (but deliberately not reentry) temps, and in space, and be reusable over many normal flights. If you use a metal alloy plug or stud that melts at the desired temperature, it won't keep up with tank stretching and contracting in different temperatures well. If you use something flexible, it's going to have a hard time with the cryo and/or high temperatures.
I think it's an interesting idea that might make the tank sections safer, but those are the potential problems I came up with.
If it were me, I'd go with the hint someone mentioned earlier in the thread about steel cookware needing an aluminum or copper coating to actually spread heat around. I can't help but wonder how thick (and heavy, and expensive) a copper coating on the inside of the tanks, skirt, and nosecone would have be to effectively spread heat to cooler parts of the ship if a few tiles were lost.To provide a useful increment in thermal conduction, the aluminum or copper layer would have to be quite thick and heavy.
It doesn't help with the cargo, fin, or skirt sections of the hull, so it's a problem that has to be solved a different way anyway. Might as well solve it for the whole vehicle.
You're missing the point. People still argued that 'common sense' says not to do that, just like you're arguing above.
Also, the "catching it with arms" concept isn't that old. You're conflating it with "landing on or near the launch mount," which is not the same thing.They have never mentioned Swiss cheesing the propellant tanks.
I'm not arguing that SpaceX is doing this. I'm arguing that SpaceX should do this.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
They'd also be adding (tens of?) thousands of potential leak points to make normal vehicle use more difficult. Now you have thousands of seals that have to hold up in cryo temperatures, high (but deliberately not reentry) temps, and in space, and be reusable over many normal flights. If you use a metal alloy plug or stud that melts at the desired temperature, it won't keep up with tank stretching and contracting in different temperatures well. If you use something flexible, it's going to have a hard time with the cryo and/or high temperatures.
I think it's an interesting idea that might make the tank sections safer, but those are the potential problems I came up with.
If it were me, I'd go with the hint someone mentioned earlier in the thread about steel cookware needing an aluminum or copper coating to actually spread heat around. I can't help but wonder how thick (and heavy, and expensive) a copper coating on the inside of the tanks, skirt, and nosecone would have be to effectively spread heat to cooler parts of the ship if a few tiles were lost.
I'm a bit concerned about releasing oxygen to cool the steel. Steel can burn. The ignition temperature of steel is maybe 1350 F, well below its melting point. If you supply oxygen, it will ignite and any hole will expand catastrophically.
Therein lies the beauty of using a fusible plug. You can choose a low enough melting point to avoid any issues, since you're not depending on the actual steel itself melting.
That's not the point. It does not matter how the oxygen gets to the surface of the steel: melt plugs, transpiration, whatever. If that surface is above the ignition temperature of steel, it will burn in that oxygen. IMO they will just let the LOX and LCH4 cool the steel from the inside, and then find the best way to move the heat out of the liquid.
How about a grid of small diameter pipes outside of the tank under the tiles, think under-floor heating. This can have fusible plugs like a fire suppression system without making a hole in the tank. It's just a bunch of added weight.
Thank you for making a technical argument against a fun creative idea, instead of just throwing rhetoric like "Rube Goldberg" around.
(Note, Rube Goldberg in the age of robotics is not a useful argument in many cases. 30 years ago placing thousands of pins accurately on a cylinder would have been Rube Goldberg, it no longer is.)
If the diameter of the hole is smaller than the thickness of the steel, maybe that does help? It feels like the expansion ratio would still be an issue, but I'm not a materials engineer. But then there's a question of how big the holes have to be in order to be effective. It did cause me to start imagining the Raptors ingesting bits of formally molten plug material, which could cause issues upon landing if they did need to melt due to a lost tile.These are strong points. To keep the idea in the maybe-possibly-viable range would require candidate “rivet” materials that simultaneously meet several maybe-incompatible criteria: low(ish) melting point, compatible-enough thermal expansion coefficient, and OK w.r.t. galvanic corrosion problems. Turning the critic’s hat backward, could small holes (mm-scale) be drilled then filled with a brazing material?It doesn't help with the cargo, fin, or skirt sections of the hull, so it's a problem that has to be solved a different way anyway. Might as well solve it for the whole vehicle.
You're missing the point. People still argued that 'common sense' says not to do that, just like you're arguing above.
Also, the "catching it with arms" concept isn't that old. You're conflating it with "landing on or near the launch mount," which is not the same thing.They have never mentioned Swiss cheesing the propellant tanks.
I'm not arguing that SpaceX is doing this. I'm arguing that SpaceX should do this.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
They'd also be adding (tens of?) thousands of potential leak points to make normal vehicle use more difficult. Now you have thousands of seals that have to hold up in cryo temperatures, high (but deliberately not reentry) temps, and in space, and be reusable over many normal flights. If you use a metal alloy plug or stud that melts at the desired temperature, it won't keep up with tank stretching and contracting in different temperatures well. If you use something flexible, it's going to have a hard time with the cryo and/or high temperatures.
I think it's an interesting idea that might make the tank sections safer, but those are the potential problems I came up with.
That's too bad, but kinda what I figured. Might be interesting to run the numbers at some point if I ever had some spare time.If it were me, I'd go with the hint someone mentioned earlier in the thread about steel cookware needing an aluminum or copper coating to actually spread heat around. I can't help but wonder how thick (and heavy, and expensive) a copper coating on the inside of the tanks, skirt, and nosecone would have be to effectively spread heat to cooler parts of the ship if a few tiles were lost.To provide a useful increment in thermal conduction, the aluminum or copper layer would have to be quite thick and heavy.
It's taking a fairly straightforward concern and responding in a ridiculously complicated manner introducing all kinds of complexity and altering the integrity of the tank over its entire lifetime for that edge case that may never happen, may not be an issue if it does, and could be addressed in far simpler ways.I tend to agree with you that risking the integrity of the entire tank is doubtful. And yet..... something is going on with transpirational cooling. So there must be hot spots that require some non-conventional solution. And Elon's mention of ITAR suggests that this solution is sophisticated and non-obvious to the point of being a national security issue. So the fusible plug idea, perhaps coupled with an upstream valve, might offer failsafe protection against disaster. It might be done only with methane and it might be intermittent. Something is going on beyond tiles so I don't want to assume that even crazy ideas are impossible. :)
If it were me, I'd go with the hint someone mentioned earlier in the thread about steel cookware needing an aluminum or copper coating to actually spread heat around. I can't help but wonder how thick (and heavy, and expensive) a copper coating on the inside of the tanks, skirt, and nosecone would have be to effectively spread heat to cooler parts of the ship if a few tiles were lost.Quality stainless steel cookware does not have a "copper coating". Cheap cookware has a coating to make it look like older expensive copper-bottomed cookware. Quality stainless steel cookware has an embedded fairly thick copper plate. For the tank skins, the LOX and LCH4 will move heat far more efficiently by convection than any conceivable solid heat spreader. For the rest of the under-TPS hull, you need convection of some sort, possibly heat pipes.
From COMBUSTION OF METALS IN OXYGEN PHASE II: BULK BURNING EXPERIMENTS (https://nvlpubs.nist.gov/nistpubs/Legacy/IR/nbsir73-345.pdf), NBSIR 73-345:So, combustion conditions = melting point & high oxygen pressure, not merely hot at lower pressure.
“…we found that 304L stainless steel, if brought to its melting point and allowed to spread out in a layer not more than 1 /4 inch thick on a poorly conducting surface, would burn to completion if the oxygen pressure was over 50 psig.” (emphasis in the original text, pg 2)
“In no case did we seem to get ignition before melting....Sustained burning [of already-molten 304L] will not occur generally below 50 psig of oxygen.” (pg 19)
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
You are missing the point. Wild ideas lie on a spectrum. It's not a binary where "Oh, some other idea argued as 'not common sense' was adopted so anyone that argues 'not common sense' is, by default, automatically on shaky ground.
Catching on arms and catching on mount are closely related enough that they might as well be the same concept on the wild ideas spectrum. There's not much qualitatively different about them as relates to the trades.
Of course it could probably be made to work, but LOV/LOC vs. Few Rivets is a false dichotomy.
The question is whether pursuing an incrementally better TPS is far more sensible than chasing an enormously complicated pipe dream for a case that should never be allowed to happen anyway.
These are strong points. To keep the idea in the maybe-possibly-viable range would require candidate “rivet” materials that simultaneously meet several maybe-incompatible criteria: low(ish) melting point, compatible-enough thermal expansion coefficient, and OK w.r.t. galvanic corrosion problems.
Naturally the chosen alloy would need to be compatible with 304 stainless in terms of galvanic corrosion, CTE, etc.
Turning the critic’s hat backward, could small holes (mm-scale) be drilled then filled with a brazing material?
Thank you for making a technical argument against a fun creative idea, instead of just throwing rhetoric like "Rube Goldberg" around.
(Note, Rube Goldberg in the age of robotics is not a useful argument in many cases. 30 years ago placing thousands of pins accurately on a cylinder would have been Rube Goldberg, it no longer is.)
And yet it's perfectly apropos here precisely because it's not 30 years from now. If in 30 years it's no longer a Rube Goldberg idea, then it won't be labelled such just as Robotic Pinning isn't labelled that now.
I just fail to see how anyone with a modicum of engineering background thinks that intentionally designing a pressure vessel to be perforated for an edge case is reasonable and something that the astronauts will find to be a fun creative idea. It's taking a fairly straightforward concern and responding in a ridiculously complicated manner introducing all kinds of complexity and altering the integrity of the tank over its entire lifetime for that edge case that may never happen, may not be an issue if it does, and could be addressed in far simpler ways. That's RGB. Rube Goldberg Baby.
Similarly with this concept and "transpiration cooling."
The advantage of this over transpiration cooling is that it eliminates all the plumbing.
"To design a spacecraft right takes an infinite amount of effort. This is why it's a good idea to design them to operate when some things are wrong." -- Akin's Second Law of Spacecraft Design (https://spacecraft.ssl.umd.edu/akins_laws.html)
I think this is one of those "obvious in hindsight" issues where the safety backup will only be added in the wake of a very public failure. That's part of the SpaceX iterative design philosophy -- don't add it until you know you need it.
It will be very interesting to see the results of the first Starship reentry test.
AFAICT this "belt and suspenders" approach combines the best of both worlds: tiles as the fully-reusable primary heat shield, with a super-lightweight and ultra-simplified contingency transpiration system covering the primary failure mode of the tiles.
1) Similar is a meaningless word. Perforation cooling and Transpiration Cooling are similar in that the concepts do similar things (namely: "cool" ... duh) but are completely different in that they cannot address the same scenarios. Quit trying to play semantic games.This is getting strange. Exactly what do you think transpiration is anyway? It means the movement of water from the stomata of a leaf. In the most general sense, it is the movement of a fluid (or gas) through a perforation. There is the related concept of the evaporation of the fluid causing a "transpiration pressure" which pulls more fluid behind it. Do you think anyone has offered a definition of transpiration cooling that differentiates it from the movement of fluid under pressure through a small perforation? These ideas are not only similar but as used so far seem to be identical.
Similarly with this concept and "transpiration cooling."
The advantage of this over transpiration cooling is that it eliminates all the plumbing.
"To design a spacecraft right takes an infinite amount of effort. This is why it's a good idea to design them to operate when some things are wrong." -- Akin's Second Law of Spacecraft Design (https://spacecraft.ssl.umd.edu/akins_laws.html)
Not similar at all. Mount Catching and Arm catching are alternatives ... you don't need both. Planned-Perforation can't address all Primary and Backup Cooling needs.I think this is one of those "obvious in hindsight" issues where the safety backup will only be added in the wake of a very public failure. That's part of the SpaceX iterative design philosophy -- don't add it until you know you need it.
It will be very interesting to see the results of the first Starship reentry test.
AFAICT this "belt and suspenders" approach combines the best of both worlds: tiles as the fully-reusable primary heat shield, with a super-lightweight and ultra-simplified contingency transpiration system covering the primary failure mode of the tiles.
Perhaps. I agree the safety backup needs to be addressed early before any high-profile failure. I don't think Planned-Perforation is very good for anything other than a last line of defense and it's too complex to be worth investing in as a last line of defense given that you'd still need other lines. Better to beef up the other elements of the system.
This is one of those things that's speciously compelling, becoming a hobby-horse once it gets it worms it past your initial incredulity. Be stronger.
I preferred when the heat shield currently being put on Starship 20 was discussed.
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Why cooling “only with methane”?The tanks are are well above 50 PSIG (64 PSIA, or 4.4 Bar, vs. 6 Bar tank pressure). In addition, putting a thin sheet with molten edges in a hypersonic gas flow is going to mean you;re dealing with combustion of a spray of aerosolised molten metal, not a contiguous lump.
Is there any evidence that combustion is a risk for stainless?
Experimental evidence says otherwise:QuoteFrom COMBUSTION OF METALS IN OXYGEN PHASE II: BULK BURNING EXPERIMENTS (https://nvlpubs.nist.gov/nistpubs/Legacy/IR/nbsir73-345.pdf), NBSIR 73-345:So, combustion conditions = melting point & high oxygen pressure, not merely hot at lower pressure.
“…we found that 304L stainless steel, if brought to its melting point and allowed to spread out in a layer not more than 1 /4 inch thick on a poorly conducting surface, would burn to completion if the oxygen pressure was over 50 psig.” (emphasis in the original text, pg 2)
“In no case did we seem to get ignition before melting....Sustained burning [of already-molten 304L] will not occur generally below 50 psig of oxygen.” (pg 19)
I think we’ve seen some exaggeration of the combustibility of stainless steel in several discussions in this forum.
Maybe people are confusing 304L (Starship Stainless®) with other steel alloys (or with aluminum or something)?
Net assessment so far: Small fusible plugs in tank walls might possibly be good for something, somewhere, sometime -- or not.
The data seems to say that combusion requires melting, and if the structure is melting, then you’ve already lost the ship. Combustion might be a consequence of failure, but not a cause.Why cooling “only with methane”?The tanks are are well above 50 PSIG (64 PSIA, or 4.4 Bar, vs. 6 Bar tank pressure). In addition, putting a thin sheet with molten edges in a hypersonic gas flow is going to mean you;re dealing with combustion of a spray of aerosolised molten metal, not a contiguous lump.
Is there any evidence that combustion is a risk for stainless?
Experimental evidence says otherwise:QuoteFrom COMBUSTION OF METALS IN OXYGEN PHASE II: BULK BURNING EXPERIMENTS (https://nvlpubs.nist.gov/nistpubs/Legacy/IR/nbsir73-345.pdf), NBSIR 73-345:So, combustion conditions = melting point & high oxygen pressure, not merely hot at lower pressure.
“…we found that 304L stainless steel, if brought to its melting point and allowed to spread out in a layer not more than 1 /4 inch thick on a poorly conducting surface, would burn to completion if the oxygen pressure was over 50 psig.” (emphasis in the original text, pg 2)
“In no case did we seem to get ignition before melting....Sustained burning [of already-molten 304L] will not occur generally below 50 psig of oxygen.” (pg 19)
I think we’ve seen some exaggeration of the combustibility of stainless steel in several discussions in this forum.
Maybe people are confusing 304L (Starship Stainless®) with other steel alloys (or with aluminum or something)?
Net assessment so far: Small fusible plugs in tank walls might possibly be good for something, somewhere, sometime -- or not.
Hot stainless will burn in the conditions inside the tank. The optimum option remain to not allow presence of hot stainless in the first place.
Any molten spray won't be in the tank, though. The stagnation pressure of the incoming plasma is only a fraction of a psi, so any flow through a hypothetical hole is going to go out of the tank, not into it. Outside it could vaporize, ionize, burn, or something, but who cares?Why cooling “only with methane”?The tanks are are well above 50 PSIG (64 PSIA, or 4.4 Bar, vs. 6 Bar tank pressure). In addition, putting a thin sheet with molten edges in a hypersonic gas flow is going to mean you;re dealing with combustion of a spray of aerosolised molten metal, not a contiguous lump.
Is there any evidence that combustion is a risk for stainless?
Experimental evidence says otherwise:QuoteFrom COMBUSTION OF METALS IN OXYGEN PHASE II: BULK BURNING EXPERIMENTS (https://nvlpubs.nist.gov/nistpubs/Legacy/IR/nbsir73-345.pdf), NBSIR 73-345:So, combustion conditions = melting point & high oxygen pressure, not merely hot at lower pressure.
“…we found that 304L stainless steel, if brought to its melting point and allowed to spread out in a layer not more than 1 /4 inch thick on a poorly conducting surface, would burn to completion if the oxygen pressure was over 50 psig.” (emphasis in the original text, pg 2)
“In no case did we seem to get ignition before melting....Sustained burning [of already-molten 304L] will not occur generally below 50 psig of oxygen.” (pg 19)
I think we’ve seen some exaggeration of the combustibility of stainless steel in several discussions in this forum.
Maybe people are confusing 304L (Starship Stainless®) with other steel alloys (or with aluminum or something)?
Net assessment so far: Small fusible plugs in tank walls might possibly be good for something, somewhere, sometime -- or not.
Hot stainless will burn in the conditions inside the tank. The optimum option remain to not allow presence of hot stainless in the first place.
OkWhich pictures have you been looking at? From Mary: (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2295258#msg2295258)
Instead of fusible plugs discussion (well mostly).
I asked before if the tiles blown off of S20 by the header tank vents had pins.
Every picture I have found of the tileless area has not shown any pins.
Anybody have evidence to the contrary? And yes this relates to the need of fusible plugs...
Also on fusible plugs, I think single tile loss would probably be survivable. Just a guess from comments about reduced stress during reentry and lower ullage pressure and a single tile being a small enough spot to stay cooler. So best part is no part.
What exactly do you think I'm saying? It seems clear enough to me.1) Similar is a meaningless word. Perforation cooling and Transpiration Cooling are similar in that the concepts do similar things (namely: "cool" ... duh) but are completely different in that they cannot address the same scenarios. Quit trying to play semantic games.This is getting strange. Exactly what do you think transpiration is anyway? It means the movement of water from the stomata of a leaf. In the most general sense, it is the movement of a fluid (or gas) through a perforation. There is the related concept of the evaporation of the fluid causing a "transpiration pressure" which pulls more fluid behind it. Do you think anyone has offered a definition of transpiration cooling that differentiates it from the movement of fluid under pressure through a small perforation? These ideas are not only similar but as used so far seem to be identical.
Ok, so what engineering system has been defined for transpiration cooling? Elon refuses to be specific, offering ITAR as a reason. How do we know that Elon's plan for transpiration cooling does not involve "perforation cooling" or fusable plugs? That's why I say that, so far, they appear to be identical. Until such time as SpaceX actually explains its plans, we don't know. Yes, fusable plugs seems like a far out idea, but so does any form of cooling that involves loss of propellant. And yet, Elon says that is still on the table.What exactly do you think I'm saying? It seems clear enough to me.1) Similar is a meaningless word. Perforation cooling and Transpiration Cooling are similar in that the concepts do similar things (namely: "cool" ... duh) but are completely different in that they cannot address the same scenarios. Quit trying to play semantic games.This is getting strange. Exactly what do you think transpiration is anyway? It means the movement of water from the stomata of a leaf. In the most general sense, it is the movement of a fluid (or gas) through a perforation. There is the related concept of the evaporation of the fluid causing a "transpiration pressure" which pulls more fluid behind it. Do you think anyone has offered a definition of transpiration cooling that differentiates it from the movement of fluid under pressure through a small perforation? These ideas are not only similar but as used so far seem to be identical.
There is the physical process and the engineering system that implements the physical process. The terms Perforation Cooling or Transpiration Cooling can refer to either. The physical processes are similar enough but the engineering systems and what can be accomplished with them are miles apart. Because the physical process cannot exist without the engineering system, it's mendacious to suggest they are identical.
OkWhich pictures have you been looking at? From Mary: (https://forum.nasaspaceflight.com/index.php?topic=52398.msg2295258#msg2295258)
Instead of fusible plugs discussion (well mostly).
I asked before if the tiles blown off of S20 by the header tank vents had pins.
Every picture I have found of the tileless area has not shown any pins.
Anybody have evidence to the contrary? And yes this relates to the need of fusible plugs...
Also on fusible plugs, I think single tile loss would probably be survivable. Just a guess from comments about reduced stress during reentry and lower ullage pressure and a single tile being a small enough spot to stay cooler. So best part is no part.
SpaceX hasn't shared a transpiration design but the topic has been well covered on this forum and it's reasonable to assume a system like those. We don't know but I would lay good odds that Elon isn't going to use fusible plugs because they seem to me completely inconsistent with everything we know about his approach. I can't imagine what such a system would do to the manufacturing, validation, and inspection processes. Just doesn't seem what is aimed for.What exactly do you think I'm saying? It seems clear enough to me.Ok, so what engineering system has been defined for transpiration cooling? Elon refuses to be specific, offering ITAR as a reason. How do we know that Elon's plan for transpiration cooling does not involve "perforation cooling" or fusable plugs? That's why I say that, so far, they appear to be identical. Until such time as SpaceX actually explains its plans, we don't know. Yes, fusable plugs seems like a far out idea, but so does any form of cooling that involves loss of propellant. And yet, Elon says that is still on the table.
There is the physical process and the engineering system that implements the physical process. The terms Perforation Cooling or Transpiration Cooling can refer to either. The physical processes are similar enough but the engineering systems and what can be accomplished with them are miles apart. Because the physical process cannot exist without the engineering system, it's mendacious to suggest they are identical.
Not so thick and heavy if it's on the outside of the skin. That would start spreading the heat before it even gets to the stainless. This avoids a problem. Put it on the inside and it conducts heat away from an already hot skin. This mitigates an existing problem.These are strong points. To keep the idea in the maybe-possibly-viable range would require candidate “rivet” materials that simultaneously meet several maybe-incompatible criteria: low(ish) melting point, compatible-enough thermal expansion coefficient, and OK w.r.t. galvanic corrosion problems. Turning the critic’s hat backward, could small holes (mm-scale) be drilled then filled with a brazing material?It doesn't help with the cargo, fin, or skirt sections of the hull, so it's a problem that has to be solved a different way anyway. Might as well solve it for the whole vehicle.
You're missing the point. People still argued that 'common sense' says not to do that, just like you're arguing above.
Also, the "catching it with arms" concept isn't that old. You're conflating it with "landing on or near the launch mount," which is not the same thing.They have never mentioned Swiss cheesing the propellant tanks.
I'm not arguing that SpaceX is doing this. I'm arguing that SpaceX should do this.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
They'd also be adding (tens of?) thousands of potential leak points to make normal vehicle use more difficult. Now you have thousands of seals that have to hold up in cryo temperatures, high (but deliberately not reentry) temps, and in space, and be reusable over many normal flights. If you use a metal alloy plug or stud that melts at the desired temperature, it won't keep up with tank stretching and contracting in different temperatures well. If you use something flexible, it's going to have a hard time with the cryo and/or high temperatures.
I think it's an interesting idea that might make the tank sections safer, but those are the potential problems I came up with.If it were me, I'd go with the hint someone mentioned earlier in the thread about steel cookware needing an aluminum or copper coating to actually spread heat around. I can't help but wonder how thick (and heavy, and expensive) a copper coating on the inside of the tanks, skirt, and nosecone would have be to effectively spread heat to cooler parts of the ship if a few tiles were lost.To provide a useful increment in thermal conduction, the aluminum or copper layer would have to be quite thick and heavy.
Also, I'm dubious that stainless 304 will melt at all in these conditions. At the melting point of stainless 304, the radiative flux into the cold tank sink (~275 kW/m2) would be about triple the flux coming in from the plasma stream along the vehicle centerline (~100 kW/m2 based on Shuttle data). If flux out is more than flux in, then it is above equilibrium temperature, i.e. unreachable in this scenario. The equilibrium temperature is about 1000 to 1100 C, which is quite far below the melting point of stainless 304. And that's before accounting for the isolator pad insulation, which will add thermal resistance and reduce flux.
I think the overwhelmingly most likely outcome of losing a tile, or a few tiles, is that the steel heats to around 700-900 C, above the annealing temperature, but does not burst, leak, or melt in any significant fashion. It certainly doesn't burn. The vehicle lands, and then is repaired by reinforcing or replacing that patch of steel and replacing the tile, or is scrapped.
Not so thick and heavy if it's on the outside of the skin. That would start spreading the heat before it even gets to the stainless. This avoids a problem. Put it on the inside and it conducts heat away from an already hot skin. This mitigates an existing problem.These are strong points. To keep the idea in the maybe-possibly-viable range would require candidate “rivet” materials that simultaneously meet several maybe-incompatible criteria: low(ish) melting point, compatible-enough thermal expansion coefficient, and OK w.r.t. galvanic corrosion problems. Turning the critic’s hat backward, could small holes (mm-scale) be drilled then filled with a brazing material?It doesn't help with the cargo, fin, or skirt sections of the hull, so it's a problem that has to be solved a different way anyway. Might as well solve it for the whole vehicle.
You're missing the point. People still argued that 'common sense' says not to do that, just like you're arguing above.
Also, the "catching it with arms" concept isn't that old. You're conflating it with "landing on or near the launch mount," which is not the same thing.They have never mentioned Swiss cheesing the propellant tanks.
I'm not arguing that SpaceX is doing this. I'm arguing that SpaceX should do this.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
They'd also be adding (tens of?) thousands of potential leak points to make normal vehicle use more difficult. Now you have thousands of seals that have to hold up in cryo temperatures, high (but deliberately not reentry) temps, and in space, and be reusable over many normal flights. If you use a metal alloy plug or stud that melts at the desired temperature, it won't keep up with tank stretching and contracting in different temperatures well. If you use something flexible, it's going to have a hard time with the cryo and/or high temperatures.
I think it's an interesting idea that might make the tank sections safer, but those are the potential problems I came up with.If it were me, I'd go with the hint someone mentioned earlier in the thread about steel cookware needing an aluminum or copper coating to actually spread heat around. I can't help but wonder how thick (and heavy, and expensive) a copper coating on the inside of the tanks, skirt, and nosecone would have be to effectively spread heat to cooler parts of the ship if a few tiles were lost.To provide a useful increment in thermal conduction, the aluminum or copper layer would have to be quite thick and heavy.
Cookware uses a thick plate to deliver even heating over a large area. For SS the area and evenness if heating is irrelevant. Reducing max temp is the goal.
Also, I'm dubious that stainless 304 will melt at all in these conditions. At the melting point of stainless 304, the radiative flux into the cold tank sink (~275 kW/m2) would be about triple the flux coming in from the plasma stream along the vehicle centerline (~100 kW/m2 based on Shuttle data). If flux out is more than flux in, then it is above equilibrium temperature, i.e. unreachable in this scenario. The equilibrium temperature is about 1000 to 1100 C, which is quite far below the melting point of stainless 304. And that's before accounting for the isolator pad insulation, which will add thermal resistance and reduce flux.
I think the overwhelmingly most likely outcome of losing a tile, or a few tiles, is that the steel heats to around 700-900 C, above the annealing temperature, but does not burst, leak, or melt in any significant fashion. It certainly doesn't burn. The vehicle lands, and then is repaired by reinforcing or replacing that patch of steel and replacing the tile, or is scrapped.
Well, that's comforting.
So maybe nothing special is needed at all?
The nominal case (of course) is that the tiles protect the structure. But the fallback can be that the steel (+ insulation) handles it well enough to land safely, though not well enough to handle another launch (loses strength due to above annealing temperature)?
Am I understanding that correctly?
Thin sheets, thick plates. No numbers. Conceptual. As thick as necessary, no more. More than electroplating and (WAG) less than 1mm.Not so thick and heavy if it's on the outside of the skin. That would start spreading the heat before it even gets to the stainless. This avoids a problem. Put it on the inside and it conducts heat away from an already hot skin. This mitigates an existing problem.These are strong points. To keep the idea in the maybe-possibly-viable range would require candidate “rivet” materials that simultaneously meet several maybe-incompatible criteria: low(ish) melting point, compatible-enough thermal expansion coefficient, and OK w.r.t. galvanic corrosion problems. Turning the critic’s hat backward, could small holes (mm-scale) be drilled then filled with a brazing material?It doesn't help with the cargo, fin, or skirt sections of the hull, so it's a problem that has to be solved a different way anyway. Might as well solve it for the whole vehicle.
You're missing the point. People still argued that 'common sense' says not to do that, just like you're arguing above.
Also, the "catching it with arms" concept isn't that old. You're conflating it with "landing on or near the launch mount," which is not the same thing.They have never mentioned Swiss cheesing the propellant tanks.
I'm not arguing that SpaceX is doing this. I'm arguing that SpaceX should do this.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
They'd also be adding (tens of?) thousands of potential leak points to make normal vehicle use more difficult. Now you have thousands of seals that have to hold up in cryo temperatures, high (but deliberately not reentry) temps, and in space, and be reusable over many normal flights. If you use a metal alloy plug or stud that melts at the desired temperature, it won't keep up with tank stretching and contracting in different temperatures well. If you use something flexible, it's going to have a hard time with the cryo and/or high temperatures.
I think it's an interesting idea that might make the tank sections safer, but those are the potential problems I came up with.If it were me, I'd go with the hint someone mentioned earlier in the thread about steel cookware needing an aluminum or copper coating to actually spread heat around. I can't help but wonder how thick (and heavy, and expensive) a copper coating on the inside of the tanks, skirt, and nosecone would have be to effectively spread heat to cooler parts of the ship if a few tiles were lost.To provide a useful increment in thermal conduction, the aluminum or copper layer would have to be quite thick and heavy.
Cookware uses a thick plate to deliver even heating over a large area. For SS the area and evenness if heating is irrelevant. Reducing max temp is the goal.
To reduce max temp with a conductor the heat has to go somewhere to be rejected. Where is it going, how is it being rejected, and how much does a thin layer help it get there? Thin sheets are lousy for lateral heat transport.
Has anybody come up with an idea of what the mesh is made of? I swear it drapes like plastic. That makes no sense.It almost looks like Nomex Aramid...
Thin sheets, thick plates. No numbers. Conceptual. As thick as necessary, no more. More than electroplating and (WAG) less than 1mm.Not so thick and heavy if it's on the outside of the skin. That would start spreading the heat before it even gets to the stainless. This avoids a problem. Put it on the inside and it conducts heat away from an already hot skin. This mitigates an existing problem.These are strong points. To keep the idea in the maybe-possibly-viable range would require candidate “rivet” materials that simultaneously meet several maybe-incompatible criteria: low(ish) melting point, compatible-enough thermal expansion coefficient, and OK w.r.t. galvanic corrosion problems. Turning the critic’s hat backward, could small holes (mm-scale) be drilled then filled with a brazing material?It doesn't help with the cargo, fin, or skirt sections of the hull, so it's a problem that has to be solved a different way anyway. Might as well solve it for the whole vehicle.
You're missing the point. People still argued that 'common sense' says not to do that, just like you're arguing above.
Also, the "catching it with arms" concept isn't that old. You're conflating it with "landing on or near the launch mount," which is not the same thing.They have never mentioned Swiss cheesing the propellant tanks.
I'm not arguing that SpaceX is doing this. I'm arguing that SpaceX should do this.
What I'm failing to see are any actual technical arguments as to why this concept wouldn't work. Specifically, how is complete hull failure leading to LOV / LOC preferable to replacing a few rivets before re-tiling? ???
They'd also be adding (tens of?) thousands of potential leak points to make normal vehicle use more difficult. Now you have thousands of seals that have to hold up in cryo temperatures, high (but deliberately not reentry) temps, and in space, and be reusable over many normal flights. If you use a metal alloy plug or stud that melts at the desired temperature, it won't keep up with tank stretching and contracting in different temperatures well. If you use something flexible, it's going to have a hard time with the cryo and/or high temperatures.
I think it's an interesting idea that might make the tank sections safer, but those are the potential problems I came up with.If it were me, I'd go with the hint someone mentioned earlier in the thread about steel cookware needing an aluminum or copper coating to actually spread heat around. I can't help but wonder how thick (and heavy, and expensive) a copper coating on the inside of the tanks, skirt, and nosecone would have be to effectively spread heat to cooler parts of the ship if a few tiles were lost.To provide a useful increment in thermal conduction, the aluminum or copper layer would have to be quite thick and heavy.
Cookware uses a thick plate to deliver even heating over a large area. For SS the area and evenness if heating is irrelevant. Reducing max temp is the goal.
To reduce max temp with a conductor the heat has to go somewhere to be rejected. Where is it going, how is it being rejected, and how much does a thin layer help it get there? Thin sheets are lousy for lateral heat transport.
Lateral conductivity for a high temp gradient, AFAIK, works better than a low temp gradient. What we're talking about is a hot spot which implies a high gradient. If the entire layer becomes the sink for a missing tile who cares. While the 'heat front' is spreading laterally it will do some admittedly crappy conduction to the cooler stainless.
Does anybody have a decent guess for the Mars altitude that will be considered "entry interface?" Similarly, what speed do you think Starship will be able to handle at that interface?
I have pretty much the same questions for Earth.
I've been fooling with some delta-v and prop budgeting for martian Starship missions. I've been assuming that Mars entry interface is about 70km altitude, and that max speed is about 12km/s. That yields an arrival v∞ of 10.92km/s.
Do those sound in the right ballpark? Anybody have better numbers?
One unique dynamic about Martian reentry is the presence of dust particles pretty high up in the atmosphere, which may create problems for reusing heatshield.I think we can make a pretty good estimate of the problem (or non-problem) based on two facts:
Does anybody have a decent guess for the Mars altitude that will be considered "entry interface?" Similarly, what speed do you think Starship will be able to handle at that interface?Something that might feed into the problem is that martian and earth atmospheric density are roughly the same from ~120km to ~85km. This is from a NASA paper that I can't put my finger on.
I have pretty much the same questions for Earth.
I've been fooling with some delta-v and prop budgeting for martian Starship missions. I've been assuming that Mars entry interface is about 70km altitude, and that max speed is about 12km/s. That yields an arrival v∞ of 10.92km/s.
Do those sound in the right ballpark? Anybody have better numbers?
Does anybody have a decent guess for the Mars altitude that will be considered "entry interface?" Similarly, what speed do you think Starship will be able to handle at that interface?Something that might feed into the problem is that martian and earth atmospheric density are roughly the same from ~120km to ~85km. This is from a NASA paper that I can't put my finger on.
I have pretty much the same questions for Earth.
I've been fooling with some delta-v and prop budgeting for martian Starship missions. I've been assuming that Mars entry interface is about 70km altitude, and that max speed is about 12km/s. That yields an arrival v∞ of 10.92km/s.
Do those sound in the right ballpark? Anybody have better numbers?
Here's something I came across while looking for it. More than I can adsorb quickly. It covers reentry issues. Looks like your type of meat.
https://ntrs.nasa.gov/api/citations/20110003632/downloads/20110003632.pdf (https://ntrs.nasa.gov/api/citations/20110003632/downloads/20110003632.pdf)
"Entry, Descent, and Landing (EDL) begins when the spacecraft reaches the top of the Martian atmosphere, about 80 miles (about 128 kilometers) above the surface, and ends with the lander safe and sound on the surface of Mars six minutes later."
"The entry, descent, and landing (EDL) phase began when the spacecraft reached the Martian atmosphere, about 125 kilometers (about 78 miles) above the surface..."
Does anybody have a decent guess for the Mars altitude that will be considered "entry interface?" Similarly, what speed do you think Starship will be able to handle at that interface?
I have pretty much the same questions for Earth.
I've been fooling with some delta-v and prop budgeting for martian Starship missions. I've been assuming that Mars entry interface is about 70km altitude, and that max speed is about 12km/s. That yields an arrival v∞ of 10.92km/s.
Do those sound in the right ballpark? Anybody have better numbers?
Here's some reentry data from historical Mars landing missions, courtesy of NASA:
(https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Mars-Science-Laboratory-Mars-Entry-Trajectory.png/1280px-Mars-Science-Laboratory-Mars-Entry-Trajectory.png)
See also here, on "Mars Pathfinder Atmospheric Entry Strategy" : https://nssdc.gsfc.nasa.gov/planetary/marsentry.html
Peak heating for Pathfinder entry at about 40km altitude, at speed roughly 6km/s.
One unique dynamic about Martian reentry is the presence of dust particles pretty high up in the atmosphere, which may create problems for reusing heatshield.
Does anybody have a decent guess for the Mars altitude that will be considered "entry interface?" Similarly, what speed do you think Starship will be able to handle at that interface?
I have pretty much the same questions for Earth.
I've been fooling with some delta-v and prop budgeting for martian Starship missions. I've been assuming that Mars entry interface is about 70km altitude, and that max speed is about 12km/s. That yields an arrival v∞ of 10.92km/s.
Do those sound in the right ballpark? Anybody have better numbers?
Here's some reentry data from historical Mars landing missions, courtesy of NASA:
(https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Mars-Science-Laboratory-Mars-Entry-Trajectory.png/1280px-Mars-Science-Laboratory-Mars-Entry-Trajectory.png)
See also here, on "Mars Pathfinder Atmospheric Entry Strategy" : https://nssdc.gsfc.nasa.gov/planetary/marsentry.html
Peak heating for Pathfinder entry at about 40km altitude, at speed roughly 6km/s.
One unique dynamic about Martian reentry is the presence of dust particles pretty high up in the atmosphere, which may create problems for reusing heatshield.
Your chart shows considerably lower speeds than Apollo-era entry interface speeds, which were about 11km/s. Is that because of some inherent property of the Mars atmosphere and scale height, or is it a function of the kinds of blunt-body L/D that your garden-variety martian probe can muster? If so, is it possible that Starship's entry speed could be considerably higher?
At some point, I'd heard somebody suggesting that Starship would do Mars entry with negative lift, so that it could have a flight path angle that would otherwise cause it to skip out of the atmosphere but still stayed at a very high altitude for a long time. However, I'm unclear on how such a trajectory would eventually wind up with the nose point forward and the Starship rightside-up.
If the charted numbers (125km entry interface @ 7500m/s) are close to the maximum, that implies an arrival v∞ = 5650m/s. Here are some windows for both minimum energy and minimum time-of-flight, given that restriction.
Reentry speed is primarily determined by orbital mechanics. Mars has much less mass than Earth, so the velocity of a spacecraft at 100km circular orbit around Mars would be roughly 3.5km/s only. Pathfinder's reentry speed is actually higher than Mars escape velocity, as it uses the Martian atmosphere to aerobreak into landing trajectory. Note while Mars reentry begins at around 130km altitude, the spacecraft would continue to accelerate until about 80km in Pathfinder's case, that's when aerodynamic forces finally displaces orbital mechanic.
At some point, I'd heard somebody suggesting that Starship would do Mars entry with negative lift, so that it could have a flight path angle that would otherwise cause it to skip out of the atmosphere but still stayed at a very high altitude for a long time. However, I'm unclear on how such a trajectory would eventually wind up with the nose point forward and the Starship rightside-up.Extensive modelling of such a trajectory here (skip to 30:54 if you don't want to watch the whole thing.): https://youtu.be/ZoSKHzziLKw?t=1854
Reentry speed is primarily determined by orbital mechanics. Mars has much less mass than Earth, so the velocity of a spacecraft at 100km circular orbit around Mars would be roughly 3.5km/s only. Pathfinder's reentry speed is actually higher than Mars escape velocity, as it uses the Martian atmosphere to aerobreak into landing trajectory. Note while Mars reentry begins at around 130km altitude, the spacecraft would continue to accelerate until about 80km in Pathfinder's case, that's when aerodynamic forces finally displaces orbital mechanic.
But my question still stands: Is Pathfinder a good proxy for a vehicle that will probably have a shallower flight-path angle and a radically different TPS?
This was for the old 'Red Dragon' mission concept, but the principle for a cylindrical rather than conical lifting body is the same: roll 'upside down' when negative lift is required, and roll back upright afterwards.
The coordinate systems are different. Both maneuvers are rotating the lift vector around the velocity vector at constant AoA. For Starship it is simply a combined retraction/deployment of the fins in diagonal pairs (i.e. right forward/left aft in, left forward/right aft out to rotate to the nose to the right and vice versa). Starship has the added benefit of also being able to quickly do small corrections in total drag/lift and AoA which is a good thing since it will at best be barely passively stable for part of the flight envelope.This was for the old 'Red Dragon' mission concept, but the principle for a cylindrical rather than conical lifting body is the same: roll 'upside down' when negative lift is required, and roll back upright afterwards.
That seems doable for a Dragon, which has a fairly low angle of attack and fairly stubby moments of inertia in the roll and pitch directions. As a result, it can roll pretty fast, and the stagnation point isn't going to move off of the TPS while you're rolling.
But how can you roll a Starship, which has high angle of attack, hefty pitch moments, and not the most responsive aerocontrols? And if you can roll it, how do you roll it in such a manner that you keep your free stream stagnation point on the TPS, rather than having it walk around to the unprotected dorsal side of the vehicle?
ISTM that the maneuver that a Starship would need is a combination roll/yaw maneuver, so that the angle of attack stays the same while the lift vector rotates until it's pointing up. Is that a feasible maneuver with elonerons?
I don't want to haul us too far off-topic here, but this seems on-point to the extent that if you can't model the heat loads and duration of those loads, you really don't know what you need. Having recently wallowed around in Earth-Mars porkchop plots, it's not super-difficult to find low-energy, fairly long time-of-flight trajectories that keep arrival speeds fairly low, but arrival speed rapidly becomes the primary constraint as you try to shorten time-of-flight. It'd be nice to work to some kind of figure of merit here. (And of course by "work", I mean "fool around in a space-nerdy kinda way".)
I guess the other wrinkle here is whether you're designing to direct entry or an aerobrake pass into an eccentric orbit, followed by a lower speed EDL.
As eriblo says, roll is about the velocity vector, not around the body axis. See the original BFR presentation at 35:33 :This was for the old 'Red Dragon' mission concept, but the principle for a cylindrical rather than conical lifting body is the same: roll 'upside down' when negative lift is required, and roll back upright afterwards.
That seems doable for a Dragon, which has a fairly low angle of attack and fairly stubby moments of inertia in the roll and pitch directions. As a result, it can roll pretty fast, and the stagnation point isn't going to move off of the TPS while you're rolling.
But how can you roll a Starship, which has high angle of attack, hefty pitch moments, and not the most responsive aerocontrols? And if you can roll it, how do you roll it in such a manner that you keep your free stream stagnation point on the TPS, rather than having it walk around to the unprotected dorsal side of the vehicle?
ISTM that the maneuver that a Starship would need is a combination roll/yaw maneuver, so that the angle of attack stays the same while the lift vector rotates until it's pointing up. Is that a feasible maneuver with elonerons?
I don't want to haul us too far off-topic here, but this seems on-point to the extent that if you can't model the heat loads and duration of those loads, you really don't know what you need. Having recently wallowed around in Earth-Mars porkchop plots, it's not super-difficult to find low-energy, fairly long time-of-flight trajectories that keep arrival speeds fairly low, but arrival speed rapidly becomes the primary constraint as you try to shorten time-of-flight. It'd be nice to work to some kind of figure of merit here. (And of course by "work", I mean "fool around in a space-nerdy kinda way".)
I guess the other wrinkle here is whether you're designing to direct entry or an aerobrake pass into an eccentric orbit, followed by a lower speed EDL.
As eriblo says, roll is about the velocity vector, not around the body axis.
The control surfaces will be sized to provide sufficient control authority - that is the sole reason for including them. I personally think the control logic will be significantly easier than most fly-by-wire aircraft which have more control surfaces all of which need to stay within tight speed/altitude/AoA-dependent envelopes. Starship could probably get quite far with just a simple control axis mapping and direct feedback.As eriblo says, roll is about the velocity vector, not around the body axis.
I understand that. That's fairly easy to do if the AoA is 0º, and only somewhat harder if it's 90º. But you're doing this because you need lift, and both of those cases have L/D = ~0. To get lift, you need the AoA between those extremes, so rotating about the velocity vector is essentially a controlled hypersonic spiral. I'm pretty sure that you can do pitch, roll, and yaw using just the four elonerons, but I'm not sure how much command authority you have if there are errors. And an error that moves the stagnation point off of the TPS is one that has to be corrected pretty quickly.
Radical, are your doubts not solved by watching the simulation of mars edl? It shows all maneuvers in dynamic detail. It checks out. Dont understand your concernsAs eriblo says, roll is about the velocity vector, not around the body axis.
I understand that. That's fairly easy to do if the AoA is 0º, and only somewhat harder if it's 90º. But you're doing this because you need lift, and both of those cases have L/D = ~0. To get lift, you need the AoA between those extremes, so rotating about the velocity vector is essentially a controlled hypersonic spiral. I'm pretty sure that you can do pitch, roll, and yaw using just the four elonerons, but I'm not sure how much command authority you have if there are errors. And an error that moves the stagnation point off of the TPS is one that has to be corrected pretty quickly.
Radical, are your doubts not solved by watching the simulation of mars edl? It shows all maneuvers in dynamic detail. It checks out. Dont understand your concerns
Radical, are your doubts not solved by watching the simulation of mars edl? It shows all maneuvers in dynamic detail. It checks out. Dont understand your concerns
A simulation from four years ago, built around a carbon composite vehicle, with a single delta wing, with a split flap, and a fixed dihedral? A simulation that doesn't use the skydiving technique? I still have some doubts.
Radical, are your doubts not solved by watching the simulation of mars edl? It shows all maneuvers in dynamic detail. It checks out. Dont understand your concerns
A simulation from four years ago, built around a carbon composite vehicle, with a single delta wing, with a split flap, and a fixed dihedral?
A simulation that doesn't use the skydiving technique?
I don’t see how “rotating about the velocity vector is essentially a controlled hypersonic spiral”. It’s just a roll maneuver. What does “spiral” mean here?As eriblo says, roll is about the velocity vector, not around the body axis.
I understand that. That's fairly easy to do if the AoA is 0º, and only somewhat harder if it's 90º. But you're doing this because you need lift, and both of those cases have L/D = ~0. To get lift, you need the AoA between those extremes, so rotating about the velocity vector is essentially a controlled hypersonic spiral. I'm pretty sure that you can do pitch, roll, and yaw using just the four elonerons, but I'm not sure how much command authority you have if there are errors. And an error that moves the stagnation point off of the TPS is one that has to be corrected pretty quickly.
closeup of some discovery spaceshuttle tiles on display at
Air and Space Museum Parkway Chantilly, VA
Tiles are from front side panel , (not very exposed) can see some marks from re=entry, can see some sort of gap filler, some has been worn away during re=entry, exposing some other sort of material between tiles.
If SN20 flies with tiles as they are now, I predict huge number will break/fall off during engine startup on launch,
some more falling off during ascent, will make for an interesting light show during re=entry
StarShip will likely be limited to now lower than ~30-40 degrees during reentry. Control authority will drop to near zero at zero degrees. Also, Max L/D occurs around this AoA range, so there isn't a need to go to lower AoA.
John
We are talking about different sims thenRadical, are your doubts not solved by watching the simulation of mars edl? It shows all maneuvers in dynamic detail. It checks out. Dont understand your concerns
A simulation from four years ago, built around a carbon composite vehicle, with a single delta wing, with a split flap, and a fixed dihedral? A simulation that doesn't use the skydiving technique? I still have some doubts.
StarShip will likely be limited to now lower than ~30-40 degrees during reentry. Control authority will drop to near zero at zero degrees. Also, Max L/D occurs around this AoA range, so there isn't a need to go to lower AoA.
John
Just to make sure: 0 deg AoA is when starship is belly flopping with neither nose or tail closer to the oncoming stream of air/plasma?
The sim in the dearmoon presentation has the present configuration except different fins planform. It's earth edl. Put it the toghether with the one in 2019 which is a mars reentry, and the sim in mk1 starship update, showing final bellyflop with the most actual configuration. You have everything you need.We are talking about different sims thenRadical, are your doubts not solved by watching the simulation of mars edl? It shows all maneuvers in dynamic detail. It checks out. Dont understand your concerns
A simulation from four years ago, built around a carbon composite vehicle, with a single delta wing, with a split flap, and a fixed dihedral? A simulation that doesn't use the skydiving technique? I still have some doubts.
StarShip will likely be limited to now lower than ~30-40 degrees during reentry. Control authority will drop to near zero at zero degrees. Also, Max L/D occurs around this AoA range, so there isn't a need to go to lower AoA.
John
Just to make sure: 0 deg AoA is when starship is belly flopping with neither nose or tail closer to the oncoming stream of air/plasma?
I don’t see how “rotating about the velocity vector is essentially a controlled hypersonic spiral”. It’s just a roll maneuver. What does “spiral” mean here?
The sim in the dearmoon presentation has the present configuration except different fins planform. It's earth edl. Put it the toghether with the one in 2019 which is a mars reentry, and the sim in mk1 starship update, showing final bellyflop with the most actual configuration. You have everything you need.
Oops -- terminology blooper. Yes, “roll” would be in body-centered coordinates and neither necessary or wise. What one wants is rotation of the vehicle around the velocity vector (w.r.t. the surrounding air), which redirects the lift vector while making no difference to thermal protection. What can be confusing is that for typical vehicles and typical flight conditions, the nominal body axis and velocity vector roughly coincide.I don’t see how “rotating about the velocity vector is essentially a controlled hypersonic spiral”. It’s just a roll maneuver. What does “spiral” mean here?
If you just did a roll (i.e., rotation about the x-axis) from a 30º angle of attack, you'd wind up at a -30º angle of attack, which would expose the top of the Starship to high stagnation pressures and heating.
StarShip will likely be limited to now lower than ~30-40 degrees during reentry. Control authority will drop to near zero at zero degrees. Also, Max L/D occurs around this AoA range, so there isn't a need to go to lower AoA.
John
Just to make sure: 0 deg AoA is when starship is belly flopping with neither nose or tail closer to the oncoming stream of air/plasma?
Also, a “barrel roll” in aerobatics is pretty much a rotation around the velocity vector, and definitely not around the vehicle axis (this is an “aileron roll”, which is very different at high AoA!). I had meant “roll” in the former not-wrong sense.Oops -- terminology blooper. Yes, “roll” would be in body-centered coordinates and neither necessary or wise. What one wants is rotation of the vehicle around the velocity vector (w.r.t. the surrounding air), which redirects the lift vector while making no difference to thermal protection. What can be confusing is that for typical vehicles and typical flight conditions, the nominal body axis and velocity vector roughly coincide.I don’t see how “rotating about the velocity vector is essentially a controlled hypersonic spiral”. It’s just a roll maneuver. What does “spiral” mean here?
If you just did a roll (i.e., rotation about the x-axis) from a 30º angle of attack, you'd wind up at a -30º angle of attack, which would expose the top of the Starship to high stagnation pressures and heating.
RVac 6 in tent 1.As it's technically part of the vehicle TPS: RVac has now gained a metallic skirt.
A peek into tent 3.
S22 common dome section inside tent 1.
Yes, it is windy today.
It is worth noting (especially in this thread) that while the max heating rate due to Raptor toasting looks to be similar to Starship reentry it is unlikely that Super Heavy will need any extra protection:interesting calculation. but wasn't the steel 3 mm or did I miss something?
304l:
Heat capacity: 0.5 J/g/K
Density: 8 g/cm3
Thickness: 4 mm
=> Areal heat capacity: 1.6 J/K/cm2
Max heat rate: 20 W/cm2 => Temperature increase: 12.5 K/s
It is worth noting (especially in this thread) that while the max heating rate due to Raptor toasting looks to be similar to Starship reentry it is unlikely that Super Heavy will need any extra protection:
I believe for super heavy it was, and still is intended to be 4mm. Starship itself has had thinner steel experiments performed, but it doesn’t need to withstand launching with a full starship on top of it, and not getting crushed.It is worth noting (especially in this thread) that while the max heating rate due to Raptor toasting looks to be similar to Starship reentry it is unlikely that Super Heavy will need any extra protection:interesting calculation. but wasn't the steel 3 mm or did I miss something?
304l:
Heat capacity: 0.5 J/g/K
Density: 8 g/cm3
Thickness: 4 mm
=> Areal heat capacity: 1.6 J/K/cm2
Max heat rate: 20 W/cm2 => Temperature increase: 12.5 K/s
Red RTV silicone think you could use that inbetween the tiles?The filler bars are not 'ceramic sheet', it's ceramic fibre (mat).
Seems the answer in part is yes, used on shuttle discovery to hold the spacer material in place, only a minimal amount seems to have been used see:
https://airandspace.si.edu/collection-objects/tile-gap-filler-shuttle-sts-114/nasm_A20060583000
Also it seems the filler between tiles is ceramic sheet, I would have thought something flexible would be better.
Something flexible with the consistency and rubberyness of silicone sealers would I think help stop ceramic tile breakage. Maybe there is nothing with that consistency that can handle the temperatures.
The spacer material on shuttle discovery was easily removed, as done per one space walk, seems they were only just held in position.
see
https://www.theguardian.com/science/2005/aug/03/spaceexploration.internationalnews1
it appears they have wrapped the white nomex or similar fabric around the edges, if you look the right hand top of same pic you can see more clearly the sides are wrapped in the white material, pic attached, I wonder what the glue is going underneath?We can be fairly sure it is not Nomex (max temperature 370°C) - "refractory ceramic fiber felt" is likely unspecific enough to be correct, i.e. similar or even identical to what is under the other tiles.
seems testing of rtv ( room temperature vulcanising) silicones goes back to the 1960s, this JPL paper maybe around the start of when they were testing them for space use.Technological progress is not only limited by time and effort (i.e. money) but ultimately by the laws of physics. Just because some thing was invented 50 years ago does not automagically mean that it has or even can be improved upon. They are after all using 304l SS which is 100 years old technology...
https://ntrs.nasa.gov/api/citations/19650020859/downloads/19650020859.pdf
560 silicone is tested at that time, its now over 50years years down the track, surely there are now available better suited materials or perhaps it really is time for some products to be developed.
seems testing of rtv ( room temperature vulcanising) silicones goes back to the 1960s, this JPL paper maybe around the start of when they were testing them for space use.Technological progress is not only limited by time and effort (i.e. money) but ultimately by the laws of physics. Just because some thing was invented 50 years ago does not automagically mean that it has or even can be improved upon. They are after all using 304l SS which is 100 years old technology...
https://ntrs.nasa.gov/api/citations/19650020859/downloads/19650020859.pdf
560 silicone is tested at that time, its now over 50years years down the track, surely there are now available better suited materials or perhaps it really is time for some products to be developed.
There might well be incremental improvements and adaption to unique requirements to be done but I would think that the field of high temperature flexible seals and adhesives is fairly mature considering how much money has been spent on optimizing internal combustion engines.
seems testing of rtv ( room temperature vulcanising) silicones goes back to the 1960s, this JPL paper maybe around the start of when they were testing them for space use.Technological progress is not only limited by time and effort (i.e. money) but ultimately by the laws of physics. Just because some thing was invented 50 years ago does not automagically mean that it has or even can be improved upon. They are after all using 304l SS which is 100 years old technology...
https://ntrs.nasa.gov/api/citations/19650020859/downloads/19650020859.pdf
560 silicone is tested at that time, its now over 50years years down the track, surely there are now available better suited materials or perhaps it really is time for some products to be developed.
There might well be incremental improvements and adaption to unique requirements to be done but I would think that the field of high temperature flexible seals and adhesives is fairly mature considering how much money has been spent on optimizing internal combustion engines.
For a lot of reasons, the relevant definition of “high temperature” and the desired properties here are pretty different. That doesn’t mean there’s necessarily any low hanging fruit for development, but I think it does mean the automotive seals work is only marginally relevant.
It would be great if the current Starship tiles are able to handle that kind of heat flux as that would be state-of-the-art. I am no expert but I have wondered quite a bit about this, so here is my "quick" recap for those who are interested:It is worth noting (especially in this thread) that while the max heating rate due to Raptor toasting looks to be similar to Starship reentry it is unlikely that Super Heavy will need any extra protection:I think re-entry peak heat rate is a lot higher? It should be over 100 W/cm^2
some excellent links there, though being patents they do try to cover all bases and multiple material combinations,
this article is informative on history of heatshield tiles up to 1980.
https://history.nasa.gov/sts1/pages/tps.html
This is a very obvious statement but the conditions the starship re-enters through, has the ability to completely destroy the space craft, as has been seen many times in the past. So a bunch of tiles being blown off during venting on the ground, and changes in shape of the stailness during crane movements or tank filling are somewhat concerning. As they are I really expect serious tile damage and detachment during static fire, even though a very short duration test. I wonder if it will be a night time test fire.
Have I got this right? You are suggesting that SpaceX might do a night time test so as to hide any possible damage from onlookers?That's a bit of a stretch, no? Given the times of the test windows, and past testing performance, its quite reasonable to idly wonder if testing will happen after dark, impeding the ability of the peanut gallery to watch whats going on. Jumping from there to the conclusion that SpaceX is trying to hide something just doesn't follow.
Every failure to date has been in public and never hidden. Plus they have some of the smartest engineers on the planet so I think it's a pretty good bet that they understand about expanding tanks and blowing vents and the re-entry regime and are way ahead of us in their thinking and understanding of the issues.some excellent links there, though being patents they do try to cover all bases and multiple material combinations,
this article is informative on history of heatshield tiles up to 1980.
https://history.nasa.gov/sts1/pages/tps.html
This is a very obvious statement but the conditions the starship re-enters through, has the ability to completely destroy the space craft, as has been seen many times in the past. So a bunch of tiles being blown off during venting on the ground, and changes in shape of the stailness during crane movements or tank filling are somewhat concerning. As they are I really expect serious tile damage and detachment during static fire, even though a very short duration test. I wonder if it will be a night time test fire.
Have I got this right? You are suggesting that SpaceX might do a night time test so as to hide any possible damage from onlookers?That's a bit of a stretch, no? Given the times of the test windows, and past testing performance, its quite reasonable to idly wonder if testing will happen after dark, impeding the ability of the peanut gallery to watch whats going on. Jumping from there to the conclusion that SpaceX is trying to hide something just doesn't follow.
Every failure to date has been in public and never hidden. Plus they have some of the smartest engineers on the planet so I think it's a pretty good bet that they understand about expanding tanks and blowing vents and the re-entry regime and are way ahead of us in their thinking and understanding of the issues.some excellent links there, though being patents they do try to cover all bases and multiple material combinations,
this article is informative on history of heatshield tiles up to 1980.
https://history.nasa.gov/sts1/pages/tps.html
This is a very obvious statement but the conditions the starship re-enters through, has the ability to completely destroy the space craft, as has been seen many times in the past. So a bunch of tiles being blown off during venting on the ground, and changes in shape of the stailness during crane movements or tank filling are somewhat concerning. As they are I really expect serious tile damage and detachment during static fire, even though a very short duration test. I wonder if it will be a night time test fire.
some excellent links there, though being patents they do try to cover all bases and multiple material combinations,
this article is informative on history of heatshield tiles up to 1980.
https://history.nasa.gov/sts1/pages/tps.html
This is a very obvious statement but the conditions the starship re-enters through, has the ability to completely destroy the space craft, as has been seen many times in the past. So a bunch of tiles being blown off during venting on the ground, and changes in shape of the stailness during crane movements or tank filling are somewhat concerning. As they are I really expect serious tile damage and detachment during static fire, even though a very short duration test. I wonder if it will be a night time test fire.
" So a bunch of tiles being blown off during venting on the ground, and changes in shape of the stailness during crane movements or tank filling are somewhat concerning. "
" So a bunch of tiles being blown off during venting on the ground, and changes in shape of the stailness during crane movements or tank filling are somewhat concerning. "
Can someone please share with me anything that supports this continuing notion that the nosecone flexes during lifts and therefore looses tiles?
This seems to be a concept taken as a truth by many on this forum and I can't imagine what has possibly driven it. It makes absolutely no sense.
Your burden of proof is inverted.For the claim that tiles are lost when the nose is lifted, the burden of proof is to show tiles have been lost when the nose has been lifted.
Also, steel below its elastic limit [better: working stress] will stretch very little, and lifting from the nose won’t cause significant bending, either. The change in distance between pins will be very, very, very small.Your burden of proof is inverted.For the claim that tiles are lost when the nose is lifted, the burden of proof is to show tiles have been lost when the nose has been lifted.
Thus far, I cannot recall this being observed. Tiles have been observed as lost during pressurisation tests, but not as a result of a lift (even as just inferred tile loss from before/after photos).
If I express concern about tiles getting shed, don't take is as a 'sky is falling' type of concern. It's a mix of I (and everybody else) has never seen anything quite like this and SX has been known to give something a try when their modeling doesn't quite reach far enough. At a minimum the modeling improves.Also, steel below its elastic limit will stretch very little, and lifting from the nose won’t cause significant bending, either. The change in distance between pins will be very, very, very small.Your burden of proof is inverted.For the claim that tiles are lost when the nose is lifted, the burden of proof is to show tiles have been lost when the nose has been lifted.
Thus far, I cannot recall this being observed. Tiles have been observed as lost during pressurisation tests, but not as a result of a lift (even as just inferred tile loss from before/after photos).
All I can say is SpaceX WILL solve the problem, there is no doubt about that, and as per usual I will be amazed once again at how they do it, but what we can see from boca chica there is a big issue with tiles, whatever is the true reasons for cracking/fracturing tiles, all pre-launch, must be a concern considering the stresses the ship will go through on the way back to earth. I'm just going by what I see in videos/pictures and a little research, yup it will be obvious if the tiles are effected by static fire whether they do it at night or day time, but it would be a little embarrasing if they had a massive detiling event on static fire. What do you people think? Anyone care to guesstimate what percentage of tiles will crack or be damaged during static fire? Its a very very short event.
TUFROC uses a HETC treatment (includes tantalum disilicide for improved thermal and emissive properties) on an intermediate oxidation protected ceramic carbon layer on top of the TUFI/AETB to mange 3000 °F (1922 K, 70 W/cm2) for ~10 min or up to 3600 °F (2255 K, 132 W/cm2) for ~1 min. This matches the multi-use limit on the Shuttles RCC panels at 3000 °F.
TUFROC uses a HETC treatment (includes tantalum disilicide for improved thermal and emissive properties) on an intermediate oxidation protected ceramic carbon layer on top of the TUFI/AETB to mange 3000 °F (1922 K, 70 W/cm2) for ~10 min or up to 3600 °F (2255 K, 132 W/cm2) for ~1 min. This matches the multi-use limit on the Shuttles RCC panels at 3000 °F.
So if the Starship tiles are TUFROC-like, then from the inside out, we have:
1) The pin.
2) Maybe some kind of gap filler / structural slip / bearing to deal with expansion, contraction, and mechanical stresses.
3) AETB as the bulk of the insulating layer.
4) HETC coated with RCG for high refractory, high emissivity, low absorptivity.
I didn't go back a huge number of pages on the thread, so I apologize if this got answered somewhere: With advanced TUFROC, the slide deck you linked implied that the pin connected to the ROCCI (the HETC/RCG combo). Do you think that's what's happening with the pinned tiles for Starship? Or have they figured out some way to anchor the pin latches in the AETB (or whatever the insulator is)?
The other thing I'm not understanding is how the pin isn't a huge heat conductor through the AETB. This is one of the reasons why I wondered if the latches were in the AETB, but even then, they should still increase the conductivity of the whole system, and you don't want that. What am I missing?
The other thing I'm not understanding is how the pin isn't a huge heat conductor through the AETB. This is one of the reasons why I wondered if the latches were in the AETB, but even then, they should still increase the conductivity of the whole system, and you don't want that. What am I missing?Thermal conductance is proportional to conductivity x cross-section.
And, for a metal, SS is a lousy heat conductor.The other thing I'm not understanding is how the pin isn't a huge heat conductor through the AETB. This is one of the reasons why I wondered if the latches were in the AETB, but even then, they should still increase the conductivity of the whole system, and you don't want that. What am I missing?Thermal conductance is proportional to conductivity x cross-section.
Pin conductivity is high (metal), but cross-section(pins) << cross-section(tiles), so relative conductance is low.
Also, the pins don’t go all the way through and and probably make poor (point-like) thermal contact with the tiles.
This has come up before.
And, for a metal, SS is a lousy heat conductor.
It's a two edged sword. The pins conduct poorly to the skin, but when the heat impulse does get there it doesn't conduct away and spread out very fast. Grumble, grumble.And, for a metal, SS is a lousy heat conductor.
If you were going to have hot spots, you'd want the metal to be a good conductor.
The skin is only 4 mm think, much thinner than the length of the pins. And of course the cryo fuels have chilled the skin from the inside. So a heat sink is less than 4 mm away from the surface of the skin.It's a two edged sword. The pins conduct poorly to the skin, but when the heat impulse does get there it doesn't conduct away and spread out very fast. Grumble, grumble.And, for a metal, SS is a lousy heat conductor.
If you were going to have hot spots, you'd want the metal to be a good conductor.
It's complicated. The pin might have the equivalent of a 4mm x 4mm cross section. The steel under a missing tile might have a cross sectional surface to adjoining steel areas of about 4mm depth x 500 mm circumference. In addition to the heat transfer into the ship. the cross section into the ship is perhaps equivalent to 300 mm x 300 mm. When the missing tile is over a tank, the heat will transfer to the very cold gas or liquid in the tank convectively: this transfer is overwhelmingly larger that any conduction in the steel. When the missing tile is not over a tank, things will get interesting. My guess (no data, just a guess) is that convective heat transfer into atmospheric pressured air will easily keep the steel cool, but what about an unpressurized cargo hold?The skin is only 4 mm think, much thinner than the length of the pins. And of course the cryo fuels have chilled the skin from the inside. So a heat sink is less than 4 mm away from the surface of the skin.It's a two edged sword. The pins conduct poorly to the skin, but when the heat impulse does get there it doesn't conduct away and spread out very fast. Grumble, grumble.And, for a metal, SS is a lousy heat conductor.
If you were going to have hot spots, you'd want the metal to be a good conductor.
this transfer is overwhelmingly larger that any conduction in the steel.That's a definitely a 'calculations required' claim.
When the missing tile is over a tank, the heat will transfer to the very cold gas or liquid in the tank convectively:
TUFROC uses a HETC treatment (includes tantalum disilicide for improved thermal and emissive properties) on an intermediate oxidation protected ceramic carbon layer on top of the TUFI/AETB to mange 3000 °F (1922 K, 70 W/cm2) for ~10 min or up to 3600 °F (2255 K, 132 W/cm2) for ~1 min. This matches the multi-use limit on the Shuttles RCC panels at 3000 °F.
So if the Starship tiles are TUFROC-like, then from the inside out, we have:
1) The pin.
2) Maybe some kind of gap filler / structural slip / bearing to deal with expansion, contraction, and mechanical stresses.
3) AETB as the bulk of the insulating layer.
4) HETC coated with RCG for high refractory, high emissivity, low absorptivity.
I didn't go back a huge number of pages on the thread, so I apologize if this got answered somewhere: With advanced TUFROC, the slide deck you linked implied that the pin connected to the ROCCI (the HETC/RCG combo). Do you think that's what's happening with the pinned tiles for Starship? Or have they figured out some way to anchor the pin latches in the AETB (or whatever the insulator is)?
The other thing I'm not understanding is how the pin isn't a huge heat conductor through the AETB. This is one of the reasons why I wondered if the latches were in the AETB, but even then, they should still increase the conductivity of the whole system, and you don't want that. What am I missing?
I think you missed the part where these tiles are not TUFROC.
I think you missed the part where these tiles are not TUFROC.
eriblo's post does not say that.
TUFROC has a completely separate ceramic carbon cap on top of a refractory ceramic fiber base (both of which are porous bulk insulators). TUFROC is glued to the spacecraft skin, the pins-connecting-to-embedded-metal-brackets are a completely separate attachment system. We have seen no sign of separate layers beyond the surface coating or any carbon based material so I think the current tiles are much closer to a denser version of TUFI tiles.I think you missed the part where these tiles are not TUFROC.
eriblo's post does not say that.
I know they're not TUFROC, which is why I said "TUFROC-like". Is that correct? Or at least to the extent that they're:
1) Pinned attachments. (And I'm still confused how the pins are mechanically anchored into the tiles.)
2) RCG of some sort on the outside, with some thin layer of high-heat-capacity refractory substance just below.
3) Then something thicker with very low conductivity below that.
TUFROC has a completely separate ceramic carbon cap on top of a refractory ceramic fiber base (both of which are porous bulk insulators). TUFROC is glued to the spacecraft skin, the pins-connecting-to-embedded-metal-brackets are a completely separate attachment system. We have seen no sign of separate layers beyond the surface coating or any carbon based material so I think the current tiles are much closer to a denser version of TUFI tiles.
https://twitter.com/elonmusk/status/1451354108531728384 (https://twitter.com/elonmusk/status/1451354108531728384)How can this be reasonable at this late date?
https://twitter.com/elonmusk/status/1451354108531728384 (https://twitter.com/elonmusk/status/1451354108531728384)How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
Shaking out the problems (literally) haha
https://twitter.com/elonmusk/status/1451354108531728384 (https://twitter.com/elonmusk/status/1451354108531728384)How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
We have to remember that the Starship vehicle will NEVER light its engines on the ground for normal flights, because it will normally sit on top of the Booster to get off the ground. So tiles falling off because of a static fire on the ground is not necessarily a bad sign, since that is a condition they are not designed to operate in.
The bigger question is whether the tiles that did fall off during the static fire would have stayed on during a launch on top of the Booster, with the air trying to rip them off...
We're a long ways from there yet.How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
We have to remember that the Starship vehicle will NEVER light its engines on the ground for normal flights, because it will normally sit on top of the Booster to get off the ground. So tiles falling off because of a static fire on the ground is not necessarily a bad sign, since that is a condition they are not designed to operate in.
The bigger question is whether the tiles that did fall off during the static fire would have stayed on during a launch on top of the Booster, with the air trying to rip them off...
Yes but actually no, point to point starship will launch on it's own and it will have even more engines
https://twitter.com/elonmusk/status/1451354108531728384 (https://twitter.com/elonmusk/status/1451354108531728384)How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
The heat tiles will also experience an environment that they would not normally encounter. At launch Starship will be 50m away from the Raptors on Superheavy and when the Raptors on Starship fire up it will be out of the atmosphere. That said, no doubt they will still take a lot of vibration and will need design tweaks etc. But yes its a prototype...https://twitter.com/elonmusk/status/1451354108531728384 (https://twitter.com/elonmusk/status/1451354108531728384)How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
It is completely reasonable because this is not a ‘late date’. This is an early flight prototype, not a finished product. If tiles fall off they replace them. If tiles keep falling off they tweak the design. That’s the whole point of this development method.
this transfer is overwhelmingly larger that any conduction in the steel.That's a definitely a 'calculations required' claim.
600-1200kWm^-2 are a rough range for thermal flux during re-entry heating, so ~300mm x 300mm of exposed stainless steel is being bathed by 54-108kW of heating. To stay below ~650°C (significant strength loss beyond that), you have:
An 850K (~650°C and ~-200°C on either side) temperature gradient
A 4mm wall thickness (0.004m)
A 16.2 Wm^-1K^-1 thermal conductivity for 304L
So you can tolerate ~55Wm^-2 in steady-state for bare 304L. That's quite a way from what's necessary to handle EDL, hence why the tiles are installed to start with.
this transfer is overwhelmingly larger that any conduction in the steel.That's a definitely a 'calculations required' claim.
600-1200kWm^-2 are a rough range for thermal flux during re-entry heating, so ~300mm x 300mm of exposed stainless steel is being bathed by 54-108kW of heating. To stay below ~650°C (significant strength loss beyond that), you have:
An 850K (~650°C and ~-200°C on either side) temperature gradient
A 4mm wall thickness (0.004m)
A 16.2 Wm^-1K^-1 thermal conductivity for 304L
So you can tolerate ~55Wm^-2 in steady-state for bare 304L. That's quite a way from what's necessary to handle EDL, hence why the tiles are installed to start with.
That's off by ~5 orders of magnitude, you multiplied by 0.004 instead of dividing.
(16.2 Wm^-1K^-1) × (850K) / (0.004m) = 3.4 × 10^6 Wm^-2
so about 300 kW /m^2
Yes, this isn’t late as in “too late to succeed” -- flexible development, fast iteration, etc., can deal with the problem.https://twitter.com/elonmusk/status/1451354108531728384 (https://twitter.com/elonmusk/status/1451354108531728384)How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
It is completely reasonable because this is not a ‘late date’. This is an early flight prototype, not a finished product. If tiles fall off they replace them. If tiles keep falling off they tweak the design. That’s the whole point of this development method.
It is, however, surprisingly late (this is subjective and absolutely true: I’m surprised!) considering the apparent number of design iterations on what looks like a problem that should be readily solvedIt's literally the first iteration of a full heat-shield installation (and not single small patches), and the first firing of an RVac (which is mechanically coupled directly to the outer skin, rather than just to the thrust puck) attached to Starship. There has been no earlier iteration yet.
Yes, this isn’t late as in “too late to succeed” -- flexible development, fast iteration, etc., can deal with the problem.https://twitter.com/elonmusk/status/1451354108531728384 (https://twitter.com/elonmusk/status/1451354108531728384)How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
It is completely reasonable because this is not a ‘late date’. This is an early flight prototype, not a finished product. If tiles fall off they replace them. If tiles keep falling off they tweak the design. That’s the whole point of this development method.
It is, however, surprisingly late (this is subjective and absolutely true: I’m surprised!) considering the apparent number of design iterations on what looks like a problem that should be readily solved: Make tiles that aren’t cracked (after pre-installation QC) and use fasteners that hold the tiles securely without applying too much stress.
I continue to wonder whether they’ve chosen a design that over-constrains the attachments -- 3 translational constraints per pin is 9 per tile, which is 3 too many for a stress-free kinematic constraint (https://en.wikipedia.org/wiki/Kinematic_coupling#Maxwell_coupling) on the tile positions and orientations. A formally over-constrained design can work (only?) if the pins can absorb manufacturing tolerances and in-use displacements through elastic deformation (acting as springs). [Otherwise, not so good -- strong and stiff pins lead to (unnecessarily) high stress in tiles.]
TL;DR: Should work already, will work eventually, but what seems to be the current design seems questionable.
We shouldn't be downplaying the tile problem.
NO tiles should be falling off during static fire. Otherwise, reentry will surely fail. I mean, this is analogous to the spray-on insulation of the SS external tank. NASA knew it was a problem and kept on flying....
We're a long ways from there yet.How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
We have to remember that the Starship vehicle will NEVER light its engines on the ground for normal flights, because it will normally sit on top of the Booster to get off the ground. So tiles falling off because of a static fire on the ground is not necessarily a bad sign, since that is a condition they are not designed to operate in.
The bigger question is whether the tiles that did fall off during the static fire would have stayed on during a launch on top of the Booster, with the air trying to rip them off...
Yes but actually no, point to point starship will launch on it's own and it will have even more engines
Before and after composite from RGV and StarshipGazer. From the belly view, I can count 9 lost or partially lost tiles.
Before and after composite from RGV and StarshipGazer. From the belly view, I can count 9 lost or partially lost tiles.
So what would the defect rate be, which think is an important metric? Someone must have done an estimate of total tile count (but can't find it)... anyone?
Before and after composite from RGV and StarshipGazer. From the belly view, I can count 9 lost or partially lost tiles.
So what would the defect rate be, which think is an important metric? Someone must have done an estimate of total tile count (but can't find it)... anyone?
Maybe 10,000 tiles. So 10 out of 10,000 is .1% tile breakage.
This to me means that it isn't a fundamental design issue and is just an "acceptable" failure of installation or manufacture. Something that will be worked out.
We're a long ways from there yet.How can this be reasonable at this late date?
If these are known-bad tiles that they haven’t bothered to replace, that’s sort of almost OK.
But otherwise...??
We have to remember that the Starship vehicle will NEVER light its engines on the ground for normal flights, because it will normally sit on top of the Booster to get off the ground. So tiles falling off because of a static fire on the ground is not necessarily a bad sign, since that is a condition they are not designed to operate in.
The bigger question is whether the tiles that did fall off during the static fire would have stayed on during a launch on top of the Booster, with the air trying to rip them off...
Yes but actually no, point to point starship will launch on it's own and it will have even more engines
Will point to point even need a "full" heat shield? It's going to be considerably less energetic without Superheavy, and so reentry heating will be significantly reduced.
I dont know about rear structure of tile, how its connected to y frame,I hope there is not such ice layer because it will make planning trajectories difficult due to its unknown mass. And it would take dV away too.
I am curious about this though:
When the static fires occured there was a type of mist could be seen coming from the tiles, I'm not sure what
that mist was. It seemed to come from all areas of the tiles except maybe the top half of the nosecone.
If the tanks were full it might have been ice from atmospheric water vapour that chilled down due to the cold
fuels in the tanks. Anyone know what it was?
Anyhow led me to an idea ( bit of a crazy idea):
what if the white backing material (whatever it is) was to be drenched with water as the tanks are filling up, assuming it can hold liquid water, lets assume the water then freezes due to cold propellents inside tanks, and you land up with a very thick layer of ice under the tiles ( assume the expansion of the water doesn't hurt the tiles).
Yup its going to be heavy but....lets assume that water soaked white backing felt makes its too orbit fully saturated with water, or even largely still as ice, once in orbit its cold out there, ice will remain as ice.
So you have taken a good source of water with you too space ( if needed).....but....on re-entry all that water can turn back into liquid and then gas, giving a layer of protection to the tiles as the out-gases absorb energy of re-entry. ( back and sides of tiles might need that black borosilicate( or similar) layer).
Just a random brain fart, but... How cool would it be it they'll rig a Raptor engine on an horizontal support, hook it up to some LOX and LCH4 pipes and fire it up against a vertical standing StarShip with complete heat shield? Could it validate or prove the heat shield concept wrong without requiring an orbital flight, just in case FAA doesn't allow it anytime soon?Like for every thing of this kind the development and construction of this test rig would take more time than the orbital flight. Moreover, even if the realtor engine exhaust *might* be very roughly in the ballpark for the temperature, and surely low in the velocity, the density and chemical composition are way off. Moreover the mechanism that causes the heating during twenty is the shockwave compression, not a combustion.
Before and after composite from RGV and StarshipGazer. From the belly view, I can count 9 lost or partially lost tiles.This is enough damage for re-entry RUD?
this transfer is overwhelmingly larger that any conduction in the steel.That's a definitely a 'calculations required' claim.
600-1200kWm^-2 are a rough range for thermal flux during re-entry heating, so ~300mm x 300mm of exposed stainless steel is being bathed by 54-108kW of heating. To stay below ~650°C (significant strength loss beyond that), you have:
An 850K (~650°C and ~-200°C on either side) temperature gradient
A 4mm wall thickness (0.004m)
A 16.2 Wm^-1K^-1 thermal conductivity for 304L
So you can tolerate ~55Wm^-2 in steady-state for bare 304L. That's quite a way from what's necessary to handle EDL, hence why the tiles are installed to start with.
That's off by ~5 orders of magnitude, you multiplied by 0.004 instead of dividing.
(16.2 Wm^-1K^-1) × (850K) / (0.004m) = 3.4 × 10^6 Wm^-2
so about 300 kW /m^2
Before and after composite from RGV and StarshipGazer. From the belly view, I can count 9 lost or partially lost tiles.This is enough damage for re-entry RUD?
Good calculation on the heat flux through the SS, but the process is going to be limited by Stefan Boltzmann:
[snip]
In other words, to maintain equilibrium temperature of the stainless steel sheet, the impinging heat flux from re-entry must be less than 50kW/m^2. Otherwise the steel will heat up because it can't radiate the heat fast enough.
Before and after composite from RGV and StarshipGazer. From the belly view, I can count 9 lost or partially lost tiles.This is enough damage for re-entry RUD?
I dont know about rear structure of tile, how its connected to y frame,A BOE, shows this much water to be HEAVY. With a 4.5m radius and ~50m of height covered with tiles, ignoring the fin covering and assuming a 1cm layer of water, the water weighs in at ~7t. There's a risk that the freezing water could pop tiles off. It would also be off center mass (which might add passive stability during the belly flop) and would probably lend itself to uneven buildup without a lot of engineering.
I am curious about this though:
When the static fires occured there was a type of mist could be seen coming from the tiles, I'm not sure what
that mist was. It seemed to come from all areas of the tiles except maybe the top half of the nosecone.
If the tanks were full it might have been ice from atmospheric water vapour that chilled down due to the cold
fuels in the tanks. Anyone know what it was?
Anyhow led me to an idea ( bit of a crazy idea):
what if the white backing material (whatever it is) was to be drenched with water as the tanks are filling up, assuming it can hold liquid water, lets assume the water then freezes due to cold propellents inside tanks, and you land up with a very thick layer of ice under the tiles ( assume the expansion of the water doesn't hurt the tiles).
Yup its going to be heavy but....lets assume that water soaked white backing felt makes its too orbit fully saturated with water, or even largely still as ice, once in orbit its cold out there, ice will remain as ice.
So you have taken a good source of water with you too space ( if needed).....but....on re-entry all that water can turn back into liquid and then gas, giving a layer of protection to the tiles as the out-gases absorb energy of re-entry. ( back and sides of tiles might need that black borosilicate( or similar) layer).
Are we sure there is a void ie is there really a back piece of ceramic? It looks like the back indented three sections would get at least partly filled in by the blanket when the tile is fixed to the pins.
Yeah agree. Especially if initial main feature of bayonet clip design doesn't work. You avoid too much optimization for nothing. So its in a way sad that SpaceX needs build all infrastructure from scratch first and wait for public opinions. Also its rural and natural habitat location doesn't help too much in terms of speedup the process in testing even more. Also transport between facilities at boca are logistical hussle.Sad that SpaceX needs to build all infrastructure from scratch first and wait for public opinions? Do you mean that it's a little bit unfortunate that all of their experiments and inevitable mistakes are on public display?
So i agree engineers are feeling very angsty about first flight and its ramification so they can get back too work at its heat shield design even further. At end of day they can torch tiles as much they want in lab. All that vibrations, head soaks, acoustics are hard too sim in CFD and NASAs windtunnels. Even if there is a way to test that system without scaling problems.
Before and after composite from RGV and StarshipGazer. From the belly view, I can count 9 lost or partially lost tiles.This is enough damage for re-entry RUD?
No, BT52 was getting at SX building out then going through the FAA public comment process for an up/down on what's already done.Yeah agree. Especially if initial main feature of bayonet clip design doesn't work. You avoid too much optimization for nothing. So its in a way sad that SpaceX needs build all infrastructure from scratch first and wait for public opinions. Also its rural and natural habitat location doesn't help too much in terms of speedup the process in testing even more. Also transport between facilities at boca are logistical hussle.Sad that SpaceX needs to build all infrastructure from scratch first and wait for public opinions? Do you mean that it's a little bit unfortunate that all of their experiments and inevitable mistakes are on public display?
So i agree engineers are feeling very angsty about first flight and its ramification so they can get back too work at its heat shield design even further. At end of day they can torch tiles as much they want in lab. All that vibrations, head soaks, acoustics are hard too sim in CFD and NASAs windtunnels. Even if there is a way to test that system without scaling problems.
I imagine the engineers are all a bit nervous. They just have to do there best and hope that 1) it's not their bit that fails and 2) that if their bit does fail it's not some sort of school boy error type thing (school boy error in terms of SpaceX rocketry covers a lot of ground).
thanks OTV booster for the calcs on crazy water idea. 7 tonnes is quite a bit of water, compared to say 77kg of clips and tiles, is that really all it weighs? 7 tonnes of water though might be rather useful , say , on the moon.Are you serious? Useable water on the moon would include it being "in" something. Or if ICE, then in convenient blocks-still stored ready for use. Stick on the side of the ship, busily sublimating in the sunlight, most of it above ladder height, and half of it hidden in insulation matting under tiles - is, mmm, inconvenient!
Lets say do both sides of the ship with water/felt and tiles, control issues not such a problem and 14 tonnes of water to play with on the moon.
thanks OTV booster for the calcs on crazy water idea. 7 tonnes is quite a bit of water, compared to say 77kg of clips and tiles, is that really all it weighs? 7 tonnes of water though might be rather useful , say , on the moon.
Lets say do both sides of the ship with water/felt and tiles, control issues not such a problem and 14 tonnes of water to play with on the moon.
thanks OTV booster for the calcs on crazy water idea. 7 tonnes is quite a bit of water, compared to say 77kg of clips and tiles, is that really all it weighs? 7 tonnes of water though might be rather useful , say , on the moon.No, that 77kg was in addition to what's already there and was strictly a 'for example' type of number. It could be ten times heavier and still be an order of magnitude less than the water.
Lets say do both sides of the ship with water/felt and tiles, control issues not such a problem and 14 tonnes of water to play with on the moon.
I'm not nearly as confident as you around this statement. At best I'd say there are probably many single tile losses that might be Ok. But I wouldn't be surprised if there are some single tile losses that could be very bad. And I'd add that some single tile losses might result in loosing adjacent tiles due to aerodynamic force and weakened steel. If nothing else, modeling how the ship reacts to various tile failures seems like a very difficult task.Before and after composite from RGV and StarshipGazer. From the belly view, I can count 9 lost or partially lost tiles.This is enough damage for re-entry RUD?
No. missing tiles are not adjacent, and Superwool backing is sufficient in a small surface area to protect for one re-entry.
Numerous discussions about this in threads above. Tl;DR SpaceX would no design a system with 10k failure points of which zero are allowed to fail before vehicle loss. (Space Shuttle and Boeing 737-Max being exceptions to the single point of failure rule.... how did that turn out?)
thanks OTV booster for the calcs on crazy water idea. 7 tonnes is quite a bit of water, compared to say 77kg of clips and tiles, is that really all it weighs? 7 tonnes of water though might be rather useful , say , on the moon.
Lets say do both sides of the ship with water/felt and tiles, control issues not such a problem and 14 tonnes of water to play with on the moon.
77 kg for only the pin and attachments, if they weigh 5 grams each. The entire heat shield is likely in the 7 metric ton range.
I think that the only way to find out whetever one tile loss is fatal or how dangerouse it is is to wait for the first reentry. We are discussing this from a lot of time, and we don't have much added information that could help us in this front. We should beware while discussing this aspect,because in this cases we risk that truth are built in this forum just because many agree and they are riproposed many times.I'm not nearly as confident as you around this statement. At best I'd say there are probably many single tile losses that might be Ok. But I wouldn't be surprised if there are some single tile losses that could be very bad. And I'd add that some single tile losses might result in loosing adjacent tiles due to aerodynamic force and weakened steel. If nothing else, modeling how the ship reacts to various tile failures seems like a very difficult task.Before and after composite from RGV and StarshipGazer. From the belly view, I can count 9 lost or partially lost tiles.This is enough damage for re-entry RUD?
No. missing tiles are not adjacent, and Superwool backing is sufficient in a small surface area to protect for one re-entry.
Numerous discussions about this in threads above. Tl;DR SpaceX would no design a system with 10k failure points of which zero are allowed to fail before vehicle loss. (Space Shuttle and Boeing 737-Max being exceptions to the single point of failure rule.... how did that turn out?)
And I'd add that some single tile losses might result in loosing adjacent tiles due to aerodynamic force and weakened steel.
Work continues on Ship 21 nosecone.Two tiles added to the nose section appear to be either missing their black RCG top layer, have a white top layer of unknown composition, or have been painted white over the RCG. It does not appear to just be a reflectance trick as the surrounding tiles at the same or similar sun angle are not the same uniform white.
Sorry to harp on the water blanket idea, the tiles are good heat insulators, they can get very hot and heat conductance is very slow ( if I've got the right idea), so they would also make good insulators to keep things cool.For the record I believe this idea has exactly zero chance of ever being implemented in any practical way. I think the technical challenges in implementing this in any practical way are far more severe that you realize, and its most likely completely hopeless as a way to get water to the moon (or anywhere really). But the bigger question here isn't how?, it's why?. Water is heavy, so ISTM that the most logical thing to do is put it in a tank. Your 7 tons of water would take up less that one percent of the pressurized volume of Starship. Alternatively, if you wanted to just ship water to the moon, you'd run into mass limits long before you ever hit volume limits, so just carry it inside (as liquid, in a tank). Before you embark on the very substantial task of explaining the how of this notion, I would encourage you to think long and hard about the why.
Lets say a layer of water ice makes it too the moon ( embedded in the backing fabric)
While on the moon ( or in space) in shade it will stay as ice, exposed to sunlight it will evaporate or sublime, rather than being a bad thing, that gives an easy way to covert it too liquid for use. Just how to capture the evaporated/sublimed water would be tricky problem to solve, probably could be done.
Maybe take out a few tiles, put on a clear window, with tube that takes away evaporated/sublimed water, might not be that hard.
On ascent from earth I think the water would make it to cold space as ice due to insulation of tiles, it would take some energy away from the propellents, so longer propellent filling time might be needed. Gap between the tiles is another issue.
Work continues on Ship 21 nosecone.Two tiles added to the nose section appear to be either missing their black RCG top layer, have a white top layer of unknown composition, or have been painted white over the RCG. It does not appear to just be a reflectance trick as the surrounding tiles at the same or similar sun angle are not the same uniform white.
This might have been covered before (very long thread), but I am wondering why they are not using bigger tiles, at least on the cylindrical section. Would seem like a lot less work for installation and might need less mounting points. Is it a problem with manufacturing them to a bigger size (e.g. more potential waste due to manufacturing faults)?They did. It looks like they tended to break.
And the reason they probably vibrated more is larger flat tiles are not going to tightly fit a curved surface. They could have changed their tile manufacturing process to make them conformally curved, but the simpler solution was to just make them smaller.This might have been covered before (very long thread), but I am wondering why they are not using bigger tiles, at least on the cylindrical section. Would seem like a lot less work for installation and might need less mounting points. Is it a problem with manufacturing them to a bigger size (e.g. more potential waste due to manufacturing faults)?They did. It looks like they tended to break.
Most of the smaller TPS patches on the earlier prototypes included larger tiles than the current "standard" tile. It stands to mention that a larger tile will be weaker unless it is made denser (i.e. heavier), have larger gaps between tiles and could be more sensitive to vibrations.
Maybe dummy tiles that will be replaced with the real thing? Makes sense that they might 3D print a unique tile before they make the real one, for instance.Or maybe a clear sign that SX knows the tile system is less than perfect and are trying different things. If these tiles stay on for launch maybe they've found a hard ceramic coating with high reflectance in visible and high emissivity in IR, like the paint on the LSS mockup.
Also, the larger the tile the greater the divergence from the curve of the OML and the more the pointy corners stick out begging for heat buildup.This might have been covered before (very long thread), but I am wondering why they are not using bigger tiles, at least on the cylindrical section. Would seem like a lot less work for installation and might need less mounting points. Is it a problem with manufacturing them to a bigger size (e.g. more potential waste due to manufacturing faults)?They did. It looks like they tended to break.
Most of the smaller TPS patches on the earlier prototypes included larger tiles than the current "standard" tile. It stands to mention that a larger tile will be weaker unless it is made denser (i.e. heavier), have larger gaps between tiles and could be more sensitive to vibrations.
And the reason they probably vibrated more is larger flat tiles are not going to tightly fit a curved surface. They could have changed their tile manufacturing process to make them conformally curved, but the simpler solution was to just make them smaller.
Also, the larger the tile the greater the divergence from the curve of the OML and the more the pointy corners stick out begging for heat buildup.This might have been covered before (very long thread), but I am wondering why they are not using bigger tiles, at least on the cylindrical section. Would seem like a lot less work for installation and might need less mounting points. Is it a problem with manufacturing them to a bigger size (e.g. more potential waste due to manufacturing faults)?They did. It looks like they tended to break.
Most of the smaller TPS patches on the earlier prototypes included larger tiles than the current "standard" tile. It stands to mention that a larger tile will be weaker unless it is made denser (i.e. heavier), have larger gaps between tiles and could be more sensitive to vibrations.
Also, the larger the tile the greater the divergence from the curve of the OML and the more the pointy corners stick out begging for heat buildup.This might have been covered before (very long thread), but I am wondering why they are not using bigger tiles, at least on the cylindrical section. Would seem like a lot less work for installation and might need less mounting points. Is it a problem with manufacturing them to a bigger size (e.g. more potential waste due to manufacturing faults)?They did. It looks like they tended to break.
Most of the smaller TPS patches on the earlier prototypes included larger tiles than the current "standard" tile. It stands to mention that a larger tile will be weaker unless it is made denser (i.e. heavier), have larger gaps between tiles and could be more sensitive to vibrations.
A larger tile could just be longer in the vertical dimension, which would not have the issue of curvature to deal with - in other words, a strip of heat tile instead of a hexagon. This would only work on the body of the Starship that is the same diameter (i.e. not the nose), but that is a lot of space to cover.
Also, the larger the tile the greater the divergence from the curve of the OML and the more the pointy corners stick out begging for heat buildup.Why not make them to fit the curvature?
Larger tiles need bigger gaps for thermal expansion.
Kind of like . . . scales? :)Larger tiles need bigger gaps for thermal expansion.
Or overlapping ends and edges.
Larger tiles, larger areas, larger forces, greater bending moments.And the reason they probably vibrated more is larger flat tiles are not going to tightly fit a curved surface. They could have changed their tile manufacturing process to make them conformally curved, but the simpler solution was to just make them smaller.
It's more likely (by Occam's Razor) that we're seeing a simple direct scaling effect: larger tiles have more mass, but they have the same number of attachment points. That means more stress per attachment point. Simple.
Just as an aside, do we have confirmation that the tiles are flat and not curved? Sorry if I missed it.
Larger tiles, larger areas, larger forces, greater bending moments.And the reason they probably vibrated more is larger flat tiles are not going to tightly fit a curved surface. They could have changed their tile manufacturing process to make them conformally curved, but the simpler solution was to just make them smaller.
It's more likely (by Occam's Razor) that we're seeing a simple direct scaling effect: larger tiles have more mass, but they have the same number of attachment points. That means more stress per attachment point. Simple.
Just as an aside, do we have confirmation that the tiles are flat and not curved? Sorry if I missed it.
Same thickness, more fragile.
Tiny tiles would be blocky and unlikely to break, but not a good choice for other reasons.
Kind of like . . . scales? :)Larger tiles need bigger gaps for thermal expansion.
Or overlapping ends and edges.
This is the first full try ala SX modus operandi of just good enough. If they need to do that they will. It's not that big a parts count issue on the cylinder but up on the ogive it might be a complexity they'd like to avoid. That said, there are custom curved tiles in the fin edges. They'll do whatever it takes.Also, the larger the tile the greater the divergence from the curve of the OML and the more the pointy corners stick out begging for heat buildup.Why not make them to fit the curvature?
There's that old bugaboo of swapping out overlapping tiles. If the bevel is mild and the pin short maybe there would be enough slack to lever one side up and pop the latch before the other side starts to bind. Make the bevel too mild and what's the point? Like everything else in this game, it's a balancing act.Kind of like . . . scales? :)Larger tiles need bigger gaps for thermal expansion.
Or overlapping ends and edges.
I would not be surprised if SpaceX has thought of what I'm thinking of and rejected it for good reasons, but what I was thinking of would be something like a 45 degree bevel that allows the bottom of the top tile to overlap the top of the bottom tile, but still leave room for heat expansion of the tile.
We don't see any overlap with the current tiles, so even a small amount of overlap could be an added bonus.
In order to tile the straight bodied part of the Starship, you'd need three separate versions of the tile:
1. A "spine" variant that would be placed in the bottom of the ship when it is falling through the atmosphere. This version would have 45 degree overlaps that stick out and over on the sides, an under slope at the top, and an under slope at the bottom.
2. A "Right side" variant would only be placed on the right side of the body from the "spine" variants, and would have under slope on the side towards the spine, and over slopes on the right side as the body curves "up" the side of the body.
3. Same as 2 above, but the left side variant.
It could be that SpaceX has rejected long tiles because of expansion issues or because they could break more. So consider this more of a thought experiment... :o
Kind of like . . . scales? :)Larger tiles need bigger gaps for thermal expansion.
Or overlapping ends and edges.
I would not be surprised if SpaceX has thought of what I'm thinking of and rejected it for good reasons, but what I was thinking of would be something like a 45 degree bevel that allows the bottom of the top tile to overlap the top of the bottom tile, but still leave room for heat expansion of the tile.
We don't see any overlap with the current tiles, so even a small amount of overlap could be an added bonus.
In order to tile the straight bodied part of the Starship, you'd need three separate versions of the tile:
1. A "spine" variant that would be placed in the bottom of the ship when it is falling through the atmosphere. This version would have 45 degree overlaps that stick out and over on the sides, an under slope at the top, and an under slope at the bottom.
2. A "Right side" variant would only be placed on the right side of the body from the "spine" variants, and would have under slope on the side towards the spine, and over slopes on the right side as the body curves "up" the side of the body.
3. Same as 2 above, but the left side variant.
It could be that SpaceX has rejected long tiles because of expansion issues or because they could break more. So consider this more of a thought experiment... :o
Or you could do a pull test like they did on the Space Shuttle. Requirement was just north of 100 lbs if I remember right.
1) insert tile, 2) check fit, 3) pull test, done.
John
Random thought.
It seems implicitly accepted by everyone that cracked tiles will have to be replaced.
But will they really ?
After all, the gaps between tiles are not filled with anything, and the cracks surely leave smaller gaps than that.
So if they see that cracked tiles remain decently attached, I am wondering if really they would require replacement.
Or you could do a pull test like they did on the Space Shuttle. Requirement was just north of 100 lbs if I remember right.
1) insert tile, 2) check fit, 3) pull test, done.
John
(thread from prototype discussion thread).
I'm sorry but I have to disagree John. In high volume manufacturing adding tests is almost never the correct solution. Elon has some good rants on this topic, and I spent the first 5 years of my career eliminating unneeded tests from a high volume electronics manufacturing line.
Unless the test can be integrated into an application tool that takes near zero additional time, adding a 10 second test to 10,000 tiles isn't the best solution when 7 tiles out of 10,000 failed.
The static fire test is the best QA method for that kind of failure rate.
The tiles are hand-applied, so not sure what kind of tool would be possible for making the tile application process faster while doing in-situ test. Perhaps a robot could do a higher quality job.
On repair after landing, a test tool for the repair would probably be a good idea, since there's probably no static fire to check the work.
They're still feeling their way through the problem. First find a general solution, then figure out how to automate it with minimal modification.Or you could do a pull test like they did on the Space Shuttle. Requirement was just north of 100 lbs if I remember right.
1) insert tile, 2) check fit, 3) pull test, done.
John
(thread from prototype discussion thread).
I'm sorry but I have to disagree John. In high volume manufacturing adding tests is almost never the correct solution. Elon has some good rants on this topic, and I spent the first 5 years of my career eliminating unneeded tests from a high volume electronics manufacturing line.
Unless the test can be integrated into an application tool that takes near zero additional time, adding a 10 second test to 10,000 tiles isn't the best solution when 7 tiles out of 10,000 failed.
The static fire test is the best QA method for that kind of failure rate.
The tiles are hand-applied, so not sure what kind of tool would be possible for making the tile application process faster while doing in-situ test. Perhaps a robot could do a higher quality job.
On repair after landing, a test tool for the repair would probably be a good idea, since there's probably no static fire to check the work.
Echo_Jex: There may be different inspection criteria for the prototypes in engineering development vs "rapidly reusable".
That suggests some overall context-setting that might be useful on this thread.
As we watch things shake out at Starbase, so to speak, just what are we witnessing? Beats me, really, but they don't seem to be terribly surprised at developments.
Would I be incorrect to presume that at the very least:
☼ Sx used continuously-adapting computer models to develop this tile design, informed by:
☼ stressing R&D installation of R&D samples on R&D mount attachments on a shake table, perhaps with some active substrate flexure,
☼ stressing R&D installation of R&D samples on R&D mount attachments in a hypersonic wind tunnel, perhaps with some active substrate flexure, plus
☼ things learned from actual flight of test materials (e.g. CRS-18)
The above would have been R&D materials and processes. What's at B.C. might represent qualification of production-grade tiles & production-grade installation, and perhaps not so much validation of the basic tile design. And yes, I'm also expecting that the entire life-cycle process for tiles will at some point be automated (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2264287#msg2264287).
A cracked tile could possibly leave the tile improperly supported. There is no redundancy in your attachment to the 3 pins.
I'm not sure that's correct.
Remember that the attachement points on the tile's side are linked together through a metallic frame that's encased in the tile.
So depending on where the crack is, there likely are cases where the tile is cracked, but where both halves are still attached to the frame, and thus, to the attachement mechanism.
I'm not sure that's correct.
Remember that the attachement points on the tile's side are linked together through a metallic frame that's encased in the tile.
So depending on where the crack is, there likely are cases where the tile is cracked, but where both halves are still attached to the frame, and thus, to the attachement mechanism.
Given that loads on the unsupported parts of the tile will generate torques along the y-channel supports, it's more likely that the cracks will be along the channels, rather than across them. That'll leave a chunk literally flapping in the breeze, which will likely carry it way in short order.
Folks, cracked tiles are bad. You can argue all you want about how often a missing tile is a catastrophic failure, but I'm pretty sure that the answer is going to be, "Often enough that you really don't want any." I'm pretty sure that engineering will continue until p(loss of tile) << p(loss of vehicle).
This doesn't necessarily mean that the first launch will be delayed, because getting this puppy to orbit is much, much more important than getting it back down from orbit. But I doubt that Starship will be considered reliably recoverable until missing tiles are very, very rare.
Yes, I agree. SS could withstand a few brocken tiles, but there is a reason because of which it haas a full heat shield and it doesn't lack a few tiles. The inspection that we saw months ago clearly showns that they wnat to find the cracked tiles. About S20 the most important thing for them like you say is to get it to orbit. I think that s21 and s22 will be the true test beds for the heat shield.
I'm not sure that's correct.
Remember that the attachement points on the tile's side are linked together through a metallic frame that's encased in the tile.
So depending on where the crack is, there likely are cases where the tile is cracked, but where both halves are still attached to the frame, and thus, to the attachement mechanism.
Given that loads on the unsupported parts of the tile will generate torques along the y-channel supports, it's more likely that the cracks will be along the channels, rather than across them. That'll leave a chunk literally flapping in the breeze, which will likely carry it way in short order.
Folks, cracked tiles are bad. You can argue all you want about how often a missing tile is a catastrophic failure, but I'm pretty sure that the answer is going to be, "Often enough that you really don't want any." I'm pretty sure that engineering will continue until p(loss of tile) << p(loss of vehicle).
This doesn't necessarily mean that the first launch will be delayed, because getting this puppy to orbit is much, much more important than getting it back down from orbit. But I doubt that Starship will be considered reliably recoverable until missing tiles are very, very rare.
Yes, I agree. SS could withstand a few brocken tiles, but there is a reason because of which it haas a full heat shield and it doesn't lack a few tiles. The inspection that we saw months ago clearly showns that they wnat to find the cracked tiles. About S20 the most important thing for them like you say is to get it to orbit. I think that s21 and s22 will be the true test beds for the heat shield.
I think Starship will generally survive TPS failures, but I do not think it will ever be rapidly reusable after a TPS failure, instead requiring at least repairs and possibly scrapping.That's also my gut feeling based on no particular expertise... it certainly has a lot higher chance of surviving a missing tile or two when it's made from stainless steel vs the shuttles aluminium frame but there's no way it would be getting rapidly re-flown afterwards, (even un-manned) as even if the steel didn't melt and lose integrity it could have been considerably weakened by the excessive heat etc... and if they can produce these things like a sausage in a sausage factory why would you want to risk re-flying a damaged one if there are several new ones waiting their turn ? In that case just be glad that it landed in one piece, study the damage to help improve the design and move on.
Since the goal is rapid reuse, they are doing, and need to do, everything that is reasonably possible to eliminate TPS failures.
but there's no way it would be getting rapidly re-flown afterwards, (even un-manned) as even if the steel didn't melt and lose integrity it could have been considerably weakened by the excessive heat etc
but there's no way it would be getting rapidly re-flown afterwards, (even un-manned) as even if the steel didn't melt and lose integrity it could have been considerably weakened by the excessive heat etc
But does the goal of rapid re-flight then potentially increase the likelihood of overlooking significant damage following return?
but there's no way it would be getting rapidly re-flown afterwards, (even un-manned) as even if the steel didn't melt and lose integrity it could have been considerably weakened by the excessive heat etc
But does the goal of rapid re-flight then potentially increase the likelihood of overlooking significant damage following return?
I wonder if you could embed strain gauges with passive RFIDs in each tile. I'll bet that a crack anywhere will change strain in easily-detectable ways.
Not sure if you could keep the RFID from cooking, though.
That said, I still think the ultimate answer is to make cracked tiles really, really rare.
This sounds like a good job for first pass machine vision automatic inspection, maybe via drones for close up views. Flag anything off nominal looking for human review. Missing, damaged or relocated tiles should be fairly easy to quantify.
If the perpendicular flows are very strong, then they would act like a blow torch straight onto the tiles. That wouldn't bode well for skin integrity even in the case of just a single tile loss.Two and a half years ago, SpaceX were literally conducting that head-on blowtorch test on tile sections: https://twitter.com/elonmusk/status/1107378575924035584
Echo_Jex: There may be different inspection criteria for the prototypes in engineering development vs "rapidly reusable".
That suggests some overall context-setting that might be useful on this thread.
As we watch things shake out at Starbase, so to speak, just what are we witnessing? Beats me, really, but they don't seem to be terribly surprised at developments.
Would I be incorrect to presume that at the very least:
☼ Sx used continuously-adapting computer models to develop this tile design, informed by:
☼ stressing R&D installation of R&D samples on R&D mount attachments on a shake table, perhaps with some active substrate flexure,
☼ stressing R&D installation of R&D samples on R&D mount attachments in a hypersonic wind tunnel, perhaps with some active substrate flexure, plus
☼ things learned from actual flight of test materials (e.g. CRS-18)
The above would have been R&D materials and processes. What's at B.C. might represent qualification of production-grade tiles & production-grade installation, and perhaps not so much validation of the basic tile design. And yes, I'm also expecting that the entire life-cycle process for tiles will at some point be automated (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2264287#msg2264287).
I assume most of these analyses and tests has been done.
John
I'm sure SpaceX has been simulating the TPS in plasma flow to very great lengths. One of the important factors of those simulations would be the "granularity", or resolution, they have been able to achieve in the simulations.
I am pretty sure the simulations have informed the eventual choice of tile size acceptable for maintaining good shielding, even in the case of a tile loss.
As I see it, the strength of perpendicular versus parallel plasma flows (in relation to the tile surface) must have a great effect.
If the perpendicular flows are very strong, then they would act like a blow torch straight onto the tiles. That wouldn't bode well for skin integrity even in the case of just a single tile loss.
If the parallel plasma flows are much stronger and, in effect, overpower the perpendicular flows, then I could see them shielding an area where a tile has been lost.
Of course the strengths of perpendicular and parallel flows are very much dependent on where on the fuselage the tiles are located.
I'm sure SpaceX has been simulating the TPS in plasma flow to very great lengths. One of the important factors of those simulations would be the "granularity", or resolution, they have been able to achieve in the simulations.I believe they now use adaptive grids in the simulation where the resolution is variable, lower where there is little complexity and much higher where there is more complexity. This video explains it in some detail (13 mins in)
I am pretty sure the simulations have informed the eventual choice of tile size acceptable for maintaining good shielding, even in the case of a tile loss.
As I see it, the strength of perpendicular versus parallel plasma flows (in relation to the tile surface) must have a great effect.
If the perpendicular flows are very strong, then they would act like a blow torch straight onto the tiles. That wouldn't bode well for skin integrity even in the case of just a single tile loss.
If the parallel plasma flows are much stronger and, in effect, overpower the perpendicular flows, then I could see them shielding an area where a tile has been lost.
Of course the strengths of perpendicular and parallel flows are very much dependent on where on the fuselage the tiles are located.
I'm looking at this from a photography point of view. And a lifelong infatuation with astronomy where I've learned that all EMR behaves roughly the same if the unit of measure is a wavelength.I'm sure SpaceX has been simulating the TPS in plasma flow to very great lengths. One of the important factors of those simulations would be the "granularity", or resolution, they have been able to achieve in the simulations.
I am pretty sure the simulations have informed the eventual choice of tile size acceptable for maintaining good shielding, even in the case of a tile loss.
As I see it, the strength of perpendicular versus parallel plasma flows (in relation to the tile surface) must have a great effect.
If the perpendicular flows are very strong, then they would act like a blow torch straight onto the tiles. That wouldn't bode well for skin integrity even in the case of just a single tile loss.
If the parallel plasma flows are much stronger and, in effect, overpower the perpendicular flows, then I could see them shielding an area where a tile has been lost.
Of course the strengths of perpendicular and parallel flows are very much dependent on where on the fuselage the tiles are located.
More resolution in FLIR, might be a good thing. some modification of said gear...something that puts the camera proper in it's sweet zone of sensitivity. This, with regard to frame rate, flow rate and being on a shaker of some sort. Being on a shaker is where an improved frame rate might really be helpful. This one seems to be headed in the right direction but the temperature range is not quite high enough.
(https://www.flir.ca/discover/instruments/oil-petrochemical/a-flir-infrared-furnace-camera-for-high-temp-industrial-applications-watches-hydro-reformers-at-german-bayernoil-refinery-complex/)
The next problem is that any additional reflecting layer that is designed to be in front of the camera proper, to get the camera into it's sweet spot..that layer would quite likely require some form of temperature control on it's own, as thermals in the reflector would probably slow the temporal resolution. Maybe a liquid cooled lens stack. A coated transparent ceramic, maybe. Even high speed air flow (across the ceramic reflector) might be clean enough to do the trick, to keep that temporal resolution up. Perhaps someone has solved this potential problem already.
To do this sort of temporal resolution test, if it is easy (enough) to arrive at... and then find out if it has any use. There might be useful data in there. Who knows. Again, considering the issue of number of tiles and importance of said tiles, and so on... more varied data might be better, at least at this discovery end of the process.
EG, it might turn out that cooling the edges of a ceramic reflector is the best way to keep the given sheet cooled, without having thermal flutter occur in the lens proper. Where air and fluid would possibly cause enough random fluctuations to make fine resolution and fine temporal resolution (as a related pair) attempts be pretty well useless.
A way around that might be edge cooling, where the thermal changes have a more defined, less random propagation pattern. Then, add in a modifier in the resulting data, where it is akin to optical color shift correction. This is used to correct for VR lenses, to get rid of color aberration across the viewed image. A similar thermal correction might be useful. To only be looked at, if a problem arises, but one should probably have a back up plan for the back up plan, one that looks at potential issues.
Anyway, it's just a quickly rambled thought experiment at this point. A few seconds of thought put into it is probably worth the time it takes.
Doubling the fundamental frame rate limit of FLIR is 'almost' easy...as this can be done via using two cameras with tightly controlled frame capture sequencing and all the rest that follows. Mapping the individual cameras sensitivities out on a calibration set up... and then the resulting correction file for when the cameras are paired. Does the possible loss in that calibration/pairing process warrant the attempt? One might borrow/mine from the 3D camera fields of endeavor for the basic hardware design. Additionally, via the data package... sensitivity across thermals goes up just a hair, it comes along for the ride, if it properly handled, it might be useful. Who knows. Something additional to look at, for future extrapolation. One can half step the thermals as well, via a second thermal filter on the one camera in the given paring. Write it down in the notes.
(my job, for about the past 20 plus years... has principally been about prototype initiation and proofing. A place where the need for custom design and gear is desirable. Hence these sorts of rambles. They are semi-educated guesses, rife with cross insemination, steeped in the lore of actually doing it, every dang day, all day long. Where my inherent over the top ADHD and semi OCD comes in very handy)
Whoops..I also see a potential way to quadruple the resolution of the camera..but that's another ramble...
there are plasma wind tunnels for doing testing toJust some questions on my end but how would a static fire affect those tiles? Something specific to square on square contact area that makes them more sensitive to shaking? Temperature difference from nearer-to-tank to farther-from-tank causing issues? Both those issues don't seem too stressful compared to the load they're supposed to handle.
https://www.livescience.com/plasma-tunnel-melts-satellite-model.html
also some tiles being replaced on sn20 near wing a few day ago, the cause might be the static fire but really cause is not known,
I'm asusming related to static fire, so the tally for tile loss goes up quite a bit.....yup its all assumption.
Resonances.there are plasma wind tunnels for doing testing toJust some questions on my end but how would a static fire affect those tiles? Something specific to square on square contact area that makes them more sensitive to shaking? Temperature difference from nearer-to-tank to farther-from-tank causing issues? Both those issues don't seem too stressful compared to the load they're supposed to handle.
https://www.livescience.com/plasma-tunnel-melts-satellite-model.html
also some tiles being replaced on sn20 near wing a few day ago, the cause might be the static fire but really cause is not known,
I'm asusming related to static fire, so the tally for tile loss goes up quite a bit.....yup its all assumption.
Resonances.there are plasma wind tunnels for doing testing toJust some questions on my end but how would a static fire affect those tiles? Something specific to square on square contact area that makes them more sensitive to shaking? Temperature difference from nearer-to-tank to farther-from-tank causing issues? Both those issues don't seem too stressful compared to the load they're supposed to handle.
https://www.livescience.com/plasma-tunnel-melts-satellite-model.html
also some tiles being replaced on sn20 near wing a few day ago, the cause might be the static fire but really cause is not known,
I'm asusming related to static fire, so the tally for tile loss goes up quite a bit.....yup its all assumption.
Think of Starship as a guitar string and the tile is stuck on.
At a node, not much movement, between nodes, there is a lot of movement.
I meant specifically with the tiles in that specific area, as in why would they be replacing a large area on that flat surface as opposed to on the barrel sections?
S21 aft section was moved to the front of the mid bay.
Is there any reason they'd want larger tiles on this area specificallyWidth of the band might be a reason
Good question. By the way, am I the only one, having the impression that the tiles are applied with a higher accuracy than before?S21 aft section was moved to the front of the mid bay.
S21's aft section has larger tiles on the bulkhead reinforcement band than on the rest of the section (see attached image from the quoted post). For comparison, the same section on S20 uses the usual smaller tiles. Is there any reason they'd want larger tiles on this area specifically, or might they be thinking of switching to larger tiles and are gathering data with this smaller section first? Could it have something to do with the lack of thermal blanket on the reinforcement band?
I suspect it has something to do with the tiles being glued on rather than pinned on.S21 aft section was moved to the front of the mid bay.
S21's aft section has larger tiles on the bulkhead reinforcement band than on the rest of the section (see attached image from the quoted post). For comparison, the same section on S20 uses the usual smaller tiles. Is there any reason they'd want larger tiles on this area specifically, or might they be thinking of switching to larger tiles and are gathering data with this smaller section first? Could it have something to do with the lack of thermal blanket on the reinforcement band?
... By the way, am I the only one, having the impression that the tiles are applied with a higher accuracy than before?
Is that true for the nose cone, too? The barrel section is more uniform than the nose cone for SN20, too.... By the way, am I the only one, having the impression that the tiles are applied with a higher accuracy than before?
No, I have that impression too. The tiles seem more consistently fitted and the edges seem better aligned into a smooth surface.
... The tiles seem more consistently fitted and the edges seem better aligned into a smooth surface.Is that true for the nose cone, too? The barrel section is more uniform than the nose cone for SN20, too.
I wonder how much more delay on the part of the FAA it would take to doom SN20 to lawn ornamentation duties and allow SN21 in on the first orbital attempt?... The tiles seem more consistently fitted and the edges seem better aligned into a smooth surface.Is that true for the nose cone, too? The barrel section is more uniform than the nose cone for SN20, too.
To my eye in the pictures I've seen, SN21 cone and barrel sections both have a more even, smooth appearance indicating less tile-to-tile variation in mounting, and thus forming a smoother skin. Not perfect, but a good step forward. YMMV, since I'm not sure we've had the best lighting angles to emphasize irregularities for SN21 yet.
The skin of the SS has noticeably improved with each build although the improvement curve has been flattening of late. No reason not to expect the tiles to follow the same path despite a chorus of "they're not doing it right." It's the SX way.... The tiles seem more consistently fitted and the edges seem better aligned into a smooth surface.Is that true for the nose cone, too? The barrel section is more uniform than the nose cone for SN20, too.
To my eye in the pictures I've seen, SN21 cone and barrel sections both have a more even, smooth appearance indicating less tile-to-tile variation in mounting, and thus forming a smoother skin. Not perfect, but a good step forward. YMMV, since I'm not sure we've had the best lighting angles to emphasize irregularities for SN21 yet.
I'll answer your question with a question. How long before SN21 is ready? They'll do it in a heartbeat if the timing works out.I wonder how much more delay on the part of the FAA it would take to doom SN20 to lawn ornamentation duties and allow SN21 in on the first orbital attempt?... The tiles seem more consistently fitted and the edges seem better aligned into a smooth surface.Is that true for the nose cone, too? The barrel section is more uniform than the nose cone for SN20, too.
To my eye in the pictures I've seen, SN21 cone and barrel sections both have a more even, smooth appearance indicating less tile-to-tile variation in mounting, and thus forming a smoother skin. Not perfect, but a good step forward. YMMV, since I'm not sure we've had the best lighting angles to emphasize irregularities for SN21 yet.
IMO SN21 will be ready long before the FAA are, so it seems likely that SN20 will soon be relegated to a static fire and GSE testing role. If it hasn't been already.I'll answer your question with a question. How long before SN21 is ready? They'll do it in a heartbeat if the timing works out.I wonder how much more delay on the part of the FAA it would take to doom SN20 to lawn ornamentation duties and allow SN21 in on the first orbital attempt?... The tiles seem more consistently fitted and the edges seem better aligned into a smooth surface.Is that true for the nose cone, too? The barrel section is more uniform than the nose cone for SN20, too.
To my eye in the pictures I've seen, SN21 cone and barrel sections both have a more even, smooth appearance indicating less tile-to-tile variation in mounting, and thus forming a smoother skin. Not perfect, but a good step forward. YMMV, since I'm not sure we've had the best lighting angles to emphasize irregularities for SN21 yet.
IMO SN21 will be ready long before the FAA are, so it seems likely that SN20 will soon be relegated to a static fire and GSE testing role. If it hasn't been already.
This is the first full try ala SX modus operandi of just good enough. If they need to do that they will. It's not that big a parts count issue on the cylinder but up on the ogive it might be a complexity they'd like to avoid. That said, there are custom curved tiles in the fin edges. They'll do whatever it takes.Also, the larger the tile the greater the divergence from the curve of the OML and the more the pointy corners stick out begging for heat buildup.Why not make them to fit the curvature?
Why not make them to fit the curvature?Currently (as per the FDEP report) tiles are milled to final size and shape on a router (cheap and fast, potentially large working volume for multiple tiles processed in parallel). Curved tiles would need a 5-axis CNC (more expensive, slower, more complex fixturing). If the flat tiles are adequate, curved tiles being 'better' is not worth the cost and time expenditure.
Or maybe add three RVacs to the three outer SL's. Yeah, a major thrust dome and plumbing redesign but as per speculation, something maybe being looked at. Big advantages for the meat haulers. If they're hung up on regulatory, it would keep the game moving.IMO SN21 will be ready long before the FAA are, so it seems likely that SN20 will soon be relegated to a static fire and GSE testing role. If it hasn't been already.
They could also get a non-SuperHeavy launch license pretty easily, fill it as full as they can while still having an adequate T/W to launch with just the sea-level engines (I get about 160t of prop for T/W=1.2), and get some decent suborbital reentry data by launching it out to sea. SWAGging at gravity losses, I get a burnout speed of something like 2200m/s. Not exactly an orbital reentry, but fast enough to find out if the CFD models are roughly correct, and to see how many tiles fall off.
Update: Anybody know the details of the mounting of the RVacs? If you can swap them out for RSLs without having to re-engineer the entire thrust structure, then you can load 960t of prop and expend 7450m/s of delta-v with a launch T/W=1.3. That's probably good for an entry speed of 6800m/s. That'll get you some pretty serious data.
SX will probably do a lot more tile customizing but given the culture, they've got to give the flat ones a try. Easing up to just good enough instead of dropping down from over engineered.This is the first full try ala SX modus operandi of just good enough. If they need to do that they will. It's not that big a parts count issue on the cylinder but up on the ogive it might be a complexity they'd like to avoid. That said, there are custom curved tiles in the fin edges. They'll do whatever it takes.Also, the larger the tile the greater the divergence from the curve of the OML and the more the pointy corners stick out begging for heat buildup.Why not make them to fit the curvature?
Even if they used the exact same (single-curved) tiles on the ogive, the overall curvature would still be less wrong than using flat tiles.
So again I ask, why not make the tiles fit the curvature? ???
Is it just so the body flaps (which are flat) can share a common tile SKU with the body/ogive tiles? Or is it the additional manufacturing complexity of making slightly curved tiles? Or is it just that SpaceX hasn't reached that stage yet?
Why not make them to fit the curvature?Currently (as per the FDEP report) tiles are milled to final size and shape on a router (cheap and fast, potentially large working volume for multiple tiles processed in parallel). Curved tiles would need a 5-axis CNC (more expensive, slower, more complex fixturing). If the flat tiles are adequate, curved tiles being 'better' is not worth the cost and time expenditure.
The tiles are shaped to the desired form using a router.
Why not make them to fit the curvature?Currently (as per the FDEP report) tiles are milled to final size and shape on a router (cheap and fast, potentially large working volume for multiple tiles processed in parallel). Curved tiles would need a 5-axis CNC (more expensive, slower, more complex fixturing). If the flat tiles are adequate, curved tiles being 'better' is not worth the cost and time expenditure.
It says (https://forum.nasaspaceflight.com/index.php?topic=48412.msg2162595#msg2162595)QuoteThe tiles are shaped to the desired form using a router.
A 5-axis CNC router is also a "router," so it's not clear that this is actually a contradiction.
I find it highly unlikely that SpaceX is using a manual (non-CNC) router for manufacturing the tiles.
Thus far we have 5 votes for "manufacturing complexity" and 4 votes for "not there yet." ??? 8)
Yes and they have a much better grasp of what's needed than we do. I (and probably others) made invalid assumptions about the tiles right from early on. My suggestion that a different tile would be needed for each layer of the nose cone was wrong because I had assumed no long straight lines were allowed between tiles. But long straight lines are allowed between tiles as long as they run circumferentially and not longitudinally. This allows them to get a much better fit with just 3 primary tile types and their corresponding half tiles.SX will probably do a lot more tile customizing but given the culture, they've got to give the flat ones a try. Easing up to just good enough instead of dropping down from over engineered.This is the first full try ala SX modus operandi of just good enough. If they need to do that they will. It's not that big a parts count issue on the cylinder but up on the ogive it might be a complexity they'd like to avoid. That said, there are custom curved tiles in the fin edges. They'll do whatever it takes.Also, the larger the tile the greater the divergence from the curve of the OML and the more the pointy corners stick out begging for heat buildup.Why not make them to fit the curvature?
Even if they used the exact same (single-curved) tiles on the ogive, the overall curvature would still be less wrong than using flat tiles.
So again I ask, why not make the tiles fit the curvature? ???
Is it just so the body flaps (which are flat) can share a common tile SKU with the body/ogive tiles? Or is it the additional manufacturing complexity of making slightly curved tiles? Or is it just that SpaceX hasn't reached that stage yet?
I have been wondering why the nosecone in particular requires glued on tiles ( red rtv silicone as glue?), anyhow scott manley put up a pic of a mach 20 wind tunnel test from the 1970s showing shock wave, and can be clearly seen the high temp shock wave remains very close to the nosecone area, and gradually gets further away from the craft as you go down the length of the craft, same shoud apply to sn20.How relevant is this Shuttle test to Starship? Starship does not have big wings. I thought it would just present its windward side to the direction of travel instead of a nose-up attitude.
Also next static fire, I think we might see some more tile shedding, will find out soon enough.
Looks like the Ship 20 heat shield did pretty well during the full static fire, losing perhaps two dozen tiles? We might see more when we have closer imaging, but seems unlikely it will be a lot more.
I have been wondering why the nosecone in particular requires glued on tiles ( red rtv silicone as glue?), anyhow scott manley put up a pic of a mach 20 wind tunnel test from the 1970s showing shock wave, and can be clearly seen the high temp shock wave remains very close to the nosecone area, and gradually gets further away from the craft as you go down the length of the craft, same shoud apply to sn20.How relevant is this Shuttle test to Starship? Starship does not have big wings. I thought it would just present its windward side to the direction of travel instead of a nose-up attitude.
Also next static fire, I think we might see some more tile shedding, will find out soon enough.
Very. Starship is going to enter at a higher angle of attack than Shuttle's 40 degrees, but not by much. It certainly won't be broadside (90 degrees AoA) because they it would not generate any lift, and it needs lift.
I have been wondering why the nosecone in particular requires glued on tiles ( red rtv silicone as glue?), anyhow scott manley put up a pic of a mach 20 wind tunnel test from the 1970s showing shock wave, and can be clearly seen the high temp shock wave remains very close to the nosecone area, and gradually gets further away from the craft as you go down the length of the craft, same shoud apply to sn20.
Also next static fire, I think we might see some more tile shedding, will find out soon enough.
I have been wondering why the nosecone in particular requires glued on tiles ( red rtv silicone as glue?), anyhow scott manley put up a pic of a mach 20 wind tunnel test from the 1970s showing shock wave, and can be clearly seen the high temp shock wave remains very close to the nosecone area, and gradually gets further away from the craft as you go down the length of the craft, same shoud apply to sn20.
Also next static fire, I think we might see some more tile shedding, will find out soon enough.
I have been wondering why the nosecone in particular requires glued on tiles ( red rtv silicone as glue?), anyhow scott manley put up a pic of a mach 20 wind tunnel test from the 1970s showing shock wave, and can be clearly seen the high temp shock wave remains very close to the nosecone area, and gradually gets further away from the craft as you go down the length of the craft, same shoud apply to sn20.
Also next static fire, I think we might see some more tile shedding, will find out soon enough.
There's a quick-and-dirty formula for heating rate (in W/m²) that goes:
q̇ = 1.83E-4v³√(⍴/rnose)
Where v is the current speed, ⍴ is the atmospheric density, and rnose is the nose radius, in meters.
Pro-tip: if you want the equation to be independent of the units used (ie the correct way in physics), then put the units where they belong: attached to the empirical constant.
If you're giving v above in m/s, then the equation is:
q̇ = (1.83E-4 kg1/2 m-1/2 ) v³√(⍴/rnose)
Pro-tip: if you want the equation to be independent of the units used (ie the correct way in physics), then put the units where they belong: attached to the empirical constant.
If you're giving v above in m/s, then the equation is:
q̇ = (1.83E-4 kg1/2 m-1/2 ) v³√(⍴/rnose)
q̇ is in W/m², so I think the coefficient is in kg½m-1, but I was willing to trust the source (which is an FAA tutorial, p. 4.1.7-322 (https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/aam/cami/library/online_libraries/aerospace_medicine/tutorial/media/iii.4.1.7_returning_from_space.pdf)). And yes, v is in m/s.
But none of that gets me any closer to figuring out how to estimate the nose radius.
Pro-tip: if you want the equation to be independent of the units used (ie the correct way in physics), then put the units where they belong: attached to the empirical constant.
If you're giving v above in m/s, then the equation is:
q̇ = (1.83E-4 kg1/2 m-1/2 ) v³√(⍴/rnose)
q̇ is in W/m², so I think the coefficient is in kg½m-1, but I was willing to trust the source (which is an FAA tutorial, p. 4.1.7-322 (https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/aam/cami/library/online_libraries/aerospace_medicine/tutorial/media/iii.4.1.7_returning_from_space.pdf)). And yes, v is in m/s.
But none of that gets me any closer to figuring out how to estimate the nose radius.
Can you estimate the curvature at any point on the ogive as a parabola? Wouldn't the focus of the parabola around the axis of symmetry then be your critical radius dimension?
Alternately, if you represent the ogive as a quadratic equation, taking the inverse of the derivative ( tangent line) at any give point gives you a line perpendicular to the ogive tangent at that point. You could numerically step your way outwards from the axis of symmetry & find the (x,y) coordinates where the adjacent linear equations intersect. Then the distance from your tangential point on the ogive the intersection of adjacent tangents is your radius. The radius will be calculated with pythagoreans theorem as the hypotenuse of the X,Y sides.
Why I dont like the pin/y bracket method of space x:
1. according to article above the tiles on the shuttle they need to be isolated from the vibrations etc, shuttle used isolation pads. The stainless pins are in effect going to transfer vibration to the tile via the Y brackets.
2. The y brackets are just set into the tile at manufacture, so vibration from bracket directly transferred to tile ( tiles are very easily cracked)
3. The stainless clips in effect will magnify the vibrations ( and if it happens you hit their resonate frequency they will act like little tuning forks).
4. The y brackets so far are not one connected piece, they are three separate pieces set into the slurry at manufacture. That would have to increase chance of cracking in my view.
5. The white blanket might perform some dampening of vibration of pins so thats a positive.
I dont think it will work in long term ( I could be wrong of course!), maybe increase tile density to decrease risk of cracking but weight issues there.
Not all that much. Part of the problem with the pointy end is that all the flow wraps around it. Because it's pointy it's getting radiative heating from all directions and in fairly equal proportions. On the cylinder input from 'adjacent' is from a bit further away. On the nose 'adjacent' still very close.I have been wondering why the nosecone in particular requires glued on tiles ( red rtv silicone as glue?), anyhow scott manley put up a pic of a mach 20 wind tunnel test from the 1970s showing shock wave, and can be clearly seen the high temp shock wave remains very close to the nosecone area, and gradually gets further away from the craft as you go down the length of the craft, same shoud apply to sn20.
Also next static fire, I think we might see some more tile shedding, will find out soon enough.
Remember though, the Space Shuttle entered at a much more nose down angle than Starship will. How much of the bow shock being close to the nose cone is due to the tight curvature, and how much is due to it being the first bit of the space shuttle to hit the air. A blunt reentry capsule shape pushing its bow shock away from it suggests strongly that Starship's much more belly first entry will push the bow shock much further from the nose.
Oh, and of course SpaceX has tested all thinkable issues relating to vibration. That goes without saying. Let's keep the Dunning-Kruger effect in mind... https://en.wikipedia.org/w/index.php?title=Dunning%E2%80%93Kruger_effect&oldid=1053909068
An unexpected vibration can fail a part in very short order. Identification of all possible vibration modes is nearly impossible for a complex design. You will most likely miss a few. Testing, inspection, and analysis is almost always needed to track down unexpected vibration modes. The good news is that there are numerous minor fixes which can usually deal with them once they are identified.Completely agree. Solutions such as a slight increase in the gap clearances on tiles in certain locations to allow for greater freedom of movement. Or slightly increased underlayment blanket thickness to provide more damping (and doesn't change overall mass if you increase the loft of the material). Maybe even a small geometry change to the tile retention clips to increase clamping force, trading on the risk of increased installation damage. These are all production tolerances that may need adjustment as testing illustrates the weak points.
John
Did Shuttle ever lose tiles on main engine test? Did it lose any tiles on lift off?
Did Shuttle ever lose tiles on main engine test? Did it lose any tiles on lift off?
Columbia lost more than 2000 tiles while just being ferried before the first flight.
Over 700 lost or damaged tiles on STS-27.
8-10 tiles lost or damaged on STS-134.
This issue was never fully resolved throughout the entire life of the Shuttle and I can't verify this but one report stated that loose tiles, cracked tiles, broken tiles, abraded tiles or missing tiles were part of every shuttle flight. Lockheed and NASA had decades to find a solution to the tile problem, but they were still unsuccessful. For Starship, color me wary, but optimistic.
... SS may have a resonance challenge for the TPS to overcome and the elasticity of the vehicle on entry is another one even if tank pressure is not lost... YMMV
A bit more exciting than using my old slide rule at least! ;D... SS may have a resonance challenge for the TPS to overcome and the elasticity of the vehicle on entry is another one even if tank pressure is not lost... YMMV
Only one way to find out. Light that candle! ;D
Which SpaceX have done, on multiple static fires and flights, at multiple scales (from small tile patches to whole ring spans to now full coverage). Even Starhopper had a tile patch, so the tile and tile attachment design has been iterating with in-flight testing for over two years now.... SS may have a resonance challenge for the TPS to overcome and the elasticity of the vehicle on entry is another one even if tank pressure is not lost... YMMV
Only one way to find out. Light that candle! ;D
Iterating lightly, and only really meaningfully in the latest full coverage tests where reactions in more than 1-way curved surfaces in locations with a great variety of outside factors and potential corelations were tested.Which SpaceX have done, on multiple static fires and flights, at multiple scales (from small tile patches to whole ring spans to now full coverage). Even Starhopper had a tile patch, so the tile and tile attachment design has been iterating with in-flight testing for over two years now.... SS may have a resonance challenge for the TPS to overcome and the elasticity of the vehicle on entry is another one even if tank pressure is not lost... YMMV
Only one way to find out. Light that candle! ;D
We've gone from the 'bolt through' tiles on Starshopper, through multiple different mounting mechanism (both mechanical and adhesive) with varying backing thickness/presence, varying presence/lack of gap-fillers, etc, various sizes of tiles, plus at least one internal tile frame change. A lot of iteration has already occurred before SpaceX even decided to start increasing the patch size.Iterating lightly, and only really meaningfully in the latest full coverage testsWhich SpaceX have done, on multiple static fires and flights, at multiple scales (from small tile patches to whole ring spans to now full coverage). Even Starhopper had a tile patch, so the tile and tile attachment design has been iterating with in-flight testing for over two years now.... SS may have a resonance challenge for the TPS to overcome and the elasticity of the vehicle on entry is another one even if tank pressure is not lost... YMMV
Only one way to find out. Light that candle! ;D
I suspect SpaceX will go to at least partly metal tiles eventually, as Elon suggested, altho they might fly orbital for a while with ceramic.Metal tiles would require a lower ballistic coefficient to reduce peak entry temperatures to around 1000C. So the “Dragon Wing” design with large wings spanning the gap between the forward and aft flaps and extending the overall Starship width to about 25m. The larger tile area and higher mass of wings and the metal tiles would lead to a significant loss of payload.
Yes I know all this thank you. I stated from the onset a couple more years ago that the TPS was going to be a 'long pole" for this SS design. I just don't post on here much anymore because of all the hand-waving. The other NSF ol' timers will know what I mean...We've gone from the 'bolt through' tiles on Starshopper, through multiple different mounting mechanism (both mechanical and adhesive) with varying backing thickness/presence, varying presence/lack of gap-fillers, etc, various sizes of tiles, plus at least one internal tile frame change. A lot of iteration has already occurred before SpaceX even decided to start increasing the patch size.Iterating lightly, and only really meaningfully in the latest full coverage testsWhich SpaceX have done, on multiple static fires and flights, at multiple scales (from small tile patches to whole ring spans to now full coverage). Even Starhopper had a tile patch, so the tile and tile attachment design has been iterating with in-flight testing for over two years now.... SS may have a resonance challenge for the TPS to overcome and the elasticity of the vehicle on entry is another one even if tank pressure is not lost... YMMV
Only one way to find out. Light that candle! ;D
The chemically adhered tiles at least were already a pretty high TRL (9) due to decades of operational use on STS, as is the tile composition and manufacture. The new parts are the mechanical mounting and the embedding of that mount inside the tile.
Is this where we start entertaining those weird double-fuselage extra wide Starships again? Those were fun.I suspect SpaceX will go to at least partly metal tiles eventually, as Elon suggested, altho they might fly orbital for a while with ceramic.Metal tiles would require a lower ballistic coefficient to reduce peak entry temperatures to around 1000C. So the “Dragon Wing” design with large wings spanning the gap between the forward and aft flaps and extending the overall Starship width to about 25m. The larger tile area and higher mass of wings and the metal tiles would lead to a significant loss of payload.
So what could that be?Dust. Everything on site will end up covered in it.
Just curious what happened to elons original plan of transpiration cooling? And why did they decide to go with tiles?https://twitter.com/elonmusk/status/1107376856175513600
And If they did use transpiration cooling would the leidenfrost effect apply?
Maybe another mechanism. Speed of sound in stainless would be higher than in air. Maybe a high frequency vibration that loads into the air and creates a local shock. In humid air a shock will look vapor like. I've seen it in pics of aircraft and live in person from the air watching expanding shock domes emitting from detonations.So what could that be?Dust. Everything on site will end up covered in it.
A minor procedure note:
On Ship 21 we see that the majority of tiles have a small 'OK' written on their apex. In the latest NSF video we see a few tiles being drilled out and replaced. The replacement tiles installed already have this 'OK' marking, so that marking is an indicator of a pre-install inspection rather than a post-install inspection. This should be of interest to those estimating post-install inspection coverage as we saw with Ship 20.
I happened across this slide-deck for a course:Yeah, I remember that exact presentation. Super helpful!
https://tfaws.nasa.gov/TFAWS12/Proceedings/Aerothermodynamics%20Course.pdf (https://tfaws.nasa.gov/TFAWS12/Proceedings/Aerothermodynamics%20Course.pdf)
It's very interesting but I don't have time to look at the detail. I learned a good bit just by scanning through the slides.
I happened across this slide-deck for a course:WOW! This is the slide deck for a whole course, so the time to actually assimilate it would be weeks. However, it really brings home how complicated TPS can get. One thing to learn quickly: re-entry vehicles are "blunt", not "pointy", for a reason: to generate a big shockwave that moves away from the vehicle as much as quickly as possible. This shockwave carries away almost all of the energy, and the TPS must handle the rest. Oversimplifying, the leading part of the vehicle is called the "nose" and the "nose diameter" is a fundamental parameter. Thus, the "nose" of a circular capsule (Orion, Dragon, Apollo) is the bottom part that is covered by the heat shield. The "nose" of a vehicle that is not radially symmetric about its velocity vector (Shuttle, Starship) is complicated, and is not simply the pointy front part. The "nose diameter" varies across the vehicle. Still oversimplifying, the "diameter" at a point is the diameter of the section of a sphere that approximates the curvature of the surface at that point. And that's just in the first few slides.
https://tfaws.nasa.gov/TFAWS12/Proceedings/Aerothermodynamics%20Course.pdf (https://tfaws.nasa.gov/TFAWS12/Proceedings/Aerothermodynamics%20Course.pdf)
It's very interesting but I don't have time to look at the detail. I learned a good bit just by scanning through the slides.
I hope they try those stainless heatshield tiles they showed before. Those shouldn’t have the brittleness problems. Might still have to use Shuttle-like ceramic tiles for stuff with sharper radiuses like near aero surfaces, but it’s still a big potential improvement.
NASA had been developing Inconel heatshield tiles for X-33/Venturestar, but certain grades of stainless are essentially just as good as Inconel but an order of magnitude cheaper.
(This comparison is for thermocouple sheath use temperature, but I think it is a reasonably good comparison.)
I hope they try those stainless heatshield tiles they showed before. Those shouldn’t have the brittleness problems. Might still have to use Shuttle-like ceramic tiles for stuff with sharper radiuses like near aero surfaces, but it’s still a big potential improvement.
NASA had been developing Inconel heatshield tiles for X-33/Venturestar, but certain grades of stainless are essentially just as good as Inconel but an order of magnitude cheaper.
(This comparison is for thermocouple sheath use temperature, but I think it is a reasonably good comparison.)
I hope they try those stainless heatshield tiles they showed before. Those shouldn’t have the brittleness problems. Might still have to use Shuttle-like ceramic tiles for stuff with sharper radiuses like near aero surfaces, but it’s still a big potential improvement.You got me thinking. Always dangerous. What do you think of the tiles loosing the vitreous surface and gaining stainless? Thermal expansion would dictate they be separate pieces. Put the bayonet on the back of the stainless and the socket on the skin. Run passthrough holes in the ceramic. Or some variation. Tricky details but the outer surface won't crack from MMOD. It also puts the ceramic in compression where it has its best strength.
NASA had been developing Inconel heatshield tiles for X-33/Venturestar, but certain grades of stainless are essentially just as good as Inconel but an order of magnitude cheaper.
(This comparison is for thermocouple sheath use temperature, but I think it is a reasonably good comparison.)
Just a thought regarding the white mist during static fire.
The tiles are some form of silicon, silicon can be water absorbent ( hydrophyllic), I remember reading somewhere the shuttle tiles were coated to stop water infiltration ( not the black borosilcate coating, but another coating for the white part not covered by black). If the rear of the tiles is not coated to stop water absorbtion, it might make the rear part prone to water absorption and might be possible the white mist ( thinking of the flaps here) is inner most layer of tile being a mix of water and silicone shaking loose.
anyhow it seems the ship is trying to say I can make a misty coating to protect myself during re-entry.
I hope they try those stainless heatshield tiles they showed before. Those shouldn’t have the brittleness problems. Might still have to use Shuttle-like ceramic tiles for stuff with sharper radiuses like near aero surfaces, but it’s still a big potential improvement.
NASA had been developing Inconel heatshield tiles for X-33/Venturestar, but certain grades of stainless are essentially just as good as Inconel but an order of magnitude cheaper.
(This comparison is for thermocouple sheath use temperature, but I think it is a reasonably good comparison.)
I hope they try those stainless heatshield tiles they showed before. Those shouldn’t have the brittleness problems. Might still have to use Shuttle-like ceramic tiles for stuff with sharper radiuses like near aero surfaces, but it’s still a big potential improvement.
NASA had been developing Inconel heatshield tiles for X-33/Venturestar, but certain grades of stainless are essentially just as good as Inconel but an order of magnitude cheaper.
(This comparison is for thermocouple sheath use temperature, but I think it is a reasonably good comparison.)
Just a thought regarding the white mist during static fire.
The tiles are some form of silicon, silicon can be water absorbent ( hydrophyllic), I remember reading somewhere the shuttle tiles were coated to stop water infiltration ( not the black borosilcate coating, but another coating for the white part not covered by black). If the rear of the tiles is not coated to stop water absorbtion, it might make the rear part prone to water absorption and might be possible the white mist ( thinking of the flaps here) is inner most layer of tile being a mix of water and silicone shaking loose.
anyhow it seems the ship is trying to say I can make a misty coating to protect myself during re-entry.
SpaceX use almost exactly same tiles as Shuttle, silica fibre and borosilicate coating. Main difference is Starship ones are thinner and use different waterproofing agent to stop water. Shuttle tiles was quite sensitive to water after multiple landings because it basically burned of waterproofing (i may not be right, I'm not sure), SpaceX may have more durable waterproofing as they changed one from shuttle era.
I hope they try those stainless heatshield tiles they showed before. Those shouldn’t have the brittleness problems. Might still have to use Shuttle-like ceramic tiles for stuff with sharper radiuses like near aero surfaces, but it’s still a big potential improvement.As others have noted, the shielding problem decreases pretty smoothly from the belly to the back. It’s obvious that the present system isn’t optimized for mass, because there’s a literal step function between shielded-like-the-belly and unshielded-like-the-back. So far as I can see, full-thickness tiles are adjacent to bare metal.
[...]
One way or another, thermal protection will taper off rather than cut off.
Because if bare metal is enough on one side of edge, then using full-thickness (= full-mass) worst-case shielding just 10 cm away is a waste. The only argument for an all-or-nothing transition at the edge is to make the shield uniform. [edit: as daavery argues above]One way or another, thermal protection will taper off rather than cut off.
Why?
Because if bare metal is enough on one side of edge, then using full-thickness (= full-mass) worst-case shielding just 10 cm away is a waste. The only argument for an all-or-nothing transition at the edge is to make the shield uniform. [edit: as daavery argues above]One way or another, thermal protection will taper off rather than cut off.
Why?
I can see this as a shortcut in a prototype, but not in an optimized production vehicle.
the whole idea is avoid the space shuttle and every tile being unique. using 1 design and thickness of tile allows for bulk manufacturing instead is 100s of unique tile versions
For something like a sphere (no sharp edges), heating is highest at the stagnation point, and for the same reason, heating is higher on the mid-line than on the sides of a cylinder entering at a high angle of attack.Because if bare metal is enough on one side of edge, then using full-thickness (= full-mass) worst-case shielding just 10 cm away is a waste. The only argument for an all-or-nothing transition at the edge is to make the shield uniform. [edit: as daavery argues above]One way or another, thermal protection will taper off rather than cut off.
Why?
I can see this as a shortcut in a prototype, but not in an optimized production vehicle.
So correct me if I am wrong. I am not a hypersonic flow specialist.
So at the midline we have supersonic flow that piles up and creates a large standoff/stagnation for the super hot gas.
At the edges it comes much closer to the edge because there is a lot less of the cushion to keep the flow away from the metal.
The flow might be cooler by the time it passes the edge and also near the edge their is not as much compression going on. So this would be the reverse of the standoff distance.
So you have 2 effects going on and I would bet the standoff/stagnation distance is the greater?
Has any attempt to use Alumina Al2O3-Al3O2 rather than SiO2 as the tile substrate? They use Alumina in high temperatures ( it is what sapphire is made of) in plasma furnaces and electronics?I have wondered about this myself, although it stands to mention that AETB tiles are 68% silica, 20% alumina and 12% aluminoborosilicate. I think the problem might be similar to that of ultra-high-temperature ceramics: the higher the temperature tolerance of your material, the harder it is to make into the composition and structure you want...
I agree that there can be some optimization of the heat shield edge but also think that will wait until they are optimizing for the last % of payload.the whole idea is avoid the space shuttle and every tile being unique. using 1 design and thickness of tile allows for bulk manufacturing instead is 100s of unique tile versions
Tapering the shield with a transition thickness or two isn’t anything like the “every tile is unique” Shuttle nightmare. There are already many kinds of tiles on the vehicle (look at the nose, look at the body flaps). Adding (for example) two more kinds could save a significant fraction of the heat shield mass, which would be well worth doing.
Substituting stainless surfaces where heating is lower would be a more substantial departure, but could be a big win for cost, robustness, and maintenance. Stainless on (for example) a thin Superwool insulation layer must be OK near the boundary where a bare stainless pressure vessel surface is OK.
Or am I missing something obvious?
IIRC, total mass of the tiles on Starship is estimated as around 9 metric tonnes (assuming density comaprable to the STS tiles that are almost identical to).I would make that more like “a few tons”. I think that SpaceX could manage to put different tiles on a few vertical bands down the body of the vehicle without being driven mad by the complexity, crates, packing, etc.
Thinning the tiles for optimum mass gains you maybe a few hundred kilograms. That is absolutely not worth the headache of adding extra tile types: manufacturing yet more variants, handling (e.g. crates and packing) for yet more variants, labelling for yet more variants (to avoid mixing with others that share the same peg layout) and/or adding a new peg layout to avoid mixing tiles, extra QC steps to make sure tile types are not mixed, etc.
SpaceX are optimising for cost and complexity, not mass.
Thanks, these are all well-grounded points.I agree that there can be some optimization of the heat shield edge but also think that will wait until they are optimizing for the last % of payload.the whole idea is avoid the space shuttle and every tile being unique. using 1 design and thickness of tile allows for bulk manufacturing instead is 100s of unique tile versions
Tapering the shield with a transition thickness or two isn’t anything like the “every tile is unique” Shuttle nightmare. There are already many kinds of tiles on the vehicle (look at the nose, look at the body flaps). Adding (for example) two more kinds could save a significant fraction of the heat shield mass, which would be well worth doing.
Substituting stainless surfaces where heating is lower would be a more substantial departure, but could be a big win for cost, robustness, and maintenance. Stainless on (for example) a thin Superwool insulation layer must be OK near the boundary where a bare stainless pressure vessel surface is OK.
Or am I missing something obvious?
A few things to consider:
There might be limitations regarding total heat conducted into the structure rather than maximum temperature (i.e. you still need the full insulation, just not the temperature tolerance).
The multi-cm edge of the heat shield might detach the flow and very rapidly decrease the transverse convective heat flow.
A thin sheet of stainless backed by insulation will have much lower thermal inertia and will only be able to shed heat by radiation on the outside surface so it will be much more sensitive to fluctuations in heat flow caused by for example local turbulence or shock interactions.
IIRC, total mass of the tiles on Starship is estimated as around 9 metric tonnes (assuming density comaprable to the STS tiles that are almost identical to).
Thinning the tiles for optimum mass gains you maybe a few hundred kilograms. That is absolutely not worth the headache of adding extra tile types: manufacturing yet more variants, handling (e.g. crates and packing) for yet more variants, labelling for yet more variants (to avoid mixing with others that share the same peg layout) and/or adding a new peg layout to avoid mixing tiles, extra QC steps to make sure tile types are not mixed, etc.
SpaceX are optimising for cost and complexity, not mass.
You just added less than 1% to the payload mass on a reusable launch (probably more like 0.7% : we'll see). Your cost to do this (design, manufacturing, turnaround/refurbishment) is X, Y, and Z. At $2 million/launch or even $10 million/launch, I don't see how you are going to recover your investment. You only recover it on the edge case where that extra tonne is actually needed for the mission.IIRC, total mass of the tiles on Starship is estimated as around 9 metric tonnes (assuming density comaprable to the STS tiles that are almost identical to).
Thinning the tiles for optimum mass gains you maybe a few hundred kilograms. That is absolutely not worth the headache of adding extra tile types: manufacturing yet more variants, handling (e.g. crates and packing) for yet more variants, labelling for yet more variants (to avoid mixing with others that share the same peg layout) and/or adding a new peg layout to avoid mixing tiles, extra QC steps to make sure tile types are not mixed, etc.
SpaceX are optimising for cost and complexity, not mass.
Assuming 9 tons for total TPS weight, if you can reduce the weight of 10% of the tiles by half, that's still 450 kg (992 lb).
That's not trivial.
Mass is still an extremely important aspect of Starship (as it is in all rockets). Every kg they can remove from Starship is a kg that can be added directly to payload.
You recover it every tanker refueling
You just added less than 1% to the payload mass on a reusable launch (probably more like 0.7% : we'll see). Your cost to do this (design, manufacturing, turnaround/refurbishment) is X, Y, and Z. At $2 million/launch or even $10 million/launch, I don't see how you are going to recover your investment. You only recover it on the edge case where that extra tonne is actually needed for the mission.IIRC, total mass of the tiles on Starship is estimated as around 9 metric tonnes (assuming density comaprable to the STS tiles that are almost identical to).
Thinning the tiles for optimum mass gains you maybe a few hundred kilograms. That is absolutely not worth the headache of adding extra tile types: manufacturing yet more variants, handling (e.g. crates and packing) for yet more variants, labelling for yet more variants (to avoid mixing with others that share the same peg layout) and/or adding a new peg layout to avoid mixing tiles, extra QC steps to make sure tile types are not mixed, etc.
SpaceX are optimising for cost and complexity, not mass.
Assuming 9 tons for total TPS weight, if you can reduce the weight of 10% of the tiles by half, that's still 450 kg (992 lb).
That's not trivial.
Mass is still an extremely important aspect of Starship (as it is in all rockets). Every kg they can remove from Starship is a kg that can be added directly to payload.
You recover it every tanker refueling or additional secondary payload or higher GTO orbit.Tanker refuelings are quantized so not quite, unless you have a depot. Even with a depot you are only saving at most 0.7% of the cost (or one launch for every 150 tanker launches, if you prefer). For the rideshare case you will not get the extra tonne of customer payload unless there are an effectively unlimited number of paying customers with satellites of variable sizes in the one-tonne range. If your demand is completely elastic with continuously-variable mass, you get at most 0.7% gain. I'm just not seeing it. Even for GEO: If the payload is just one tonne too big for me to get to GEO, I will need to refuel in LEO to deliver. But if it were two tonnes too big, I would need to refuel anyway, so it's still an edge case, and that edge will be there somewhere anyway, so we are still talking about 0.7% cost improvement on average.
You recover it every tanker refueling or additional secondary payload or higher GTO orbit.Tanker refuelings are quantized so not quite, unless you have a depot. Even with a depot you are only saving at most 0.7% of the cost (or one launch for every 150 tanker launches, if you prefer). For the rideshare case you will not get the extra tonne of customer payload unless there are an effectively unlimited number of paying customers with satellites of variable sizes in the one-tonne range. If your demand is completely elastic with continuously-variable mass, you get at most 0.7% gain. I'm just not seeing it. Even for GEO: If the payload is just one tonne too big for me to get to GEO, I will need to refuel in LEO to deliver. But if it were two tonnes too big, I would need to refuel anyway, so it's still an edge case, and that edge will be there somewhere anyway, so we are still talking about 0.7% cost improvement on average.
About GTO: using "Starship economics", does it ever make sense to launch to GTO? (It may: I am very much NOT a rocket scientist.) Might it not be cheaper and simpler to put the payload in a Starship, launch to LEO, refuel, deliver to GEO, and then come home? This assumes a depot or some sort of standard tanker system that provides propellant at $10 million/150 t = $67000/t, not a bespoke tanker for the GEO mission.
Not if you use a depot, which SpaceX is doing for Artemis.You recover it every tanker refueling
... but, just like DanClemmensen said, only if the mission you're refueling actually needs the additional single-digit tonnes of propellant.
Hey, I'm easy. If the launch cost is $10 million and the payload mass is somewhere near 150 t, then you will save on the order of $67,000 per launch for every tonne of dry mass you save, TPS or not. let's be generous and give you 100 launches: you save $6.7 million per tonne of dry mass saved. If that dry mass savings does not increase the cost of operations or refurbishment, you will only need to recoup the costs of design and manufacture associated with the mass savings. Note that Elon is aiming for $2 million/launch, not $10 million. Note also that this is tankers and other LEO-type missions, or you won't get the 100-mission reuse.You recover it every tanker refueling or additional secondary payload or higher GTO orbit.Tanker refuelings are quantized so not quite, unless you have a depot. Even with a depot you are only saving at most 0.7% of the cost (or one launch for every 150 tanker launches, if you prefer). For the rideshare case you will not get the extra tonne of customer payload unless there are an effectively unlimited number of paying customers with satellites of variable sizes in the one-tonne range. If your demand is completely elastic with continuously-variable mass, you get at most 0.7% gain. I'm just not seeing it. Even for GEO: If the payload is just one tonne too big for me to get to GEO, I will need to refuel in LEO to deliver. But if it were two tonnes too big, I would need to refuel anyway, so it's still an edge case, and that edge will be there somewhere anyway, so we are still talking about 0.7% cost improvement on average.
About GTO: using "Starship economics", does it ever make sense to launch to GTO? (It may: I am very much NOT a rocket scientist.) Might it not be cheaper and simpler to put the payload in a Starship, launch to LEO, refuel, deliver to GEO, and then come home? This assumes a depot or some sort of standard tanker system that provides propellant at $10 million/150 t = $67000/t, not a bespoke tanker for the GEO mission.
Keep in mind, this is assuming 9 tons for total TPS weight, and that you can only reduce the weight of 10% of the tiles by half.
Both heavily conservative estimates. It's probably true that the weight of a much higher percentage of tiles can be reduced significantly, depending on their location.
Also, the TPS is not the only place where mass savings can be made. Elon Musk originally said he hoped the final mass of Starship would be around 85 tons.
There's lots of room for mass optimization.
Every such incremental change looks insignificant by itself in isolation but to make the whole thing viable you need enough of them to compound together.Yep, they will analyze any mass saving they can. It's a question of priority. Right now, they need to get to orbit with Starlink satellites. I doubt they will consider any design change for the purpose of mass reduction if it affects the schedule. Clearly, any design change they are required to make for other reasons will take mass into account, so there may be some saving anyway. I would bet that Elon would trade an extra tonne of mass to shorten the schedule by a month. He would probably trade an extra ten tonnes for that month if he knew he would get it back in a year.
SpaceX isn’t gonna ignore a 1% mass savings if it’s staring them in the face.
This is the same Elon that deleted the legs and used the highest pressure rocket engine.That was then. This is now. We are within maybe 3 months of the first flight and Elon says SpaceX is at risk of bankruptcy if the cannot launch Starlink satellites. Deleting the legs in favor of chopsticks was not an apparent schedule risk when that decision was made: different engineering teams. The Raptor choice was also made a long time ago. The current schedule crisis is a short-term problem whose risk is caused by the surprise.
Another perspective: If the entire vehicle faced the relaxed thermal environment now seen on its sides, the heat shield design would make a different mass/cost/robustness trade-off, maybe not even using tiles. Since half the shielded area is in that kind of relaxed environment -- not stagnation point conditions -- then similar mass/cost/robustness improvements may still be worth pursuing. What if half the tile area could be replaced with a metal TPS solution?
But for now, it makes sense to design for the hard case and use the solution everywhere. Premature optimization is the root of much evil.
This is the same Elon that deleted the legs and used the highest pressure rocket engine.
Unless each tanker launch is just barely short of the propellant mass required by a few hundred kg and thus requires an additional launch to top-up that last ~1 ton, that doesn't actually save you much money at all. The per-launch costs will dwarf propellant costs for quite some time to come. You need to be operating at much higher flight rates and re-use counts before propellant cost starts to dominate launch costs, and at that point you have to consider whether that extra few hundred kg for edge-cause missions is worth retrofitting your fleet.Not if you use a depot, which SpaceX is doing for Artemis.You recover it every tanker refueling
... but, just like DanClemmensen said, only if the mission you're refueling actually needs the additional single-digit tonnes of propellant.
why not just cover the whole of the tiles with borosilicate?The borosilicate glass layer is a thin brittle crust over a stiff but frangible low density ceramic (a bit like an open-cell foam). SpaceX are also applying the pushpins via pressing them into the internal channels straight through the sintered fibre (just letting it crush out of the way rather than needing to mill or cast dedicated channels). The glass is vulnerable to cracks and microfractures, and whilst these can be tolerated for use as a heatshield (a hairline crack in the glass coating does not significantly affect its radiative properties) it will allow water ingress. Coating the entire tile and assuming that the glass coating will remain unfractured to provide the waterproofing is very likely to result in waterlogged tiles.
With regard tile waterproofing.The bulk material of the tile is a low density open "foam" of thin silica fibres. It needs to have some surface uncovered in order for the air inside to escape when exposed to the vacuum of space. Otherwise the surface layer would have to withstand a pressure difference of several atmospheres when the tile is heated. The insulating performance would also be negatively affected.
Thanks for the info posted and link to a pdf file. I had made a few assumptions on the waterproofing:
the borosilicate ( or similar) black coating already provided a waterproof surface, not the whole tile is coated with the black borosilcate. So only the rear or sides of tiles without borosilcate required waterproofing i.e. the white parts of the tiles which are not visible.
The pdf file posted previously says waterproofing was injected after shuttle flights, which suggests to me its only the
white parts which require waterproofing. If that is correct why not just cover the whole of the tiles with borosilicate?
Maybe it wouldn't be necessary to re-waterproof at all.
Not if you use a depot, which SpaceX is doing for Artemis.You recover it every tanker refueling
... but, just like DanClemmensen said, only if the mission you're refueling actually needs the additional single-digit tonnes of propellant.
This argument that small improvements aren’t worth it just doesn’t hold with reality.Not if you use a depot, which SpaceX is doing for Artemis.You recover it every tanker refueling
... but, just like DanClemmensen said, only if the mission you're refueling actually needs the additional single-digit tonnes of propellant.
Yes, it adds up within that refueling campaign (that's how it went from under 1 tonne to "single-digit tonnes"). But the vast majority of launches won't be.
Depots as a separate starship type would not be able to reenter- the insulation for long term cryo storage on orbit is different from reentry shielding. To be used for the next campaign, the depot will either need to be abandoned, or transfer to a more appropriate departure orbit. More fuel per launch helps to make the second option more viable.Not if you use a depot, which SpaceX is doing for Artemis.You recover it every tanker refueling
... but, just like DanClemmensen said, only if the mission you're refueling actually needs the additional single-digit tonnes of propellant.
Yes, it adds up within that refueling campaign (that's how it went from under 1 tonne to "single-digit tonnes"). But the vast majority of launches won't be.
Depots as a separate starship type would not be able to reenter- the insulation for long term cryo storage on orbit is different from reentry shielding. To be used for the next campaign, the depot will either need to be abandoned, or transfer to a more appropriate departure orbit. More fuel per launch helps to make the second option more viable.Not if you use a depot, which SpaceX is doing for Artemis.You recover it every tanker refueling
... but, just like DanClemmensen said, only if the mission you're refueling actually needs the additional single-digit tonnes of propellant.
Yes, it adds up within that refueling campaign (that's how it went from under 1 tonne to "single-digit tonnes"). But the vast majority of launches won't be.
I agree that for temporary use a tanker might be fine, but the heat shielding and the flaps add a lot of mass. In the long terma a different version might be better for the tanker, if the demand from customers is enough.Depots as a separate starship type would not be able to reenter- the insulation for long term cryo storage on orbit is different from reentry shielding. To be used for the next campaign, the depot will either need to be abandoned, or transfer to a more appropriate departure orbit. More fuel per launch helps to make the second option more viable.Not if you use a depot, which SpaceX is doing for Artemis.You recover it every tanker refueling
... but, just like DanClemmensen said, only if the mission you're refueling actually needs the additional single-digit tonnes of propellant.
Yes, it adds up within that refueling campaign (that's how it went from under 1 tonne to "single-digit tonnes"). But the vast majority of launches won't be.
I doubt there will be a separate variant for depots. A Tanker can be a temporary depot just fine.
Elon was asked 2 weeks ago about the challenge of long-term storage of cryogenics with all the boil off problems etc. and he said that there will be a Depot variant of Starship with multi-layer thermal insulation. (And let's not forget that this variant is also mentioned in the NASA's official documentation for HLS).
Starship going to Mars will only store propellant in the header tanks. There may be no way to hold larger amounts in the main tanks without insulation, so Depot might be a necessary variant to do refilling at all, not just a nice optimization for later.
I have no idea how big of a problem the boil off will be in shorter time, like a few days or a week, but if it's significant then Starship will need an insulated depot not just for Artemis and Mars, but even for many missions to orbits other than LEO that F9 and FH already can do.
I don't think anyone believes they will be able to do multiple Starship launches per day anytime soon, so even 2 refill launches could mean a week or longer storage that may require a depot.
In other words: if the problem is serious we are no longer talking about depot being a cool feature to have, but a technical necessity for a minimum viable concept that works.
Elon seems to be more convinced about the necessity of a depot than landing thrusters on HLS Starship.
The engine section is full of conductive metal ;) My suggestion is to put MLI above the top tank dome and point the nose towards the Sun. The nose will be "hot" (probably no more than warm) but the only heat leak will be the thin barrel wall. If you insulate the last meter above barrel/dome weld even a 300 K temperature difference would be < 1 kW of heating.I have no idea how big of a problem the boil off will be in shorter time, like a few days or a week, but if it's significant then Starship will need an insulated depot not just for Artemis and Mars, but even for many missions to orbits other than LEO that F9 and FH already can do.
I don't think anyone believes they will be able to do multiple Starship launches per day anytime soon, so even 2 refill launches could mean a week or longer storage that may require a depot.
In other words: if the problem is serious we are no longer talking about depot being a cool feature to have, but a technical necessity for a minimum viable concept that works.
Elon seems to be more convinced about the necessity of a depot than landing thrusters on HLS Starship.
If you point the Starship Tanker's engines at the Sun, you get minimal solar heating on the tanks. The heatshield also provides some insulation. Previous indications were that was sufficient for a significant period of time.
For example, Starship HLS is supposed to have a loiter time of up to several months in NRHO before an Artemis landing.
Short term, a stock SS will do ok for a depot. Long term, not so much. Rad Mod ran numbers for different refueling scenarios and IIRC, stretch tanks and a no return design package made a difference in some. Further down the road it might be reasonable to add active cooling and multiple tankers in popular orbits. Ultimately is would be great to have depots as an available resource rather than a mission specific add on. Especially when launching a clutch of mars bound ships.Indeed, for high orbits the nose to sun approach might be enough to avoid boil-off completely but lower down you would have to do your best block the reflected sunlight and thermal emissions from the surface with the heat shield. The crazy thing is that if it is just ~240 W/m2 of thermal emissions (-18 °C, 265 K) like on the night side (of Earth) a heat shield at ~1 W/m2K on top of a 100 K tank wall would have a surface temperature of 220 K and conduct 120 W/m2, while the bare tank wall with an IR reflectivity likely > 80 % would absorb less than half that! Interesting modeling/optimization problem...
I keep seeing the differences between the first F9 and the current one. SS will be no different. For now, get the sucker working, then start deploying Starlinks. Then look for .7% mass here and .7% there. They've got a lot on their plate.Every such incremental change looks insignificant by itself in isolation but to make the whole thing viable you need enough of them to compound together.Yep, they will analyze any mass saving they can. It's a question of priority. Right now, they need to get to orbit with Starlink satellites. I doubt they will consider any design change for the purpose of mass reduction if it affects the schedule. Clearly, any design change they are required to make for other reasons will take mass into account, so there may be some saving anyway. I would bet that Elon would trade an extra tonne of mass to shorten the schedule by a month. He would probably trade an extra ten tonnes for that month if he knew he would get it back in a year.
SpaceX isn’t gonna ignore a 1% mass savings if it’s staring them in the face.
How does it compare on the day side? Would that white thermal paint improve things? It would be great to get rid of the heat shield but if it does away with a deplorable shade it's worth keeping.The engine section is full of conductive metal ;) My suggestion is to put MLI above the top tank dome and point the nose towards the Sun. The nose will be "hot" (probably no more than warm) but the only heat leak will be the thin barrel wall. If you insulate the last meter above barrel/dome weld even a 300 K temperature difference would be < 1 kW of heating.I have no idea how big of a problem the boil off will be in shorter time, like a few days or a week, but if it's significant then Starship will need an insulated depot not just for Artemis and Mars, but even for many missions to orbits other than LEO that F9 and FH already can do.
I don't think anyone believes they will be able to do multiple Starship launches per day anytime soon, so even 2 refill launches could mean a week or longer storage that may require a depot.
In other words: if the problem is serious we are no longer talking about depot being a cool feature to have, but a technical necessity for a minimum viable concept that works.
Elon seems to be more convinced about the necessity of a depot than landing thrusters on HLS Starship.
If you point the Starship Tanker's engines at the Sun, you get minimal solar heating on the tanks. The heatshield also provides some insulation. Previous indications were that was sufficient for a significant period of time.
For example, Starship HLS is supposed to have a loiter time of up to several months in NRHO before an Artemis landing.Short term, a stock SS will do ok for a depot. Long term, not so much. Rad Mod ran numbers for different refueling scenarios and IIRC, stretch tanks and a no return design package made a difference in some. Further down the road it might be reasonable to add active cooling and multiple tankers in popular orbits. Ultimately is would be great to have depots as an available resource rather than a mission specific add on. Especially when launching a clutch of mars bound ships.Indeed, for high orbits the nose to sun approach might be enough to avoid boil-off completely but lower down you would have to do your best block the reflected sunlight and thermal emissions from the surface with the heat shield. The crazy thing is that if it is just ~240 W/m2 of thermal emissions (-18 °C, 265 K) like on the night side (of Earth) a heat shield at ~1 W/m2K on top of a 100 K tank wall would have a surface temperature of 220 K and conduct 120 W/m2, while the bare tank wall with an IR reflectivity likely > 80 % would absorb less than half that! Interesting modeling/optimization problem...
How does it compare on the day side? Would that white thermal paint improve things? It would be great to get rid of the heat shield but if it does away with a deplorable shade it's worth keeping.The engine section is full of conductive metal ;) My suggestion is to put MLI above the top tank dome and point the nose towards the Sun. The nose will be "hot" (probably no more than warm) but the only heat leak will be the thin barrel wall. If you insulate the last meter above barrel/dome weld even a 300 K temperature difference would be < 1 kW of heating.I have no idea how big of a problem the boil off will be in shorter time, like a few days or a week, but if it's significant then Starship will need an insulated depot not just for Artemis and Mars, but even for many missions to orbits other than LEO that F9 and FH already can do.
I don't think anyone believes they will be able to do multiple Starship launches per day anytime soon, so even 2 refill launches could mean a week or longer storage that may require a depot.
In other words: if the problem is serious we are no longer talking about depot being a cool feature to have, but a technical necessity for a minimum viable concept that works.
Elon seems to be more convinced about the necessity of a depot than landing thrusters on HLS Starship.
If you point the Starship Tanker's engines at the Sun, you get minimal solar heating on the tanks. The heatshield also provides some insulation. Previous indications were that was sufficient for a significant period of time.
For example, Starship HLS is supposed to have a loiter time of up to several months in NRHO before an Artemis landing.Short term, a stock SS will do ok for a depot. Long term, not so much. Rad Mod ran numbers for different refueling scenarios and IIRC, stretch tanks and a no return design package made a difference in some. Further down the road it might be reasonable to add active cooling and multiple tankers in popular orbits. Ultimately is would be great to have depots as an available resource rather than a mission specific add on. Especially when launching a clutch of mars bound ships.Indeed, for high orbits the nose to sun approach might be enough to avoid boil-off completely but lower down you would have to do your best block the reflected sunlight and thermal emissions from the surface with the heat shield. The crazy thing is that if it is just ~240 W/m2 of thermal emissions (-18 °C, 265 K) like on the night side (of Earth) a heat shield at ~1 W/m2K on top of a 100 K tank wall would have a surface temperature of 220 K and conduct 120 W/m2, while the bare tank wall with an IR reflectivity likely > 80 % would absorb less than half that! Interesting modeling/optimization problem...
At what altitude does earth thermal become insignificant?
Short term, a stock SS will do ok for a depot. Long term, not so much. Rad Mod ran numbers for different refueling scenarios and IIRC, stretch tanks and a no return design package made a difference in some. Further down the road it might be reasonable to add active cooling and multiple tankers in popular orbits. Ultimately is would be great to have depots as an available resource rather than a mission specific add on. Especially when launching a clutch of mars bound ships.
Precisely.I keep seeing the differences between the first F9 and the current one. SS will be no different. For now, get the sucker working, then start deploying Starlinks. Then look for .7% mass here and .7% there. They've got a lot on their plate.Every such incremental change looks insignificant by itself in isolation but to make the whole thing viable you need enough of them to compound together.Yep, they will analyze any mass saving they can. It's a question of priority. Right now, they need to get to orbit with Starlink satellites. I doubt they will consider any design change for the purpose of mass reduction if it affects the schedule. Clearly, any design change they are required to make for other reasons will take mass into account, so there may be some saving anyway. I would bet that Elon would trade an extra tonne of mass to shorten the schedule by a month. He would probably trade an extra ten tonnes for that month if he knew he would get it back in a year.
SpaceX isn’t gonna ignore a 1% mass savings if it’s staring them in the face.
As for the number of unique tiles, that is a problem but nothing like the Shuttle. Compared to the Shuttle, the SS is a simple topography. Looking at tiles in the fiddly areas, there is a mix of unique and and duplicate tiles. Many, like the tiles that wrap around an edge are not only there in multiples, they are inherently bi laterally symmetrical. The same tiles can be used on both sides.
Keeping the count as low as possible is an engineering goal. Getting back down in one piece is a mission objective. The number of tiles it takes to meet the objective will define "low as possible".
Methinks the heatshield will be a thorn in the idea of rapid reusability. It is what it is, but it's not the shuttle.
Short term, a stock SS will do ok for a depot. Long term, not so much. Rad Mod ran numbers for different refueling scenarios and IIRC, stretch tanks and a no return design package made a difference in some. Further down the road it might be reasonable to add active cooling and multiple tankers in popular orbits. Ultimately is would be great to have depots as an available resource rather than a mission specific add on. Especially when launching a clutch of mars bound ships.
Yea but just think what a LEO gas station for any orbital rocket will enable. Whats the cost/gal of a fill up with LOX and LCH4 in orbit.
A lot less than a rocket big enough to lift all the propellant it needs.Short term, a stock SS will do ok for a depot. Long term, not so much. Rad Mod ran numbers for different refueling scenarios and IIRC, stretch tanks and a no return design package made a difference in some. Further down the road it might be reasonable to add active cooling and multiple tankers in popular orbits. Ultimately is would be great to have depots as an available resource rather than a mission specific add on. Especially when launching a clutch of mars bound ships.
Yea but just think what a LEO gas station for any orbital rocket will enable. Whats the cost/gal of a fill up with LOX and LCH4 in orbit.
based on some comments by apollo astronauts, that the first 20sec or so of liftoff is extremely violent, that it would be pretty much impossible to touch any of the dials/instruments even if they wanted to, I'm going to predict the tiles if they fly as they are now during the first flight that maybe 5% to 7% will fall off in first minute of flight, after that I would hesitate to predict.Given that the level of vibrations is inversely proportional to the number of engines, I would expect a rather smooth ride as long as the booster is burning. But in general I agree, it would be a miracle if the first heat shield arrives in orbit in one piece.
based on some comments by apollo astronauts, that the first 20sec or so of liftoff is extremely violent, that it would be pretty much impossible to touch any of the dials/instruments even if they wanted to, I'm going to predict the tiles if they fly as they are now during the first flight that maybe 5% to 7% will fall off in first minute of flight, after that I would hesitate to predict.Given that the level of vibrations is inversely proportional to the number of engines, I would expect a rather smooth ride as long as the booster is burning. But in general I agree, it would be a miracle if the first heat shield arrives in orbit in one piece.
But in general I agree, it would be a miracle if the first heat shield arrives in orbit in one piece.
something to remember is that so far the static fires have been with mostly empty starship tanks and the actual flight regime will be full tanks and ignition @ MECO altitude for launch phase and partial tanks and ignition of 3 engines on orbit or 2-3 engines on the flip
It's a consideration of magnitude potential in failure for all tiles individually, calculated as a set. The place where we come to say that a magnitude reduction in peak/transient stressing per tile, is required to get to a situation where all tiles are collectively at a zero failure point.
Ie, that one in a thousand or one in 10,000, really isn't good enough. and that 'problem' will generally show it's face in transient stressing, not just long term stressing.
Where those first seconds of the flight is more akin to chaos in stressing than anything else.
Think freak ocean waves, when searching for a simile of a sort. Which is merely tile reaction to loading, not the loading itself.
Calm down, you’re barking up the wrong tree. I didn’t write any of this!But in general I agree, it would be a miracle if the first heat shield arrives in orbit in one piece.
Nope!
It will be because of design, engineering and process.
It always blows my mind how so many people see a little thing like a tile fall off and jump to the conclusion that the whole design is faulty.
It's as if these people have never conceived something, designed and built it only to find out that you missed one (or five) little things. Doesn't mean that the concept is bad, just that there's more to do to get it to do the job as conceived.
I think this quickness to determine something a failure should be called the "Chicken Little Syndrome".
that is interesting theory that more engines gives less vibration, I would have thought the opposite.Yes more engines = more vibration, but...
The three metal supports on each tile ( the y bracket) are not joined, they are three separate pieces of metal for each
tile, I would have thought the three metal pieces should be joined together it would give less stress on the tiles.
weight of each metal piece is 25g ( 24.68g to be more accurate), so 75g all up for the 'y' bracket metal pieces ( from collected debris boca chica beach post sn11)
[...]https://twitter.com/NicAnsuini/status/1470454169723191301
If my speculative labeling of Nic's picture is correct the the vents would be the ~ 2cm diameter holes in each side of the two round posts ~1m from the edge of the TPS. If that is the case it would seem that the jets, helped by the Coandă effect, managed to get under the blanket and produce pressure differential large enough to dislodge some of the tiles (would only require a fraction of an atmosphere).
Maybe it should have been caught before it happened but it would at least be easy to remedy by welding a small ramp next to the vents and perhaps rotating and/or moving them slightly for later prototypes. The only relevance I can see for this failure mode for the rest of the TPS would be the forward facing edges behind the forward fins/ahead of the aft fins on ascent. We will see if they do anything there before launch...
that is interesting theory that more engines gives less vibration, I would have thought the opposite.
The three metal supports on each tile ( the y bracket) are not joined, they are three separate pieces of metal for each
tile, I would have thought the three metal pieces should be joined together it would give less stress on the tiles.
weight of each metal piece is 25g ( 24.68g to be more accurate), so 75g all up for the 'y' bracket metal pieces ( from collected debris boca chica beach post sn11)
Or alternatively, modify the mounting mechanism to accommodate a small amount of stretch/warp.Kinematic coupling.
On the latest NSF video https://www.youtube.com/watch?v=HHTQATW6C94&t=633s (https://www.youtube.com/watch?v=HHTQATW6C94&t=633s) shows the pan of S21 heat shield and it appears to be heavily damaged from all the manufacturing activities. The hairline fractures are most likely from the flexing action of the skin when transported and lifted. It would point towards the heatshield application and transportation can be done only after the ship can be pressurized rigid, so at a very late stage.
When manufacturing has sequences which can not be broken in separate parallel actions and in this case must be done at extreme heights and awkward positions, it could become a major bottleneck for the manufacturing. Probably a dedicated high bay just for that purpose is needed. Would there be a regulatory safety hassle if starship were pressurized to say, 1.5 bars while work is being done on it? One thing which comes to my mind is that it could require them to pressure test it before applying the shields (as it is considered unsafe to pressure before regulatory testing).
Just talking to keep myself warm.
from that video there is no way you can determine if there are hairline cracks, to see a hairline crack you need much more high resolution images, I think what you refer to as hairline cracks in that video , are in fact chalk marks by the installers, just what they mean I have no idea.I think the first reasonable assumption is that the chalk is used to mark cracks. In any case the marked tiles tend to have either a big X or have the OK mark scratched out suggesting they will all be replaced.
The hairline fractures are most likely from the flexing action of the skin when transported and lifted. It would point towards the heatshield application and transportation can be done only after the ship can be pressurized rigid, so at a very late stage.
A meat hammer (fist) does a good job of impact distribution. Just as important, an experienced tradesman develops a fine tactile sense of limits. Screw up a couple and the feel is there. Few screwups follow. If it takes too much force to install a tile the problem most likely will be clips and/or Y bracket being misaligned, out of spec or damaged. The tile not being square to the surface when hit could mess it up too. That counts as a screwup and should go away with experience.The hairline fractures are most likely from the flexing action of the skin when transported and lifted. It would point towards the heatshield application and transportation can be done only after the ship can be pressurized rigid, so at a very late stage.
How do you jump to the conclusion that the flexing of a very stiff stainless steel can is the likely cause as opposed to something like maybe the pounding them on with a fist?
A meat hammer (fist) does a good job of impact distribution. Just as important, an experienced tradesman develops a fine tactile sense of limits. Screw up a couple and the feel is there. Few screwups follow. If it takes too much force to install a tile the problem most likely will be clips and/or Y bracket being misaligned, out of spec or damaged. The tile not being square to the surface when hit could mess it up too. That counts as a screwup and should go away with experience.The hairline fractures are most likely from the flexing action of the skin when transported and lifted. It would point towards the heatshield application and transportation can be done only after the ship can be pressurized rigid, so at a very late stage.
How do you jump to the conclusion that the flexing of a very stiff stainless steel can is the likely cause as opposed to something like maybe the pounding them on with a fist?
IMO, if the chalk marks represent cracks, there is a design or environmental problem. If the cracks really are coming from the meat hammers and everything is in spec, it's a design that can not be installed manually without special tools. If it's not from the meat hammers it's something in the environment and transport is a good target for the hairy eyeball.
from that video there is no way you can determine if there are hairline cracks, to see a hairline crack you need much more high resolution images, I think what you refer to as hairline cracks in that video , are in fact chalk marks by the installers, just what they mean I have no idea.I think the first reasonable assumption is that the chalk is used to mark cracks. In any case the marked tiles tend to have either a big X or have the OK mark scratched out suggesting they will all be replaced.
Yes and no. Manual trades do amazing cross pollination. Installing door panels on a 70's vintage Ford product, with wire bayonet clips amazingly like the tiles, is very educational. Somehow I became the go to guy for power windows at a Lincoln Mercury dealer. Tiles and door panels are different but have similarities. When I spoke of experienced tradesmen I meant just that - not experienced thermal tile installers.A meat hammer (fist) does a good job of impact distribution. Just as important, an experienced tradesman develops a fine tactile sense of limits. Screw up a couple and the feel is there. Few screwups follow. If it takes too much force to install a tile the problem most likely will be clips and/or Y bracket being misaligned, out of spec or damaged. The tile not being square to the surface when hit could mess it up too. That counts as a screwup and should go away with experience.The hairline fractures are most likely from the flexing action of the skin when transported and lifted. It would point towards the heatshield application and transportation can be done only after the ship can be pressurized rigid, so at a very late stage.
How do you jump to the conclusion that the flexing of a very stiff stainless steel can is the likely cause as opposed to something like maybe the pounding them on with a fist?
IMO, if the chalk marks represent cracks, there is a design or environmental problem. If the cracks really are coming from the meat hammers and everything is in spec, it's a design that can not be installed manually without special tools. If it's not from the meat hammers it's something in the environment and transport is a good target for the hairy eyeball.
One thing to note amout "experienced trademan" is that going into SN20, these didn't really exist. The team's full experience at this point was installing maybe a thousand tiles on the patches on the earlier prototypes, and they had never installed them in the tricky regions like the nose and edges of the fins. It was a learning experience for everyone, and that's fine - this is one of the reasons we build prototypes.
(clip ...)Great question!
During re-entry is all this water going to sublimate/evaporate as the rear of the tiles heat up, and what effect will it then have on plasma layer?
(clip ...)
To have any non trivial thickness of ice to develop on a surface this surface needs to see free airflow, so there's a flow of humidity which then condenses out. If you block air movement (for example by putting on tiles and under-tile padding) you are blocking humidity inflow and there wont be any thick ice layer.As the air under the tiles chills during propellant loading it will contract and as it migrates downward through the fiber layer more air will be drawn in at the top of the tile. Moisture will condense out and freeze. As the padding fills with frozen water (solid? fluffy?) the convection behind the tile will slow and probably stop at some point.
Sorry what is metric T/W ?Thrust to weight ratio.
30 °C air can hold 30 g/m3 of water vapor. Cooling it down to 100 K increases the density ~3x. So a 5 cm layer cooling down and drawing in more air as the density increases will contain a maximum of ~5 g/m2 of water for a grand total of < 10 kg for the whole heat shield. The bare steel surface can potentially collect much more but it will still be more or less identical to the frost on other launch vehicles such as F9 - relatively fluffy and easily dislodged on takeoff.To have any non trivial thickness of ice to develop on a surface this surface needs to see free airflow, so there's a flow of humidity which then condenses out. If you block air movement (for example by putting on tiles and under-tile padding) you are blocking humidity inflow and there wont be any thick ice layer.As the air under the tiles chills during propellant loading it will contract and as it migrates downward through the fiber layer more air will be drawn in at the top of the tile. Moisture will condense out and freeze. As the padding fills with frozen water (solid? fluffy?) the convection behind the tile will slow and probably stop at some point.
ISTM that this will be the mechanism. The open issues seems be the texture of the ice and how much it takes to clog the padding. The added weight of ice makes the 1.5 T/W look like a smart margin. Even fluff starts adding up.
ship 21 appears to be some red silicone used on a small section of tiles, a narrow band, i'm guessing that section not in contact with cold liquids? anyone can line up that section with inside liquids?I had actually forgotten about that when talking about tiles glued to cryogenic tank walls before:
I've given some thought to improve starship tile system and cracking problem.
( theres quite a bit of detail in the structure but for brevity will post basics)
Came up with this:
A backing plate which tiles are red siliconed to. Backing plate can pop onto existing three pins on via 3 lugs.
Backing plate material of suitable material ( carbon fibre or aluminium or stainless or phenolic resin).
Design of backing plate so that its very stiff structurally but lightweight. Red silicone ample proportion to give soft base for tile ( maybea few mm thickness).
One form either the whole backing plate is ablative material such as phenolic resin, if tile falls off there is some secondary system to save the ship, or just a thin layer of phenolic resin.
I've given some thought to improve starship tile system and cracking problem.Why? What problem is this trying to solve, and why does it solve it? It adds extra mass and extra points of failure, but does not appear to eliminate any mass or eliminate any points of failure.
( theres quite a bit of detail in the structure but for brevity will post basics)
Came up with this:
A backing plate which tiles are red siliconed to. Backing plate can pop onto existing three pins on via 3 lugs.
Backing plate material of suitable material ( carbon fibre or aluminium or stainless or phenolic resin).
Design of backing plate so that its very stiff structurally but lightweight. Red silicone ample proportion to give soft base for tile ( maybea few mm thickness).
One form either the whole backing plate is ablative material such as phenolic resin, if tile falls off there is some secondary system to save the ship, or just a thin layer of phenolic resin.
I've given some thought to improve starship tile system and cracking problem.Why? What problem is this trying to solve, and why does it solve it? It adds extra mass and extra points of failure, but does not appear to eliminate any mass or eliminate any points of failure.
( theres quite a bit of detail in the structure but for brevity will post basics)
Came up with this:
A backing plate which tiles are red siliconed to. Backing plate can pop onto existing three pins on via 3 lugs.
Backing plate material of suitable material ( carbon fibre or aluminium or stainless or phenolic resin).
Design of backing plate so that its very stiff structurally but lightweight. Red silicone ample proportion to give soft base for tile ( maybea few mm thickness).
One form either the whole backing plate is ablative material such as phenolic resin, if tile falls off there is some secondary system to save the ship, or just a thin layer of phenolic resin.
That seems like a "fix the tiles" problem (e.g. adding a fibre reinforced core to the sintered preform, or using a more fractal metal insert to spread loads more evenly) rather than an "add a whole extra attachment mechanism" problem.I've given some thought to improve starship tile system and cracking problem.Why? What problem is this trying to solve, and why does it solve it? It adds extra mass and extra points of failure, but does not appear to eliminate any mass or eliminate any points of failure.
( theres quite a bit of detail in the structure but for brevity will post basics)
Came up with this:
A backing plate which tiles are red siliconed to. Backing plate can pop onto existing three pins on via 3 lugs.
Backing plate material of suitable material ( carbon fibre or aluminium or stainless or phenolic resin).
Design of backing plate so that its very stiff structurally but lightweight. Red silicone ample proportion to give soft base for tile ( maybea few mm thickness).
One form either the whole backing plate is ablative material such as phenolic resin, if tile falls off there is some secondary system to save the ship, or just a thin layer of phenolic resin.
Most of the tile failures seem to be the attachment points separating from the bulk of the tile, or the entire tile cracking around the attachments. Adhering the entire back of the tile to a solid surface would spread those concentrated loads out over the surface and should reduce cracking and pull-out. It would also allow that exacting and time-consuming adhesive step to be done in a factory instead of on the vehicle, as the whole assembly would simply snap on to the welded mounting points.
But it does look heavy, especially once you consider the extra tile thickness needed to keep the silicone adhesive below its failure temperature. SpaceX seems to be trying to eliminate the adhesive as much as possible.
The bulk tile material can likely handle >1500 K, the felt is similar or betterFelt is worse. Uncoated tiles would also not fare well.
I'm not sure if I would agree with edzeiba, you are saying that the black ceramic glass coating which is maybe as thick as a human hair is doing most of the work?? I find that hard to believe ( said with max smart ( agent 86)voice)
Yes, the tile coating can withstand higher temperatures - possibly up to 2000 K. The tiles are usually limited by the maximum temperature of the bulk silica fiber material which is the reason for TUFROC where a layer of higher temperature carbon-based insulator is put in between the coating and the silica insulator.The bulk tile material can likely handle >1500 K, the felt is similar or betterFelt is worse. Uncoated tiles would also not fare well.
Whilst the tiles look like a big block of insulator with a thin cosmetic coating, in terms of functionality during re-entry (enormous radiative heat loading, plus plasma impingement) they're more like a thin glass sheet doing most of the work reflecting and reradiating heat, and the tile body just handling what heat conducts through that layer. The unsintered felt is not suitable on its own as an exposed bare TPS.
so my backplate concept 4, a bit more detail only showing right hand side in any detail, nothing to scale.
yup just nutting out some ideas.cools off quickly at the surface due to radiative and convective effects. Internal heat transfer is slow. Corners have the most surface area for a given mass.
These tiles are really quite curious material, what puzzles me is this:
the videos showing the tiles coming straight out of an oven and the corners cooling off immediately so they can be picked up by hand to me is very curious behaviour.
this video is particularly informative
https://www.youtube.com/watch?v=CchPemGaEmw (https://www.youtube.com/watch?v=CchPemGaEmw)
Tiles are 90plus percent air.
The thermal conductivity of both air and the silica fibres are low, as is the specific heat, but exposing to air the corners will cool off very very quickly indeed. This seems counter-intuitive to me. In this video link its described as the tile in insulating itself from his hand at the 3:43 mark.
So the speed at which heat is transferred is very very slow, yet the corners cool immediately?
Can anyone explain that in terms of physics in some detail?
Warning dumb question from a non-rocket-scientist: As I understand it, re-entry aerobraking is used to dissipate the kinetic energy of the vehicle. Most of the energy is converted to heat in the bow shockwave, and some of this heat gets transferred to the skin of the vehicle by several methods. Several methods are used to prevent the heat from damaging the structure, including insulation, ablation, and (in theory) transpiration. Ablation and transpiration work by expending mass to carry away the heat.
So here is the question: can a vehicle use its engines to inject mass to create a buffer between the bow shock and the vehicle? Orient the vehicle to enter tail first, and then fire up the engines to create as cool an exhaust as they are capable of at as low a thrust as they can. For a methalox engine, this might be done by using only the LOX and just enough methane to drive the turbopump. This exhaust would push the bow shock out and would also carry away heat the way the ablated material does in an ablative heat shield. The bow shock provides deceleration by pushing the exhaust back against the tail.
You need to take some mass to orbit in any event: TPS tiles, transpiration cooling mass and equipment, ablative heat shield, whatever. The question is: how much? In theory (and only in theory) the amount of heat carried away is roughly proportional to the amount of mass use to carry that heat, in addition to a huge and scary number of other factors. The potential advantage of using engine exhaust is that you don't need the mass of a separate mass-injection system.Warning dumb question from a non-rocket-scientist: As I understand it, re-entry aerobraking is used to dissipate the kinetic energy of the vehicle. Most of the energy is converted to heat in the bow shockwave, and some of this heat gets transferred to the skin of the vehicle by several methods. Several methods are used to prevent the heat from damaging the structure, including insulation, ablation, and (in theory) transpiration. Ablation and transpiration work by expending mass to carry away the heat.
So here is the question: can a vehicle use its engines to inject mass to create a buffer between the bow shock and the vehicle? Orient the vehicle to enter tail first, and then fire up the engines to create as cool an exhaust as they are capable of at as low a thrust as they can. For a methalox engine, this might be done by using only the LOX and just enough methane to drive the turbopump. This exhaust would push the bow shock out and would also carry away heat the way the ablated material does in an ablative heat shield. The bow shock provides deceleration by pushing the exhaust back against the tail.
You would need to take that additional fuel to orbit first right? so your payload would need to shrink...
But there was (and maybe still is) considered something similar for starship, https://en.wikipedia.org/wiki/Transpiration_cooling, but not with engines but with bleeding methane through starship skin.
There are many ways to get rid of heat, only question is what is the lightest solution.
So here is the question: can a vehicle use its engines to inject mass to create a buffer between the bow shock and the vehicle? Orient the vehicle to enter tail first, and then fire up the engines to create as cool an exhaust as they are capable of at as low a thrust as they can.Yes, Falcon 9 does this during the Entry Burn (as a welcome side-effect of burning to decelerate). However:
Sometimes the drag produced by the vehicle actually goes down when you burn the engines. And, of course, rocket exhaust is hot…Firing engines directly into the bow shock collapses the bow shock and allows the superheated plasma that it kept at bay to move into contact with the vehicle wherever it is not being directly displaced by exhaust gas.
Sometimes the drag produced by the vehicle actually goes down when you burn the engines. And, of course, rocket exhaust is hot…Reducing the drag is not an inherent problem. It just increases the amount of time it takes to dissipate the kinetic energy of reentry and reduces peak thermal input rate, while providing more time to dissipate the heat. We will end up at the same terminal velocity in any case, and as soon as the velocity gets low enough we will no longer need the exhaust buffer so we shift to a ventral-first approach and increase drag.
Warning dumb question from a non-rocket-scientist: As I understand it, re-entry aerobraking is used to dissipate the kinetic energy of the vehicle. Most of the energy is converted to heat in the bow shockwave, and some of this heat gets transferred to the skin of the vehicle by several methods. Several methods are used to prevent the heat from damaging the structure, including insulation, ablation, and (in theory) transpiration. Ablation and transpiration work by expending mass to carry away the heat.
So here is the question: can a vehicle use its engines to inject mass to create a buffer between the bow shock and the vehicle? Orient the vehicle to enter tail first, and then fire up the engines to create as cool an exhaust as they are capable of at as low a thrust as they can. For a methalox engine, this might be done by using only the LOX and just enough methane to drive the turbopump. This exhaust would push the bow shock out and would also carry away heat the way the ablated material does in an ablative heat shield. The bow shock provides deceleration by pushing the exhaust back against the tail.
So oxygen-rich exhaust makes absolutely zero sense.
What would be fuel-rich exhaust. Oxygen-rich exhaust attaching vehicle components would be adding fire to the fuel.
So oxygen-rich exhaust makes absolutely zero sense.
You can perhaps even say it would be adding fuel to the fire.
thanks xvel for explanation of cooling of tile edges out of oven.Adding a heatsink just means that all that heat you have been so carefully trying to avoid reaching the vehicle body is given a conduction path that dumps it into the vehicle body, defeating the entire point of the TPS. Because the only way to sink that heat is for it to go from a hot thing (the tile) to a cold thing (the vehicle).
There are many videos of people heating these tiles with blow torch, seems there are alot of the shuttle type tiles out there. So if I understand this correctly, the heat transfer is extremely slow, you heat up a part of the tile with torch and basically just that part gets hot.
So heat from the inside of tile takes quite a while to reach the outside ,a slow process, but once the heat reaches the edges its easily taken away by air ( in the case of the videos showing cool edges appear almost immediately).
With that in mind I suspect a heatsink of say aluminium might be quite effective in removing the heat that has reached the surface of the tile.........it might be relatively easy to cool the rear of the tile just going by the videos.
well seems I aint so crazy afterall, appears Musk has already commented on water cooling during re-entry some time back:
https://www.teslarati.com/spacex-ceo-elon-musk-starship-transpiring-steel-heat-shield-interview/
thanks xvel for explanation of cooling of tile edges out of oven.Adding a heatsink just means that all that heat you have been so carefully trying to avoid reaching the vehicle body is given a conduction path that dumps it into the vehicle body, defeating the entire point of the TPS. Because the only way to sink that heat is for it to go from a hot thing (the tile) to a cold thing (the vehicle).
There are many videos of people heating these tiles with blow torch, seems there are alot of the shuttle type tiles out there. So if I understand this correctly, the heat transfer is extremely slow, you heat up a part of the tile with torch and basically just that part gets hot.
So heat from the inside of tile takes quite a while to reach the outside ,a slow process, but once the heat reaches the edges its easily taken away by air ( in the case of the videos showing cool edges appear almost immediately).
With that in mind I suspect a heatsink of say aluminium might be quite effective in removing the heat that has reached the surface of the tile.........it might be relatively easy to cool the rear of the tile just going by the videos.
Yup if the felt discourages ice buildup, these are just thought experiments.Not a given. Boca Chica is a dusty place, and dust will also be liberated on engine startup.
Since we can see from the static fires that there is ice there in the felt and comes out as a white cloud, as it does on the non-tiled side, I'm not encouraging ice build up, its already there!
bleeding off a bit of heat energy at the rear to lower temp for red rtv attachment and assisting cooling at the front of the tiles at same time, I think is not a bid idea.It is a bad idea. The entire purpose of the tiles is to have the maximum thermal resistance achievable between the outer surface and the inner surface. Any conduction path added to the inner surface is completely opposite to the entire purpose of the TPS.
Yup if the felt discourages ice buildup, these are just thought experiments.
Since we can see from the static fires that there is ice there in the felt and comes out as a white cloud, as it does on the non-tiled side, I'm not encouraging ice build up, its already there!
I dont think SpaceX current tile design with embedded stainless will be reliable and tiles will crack or be lost during first test flight, hence having a go at nutting out some alternate designs. I understand your concern about the design, the tiles will do their job regardless of whats behind them, bleeding off a bit of heat energy at the rear to lower temp for red rtv attachment and assisting cooling at the front of the tiles at same time, I think is not a bid idea.
I could be wrong, but you would have to convince me some physics why it wouldn't work.
Still no physics to say why it wont work? Some heat transfer calculations might be useful.There’s no point in analyzing a design that gets the parts backward. Maybe read more and write less?
Emphasis mine. Excellent advice in almost any circumstance. To this I would also add the old rule that if someone thinks they've got some new concept, design, or principal that going to change everything, or at least is a significant advancement, and the general response is along the lines of "nope - that'll never work", then the onus is on the originator of the idea (looking at you, brettly2021) to demonstrate otherwise with physics, calculations, working models, etc. It has to be this way. We're it otherwise hardworking professionals in every field would never get anything done, as they'd have to spend all their time refuting (with physics, calculations, non-working models, etc.) "new" ideas brought to them by the mighty horde of those who ... write more and read less.Still no physics to say why it wont work? Some heat transfer calculations might be useful.There’s no point in analyzing a design that gets the parts backward. Maybe read more and write less?
Still no physics to say why it wont work? Some heat transfer calculations might be useful./s
Yup I realise spacex/tesla has top scientists, thats why I'm so surprised at the stainless embedded in the tiles.
Lets see how the tiles go during ascent and re-entry.
At this time it appears that in order to get the backing plate system to work ( to produce steam behind the tiles during re-entry)You don't want to do this, at all. Gas pressure generated behind the tiles is trying to push the tiles off, which is bad.
At this time it appears that in order to get the backing plate system to work ( to produce steam behind the tiles during re-entry)
the shuttle tile system was tile/rtv/sip/al : tile then red silicone then felt pad then aluminium structure.
They suggest in that paper in last post that at time 15min mark aluminium and red rtv reach peak temp of 50degC and aluminium skin reach same 50degC . They say max structural limit of aluminium as 117 degC ( not melting point!).
Anyhow for that particular location ( wing base centre not leading edge) the temp is way way below boiling point of water, so will be no issue with steam formation at all. Other locations may differ somewhat, I thought someone had given some really high temps for the back of tiles/aluminium surface but appears not that hot in this area anyhow.
I know the leading edges get really hot not relevant for majority of tiles though.
If this is typical of the majority of the tiles.
I'm thinking very light very thin carbon fibre backing plate, with its rigity and some forms very high temp resistance, would probably suit. 3D printed to get lightest weight/thinest design might just do that job, and could probably match the weight of the 3 stainless pieces being used at present.
Amateur here though, could be wrong.
there is a good reason to re-engineer, the stainless steel plates ( 3x) that are embedded into the tiles are the current method of having a type of backing plate. I believe the design is very much flawed. I'm quite convinced spacex will do away with those 3 stainless mounting brackets. Thats my whole purpose of discussing this. The tiles have very little expansion as far as I'm aware, will be quite different to the stainless expansion, and the tiles are fragile. There is a method to increase density of the rear of tiles which was used on shuttle, which is probably what space x has done,I imagine every effort will be made to minimise ice build up behind the tiles as it will add mass. But assuming that there is at least a little, what's going to happen to it? Firstly strong vibration will loosen it and break it up and air flow in the lower atmosphere will blow it out during launch. Any that remains after that will sublimate into the vacuum. There really is no chance of steam forming very late in re-entry.
to overcome the issues but I really think its a bad method and wont be used for long. Hence the reason for discussing backing plate ideas. It certainly is an interesting way to learn about the tiles/heat transfer etc. I'm a novice, knowledge is not great but is increasing.
I think I was misled by a youtube video which said the tiles were actively cooled after landing, I think that is wrong.
There will be a much better form of attachment/backing plate designed by SpaceX, why not put some ideas out there of different ways to do it?
The steam formation is what I consider something that will be an issue when the tile heat reaches the felt backing,
I'm suggesting it will likely happen, why not discuss it? I might be wrong but it appears at this stage there is ice formation in the felt backing, as its clearly visible during test fires ( although one person is suggesting its just dust, problem is its same white cloud visible on the tile side and the non-tile side of the starship ....very much doubt its dust, there will be some dust but the white cloud would not be white if it was just dust)
I'm not sure as yet but its possible steam will form very late in re-entry, since the heat takes so long to get to the back of the tiles, I will have some data soon on that.
there is a good reason to re-engineer, the stainless steel plates ( 3x) that are embedded into the tiles are the current method of having a type of backing plate. I believe the design is very much flawed. I'm quite convinced spacex will do away with those 3 stainless mounting brackets. Thats my whole purpose of discussing this.I think I speak for many when I say that I do not quite share your conviction :) Remember SpaceX engineers (some of which have decades of experience with these TPS materials and designs) have spent many thousands of hours designing and testing different configurations - of which we have only seen a handful.
The tiles have very little expansion as far as I'm aware, will be quite different to the stainless expansion, and the tiles are fragile. There is a method to increase density of the rear of tiles which was used on shuttle, which is probably what space x has done, to overcome the issues but I really think its a bad method and wont be used for long. Hence the reason for discussing backing plate ideas.I do not think we have ever had the chance to see a tile fail from CTE mismatch as opposed to installation or vibration.
there is a good reason to re-engineer, the stainless steel plates ( 3x) that are embedded into the tiles are the current method of having a type of backing plate. I believe the design is very much flawed. I'm quite convinced spacex will do away with those 3 stainless mounting brackets. Thats my whole purpose of discussing this. The tiles have very little expansion as far as I'm aware, will be quite different to the stainless expansion, and the tiles are fragile.
there is a good reason to re-engineer, the stainless steel plates ( 3x) that are embedded into the tiles are the current method of having a type of backing plate. I believe the design is very much flawed.Then rather than trying to propose solutions to non-problems, you should instead be concentrated on providing some evidence that your belief has any resemblance to reality. That some cracked tiles have 3-fold patterns is not much evidence on its own when the tiles themselves have 3-fold symmetry (as a subset of having 6-fold symmetry).
there is a good reason to re-engineer, the stainless steel plates ( 3x) that are embedded into the tiles are the current method of having a type of backing plate. I believe the design is very much flawed. I'm quite convinced spacex will do away with those 3 stainless mounting brackets. Thats my whole purpose of discussing this. The tiles have very little expansion as far as I'm aware, will be quite different to the stainless expansion, and the tiles are fragile.
the 3 steel plates form a 3 point kinematic mount that easily deals with thermal expansion and mechanical vibration. ther is no need for a backing plate or bonding
The bulk tile material can likely handle >1500 K, the felt is similar or better, the steel should be good to at least 700 K indefinitely (probably more than 900 K at the low durations/cycles involved) and the brackets/mounting pins should be similar or better (they can use a different alloy and are fine with annealed material properties). They should all be ok down to 0 K.
.... I think the space shuttle tiles probably thicker than starship so rear side of tile will be over 50degc, no idea what temp it will go to....
I'm not sure of the relationship between tile thickness and peak temp on back side, lets say as a guess its linear relationship, then if the shuttle tiles reach 50degC peak at rear, and if the starship tiles are say 1/3 the thickness, then maybe ( 3 times shuttle temp)150degC rear side temp of tiles.......probably way out. Can only guesstimate.Thickness is not the only factor. Re-entry profile and thus total thermal load and thermal soak time are also major factors in maximum backside temperature.
I'm going to take a guess at around 100degC or just under.
Another thought, since the tiles are pushed into the pins which sort of latches them, why not have the pins such that when you push them on they latch, if you push them in again they de-latch and spring back out. Would make replacement super fast.If you're replacing a tile, you do not care about damaging it so drilling through to reach the latch is not an issue. However, a delatchable tile introduces an unnecessary risk of delatching unintentionally e.g. on encountering a pressure that would not damage the time but provides sufficient force to delatch.
just watching everyday astronaut interview pt2 with Musk, he talks a bit about the heatshield tiles, on thing he mentions is that hot ullage gas goes into the tank, so the inside of the tank has some temperature at some stage.Autogenous pressurization of the tanks. Hot gas oxygen in the liquid oxygen tank, to fill the volume and push the LOX into the pumps. Same with methane gas in the liquid methane tank.
I think the word he used is ullage ( I had to look it up).
there is a good reason to re-engineer, the stainless steel plates ( 3x) that are embedded into the tiles are the current method of having a type of backing plate. I believe the design is very much flawed. I'm quite convinced spacex will do away with those 3 stainless mounting brackets. Thats my whole purpose of discussing this. The tiles have very little expansion as far as I'm aware, will be quite different to the stainless expansion, and the tiles are fragile. There is a method to increase density of the rear of tiles which was used on shuttle, which is probably what space x has done,
to overcome the issues but I really think its a bad method and wont be used for long. Hence the reason for discussing backing plate ideas. It certainly is an interesting way to learn about the tiles/heat transfer etc. I'm a novice, knowledge is not great but is increasing.
I think I was misled by a youtube video which said the tiles were actively cooled after landing, I think that is wrong.
There will be a much better form of attachment/backing plate designed by SpaceX, why not put some ideas out there of different ways to do it?
The steam formation is what I consider something that will be an issue when the tile heat reaches the felt backing,
I'm suggesting it will likely happen, why not discuss it? I might be wrong but it appears at this stage there is ice formation in the felt backing, as its clearly visible during test fires ( although one person is suggesting its just dust, problem is its same white cloud visible on the tile side and the non-tile side of the starship ....very much doubt its dust, there will be some dust but the white cloud would not be white if it was just dust)
I'm not sure as yet but its possible steam will form very late in re-entry, since the heat takes so long to get to the back of the tiles, I will have some data soon on that.
I'm not sure of the relationship between tile thickness and peak temp on back side, lets say as a guess its linear relationship, then if the shuttle tiles reach 50degC peak at rear, and if the starship tiles are say 1/3 the thickness, then maybe ( 3 times shuttle temp)150degC rear side temp of tiles.......probably way out. Can only guesstimate.Using your logic, that would be not 50deg C but 323deg K. I don't know one way or the other if it works that way.
I'm going to take a guess at around 100degC or just under.
Another thought, since the tiles are pushed into the pins which sort of latches them, why not have the pins such that when you push them on they latch, if you push them in again they de-latch and spring back out. Would make replacement super fast.
last sequence show cooling off of the small cube, over a period of 24 seconds, you can see the corners and edges continue to cool and change to blackish colour. I was curious as to why the corners and edges cool off more rapidly and I think I have a reasonable explanation:This is pretty well correct, except for that last sentence.
The heat inside the cube can be visualised as a sphere, where the heat from the centre conducts outwards in all directions at the same rate. It takes longer for the heat too reach the edges than the face of the cube, and longer for the heat to reach the vertices ( corners) than it takes to reach the edges. This seems pretty obvious and the rate of heat transfer is very very slow through the cube.
But at the surface radiant heat transfer can occur to the surrounding air, that rate of heat transfer is much faster than the rate at which heat transfers through the cube.
Please please Starship heat shield only. Dont ruin one of the 4 or 5 good threads.Could use some thread trimming at this point.
From latest pictures on L2, it appears that the gap between tiles is 2-3 popsicle stick thicknesses. These guys know high tech!Or possible 1 carpenter's pencil.
:^)
John
From latest pictures on L2, it appears that the gap between tiles is 2-3 popsicle stick thicknesses. These guys know high tech!Or possible 1 carpenter's pencil.
:^)
John
From latest pictures on L2, it appears that the gap between tiles is 2-3 popsicle stick thicknesses. These guys know high tech!Or possible 1 carpenter's pencil.
:^)
John
Sure looked like one.
John
just having a look at John L's papers, really nice work. What I think is interesting is that what appears on the surface to be a simple tile, in order to predict its nature mathematically is an extremely complex matter.
The formulas etc given in the nasa paper in last link put up by John is a work of art and would require some time to understand it well. Thanks John for simplifying it down to something that is much easier to understand in your paper.
Would you be able to comment on the graph attached, I'm trying to understand it.
Lets say thickness of tile is 2cm
then some results are ( just approximate):
outside max: 330degC ( 600K) gives inner max of -60degC ( diff: 270degC)
530degC ( 800K) gives inner max of 280degC ( diff: 250degC)
730degC ( 1000k) gives inner max of 560degC ( diff: 170degC)
930degC ( 1200k) gives inner max of approx 780degC ( extrapolated) ( diff: 150degC)
where diff : is difference between outer and inner wall max temps.
Would you agress with this interpretation of your graph and would anyone know the exact thickness of the majority of tiles on the underbelly of the starship?
sorry only degC makes sense to me.
thanks for feedback and link, if anyone knows the actual thickness of a belly tile, your graph will show us the actual rear temperature, at the moment looks like its going to be pretty darn hot.
thanks for feedback and link, if anyone knows the actual thickness of a belly tile, your graph will show us the actual rear temperature, at the moment looks like its going to be pretty darn hot.Note that the graph is for steady-state conditions, whereas EDL is a limited heat-pulse. Once heating stops, heat soaked into the insulator is now being conducted away to both faces rather than just the inner face in the steady-state regime (with the hottest region near the outer skin also being closest to the new cold surface), and you have a limited amount of energy being input into the system rather than the unlimited quantity of the steady state model.
The model looks like it is for steady state with a conducted heat load of 909 W/m2. The heat capacity of a 4 mm SS hull is about 16kJ/m2K so it would heat up at a rate of ~200K/h for these thickness and temperature combinations...thanks for feedback and link, if anyone knows the actual thickness of a belly tile, your graph will show us the actual rear temperature, at the moment looks like its going to be pretty darn hot.Note that the graph is for steady-state conditions, whereas EDL is a limited heat-pulse. Once heating stops, heat soaked into the insulator is now being conducted away to both faces rather than just the inner face in the steady-state regime (with the hottest region near the outer skin also being closest to the new cold surface), and you have a limited amount of energy being input into the system rather than the unlimited quantity of the steady state model.
The model looks like it is for steady state with a conducted heat load of 909 W/m2. The heat capacity of a 4 mm SS hull is about 16kJ/m2K so it would heat up at a rate of ~200K/h for these thickness and temperature combinations...thanks for feedback and link, if anyone knows the actual thickness of a belly tile, your graph will show us the actual rear temperature, at the moment looks like its going to be pretty darn hot.Note that the graph is for steady-state conditions, whereas EDL is a limited heat-pulse. Once heating stops, heat soaked into the insulator is now being conducted away to both faces rather than just the inner face in the steady-state regime (with the hottest region near the outer skin also being closest to the new cold surface), and you have a limited amount of energy being input into the system rather than the unlimited quantity of the steady state model.
So unless I am mistaken these particular graphs have almost no relevance ro temperatures during EDL.
I posted a graph for space shuttle a few pages back, showed the peak heating region lasted for about 14minutes for shuttle, assuming will be similar for starship, so although referred to as a heat pulse, that is a significant amount of time where high temperatures are sustained.I could be very off on this as I took literally only one aerospace engineering class as an elective, but it seems to me that starship will renter slightly faster than the shuttle as it has significantly less cross range. Or I guess maybe a better way to say it is as a question: how does the difference in shape between shuttle and starship change the thermal load the heat shield experiences? Less or more total heat flux? Greater or lesser peak flux? I know there is speculation up thread, so is it safe to assume the shuttle is a good model?
reason I posted regarding the 14minute period peak heating region ( from 80k to 50km) of the shuttle is that some posters mentioned that the tiles see a heat pulse, in my mind the word 'pulse' is associated with a very short time frame, the pulse of a heart for example is very quick, pulses in electronics tend to be very quick. Since the period of peak heating will be what I consider a fairly long period ( on the order of almost 1/4 of an hour) I just wanted to clear up exactly what the other contributors are meaning by a heat 'pulse'. Pulse is probably not the best descriptor for it.
How close it will be to starship peak heating period I cannot say.
anyone know what caused the temperature to jump back up shown in fig 17 by red circle.
Simulation video shows tile vibration up close. Start at about 4:30 or so.I wonder if it is intentional or just an artifact of the camera shake implementation - in any case I would say not realistic.
Realistic or no?
https://youtube.com/watch?v=NOT4-XwU9qQ
Simulation video shows tile vibration up close. Start at about 4:30 or so.I wonder if it is intentional or just an artifact of the camera shake implementation - in any case I would say not realistic.
Realistic or no?
https://youtube.com/watch?v=NOT4-XwU9qQ
The tiles are light and fairly rigidly attached to the hull so large scale movement like that in the video would likely require vibration amplitudes of 100's of gs. Any resonant frequencies would be much higher.
Sideways movement like that - i.e. a large fraction of the attachment pin length - would also lead to metal fatigue within minutes although I suspect the tiles would completely crumble away before that.
In reality the tiles are obviously not expected to move more than a mm or so as there are no gap fillers in between them and tiles contacting each other would rapidly damage them.
Simulation video shows tile vibration up close. Start at about 4:30 or so.
Realistic or no?
https://www.youtube.com/watch?v=NOT4-XwU9qQ
Simulation video shows tile vibration up close. Start at about 4:30 or so.
Realistic or no?
https://www.youtube.com/watch?v=NOT4-XwU9qQ
This looks to me like the simulation is showing the ship shaking under thrust. Nothing tile specific.
I noticed in a recent NSF daily update youtube video that the tiles on the top of the "bulge" that hold the upper flap/fin are much thicker than most tiles (estimating 3-4x) (sorry no link, can't find which day). I assume they are the same material, so the model must have much more heating at that point. Is it expected to be that different?
Tile RUD
S24 nose cone close ups
Aft static aero leading edge
What are those seals made from?
some nice detail in that photo:If by "asbestos based" you mean "made from high temperature ceramic fibers" then that is most likely the case, just like the white insulation and the tiles themselves. The exact composition might be the same or optimized for each application, we have no way of knowing unless they tell us.
green arrow can see fibrous material rapped around the edges of the tiles as tile spacer.
red arrow can see the material is very fibrous: I wonder if its asbestos based?
can also see that tiles are likely just bonded directly to the aluminium frame ( rtv glue?)
some sound reasoning there, I wonder what effect ( if any) those rather long fibres sticking out will have on the plasma?They will melt away within seconds of entry interface.
T I L E S
- @NASASpaceflight
Ooops, vent causes tiles to fly in the breeze
https://twitter.com/kspaceacademy/status/1530209785500557315
heres an interesting homemade tps tile:Well, it has the shape in common, I guess. But that's about it.
https://www.youtube.com/watch?v=E7MxSIkpcrk
Nothing to indicate it is Asbestos either, and no good reason to use Asbestos for TPS either (as far as I am aware Asbestos has not been used for spacecraft TPS).
The current tiles are very, very close to the STS tiles in composition and method of manufacture. The adhesion mechanism for non-pin tiles is also very similar (RTV Silicone backing with inter-tile batting), so it is very likely the gap-fillers are also the same or very similar silica fibre pads.
Nothing to indicate it is Asbestos either, and no good reason to use Asbestos for TPS either (as far as I am aware Asbestos has not been used for spacecraft TPS).
The current tiles are very, very close to the STS tiles in composition and method of manufacture. The adhesion mechanism for non-pin tiles is also very similar (RTV Silicone backing with inter-tile batting), so it is very likely the gap-fillers are also the same or very similar silica fibre pads.
When I was attending the Cosmonauts exhibition at the Science Museum in London I chatted with the Curator of the event. He said they'd had a difference of opinion - cultural - with the Russians as the Vostok and Voskhod capsules were shedding asbestos. The Russians thought nothing of it, the Londoners were unhappy! During the exhibition itself the flown vehicles were safely behind glass!
There are many photographs showing fibrous material flaking off the early Soiviet vehicles post-landing, so yes, asbestos has been flown in space as part of TPS.
Another interesting fact: a lot of the darker, new tiles (the replacements) are located over antennas, which we sometimes used as convenient access points for airframe structural inspections between flights. /1
2/ You can tell these are the antenna locations by the four white chevrons painted onto the tiles around each antenna. We used those to align ground-testing antennas to verify the comm/nav systems worked before the next flight.
3/ Another interesting fact: each tile has a hole in it with a white circle painted around the hole so technicians could find it. That hole was used to inject water-proofing spray into the inside of every single tile before each rollout to the launch pad. I marked a few examples:
4/ Oh, but why did we have to spray water-proofing spray inside each and every Space Shuttle tile before every launch? Those tiles protect against the super hot plasma during re-entry from space, and we know there isn’t any water up there! I’m glad you asked…
5/ The problem was that the Space Shuttle had to sit through frequent rainstorms while it was on the launch pad, and if rain seeped into the tiles then it would add a huge amount of weight to the vehicle, which could prevent it from achieving the desired orbit.
6/ But why weren’t the tiles simply sealed so the rain couldn’t get in? I mean, if you had to cut a hole in the surface to inject the water-proofing spray, then the water shouldn’t be able to get in anyhow, right? Well no, because we couldn’t actually seal the tiles. Why not?…
7/ Because the tiles were 90% hollow and were filled with air, and when the Space Shuttle flew up into the vacuum of space, the air needed to easily get out of the tiles or then pressure would make them explode and then they would not protect the Shuttle during landing.
8/ But why were they 90% hollow? Because the whole point of them was to be excellent insulators during hot re-entry from space. They were made of tiny silica fibers that barely touched each other so heat could barely conduct through them.
9/ Here’s an interesting video on how they were made. They were such good insulators you could heat them to glowing-hot while holding them in your hand. newsflare.com/video/173291/w…
10/ So then, if they had to let air out while launching, and the coating couldn’t keep water out, then why have the coating? Two reasons. 1st, to be a smooth surface so the plasma would flow without turbulence over the surface during entry to minimize heating. And…
11/ 2nd, to have high emissivity in the desired wavelengths so heat that *did* get into the tiles from the hot plasma would radiate back to space more easily than go into the skin of the Space Shuttle. Thus, they were black over the hotter parts, white over the cooler parts.
12/ So they were hollow, filled with air that needed to get out while the Shuttle was “going uphill”, but they had to be coated which would restrict the air getting out. So the coating was simply left off near the base of every tile, allowing the air an escape path.
13/ So that escape path for the air meant that the rain could get into the tiles before launch, weighing the vehicle down tremendously, and that would have been a giant problem!
14/ Part of the reason this problem was so giant was that the silica fibers that make up the body of each tile are hydrophilic — “water loving”. Water clings to it. Any water that got into a tile would never want to come out again. It would become happy water inside its new home.
15/ Materials are sometimes classified as hydrophobic — water tries to get away from it — or hydrophilic — water clings to it. The coating on this leaf is hydrophobic, so water beads-up and wants to run off the leaf. (Source: https://scitechdaily.com/more-efficient-thermal-cooling-method-bioinspired-by-plants/amp/)
16/ The fibers in jeans are hydrophilic, so if you go snow skiing you get wet. That’s why, back in the day, we used Scotchgard on jeans to go skiing. Scotchgard is hydrophobic. It’s pretty much the same thing we sprayed into Shuttle tiles.
17/ Remember learning about a meniscus back in high school or college chemistry lab? It’s that curve of the water inside a glass container. That’s because glass is hydrophilic, so water loves it and wants to climb up the sides of the glass. Shuttle tile fibers are silica (glass).
18/ After installing the tiles, we could not get access to the uncoated parts of the tile to spray “Scotchgard” into each tile to keep the rain out, so they had to poke the little holes in the coating of each tile (in the little circles in this picture) to inject the spray. But…
19/ …now your gonna ask, why not just spray in the Scotchgard BEFORE installing the tiles, when we still had access to the uncoated parts near the base of each tile? Wouldn’t that be easier than injecting each tile one-by-one AFTER installation? Well…
20/ The problem was that the “Scotchgard” burns out of the tiles during that super hot re-entry. It was vaporized by the heat and then it escaped from the tiles the same way the air escaped. So we had to reinject it into every tile all over again before every flight.
21/ So we had hollow tiles for heat protection, high emissivity coating on the tiles, a gap in the coating to let the air out, Scotchgard for inside the tiles to keep the rain out, and tiny holes to spray the Scotchgard in after every landing before going back out to the pad. BUT
22/ There was still one problem. Sometimes the Shuttle came back from a mission, freshly burned-out from all its Scotchgard, and before it was towed back to the hangar a thunderstorm rolled in and the tiles got soaked full of water. Florida weather changes fast.
23/ So then we are back to square one: how do we get those tons of water to come back out of the hydrophilic tiles before spraying in the new Scotchgard? Heat lamps did not work. It just moved the water around the outside of the vehicle to the cold side, never leaving the tiles.
24/ I used to be a Space Shuttle comm/nav engineer and later became a physicist. My first physics project at NASA was to study how to get water out of the Space Shuttle tiles. I did experiments filling them with water and sucking it back out using a vacuum hose on the same holes.
25/ It was a really cool condensed matter project because the water droplets did a directed (but randomized) walk through the fibers, with denser fibers holding the water more tightly so it was diffusion thru random potential wells. It resulted in stretched exponential curves.
26/ In the end we used those results to help decide how long to suck on the tiles before removing the suction cups and moving on to the next batch of tiles. The system could suck the Shuttle dry in a few days, whereas heat lamps took months and still couldn’t get the water out.
27/ So when I look at Shuttle tiles I think of those 2 things: the white chevrons marking the comm/nav antennas which I worked on for 10 years as part of the launch team, then the tiny holes where we sucked water out after (later) becoming a physicist. Fond memories! /end
A minor correction on the STS tile waterproofing:Why can't the MTMS be used as rewaterproofing agent?
The tiles were initially impregnated with methyltrimethoxysilane (MTMS) during manufacture, and this provided waterproofing through to the first flight and entry, and which point the MTMS burnt off during entry. Subsequent to this, a rewaterproofing agent needed to be applied after every flight.
Initially, rewaterproofing was performed by spray-on fluoropolymer (Scotchguard), with the idea that it could be sprayed on rapidly after landing to minimise the chance of water ingress. This proved inadequate, as too much Scotchguard would interact with and degrade the Silicone used to adhere the gap-fillers between the tiles, and too little provided inadequate protection and led to water ingress into the tiles.
As a replacement for the Scotchguard, hexamethyldisilazane (HDMS) was applied through vapour diffusion, to provide good penetration into the tile. As a rewaterproofing agent it worked well, but it was found the catalyst used in the HDMS degraded the silicone under the base of the tile (that attached it to the Orbiter), meaning all treated tiles needed to be replaced and a new rewaterproofing agent found.
That new agent was dimethylethoxysilane (DMES), which needed to be injected rather than diffused into the tiles. This was laborious (poking a needle into each tile and injecting sly enough to not fracture the tile) but it worked and did not degrade the silicone, so was the rewaterproofing agent for the rest of the life of STS.
Manufacture of Starship's tiles impregnates them with MTMS during manufacture (as per the FDEP report (https://prodenv.dep.state.fl.us/DepNexus/public/electronic-documents/FLR000231449/facility!search) on the tile facility waste handling), with the rewaterproofing method currently unknown.
Having to re-waterproof the tiles between flights seems like a big hairy deal, if not a showstopper, for rapid reuse. I wonder if we won't see either a ceramic coating on the fibers or a change to the composition of the fibers which causes them to develop a hydrophobic surface.Yes. It looks to me that it kills truly rapid reuse, unless the inspection and re-waterproofing process can be fully automated. Starship's geometry is a lot simpler than the shuttle's, and automation has become much more sophisticated during the last 20 years, so it might be possible. I'm guessing that inspection and re-waterproofing can be automated but tile replacement will remain at least semi-manual for a long while.
OTOH if boiling or freezing water destroys tiles this would not help.Water ingress causes exactly this.
After the 2nd flight of Columbia inspection of the Orbiter indicated that in-plane failures of six HRSI tiles had
occurred on the right wing glove area. The depth of the missing material corresponded to the burnout zone of the
factory waterproofing or the 1050 F line. In addition, the surface coating of 12 tiles on the body flap showed
evidence of bubbling. Based on these observations and previous results from the ground test program, it was
concluded that water penetration had occurred on the tiles before the flight and the rewaterproofing application
technique required improvement. The mechanism involved in this failure is postulated as follows. Water from
rainstorms entered an area of the tiles before lift-off. During ascent, a small amount of water in the tile was
vaporized, and the remainder cooled rapidly because of the rapid decrease in pressure. When the vehicle went to
orbital conditions, the water changed to ice, which contracted and fractured the tile. The steam generated in the tile
during entry then completed the fracture of the tile.
Shuttle tiles fit extremely tightly together and were attached to the vehicle with adhesive.The fracturing was internal to the tile, attachment method or abutment would be irrelevant to that failure mechanism.
Most Starship tiles have a deliberate inter tile gap to allow thermal expansion and are attached with mechanical devices whose retention force and range and spring constant of "play" can be defined as necessary. This scheme likely tolerates freezing and boiling of intruding moisture and resultant stress on individual tiles much better than the orbiter's.
Starship has a lower surface area/volume ratio than the shuttle because it is larger and has a more compact shape.
If the weight of absorbed water is the only problem SS may be able to dispense with waterproofing, or accept imperfect waterproofing. This would be particularly true for tanker flights since these have excess fuel that could be used to adjust for an unknown mass of absorbed water.
OTOH if boiling or freezing water destroys tiles this would not help.
Not following your Challenger bit. What freezing damage was hidden during a Challenger (OV-099) flight?Starship has a lower surface area/volume ratio than the shuttle because it is larger and has a more compact shape.
If the weight of absorbed water is the only problem SS may be able to dispense with waterproofing, or accept imperfect waterproofing. This would be particularly true for tanker flights since these have excess fuel that could be used to adjust for an unknown mass of absorbed water.
OTOH if boiling or freezing water destroys tiles this would not help.
If the tiles are that permeable, then boiling is probably irrelevant, it won't cause damage. At high enough altitude (> 60km) the moisture will boil off (or sublime if frozen), and thus only slightly impact Starship fuel usage since staging doesn't happen until about that altitude. The water mass will probably be there for the entire Booster burn but it's probably rounding error given Booster + full Starship is on the order of 1800 tons. I doubt 2 tons of water will matter, that's equivalent to a 1-2 engine outage on the Booster which is already planned for.
Freezing, OTOH. Fortunately, unlike Challenger, the damage will be obvious.
And since freezing happens every time we see a cryo test, my guess is, not a problem. Let's see what the shortest time between a BC rainstorm and cryotest is. Has this happened yet?
Not following your Challenger bit. What freezing damage was hidden during a Challenger (OV-099) flight?Starship has a lower surface area/volume ratio than the shuttle because it is larger and has a more compact shape.
If the weight of absorbed water is the only problem SS may be able to dispense with waterproofing, or accept imperfect waterproofing. This would be particularly true for tanker flights since these have excess fuel that could be used to adjust for an unknown mass of absorbed water.
OTOH if boiling or freezing water destroys tiles this would not help.
If the tiles are that permeable, then boiling is probably irrelevant, it won't cause damage. At high enough altitude (> 60km) the moisture will boil off (or sublime if frozen), and thus only slightly impact Starship fuel usage since staging doesn't happen until about that altitude. The water mass will probably be there for the entire Booster burn but it's probably rounding error given Booster + full Starship is on the order of 1800 tons. I doubt 2 tons of water will matter, that's equivalent to a 1-2 engine outage on the Booster which is already planned for.
Freezing, OTOH. Fortunately, unlike Challenger, the damage will be obvious.
And since freezing happens every time we see a cryo test, my guess is, not a problem. Let's see what the shortest time between a BC rainstorm and cryotest is. Has this happened yet?
Shuttle tiles fit extremely tightly together and were attached to the vehicle with adhesive.Shuttle tiles were spaced apart to allow for thermal expansion during entry and had gap fillers fitted which made the tile surface look smooth from a distance.
Most Starship tiles have a deliberate inter tile gap to allow thermal expansion and are attached with mechanical devices whose retention force and range and spring constant of "play" can be defined as necessary. This scheme likely tolerates freezing and boiling of intruding moisture and resultant stress on individual tiles much better than the orbiter's.
Could they ensure that Starship is kept sheltered before launch to prevent the absorption of rain? I know it would be a massive undertaking but it should at least theoretically be possible to have some sort of movable structure to keep the rain off. It can't be that much more crazy than ideas like using chopsticks to snatch a Starship out of the air.A baggie. A really big baggie.
Minotaur has something like that - the first stage sheds what looks like a shrink-wrapped plastic skin at launch time.Could they ensure that Starship is kept sheltered before launch to prevent the absorption of rain? I know it would be a massive undertaking but it should at least theoretically be possible to have some sort of movable structure to keep the rain off. It can't be that much more crazy than ideas like using chopsticks to snatch a Starship out of the air.A baggie. A really big baggie.
I was trying to be funny, but I do note that the chopsticks could probably be used to to install the baggie. Not sure how to keep moisture from condensing into/onto the tiles during cryogenic propellant loading, though.Minotaur has something like that - the first stage sheds what looks like a shrink-wrapped plastic skin at launch time.Could they ensure that Starship is kept sheltered before launch to prevent the absorption of rain? I know it would be a massive undertaking but it should at least theoretically be possible to have some sort of movable structure to keep the rain off. It can't be that much more crazy than ideas like using chopsticks to snatch a Starship out of the air.A baggie. A really big baggie.
Given that this has been a known issue since before the start of the program, it's literally a "bet the company" program, and SpaceX almost certainly has former STS heat shield experts on staff, I think "I don't know how we'll avoid re-waterproofing 18k tiles after every flight" is not something they're saying in the offices at Boca Chica. I suspect the issue was resolved before the first Starbrick (not "tile") left the Bakery.
Given that this has been a known issue since before the start of the program, it's literally a "bet the company" program, and SpaceX almost certainly has former STS heat shield experts on staff, I think "I don't know how we'll avoid re-waterproofing 18k tiles after every flight" is not something they're saying in the offices at Boca Chica. I suspect the issue was resolved before the first Starbrick (not "tile") left the Bakery.
Given that this has been a known issue since before the start of the program, it's literally a "bet the company" program, and SpaceX almost certainly has former STS heat shield experts on staff, I think "I don't know how we'll avoid re-waterproofing 18k tiles after every flight" is not something they're saying in the offices at Boca Chica. I suspect the issue was resolved before the first Starbrick (not "tile") left the Bakery.
Quite. Although I would say maybe not completely resolved, but certainly a long way to the end goal. I would certainly think that some of the commentators here worrying about it should definitely consider that they may not be the experts here.
Given that this has been a known issue since before the start of the program, it's literally a "bet the company" program, and SpaceX almost certainly has former STS heat shield experts on staff, I think "I don't know how we'll avoid re-waterproofing 18k tiles after every flight" is not something they're saying in the offices at Boca Chica. I suspect the issue was resolved before the first Starbrick (not "tile") left the Bakery.
Quite. Although I would say maybe not completely resolved, but certainly a long way to the end goal. I would certainly think that some of the commentators here worrying about it should definitely consider that they may not be the experts here.
Given that this has been a known issue since before the start of the program, it's literally a "bet the company" program, and SpaceX almost certainly has former STS heat shield experts on staff, I think "I don't know how we'll avoid re-waterproofing 18k tiles after every flight" is not something they're saying in the offices at Boca Chica. I suspect the issue was resolved before the first Starbrick (not "tile") left the Bakery.
Quite. Although I would say maybe not completely resolved, but certainly a long way to the end goal. I would certainly think that some of the commentators here worrying about it should definitely consider that they may not be the experts here.
Ok. No commenting on anything unless you're a SpaceX engineer then. Time to shut down NSF... ::)
Tiles currently installed are impregnated ::)
Both: the EPA document revealed they are doing it 'the shuttle way' - MTMS impregnation during manufacture.Tiles currently installed are impregnated ::)
I forgot, is that a guess based on EPA/MSDS disclosures from the Florida facility, or is it a "the shuttle did it that way" guess? And the water repellent applies to *all* the surfaces? (I don't know).
SuperWool blankets have a water absorption ratiing of ~20% by weight. there's on the order of 750m^2 of tile (pi*4.5*50) backed by wool.It's unknown what the batting composition is (superwool, kaowool, and other ASF & RCF products have been assumed, but no confirmation), but waterproofing impregnation could be done at manufacture or post manufacture, and like the tiles would need rewaterproofing after exposure to elevated temperatures.
Assuming iit's 50mm superwool that's 37.5 cubic meters of superwool, at 128kg/m^3 = 4.8T of superwool, or about 1T of water absorbed. Rounding error for the first 3 minutes of flight.
All that wool was wide open to the rain for numerous cryotests. Didn't seem to bother anything as far as freezing goes.
So, why are tiles different than the superwool?
https://www.goodfellow.com/DocumentHandler/177/superwool-ht.pdf?download=1
https://pure.strath.ac.uk/ws/portalfiles/portal/90853154/Edet_etal_Electrochem_2019_Poster_Investigation_of_water_absorption_profile_of_mineral_wool.pdf
elon musk states in recent everyday astronaut video that the tiles will expand and fill the gaps, so should be no problem for hot gas entry between tiles, I think he got that one wrong, I remember when I was researching a bit on the shuttle tiles one reason the material was so suitable was the lack of thermal expansion, I wont be bothered going back to find the data, if others want to debate it the info is out there, but expansion should be negligible.Expansion at gaps aide, the hazards associated with gaps are substantially different for shuttle & Starship. The thermal resilience of the orbiter's aluminum (7075?) skin was dramatically lower than is expected for Starship's 304L stainless steel.
I wonder if they are now thinking about using a deliberate internal Impulse ("boom") as a way to test the tiles. Does it just shake off loose tiles, or does it loosen tiles that are otherwise tight? If it works, it allows a single test to test all the tiles instead of requiring individual testing.elon musk states in recent everyday astronaut video that the tiles will expand and fill the gaps, so should be no problem for hot gas entry between tiles, I think he got that one wrong, I remember when I was researching a bit on the shuttle tiles one reason the material was so suitable was the lack of thermal expansion, I wont be bothered going back to find the data, if others want to debate it the info is out there, but expansion should be negligible.Expansion at gaps aide, the hazards associated with gaps are substantially different for shuttle & Starship. The thermal resilience of the orbiter's aluminum (7075?) skin was dramatically lower than is expected for Starship's 304L stainless steel.
Personally, what I'm more concerned with, at this late date in SS iterations, is how easy it seems to be for the tiles to shake loose.
Given that this has been a known issue since before the start of the program, it's literally a "bet the company" program, and SpaceX almost certainly has former STS heat shield experts on staff, I think "I don't know how we'll avoid re-waterproofing 18k tiles after every flight" is not something they're saying in the offices at Boca Chica. I suspect the issue was resolved before the first Starbrick (not "tile") left the Bakery.
Quite. Although I would say maybe not completely resolved, but certainly a long way to the end goal. I would certainly think that some of the commentators here worrying about it should definitely consider that they may not be the experts here.
Ok. No commenting on anything unless you're a SpaceX engineer then. Time to shut down NSF... ::)
Way to miss the point. There are too many people on here saying, in effect, "That will never work". I have no problem with commenting, but I do have a problem with people thinking they know better than SpaceX. That's offensive to the engineers at SpaceX, who they are effectively calling incompetent.
Didn't everybody already knows the whole S24 pipe coming lose? It's really not a tile problemselon musk states in recent everyday astronaut video that the tiles will expand and fill the gaps, so should be no problem for hot gas entry between tiles, I think he got that one wrong, I remember when I was researching a bit on the shuttle tiles one reason the material was so suitable was the lack of thermal expansion, I wont be bothered going back to find the data, if others want to debate it the info is out there, but expansion should be negligible.Expansion at gaps aide, the hazards associated with gaps are substantially different for shuttle & Starship. The thermal resilience of the orbiter's aluminum (7075?) skin was dramatically lower than is expected for Starship's 304L stainless steel.
Personally, what I'm more concerned with, at this late date in SS iterations, is how easy it seems to be for the tiles to shake loose.
Not sure. I've raised this with SpaceX indirectly and this observation is part of a design hold point until actual flights provide information on behavior of the tiles at launch and subsequent speeds. Redesign would be a major delay. Shuttle tiles did not have cryogenics in the tank behind them. The tiles on the Shuttle were also sealed with both woven fiberglass caulking strips and silicone sealant to mitigate weather and plasma intrusion as u/flshr19 will confirm.
Secondly, I'm not happy with the bayonet fittings or 'tile pins' holding the tile on. They are like a steel rawlplug with one way toothed ridging that requires destruction to remove the tile. Still, the anchor sockets in the tile rip out still attached to the bayonet fitting and the tile falls off.
There is another product on the market, and I won't promote it but if you want to see it it is here which is like steel velcro and probably better suited to thermal heating and tile replacement.
Going forward, the current tiles are the best and lightest thermal cladding available. Metallic forms carry a severe weight penalty, so it is up to the design team to finesse their tile, anchor points, reinforcing mesh, and felt insulation for all weather, all heat load situations.
Early in the shuttle's history, NASA discovered that the porous tiles tended to suck up moisture like a sponge, then crack in the freezing void of space.
Shuttle tiles did not have cryogenics in the tank behind them. The tiles on the Shuttle were also sealed with both woven fiberglass caulking strips and silicone sealant to mitigate weather and plasma intrusion as u/flshr19 will confirm.
Secondly, I'm not happy with the bayonet fittings or 'tile pins' holding the tile on. They are like a steel rawlplug with one way toothed ridging that requires destruction to remove the tile. Still, the anchor sockets in the tile rip out still attached to the bayonet fitting and the tile falls off.
There is another product on the market, and I won't promote it but if you want to see it it is here which is like steel velcro and probably better suited to thermal heating and tile replacement.
Going forward, the current tiles are the best and lightest thermal cladding available. Metallic forms carry a severe weight penalty, so it is up to the design team to finesse their tile, anchor points, reinforcing mesh, and felt insulation for all weather, all heat load situations.
This is the link to the "steel velcro" mentioned:
https://www.metaklett.de/en/technologie.html
Looks interesting.
Looks interesting but how do you peel a rigid item? See the pictures on the mfgr's website. All velcro I know about involves a bend radius for removal. Ceramics and glass have zero bend radius. the steel velcro probably doesn't have the degrees of freedom that the triple bayonet system has, so will be more rigid and promote cracking.
I think the OP's thought was that this steel velcro *would provide enough degrees of freedom. The advantages I see in this method of tile placement is 1 - probably simpler to install, and 2 - less thermal penetration (no thermal path like the exisiting pins).
As far as removing them, presumably it would be the same (why remove a tile if it isn't broken?) and if it's broken anyway, perhaps you could peel it off from the back.
If the plan is to use the mfgrs steel-steel mode you well get far more thermal coupling than three pins. The mfgr calls this "Etenkopf" configuration.
[snip]
https://www.metaklett.de/en/technologie.html
It's unknown what the batting composition is (superwool, kaowool, and other ASF & RCF products have been assumed, but no confirmation), but waterproofing impregnation could be done at manufacture or post manufacture, and like the tiles would need rewaterproofing after exposure to elevated temperatures.
It's unknown what the batting composition is (superwool, kaowool, and other ASF & RCF products have been assumed, but no confirmation), but waterproofing impregnation could be done at manufacture or post manufacture, and like the tiles would need rewaterproofing after exposure to elevated temperatures.
We know from observation that they are taking no safety precautions when handling the "felt blanket".
We also know that it needs to have a useful temperature in excess of 750degC.
This considerably narrows the choices down to... superwool.
Superwool: Human safe, working temperature 1300degC
Kaowool: can cause cancer from fine particles: 1100 degC
Other ASF&RFC products: Many cause cancer or severe lung irritation. Cite one that doesn't.
http://www.lloyd-ris.co.uk/pdfs/datasheets/607%20Products%20MSDS.pdf
https://www.insulationindustries.com.au/wp-content/uploads/2022/05/MSDS_-_Kaowool_Blanket_and_Bulk_Products.pdf
It's unknown what the batting composition is (superwool, kaowool, and other ASF & RCF products have been assumed, but no confirmation), but waterproofing impregnation could be done at manufacture or post manufacture, and like the tiles would need rewaterproofing after exposure to elevated temperatures.
We know from observation that they are taking no safety precautions when handling the "felt blanket".
We also know that it needs to have a useful temperature in excess of 750degC.
This considerably narrows the choices down to... superwool.
Superwool: Human safe, working temperature 1300degC
Kaowool: can cause cancer from fine particles: 1100 degC
Other ASF&RFC products: Many cause cancer or severe lung irritation. Cite one that doesn't.
http://www.lloyd-ris.co.uk/pdfs/datasheets/607%20Products%20MSDS.pdf
https://www.insulationindustries.com.au/wp-content/uploads/2022/05/MSDS_-_Kaowool_Blanket_and_Bulk_Products.pdf
My money is on an alumina fiber product like Saffil. Its good to 1650 C, ~3000 F.
John
Based on the preponderance of evidence, I believe SpaceX has completely abandoned any waterproofing on tiles and the heat shield in general, including scotch-guard or other water proofing chemicals.The tile cracking caused by water-impregnated tiles undergoing freeze/sublimation/boil cycles duringascent & descent is independent of attachment mechanism. A tile floating freely unattached to any vehicle would have the same issues.
From WaPo articleQuoteEarly in the shuttle's history, NASA discovered that the porous tiles tended to suck up moisture like a sponge, then crack in the freezing void of space.
The other way to solve expansion/contraction problems from changes caused by freezing water is loose mechanical tolerances.
Space Shuttle did not have loose mechanical tolerances. That wasn't the design philosophy and you can't do that with aluminum or the materials available for backing in the 1970s. The tiles were packed together and sealed, leaving little room for expansion that occurs when water freezes.
SpaceX, OTOH, has loose tolerances all over the place - in the super-wool padding, in the bayonet fastener, and between the tiles. The padding deals with any plasma leaks resulting from those loose tolerances, as well as a skin that can handle 750degC.
They have already tested freezing in live testing, via cryogenic testing after the Starship getting wet. What remains to prove is whether or not the tiles and padding were waterpoofed. They *could* have been, but based on the design approach I don't think they are using the waterproofing they have on their MSDS disclosures.
Can't think of another way to find out (on our end) other than an updated disclosure form from the Florida facility, insider gossip, or a reflown Starship that has sat out in the weather.
https://www.washingtonpost.com/wp-srv/articles/A38144-2003Feb6.html
What I wonder is what is the time scale for how long the tiles can sit without rewaterproofing before it becomes a problem? Hours, days, or weeks?Based on the preponderance of evidence, I believe SpaceX has completely abandoned any waterproofing on tiles and the heat shield in general, including scotch-guard or other water proofing chemicals.The tile cracking caused by water-impregnated tiles undergoing freeze/sublimation/boil cycles duringascent & descent is independent of attachment mechanism. A tile floating freely unattached to any vehicle would have the same issues.
From WaPo articleQuoteEarly in the shuttle's history, NASA discovered that the porous tiles tended to suck up moisture like a sponge, then crack in the freezing void of space.
The other way to solve expansion/contraction problems from changes caused by freezing water is loose mechanical tolerances.
Space Shuttle did not have loose mechanical tolerances. That wasn't the design philosophy and you can't do that with aluminum or the materials available for backing in the 1970s. The tiles were packed together and sealed, leaving little room for expansion that occurs when water freezes.
SpaceX, OTOH, has loose tolerances all over the place - in the super-wool padding, in the bayonet fastener, and between the tiles. The padding deals with any plasma leaks resulting from those loose tolerances, as well as a skin that can handle 750degC.
They have already tested freezing in live testing, via cryogenic testing after the Starship getting wet. What remains to prove is whether or not the tiles and padding were waterpoofed. They *could* have been, but based on the design approach I don't think they are using the waterproofing they have on their MSDS disclosures.
Can't think of another way to find out (on our end) other than an updated disclosure form from the Florida facility, insider gossip, or a reflown Starship that has sat out in the weather.
https://www.washingtonpost.com/wp-srv/articles/A38144-2003Feb6.html
If SpaceX does not rewaterproof tiles (and does not immediately place a landed Starship in a desiccating environment until liftoff, because atmospheric moisture exists regardless of inclement weather) then the tiles will need to be considered single-use items. Rewaterproofing is not optional.
What I wonder is what is the time scale for how long the tiles can sit without rewaterproofing before it becomes a problem? Hours, days, or weeks?I still think they can take a (ahem) prophylactic approach and cover the Starship in a thin flexible conformal sheath each time it lands, which can be filled if needed with dry nitrogen.
If it's days or longer, then they might be working with the specification that "well, we'll be doing rapid relaunch, so it's not a problem."
After all, shuttle was exposed to humidity for a much longer time between launches.
It will take them years to get to that launch cadence but they're not going to keep any of the existing starships anyway, and it'll probably be years before they have a finalized design. So until then, as long as they aren't carrying any downmass, losing a starship on decent is acceptable (and instructive).
After all, shuttle was exposed to humidity for a much longer time between launches.The Orbiter also had the tiles re-waterproofed.
After all, shuttle was exposed to humidity for a much longer time between launches.The Orbiter also had the tiles re-waterproofed.
And in events where rain occurred before the Orbiter could be brought under cover and re-waterproofing performed, a protracted drying period of weeks was required to drive out the absorbed moisture.
So, SpaceX need to develop a waterproof tile that doesn't suffer this fate. Have they already done this? Seems like it would be high on the development schedule as its pretty much needed for high turnaround reusability. Is everyone assuming they haven't bothered or forgot to think about this?
I'm in the midst of 2-3 pages of google search results, and nothing indicates that there's a problem with taking an untreated tile, soaking it in water, and throwing in the freezer. Just that tiles "pop off" the shuttle, which could be from internal fractures or low tolerances.See my post on the previous page of this thread, linking to the relevant document and quoting the relevant section (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2373374#msg2373374). The issue is nothing to do with tile attachment, the failure occurs within the body of the tile.
So, SpaceX need to develop a waterproof tile that doesn't suffer this fate. Have they already done this? Seems like it would be high on the development schedule as its pretty much needed for high turnaround reusability. Is everyone assuming they haven't bothered or forgot to think about this?
It's unknown what the batting composition is (superwool, kaowool, and other ASF & RCF products have been assumed, but no confirmation), but waterproofing impregnation could be done at manufacture or post manufacture, and like the tiles would need rewaterproofing after exposure to elevated temperatures.
We know from observation that they are taking no safety precautions when handling the "felt blanket".
We also know that it needs to have a useful temperature in excess of 750degC.
This considerably narrows the choices down to... superwool.
Superwool: Human safe, working temperature 1300degC
Kaowool: can cause cancer from fine particles: 1100 degC
Other ASF&RFC products: Many cause cancer or severe lung irritation. Cite one that doesn't.
http://www.lloyd-ris.co.uk/pdfs/datasheets/607%20Products%20MSDS.pdf
https://www.insulationindustries.com.au/wp-content/uploads/2022/05/MSDS_-_Kaowool_Blanket_and_Bulk_Products.pdf
My money is on an alumina fiber product like Saffil. Its good to 1650 C, ~3000 F.
John
Nice find!
Saffil: Human safe, working temperature 1650C (looks to be as safe or safer than Superwool)
MSDS: https://www.unifrax.com/wp-content/uploads/2018/08/Unifrax-SDS-Saffil-V2.00-GB-en-160811.pdf
product brief: http://www.lloyd-ris.co.uk/pdfs/datasheets/saffil%20blanket%5B1%5D.pdf
and a general overview of related material: https://www.unifrax.com/product-category/blankets/?productcategory=236
I'm in the midst of 2-3 pages of google search results, and nothing indicates that there's a problem with taking an untreated tile, soaking it in water, and throwing in the freezer. Just that tiles "pop off" the shuttle, which could be from internal fractures or low tolerances.See my post on the previous page of this thread, linking to the relevant document and quoting the relevant section (https://forum.nasaspaceflight.com/index.php?topic=50748.msg2373374#msg2373374). The issue is nothing to do with tile attachment, the failure occurs within the body of the tile.
Originally it was intended that the re-waterproofing needed to
be completed quickly for turnaround activities so spray on type materials were investigated as the factory
waterproofing burns out at temperatures above 1050 F. The first spray that was used was a fluro-polymer or
Scotchgard, which provided a thin film of low surface energy on the exterior surface of the tile glass coating. It was
recognized that this treatment would not provide an impervious barrier to water and that its effects would be highly
dependent on the surface tension of the water and resultant contact angle.
After the 2nd flight of Columbia inspection of the Orbiter indicated that in-plane failures of six HRSI tiles had
occurred on the right wing glove area. The depth of the missing material corresponded to the burnout zone of the
factory waterproofing or the 1050 F line. In addition, the surface coating of 12 tiles on the body flap showed
evidence of bubbling.
To eliminate tile fracturing while the vehicle was on orbit the attitude was changed to provide a
favorable Sun attitude to drive out the water before ice damage could occur. The activity proved successful as post
flight evaluations revealed that no tiles underwent fracturing.
This why I maintain that Starship's true "heat" shield is the "felt backing" (probably Saffil). The tiles are there to hold on the backing and for a high emissivity to take maximum advantage of Stefan-Boltzmann.The 'true' heatshield is the thin borosilciate glass coating on the outer surface of the tiles. That is what radiates the majority of incoming energy from entry away from the vehicle again, and resists the chemical attach from the ionised atmosphere molecules in the entry plasma (e.g. superheated oxygen). The sintered silica tile body that the glass is coated onto supports that coating with low mass (lower than a solid glass sheet of comparable strength) and reduced conduction from the backside of that high temperature glass coating to the vehicle. The mats behind the tiles provide some mechanical isolation to the tile body, and allows the pin latching mechanism to work (needs to push 'in' slightly further than the final latched position in order to latch), and allows the tile backside surface to not need to be exactly conformal the the tank wall - i.e. the backside can be flat rather than a hollow sphere or cylinder section. Without that outer glass layer, the rest of the materials would be exposed to a much total higher energy, would absorb a dramatically higher proportion of that energy, and be under attack from high energy particles attempting to decompose the insulating fibres.
This why I maintain that Starship's true "heat" shield is the "felt backing" (probably Saffil). The tiles are there to hold on the backing and for a high emissivity to take maximum advantage of Stefan-Boltzmann.The 'true' heatshield is the thin borosilciate glass coating on the outer surface of the tiles. That is what radiates the majority of incoming energy from entry away from the vehicle again, and resists the chemical attach from the ionised atmosphere molecules in the entry plasma (e.g. superheated oxygen). The sintered silica tile body that the glass is coated onto supports that coating with low mass (lower than a solid glass sheet of comparable strength) and reduced conduction from the backside of that high temperature glass coating to the vehicle. The mats behind the tiles provide some mechanical isolation to the tile body, and allows the pin latching mechanism to work (needs to push 'in' slightly further than the final latched position in order to latch), and allows the tile backside surface to not need to be exactly conformal the the tank wall - i.e. the backside can be flat rather than a hollow sphere or cylinder section. Without that outer glass layer, the rest of the materials would be exposed to a much total higher energy, would absorb a dramatically higher proportion of that energy, and be under attack from high energy particles attempting to decompose the insulating fibres.
For Starship, it does not apply to every square inch. A few missing tiles cracked from being frozen while full of water (which is all the Space Shuttle ever experienced) is a non-event, because of layered defense.Often asserted, yet to be proven. If heating of the stainless structure reduced strength beyond the minimum required, the tank will fail, and potentially the vehicle (due to semiballoon construction). That temperature is higher than that which would cause damage to the STS orbiter, but remains lower than the temperatures reached during EDL (or no TPS would be required in the first place). And because someone will probably bring up the STS-27 missing tile: That area had a substantial thickness of Aluminium behind it (~5mm Aluninium access panel, gapped over the Aluminium structure itself), rather than the ~3mm Stainless single-layer tank skin of Starship.
Thus, SpaceX, as clearly shown by their operations, doesn't care whether Starship gets wet, and doesn't care very much about water proofing tiles.This assertion does not follow even if a single or small number of tile failures is tolerable: tile failure from water intrusion is a known failure mode. Absence of re-waterproofing is not going to affect a handful of isolated tiles, it will affect all tiles.
This why I maintain that Starship's true "heat" shield is the "felt backing" (probably Saffil). The tiles are there to hold on the backing and for a high emissivity to take maximum advantage of Stefan-Boltzmann.The 'true' heatshield is the thin borosilciate glass coating on the outer surface of the tiles. That is what radiates the majority of incoming energy from entry away from the vehicle again, and resists the chemical attach from the ionised atmosphere molecules in the entry plasma (e.g. superheated oxygen). The sintered silica tile body that the glass is coated onto supports that coating with low mass (lower than a solid glass sheet of comparable strength) and reduced conduction from the backside of that high temperature glass coating to the vehicle. The mats behind the tiles provide some mechanical isolation to the tile body, and allows the pin latching mechanism to work (needs to push 'in' slightly further than the final latched position in order to latch), and allows the tile backside surface to not need to be exactly conformal the the tank wall - i.e. the backside can be flat rather than a hollow sphere or cylinder section. Without that outer glass layer, the rest of the materials would be exposed to a much total higher energy, would absorb a dramatically higher proportion of that energy, and be under attack from high energy particles attempting to decompose the insulating fibres.
q_insulation = k_insulation *(Toutside -Tinside)/thickness = SB_constant*emitter_constant*Tinside^4
Sadly EDL behaviour is not that simple to model. As well as radiant heating, you also have hot gas diffusion and catalytic heating, and the proportion and energy of each will vary with velocity and altitude. Unlike the glass coating, fibre mats (and particularly flexible fibre mats) are highly porous, can have fibres that are mobile (i.e. move around when gas impinges on them) and have an extremely high surface area for a given mass. That surface area works directly against you for the chemical effects in particular: if your saffil mat reacts and erodes faster than it can heart up, it's not able to do its job of reducing thermal conductivity.
The obvious question you should be asking yourself is why SpaceX are not just covering Starahip - or anyone else covering any other vehicle for that matter, the product being over half a century old - with secured-in-place mats. Because if the tiles are just providing an aerosurface or just holding the mats on, there are lighter and less complex methods than RCG-coated sintered-silica tiles.
Radiative transfer alone is not sufficient to model re-entry.
1. 3x-5x less heat transfer into the interior of Starship so as to not boil off all the starship fuel. I have yet to calculate how much heat flux Starsip can actually handle into the interior and not boil everything off, this might be a minor deal or a big deal.On entry, the main tank volumes will be empty of liquids, and at moderate gas pressure required for structural stability.
2. Secure the mats. Whatever method secures the mats has to be light, strong, and withstand 1300degC+, and withstand more air movement than the mats can.. We've investigated what materials can do that in threads far above, there's nothing lighter than coated sintered tiles that we could find (or SpaceX for that matter)The fibres the non-woven matting are made from can be woven into fibres, and used to stitch to backside support posts (e.g. the existing clip stanchions). This is how existing heatproof blankets are mounted.
There's also the fact that modern human-safe high temp insulation exists now, and it didn't prior to about 1976 or so (more widely late 1980s)Saffil mat dates from the early 70s.
The obvious question you should be asking yourself is why SpaceX are not just covering Starahip - or anyone else covering any other vehicle for that matter, the product being over half a century old - with secured-in-place mats. Because if the tiles are just providing an aerosurface or just holding the mats on, there are lighter and less complex methods than RCG-coated sintered-silica tiles.
Radiative transfer alone is not sufficient to model re-entry.
The obvious question you should be asking yourself is why SpaceX are not just covering Starahip - or anyone else covering any other vehicle for that matter, the product being over half a century old - with secured-in-place mats. Because if the tiles are just providing an aerosurface or just holding the mats on, there are lighter and less complex methods than RCG-coated sintered-silica tiles.
Radiative transfer alone is not sufficient to model re-entry.
TBE Shuttle leeward side was covered by mats (but very different from Saffil) and they were handling temperatures stainless steel is supposed to handle uncovered.
Also various inflatable heat shield prototypes were made from fabric not tiles. And they were supposed to handle re-entry "head on" so with temperatures around 1200°C
Related note: a pin attachment allows for quick-and-easy replacement of tiles, but there's no provision for repairing the mat. Surely we can't assume mats never need repairing? What if a tile is lost on ascent and the mat has to deal with the full heat flux on return?
I wonder how big the mats are, and how they deal with the seams. If mat repairs are tolerable, then bond the tile, and replace its mat too when needed. But if you have to replace mats seam to seam that'll involve a lot of tiles.
Perhaps one compromise is to produce large panels of tiles bonded to their underlying mat that can be replaced as a unit. A single panel design would cover a lot of the area...
That was my guess too. And the SpaceX MO is to try the ideal method first to see if that works as is, i.e. "can we just slap on a new tile when one's needed?" But the pin attachments we've seen so far are clearly not working that well.
I'd say the pins are working well if all tiles stay firmly attached during all normal spacecraft operations, starting with static fire.I'd say the tiles are working well if a minor sudden internal overpressure event ("THUMP") fails to dislodge any tiles. We saw such an event on S24, apparently accidentally induced, and some tiles fell off. Maybe they should do it on purpose.
I'd say the pins are working well if all tiles stay firmly attached during all normal spacecraft operations, starting with static fire.I'd say the tiles are working well if a minor sudden internal overpressure event ("THUMP") fails to dislodge any tiles. We saw such an event on S24, apparently accidentally induced, and some tiles fell off. Maybe they should do it on purpose.
Clearly, if they want to use a deliberate "thump" to test the tiles they will find a non-destructive way to do it.If speculation that this was a header tank autogenous pressurisation line failure is correct this would hardly be a minor event. Rather than overpressure damage it was more likely the result of the pipe whipping the the vehicle side.I'd say the pins are working well if all tiles stay firmly attached during all normal spacecraft operations, starting with static fire.I'd say the tiles are working well if a minor sudden internal overpressure event ("THUMP") fails to dislodge any tiles. We saw such an event on S24, apparently accidentally induced, and some tiles fell off. Maybe they should do it on purpose.
Because bonding them is intrinsically harder for maintenance than pins. That seems like enough answer by itself, doesn’t it?They already bond the tiles on the nose, flap edges, flap base, joints between ring segments, etc.
Only if there are any 'thump' sources that are liable to occur without more critical damage. e.g. the header tank line failure would have already been a loss-of-vehicle failure due to not having a header tank available for the landing burn, regardless of tile condition.If speculation that this was a header tank autogenous pressurisation line failure is correct this would hardly be a minor event. Rather than overpressure damage it was more likely the result of the pipe whipping the the vehicle side.Clearly, if they want to use a deliberate "thump" to test the tiles they will find a non-destructive way to do it.
Because bonding them is intrinsically harder for maintenance than pins. That seems like enough answer by itself, doesn’t it?They already bond the tiles on the nose, flap edges, flap base, joints between ring segments, etc.
Bonding tiles is known to work (flight proven on STS), <snip>
IF they chose to do a deliberate "thump" (an idle armchair idea, not something SpaceX ever mentioned) then it would use a carefully engineered system that has little risk of damage. It might be designed for use only during the manufacturing test, or to be used after any tile work during refurbishment, or even used each time the tanks are filled. As much as possible of the mass of the system would be on the ground, not in the Starship.Only if there are any 'thump' sources that are liable to occur without more critical damage. e.g. the header tank line failure would have already been a loss-of-vehicle failure due to not having a header tank available for the landing burn, regardless of tile condition.If speculation that this was a header tank autogenous pressurisation line failure is correct this would hardly be a minor event. Rather than overpressure damage it was more likely the result of the pipe whipping the the vehicle side.Clearly, if they want to use a deliberate "thump" to test the tiles they will find a non-destructive way to do it.
You missed my point: what potential sources of a 'thump' exist that would not otherwise result in LoV or LoM? Or in other words, is this a scenario that needs to be tested for in the first place?IF they chose to do a deliberate "thump" (an idle armchair idea, not something SpaceX ever mentioned) then it would use a carefully engineered system that has little risk of damage. It might be designed for use only during the manufacturing test, or to be used after any tile work during refurbishment, or even used each time the tanks are filled. As much as possible of the mass of the system would be on the ground, not in the Starship.Only if there are any 'thump' sources that are liable to occur without more critical damage. e.g. the header tank line failure would have already been a loss-of-vehicle failure due to not having a header tank available for the landing burn, regardless of tile condition.If speculation that this was a header tank autogenous pressurisation line failure is correct this would hardly be a minor event. Rather than overpressure damage it was more likely the result of the pipe whipping the the vehicle side.Clearly, if they want to use a deliberate "thump" to test the tiles they will find a non-destructive way to do it.
They already bond the tiles on the nose, flap edges, flap base, joints between ring segments, etc.
Bonding tiles is known to work (flight proven on STS), but is messy, slow, and expensive both to install and to maintain. The pinned connections are intended to be faster, cheaper, and easier to install and maintain. Pins are used where they can (large areas of simply geometry) and not used where they can't. Time will tell whether the pins achieve their design goals, but adhesive remains as a fallback option if necessary - albeit an undesirable one - but continued iteration on the pin system is more likely.
Except tiles were never bonded to a cryogenic tank on STS. This is new territory...
Do we know how the pins have been mechanically attached to the tiles to date? I've read a few guesses but nothing definitive.
The tiles appear to be just as brittle as those on the Shuttle, so spreading the connecting load over much of the tiles interior seems necessary.
...Bench-testing pin attachments with representative loads seems pretty easy, so it's unclear why they're installing a design that falls of the test vehicles during static fires, etc. My only guess is they want practice at acreage installation right now, knowing the pin/tile design will need to change.
Do we know how the pins have been mechanically attached to the tiles to date? I've read a few guesses but nothing definitive.
The tiles appear to be just as brittle as those on the Shuttle, so spreading the connecting load over much of the tiles interior seems necessary.
...Bench-testing pin attachments with representative loads seems pretty easy, so it's unclear why they're installing a design that falls of the test vehicles during static fires, etc. My only guess is they want practice at acreage installation right now, knowing the pin/tile design will need to change.
If the pin attachment design needed to change, it would have by now. The "acreage" testing was done long ago, they've completed tiling multiple test vehicles and Starships, that have undergone full cryo testing, the test flights, etc. A few tiles getting damaged or falling off here and there does not warrant a complete redesign of the system. At worst it means a few specific areas might need tweaking.
Do we know how the pins have been mechanically attached to the tiles to date? I've read a few guesses but nothing definitive.
The tiles appear to be just as brittle as those on the Shuttle, so spreading the connecting load over much of the tiles interior seems necessary.
...Bench-testing pin attachments with representative loads seems pretty easy, so it's unclear why they're installing a design that falls of the test vehicles during static fires, etc. My only guess is they want practice at acreage installation right now, knowing the pin/tile design will need to change.
If the pin attachment design needed to change, it would have by now. The "acreage" testing was done long ago, they've completed tiling multiple test vehicles and Starships, that have undergone full cryo testing, the test flights, etc. A few tiles getting damaged or falling off here and there does not warrant a complete redesign of the system. At worst it means a few specific areas might need tweaking.
I think you maybe wrong with the idea, that if there needs to be changes it would have been done by now. Starship has not gone through a full stack static fire, reached LEO or attempted a re-entry.
SpaceX is always trying to find the minimal viable product. I think they maybe busy with everything needed to reach orbit and may also be waiting to see it this design works and when things fail, if they fail, before putting resources in the heatshield.
S24 is likely highly instrumented and if there are problems SpaceX will know exactly what forces create it and they can adapt to that.
I think they will get it all sorted but that the heatshield is the single biggest risk item to the success of this project.
Do we know how the pins have been mechanically attached to the tiles to date? I've read a few guesses but nothing definitive.
The tiles appear to be just as brittle as those on the Shuttle, so spreading the connecting load over much of the tiles interior seems necessary.
...Bench-testing pin attachments with representative loads seems pretty easy, so it's unclear why they're installing a design that falls of the test vehicles during static fires, etc. My only guess is they want practice at acreage installation right now, knowing the pin/tile design will need to change.
If the pin attachment design needed to change, it would have by now. The "acreage" testing was done long ago, they've completed tiling multiple test vehicles and Starships, that have undergone full cryo testing, the test flights, etc. A few tiles getting damaged or falling off here and there does not warrant a complete redesign of the system. At worst it means a few specific areas might need tweaking.
I think you maybe wrong with the idea, that if there needs to be changes it would have been done by now. Starship has not gone through a full stack static fire, reached LEO or attempted a re-entry.
SpaceX is always trying to find the minimal viable product. I think they maybe busy with everything needed to reach orbit and may also be waiting to see it this design works and when things fail, if they fail, before putting resources in the heatshield.
S24 is likely highly instrumented and if there are problems SpaceX will know exactly what forces create it and they can adapt to that.
I think they will get it all sorted but that the heatshield is the single biggest risk item to the success of this project.
Then let me be very clear: none of the testing we have seen to date indicates the need for a tile attachment design change. The vast majority of heat shield tiles remained on the Starship, even in the very earliest tests when many were broken or fell off. During the most recent tests we have seen only a very few break or fall off. It's not a systemic problem.
I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Isn't it required, orbit or not?I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Well it's a minor concern right up to entry interface. If they get to that point they have proven a lot of things.
Getting Superheavy successfully off the ground and to MECO makes me anxious every time I think about it.
If they get into orbit then they can worry about the heatshield.
I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Minor? By far the most expensive aspect of the Space Shuttle was TPS maintenance. It consumed ~20,000 man-hours per flight.
John
I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Well it's a minor concern right up to entry interface. If they get to that point they have proven a lot of things.
Getting Superheavy successfully off the ground and to MECO makes me anxious every time I think about it.
If they get into orbit then they can worry about the heatshield.
We have seen shuttle tile install with installers standing on the ground.I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Minor? By far the most expensive aspect of the Space Shuttle was TPS maintenance. It consumed ~20,000 man-hours per flight.
John
Which is completely irrelevant to Starship. Their tiles are not made of the same material, are not installed in the same way, and are not 24,500 unique shapes. The game changer is the fact that over 90% of the Starship tiles are the exact same shape. We have seen Starship tile replacement done by people just going up in a scissor lift.
We have seen shuttle tile install with installers standing on the ground.I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Minor? By far the most expensive aspect of the Space Shuttle was TPS maintenance. It consumed ~20,000 man-hours per flight.
John
Which is completely irrelevant to Starship. Their tiles are not made of the same material, are not installed in the same way, and are not 24,500 unique shapes. The game changer is the fact that over 90% of the Starship tiles are the exact same shape. We have seen Starship tile replacement done by people just going up in a scissor lift.
Some are the same material.
The large acreage SS tiles are the same shape, which of course has advantages, but is physical maintenance really a "game changer" one of them? The shape of the tiles didn't create all the human-hours for STS maintenance.
Different, yes, completely irrelevant, far from it.
I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Well it's a minor concern right up to entry interface. If they get to that point they have proven a lot of things.
Getting Superheavy successfully off the ground and to MECO makes me anxious every time I think about it.
If they get into orbit then they can worry about the heatshield.
Honestly, even the first reentry doesn't worry me. Humanity has been doing heat shields on spacecraft for a long time, with very few failures. The only one that comes to mind is Columbia, and that wasn't a problem with the heat shield design per se. The Shuttles had a lot of near-disasters due to debris strikes, something that Starship does not really have to deal with. Other than that I'm not sure if a heat shield has ever been the cause of a failure during reentry. More relevantly, SpaceX hasn't had any big heat shield issues during reentry with the Dragons.
As an aside, I have always considered in orbit refueling to be the number one problem they need to solve, and way too many people, both here and elsewhere, consider that practically a fait accompli.
The only one that comes to mind is Columbia, and that wasn't a problem with the heat shield design per se. The Shuttles had a lot of near-disasters due to debris strikes, something that Starship does not really have to deal with.
- The tiles are made of the same material: sintered Silica fibres, coated with borosilicate glass, then impregnated with MTMS (methyltrimethoxysilane) for initial waterproofing. They are nearly identical to the STS tiles in composition, though not in shape.I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Minor? By far the most expensive aspect of the Space Shuttle was TPS maintenance. It consumed ~20,000 man-hours per flight.
John
Which is completely irrelevant to Starship. Their tiles are not made of the same material, are not installed in the same way, and are not 24,500 unique shapes. The game changer is the fact that over 90% of the Starship tiles are the exact same shape. We have seen Starship tile replacement done by people just going up in a scissor lift.
The tiles were initially impregnated with methyltrimethoxysilane (MTMS) during manufacture, and this provided waterproofing through to the first flight and entry, and which point the MTMS burnt off during entry. Subsequent to this, a rewaterproofing agent needed to be applied after every flight.The big timesinks of TPS refurb were waiting for the tiles to dry out if they had been exposed to moisture between landing and being rolled back to a controlled environment, and the actual process of injecting every tile individually with DMES. Whilst replacement of individual tiles meant installing a cut-to-size replacement, tile replacement was not what the majority of time was spent on, particularly by the end of the programme when the switch had been made to r-ewaterproofing agents that did not degrade the adhesives.
Initially, rewaterproofing was performed by spray-on fluoropolymer (Scotchguard), with the idea that it could be sprayed on rapidly after landing to minimise the chance of water ingress. This proved inadequate, as too much Scotchguard would interact with and degrade the Silicone used to adhere the gap-fillers between the tiles, and too little provided inadequate protection and led to water ingress into the tiles.
As a replacement for the Scotchguard, hexamethyldisilazane (HDMS) was applied through vapour diffusion, to provide good penetration into the tile. As a rewaterproofing agent it worked well, but it was found the catalyst used in the HDMS degraded the silicone under the base of the tile (that attached it to the Orbiter), meaning all treated tiles needed to be replaced and a new rewaterproofing agent found.
That new agent was dimethylethoxysilane (DMES), which needed to be injected rather than diffused into the tiles. This was laborious (poking a needle into each tile and injecting sly enough to not fracture the tile) but it worked and did not degrade the silicone, so was the re-waterproofing agent for the rest of the life of STS.
My impression was, that the Shuttle had flight cost of around 1 Billion per start. But 20,000 man hours, paying them 100$ per hour does only bring me to 2.000.000$. There must be some other expensive items on the way.I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Minor? By far the most expensive aspect of the Space Shuttle was TPS maintenance. It consumed ~20,000 man-hours per flight.
John
My impression was, that the Shuttle had flight cost of around 1 Billion per start. But 20,000 man hours, paying them 100$ per hour does only bring me to 2.000.000$. There must be some other expensive items on the way.I just think there's way too much "OMG a couple tiles fell off, time to scrap everything and redesign the entire heat shield" going on here, and not enough, "Hey, only a couple tiles fell off, looks like SpaceX has nearly got the heat shield system down pat."
Frankly of all the issues that SpaceX has to deal with, I have always considered the heat shield to be a very minor concern.
Minor? By far the most expensive aspect of the Space Shuttle was TPS maintenance. It consumed ~20,000 man-hours per flight.
John
The big challenge with STS was not the unique tiles or their bonding, but because of re-waterproofing. After every entry, the waterproofing burnt off and the tiles went from hydrophobic to extremely hydrophilic (to the extend they would 'suck up' ambient humidity, not just rainwater). Wet tiles are bad not because of mass, but because the process of sublimation, freezing, and re-sublimation during ascent, coast, and entry results in internal tile fracturing. That is a known and recorded phenomena, and is independent of tile attachment method. Thus, re-waterproofing is mandatory.
Originally it was intended that the re-waterproofing needed to
be completed quickly for turnaround activities so spray on type materials were investigated as the factory
waterproofing burns out at temperatures above 1050 F. The first spray that was used was a fluro-polymer or
Scotchgard, which provided a thin film of low surface energy on the exterior surface of the tile glass coating. It was
recognized that this treatment would not provide an impervious barrier to water and that its effects would be highly
dependent on the surface tension of the water and resultant contact angle.
After the 2nd flight of Columbia inspection of the Orbiter indicated that in-plane failures of six HRSI tiles had
occurred on the right wing glove area. The depth of the missing material corresponded to the burnout zone of the
factory waterproofing or the 1050 F line. In addition, the surface coating of 12 tiles on the body flap showed
evidence of bubbling.
Starship doesn't have a single point of failure problem on its heat shield, The time to replace 18 tiles is far smaller than the time to wield a syringe on 20,000 tiles. So they will just live with the slight amount of damage potential from water in the tiles.
18 damaged tiles when you have a single point of failure design like Orbiter is catastrophic, and leads to all sorts of paranoid time consuming design choices (that failed anyways).The '18 tiles' is merely how many tiles they found fractured and identified the problem from, not how many tiles will fail from an inadequate waterproofing job. Concluding "if you spray Starship with Scotchguard only 18 tiles will fail" from that is false logic.
Starship doesn't have a single point of failure problem on its heat shieldOften asserted, yet to be proven. SpaceX cover large acreages of the ship with continuous tiles even when leaving a small hole would make things a lot easier (e.g. covering the lift points, covering downward-facing sensors and antennae, etc), so they clearly think that the tiles are all needed. SpaceX are not in the habit of installing a part if they could instead eliminate that part.
The time to replace 18 tiles is far smaller than the time to wield a syringe on 20,000 tiles.Again, that false '18 tiles' figure. And we do not yet know if DMES re-waterproofing is the solution chosen by SpaceX, only that it is one option that has been proven to work successfully.
Thermal protection system anomalies due to moisture absorption that have occurred during flight test led to
many changes to the way tiles were rewaterproofed. Originally it was intended that the re-waterproofing needed to
be completed quickly for turnaround activities so spray on type materials were investigated as the factory
waterproofing burns out at temperatures above 1050 F. The first spray that was used was a fluro-polymer or
Scotchgard, which provided a thin film of low surface energy on the exterior surface of the tile glass coating. It was
recognized that this treatment would not provide an impervious barrier to water and that its effects would be highly
dependent on the surface tension of the water and resultant contact angle.
After the 2nd flight of Columbia inspection of the Orbiter indicated that in-plane failures of six HRSI tiles had
occurred on the right wing glove area. The depth of the missing material corresponded to the burnout zone of the
factory waterproofing or the 1050 F line. In addition, the surface coating of 12 tiles on the body flap showed
evidence of bubbling. Based on these observations and previous results from the ground test program, it was
concluded that water penetration had occurred on the tiles before the flight and the rewaterproofing application
technique required improvement. The mechanism involved in this failure is postulated as follows. Water from
rainstorms entered an area of the tiles before lift-off. During ascent, a small amount of water in the tile was
vaporized, and the remainder cooled rapidly because of the rapid decrease in pressure. When the vehicle went to
orbital conditions, the water changed to ice, which contracted and fractured the tile. The steam generated in the tile
during entry then completed the fracture of the tile.
Prior to the 3rd flight of Columbia an auxiliary pressurization and nozzle system was developed for application of
the Scotchgard. This technique improved the penetration effectiveness of the material into the tile. In addition the
amount of Scotchgard that was applied was increased by a factor of four in an attempt to prevent water absorption.
The post flight inspection after the 3rd flight of Columbia found that several non-densified LRSI and HRSI tile
were missing in the forward fuselage area and body flap areas. In contrast to the STS-2 flight anomaly, complete
loss of the tiles occurred during the mission. After extensive testing the failure was attributed to excessive quantities
of Scotchgard carrier agent that caused swelling of the RTV bond between the tile and the SIP, failing the tile-to-SIP
bondline. The rewaterproofing procedures for STS-4 were modified to reduce the amount of Scotchgard application.
[...]
The flight test program revealed that the film type rewaterproofing was inadequate so activities were undertaken
to develop an internal rewaterproofing system that could return the tile to a factory waterproof state. A commercial
disilazane material was selected as the most promising. This material has a vapor pressure at room temperature that
allows the vapors to penetrate the interior of the tile by means of vapor diffusion. Although ammonia is formed by
the reaction of this product, the amount produced is minimal and the vapors could be handled by adequate
ventilation. This method worked fine until it was discovered that reversion or softening of the RTV-577 screed,
which is used to fair out the underlying structure, could occur. During the STS-41G mission the V070-394504-372
tile was lost, Figure 8, at some point during the reentry phase. The loss occurred at the RTV bondline of the tile to
the underlying RTV-577 screed. The catalyst that was used in the silane tile waterproofing solution was found
through test to be the culprit. Over 4000 tiles were removed and replaced over areas of RTV-577 to preclude further
issues from this chemical reaction. In addition a new waterproofing agent, DimethylEthoxySilane (DMES), was
developed for use during rewaterproofing. Over the remainder of the Space Shuttle program, DMES was proven to
be a very successful waterproofing agent although it was expensive, labor intensive, and generated toxic vapors that
required bay closure to perform the task.
Maybe they have a design of the tile that allows the tile to get wet and allows the resulting steam to escape without damage?The damage is not just from steam, but from internal ice formation. The tiles are already porous to water vapour: that's the problem, not the solution.
18 damaged tiles when you have a single point of failure design like Orbiter is catastrophic, and leads to all sorts of paranoid time consuming design choices (that failed anyways).
The '18 tiles' is merely how many tiles they found fractured and identified the problem from, not how many tiles will fail from an inadequate waterproofing job. Concluding "if you spray Starship with Scotchguard only 18 tiles will fail" from that is false logic.
Starship doesn't have a single point of failure problem on its heat shield
Often asserted, yet to be proven. SpaceX cover large acreages of the ship with continuous tiles even when leaving a small hole would make things a lot easier (e.g. covering the lift points, covering downward-facing sensors and antennae, etc), so they clearly think that the tiles are all needed. SpaceX are not in the habit of installing a part if they could instead eliminate that part.
First one flight after rewaterproofing: you don't rewaterproof for the first every launch because the factory waterproofing has not burnt off yet. The first ever flight was protected by the factory MTMS waterproofing treatment. The NASA document even states outright that the failure on the second flight was at the burnout line of the factory waterproofing (said burnout occurring on the first flight).18 damaged tiles when you have a single point of failure design like Orbiter is catastrophic, and leads to all sorts of paranoid time consuming design choices (that failed anyways).
The '18 tiles' is merely how many tiles they found fractured and identified the problem from, not how many tiles will fail from an inadequate waterproofing job. Concluding "if you spray Starship with Scotchguard only 18 tiles will fail" from that is false logic.
Spray on Scotchgard is literally what they did for the first two shuttle flights. It's not false logic to conclude that the damage yield is 18/20,000 tiles. It's just observation/estimation of a minor (in percentage terms) problem.
They cover those because (a) there's no mat backing those areas, (b) lift points are one critical piece that shouldn't go above 870degC as they are high stress, and (c) sensors and antennae aren't stainless steel and can't handle 870degC.The mat is not the primary TPS. It's a good insualtor agaisnt conductive heat transfer, but that's not the sort of heat transfer you experience during EDL. That's instead radiative (first portion of EDL with highest energy and greatest velocity lost) and later convective (later portion where velocity has slowed). The mats lack the borosilicate glass coating that rejects the majority of radiative heat transfer, and lack the gas impermeability of the borosilicate glass coating that prevents hot gas infiltration (convective heat transfer).
There *are* a few single remaining points of failure on Starship, the lift points being one of them (you wouldn't want them breaking when being caught by chopsticks).The lift points are used for the sling eyes, not by the chopsticks.
They may even re-inject those few tiles or apply special waterproof treatments at those few single points after every flight. Just not 20,000 tiles.The water infiltration failure mode has nothing to do with how much heating they receive during entry, the majority of the failure occurs during ascent. Any tile heated above the waterproofing burnout temperature will need rewaterproofing.
Meanwhile we have design analysis, cryotests being done on tiles soaked in rainUnless SpaceX went and secretly took a blowtorch to the side of the vehicle prior to cryoproofing, those tiles would still have had their factory MTMS waterproofing in place. This is why we do not know what rewaterproofing method SpaceX are using yet: they have yet to have had any times that need rewaterproofing outside of their labs.
First one flight after rewaterproofing: you don't rewaterproof for the first every launch because the factory waterproofing has not burnt off yet. The first ever flight was protected by the factory MTMS waterproofing treatment. The NASA document even states outright that the failure on the second flight was at the burnout line of the factory waterproofing (said burnout occurring on the first flight).18 damaged tiles when you have a single point of failure design like Orbiter is catastrophic, and leads to all sorts of paranoid time consuming design choices (that failed anyways).
The '18 tiles' is merely how many tiles they found fractured and identified the problem from, not how many tiles will fail from an inadequate waterproofing job. Concluding "if you spray Starship with Scotchguard only 18 tiles will fail" from that is false logic.
Spray on Scotchgard is literally what they did for the first two shuttle flights. It's not false logic to conclude that the damage yield is 18/20,000 tiles. It's just observation/estimation of a minor (in percentage terms) problem.QuoteThey cover those because (a) there's no mat backing those areas, (b) lift points are one critical piece that shouldn't go above 870degC as they are high stress, and (c) sensors and antennae aren't stainless steel and can't handle 870degC.The mat is not the primary TPS. It's a good insualtor agaisnt conductive heat transfer, but that's not the sort of heat transfer you experience during EDL. That's instead radiative (first portion of EDL with highest energy and greatest velocity lost) and later convective (later portion where velocity has slowed). The mats lack the borosilicate glass coating that rejects the majority of radiative heat transfer, and lack the gas impermeability of the borosilicate glass coating that prevents hot gas infiltration (convective heat transfer).
The mats alone are not sufficient protection, which is why the entire vehicle TPS is covered in tiles and bare mats are used nowhere.QuoteThere *are* a few single remaining points of failure on Starship, the lift points being one of them (you wouldn't want them breaking when being caught by chopsticks).The lift points are used for the sling eyes, not by the chopsticks.QuoteThey may even re-inject those few tiles or apply special waterproof treatments at those few single points after every flight. Just not 20,000 tiles.The water infiltration failure mode has nothing to do with how much heating they receive during entry, the majority of the failure occurs during ascent. Any tile heated above the waterproofing burnout temperature will need rewaterproofing.QuoteMeanwhile we have design analysis, cryotests being done on tiles soaked in rainUnless SpaceX went and secretly took a blowtorch to the side of the vehicle prior to cryoproofing, those tiles would still have had their factory MTMS waterproofing in place. This is why we do not know what rewaterproofing method SpaceX are using yet: they have yet to have had any times that need rewaterproofing outside of their labs.
The mat is not the primary TPS. It's a good insualtor agaisnt conductive heat transfer, but that's not the sort of heat transfer you experience during EDL. That's instead radiative (first portion of EDL with highest energy and greatest velocity lost) and later convective (later portion where velocity has slowed). The mats lack the borosilicate glass coating that rejects the majority of radiative heat transfer, and lack the gas impermeability of the borosilicate glass coating that prevents hot gas infiltration (convective heat transfer).
Very well, some napkin math to see if we're even vaguely in the correct ballpark:
The mat is not the primary TPS. It's a good insualtor agaisnt conductive heat transfer, but that's not the sort of heat transfer you experience during EDL. That's instead radiative (first portion of EDL with highest energy and greatest velocity lost) and later convective (later portion where velocity has slowed). The mats lack the borosilicate glass coating that rejects the majority of radiative heat transfer, and lack the gas impermeability of the borosilicate glass coating that prevents hot gas infiltration (convective heat transfer).
Correct(1), so the danger of heating a spot of stainless steel past 870degC is in the radiative dominated portion of reentry, where there is the highest energy conditions for heating. The convective heating is done at much lower energies and thus doesn't involve danger of heating to 870degC. I suspect the bare stainless can handle the convective heating all by itself.
Now, go look up the emissivity of the borosilicate glass coating vs. the Saffil. They are only different by about 20% (as opposed to stainless steel which is 2.5x). This is what is involved in the "rejection" of radiative heat.
The glass will be radiating about as efficient as humans can make material, and the Saffil about 20% less so. Since there's a factor of 34 in the small-spot safety of stainless steel over aluminum, that is quite sufficient for small-number-of-tiles loss.
I did the math above, If you think the math is wrong do some math to show why it is wrong, don't just use words. Back them up. Math his how engineering disputes are supposed to done.
(1) see https://en.wikipedia.org/wiki/Atmospheric_entry#Reentry_heating
Very well, some napkin math to see if we're even vaguely in the correct ballpark:
Confining to the convective regime and imagining that somehow the TPS disappears after the radiative regime with no heat transfer to the steel:
Stainless steel heat capacity: ~500J/kg.K
Heat flux as re-entry heating becomes dominated by convective rather than radiative heating (https://www.researchgate.net/figure/Typical-convective-and-radiative-fluxes-encountered-during-Earth-reentry-and-their_fig95_338868244): ~3MW/m2
Mass of 1 square metre of Stainless Steel of thickness 3mm: ~23.6kg
Temperature rise per second per square metre of exposed Stainless Steel in convective heating regime: ~250K
Therefore, exposed Stainless will exceed 870°C (assuming starting from ~-300°C for the LOX tank wall) in ~5 seconds of exposure in the convective heating regime. This ignores that it also needs to survive the radiative regime, and chemical attack (and additional heating) from the surrounding plasma.
So no, your "suspicion" that "bare stainless can handle the convective heating all by itself" is not correct, by a rather large margin. Extended over the entire entry regime, we can make that a pretty definite conclusion. We can also conclude the same from SpaceX application of TPS, which does not leave any Stainless steel exposed to the forward direction. Nor do they leave any of the mats exposed.
the heat flux on the afterbody was about 5 times lower than on the forebody (about 20 W/cm2 as compared to 100 W/cm2
Very well, some napkin math to see if we're even vaguely in the correct ballpark:I suspect the 3MW/m^2 reflects a very steep entry angle common for ablative reentries. In the paper you cite, see figure 5 that shows the different trajectories. I suspect Figure 3, where one might get a 3MW figure at 11km/sec, is for steep rentry angle, not shallow reentry angle. The figure is from 1969, and since all missions at that time were ablative/steep entries, that is the most likely explanation,
Confining to the convective regime and imagining that somehow the TPS disappears after the radiative regime with no heat transfer to the steel:
Stainless steel heat capacity: ~500J/kg.K
Heat flux as re-entry heating becomes dominated by convective rather than radiative heating (https://www.researchgate.net/figure/Typical-convective-and-radiative-fluxes-encountered-during-Earth-reentry-and-their_fig95_338868244): ~3MW/m2
Mass of 1 square metre of Stainless Steel of thickness 3mm: ~23.6kg
Temperature rise per second per square metre of exposed Stainless Steel in convective heating regime: ~250K
Therefore, exposed Stainless will exceed 870°C (assuming starting from ~-300°C for the LOX tank wall) in ~5 seconds of exposure in the convective heating regime. This ignores that it also needs to survive the radiative regime, and chemical attack (and additional heating) from the surrounding plasma.
So no, your "suspicion" that "bare stainless can handle the convective heating all by itself" is not correct, by a rather large margin. Extended over the entire entry regime, we can make that a pretty definite conclusion. We can also conclude the same from SpaceX application of TPS, which does not leave any Stainless steel exposed to the forward direction. Nor do they leave any of the mats exposed.
That seems quite low heating - is it because Starship is fluffy compared to the Shuttle?
How do these hotspots, coefficients and all change if starship comes in with the flaps all the way back? Would they do that? Or will they always come in "arms and legs fully spread"? I would think that offering less head-on surface reduces the heating, at the expense of not decelerating as fast, which might be desired?nah, it makes heat worse if you come in without flaps extended.
Maybe they come in with the flaps half way actuated, so they have some stability control in all directions?
The payload mass is going to be the biggest factor for flap position (in order to trim center of drag to match center of mass). Apart from that you want maximum extension for maximum drag and lift (with some reserve for control).
There might be a double whammy for re-entry heating with heavier payloads as it means both higher mass and smaller area with less extension of the aft flaps.
What paint could they be using between the edge tiles on S24? They presumably don't want it cooking off during re-entry.Could be:
What paint could they be using between the edge tiles on S24? They presumably don't want it cooking off during re-entry.Could be:
Ablative: cooking off during re-entry is the design goal
Cosmetic: cooking off during re-entry is mere visual inconvenience (see: paint damage during F9 re-entry)
Radiative (temperature control in orbit): also does not need to survive re-entry
Radiative (during re-entry): here's the only case where the coating needs to survive (enough of) re-entry to do its job
While there may be some performance improvements by painting some areas, it's clear from looking at how and where they painted that most of the paint is for aesthetic reasons.I don't agree (in part because it doesn't seem that aesthetic of a paint pattern). It seems quite likely that analysis showed they might need more thermal protection, so they added some to maximize the chance it survives reentry.
While there may be some performance improvements by painting some areas, it's clear from looking at how and where they painted that most of the paint is for aesthetic reasons.I don't agree (in part because it doesn't seem that aesthetic of a paint pattern). It seems quite likely that analysis showed they might need more thermal protection, so they added some to maximize the chance it survives reentry.
It could also be for analysis purposes. If they have high resolution tracking cameras following the vehicle's reentry from a chase plane (like was sometimes done with Shuttle or Falcon 9), having black, high-emissivity paint anywhere it might get hot and surrounding, that allows them to map the temperature distribution accurately with infrared (etc) cameras. Shiny stainless steel does not allow that.
The slide deck (https://ntrs.nasa.gov/api/citations/20210020835/downloads/GCD_2021%20APR_SCIFLI_SpaceX%20ACO%20poster.pptx.pdf) literally has 'Starship' in the title, the body, and is plastered with pictures of it. No speculation required.While there may be some performance improvements by painting some areas, it's clear from looking at how and where they painted that most of the paint is for aesthetic reasons.I don't agree (in part because it doesn't seem that aesthetic of a paint pattern). It seems quite likely that analysis showed they might need more thermal protection, so they added some to maximize the chance it survives reentry.
It could also be for analysis purposes. If they have high resolution tracking cameras following the vehicle's reentry from a chase plane (like was sometimes done with Shuttle or Falcon 9), having black, high-emissivity paint anywhere it might get hot and surrounding, that allows them to map the temperature distribution accurately with infrared (etc) cameras. Shiny stainless steel does not allow that.
I think I recall that there was a NASA project funding item someone noticed many months ago for what looked like thermal reentry analysis for an undescribed object doing reentry near Hawaii, and it was speculated that this was for NASA looking at the Starship reentry. This would make sense both for SpaceX, so they don't have to build a dedicated system to watch this, and NASA, to help refine their models of different aerodynamic shapes doing reentry. All of NASA's existing data is probably either on capsules, or the Space Shuttle.
Starship's ventral-forward attitude means that the dorsal surface is fairly visible after Starship passes the observer, I think. do we know where the WB-57 will be located?The slide deck (https://ntrs.nasa.gov/api/citations/20210020835/downloads/GCD_2021%20APR_SCIFLI_SpaceX%20ACO%20poster.pptx.pdf) literally has 'Starship' in the title, the body, and is plastered with pictures of it. No speculation required.While there may be some performance improvements by painting some areas, it's clear from looking at how and where they painted that most of the paint is for aesthetic reasons.I don't agree (in part because it doesn't seem that aesthetic of a paint pattern). It seems quite likely that analysis showed they might need more thermal protection, so they added some to maximize the chance it survives reentry.
It could also be for analysis purposes. If they have high resolution tracking cameras following the vehicle's reentry from a chase plane (like was sometimes done with Shuttle or Falcon 9), having black, high-emissivity paint anywhere it might get hot and surrounding, that allows them to map the temperature distribution accurately with infrared (etc) cameras. Shiny stainless steel does not allow that.
I think I recall that there was a NASA project funding item someone noticed many months ago for what looked like thermal reentry analysis for an undescribed object doing reentry near Hawaii, and it was speculated that this was for NASA looking at the Starship reentry. This would make sense both for SpaceX, so they don't have to build a dedicated system to watch this, and NASA, to help refine their models of different aerodynamic shapes doing reentry. All of NASA's existing data is probably either on capsules, or the Space Shuttle.
Starship is projected to enter over the Pacific Missile Range due to the existing extensive tracking and measurement capabilities of that range. WB-57 observations would be nice, but still mainly viewing from 'below' during most of EDL - by the time Starship has descended below the WB-57's maximum altitude it will be almost if not already (for the first test with limited downmass) subsonic.
There will be many military satellites focused on that Starship flight. Nobody has more to gain from Starship than the US military.Starship's ventral-forward attitude means that the dorsal surface is fairly visible after Starship passes the observer, I think. do we know where the WB-57 will be located?The slide deck (https://ntrs.nasa.gov/api/citations/20210020835/downloads/GCD_2021%20APR_SCIFLI_SpaceX%20ACO%20poster.pptx.pdf) literally has 'Starship' in the title, the body, and is plastered with pictures of it. No speculation required.While there may be some performance improvements by painting some areas, it's clear from looking at how and where they painted that most of the paint is for aesthetic reasons.I don't agree (in part because it doesn't seem that aesthetic of a paint pattern). It seems quite likely that analysis showed they might need more thermal protection, so they added some to maximize the chance it survives reentry.
It could also be for analysis purposes. If they have high resolution tracking cameras following the vehicle's reentry from a chase plane (like was sometimes done with Shuttle or Falcon 9), having black, high-emissivity paint anywhere it might get hot and surrounding, that allows them to map the temperature distribution accurately with infrared (etc) cameras. Shiny stainless steel does not allow that.
I think I recall that there was a NASA project funding item someone noticed many months ago for what looked like thermal reentry analysis for an undescribed object doing reentry near Hawaii, and it was speculated that this was for NASA looking at the Starship reentry. This would make sense both for SpaceX, so they don't have to build a dedicated system to watch this, and NASA, to help refine their models of different aerodynamic shapes doing reentry. All of NASA's existing data is probably either on capsules, or the Space Shuttle.
Starship is projected to enter over the Pacific Missile Range due to the existing extensive tracking and measurement capabilities of that range. WB-57 observations would be nice, but still mainly viewing from 'below' during most of EDL - by the time Starship has descended below the WB-57's maximum altitude it will be almost if not already (for the first test with limited downmass) subsonic.
There will be many military satellites focused on that Starship flight. Nobody has more to gain from Starship than the US military.Starship's ventral-forward attitude means that the dorsal surface is fairly visible after Starship passes the observer, I think. do we know where the WB-57 will be located?The slide deck (https://ntrs.nasa.gov/api/citations/20210020835/downloads/GCD_2021%20APR_SCIFLI_SpaceX%20ACO%20poster.pptx.pdf) literally has 'Starship' in the title, the body, and is plastered with pictures of it. No speculation required.While there may be some performance improvements by painting some areas, it's clear from looking at how and where they painted that most of the paint is for aesthetic reasons.I don't agree (in part because it doesn't seem that aesthetic of a paint pattern). It seems quite likely that analysis showed they might need more thermal protection, so they added some to maximize the chance it survives reentry.
It could also be for analysis purposes. If they have high resolution tracking cameras following the vehicle's reentry from a chase plane (like was sometimes done with Shuttle or Falcon 9), having black, high-emissivity paint anywhere it might get hot and surrounding, that allows them to map the temperature distribution accurately with infrared (etc) cameras. Shiny stainless steel does not allow that.
I think I recall that there was a NASA project funding item someone noticed many months ago for what looked like thermal reentry analysis for an undescribed object doing reentry near Hawaii, and it was speculated that this was for NASA looking at the Starship reentry. This would make sense both for SpaceX, so they don't have to build a dedicated system to watch this, and NASA, to help refine their models of different aerodynamic shapes doing reentry. All of NASA's existing data is probably either on capsules, or the Space Shuttle.
Starship is projected to enter over the Pacific Missile Range due to the existing extensive tracking and measurement capabilities of that range. WB-57 observations would be nice, but still mainly viewing from 'below' during most of EDL - by the time Starship has descended below the WB-57's maximum altitude it will be almost if not already (for the first test with limited downmass) subsonic.
I agree that the heatshield functioning is the part of Starship I worry about most. And let me re-word my earlier comment"There will be many military satellites focused on that Starship flight. Nobody has more to gain from Starship than the US military.
SpaceX and NASA might disagree. SpaceX has bet nearly everything on Starship being successful.
It will be one of the most monitored launches ever.
I have total faith in Superheavy being able to work and even recovery with the chopsticks.
Starship can get to orbit, I believe that as well. The heatshield on such a large vehicle with control surfaces, that has been the biggest unknown in my mind since the start of this development effort.
Yes in theory it should all work fine. But the trouble is that in theory practice and theory are the same. But in practice they are often different. Lets hope that any problems uncovered can be easily resolved an there aren't any seriously hairy gotyas lurking.I agree that the heatshield functioning is the part of Starship I worry about most. And let me re-word my earlier comment"There will be many military satellites focused on that Starship flight. Nobody has more to gain from Starship than the US military.
SpaceX and NASA might disagree. SpaceX has bet nearly everything on Starship being successful.
It will be one of the most monitored launches ever.
I have total faith in Superheavy being able to work and even recovery with the chopsticks.
Starship can get to orbit, I believe that as well. The heatshield on such a large vehicle with control surfaces, that has been the biggest unknown in my mind since the start of this development effort.
"There will be many military satellites focused on that Starship flight. Not all of them will be American."
...Stamp the stainless steel to form a tile-shaped flat surface for each tile. Probably easier, lighter. and stronger than adding bumps. Do this as a post-processng step when forming the rings. It does make adding stringers more complicated, but not my much.
~~~~~~~~~~~~~~~
An idea comes: a bump or attachment of some sort, UNDER the blanket, attached to the stainless hull itself, that changes the pressure and stress loading of the tri-corner areas.
I take it you've never tried popping a dent out of a car. With material that thin a small amount of internal pressure will pop the skin right back to the shape it started. If there's a tile on top then it would be destroyed....Stamp the stainless steel to form a tile-shaped flat surface for each tile. Probably easier, lighter. and stronger than adding bumps. Do this as a post-processng step when forming the rings. It does make adding stringers more complicated, but not my much.
~~~~~~~~~~~~~~~
An idea comes: a bump or attachment of some sort, UNDER the blanket, attached to the stainless hull itself, that changes the pressure and stress loading of the tri-corner areas.
This is a bit off the wall, but does anybody have a clue about the reflectivity or absorbance of the tiles at various radio frequencies?
This is a bit off the wall, but does anybody have a clue about the reflectivity or absorbance of the tiles at various radio frequencies?I can't find an actual transmissivity spectrum of the STS tiles (which the Starships tiles are near identical to in composition) but there were L-band antennae installed under the tiles, so its reasonable to assume that at least UHF and below are reasonably unimpeded.
I believe there were about 30 tiles lost. On the basis that the rigors of launch and re-entry are on the order of a hundred times that of a static fire, we could expect a loss of 3000 tiles and probable loss of the Starship as well. A more secure method of attaching tiles needs to be developed which, I'm sure Spacex is working on.
I believe there were about 30 tiles lost. On the basis that the rigors of launch and re-entry are on the order of a hundred times that of a static fire, we could expect a loss of 3000 tiles and probable loss of the Starship as well. A more secure method of attaching tiles needs to be developed which, I'm sure Spacex is working on.
I believe there were about 30 tiles lost. On the basis that the rigors of launch and re-entry are on the order of a hundred times that of a static fire, we could expect a loss of 3000 tiles and probable loss of the Starship as well. A more secure method of attaching tiles needs to be developed which, I'm sure Spacex is working on.
Those are likely not tiles at all, but antenna (or other instrumentation) covers for a ship which according to rumors it's not going to have a heatshield at all. Installing such stuff paints the said rumors more likely.
Those are likely not tiles at all, but antenna (or other instrumentation) covers for a ship which according to rumors it's not going to have a heatshield at all. Installing such stuff paints the said rumors more likely.Yeah, rumor of no tiles. Why have mounting pins if tiles aren't planned? Each one of those nubbins will collect heat and melt. The ones on the centerline may even reach through or distort the shock front. It's interesting to speculate the impact all this would have in a sorta academic way but I doubt they're going to actually test it. Whatever it would do, it would not be good. Something else is going on.
Occam's razor: The pins are there because the temporary switch to no tiles hadn't been planned before this nosecone was already made and had the pins welded on. They used the next nosecone in line which was this one.
Occam's razor: The pins are there because the temporary switch to no tiles hadn't been planned before this nosecone was already made and had the pins welded on. They used the next nosecone in line which was this one.Alternative cut of the razor: the pins are installed but tiles aren't because they intend to install the tiles but the tiles are not ready to be installed yet (e.g. major changes to tile manufacture interrupting production, like moving sites, replacing equipment, changing fibre suppliers or bringing fibre manufacture in-house, etc).
Occam's razor: The pins are there because the temporary switch to no tiles hadn't been planned before this nosecone was already made and had the pins welded on. They used the next nosecone in line which was this one.
If they attempt re-entry in this configuration, surely the pins will destroy the smooth plasma flow around the vehicle?
(and don't call me Shirley)
Unless they plan for this to be a destructive re-entry all along...
Alternative cut of the razor: the pins are installed but tiles aren't because they intend to install the tiles but the tiles are not ready to be installed yet (e.g. major changes to tile manufacture interrupting production, like moving sites, replacing equipment, changing fibre suppliers or bringing fibre manufacture in-house, etc).
Occam's razor: The pins are there because the temporary switch to no tiles hadn't been planned before this nosecone was already made and had the pins welded on. They used the next nosecone in line which was this one.
If they attempt re-entry in this configuration, surely the pins will destroy the smooth plasma flow around the vehicle?
(and don't call me Shirley)
Unless they plan for this to be a destructive re-entry all along...
Those are likely not tiles at all, but antenna (or other instrumentation) covers for a ship which according to rumors it's not going to have a heatshield at all. Installing such stuff paints the said rumors more likely.
Recent S25 stacking - The tile gap between sections is a lot wider than we've seen previously. Before, ring segments gaps have omitted one row of complete tiles (but attached via adhesive rather than pins) and one row of half-tiles (attached by adhesive) on either side of the gap, making for a '3 tile wide' gap. Here, that gap looks closer to 5-7 tiles.Another thought. Maybe tile application is planned as an early move to the new building and things are lagging. No idea why this specific operation would be moved early. Just looking at possibilities.Occam's razor: The pins are there because the temporary switch to no tiles hadn't been planned before this nosecone was already made and had the pins welded on. They used the next nosecone in line which was this one.Alternative cut of the razor: the pins are installed but tiles aren't because they intend to install the tiles but the tiles are not ready to be installed yet (e.g. major changes to tile manufacture interrupting production, like moving sites, replacing equipment, changing fibre suppliers or bringing fibre manufacture in-house, etc).
Occam's razor: The pins are there because the temporary switch to no tiles hadn't been planned before this nosecone was already made and had the pins welded on. They used the next nosecone in line which was this one.Naw, doesn't make sense. Besides screwing up reentry, naked pins can't be doing anything good for ascent. Lots of drag and breakup of laminar flow. Judging by past performance, if SX didn't want tiles all of a sudden they would scrap the pinned pieces and move on.
How long exactly would ascent performance be affected to any major degree? Launch, get up and out of most of the atmosphere then begin to lay over and really pour on the acceleration. AIUI the atmospheric portion of ascent is a small portion of the total acceleration plot of an orbital vehicle.Occam's razor: The pins are there because the temporary switch to no tiles hadn't been planned before this nosecone was already made and had the pins welded on. They used the next nosecone in line which was this one.Naw, doesn't make sense. Besides screwing up reentry, naked pins can't be doing anything good for ascent. Lots of drag and breakup of laminar flow. Judging by past performance, if SX didn't want tiles all of a sudden they would scrap the pinned pieces and move on.
Hey, maybe exposed pins can BE the TPS. They are sacrificial matter that slowly evaporates, keeping the plasma from the actual hull. Naturally not reusable, but then again, the first orbital test flight wasn't supposed to be recovered anyways.Nah. They’ll probably actually make the problem worse by creating little hot spots on the flow around them.
If the pins remain as part of the design, we are bound to find out.Hey, maybe exposed pins can BE the TPS. They are sacrificial matter that slowly evaporates, keeping the plasma from the actual hull. Naturally not reusable, but then again, the first orbital test flight wasn't supposed to be recovered anyways.Nah. They’ll probably actually make the problem worse by creating little hot spots on the flow around them.
It seems to me that the most likely explanation for the pins without tiles on ship 26 is simply that they've changed up the assembly order a bit. It's even possible that they've decided that they can't do a static fire from the suborbital pad without damaging tiles due to the acoustics, and so have opted to not install them until after the static fire campaign is complete.I would think that you're likely to risk losing tiles during launch if you can't static fire on the suborbital pad without damaging tiles. Even if the acoustic environment is a bit different for orbital launch, I would hope the tiles aren't so marginal that a stress test like that would cause them to fail.
Remember it's not a case of not installing tiles on the pins on S26, they were installed (on the nose at least) and later removed...Wasted mass if they're not planning on recovering the stage.
The question is why?
Occam's razor: The pins are there because the temporary switch to no tiles hadn't been planned before this nosecone was already made and had the pins welded on. They used the next nosecone in line which was this one.Naw, doesn't make sense. Besides screwing up reentry, naked pins can't be doing anything good for ascent. Lots of drag and breakup of laminar flow. Judging by past performance, if SX didn't want tiles all of a sudden they would scrap the pinned pieces and move on.
Don't know if you know about it but this site has some useful articles ;)Those are likely not tiles at all, but antenna (or other instrumentation) covers for a ship which according to rumors it's not going to have a heatshield at all. Installing such stuff paints the said rumors more likely.
Would someone please provide a summary of the rumours? I looked back a few pages and didn't find anything. Cheers!
As previously reported, Ship 26 and Ship 27 may be undergoing a radical change in plans, omitting thermal protection system (TPS) tiles and not installing aerodynamic flaps. So far, this seems to be holding true with parts of Ship 26 seen now bare of tiles and on stand-by at Starbase’s ring yard for stacking.
Ship 27 parts are also proceeding similarly to Ship 26 parts. In some cases, there seems to be a strange mix-match of parts for these vehicles.
While all of this is happening, workers have been seen doing unusual work on future Starship vehicles and more concretely on Ship 26.
Workers were seen removing Thermal Protection System (TPS) tiles and blankets from Ship 26’s nosecone, while some of its barrel sections, which were supposed to receive the installation pins for the TPS tiles, are already staged outside in the ring yard ready for stacking.
While there has not been any official reason provided, some indications point to SpaceX trying to fast-track Ship 26 and Ship 27 builds by not installing TPS tiles or even flaps in order to quickly deliver Starlink v2 satellites into orbit, which the company may need in order to accelerate deployment once Starship proves itself worthy of going into orbit.
To be straight up, I've got no numbers and no firm answers. Just things to consider. Laying over for a horizontal component is mission dependent. Historically it often starts within 10's of seconds after liftoff. MaxQ changes accordingly. MaxQ is enough of a force to be reconned with that most if not all launches throttle down through it. Atmospheric transit may account for a small portion of the total acceleration but that says nothing about its portion of the total energy expenditure. Unless SX has modeled naked pins during liftoff, they don't have answers either. Like I said, I see nothing good coming from it. And I do see many possible gotcha's.How long exactly would ascent performance be affected to any major degree? Launch, get up and out of most of the atmosphere then begin to lay over and really pour on the acceleration. AIUI the atmospheric portion of ascent is a small portion of the total acceleration plot of an orbital vehicle.Occam's razor: The pins are there because the temporary switch to no tiles hadn't been planned before this nosecone was already made and had the pins welded on. They used the next nosecone in line which was this one.Naw, doesn't make sense. Besides screwing up reentry, naked pins can't be doing anything good for ascent. Lots of drag and breakup of laminar flow. Judging by past performance, if SX didn't want tiles all of a sudden they would scrap the pinned pieces and move on.
Any chance these exposed pins would begin to ablate? It might be nice to know how melting pins material(stainless?) affects "downstream" TPS.
It seems to me that the most likely explanation for the pins without tiles on ship 26 is simply that they've changed up the assembly order a bit. It's even possible that they've decided that they can't do a static fire from the suborbital pad without damaging tiles due to the acoustics, and so have opted to not install them until after the static fire campaign is complete.Now that is good thinking.
Hmmm. Maybe I'll have to eat my words. Low throttle well before MaxQ. Maybe even for a while after MaxQ. No fins. No tiles. Lots of margin. And ammo in their FCC arguments about bandwidth.Don't know if you know about it but this site has some useful articles ;)Those are likely not tiles at all, but antenna (or other instrumentation) covers for a ship which according to rumors it's not going to have a heatshield at all. Installing such stuff paints the said rumors more likely.
Would someone please provide a summary of the rumours? I looked back a few pages and didn't find anything. Cheers!
https://www.nasaspaceflight.com/2022/09/starship-next-phase-of-testing/ (https://www.nasaspaceflight.com/2022/09/starship-next-phase-of-testing/)QuoteAs previously reported, Ship 26 and Ship 27 may be undergoing a radical change in plans, omitting thermal protection system (TPS) tiles and not installing aerodynamic flaps. So far, this seems to be holding true with parts of Ship 26 seen now bare of tiles and on stand-by at Starbase’s ring yard for stacking.
Ship 27 parts are also proceeding similarly to Ship 26 parts. In some cases, there seems to be a strange mix-match of parts for these vehicles.
https://www.nasaspaceflight.com/2022/08/booster-7-additional-tests/ (https://www.nasaspaceflight.com/2022/08/booster-7-additional-tests/)QuoteWhile all of this is happening, workers have been seen doing unusual work on future Starship vehicles and more concretely on Ship 26.
Workers were seen removing Thermal Protection System (TPS) tiles and blankets from Ship 26’s nosecone, while some of its barrel sections, which were supposed to receive the installation pins for the TPS tiles, are already staged outside in the ring yard ready for stacking.
While there has not been any official reason provided, some indications point to SpaceX trying to fast-track Ship 26 and Ship 27 builds by not installing TPS tiles or even flaps in order to quickly deliver Starlink v2 satellites into orbit, which the company may need in order to accelerate deployment once Starship proves itself worthy of going into orbit.
Remember it's not a case of not installing tiles on the pins on S26, they were installed (on the nose at least) and later removed...
The question is why?
In this case, they might just have to strip the TPS for environmental reasons, since we can probably expect it to have a lot of the same potential health issues from exposure as asbestos.
Until they catch a booster, why expend resources on putting tiles on the ships, just expend them and move on. Once they catch a few boosters then concentrate on ship reuse. Classic agile development technique. Only work on what you need today to get the fastest viable product to market. After that refine. The current ships with tiles are just development lead products to see where the team working on that in parallel may need to refine their portion of the product.It's a tradeoff. They have a limited number of approved launches, so they need to test the TPS on every launch. The resources needed to test EDL are different than the resources to test launch, and except for the very first launch the EDL test can be deferred for days or weeks, so there is not even a short-term resource allocation problem.
Until they catch a booster, why expend resources on putting tiles on the ships, just expend them and move on. Once they catch a few boosters then concentrate on ship reuse. Classic agile development technique. Only work on what you need today to get the fastest viable product to market. After that refine. The current ships with tiles are just development lead products to see where the team working on that in parallel may need to refine their portion of the product.They explicitly started with the Starship part of the system because that was going to take the most effort and the whole reusable system was the minimum viable product - they already had unrivaled launch capabilities.
I would have to disagree with the sentiment that it will not speed up the rest of the program. They appear to have paused further development of the heat shield until they get flight data to work off of to continue improving the design. Because of this it appears that their choices are to pause production for months after the first flight while improvements are implemented, or continue production without heat shields and continue developing SH and stage 0. Going to the effort of installing a heat shield on S26 & 27 would only give them redundant data at the cost of pulling resources from other areas and extending the production timeline.Until they catch a booster, why expend resources on putting tiles on the ships, just expend them and move on. Once they catch a few boosters then concentrate on ship reuse. Classic agile development technique. Only work on what you need today to get the fastest viable product to market. After that refine. The current ships with tiles are just development lead products to see where the team working on that in parallel may need to refine their portion of the product.They explicitly started with the Starship part of the system because that was going to take the most effort and the whole reusable system was the minimum viable product - they already had unrivaled launch capabilities.
Now with Starlink V2 needing launches ASAP they might have a reason for a few expendable launches but I highly doubt it would have anything to do with speeding up the rest of the program.
It could be that they can build a Superheavy quicker than they can a fully tiled and finned Starship. So to get up to pace for launching StarLinks they needed to speed up the upper stage production.And they may still get valuable data that anchors their aero heating and structural models for a bare SS on reentry. They may even have enough torque authority from ACS only and no flaps to trim their preferred attitude during the critical phase of reentry.
It could be that they can build a Superheavy quicker than they can a fully tiled and finned Starship. So to get up to pace for launching StarLinks they needed to speed up the upper stage production.As an alternative, put more resources into SS and build fewer boosters. The last Elon mentioned long term SS to booster ratio it was 10:1.
Hmm... Another possibility is that S26 is in the process of being scrapped, similar to what they did with S16 after S15 flew. In this case, they might just have to strip the TPS for environmental reasons, since we can probably expect it to have a lot of the same potential health issues from exposure as asbestos.Highly unlikely.
Zack Golden reasonably arrives at the conclusion that the tile damage from the 6 engine Raptor test was caused by debris from the test stand.Which suggests that there should be action around the base to either strengthen the concrete or overlay it with steel plate preping for the next flight.
Implications for taking off from Mars, but not for taking off from Earth.
"the next flight" will see Starship atop the booster not on the suborbital pad. Static fires of course.....Zack Golden reasonably arrives at the conclusion that the tile damage from the 6 engine Raptor test was caused by debris from the test stand.Which suggests that there should be action around the base to either strengthen the concrete or overlay it with steel plate preping for the next flight.
Implications for taking off from Mars, but not for taking off from Earth.
That should be pretty visible. Has anyone seen this?
"the next flight" will see Starship atop the booster not on the suborbital pad. Static fires of course.....Zack Golden reasonably arrives at the conclusion that the tile damage from the 6 engine Raptor test was caused by debris from the test stand.Which suggests that there should be action around the base to either strengthen the concrete or overlay it with steel plate preping for the next flight.
Implications for taking off from Mars, but not for taking off from Earth.
That should be pretty visible. Has anyone seen this?
"the next flight" will see Starship atop the booster not on the suborbital pad. Static fires of course.....Then I guess the question becomes "Does the launch pad differ from the static fire pad?" IE Heavier concrete layers, steel plates laid down etc.
And if Raptors ongoing development work include upgrading the thrust level without it whatever debris got blown up by them starting up is going to happen worse, without something being done to the pad."the next flight" will see Starship atop the booster not on the suborbital pad. Static fires of course.....Zack Golden reasonably arrives at the conclusion that the tile damage from the 6 engine Raptor test was caused by debris from the test stand.Which suggests that there should be action around the base to either strengthen the concrete or overlay it with steel plate preping for the next flight.
Implications for taking off from Mars, but not for taking off from Earth.
That should be pretty visible. Has anyone seen this?
Don't forget S25. It has to go through ambient, cryo, thrust and static fire tests too. The sub-orbital pads need an upgrade if they want to SF 6 Raptors again.
"the next flight" will see Starship atop the booster not on the suborbital pad. Static fires of course.....Then I guess the question becomes "Does the launch pad differ from the static fire pad?" IE Heavier concrete layers, steel plates laid down etc.
That would suggest that unexpected high levels of pad debris was the issue with the missing tiles.
The risk of debris hitting tiles when the ship is stacked on the booster is near zero."the next flight" will see Starship atop the booster not on the suborbital pad. Static fires of course.....Then I guess the question becomes "Does the launch pad differ from the static fire pad?" IE Heavier concrete layers, steel plates laid down etc.
That would suggest that unexpected high levels of pad debris was the issue with the missing tiles.
IIUC It looks to me that the super-heavy pad has a much taller "milk stool", eyeballing it 6m to 30m, at least for some of the mockups. So perhaps they've already learned the lessons and made the changes.
OTOH they will need somewhere to static fire SS (Static firing Starship atop the booster is not a good idea) so some changes may be needed to the static fire pad.
So, we're seeing static fire tile damage that looks to be unavoidable without heroic efforts. An alternative reason for tile challenged builds? Do all the ground testing without tiles then install tiles before mounting SS on SH?
It looks like they are planning on some throwaways to get StarLink v2 going but maybe this makes makes long term sense.
I remember seeing images of this and have always wondered why they were'nt more use than huge, heavy flame trenches.
I find it fascinating we've not seen any evidence of flame diverters (which they use at MacGregor) for the test mount or main launch table. Even rolling in a small one like used for the V2 would presumably help?
Either way the key challenge for the heat shield is not static fire debris but launch vibration. (Mars landings are of course another matter entirely.)
I remember seeing images of this and have always wondered why they were'nt more use than huge, heavy flame trenches.
I find it fascinating we've not seen any evidence of flame diverters (which they use at MacGregor) for the test mount or main launch table. Even rolling in a small one like used for the V2 would presumably help?
Either way the key challenge for the heat shield is not static fire debris but launch vibration. (Mars landings are of course another matter entirely.)
Thanks for providing the image.
OK. But that has absolutely nothing to do with what OTV said.So, we're seeing static fire tile damage that looks to be unavoidable without heroic efforts. An alternative reason for tile challenged builds? Do all the ground testing without tiles then install tiles before mounting SS on SH?I would not call some upgrade of a stand a "heroic effort" by any means.
It looks like they are planning on some throwaways to get StarLink v2 going but maybe this makes makes long term sense.
Adding bespoke debris/blast shields to the test mount to protect the flaps and lower edge of the starship doesn't sound that difficult in the scheme of things. Then any resulting tile loss would be due to startup vibrations, so somewhat indicative of what will happen on an actual flight.How indicative is an open question. Being close to the ground is acoustically different than being on top of SH. There's a lot of acoustic energy being reflected back up. It's conceivable that when stacked during an SH live fire a whole new set of problems will show up. I hope not but that's why the test.
I believe this argument has been made several times before on this thread, but in the light of all the talk about focussing on optimizing the test stand to avoid damages:That is a very interesting trade.
The ground tests on sub-par stands also serve as good testing grounds for landing/starting on unprepared terrain. Certainly, SS is a long way away from regularly landing in such environments (maybe moon being an exception). But think about what you can learn early on about making your engines/vehicle more robust. You might even pick up some easy fixes that substantially reduce the damages in these kind of environments, when you have experience (=data). And how to collect better data on this than on a ship that might not even fly, sits on the ground and can be easily inspected..
So the process of finding a good enough (sub-)orbital test stand and launch pad has synergies with arriving at a more robust system.
I believe this argument has been made several times before on this thread, but in the light of all the talk about focussing on optimizing the test stand to avoid damages:That is a very interesting trade.
The ground tests on sub-par stands also serve as good testing grounds for landing/starting on unprepared terrain. Certainly, SS is a long way away from regularly landing in such environments (maybe moon being an exception). But think about what you can learn early on about making your engines/vehicle more robust. You might even pick up some easy fixes that substantially reduce the damages in these kind of environments, when you have experience (=data). And how to collect better data on this than on a ship that might not even fly, sits on the ground and can be easily inspected..
So the process of finding a good enough (sub-)orbital test stand and launch pad has synergies with arriving at a more robust system.
On the one hand it improves your chance of a rugged TPS for the Mars landing, but on the other it could seriously damage an otherwise perfectly good SS that could make orbit and land safetly on a concrete pad, but now won't :(
Also you get that TPS testing for free (apart from the pad repairs).
OTOH the key goal right now is simply to get to (and back from) orbit in the first place.
That has to be the enabling step to get every SS programme moving.
Hasn't she already done so?
Starting to get OT here, but at what point in this hypothesis does Gwynn Shotwell call up Musk as ask "hey about those Starlink v2 satellites we need to make revenue next year", they build a more robust test stand so they can test actual orbital launches
Uh, I thought that was five launches per year. Does anybody have that at their fingertips?Hasn't she already done so?
Starting to get OT here, but at what point in this hypothesis does Gwynn Shotwell call up Musk as ask "hey about those Starlink v2 satellites we need to make revenue next year", they build a more robust test stand so they can test actual orbital launches
That was my point. Leave the sub orbital stand alone and if damages a SS that's a learning experience, or upgrade and push harder to get to orbit to begin with.
My instinct is that the importance of TPS exceeds engines. There's a Raptor (or should we call it Raptor II?) thrust level that will get SS to orbit. Anything above that --> more payload. A design that's not hitting 100% of theoretical performance is not a show stopper.
But underperfoming TPS --> Vehicle will (or probably will) fail to survive re-entry. And that stops everything, unless you want to sacrifice every SS.
BTW I just remembered that someone can only have 5 launches from this site. Has anyone tracke how many they have left? I would have guessed they would have pushed for at least 12 to allow (potentially) 1 a month to iterate the design.
Sorry, that indeed should have been 5/year. That could seem generous in early development, but now with whole stage 1s and 2s built it would seem quite restrictive.
Uh, I thought that was five launches per year. Does anybody have that at their fingertips?
Sorry, that indeed should have been 5/year. That could seem generous in early development, but now with whole stage 1s and 2s built it would seem quite restrictive.
Could they have just one left that they are holding in reserve to try and make orbit before the year ends? Not quite a SS to Mars, but a good way to close out 2022. In which case they'd want every possible failure mode closed off (AFAP) before using it.
The 5/yr is a count of SH launches, not orbital launches. If they launched an SH 100 meters in the air with no SS on top to test a chopstick catch, it would still count as an SH launch. I suspect this is the reason they will only do full-up orbital launches of SH. The distinction is academic unless they want to start hopping SH out to a floating platform, in which case they will probably try for a change to the rule.Sorry, that indeed should have been 5/year. That could seem generous in early development, but now with whole stage 1s and 2s built it would seem quite restrictive.
Could they have just one left that they are holding in reserve to try and make orbit before the year ends? Not quite a SS to Mars, but a good way to close out 2022. In which case they'd want every possible failure mode closed off (AFAP) before using it.
Which universe are you from where 5 - 0 = 1? There hasn't been a single orbital launch of Starship, or even attempt at orbital launch, so how could there be only one left out of five?
The 5/yr is a count of SH launches, not orbital launches. If they launched an SH 100 meters in the air with no SS on top to test a chopstick catch, it would still count as an SH launch. I suspect this is the reason they will only do full-up orbital launches of SH. The distinction is academic unless they want to start hopping SH out to a floating platform, in which case they will probably try for a change to the rule.That is what I thought.
There have been no SH launches, so the count is zero. It's not a launch unless it leaves the pad.The 5/yr is a count of SH launches, not orbital launches. If they launched an SH 100 meters in the air with no SS on top to test a chopstick catch, it would still count as an SH launch. I suspect this is the reason they will only do full-up orbital launches of SH. The distinction is academic unless they want to start hopping SH out to a floating platform, in which case they will probably try for a change to the rule.That is what I thought.
So has anyone been keeping count which ones would could toward the limit?
There have been no SH launches, so the count is zero. It's not a launch unless it leaves the pad.Thanks for that.
In addition to 5/yr SH, They are also allowed to do 12/yr SS launches that do no include an SH. There has not been an SS launch this year. A full stack launch is an SH launch, not an SS launch.
Sorry, not tomorrow. They need both the FCC temporary frequency licenses and the actual FAA launch license. Both of these are routine and they don't take long, but they do result in public notices that we all get to see, just like at KSC. More than a day but less than a week(?)There have been no SH launches, so the count is zero. It's not a launch unless it leaves the pad.Thanks for that.
In addition to 5/yr SH, They are also allowed to do 12/yr SS launches that do no include an SH. There has not been an SS launch this year. A full stack launch is an SH launch, not an SS launch.
It clearly means that SX is not limited by having run out of takeoff opportunities at the site. They could (in principle) stack an SS and SH tomorrow and take a shot at orbit.
It looks as if the TPS is proving more difficult to perfect than expected.
Sorry, not tomorrow. They need both the FCC temporary frequency licenses and the actual FAA launch license. Both of these are routine and they don't take long, but they do result in public notices that we all get to see, just like at KSC. More than a day but less than a week(?)And thanks for this as well. That gives a future timeline. I'm guessing those timescales would lengthen once we start getting closer to the Christmas period.
The TPS isn’t stopping them from doing an orbital attempt. They don’t need to recover Starship intact for the first several dozen launches.Stage 2 reusability is the key distinguising feature of SS over F9. Without it you just have a very much larger, very much more complicated F9 architecture.
I think the actual pacing item is prep of the booster itself ("robustness upgrades" for B7) + static fires, nothing to do with heat shield.This seems doubtful. :(
If you can't survive re-entry then SpaceX "merely" have a F9-style partially reusable vehicle capable of super-heavy-lift at a lower cost/kg than F9. Starship recovery and re-use are desirable in the long term for further cost reduction and for improved schedule (not needing to build an additional 6 engines between launches), but a partially reusable Starship + Super Heavy stack is still a viable system for payloads of sufficient mass and value.I think the actual pacing item is prep of the booster itself ("robustness upgrades" for B7) + static fires, nothing to do with heat shield.This seems doubtful. :(
Having gone through so many iterations of Raptor it should be possible to deliver enough of a standard version that can run for what, about 10 mins total? That would get them early data on TPS under actual operating conditions.
It's a cliche but once you get to LEO you are "Halfway to anywhere." Payload can always be increased but if you can't survive reentry
TPS is looking like the long pole in the tent.
If you can't survive re-entry then SpaceX "merely" have a F9-style partially reusable vehicle capable of super-heavy-lift at a lower cost/kg than F9. Starship recovery and re-use are desirable in the long term for further cost reduction and for improved schedule (not needing to build an additional 6 engines between launches), but a partially reusable Starship + Super Heavy stack is still a viable system for payloads of sufficient mass and value.I think the actual pacing item is prep of the booster itself ("robustness upgrades" for B7) + static fires, nothing to do with heat shield.This seems doubtful. :(
Having gone through so many iterations of Raptor it should be possible to deliver enough of a standard version that can run for what, about 10 mins total? That would get them early data on TPS under actual operating conditions.
It's a cliche but once you get to LEO you are "Halfway to anywhere." Payload can always be increased but if you can't survive reentry
TPS is looking like the long pole in the tent.
I doubt SpaceX would deliberately remove TPS or flaps for a test launch, as any post-mission recovery testing is essentially 'free', but if the choice was not flying or flying a vehicle with TPS known to be sub-par, they'd still fly and get what data they can get for the phases of EDL it survives rather than waiting for a perfected vehicle.
If we unwind a year or so, NSF consensus (and Musk statements?) had TPS as the long pole. No surprises here.I think the actual pacing item is prep of the booster itself ("robustness upgrades" for B7) + static fires, nothing to do with heat shield.This seems doubtful. :(
Having gone through so many iterations of Raptor it should be possible to deliver enough of a standard version that can run for what, about 10 mins total? That would get them early data on TPS under actual operating conditions.
It's a cliche but once you get to LEO you are "Halfway to anywhere." Payload can always be increased but if you can't survive reentry
TPS is looking like the long pole in the tent.
It's unclear if you're addressing the general case or the TPS naked builds we're seeing. If the latter, there's discussion in the StarLink thread that suggests that there might be a push to get some sats up via SS. If this is correct, some quick n dirty launches sans TPS might be in the works. There are good arguments both ways.If you can't survive re-entry then SpaceX "merely" have a F9-style partially reusable vehicle capable of super-heavy-lift at a lower cost/kg than F9. Starship recovery and re-use are desirable in the long term for further cost reduction and for improved schedule (not needing to build an additional 6 engines between launches), but a partially reusable Starship + Super Heavy stack is still a viable system for payloads of sufficient mass and value.I think the actual pacing item is prep of the booster itself ("robustness upgrades" for B7) + static fires, nothing to do with heat shield.This seems doubtful. :(
Having gone through so many iterations of Raptor it should be possible to deliver enough of a standard version that can run for what, about 10 mins total? That would get them early data on TPS under actual operating conditions.
It's a cliche but once you get to LEO you are "Halfway to anywhere." Payload can always be increased but if you can't survive reentry
TPS is looking like the long pole in the tent.
I doubt SpaceX would deliberately remove TPS or flaps for a test launch, as any post-mission recovery testing is essentially 'free', but if the choice was not flying or flying a vehicle with TPS known to be sub-par, they'd still fly and get what data they can get for the phases of EDL it survives rather than waiting for a perfected vehicle.
Laminar flow over wings has nothing to do with Starship.
Laminar flow over wings has nothing to do with Starship. That only matters if you’re trying to get good lift to drag ratio, which makes no difference to Starship as the Elonerons basically act as big drag brakes.Given the organization that did the work deals with aircraft and helicopters they normally talk in terms of wings, but in truth it's an issue with every part of an airborne vehicle.
Why the frowny face? LOL no concern trolling here…
and not a fatal problem with careful engineering.That would be a fair description of the Shuttles safety record regarding its heat shield.
and not a fatal problem with careful engineering.That would be a fair description of the Shuttles safety record regarding its heat shield.
Ya, a chunk the "heat shield" of the External Tank was run into by the RCC wing leading edge "heat shield" of the Orbiter at over 500 mph closure. "RCC is hard and stout and afterall, it was JUST foam. Just a possible issue with processing for next mission, no safety of flight issue." Ya-but-no.and not a fatal problem with careful engineering.That would be a fair description of the Shuttles safety record regarding its heat shield.
Yeah, they worked around it at great cost.
When they did lose a Shuttle due to the heat shield failing and the wings falling off, it was another thing that caused the problem.
Ya, a chunk the "heat shield" of the External Tank was run into by the RCC wing leading edge "heat shield" of the Orbiter at over 500 mph closure. "RCC is hard and stout and afterall, it was JUST foam. Just a possible issue with processing for next mission, no safety of flight issue." Ya-but-no.and not a fatal problem with careful engineering.That would be a fair description of the Shuttles safety record regarding its heat shield.
Yeah, they worked around it at great cost.
When they did lose a Shuttle due to the heat shield failing and the wings falling off, it was another thing that caused the problem.
Ya, a chunk the " heat shield" of the External Tank was run into by the RCC wing leading edge "heat shield" of the Orbiter at over 500 mph closure. "RCC is hard and stout and afterall, it was JUST foam. Just a possible issue with processing for next mission, no safety of flight issue." Ya-but-no.Always you must watch the assumptions. :(
Ya, a chunk the "heat shield" of the External Tank was run into by the RCC wing leading edge "heat shield" of the Orbiter at over 500 mph closure. "RCC is hard and stout and afterall, it was JUST foam. Just a possible issue with processing for next mission, no safety of flight issue." Ya-but-no.and not a fatal problem with careful engineering.That would be a fair description of the Shuttles safety record regarding its heat shield.
Yeah, they worked around it at great cost.
When they did lose a Shuttle due to the heat shield failing and the wings falling off, it was another thing that caused the problem.
I didn't mean to be cheering for the Shuttle solution. There were several large problems with their approach. I just meant to say it wasn't fragile tiles or turbulent flow that got them, it was having a large TPS acreage exposed on the way up where stuff could fall on it.Actually it was fragile tile and turbulent flow. RCC panels were only on the wing leading edge and nose. Everything else were either various kinds of blanket topside, or tiles bottom side. But all of them were backed by the skin, which would have given them some "bounce." The wing leading edge had nothing behind it. . If it had it (arguably) would have survived the impact. That cavity acted as a trap for very high speed airflow. The rest is history.
Bringing it back on topic, Starship has lessened this problem by its configuration, but not eliminated it.Since the TPS is on SS, not SH there is nothing above that to shed stuff to hit its tiles, apart from a) Hail stones on the way up (does anyone seriously think they would launch during a hail storm?) b) Metorites
Quote from: ActionBringing it back on topic, Starship has lessened this problem by its configuration, but not eliminated it.Since the TPS is on SS, not SH there is nothing above that to shed stuff to hit its tiles, apart from a) Hail stones on the way up (does anyone seriously think they would launch during a hail storm?) b) Metorites
The TPS acreage on Starship is large and exposed on the way up. It's not cozied up next to an ET known for having things fall off it, but it is out there in the airstream. Ice could fall off Starship and hit the flaps (not sure what we're calling them these days) quite easily. Tiles shed from high up could hit areas lower down. I think I'd ignore things like birdstrikes as being beyond what this level of technology can reasonably be expected to deal with. Anyway, it's definitely a better plan than Shuttle, but it still has the same problem.Practically that only works if the heatshield is underneath the vehicle, like a Bono plug nozzle design. Wrapping the whole S2 in a shroud strong enough to avoid damage is going to add a lot of mass to S2 and probably make slying off a failed S1 impossible. :(
The only way to 100% solve this problem is to have the heatshield covered or in a controlled environment on the way up. Dragon, for example, has its heatshield on the bottom where nothing can bang into it.
[Edit: Spelling]
I'd like to remind people of Mary Shafer's words. Mary was a Flight Engineer at NASA Dryden during a lot of test flying programmes. Every one was flown by a top class pilot after extensive preparation but there was casualty rate of about one pilot death a year throughout the 1950's. Her comment was "Insisting on perfect safety is for people who don't have the balls to live in the real world."
Everything has a level of risk. Normally this is a subject only actuaries concern themselves with. Some of those risks can be reduced, some cannot. Going to orbit, for a long time to come is going to be substantially more risky than taking a commercial airline flight or similar scheduled transport.
Quote from: ActionBringing it back on topic, Starship has lessened this problem by its configuration, but not eliminated it.Since the TPS is on SS, not SH there is nothing above that to shed stuff to hit its tiles, apart from a) Hail stones on the way up (does anyone seriously think they would launch during a hail storm?) b) Metorites
The TPS acreage on Starship is large and exposed on the way up. It's not cozied up next to an ET known for having things fall off it, but it is out there in the airstream. Ice could fall off Starship and hit the flaps (not sure what we're calling them these days) quite easily. Tiles shed from high up could hit areas lower down. I think I'd ignore things like birdstrikes as being beyond what this level of technology can reasonably be expected to deal with. Anyway, it's definitely a better plan than Shuttle, but it still has the same problem.
The only way to 100% solve this problem is to have the heatshield covered or in a controlled environment on the way up. Dragon, for example, has its heatshield on the bottom where nothing can bang into it.
[Edit: Spelling]
The TPS acreage on Starship is large and exposed on the way up. It's not cozied up next to an ET known for having things fall off it, but it is out there in the airstream. Ice could fall off Starship and hit the flaps (not sure what we're calling them these days) quite easily. Tiles shed from high up could hit areas lower down. I think I'd ignore things like birdstrikes as being beyond what this level of technology can reasonably be expected to deal with. Anyway, it's definitely a better plan than Shuttle, but it still has the same problem.Practically that only works if the heatshield is underneath the vehicle, like a Bono plug nozzle design. Wrapping the whole S2 in a shroud strong enough to avoid damage is going to add a lot of mass to S2 and probably make slying off a failed S1 impossible. :(
The only way to 100% solve this problem is to have the heatshield covered or in a controlled environment on the way up. Dragon, for example, has its heatshield on the bottom where nothing can bang into it.
[Edit: Spelling]
You can always have the second stage go up in a fairing. The X-37B does it that way, and Dreamchaser is intended to I believe. If you attach the fairing to the first stage like the Rocket Lab Neutron, it shouldn't even cost much payload.This is the dictionary use of "stage," not the common one, IE a stage that is required to deliver substantial velocity to get to orbit. Neither of your examples does so. They are basically passive payloads during ascent. You might like to consider how they would work if they carry crew and there is an emergancy. What happens then?
But yes, putting the heatshield on the bottom is probably the most sensible way to do it. It's definitely simpler and lends itself to easier reentry modes.Then that would not be the design SX is going with. It would be a totally different vehicle.
You can always have the second stage go up in a fairing. The X-37B does it that way, and Dreamchaser is intended to I believe. If you attach the fairing to the first stage like the Rocket Lab Neutron, it shouldn't even cost much payload.
Quote from: ActionBut yes, putting the heatshield on the bottom is probably the most sensible way to do it. It's definitely simpler and lends itself to easier reentry modes.Then that would not be the design SX is going with. It would be a totally different vehicle.
You can always have the second stage go up in a fairing. The X-37B does it that way, and Dreamchaser is intended to I believe. If you attach the fairing to the first stage like the Rocket Lab Neutron, it shouldn't even cost much payload.
They are payloads, not stages.
You can always have the second stage go up in a fairing. The X-37B does it that way, and Dreamchaser is intended to I believe. If you attach the fairing to the first stage like the Rocket Lab Neutron, it shouldn't even cost much payload.
They are payloads, not stages.
That makes no difference to the argument. They're sideways reentering vehicles with fragile heat shield technology, just like Starship. So they go up protected.
So it's your understanding that these vehicles are launched inside fairings, not for aerodynamic reasons, but to spare their "fragile" thermal protection. That's it?
How is enclosing an almost optimally bullet shaped spacecraft (that has to withstand atmospheric reentry) with a larger fairing going be an improvement?So it's your understanding that these vehicles are launched inside fairings, not for aerodynamic reasons, but to spare their "fragile" thermal protection. That's it?
I don't recall saying that that was the only reason, but I note that Dynasoar, which had a much tougher heatshield proposed IIRC, was supposed to go up exposed to the airflow.
But yeah, fair enough. Enclosing them in a fairing also has aerodynamic and structural benefits.
[Edit: Clarified to say that I think there can be more than one reason to go up shrouded.]
So it's your understanding that these vehicles are launched inside fairings, not for aerodynamic reasons, but to spare their "fragile" thermal protection. That's it?
I don't recall saying that that was the only reason, but I note that Dynasoar, which had a much tougher heatshield proposed IIRC, was supposed to go up exposed to the airflow.
But yeah, fair enough. Enclosing them in a fairing also has aerodynamic and structural benefits.
[Edit: Clarified to say that I think there can be more than one reason to go up shrouded.]
How is enclosing an almost optimally bullet shaped spacecraft (that has to withstand atmospheric reentry) with a larger fairing going be an improvement?So it's your understanding that these vehicles are launched inside fairings, not for aerodynamic reasons, but to spare their "fragile" thermal protection. That's it?
I don't recall saying that that was the only reason, but I note that Dynasoar, which had a much tougher heatshield proposed IIRC, was supposed to go up exposed to the airflow.
But yeah, fair enough. Enclosing them in a fairing also has aerodynamic and structural benefits.
[Edit: Clarified to say that I think there can be more than one reason to go up shrouded.]
It's a benefit for X-37B and Dreamchaser. Ask Skyway - he's the one who brought it up...
You can always have the second stage go up in a fairing. The X-37B does it that way, and Dreamchaser is intended to I believe. If you attach the fairing to the first stage like the Rocket Lab Neutron, it shouldn't even cost much payload.
But yes, putting the heatshield on the bottom is probably the most sensible way to do it. It's definitely simpler and lends itself to easier reentry modes.
It's a benefit for X-37B and Dreamchaser. Ask Skyway - he's the one who brought it up...
Not true.
You cited these vehicles as an example before anyone else. I just answered it.
https://forum.nasaspaceflight.com/index.php?topic=50748.3140You can always have the second stage go up in a fairing. The X-37B does it that way, and Dreamchaser is intended to I believe. If you attach the fairing to the first stage like the Rocket Lab Neutron, it shouldn't even cost much payload.
But yes, putting the heatshield on the bottom is probably the most sensible way to do it. It's definitely simpler and lends itself to easier reentry modes.
You brought up the aerodynamics of the situation as an additional justification for the fairings in those cases. I'm sorry, I don't mean to be argumentative.
I've said before that SpaceX erred when they moved from carbon fiber and no longer had any practical diameter limit, not reconsidering sideways reentry followed by a mode switch to land vertically. They've been banging their heads against propellant management and heat shield problems for the last three years, and those problems were entirely optional.
Which begs the question how fragile are these tiles to begin with.
I've also been clear in stating I think this is an inferior option. It is though, for completeness, another way of protecting a fragile side-mount heat shield.
You're thinking of TUFROC, which is not what SpaceX are using.In that case they will have the fragility of Shuttle tiles, being about 95% air and hydroscopic.
SpaceX's tiles (seen thus far) are the same construction as the STS tiles: silica fibres are sintered into a brick, the brick is cut down to size, a thin Borosilicate glass coating is applies to some (front and part of each side) surfaces, and the finished tile is impregnated in its initial waterproofing agent (that burns off on first exposure to high temperature).
They are not multi-part, and they do not have an all-over RCG coating.
A Density comparison between chalk and Shuttle Orbiter tiles.
Chalk 156 lb/ft3 typically (varies from ~ 112 to 168 lb/ft3)
Shuttle Orbiter tiles:
LI-900 (black tiles on underside) 9 lb/ft3
LI-2200 (black higher strength around windows & landing gear doors) 22 lb/ft3
FRCI-12 (improved tiles to replace some LI tiles) 12 lb/ft3
LRSI-9 (white tiles on upper surfaces) 9 lb/ft3
LRSI-12 (white tiles on upper surfaces) 12 lb/ft3
BRI-18 (strongest & toughest tile produced, replacement for critical areas) 18 lb/ft3
Water 62.4 lb/ft3
Styrofoam packaging and insulation typically 1 to 2 lb/ft3
Conversion to metric:
1 lb/ft3 is equivalent to 0.016 g/cm3 or 16.0 kg/m3
You brought up the aerodynamics of the situation as an additional justification for the fairings in those cases. I'm sorry, I don't mean to be argumentative.
Fair enough. That's ok.
I've said before that SpaceX erred when they moved from carbon fiber and no longer had any practical diameter limit, not reconsidering sideways reentry followed by a mode switch to land vertically. They've been banging their heads against propellant management and heat shield problems for the last three years, and those problems were entirely optional.
Huh?
Starship was always going to re-enter side on when it was going to be made from carbon fibre. The exact landing maneuver was never very clear but I'm sure it would have involved some sort of flip and burn, therefore not making prop management any different.
The switch to stainless steel has nothing at all to do with the heat shield being on the side, it was always this way.
I've said before that SpaceX erred when they moved from carbon fiber and no longer had any practical diameter limit, not reconsidering sideways reentry followed by a mode switch to land vertically. They've been banging their heads against propellant management and heat shield problems for the last three years, and those problems were entirely optional.
Huh?
Starship was always going to re-enter side on when it was going to be made from carbon fibre. The exact landing maneuver was never very clear but I'm sure it would have involved some sort of flip and burn, therefore not making prop management any different.
The switch to stainless steel has nothing at all to do with the heat shield being on the side, it was always this way.
I don't want to derail the heatshield thread with that point, but I will briefly explain it. My understanding is that carbon fiber limited SpaceX in the size and shape of vehicle they could propose, because of the need for a very large curing oven among other things. So they proposed a long and skinny second stage that looked like most modern expendable rockets. If you have to have a long and skinny second stage, side entry kind of makes sense. When they switched to steel, they no longer had to have that shape and could have rethought reentry and landing.
I've said before that SpaceX erred when they moved from carbon fiber and no longer had any practical diameter limit, not reconsidering sideways reentry followed by a mode switch to land vertically. They've been banging their heads against propellant management and heat shield problems for the last three years, and those problems were entirely optional.
Huh?
Starship was always going to re-enter side on when it was going to be made from carbon fibre. The exact landing maneuver was never very clear but I'm sure it would have involved some sort of flip and burn, therefore not making prop management any different.
The switch to stainless steel has nothing at all to do with the heat shield being on the side, it was always this way.
I don't want to derail the heatshield thread with that point, but I will briefly explain it. My understanding is that carbon fiber limited SpaceX in the size and shape of vehicle they could propose, because of the need for a very large curing oven among other things. So they proposed a long and skinny second stage that looked like most modern expendable rockets. If you have to have a long and skinny second stage, side entry kind of makes sense. When they switched to steel, they no longer had to have that shape and could have rethought reentry and landing.
Starship needs a small ballistic coefficient and a an L/D max in the range of 0.5-1.0 to control heating and g loads. This requires a lot of reentry area. I don't see how this can be accomplished with an axial layout without compromising ascent performance. Care to provide a sketch and some numbers?
John
The goal is landing on Mars and Earth with the same second stage. I have not seen a capsule concept that is capable of that. (To be very fair I haven't looked very hard but I do pay attention here and have never seen one proposed)I've said before that SpaceX erred when they moved from carbon fiber and no longer had any practical diameter limit, not reconsidering sideways reentry followed by a mode switch to land vertically. They've been banging their heads against propellant management and heat shield problems for the last three years, and those problems were entirely optional.
Huh?
Starship was always going to re-enter side on when it was going to be made from carbon fibre. The exact landing maneuver was never very clear but I'm sure it would have involved some sort of flip and burn, therefore not making prop management any different.
The switch to stainless steel has nothing at all to do with the heat shield being on the side, it was always this way.
I don't want to derail the heatshield thread with that point, but I will briefly explain it. My understanding is that carbon fiber limited SpaceX in the size and shape of vehicle they could propose, because of the need for a very large curing oven among other things. So they proposed a long and skinny second stage that looked like most modern expendable rockets. If you have to have a long and skinny second stage, side entry kind of makes sense. When they switched to steel, they no longer had to have that shape and could have rethought reentry and landing.
Starship needs a small ballistic coefficient and a an L/D max in the range of 0.5-1.0 to control heating and g loads. This requires a lot of reentry area. I don't see how this can be accomplished with an axial layout without compromising ascent performance. Care to provide a sketch and some numbers?
John
A capsule shape on top of a regular super heavy seems like the obvious alternative. I believe Stoke Space Technologies is proposing something vaguely like it.
It would not have the same cross-range and it would have moderately higher-g reentry, if you feel those things are very important. The trade would be that you get better structural mass fraction, easier reentry more amenable to tougher heatshield solutions, and no mode switch on landing.
Starship needs a small ballistic coefficient and a an L/D max in the range of 0.5-1.0 to control heating and g loads. This requires a lot of reentry area. I don't see how this can be accomplished with an axial layout without compromising ascent performance. Care to provide a sketch and some numbers?Well lifting capsule designs IE with offset Cg, like Apollo managed 0.3. I think up to 0.5 is viable, but it gets tough about that.
John
I have not seen a capsule concept that is capable of that. (To be very fair I haven't looked very hard but I do pay attention here and have never seen one proposed)
I have not seen a capsule concept that is capable of that. (To be very fair I haven't looked very hard but I do pay attention here and have never seen one proposed)
In addition to the Dragon-based proposals, I think Gary Hudson proposed a system based on Phoenix to do that.
Phoenix? What is that? Do you have a reference?
John
Phoenix? What is that? Do you have a reference?
John
Phoenix was Hudson's name for a family of SSTO proposals, all of which were Bono-style big-capsule shapes, though they were small by the standards of SSTO proposals.
I can't find a free copy of the paper about using it for Mars, but the citation is: HUDSON, GARY. "Employing a chemical rocket VTOVL SSTO for high velocity Mars round trip travel." 24th Joint Propulsion Conference. 1988.
Very early ('Big Falcon Rocket' era) Starship designs were essentially scaled up Dragons utilising supersonic retropropulsion to expand the bow shock (works with canted-out engines, direct firing ones disrupt the shock) as Red Dragon was intended to demonstrate. Part of what killed Red Dragon was that the Starship design changed to sideways entry with aerodynamic lifting, so that demo mission became internally redundant.Was there any proposal for getting around cosine losses or were they just going to grit their teeth and bear it?
- Found the Phoenix papers. Gumdrop/capsule approach doesn't scale well for large, heavy, low ballistic coefficient vehicles. In order to handle the heating with known TPS you will need Shuttle, or lower, ballistic coefficient. To manage g's and atmospheric variations you will need the ability to generate an L/D of 0.5-1.0. A capsule shaped Starship design would need a diameter of ~26m to match Starship's sideways approach. Not very good for ascent aerodynamics.
- SSTO is a non-starter with current technology. You have to shave design margins pretty slim and payload fractions will be around 1% of gross, if all goes well. Any hiccups in development and you have no payload at all.
John
With the understanding you are talking about rocket based VTOVL SSTO.
- SSTO is a non-starter with current technology. You have to shave design margins pretty slim and payload fractions will be around 1% of gross, if all goes well. Any hiccups in development and you have no payload at all.
John
With the understanding you are talking about rocket based VTOVL SSTO.
- SSTO is a non-starter with current technology. You have to shave design margins pretty slim and payload fractions will be around 1% of gross, if all goes well. Any hiccups in development and you have no payload at all.
John
Excellent find about the table of ballistic coefficients BTW.
- Found the Phoenix papers. Gumdrop/capsule approach doesn't scale well for large, heavy, low ballistic coefficient vehicles. In order to handle the heating with known TPS you will need Shuttle, or lower, ballistic coefficient. To manage g's and atmospheric variations you will need the ability to generate an L/D of 0.5-1.0. A capsule shaped Starship design would need a diameter of ~26m to match Starship's sideways approach. Not very good for ascent aerodynamics.
- SSTO is a non-starter with current technology. You have to shave design margins pretty slim and payload fractions will be around 1% of gross, if all goes well. Any hiccups in development and you have no payload at all.
John
To the contrary, I think the big capsule shape is quite scalable; I'm not sure why you'd think otherwise. You have the picture right - it would look like a regular rocket with a hammerhead fairing, maybe a little more conical than cylindrical. Certainly entities like Boeing, Grumman, and Chrysler thought the big capsule made sense and proposed tremendously large vehicles with immense payloads. They should have no problem achieving 3-g reentries, usually proposing cg-offsets or small aerodynamic features. Maybe you think you need better than that, but I'm not sure why you would. Plus, with lower total heat reentries they're amenable to ablatives, convection cooling, transpiration, or even heat sink heat shields.
The SSTO part of the Phoenix paper is not what I meant to point to - it's not terribly relevant to the current discussion. Suffice it to say, if it was feasible to perform the proposed mission with a capsule-style SSTO, it would surely be feasible to perform it with a capsule-style second stage of a TSTO which would have much bigger margins. Otherwise, I think the paper is kind of neat. It reads like a first draft of the Starship architecture, with an RLV refueled in LEO and then sent to Mars and back. It predates a lot of the thinking on Mars in situ resource utilization, so it suggests some scheme with the Martian moons, but I can't really fault the guy for not inventing everything. Clearly he was born thirty years too soon.
Deceleration was intended to be more from the 'inflated' shock rather than the retropropulsion, so the angle was a feature rather than a bug.Very early ('Big Falcon Rocket' era) Starship designs were essentially scaled up Dragons utilising supersonic retropropulsion to expand the bow shock (works with canted-out engines, direct firing ones disrupt the shock) as Red Dragon was intended to demonstrate. Part of what killed Red Dragon was that the Starship design changed to sideways entry with aerodynamic lifting, so that demo mission became internally redundant.Was there any proposal for getting around cosine losses or were they just going to grit their teeth and bear it?
- I should have been clearer. As the vehicle mass and volume grows (assuming constant vehicle density), the capsule shape will get flatter to maintain ballistic coefficient. This is the direct result of the cube-square relationship between volume and area. Fine for reentry but, it makes ascent through an atmosphere harder and harder.
- My primary concern is ascent. The supersonic drag of a capsule shaped vehicle with a 26 m diameter will be ~10x larger on ascent than Starship (see attached diagram). Some of this can be offset by lowering thrust to weight of the booster, but at the expense of gravity losses. It will have higher losses and thus will require higher propellant mass ratio.
- The diagram shows a capsule design with the same volume and reentry area as the Starship. Each square is 3 meters. I superimposed the capsule's circular reentry area on top of the Starship sideview. I sketched in a 520m^2 rectangle to show that it more or less matches the Starship dimensions. I hope this helps.
John
If the second stage was VTVL, it would be flying by nowThe second stage IS VTVL, and it HAS been flying.
I meant cosine losses on ascent. Or was it expected to have separate engines for orbital insertion? And if so, where would they have been placed?Deceleration was intended to be more from the 'inflated' shock rather than the retropropulsion, so the angle was a feature rather than a bug.Very early ('Big Falcon Rocket' era) Starship designs were essentially scaled up Dragons utilising supersonic retropropulsion to expand the bow shock (works with canted-out engines, direct firing ones disrupt the shock) as Red Dragon was intended to demonstrate. Part of what killed Red Dragon was that the Starship design changed to sideways entry with aerodynamic lifting, so that demo mission became internally redundant.Was there any proposal for getting around cosine losses or were they just going to grit their teeth and bear it?
Though remember that this design was dropped because it traded poorly against an unpowered aerodynamic lifting entry (propellant mass vs. structural mass), at least at Starship's scale. Might trade better at a different scale, and there is a gulf between vehicles the size of Starship, and the largest viable pure drag capsule for Mars entry (MSL is close to that limit) where retropropulsion, inflatable decelerators, negative lift trajectories, etc, can play in the trade space.
If the second stage was VTVL, it would be flying by now, and we wouldn't have this heatshield thread.
- SSTO by any known means is pretty iffy. I have modeled all the various approaches over the years for the USAF.I've always found that any modelling's realism is only as good as the realism of the assumptions used to set it up. GIGO is eternal :(
- Best (largest payload to empty wt. & lowest growth factor) SSTO approaches my team modeled over the years were:The SCramjet result is truly astonishing given AFAIK the best T/W of one of these is 4:1, and they need a big rocket to get they up to operating speed.
- VTOHL (or VTOVL) tri-propellant (LOx, LCH4, LH2) rocket
- VTOHL (or VTOVL) tri-propellant (LOx, LCH4, LH2) rocket-scramjet
- All HTO concepts always faired poorly due to their large heavy wings, propulsion systems and takeoff gear. They have great EIsp buWith the understanding that you are talking about air breathing HTO. AFAIK there is no reason an HTO would have any better Isp than a VTO rocket.
t horrible ln(Mi/Mf). DV = g EIsp x ln(Mi/Mf).
- All SSTO concepts require the best available technologyTrue.
and have relatively low TRLs. They are risky propositions.Although there has been significant work by some companies to raise those TRL's.
John
Sorry if it's come up before, but has there been discussion of larger, slab-like TPS tiles to replace hundreds of individual tiles?Some earlier in the thread. There was a NASA Tech Brief from the 80's or 90's that described a method of slip casting the tiles over a porous mold that was under a slight vacuum to draw the water through it. This allowed near net shape slabs to match contours without machining. The test pieces were IIRC 18"x18" IE 9 standard tiles in 1. Apparently there not worried about thermal effects at this scale.
I suppose the obvious problem is thermal expansion, which is way more manageable with a small hexagonal tile than a single rectangular tile that stretches across the entire ship. But the upside is, assuming the tiles follow the shuttle recipe exactly and need to be replaced with waterproofed ones every flight, the replacement process for large portions of the ship - anything with simple geometry over a large area, is arguably fasterWaterproofing something so large is likely to be tricky. The small tiles each had a specific injection hole through the thin, brittle glass coating for injection of the waterproofing compound. I'd find it very doubtful that one hole would allow the fluid to penetrate a significantly bigger area. My instinct would be you'd need multiple holes.
So how would this craft scrub off velocity? A capsule? Which earlier in the thread was shown to have to be huge and cause other problems. Otherwise you're back to this whole heat shield issue. Also you're assuming that the reason starship isn't flying right now is the heat shield (it could be gse, ffa approval, raptor 2 problems or anything else). There are thousands of pages on this part of the website talking about design tradeoffs. People argue about one part and ignore everything else that has to work in sync to make the whole system work.If the second stage was VTVL, it would be flying by now, and we wouldn't have this heatshield thread.
If the second stage was [conventional] VTVL [as described on the past few pages], it would be flying [regularly, more than once] by now, and we wouldn't have this heatshield thread.
- This is really not the place for this alternative design discussion, so let me end with one of our reports that covers quite a few alternative designs, unfortunately it does not include a SSTO VTHL or VTVL rocket. Wish it did.Thanks for this. What a very interesting collection of authors in one place :)
John
- This is really not the place for this alternative design discussion, so let me end with one of our reports that covers quite a few alternative designs, unfortunately it does not include a SSTO VTHL or VTVL rocket. Wish it did.Thanks for this. What a very interesting collection of authors in one place :)
John
Sorry if it's come up before, but has there been discussion of larger, slab-like TPS tiles to replace hundreds of individual tiles?The big problem is not breaking the thing. A large shell made of sintered ceramic is incredibly fragile. I'd be willing to bet it would not even come vaguely close to being self-supporting. If you embed a structural support into it, you are now adding non-functional dry mass. Even if you try and get away with only external handling equipment (e.g. similar to how the STS orbiter payload bay doors required external frames if opened in a 1g environment) then you need to figure out how to attach it to the tank wall in a way that supports it across the entire surface (so a lot of blind attachment points. And ones that need to be unlatched remotely if you ever want to remove it intact) without restraining it when it expands and contracts between cryogenic and re-entry conditions. Along with all the dewatering and waterproofing issues mentioned. And the difficulty in fabricating such an item - first, construct the world's largest monolithic 2200°C furnace...
I suppose the obvious problem is thermal expansion, which is way more manageable with a small hexagonal tile than a single rectangular tile that stretches across the entire ship. But the upside is, assuming the tiles follow the shuttle recipe exactly and need to be replaced with waterproofed ones every flight, the replacement process for large portions of the ship - anything with simple geometry over a large area, is arguably faster
Sorry if it's come up before, but has there been discussion of larger, slab-like TPS tiles to replace hundreds of individual tiles?The big problem is not breaking the thing. A large shell made of sintered ceramic is incredibly fragile. I'd be willing to bet it would not even come vaguely close to being self-supporting. If you embed a structural support into it, you are now adding non-functional dry mass. Even if you try and get away with only external handling equipment (e.g. similar to how the STS orbiter payload bay doors required external frames if opened in a 1g environment) then you need to figure out how to attach it to the tank wall in a way that supports it across the entire surface (so a lot of blind attachment points. And ones that need to be unlatched remotely if you ever want to remove it intact) without restraining it when it expands and contracts between cryogenic and re-entry conditions. Along with all the dewatering and waterproofing issues mentioned. And the difficulty in fabricating such an item - first, construct the world's largest monolithic 2200°C furnace...
I suppose the obvious problem is thermal expansion, which is way more manageable with a small hexagonal tile than a single rectangular tile that stretches across the entire ship. But the upside is, assuming the tiles follow the shuttle recipe exactly and need to be replaced with waterproofed ones every flight, the replacement process for large portions of the ship - anything with simple geometry over a large area, is arguably faster
You earn yourself a lot of extra headaches, for no real benefit.
A question: If we suppose that too many tiles fall off the ship and it does not survive re-entry, would adding a thin ablative layer under the tiles (replacing or in addition to the thermal blankets) be too heavy? Too expensive? Is it even possible?Since you don't know a-priori which tile will fail, and at what point in the EDL sequence (e.g. worst case is the tile fails before entry starts), then you'd need to apply an ablative heatshield across the entire vehicle capable of surviving the entire EDL sequence. At that point, you've added the mass of an entire second TPS to the vehicle.
A question: If we suppose that too many tiles fall off the ship and it does not survive re-entry, would adding a thin ablative layer under the tiles (replacing or in addition to the thermal blankets) be too heavy? Too expensive? Is it even possible?Well there is a flexible version of both SIRCA and PICA ablatives that can be cut with a (sharp) knife. This makes working around holes, hatches etc much quicker and easier.
Since you don't know a-priori which tile will fail, and at what point in the EDL sequence (e.g. worst case is the tile fails before entry starts), then you'd need to apply an ablative heatshield across the entire vehicle capable of surviving the entire EDL sequence. At that point, you've added the mass of an entire second TPS to the vehicle.That would be the worst case scenario. :(
Dragon TPS would has a more benign re-entry environment than Starship sees.Since you don't know a-priori which tile will fail, and at what point in the EDL sequence (e.g. worst case is the tile fails before entry starts), then you'd need to apply an ablative heatshield across the entire vehicle capable of surviving the entire EDL sequence. At that point, you've added the mass of an entire second TPS to the vehicle.That would be the worst case scenario. :(
I guess to get a baseline for this you'd need to find out how much ablative is burnt off the Dragon heat shield on reentry. It's the only one that runs the full range orbital velocity to zero.
Anyone have any numbers for this?
Hmmm... So it is the tiles or nothing? No back-up possible.
I think the ship can survive losing a few tiles here and there, but we have to see if that is true or just what we hope for.
Btw, there are two types of lost tiles. Those lost on launch (could in theory be repaired on orbit) and those lost at some point during re-entry, which would just need some help to make it down.
Or will losing cargo ships now and then be acceptable and the cost of doing business?
Dragon TPS would has a more benign re-entry environment than Starship sees.I'm aware of the difference between an ablative and a radiative TPS, as well as the difference in the form of the heat pulse they are designed to cope with.
For ablative TPS, entry trajectory is designed to reduce total thermal input, with high peak temperatures being acceptable. Too much total heat soaks through the TPS and the system fails, but higher peak heat for a short time means less total ablation and less heat soak. That's the sort of trajectory Dragon flies, which is limited more by crew (and structural) desired g tolerance than peak heating.
For a radiative TPS (like Starship's) the goal is to keep peak heating within acceptable limits, with total thermal input being much less of an issue. That's the sort of trajectory Starship flies. Flying PICA-X in the same environment is liable to burn through a much thicker layer whilst also heating up the backside to a higher temperature.
Hmmm... So it is the tiles or nothing? No back-up possible.Not at all, but a)No previous vehicle has had a 2nd heatshield behind the first b)Any option adds weight, so the question is do you really need it?
I think the ship can survive losing a few tiles here and there, but we have to see if that is true or just what we hope for.You're probably right. It comes down to 2 questions. Where is the tile(s) lost and whenin the trajectory. If it's a single tile from the top side (as it comes in side on) just as it's horizontal speed drops to near zero to an Earth landing then the answer is probably yes. Lose it from the lower side as it start to decellerate (IE at near orbital speed) and it probably won't.
Btw, there are two types of lost tiles. Those lost on launch (could in theory be repaired on orbit) and those lost at some point during re-entry, which would just need some help to make it down.Actually tiles could be lost any time during the ascent trajectory, not just launch.
Or will losing cargo ships now and then be acceptable and the cost of doing business?
Hmmm... So it is the tiles or nothing? No back-up possible.Not at all, but a)No previous vehicle has had a 2nd heatshield behind the first b)Any option adds weight, so the question is do you really need it?
Quote from: RamsesBicI think the ship can survive losing a few tiles here and there, but we have to see if that is true or just what we hope for.You're probably right. It comes down to 2 questions. Where is the tile(s) lost and whenin the trajectory. If it's a single tile from the top side (as it comes in side on) just as it's horizontal speed drops to near zero to an Earth landing then the answer is probably yes. Lose it from the lower side as it start to decellerate (IE at near orbital speed) and it probably won't.Quote from: RamsesBicBtw, there are two types of lost tiles. Those lost on launch (could in theory be repaired on orbit) and those lost at some point during re-entry, which would just need some help to make it down.Actually tiles could be lost any time during the ascent trajectory, not just launch.
Or will losing cargo ships now and then be acceptable and the cost of doing business?
In practice with the amount of cargo Musk plans to send to mars (about 9 for every passenger carrier IIRC) the answer would have to be yes. :(
Except since the same design is also the passenger carrier then if it does happen then it's going to have to be fixed and proved to be fixed, as they will not be astronaughts, they will be "spaceflight participants" as the FAA calls them. Lower levels of risk will be expected (by the FAA if no one else) and also demonstrated either by a lot of flights or a detailed mathematical analysis whose assumptions can be justified.
Re: loosing tiles. I can't put my finger on it but there has been a NASA paper linked on NSF showing a relationship between radius of curvature and shock stand-off.SS does not enter "nose" first. It enters belly first. All references to "nose radius" in the re-entry literature refer to the curvature of the entering body in its direction of travel. If the tippy-tip TPS falls off, I don't know how to calculate the "radius" of the result. The Starship nose is sticking out toward the side of the plasma flow.
Assume the very tippy tip tile on the nose were lost. The radius of curvature would normally be the nose radius. Remove the tile and the radius of curvature that is of interest would be the top edge of the next tile down on the centerline. This edge is sharp and the radius of curvature of the shock front would be correspondingly small. My guess is that there would be some risk of shock impingement where the tile is missing. If the shock does not impinge and the shock stand-off distance small, heat input might be mitigated by any cryo cooling the header tank would give. Then the problem becomes landing propellant loss.
The entire centerline would be a concern with the the (I'm at a loss for the correct word) point towards the bottom of the ogive that is the first point of atmospheric 'contact' being of special concern. Moving away from the centerline, the shock stand-off distance increases and the risk associated with tile loss goes down.
This looks like a map for a backup TPS system, if future experience warrants. All the fiddly shapes, including the fins, makes my brain hurt but there may be a similar map here too. Key point: a backup TPS need not be full sized or of constant thickness.
The nose cone has glued tiles, just as the Shuttle had. Those don't fall off, unless they were not glued properly. (Anyone watching Starbase live today would have seen how hard it is to remove glued tiles. Chisel and big hammer needed.)Emphasis mine.
The ones most in danger imho are in the middle of the ship, held by studs. If one is not flush enough to the ones around it that corner could break off. If a tiles is not installed the correct way it could fall off too.
What no one can know for sure, until at least the first orbital flight, is whether or not losing one tile causes the loss of others around it. I don't know what kind of forces the plasma can exert on a tile, besides the heat. Is it capable of getting under the next tile and flicking it out?
Starship entry AoA is ~70°. The nose still still be first, and since the nose itself has an angle of ~60°, the stagnation point will just be a little to the nadir of the very tippy top.Re: loosing tiles. I can't put my finger on it but there has been a NASA paper linked on NSF showing a relationship between radius of curvature and shock stand-off.SS does not enter "nose" first. It enters belly first. All references to "nose radius" in the re-entry literature refer to the curvature of the entering body in its direction of travel. If the tippy-tip TPS falls off, I don't know how to calculate the "radius" of the result. The Starship nose is sticking out toward the side of the plasma flow.
Assume the very tippy tip tile on the nose were lost. The radius of curvature would normally be the nose radius. Remove the tile and the radius of curvature that is of interest would be the top edge of the next tile down on the centerline. This edge is sharp and the radius of curvature of the shock front would be correspondingly small. My guess is that there would be some risk of shock impingement where the tile is missing. If the shock does not impinge and the shock stand-off distance small, heat input might be mitigated by any cryo cooling the header tank would give. Then the problem becomes landing propellant loss.
The entire centerline would be a concern with the the (I'm at a loss for the correct word) point towards the bottom of the ogive that is the first point of atmospheric 'contact' being of special concern. Moving away from the centerline, the shock stand-off distance increases and the risk associated with tile loss goes down.
This looks like a map for a backup TPS system, if future experience warrants. All the fiddly shapes, including the fins, makes my brain hurt but there may be a similar map here too. Key point: a backup TPS need not be full sized or of constant thickness.
Starship entry AoA is ~70°. The nose still still be first, and since the nose itself has an angle of ~60°, the stagnation point will just be a little to the nadir of the very tippy top.Indeed. SS's entry is quite Shuttle like. I'm reminded that Reinforced Carbon Carbon was only used on two areas of the Shuttle TPS, the wing leading edges and the nose area.
The nose cone has glued tiles, just as the Shuttle had. Those don't fall off, unless they were not glued properly. (Anyone watching Starbase live today would have seen how hard it is to remove glued tiles. Chisel and big hammer needed.)Emphasis mine.
The ones most in danger imho are in the middle of the ship, held by studs. If one is not flush enough to the ones around it that corner could break off. If a tiles is not installed the correct way it could fall off too.
What no one can know for sure, until at least the first orbital flight, is whether or not losing one tile causes the loss of others around it. I don't know what kind of forces the plasma can exert on a tile, besides the heat. Is it capable of getting under the next tile and flicking it out?
During STS times this was known as the "zipper effect".
The nose cone has glued tiles, just as the Shuttle had. Those don't fall off, unless they were not glued properly. (Anyone watching Starbase live today would have seen how hard it is to remove glued tiles. Chisel and big hammer needed.)Emphasis mine.
The ones most in danger imho are in the middle of the ship, held by studs. If one is not flush enough to the ones around it that corner could break off. If a tiles is not installed the correct way it could fall off too.
What no one can know for sure, until at least the first orbital flight, is whether or not losing one tile causes the loss of others around it. I don't know what kind of forces the plasma can exert on a tile, besides the heat. Is it capable of getting under the next tile and flicking it out?
During STS times this was known as the "zipper effect".
The "zipper effect" was a concern during shuttle development. But flight experience proved that the "zipper effect" was highly unlikely to be triggered by a lost tile. Increased turbulence and thermal loading to the exposed side of the next tile was observed, but was not strong enough to force the debonding of that next tile. STS-27 being the best observations of this lack of zipper effect.
That glue the part of the TPS with the lowest temperature limit (which was fine as the aluminum structure beneath was even worse). The studs will likely be fine from a temperature standpoint.The nose cone has glued tiles, just as the Shuttle had. Those don't fall off, unless they were not glued properly. (Anyone watching Starbase live today would have seen how hard it is to remove glued tiles. Chisel and big hammer needed.)Emphasis mine.
The ones most in danger imho are in the middle of the ship, held by studs. If one is not flush enough to the ones around it that corner could break off. If a tiles is not installed the correct way it could fall off too.
What no one can know for sure, until at least the first orbital flight, is whether or not losing one tile causes the loss of others around it. I don't know what kind of forces the plasma can exert on a tile, besides the heat. Is it capable of getting under the next tile and flicking it out?
During STS times this was known as the "zipper effect".
The "zipper effect" was a concern during shuttle development. But flight experience proved that the "zipper effect" was highly unlikely to be triggered by a lost tile. Increased turbulence and thermal loading to the exposed side of the next tile was observed, but was not strong enough to force the debonding of that next tile. STS-27 being the best observations of this lack of zipper effect.
Good to know. Thanks.
But Starship uses studs and the Shuttle used glue, so the result might not be the same.
Hmmm... So it is the tiles or nothing? No back-up possible.
I think the ship can survive losing a few tiles here and there, but we have to see if that is true or just what we hope for.
Hmmm... So it is the tiles or nothing? No back-up possible.
I think the ship can survive losing a few tiles here and there, but we have to see if that is true or just what we hope for.
I think part of the idea of the SS construction is that IS the backup. Note that before Columbia, STS-27 lost tiles and had the aluminum skin melt but fortunately there was a stainless steel mounting plate for the structure underneath and that saved it.
If you need still another backup heat shield in addition to the stainless steel and the thermal tiles, you probably want to improve the thermal tiles and fastening process in some way rather than add another redundancy. Or stick to doing reentry on Dragons, and accept a 1 in 10 vehicle loss on cargo runs of Starship.
Not sure if considered a part of Shuttle's development period or not, but the "zipper effect", or the lack thereof, was accentuated by media reports of "supposed tile losses" during OV-102 Columbia's transit atop the Shuttle Carrier Aircraft from California to Florida. What appeared to be larger sections of tiles that were lost during this SCA transit, were actually tile spacers that were installed onto the orbiter vehicle specifically for the delivery flight. While SOME tiles were indeed lost, the vast volumes of lost tiles due to this "zipper effect" were incorrect and hugely overstated. To the un-knowing, the off-nominal appearing "false tiles" appeared like missing or damaged tiles which combined with earlier worries from NASA engineers about the possibility of the "zipper effect" seemed to propagate the apparent myth of the "zipper effect". Another case or knowing "just enough to be dangerous". There's a LOT of this in the world of spaceflight enthusiasm.The nose cone has glued tiles, just as the Shuttle had. Those don't fall off, unless they were not glued properly. (Anyone watching Starbase live today would have seen how hard it is to remove glued tiles. Chisel and big hammer needed.)Emphasis mine.
The ones most in danger imho are in the middle of the ship, held by studs. If one is not flush enough to the ones around it that corner could break off. If a tiles is not installed the correct way it could fall off too.
What no one can know for sure, until at least the first orbital flight, is whether or not losing one tile causes the loss of others around it. I don't know what kind of forces the plasma can exert on a tile, besides the heat. Is it capable of getting under the next tile and flicking it out?
During STS times this was known as the "zipper effect".
The "zipper effect" was a concern during shuttle development. But flight experience proved that the "zipper effect" was highly unlikely to be triggered by a lost tile. Increased turbulence and thermal loading to the exposed side of the next tile was observed, but was not strong enough to force the debonding of that next tile. STS-27 being the best observations of this lack of zipper effect.
No, please. I understand SS will not reenter nose first. Reread the my post with the assumption of a realistic AoA.Re: loosing tiles. I can't put my finger on it but there has been a NASA paper linked on NSF showing a relationship between radius of curvature and shock stand-off.SS does not enter "nose" first. It enters belly first. All references to "nose radius" in the re-entry literature refer to the curvature of the entering body in its direction of travel. If the tippy-tip TPS falls off, I don't know how to calculate the "radius" of the result. The Starship nose is sticking out toward the side of the plasma flow.
Assume the very tippy tip tile on the nose were lost. The radius of curvature would normally be the nose radius. Remove the tile and the radius of curvature that is of interest would be the top edge of the next tile down on the centerline. This edge is sharp and the radius of curvature of the shock front would be correspondingly small. My guess is that there would be some risk of shock impingement where the tile is missing. If the shock does not impinge and the shock stand-off distance small, heat input might be mitigated by any cryo cooling the header tank would give. Then the problem becomes landing propellant loss.
The entire centerline would be a concern with the the (I'm at a loss for the correct word) point towards the bottom of the ogive that is the first point of atmospheric 'contact' being of special concern. Moving away from the centerline, the shock stand-off distance increases and the risk associated with tile loss goes down.
This looks like a map for a backup TPS system, if future experience warrants. All the fiddly shapes, including the fins, makes my brain hurt but there may be a similar map here too. Key point: a backup TPS need not be full sized or of constant thickness.
The nose cone has glued tiles, just as the Shuttle had. Those don't fall off, unless they were not glued properly. (Anyone watching Starbase live today would have seen how hard it is to remove glued tiles. Chisel and big hammer needed.)I've a hunch they'll start glueing the centerline tiles too. That'll suck for repair but the need for repair will go down. ISTM that the possibility of a missing tile starting a cascade is highest in the centerline. See previous post.
The ones most in danger imho are in the middle of the ship, held by studs. If one is not flush enough to the ones around it that corner could break off. If a tiles is not installed the correct way it could fall off too.
What no one can know for sure, until at least the first orbital flight, is whether or not losing one tile causes the loss of others around it. I don't know what kind of forces the plasma can exert on a tile, besides the heat. Is it capable of getting under the next tile and flicking it out?
Stagnation point! That's the term I was looking for. Thanks.Starship entry AoA is ~70°. The nose still still be first, and since the nose itself has an angle of ~60°, the stagnation point will just be a little to the nadir of the very tippy top.Re: loosing tiles. I can't put my finger on it but there has been a NASA paper linked on NSF showing a relationship between radius of curvature and shock stand-off.SS does not enter "nose" first. It enters belly first. All references to "nose radius" in the re-entry literature refer to the curvature of the entering body in its direction of travel. If the tippy-tip TPS falls off, I don't know how to calculate the "radius" of the result. The Starship nose is sticking out toward the side of the plasma flow.
Assume the very tippy tip tile on the nose were lost. The radius of curvature would normally be the nose radius. Remove the tile and the radius of curvature that is of interest would be the top edge of the next tile down on the centerline. This edge is sharp and the radius of curvature of the shock front would be correspondingly small. My guess is that there would be some risk of shock impingement where the tile is missing. If the shock does not impinge and the shock stand-off distance small, heat input might be mitigated by any cryo cooling the header tank would give. Then the problem becomes landing propellant loss.
The entire centerline would be a concern with the the (I'm at a loss for the correct word) point towards the bottom of the ogive that is the first point of atmospheric 'contact' being of special concern. Moving away from the centerline, the shock stand-off distance increases and the risk associated with tile loss goes down.
This looks like a map for a backup TPS system, if future experience warrants. All the fiddly shapes, including the fins, makes my brain hurt but there may be a similar map here too. Key point: a backup TPS need not be full sized or of constant thickness.
If glue turns out to be necessary to fix most tiles I wonder if it would make sense to switch to larger replaceable units, e.g. an entire barrel-section's worth of glued tiles on a lightweight structure. This is far from a 'rapidly reusable' ideal TPS but I could imagine a large supply of barrel sections being on hand, so if a Starship lands with a couple of broken tiles on the belly, you swap out its entire section in less time than a custom repair. It's far from ideal, and doesn't address the complex geometry sections but it would address ~70% of the TPS area?The nose cone has glued tiles, just as the Shuttle had. Those don't fall off, unless they were not glued properly. (Anyone watching Starbase live today would have seen how hard it is to remove glued tiles. Chisel and big hammer needed.)I've a hunch they'll start glueing the centerline tiles too. That'll suck for repair but the need for repair will go down. ISTM that the possibility of a missing tile starting a cascade is highest in the centerline. See previous post.
The ones most in danger imho are in the middle of the ship, held by studs. If one is not flush enough to the ones around it that corner could break off. If a tiles is not installed the correct way it could fall off too.
What no one can know for sure, until at least the first orbital flight, is whether or not losing one tile causes the loss of others around it. I don't know what kind of forces the plasma can exert on a tile, besides the heat. Is it capable of getting under the next tile and flicking it out?
Thermal expansion and contraction would crack such sections.If glue turns out to be necessary to fix most tiles I wonder if it would make sense to switch to larger replaceable units, e.g. an entire barrel-section's worth of glued tiles on a lightweight structure. This is far from a 'rapidly reusable' ideal TPS but I could imagine a large supply of barrel sections being on hand, so if a Starship lands with a couple of broken tiles on the belly, you swap out its entire section in less time than a custom repair. It's far from ideal, and doesn't address the complex geometry sections but it would address ~70% of the TPS area?The nose cone has glued tiles, just as the Shuttle had. Those don't fall off, unless they were not glued properly. (Anyone watching Starbase live today would have seen how hard it is to remove glued tiles. Chisel and big hammer needed.)I've a hunch they'll start glueing the centerline tiles too. That'll suck for repair but the need for repair will go down. ISTM that the possibility of a missing tile starting a cascade is highest in the centerline. See previous post.
The ones most in danger imho are in the middle of the ship, held by studs. If one is not flush enough to the ones around it that corner could break off. If a tiles is not installed the correct way it could fall off too.
What no one can know for sure, until at least the first orbital flight, is whether or not losing one tile causes the loss of others around it. I don't know what kind of forces the plasma can exert on a tile, besides the heat. Is it capable of getting under the next tile and flicking it out?
If the idea had merit I'm confident SpaceX engineers could work up expansion joints. The bigger question is how much weight would such a panelized approach add?
If the skin were aluminum and they didn't use a stress isolation pad yes.
Thermal expansion and contraction would crack such sections.
How does thermal expansion compare with expansion due to pressurization? I would think that pressurization would cause more on a tank that large.Thermal expansion and contraction would crack such sections.If glue turns out to be necessary to fix most tiles I wonder if it would make sense to switch to larger replaceable units, e.g. an entire barrel-section's worth of glued tiles on a lightweight structure. This is far from a 'rapidly reusable' ideal TPS but I could imagine a large supply of barrel sections being on hand, so if a Starship lands with a couple of broken tiles on the belly, you swap out its entire section in less time than a custom repair. It's far from ideal, and doesn't address the complex geometry sections but it would address ~70% of the TPS area?The nose cone has glued tiles, just as the Shuttle had. Those don't fall off, unless they were not glued properly. (Anyone watching Starbase live today would have seen how hard it is to remove glued tiles. Chisel and big hammer needed.)I've a hunch they'll start glueing the centerline tiles too. That'll suck for repair but the need for repair will go down. ISTM that the possibility of a missing tile starting a cascade is highest in the centerline. See previous post.
The ones most in danger imho are in the middle of the ship, held by studs. If one is not flush enough to the ones around it that corner could break off. If a tiles is not installed the correct way it could fall off too.
What no one can know for sure, until at least the first orbital flight, is whether or not losing one tile causes the loss of others around it. I don't know what kind of forces the plasma can exert on a tile, besides the heat. Is it capable of getting under the next tile and flicking it out?
No, please. I understand SS will not reenter nose first. Reread the my post with the assumption of a realistic AoA.Re: loosing tiles. I can't put my finger on it but there has been a NASA paper linked on NSF showing a relationship between radius of curvature and shock stand-off.SS does not enter "nose" first. It enters belly first. All references to "nose radius" in the re-entry literature refer to the curvature of the entering body in its direction of travel. If the tippy-tip TPS falls off, I don't know how to calculate the "radius" of the result. The Starship nose is sticking out toward the side of the plasma flow.
Assume the very tippy tip tile on the nose were lost. The radius of curvature would normally be the nose radius. Remove the tile and the radius of curvature that is of interest would be the top edge of the next tile down on the centerline. This edge is sharp and the radius of curvature of the shock front would be correspondingly small. My guess is that there would be some risk of shock impingement where the tile is missing. If the shock does not impinge and the shock stand-off distance small, heat input might be mitigated by any cryo cooling the header tank would give. Then the problem becomes landing propellant loss.
The entire centerline would be a concern with the the (I'm at a loss for the correct word) point towards the bottom of the ogive that is the first point of atmospheric 'contact' being of special concern. Moving away from the centerline, the shock stand-off distance increases and the risk associated with tile loss goes down.
This looks like a map for a backup TPS system, if future experience warrants. All the fiddly shapes, including the fins, makes my brain hurt but there may be a similar map here too. Key point: a backup TPS need not be full sized or of constant thickness.
AIUI, SS is intended to reenter with an AoA of ~70deg. This moves the point of first contact from the centerline of the barrel up onto the ogive. At this point there are two radii to consider. Up/down and left/right, and it gets complicated.
At the edge where the tippy tip tile is missing a new up/down radius is introduced along the centerline. Flow will 'flow' over the lip and most likely down to the newly exposed surface. The shock will most probably also make an adjustment around the lip but my dedicated CFD computer is down right now (/s) and I can't tell if there will be any shock impingement. Greatest danger might be the side face of the tile opposite the flow.
Down on the barrel, let's assume an AoA of 90deg. It makes the visualization easier. The shock front is closest along the centerline and compressive force and it's heating are greatest. Surface flow is from the centerline to the sides. Remove one centerline tile.
The compressive forces stay the same but are now on the skin, not a tile. AIUI, the shock front would dimple in at a rate determined by the radius of curvature of the tile edge. Here it gets interesting. With the shock front dimpling in and the missing tile forming a pocket, there may be a Venturi effect with the semi trapped flow excessively heating the adjacent tile edges. This effect decreases as the missing tile distance from the centerline increases.
This is admittedly all a mind experiment. The only number I have is 42, and Elon's already used it on SS.
The bow shock would be around half a meter away (bow shock standoff is about 1/9 of the radius of the curvature) and behind the shock you have stagnation point, i.e. the point where there's no major air movement.The problem is that once a tile is removed (or the TPS otherwise mechanically disrupted) you no longer have a radius equal to the radius of the vehicle. You have a radius equal to the lip of the edge of the adjacent tiles, which is a few mm at most. The shock in that region is then happy to reattach to the surface of the vehicle and allow hot gas to impinge on the vehicle.
No, as sebk stated the relevant radius of curvature has to do with how the gas flows around the vehicle and this will not change drastically for disruptions that are significantly smaller than the shock standoff distance.The bow shock would be around half a meter away (bow shock standoff is about 1/9 of the radius of the curvature) and behind the shock you have stagnation point, i.e. the point where there's no major air movement.The problem is that once a tile is removed (or the TPS otherwise mechanically disrupted) you no longer have a radius equal to the radius of the vehicle. You have a radius equal to the lip of the edge of the adjacent tiles, which is a few mm at most. The shock in that region is then happy to reattach to the surface of the vehicle and allow hot gas to impinge on the vehicle.
The dangers are shocks in the local (up to supersonic) flow and increased heat transfer downstream due to turbulence. The space shuttle flew experiments to study this where one tile had an up to 0.5 inch tall ridge with radii of a few mm (see for example the attached pdf) which did not suffer any damage.Interesting paper.
No, as sebk stated the relevant radius of curvature has to do with how the gas flows around the vehicle and this will not change drastically for disruptions that are significantly smaller than the shock standoff distance.The bow shock would be around half a meter away (bow shock standoff is about 1/9 of the radius of the curvature) and behind the shock you have stagnation point, i.e. the point where there's no major air movement.The problem is that once a tile is removed (or the TPS otherwise mechanically disrupted) you no longer have a radius equal to the radius of the vehicle. You have a radius equal to the lip of the edge of the adjacent tiles, which is a few mm at most. The shock in that region is then happy to reattach to the surface of the vehicle and allow hot gas to impinge on the vehicle.
The dangers are shocks in the local (up to supersonic) flow and increased heat transfer downstream due to turbulence. The space shuttle flew experiments to study this where one tile had an up to 0.5 inch tall ridge with radii of a few mm (see for example the attached pdf) which did not suffer any damage.
The CFD system is still down <g> so I'm trying to use my head and model this one air particle at a time. Again assume a 90deg. AoA for simplicity.No, please. I understand SS will not reenter nose first. Reread the my post with the assumption of a realistic AoA.Re: loosing tiles. I can't put my finger on it but there has been a NASA paper linked on NSF showing a relationship between radius of curvature and shock stand-off.SS does not enter "nose" first. It enters belly first. All references to "nose radius" in the re-entry literature refer to the curvature of the entering body in its direction of travel. If the tippy-tip TPS falls off, I don't know how to calculate the "radius" of the result. The Starship nose is sticking out toward the side of the plasma flow.
Assume the very tippy tip tile on the nose were lost. The radius of curvature would normally be the nose radius. Remove the tile and the radius of curvature that is of interest would be the top edge of the next tile down on the centerline. This edge is sharp and the radius of curvature of the shock front would be correspondingly small. My guess is that there would be some risk of shock impingement where the tile is missing. If the shock does not impinge and the shock stand-off distance small, heat input might be mitigated by any cryo cooling the header tank would give. Then the problem becomes landing propellant loss.
The entire centerline would be a concern with the the (I'm at a loss for the correct word) point towards the bottom of the ogive that is the first point of atmospheric 'contact' being of special concern. Moving away from the centerline, the shock stand-off distance increases and the risk associated with tile loss goes down.
This looks like a map for a backup TPS system, if future experience warrants. All the fiddly shapes, including the fins, makes my brain hurt but there may be a similar map here too. Key point: a backup TPS need not be full sized or of constant thickness.
AIUI, SS is intended to reenter with an AoA of ~70deg. This moves the point of first contact from the centerline of the barrel up onto the ogive. At this point there are two radii to consider. Up/down and left/right, and it gets complicated.
At the edge where the tippy tip tile is missing a new up/down radius is introduced along the centerline. Flow will 'flow' over the lip and most likely down to the newly exposed surface. The shock will most probably also make an adjustment around the lip but my dedicated CFD computer is down right now (/s) and I can't tell if there will be any shock impingement. Greatest danger might be the side face of the tile opposite the flow.
Down on the barrel, let's assume an AoA of 90deg. It makes the visualization easier. The shock front is closest along the centerline and compressive force and it's heating are greatest. Surface flow is from the centerline to the sides. Remove one centerline tile.
The compressive forces stay the same but are now on the skin, not a tile. AIUI, the shock front would dimple in at a rate determined by the radius of curvature of the tile edge. Here it gets interesting. With the shock front dimpling in and the missing tile forming a pocket, there may be a Venturi effect with the semi trapped flow excessively heating the adjacent tile edges. This effect decreases as the missing tile distance from the centerline increases.
This is admittedly all a mind experiment. The only number I have is 42, and Elon's already used it on SS.
Actually, on the center-spot (or center line at 90° AoA) behind the stagnation point there would be no local shock even if a tile fell off. The bow shock would be around half a meter away (bow shock standoff is about 1/9 of the radius of the curvature) and behind the shock you have stagnation point, i.e. the point where there's no major air movement. There will be turbulence and stuff (unless things are so smooth the flow is laminar) but they will be subsonic.
But as you'd start moving to the side, you'd start getting air movement again. If you'd move totally to the side you'd actually get supersonic flow (in the order of Mach 2.5 if I remember correctly; I could be badly wrong, though). So somewhere on the side of the barrel, likely at some point between 30° and 60° to the side you actually get supersonic flow behind the bow shock too. So that's the place where there's potential for shock impingement onto the skin if a tile is missing. OTOH heating would be less there, because bow shock standoff is significantly larger back there, and the flow has lower pressure (so it's colder and contains less heat to transfer).
You could (extremely roughly!) think about the skin of the vehicle and bow shock forming a kind of a nozzle through which the stagnation point air expands to escape behind the sides of the reentering vehicle.
What you're kind of describing is quite similar to how the effect of a neutron moderator was worked out from first principles in a book called "Elementary Pile Theory"
The CFD system is still down <g> so I'm trying to use my head and model this one air particle at a time. Again assume a 90deg. AoA for simplicity.
The heatshield is in vacuum so there are no aerodynamics. Then it encounters one particle of air directly on the centerline. The particle hits and that is one tiny bit of compressive heating to both the heatshield and the particle. The energetic particle is now conceptually sharing a frame of reference with the ship and being hot and energetic, rebounds.
A key concept here is 'mean free space' between air particles. As the air gets denser the mean free space goes down and a rebounding particle has an increasing chance of impacting an incoming* particle of air. When a rebounding particle hits an incoming particle a nascent shock wave forms.
That first partial that impacts an incoming particle would bounce back towards the ship and contribute again to compressive heating. The particle it impacted would also rebound and have some chance of hitting yet another incoming particle and the process would cascade. This is all at the stagnation point.
To one side or the other the process would follow this pattern but with a radial component. This is what forms the flow under the shock. Particles are always bleeding in from the shock and adding to the flow. Particles are always piling up and entering the ships frame of reference. This pileup is the shockwave.
Not sure where this is going. Gotta think on it some more. Somebody point me in the right direction if I'm off base.
* Really just unlucky enough to be in the way.
The CFD system is still down <g> so I'm trying to use my head and model this one air particle at a time. Again assume a 90deg. AoA for simplicity.No, please. I understand SS will not reenter nose first. Reread the my post with the assumption of a realistic AoA.Re: loosing tiles. I can't put my finger on it but there has been a NASA paper linked on NSF showing a relationship between radius of curvature and shock stand-off.SS does not enter "nose" first. It enters belly first. All references to "nose radius" in the re-entry literature refer to the curvature of the entering body in its direction of travel. If the tippy-tip TPS falls off, I don't know how to calculate the "radius" of the result. The Starship nose is sticking out toward the side of the plasma flow.
Assume the very tippy tip tile on the nose were lost. The radius of curvature would normally be the nose radius. Remove the tile and the radius of curvature that is of interest would be the top edge of the next tile down on the centerline. This edge is sharp and the radius of curvature of the shock front would be correspondingly small. My guess is that there would be some risk of shock impingement where the tile is missing. If the shock does not impinge and the shock stand-off distance small, heat input might be mitigated by any cryo cooling the header tank would give. Then the problem becomes landing propellant loss.
The entire centerline would be a concern with the the (I'm at a loss for the correct word) point towards the bottom of the ogive that is the first point of atmospheric 'contact' being of special concern. Moving away from the centerline, the shock stand-off distance increases and the risk associated with tile loss goes down.
This looks like a map for a backup TPS system, if future experience warrants. All the fiddly shapes, including the fins, makes my brain hurt but there may be a similar map here too. Key point: a backup TPS need not be full sized or of constant thickness.
AIUI, SS is intended to reenter with an AoA of ~70deg. This moves the point of first contact from the centerline of the barrel up onto the ogive. At this point there are two radii to consider. Up/down and left/right, and it gets complicated.
At the edge where the tippy tip tile is missing a new up/down radius is introduced along the centerline. Flow will 'flow' over the lip and most likely down to the newly exposed surface. The shock will most probably also make an adjustment around the lip but my dedicated CFD computer is down right now (/s) and I can't tell if there will be any shock impingement. Greatest danger might be the side face of the tile opposite the flow.
Down on the barrel, let's assume an AoA of 90deg. It makes the visualization easier. The shock front is closest along the centerline and compressive force and it's heating are greatest. Surface flow is from the centerline to the sides. Remove one centerline tile.
The compressive forces stay the same but are now on the skin, not a tile. AIUI, the shock front would dimple in at a rate determined by the radius of curvature of the tile edge. Here it gets interesting. With the shock front dimpling in and the missing tile forming a pocket, there may be a Venturi effect with the semi trapped flow excessively heating the adjacent tile edges. This effect decreases as the missing tile distance from the centerline increases.
This is admittedly all a mind experiment. The only number I have is 42, and Elon's already used it on SS.
Actually, on the center-spot (or center line at 90° AoA) behind the stagnation point there would be no local shock even if a tile fell off. The bow shock would be around half a meter away (bow shock standoff is about 1/9 of the radius of the curvature) and behind the shock you have stagnation point, i.e. the point where there's no major air movement. There will be turbulence and stuff (unless things are so smooth the flow is laminar) but they will be subsonic.
But as you'd start moving to the side, you'd start getting air movement again. If you'd move totally to the side you'd actually get supersonic flow (in the order of Mach 2.5 if I remember correctly; I could be badly wrong, though). So somewhere on the side of the barrel, likely at some point between 30° and 60° to the side you actually get supersonic flow behind the bow shock too. So that's the place where there's potential for shock impingement onto the skin if a tile is missing. OTOH heating would be less there, because bow shock standoff is significantly larger back there, and the flow has lower pressure (so it's colder and contains less heat to transfer).
You could (extremely roughly!) think about the skin of the vehicle and bow shock forming a kind of a nozzle through which the stagnation point air expands to escape behind the sides of the reentering vehicle.
The heatshield is in vacuum so there are no aerodynamics. Then it encounters one particle of air directly on the centerline. The particle hits and that is one tiny bit of compressive heating to both the heatshield and the particle. The energetic particle is now conceptually sharing a frame of reference with the ship and being hot and energetic, rebounds.
A key concept here is 'mean free space' between air particles. As the air gets denser the mean free space goes down and a rebounding particle has an increasing chance of impacting an incoming* particle of air. When a rebounding particle hits an incoming particle a nascent shock wave forms.
That first partial that impacts an incoming particle would bounce back towards the ship and contribute again to compressive heating. The particle it impacted would also rebound and have some chance of hitting yet another incoming particle and the process would cascade. This is all at the stagnation point.
To one side or the other the process would follow this pattern but with a radial component. This is what forms the flow under the shock. Particles are always bleeding in from the shock and adding to the flow. Particles are always piling up and entering the ships frame of reference. This pileup is the shockwave.
Not sure where this is going. Gotta think on it some more. Somebody point me in the right direction if I'm off base.
* Really just unlucky enough to be in the way.
Re: sebk and one particle at a time."Real gas effects" is the general term for this stuff. Historically they used a 7 element model for reentry from orbital velocity, about 7900m/s. At this speed ionization was not considered but you do get dissociation where O2 -> O + O and N2 -> N + N. This absorbs substantial energy and as was noted there is also photon emission. Whether they make to the skin or are aborbed in the gas layer can have significant effects. Given that temperature is a measure of a particles velocity an O2 "particle" is heavier than an O, so it's temperature will be lower. This is why the early ICBM warhead studies about enormous temperatures (able to melt tungsten for example) were so misleading.
Yeah, was trying to keep it simple and add complexities one at a time. The early example of a single partial impact is what happens before a bow shock forms. All heating is applied directly to the skin.
I was thinking about the various species. They're there, they're important but ISTM, irrelevant in assessing the flow impact of a missing tile. Thermal and chemical, but not flow.
Something I'm chewing on is charges. That first partial, it's gonna hit hard. Not only will it break apart into constituent atoms, it will also most probably shed an electron or two. In the grand scheme of things charge will be conserved but are there local effects? If there are, this might affect flow.
These results will of course be mostly boring "nothing happens" if it is a good TPS material.Should be "nothing happens."
I have been thinking about the way the TPS tiles are made and how they are attached to the hull.Cabling large enough to carry welding current for the pins would leave holes or gaps in the tiles that would negate the tiles purpose. Leaving the cables in place would create a thermal path to the pins and underlying surface. If the cables stay in place the weight increase would most likely at least double the weight of each tile.
If I understand the way the tiles are made, they are baked (sintered) with a Y shaped frame on the back that has 3 holes for the studs that are welded to the hull by robots.
So I asked myself why do it in 2 steps? Why not sinter the tile with a frame that already has 3 studs fixed to the frame, no holes needed, then have the robots weld the tile with studs to the hull?
To do that the studs on the tile need to be electrically wired to make the welding possible. Then as much of that wiring as possible could be pulled away (or left in place). I was thinking the frame would include the wires.
I have seen how studs are welded, but I don't know if that can be done while a stud is behind a tile.
If a tile is cracked it will have to be removed as they do now, but the studs have to also be cut off to make place for a new tile.
Just a thought that maybe others can improve...or debunk.
AIUI these tiles are designed to be removed from those mouting studs if they need to be replaced.
So I asked myself why do it in 2 steps? Why not sinter the tile with a frame that already has 3 studs fixed to the frame, no holes needed, then have the robots weld the tile with studs to the hull?
AIUI these tiles are designed to be removed from those mouting studs if they need to be replaced.
So I asked myself why do it in 2 steps? Why not sinter the tile with a frame that already has 3 studs fixed to the frame, no holes needed, then have the robots weld the tile with studs to the hull?
What you're suggesting would likely weld the tile to the stud, as well as the stud to the hull.
Coming up with a design that only welds the stud to the hull and leaves the actual attachment mechanism undamaged is likely to prove more trouble than any benefits to replacing the current system.
Stud welding in industry is highly automated. Each one taking a few seconds and often done at more than one at a time.
IIRC, we've seen a bot welding the pins but I don't think we saw in enough detail to know exactly what technique was being used - or did we?AIUI these tiles are designed to be removed from those mouting studs if they need to be replaced.
So I asked myself why do it in 2 steps? Why not sinter the tile with a frame that already has 3 studs fixed to the frame, no holes needed, then have the robots weld the tile with studs to the hull?
What you're suggesting would likely weld the tile to the stud, as well as the stud to the hull.
Coming up with a design that only welds the stud to the hull and leaves the actual attachment mechanism undamaged is likely to prove more trouble than any benefits to replacing the current system.
Stud welding in industry is highly automated. Each one taking a few seconds and often done at more than one at a time.
Have you ever looked at a welder? Even the smallest home hobby unit has cables as thick as a finger.AIUI these tiles are designed to be removed from those mouting studs if they need to be replaced.
So I asked myself why do it in 2 steps? Why not sinter the tile with a frame that already has 3 studs fixed to the frame, no holes needed, then have the robots weld the tile with studs to the hull?
What you're suggesting would likely weld the tile to the stud, as well as the stud to the hull.
Coming up with a design that only welds the stud to the hull and leaves the actual attachment mechanism undamaged is likely to prove more trouble than any benefits to replacing the current system.
Stud welding in industry is highly automated. Each one taking a few seconds and often done at more than one at a time.
The studs would not be welded to the tile, but be part of the frame just as the holes are now.
When it comes to removing tiles I have noted they drill holes, then use those to break the tile in pieces then they remove the frame that was holding the tile last. With the tiles I am thinking of it would only add one step - grind off 3 studs.
The system I am envisioning would also be automated but instead of just welding studs the robot arm would place the tile, with its 3 built in studs, in its exact position then run the current through the frame on the back which would weld the tips of the studs to the hull, then pick up the next tile and repeat.
What I am not sure about is if to weld any stud there is a minimum thickness of the electrical wire used for the welding? Would it be possible to use the metal of the frame itself as a section of such a wire?
This system would also make it easier to leave all tiling until the ship is fully stacked. Then the robot would run all over the ship in one go. It can be mounted on a frame that can move it vertically and horizontally. Rotating the ship would also help.
The point of doing the tiling last is there will be no need to glue tiles at the junctions between sections the way they must at present. That would leave gluing to the tip of the nose cone and parts of the flaps. Maybe also the perimeter of the tiling surface. (Tiles are glued between sections because there is no way the studs on one side will perfectly aligned with studs on an adjacent section.)
But it all depends on the welding of the studs when installing the tile. If that for some reason can't be done then my idea is dead in the water. The wire needed for the welding has to be narrow enough to fit between any two tiles without causing damage. An alternative is to have 3 holes on the surface of each tile that connects the wires needed to the built in studs. When they have been welded the wire would be removed as the robot arm moves off the tile. Those holes would not be much more than the gaps between tiles - maybe less. They could even be at a slight angle to reduce exposure on reentry. Robots are good at doing that kind of exact movements and accurate placement.
If SpaceX wants to produce a ship every 3 days doing tiles by hand the way they are installed today will be very hard in the long run.
Have you ever looked at a welder? Even the smallest home hobby unit has cables as thick as a finger.
Have you ever used a surface grinder? What you call "only one step" would be no more than an irritation on earth but on orbit or transit to mars this would be a major operation and a space suit devouring risk. Admittedly, a safer specialized grinder could be designed and a robot could do the work but there's no reason to think that SX needs to pivot to another design - yet.
Yes, the tiles and bayonet clips have been a problem. If you've been following this since the first test tiles were installed you'll know that shedding tiles is not as bad as it once was. They need to keep working the problem and refine the design. If they can't make it work they'll look in other directions.
Absolutely agree that the pin welding would best be done on the stacked ship. Conjecture: the current method is a SpaceX 'good enough' for current testing needs. I haven't been following closely but it appears that barrel fabrication easily outstrips stacking so they weld the pins while the barrels are waiting to stack. That'll change as the fabrication process matures.
Have you ever looked at a welder? Even the smallest home hobby unit has cables as thick as a finger.
Have you ever used a surface grinder? What you call "only one step" would be no more than an irritation on earth but on orbit or transit to mars this would be a major operation and a space suit devouring risk. Admittedly, a safer specialized grinder could be designed and a robot could do the work but there's no reason to think that SX needs to pivot to another design - yet.
Yes, the tiles and bayonet clips have been a problem. If you've been following this since the first test tiles were installed you'll know that shedding tiles is not as bad as it once was. They need to keep working the problem and refine the design. If they can't make it work they'll look in other directions.
I know that those welding wires are thick (I have done some DIY welding), that is why I am asking those who might know more than me. But don't forget that the gaps between tiles are a few mm (I can only compare the size of the gaps on photos to those of a tile).
My alternative is to use holes in the tiles that connect directly to the studs. Their small size would be of the same order as the gaps and could easily be tested in a lab to show if they would add to the risks.
You mention replacing tiles in space. I would counter that with the cases when workers have had to use crowbars and chisels to remove tiles. Doing that in space will be a challenge to say the least.
I know that the installation of tiles has improved a great deal and am pretty sure they will do fine. But what I was looking at was how to automate and simplify the process (and reduce the number of tiles cracked during installation). SpaceX's tile experts could I am sure find better modifications. This idea I had was just one way. One I think could be used and improved on - that's all. (To SpaceX: if you use it or a variant of it give a donation to some charity)
It might sound like a complicated method, but really is not, and the benefits of removing the need to glue half the glued tiles is not negligible either.
BTW, if the robots used today welded the studs after stacking the ship they would avoid glueing all those tiles at the section junctions. Anyone who has watched the tiling knows using glue takes at least 10 times longer and is pure hell to remove. (I would hate to see an astronaut try using solvents in space to remove the glue behind a tile)
A full flight to orbit would shake out a lot of issues.
They really need at least one launch and EDL attempt before they can have a clue on refinement or pivot to something different. Once they have a better idea of where they're going they'll refine the mounting process.
Your idea on welding cable holes in the tiles kicked off a thought. There has been talk of small holes to allow injection of hydrophobic chemicals. There are latches that are very robust that release easily when pressed by a thin stiff wire. This might be two birds with one stone.At the back end of the X33 programme the metal tiles were being mounted by (IIRC) 4 screws, 1 at each corner, with a superalloy cap backed by high temperature insulation. However at the very end of one of the reports there were notes about a better proposal. An adaptation of some kind of commercial tool. Very thin head that could slide between the tiles and squeeze some kind of spring that would allow the tile to come off very easily while being very light as well.
;) Don't worry, I am not fixating on my idea. Just wanted to throw it out there and see if others could make something of it. I just need convincing.A misconception. The holes will not close on heating. They will enlarge. This is any material. The mean space between molecules becomes greater over the entire object. All dimensions increase.
I admit that using the Y frame to assist in leading the current was not that great. The other one with the three holes is better. BTW, the holes would get almost closed during reentry due to tile expansion - they would also release some of the tension.
Can't the welds be tested by measuring conductivity and resistance once the pin is welded? How is it done at present? Is someone checking using X-ray every single stud? (I have never seen it done)
As to making the tile with the pins fixed when it leaves the oven, what would be different compared to the tile leaving it with the 3 holes (in the Y frame)? I am assuming the holes are made of some metal, just as the studs would.
The thermal blankets are needed to reduce vibrations, but they could also be to act as last resort if a tile is lost, I guess. They could be cut to the right size and made part of a tile's back side. Maybe slightly wider to avoid gaps. That would btw replace the need to add those blankets by hand, and having to push them over the studs, which in turn risks bending a stud here or there.
I will stop here. I think I have stated all the points I wanted to make.
Still not sure what this stuff is, but it held back two minutes of butane fury without getting warm on the far side.
The metalic film didn't last long, but the stuffing seemed kind of ablative.
;) Don't worry, I am not fixating on my idea. Just wanted to throw it out there and see if others could make something of it. I just need convincing.A misconception. The holes will not close on heating. They will enlarge. This is any material. The mean space between molecules becomes greater over the entire object. All dimensions increase.
I admit that using the Y frame to assist in leading the current was not that great. The other one with the three holes is better. BTW, the holes would get almost closed during reentry due to tile expansion - they would also release some of the tension.
Can't the welds be tested by measuring conductivity and resistance once the pin is welded? How is it done at present? Is someone checking using X-ray every single stud? (I have never seen it done)
As to making the tile with the pins fixed when it leaves the oven, what would be different compared to the tile leaving it with the 3 holes (in the Y frame)? I am assuming the holes are made of some metal, just as the studs would.
The thermal blankets are needed to reduce vibrations, but they could also be to act as last resort if a tile is lost, I guess. They could be cut to the right size and made part of a tile's back side. Maybe slightly wider to avoid gaps. That would btw replace the need to add those blankets by hand, and having to push them over the studs, which in turn risks bending a stud here or there.
I will stop here. I think I have stated all the points I wanted to make.
The current Y bracket, or at least the last one I remember seeing, has three slots for the clips, not holes. The tile can expand over the clips without binding and cracking. If not the Y bracket, some other mechanism is needed to allow for the expansion differences of tile and hull. Three clips without this would lead to failure, most probably of all the tiles.
I was also wondering about how they test clip welds. It may be that they did extensive testing to find the exact setting needed for a good weld and measure current draw during the weld process to point out anomalies. I'm old school enough that I always want to see my work product. Even dogs and cats do it. :D This, and every other test I can think of other than imaging of some sort becomes murky through two interfaces (pin to hull and pin to Y bracket).
The thermal blanket is a, well, thermal blanket. It is a backup. TBH, I don't know if there is anything solid on this or if it's NSF lore. AIUI, it also reduces scuffing from vibration as you point out, and it is (speculated? known?) that it puts a bit of springiness behind the tile to keep the pins mechanically loaded, which sorta overlaps on the vibration thing.
Think through the idea of a patchwork thermal blanket a bit larger than a tile. Lay down tile number 1. Assume the intended gap is 5mm. Assume the extra fringe of blanket is 10mm. Lay down tile number 2. Hmm. It overlaps the fringe of tile 1 but it's fringe can only lap on top of tile 1. Ah ha! We can modify the blanket to stay flush on three faces and extend out 10mm on three faces. We now have a tile that can only go on with only one specific orientation. Bummer. It just got more complicated.
Next, picture loosing one tile. Hmmm. The blanket is pinched under three tiles and being held in place but is flapping in the breeze around half its circumference. And why exactly is this a good thing?
To my knowledge, however imperfect, I know if no time a stud was bent while pushing the blanket over them. It looks to be roughly the texture of a dense fiberglass insulation batt.
Really, honest to mergatroid, cross my heart and pinky promise, welding the pins as you suggest would make it harder, more expensive, and more prone to breakage. Did I mention it wouldn't work?
Are you sure you aren't in love with this idea? I know a good counselor...
In a more serious vein, you're new here. I strongly suggest starting at the beginning of this thread and at least skimming through to see what the discussion has covered. It's a lot to digest but if you're here because you're curious about the topic, you will come away from your reading with a reasonable education on the general issues and the specifics of what SX has has done to address these issues. And you would be doing the rest of us a curtesy by not hammering on something that has already been hammered to death. You haven't done that last. You've hit on something new. Bravo!
At the back end of the X33 programme the metal tiles were being mounted by (IIRC) 4 screws, 1 at each corner, with a superalloy cap backed by high temperature insulation. However at the very end of one of the reports there were notes about a better proposal. An adaptation of some kind of commercial tool. Very thin head that could slide between the tiles and squeeze some kind of spring that would allow the tile to come off very easily while being very light as well.Your memory was exactly on point both on the mounting description and the proposal for improved versions. This is the report (https://www.researchgate.net/publication/255921834_Development_of_metallic_thermal_protection_systems_for_the_reusable_launch_vehicle) you were thinking of.
Unfortunately that's all I can remember about it. :( . IIRC the actual TPS contractor was Rohr, who are (or were) quite big in building parts of ships.
The most innovative and effective modification, however, is the use of quick release fasteners. The fastener uses a simple wire clip that snaps into a groove of a stud attached to the structure. The fastener is released by sliding a special “scissors-like” tool into the gap between panels and squeezing the ends of the wire together. A thin slot or notch in the gap cover allows the tool to be inserted into the gap. When the panels heat up and expand the gaps begin to close and the slots slide over the adjacent panels. This fastener concept has no loose parts, is quick and simple to operate, and eliminates the costly and troublesome fastener access tubes and covers.
Still not sure what this stuff is, but it held back two minutes of butane fury without getting warm on the far side.
The metalic film didn't last long, but the stuffing seemed kind of ablative.
Just fluffy. There's some extremely fine powder coming out when it's abused. I decided to keep it in a plastic bag and take precautions when I handle or torture it.Still not sure what this stuff is, but it held back two minutes of butane fury without getting warm on the far side.
The metalic film didn't last long, but the stuffing seemed kind of ablative.
Which side is the back side here? Does the other side have the same metallic film or is it just fluffy?
Just fluffy. There's some extremely fine powder coming out when it's abused. I decided to keep it in a plastic bag and take precautions when I handle or torture it.Still not sure what this stuff is, but it held back two minutes of butane fury without getting warm on the far side.
The metalic film didn't last long, but the stuffing seemed kind of ablative.
Which side is the back side here? Does the other side have the same metallic film or is it just fluffy?
It's probably just coincidence that I developed the ability to shoot flames from my eyes after I touched it.
Any sign that it was "needled" into a blanket or just straight mat?Straight mat.
John
Still not sure what this stuff is, but it held back two minutes of butane fury without getting warm on the far side.A quick check says butane combustion can hit 1430c/2606F. Not bad as a 1 shot emergancy tactic to get back to the surface.
The metalic film didn't last long, but the stuffing seemed kind of ablative.
Still not sure what this stuff is, but it held back two minutes of butane fury without getting warm on the far side.
The metalic film didn't last long, but the stuffing seemed kind of ablative.
Still not sure what this stuff is, but it held back two minutes of butane fury without getting warm on the far side.
The metalic film didn't last long, but the stuffing seemed kind of ablative.
I'm surprised, it doesn't act like Saffil or Superwool:
https://www.youtube.com/watch?v=m9gjcnc6IAw
Yes, Superwool Plus has a classification temperature of 1200°C and the HT version is 1300°C so it might be able to just about handle the melting point of the steel - but the torch is quite a bit hotter than that. He has to move it quickly as the felt is made of thin fibres and the bulk density of the steel is 50x - 100x larger.
Yes, Superwool Plus has a classification temperature of 1200°C and the HT version is 1300°C so it might be able to just about handle the melting point of the steel - but the torch is quite a bit hotter than that. He has to move it quickly as the felt is made of thin fibres and the bulk density of the steel is 50x - 100x larger.IIRC Saffill is rated up to 1600c. Unfortunately no one seems to be able to weave it (or maybe no one has ever tried?) Normally used as a felt or batting.
A couple of fin fairings and a piece of something that I'm not sure about sitting out back.
That would likely be how the rails are inserted after sintering - rather than needing the rails to survive sintering furnace temperatures without deformation inside the tile preforms. The tiles are quite friable, so little mechanical force would be needed to push them in without any prior milling of channels.
How to get through the Borosilicate glass coating without fracturing it would be the tricky bit. Could be a hairline gap masked off during the glass application process, could be a milled slot in just the glass layer to allow insertion, or very careful insertion right through the unmodified glass layer to avoid spreading cracks.
One arm at a time, meeting in the centre. The frames are what are retained by the clip pins, so tiles that have fractured are easier to remove 'around' the mounted frame, which will hold to the clip pins all on its own. Whole tiles being removed have holes drilled to access the pins, which are than released from the frame internally and the whole tile assembly removed.That would likely be how the rails are inserted after sintering - rather than needing the rails to survive sintering furnace temperatures without deformation inside the tile preforms. The tiles are quite friable, so little mechanical force would be needed to push them in without any prior milling of channels.
How to get through the Borosilicate glass coating without fracturing it would be the tricky bit. Could be a hairline gap masked off during the glass application process, could be a milled slot in just the glass layer to allow insertion, or very careful insertion right through the unmodified glass layer to avoid spreading cracks.
After watching tiles being cracked and removed, the frames many times are the last to be romoved and are Y-shaped. Can't see how you can insert a Y-shaped frame after sintering.
The frames use to be shorter and completely buried. They were where most of the ones I saw failed.A couple of fin fairings and a piece of something that I'm not sure about sitting out back.
It looks like the frames of the tiles stick out on the sides.
As for the little bit of exposed metal, I doubt that it matters considering where it is and that it's edge on.
Regarding the visible mounting support in those tiles; my money is on there being a standard sintered tile part that's probably the exact size of the main hex tiles. That component is either coated and baked to make a standard tile or it's machined to a smaller size or different shape for the other tiles as a secondary process before being coated and baked.From the FDEP report on the tile manufacturing facility: The tile billets are moulded, then sintered, then cut in half face-to-face or back-to-back (i.e. billets are double-thickness), then trimmed to size, then the RCG coating is applied (with further heating).
These particular tiles are small enough that the metal was cut exposed on the edges and for whatever reason the glass coating doesn't adhere to the metal well.
From a manufacturability perspective having a single high production process that makes all the tile blanks and then customizing just a few makes the most sense.
As for the little bit of exposed metal, I doubt that it matters considering where it is and that it's edge on.
A couple of fin fairings and a piece of something that I'm not sure about sitting out back.
SpaceX switched from red RTV to white some months ago (either a switch in formulation, or just a big enough order they could request a different pigment). They've also gotten better at applying it without as much smear.A couple of fin fairings and a piece of something that I'm not sure about sitting out back.
Great photos, Nomadd! the fin fairing tiles seem to be of a completely different design from the main body tiles? And no red adhesive is to be seen. Can someone sum up what they are and how are they attached?
The Air Force Research Laboratory awarded SpaceX an $8.5 million contract to investigate advanced materials and manufacturing techniques for heat shields that protect hypersonic vehicles in flight.
Heat protection is a critical technology to shield hypersonic vehicles from the intense heat experienced when flying at more than five times the speed of sound.
The contract was from the AFRL Materials and Manufacturing Directorate for a project called “multipurpose thermal protection systems for hypersonics.”
Notice how w each iteration we see a higher % of tiles that are a custom fit to their unique location. Was probably inevitable
I know they wanted to simplify things but I’ve got a feeling the tile layout is basically gonna look like the shuttle when it’s done #starship #SpaceX
Having worked on and around Space shuttle tiles, I can tell you there’s a thing known as “step and gap” (important for laminar flow and heat transfer), and the tiles in this picture don’t yet demonstrate mastery of that topic (to say the least).
Isn’t Starships’s reentry AOA around 60 deg (2X the Shuttle)? Are step inconsistencies as important at those extreme alphas? I was told Soviet fighters had much worse surface tolerances than American fighters because they didn’t see the need to over design for the mission.
I don’t know. I agree that their requirements are likely a lot different.
Heat flux ratio in the gap decreases as Mach number increases, because the boundary layer tends to be thinner and air flowing into the gap decreases as Mach number increases.
The heat flux ratio is basically U-shaped distribution along the surface of a gap.
Thus, setting chamfer in the windward can reduce the gap effect coefficient, which is a valid method for reducing the gap local aerodynamic heating environment.
https://twitter.com/ringwatchers/status/1613691353472405504
Open question: would each and every tile carry an RFID chip (or similar) to help identify problems during the upcoming orbital mission? Could be helpful to see if/when and where tiles come off during all phases of the flight.There might be RFID tags that can survive the temperatures involved but I think it would require quite a bit of work. It would also be tricky to read them as they are mounted on a curved metal surface.
Open question: would each and every tile carry an RFID chip (or similar) to help identify problems during the upcoming orbital mission? Could be helpful to see if/when and where tiles come off during all phases of the flight.There might be RFID tags that can survive the temperatures involved but I think it would require quite a bit of work. It would also be tricky to read them as they are mounted on a curved metal surface.
Other options would be a wire/fiber optic mesh behind the insulation as well as cameras inside the tanks or mounted on the flaps.
I think the only TPS related sensors we have seen are the handfull of likely temperature sensors mounted on the ventral side of the nose cone/payload bay.
One thing I could see on the first flight is a simple free flying or tethered 360 camera deployed from the aft skirt after SECO. There has been talk of something like that on Polaris Dawn and it should require a minimum of effort.
Open question: would each and every tile carry an RFID chip (or similar) to help identify problems during the upcoming orbital mission? Could be helpful to see if/when and where tiles come off during all phases of the flight.I think much can be learned using IR cameras looking at the inside of the skin.
Open question: would each and every tile carry an RFID chip (or similar) to help identify problems during the upcoming orbital mission? Could be helpful to see if/when and where tiles come off during all phases of the flight.I do not know of an RF system that could operate "over the air" near a big stainless steel tank. There might conceivably be a way to use some sort of skin effect to transmit along the surface of the tank. A network of thousands of these would be a challenge. the bigger question is "why?". Addition of the tranceiver and sensors to the tile would change its physical characteristics, probably making it more delicate and less insulating, not to mention being a manufacturing nightmare.
I've brought this up in the past and gotten no traction. Acustic sensing. It probably wouldn't work when the main engines are firing but otherwise a network of mic's and some serious DSP's behind them could conceivably localize to individual tiles and with a good signal library, pin down what happened.Open question: would each and every tile carry an RFID chip (or similar) to help identify problems during the upcoming orbital mission? Could be helpful to see if/when and where tiles come off during all phases of the flight.There might be RFID tags that can survive the temperatures involved but I think it would require quite a bit of work. It would also be tricky to read them as they are mounted on a curved metal surface.
Other options would be a wire/fiber optic mesh behind the insulation as well as cameras inside the tanks or mounted on the flaps.
I think the only TPS related sensors we have seen are the handfull of likely temperature sensors mounted on the ventral side of the nose cone/payload bay.
One thing I could see on the first flight is a simple free flying or tethered 360 camera deployed from the aft skirt after SECO. There has been talk of something like that on Polaris Dawn and it should require a minimum of effort.
I mean.. it would be significantly difficult to read RFID chips in flight, which is apparently where the question was going, talking about detecting *when* tiles fall off, meaning having a constant connection to each tile. That's just insane. You would need a reader probably under the tiles or inside the barrel every couple inches.
At most I could imagine a 1-wire detection circuit per tile but even that is way overkill for a reusable starship.
Tile detachment detection with that kind of granularity would primarily be for the initial test flights. Hopefully wouldn't be needed on a mature launch system.
I've brought this up in the past and gotten no traction. Acustic sensing. It probably wouldn't work when the main engines are firing but otherwise a network of mic's and some serious DSP's behind them could conceivably localize to individual tiles and with a good signal library, pin down what happened.Open question: would each and every tile carry an RFID chip... SnipThere might be RFID tags that can survive the temperatures... Snip
One thing I could see on the first flight is a simple free flying or tethered 360 camera deployed from the aft skirt after SECO....
Snip
We've all heard how that hull rings when beaten by a hammer. It transmits sounds quite well. Every material has a characteristic acoustic signature. I doubt there is anything on the starship that would sound like a cracking tile except... a cracking tile. There is a lot of other noise but that's what DSP's are for. They pull small signal out of big noise.
Cracking is only one failure mode and even it has subcategories. How fine a discrimination is possible is an open question but at a gross level of tagging failures, I think it would work.
Any sonar operators out there? :D
Y'all are making a pretty big assumption that one of these very light weight, super insulated tiles with a veeeery thin glass layer, and is as isolated from the ship as possible (in most places) with a layer of fluffy insulation that probably works as a pretty good acoustic insulator as well, will actually make much sound at all when it cracks.Maybe not the sound of a tile breaking, but the sound of the metal insert within a tile rattling around on or tearing off the metal (and welded directly to the skin) mounting pegs will. A cracked tile that remain in place and otherwise in large chunks is likely still mostly effective as TPS (once the vehicle decelerates enough for airflow to slow enough for it to fall off, its done its job) but a tile that fails so catastrophically that it affects TPS effectiveness is of more interest for that sort of vehicle-did-not-survive telemetry.
I'd be very surprised if the breaking sound signature was even within 20 dB of the ambient background noise.
With an array of mic's it should be possible to pin down the physical source of transients. Combined with high speed video/LiDAR would that be enough to start building a library?I've brought this up in the past and gotten no traction. Acustic sensing. It probably wouldn't work when the main engines are firing but otherwise a network of mic's and some serious DSP's behind them could conceivably localize to individual tiles and with a good signal library, pin down what happened.Open question: would each and every tile carry an RFID chip... SnipThere might be RFID tags that can survive the temperatures... Snip
One thing I could see on the first flight is a simple free flying or tethered 360 camera deployed from the aft skirt after SECO....
Snip
We've all heard how that hull rings when beaten by a hammer. It transmits sounds quite well. Every material has a characteristic acoustic signature. I doubt there is anything on the starship that would sound like a cracking tile except... a cracking tile. There is a lot of other noise but that's what DSP's are for. They pull small signal out of big noise.
Cracking is only one failure mode and even it has subcategories. How fine a discrimination is possible is an open question but at a gross level of tagging failures, I think it would work.
Any sonar operators out there? :D
Phill,
Not a sonar op, but a live sound engineer.
The DSP will need to know what tiles cracking while the vehicle is at hypersonic velocity sounds like. Which would require a full size vehicle. Put into a supersonic wind tunnel to get the data the DSP will require. They might get away with putting the top 1/3 of a SS. Nosecone flaps & a straight ring or 2 under it. With the bottom wielded shut with a circular plate.
And do the same with engine section and lower flaps with the top sealed, the engine skirt open.
The problem is I have never heard of a supersonic wind tunnel big enough. And using a 1/10 scale model would sound different. Maybe they could extrapolate the tonal differences. I don't know.
eriblo, I like the idea of deploying a cubesat or two with cameras.
Ned
Not necessary to know the actual sound, but a calibration session would be noted applying some test sound (ideally an impulse. A hammer would not be unreasonable) in known locations to allow the time difference and reflections recorded by the transducers to be mapped to physical locations. This is a hobby-level operation, many people have DIYed touch-sensitive objects by applying contact mics to objects and calibrating desired interaction areas. It's also something SpaceX themselves have done, using the accelerometers on board CRS-7 as contact mics in order to localise the strut failure.I think you just answered my questions. Thank you.
Acoustic monitoring would give you a map of tile events, through it would not provide information of why a given tile failed without more localised instrumentation (e.g. temperature probes, strain gauges on tile pins, etc). Remote sensing from the test range equipment would only provide exterior temperatures (which can be mapped to flow discontinuities too) but not temperatures of components beneath the surface. Though both would give a map of likely tile loss areas in order to more accurately target future instrumentation installations.
Y'all are making a pretty big assumption that one of these very light weight, super insulated tiles with a veeeery thin glass layer, and is as isolated from the ship as possible (in most places) with a layer of fluffy insulation that probably works as a pretty good acoustic insulator as well, will actually make much sound at all when it cracks.My musicians ear tells me that cracking ceramic is a sharp transient with little or no ring. Not much area under that waveform but quite a bit of amplitude.
I'd be very surprised if the breaking sound signature was even within 20 dB of the ambient background noise.
Nice that SpaceX’s mom wrote their name on it.
Edit: it seems like the metal insert is steel, but not a stainless alloy?
OMG very nice.
So how u can sinter with metal inserts? Got no idea how they do that...
Seems to me texture implies not machining is needed. Also that would be preferred methodology to ease mass production.
By someone who would know or who is speculating? This would seem like the absolutely worst way to do this from what we know about the tiles..OMG very nice.I have been told the brackets are pushed inside after the tile has been sintered. On some images you can see the edge of the bracket sticking a mm or so out of the side. 3 brackets per tile.
So how u can sinter with metal inserts? Got no idea how they do that...
Seems to me texture implies not machining is needed. Also that would be preferred methodology to ease mass production.
By someone who would know or who is speculating? This would seem like the absolutely worst way to do this from what we know about the tiles..OMG very nice.I have been told the brackets are pushed inside after the tile has been sintered. On some images you can see the edge of the bracket sticking a mm or so out of the side. 3 brackets per tile.
So how u can sinter with metal inserts? Got no idea how they do that...
Seems to me texture implies not machining is needed. Also that would be preferred methodology to ease mass production.
It does look like there's a path through the material where the bracket was pushed in.OMG very nice.
So how u can sinter with metal inserts? Got no idea how they do that...
Seems to me texture implies not machining is needed. Also that would be preferred methodology to ease mass production.
I have been told the brackets are pushed inside after the tile has been sintered. On some images you can see the edge of the bracket sticking a mm or so out of the side. 3 brackets per tile.
Is there a visible difference between the original and fracture surfaces on the tile? What does the tile "channel" surface look like? Are the brackets free to move or are they rigidity attached to the tile? Can a metal object like a nail be pushed into the tile without excessive fracturing?It does look like there's a path through the material where the bracket was pushed in.OMG very nice.I have been told the brackets are pushed inside after the tile has been sintered. On some images you can see the edge of the bracket sticking a mm or so out of the side. 3 brackets per tile.
So how u can sinter with metal inserts? Got no idea how they do that...
Seems to me texture implies not machining is needed. Also that would be preferred methodology to ease mass production.
Paid the old homestead a visit today and cleaned up the mudflats some.
Paid the old homestead a visit today and cleaned up the mudflats some.
Would love to see the tile from a couple of other angles, Nomadd, I have a hard time understanding the geometry of it.
Nice find!
So, the hollowed-out backsides are what permit the brackets to slide in?No, they just save mass. And save on Silica, which reduces cost (and the reduced overall thickness may also speed up sintering time, which will also save cost).
Paid the old homestead a visit today and cleaned up the mudflats some.
Would love to see the tile from a couple of other angles, Nomadd, I have a hard time understanding the geometry of it.
Nice find!
Nomadd posted pictures already. See https://forum.nasaspaceflight.com/index.php?topic=50748.3260
Paid the old homestead a visit today and cleaned up the mudflats some.
Would love to see the tile from a couple of other angles, Nomadd, I have a hard time understanding the geometry of it.
Nice find!
Nomadd posted pictures already. See https://forum.nasaspaceflight.com/index.php?topic=50748.3260
I didn't find any more pics of that tile in your link.
Paid the old homestead a visit today and cleaned up the mudflats some.
Would love to see the tile from a couple of other angles, Nomadd, I have a hard time understanding the geometry of it.
Nice find!
Am I missing something? The tiles are sintered? This is the first I've heard of this.Sintering involves pressure and/or heat. Materials like these are sintered at high temperatures at atmospheric pressure just like pottery.
Sintering is a pressure process. Even if the tile material were sintered I don't see how the glaze could be sintered on.
Can somebody unconfuse me?
Never heard the term used that way. For ceramics, the familiar term is baking or firing.Am I missing something? The tiles are sintered? This is the first I've heard of this.Sintering involves pressure and/or heat. Materials like these are sintered at high temperatures at atmospheric pressure just like pottery.
Sintering is a pressure process. Even if the tile material were sintered I don't see how the glaze could be sintered on.
Can somebody unconfuse me?
Sintering using mechanical pressure is unsuitable for the the tiles, as pre-crushing the porous tile renders it ineffective in terms of its desired insulating properties. There are also plenty of ceramics and metallics that are vacuum sintered - e.g. tungsten carbide tooling inserts - or sintered at atmospheric pressure (though not always in regular air).Never heard the term used that way. For ceramics, the familiar term is baking or firing.Am I missing something? The tiles are sintered? This is the first I've heard of this.Sintering involves pressure and/or heat. Materials like these are sintered at high temperatures at atmospheric pressure just like pottery.
Sintering is a pressure process. Even if the tile material were sintered I don't see how the glaze could be sintered on.
Can somebody unconfuse me?
Broadly speaking, my familiarity with sintering involves pressure which generally results in heat but heat can be added. Individual particles fuse at the point of contact without general melting, creating a matrix with open spaces throughout.
Hmmm, that last does describe the tile material, so I'll just shut up and grok. Live and learn.
BTW, the glaze would not be an open matrix. In the pottery world, goop with glass in it is painted on and fired high enough that the glass softens and runs together into a solid layer. Porcelain can be thought of as all glaze with no substrate.
Does the plastic mesh have any function other than keeping the thermal blankets from getting loose before the tiles are added?
Why don't they cover the mount in the heat shield material on the ship?
My first guess is that the thrusters are a lot hotter than the re entry temps?
And if so then I just answered my own question?
Why don't they cover the mount in the heat shield material on the ship?
My first guess is that the thrusters are a lot hotter than the re entry temps?
And if so then I just answered my own question?
I think it might be more about accoustic vibrations shattering the tiles
Just for fun:
Air density at 100km above surface: ~6x10-7 kg/m3
Entry velocity: ~8km/s
1s of entry flight impacts an 8km long column of air
1 m2 of entering vehicle will meet 8000 cubic metres of air during 1s of entry
8000 m3 of air will mass ~4.8g
Entry plasma mass flow: ~0.005kg/s
Booster aft end area: ~18m2
Raptor propellant consumption: ~650kg/s each
33 raptors per booster: 21450 kg/s
Mass flow rate per square metre of booster: ~1200kg/s
About a factor of 2.4 million difference. A gentle hypersonic plasma tickling vs. a meaty combustion-product pummelling.
(Yes, peak flow would be later during entry, I'm not breaking out the calculator during my lunch break).
Just for fun:Earth scale height is about 8.5km (meaning each change in 8.5km altitude results in a change in density by about a factor of e, 2.718…)
Air density at 100km above surface: ~6x10-7 kg/m3
Entry velocity: ~8km/s
1s of entry flight impacts an 8km long column of air
1 m2 of entering vehicle will meet 8000 cubic metres of air during 1s of entry
8000 m3 of air will mass ~4.8g
Entry plasma mass flow: ~0.005kg/s
Booster aft end area: ~18m2
Raptor propellant consumption: ~650kg/s each
33 raptors per booster: 21450 kg/s
Mass flow rate per square metre of booster: ~1200kg/s
About a factor of 2.4 million difference. A gentle hypersonic plasma tickling vs. a meaty combustion-product pummelling.
(Yes, peak flow would be later during entry, I'm not breaking out the calculator during my lunch break).
Ever since I realized this system would have a huge re-entry footprint (Ahhh, the 12m BFR!) I have been wondering if the metallic thermal-protection concept that was intended for X-33/VentureStar might be suitable for use on Starship?The issue with metal tiles is the lower service temperature compared with ceramic fiber tiles. For example niobium can tolerate up to 1300C and a niobium+hafnium+titanium alloy up to 1480C but actual service temperatures for repeated re-entries are likely 300C below these numbers. Coated alumina+silica ceramic tiles can work up to 1250C on a repeated basis and show less erosion from oxygen plasma.
One of the key benefits of the "hot metal" heat shield was that it was explicitly designed to be robust, intended to survive minor debris strikes that would typically damage tiles, and even work in situations involving small MMOD hits.
Being that it forms a second layer that would vent to vacuum, that is not in continual contact with the primary structure of the vehicle, it was also intended to serve as a moderately good sun shield layer to help with storing cryogens on the vehicle.
A variant designed specifically for Starship with all those features, might be worth the weight penalty - which I understand wasn't actually that bad.
Ross.
Ever since I realized this system would have a huge re-entry footprint (Ahhh, the 12m BFR!) I have been wondering if the metallic thermal-protection concept that was intended for X-33/VentureStar might be suitable for use on Starship?The issue with metal tiles is the lower service temperature compared with ceramic fiber tiles. For example niobium can tolerate up to 1300C and a niobium+hafnium+titanium alloy up to 1480C but actual service temperatures for repeated re-entries are likely 300C below these numbers. Coated alumina+silica ceramic tiles can work up to 1250C on a repeated basis and show less erosion from oxygen plasma.
One of the key benefits of the "hot metal" heat shield was that it was explicitly designed to be robust, intended to survive minor debris strikes that would typically damage tiles, and even work in situations involving small MMOD hits.
Being that it forms a second layer that would vent to vacuum, that is not in continual contact with the primary structure of the vehicle, it was also intended to serve as a moderately good sun shield layer to help with storing cryogens on the vehicle.
A variant designed specifically for Starship with all those features, might be worth the weight penalty - which I understand wasn't actually that bad.
Ross.
The relatively high expansion coefficient also requires the tiles to be overlapped at the edges rather than butted together with gap fillers. In order to use metal tiles on Starship the ballistic coefficient would need to be lowered likely using oversized chines aka wings. This is possibly the source of Elon's cryptic comment a few years ago that they were looking at Dragon wings for Starship.
Ever since I realized this system would have a huge re-entry footprint (Ahhh, the 12m BFR!) I have been wondering if the metallic thermal-protection concept that was intended for X-33/VentureStar might be suitable for use on Starship?Completely agree, Ross. And I've tried to convince SpaceX folk to consider this approach, including trying to hook them up with the X-33 heatshield developers.
One of the key benefits of the "hot metal" heat shield was that it was explicitly designed to be robust, intended to survive minor debris strikes that would typically damage tiles, and even work in situations involving small MMOD hits.
Being that it forms a second layer that would vent to vacuum, that is not in continual contact with the primary structure of the vehicle, it was also intended to serve as a moderately good sun shield layer to help with storing cryogens on the vehicle.
A variant designed specifically for Starship with all those features, might be worth the weight penalty - which I understand wasn't actually that bad.
Ross.
Ever since I realized this system would have a huge re-entry footprint (Ahhh, the 12m BFR!) I have been wondering if the metallic thermal-protection concept that was intended for X-33/VentureStar might be suitable for use on Starship?The issue with metal tiles is the lower service temperature compared with ceramic fiber tiles. For example niobium can tolerate up to 1300C and a niobium+hafnium+titanium alloy up to 1480C but actual service temperatures for repeated re-entries are likely 300C below these numbers. Coated alumina+silica ceramic tiles can work up to 1250C on a repeated basis and show less erosion from oxygen plasma.
One of the key benefits of the "hot metal" heat shield was that it was explicitly designed to be robust, intended to survive minor debris strikes that would typically damage tiles, and even work in situations involving small MMOD hits.
Being that it forms a second layer that would vent to vacuum, that is not in continual contact with the primary structure of the vehicle, it was also intended to serve as a moderately good sun shield layer to help with storing cryogens on the vehicle.
A variant designed specifically for Starship with all those features, might be worth the weight penalty - which I understand wasn't actually that bad.
Ross.
The relatively high expansion coefficient also requires the tiles to be overlapped at the edges rather than butted together with gap fillers. In order to use metal tiles on Starship the ballistic coefficient would need to be lowered likely using oversized chines aka wings. This is possibly the source of Elon's cryptic comment a few years ago that they were looking at Dragon wings for Starship.
My concern is that a ceramic TPS Starship will *ALWAYS* be vulnerable to damage. We learned that pretty convincingly on Shuttle. To my mind that screams a critical accident becomes a "when", not an "if".
Ross.
There seems to be a widespread belief that Starship has a low ballistic coefficient. I guess it is based on the large and fluffy appearance? ::)
Shuttle orbiter: ~350 m2 projected, reentry mass 85 t - 105 t.
Perpendicular ballistic coefficient:
240 kg/m2 - 300 kg/m2
At 40° pitch:
380 kg/m2 - 470 kg/m2
Starship: ~580 m2 projected (flaps akimbo), reentry mass 150 t - 300 t.
Perpendicular ballistic coefficient:
260 kg/m2 - 520 kg/m2
At 70° pitch:
280 kg/m2 - 550 kg/m2
The reference area for Starship will actually be significantly smaller as the flaps will have some dihedral and a cylindrical body has roughly half the drag of a flat bottomed one.
While many reentries will be empty and relatively light the heat shield will be designed for the heaviest case.
Projected as in the shadow cast on a perpendicular surface. I.e. 9 m * 50 m minus nose taper plus flaps. Did a quick and dirty outline trace on Rafael's SNx drawing.There seems to be a widespread belief that Starship has a low ballistic coefficient. I guess it is based on the large and fluffy appearance? ::)
Shuttle orbiter: ~350 m2 projected, reentry mass 85 t - 105 t.
Perpendicular ballistic coefficient:
240 kg/m2 - 300 kg/m2
At 40° pitch:
380 kg/m2 - 470 kg/m2
Starship: ~580 m2 projected (flaps akimbo), reentry mass 150 t - 300 t.
Perpendicular ballistic coefficient:
260 kg/m2 - 520 kg/m2
At 70° pitch:
280 kg/m2 - 550 kg/m2
The reference area for Starship will actually be significantly smaller as the flaps will have some dihedral and a cylindrical body has roughly half the drag of a flat bottomed one.
While many reentries will be empty and relatively light the heat shield will be designed for the heaviest case.
How did you get 580m projected?
4.5m * pi * 50m = 706 m2
Which doesn't include flaps
I think Starship might be on the heavier side at first, but operationally could be 85 tonnes empty eventually. 300t is too high. Not sure if it’ll ever do that much.
I used 120 t dry + 30 t landing propellant and residuals + 150 t payload.I think Starship might be on the heavier side at first, but operationally could be 85 tonnes empty eventually. 300t is too high. Not sure if it’ll ever do that much.
with 100t return payload?
Again, I don’t think they’ll be doing a 300t entry from orbit (at least not without some aero upgrades). Either the returned payload will be small or they’ll make big strides on reducing dry mass of the stage (and landing propellant) or both. They hope to get stage dry mass down to 85 tonnes, may need only like 5-10 tons of propellant for terminal landing, and the payload may only be about 60 tons when returning from orbit, so could be just 150 tonnes.Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...
…on Mars.Again, I don’t think they’ll be doing a 300t entry from orbit (at least not without some aero upgrades). Either the returned payload will be small or they’ll make big strides on reducing dry mass of the stage (and landing propellant) or both. They hope to get stage dry mass down to 85 tonnes, may need only like 5-10 tons of propellant for terminal landing, and the payload may only be about 60 tons when returning from orbit, so could be just 150 tonnes.Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...
Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...There is a max launch payload, a max landing payload for Earth, and max landing payloads for Luna and Mars. They are not all the same. If you are designing to be able to land on Earth the same max payload you launch, then you are designing in a reduced max launch payload.
Obviously it does, for the very reason this discussion started (easier on the heatshield design). In fact, it’s not uncommon for aircraft to have different take-off max weight and landing max weight. They add a fuel dump. (Shuttle, in fact, was going to have that for Centaur missions before Challenger blew up and changed the risk profile for flights with crew, which was of course all Shuttle flights.)Again, I don’t think they’ll be doing a 300t entry from orbit (at least not without some aero upgrades). Either the returned payload will be small or they’ll make big strides on reducing dry mass of the stage (and landing propellant) or both. They hope to get stage dry mass down to 85 tonnes, may need only like 5-10 tons of propellant for terminal landing, and the payload may only be about 60 tons when returning from orbit, so could be just 150 tonnes.Does not make much sense to design a reusable vehicle that can not land with its maximum payload. …
They also need a solution that can work for Mars return reentry.Ever since I realized this system would have a huge re-entry footprint (Ahhh, the 12m BFR!) I have been wondering if the metallic thermal-protection concept that was intended for X-33/VentureStar might be suitable for use on Starship?The issue with metal tiles is the lower service temperature compared with ceramic fiber tiles. For example niobium can tolerate up to 1300C and a niobium+hafnium+titanium alloy up to 1480C but actual service temperatures for repeated re-entries are likely 300C below these numbers. Coated alumina+silica ceramic tiles can work up to 1250C on a repeated basis and show less erosion from oxygen plasma.
One of the key benefits of the "hot metal" heat shield was that it was explicitly designed to be robust, intended to survive minor debris strikes that would typically damage tiles, and even work in situations involving small MMOD hits.
Being that it forms a second layer that would vent to vacuum, that is not in continual contact with the primary structure of the vehicle, it was also intended to serve as a moderately good sun shield layer to help with storing cryogens on the vehicle.
A variant designed specifically for Starship with all those features, might be worth the weight penalty - which I understand wasn't actually that bad.
Ross.
The relatively high expansion coefficient also requires the tiles to be overlapped at the edges rather than butted together with gap fillers. In order to use metal tiles on Starship the ballistic coefficient would need to be lowered likely using oversized chines aka wings. This is possibly the source of Elon's cryptic comment a few years ago that they were looking at Dragon wings for Starship.
Dragon wings for Starship
As Nomadd mentions a lower maximum down mass means significant higher risk of loss of payload and vehicle for late aborts or any failure that prevents payload deployment. Remember that Starship will have a significant fraction of max LEO payload launches.…on Mars.Again, I don’t think they’ll be doing a 300t entry from orbit (at least not without some aero upgrades). Either the returned payload will be small or they’ll make big strides on reducing dry mass of the stage (and landing propellant) or both. They hope to get stage dry mass down to 85 tonnes, may need only like 5-10 tons of propellant for terminal landing, and the payload may only be about 60 tons when returning from orbit, so could be just 150 tonnes.Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...
The impression I’ve gotten from Robotbeat, is this has been a discussion for returning to Earth. In the near term, what use case is there to land with the maximum payload on Earth?
I am not sure I follow your logic. Maximum launch payload is determined by launch vehicle performance. Maximum landed payload on Earth is determined by heat shield performance (among other things).Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...There is a max launch payload, a max landing payload for Earth, and max landing payloads for Luna and Mars. They are not all the same. If you are designing to be able to land on Earth the same max payload you launch, then you are designing in a reduced max launch payload.
I'll concede that Starship does not have to be able to land with maximum (reusable) payload but I think that SpaceX has higher ambitions.Obviously it does, for the very reason this discussion started (easier on the heatshield design). In fact, it’s not uncommon for aircraft to have different take-off max weight and landing max weight. They add a fuel dump. (Shuttle, in fact, was going to have that for Centaur missions before Challenger blew up and changed the risk profile for flights with crew, which was of course all Shuttle flights.)Again, I don’t think they’ll be doing a 300t entry from orbit (at least not without some aero upgrades). Either the returned payload will be small or they’ll make big strides on reducing dry mass of the stage (and landing propellant) or both. They hope to get stage dry mass down to 85 tonnes, may need only like 5-10 tons of propellant for terminal landing, and the payload may only be about 60 tons when returning from orbit, so could be just 150 tonnes.Does not make much sense to design a reusable vehicle that can not land with its maximum payload. …
I doubt I can find the source anymore, but I've heard 150t up and 50t down as the cargo specs.See if you can find a better one than the often misquoted 2017 presentation which is "Typical
Regarding the aircraft analogy - they are certified to land at any weight they are allowed to take off at, it might just be at a lower vertical speed. This is not the case for Starship as it has a maximum take off weight of ~1500 t.
Here you say that maximum launch payload is determined by launch vehicle performance. But above you imply that the maximum launch payload should be determined by the weight that can be landed on Earth. Which is it?I am not sure I follow your logic. Maximum launch payload is determined by launch vehicle performance. Maximum landed payload on Earth is determined by heat shield performance (among other things.)Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...There is a max launch payload, a max landing payload for Earth, and max landing payloads for Luna and Mars. They are not all the same. If you are designing to be able to land on Earth the same max payload you launch, then you are designing in a reduced max launch payload.
That’s inserting quite a lot of unwritten words into that slide.You are correct, I checked with the presentation and Elon does not say that so I might be conflating later and different context statements. My apologies.
It is called an "Overweight landing". No pilot is going to take the scenic route to get rid of fuel if they get a fire alarm and smoke right after take off.
Regarding the aircraft analogy - they are certified to land at any weight they are allowed to take off at, it might just be at a lower vertical speed. This is not the case for Starship as it has a maximum take off weight of ~1500 t.
Definitely wrong on this one 👆
It's very common for an aircraft to have a different maximum takeoff weight than it's maximum landing weight. In fact it's also common to have an even greater taxi weight!
I am saying that it makes sense to design a reusable launch vehicle so that landed payload mass is equal to or greater than launched payload mass.Here you say that maximum launch payload is determined by launch vehicle performance. But above you imply that the maximum launch payload should be determined by the weight that can be landed on Earth. Which is it?I am not sure I follow your logic. Maximum launch payload is determined by launch vehicle performance. Maximum landed payload on Earth is determined by heat shield performance (among other things.)Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...There is a max launch payload, a max landing payload for Earth, and max landing payloads for Luna and Mars. They are not all the same. If you are designing to be able to land on Earth the same max payload you launch, then you are designing in a reduced max launch payload.
And then you’d potentially have to rebuild the landing gear as it would be potentially yielded.It is called an "Overweight landing". No pilot is going to take the scenic route to get rid of fuel if they get a fire alarm and smoke right after take off.
Regarding the aircraft analogy - they are certified to land at any weight they are allowed to take off at, it might just be at a lower vertical speed. This is not the case for Starship as it has a maximum take off weight of ~1500 t.
Definitely wrong on this one 👆
It's very common for an aircraft to have a different maximum takeoff weight than it's maximum landing weight. In fact it's also common to have an even greater taxi weight!
Actually, it does make sense for the same reason it makes sense for airliners to demonstrably have a higher safe take-off weight than landing weight. And Shuttle Centaur was to have a fuel dump port for much the same reason.I am saying that it makes sense to design a reusable launch vehicle so that landed payload mass is equal to or greater than launched payload mass.Here you say that maximum launch payload is determined by launch vehicle performance. But above you imply that the maximum launch payload should be determined by the weight that can be landed on Earth. Which is it?I am not sure I follow your logic. Maximum launch payload is determined by launch vehicle performance. Maximum landed payload on Earth is determined by heat shield performance (among other things.)Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...There is a max launch payload, a max landing payload for Earth, and max landing payloads for Luna and Mars. They are not all the same. If you are designing to be able to land on Earth the same max payload you launch, then you are designing in a reduced max launch payload.
…
I think you want to design the launch vehicle to lift as much payload as possible. There will be times, maybe with crewed flights or with a very expensive payload, when you will launch with less than max payload in order to be able to land in an abort condition and salvage the payload. But you would not design the launch vehicle around that limitation because you will not always want to adhere to it.I am saying that it makes sense to design a reusable launch vehicle so that landed payload mass is equal to or greater than launched payload mass.Here you say that maximum launch payload is determined by launch vehicle performance. But above you imply that the maximum launch payload should be determined by the weight that can be landed on Earth. Which is it?I am not sure I follow your logic. Maximum launch payload is determined by launch vehicle performance. Maximum landed payload on Earth is determined by heat shield performance (among other things.)Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...There is a max launch payload, a max landing payload for Earth, and max landing payloads for Luna and Mars. They are not all the same. If you are designing to be able to land on Earth the same max payload you launch, then you are designing in a reduced max launch payload.
I sounds like you are saying that landed payload mass had to be smaller than launched payload mass?
I think you want to design the launch vehicle to lift as much payload as possible. There will be times, maybe with crewed flights or with a very expensive payload, when you will launch with less than max payload in order to be able to land in an abort condition and salvage the payload. But you would not design the launch vehicle around that limitation because you will not always want to adhere to it.I am saying that it makes sense to design a reusable launch vehicle so that landed payload mass is equal to or greater than launched payload mass.Here you say that maximum launch payload is determined by launch vehicle performance. But above you imply that the maximum launch payload should be determined by the weight that can be landed on Earth. Which is it?I am not sure I follow your logic. Maximum launch payload is determined by launch vehicle performance. Maximum landed payload on Earth is determined by heat shield performance (among other things.)Does not make much sense to design a reusable vehicle that can not land with its maximum payload. Especially not when the ultimate goal is to land as much payload as possible...There is a max launch payload, a max landing payload for Earth, and max landing payloads for Luna and Mars. They are not all the same. If you are designing to be able to land on Earth the same max payload you launch, then you are designing in a reduced max launch payload.
I sounds like you are saying that landed payload mass had to be smaller than launched payload mass?
No, the analogy is that an overweight airliner crashes and burns just like how a full Starship crashes and burns because the heat shield can not handle the additional mass.And then you’d potentially have to rebuild the landing gear as it would be potentially yielded.It is called an "Overweight landing". No pilot is going to take the scenic route to get rid of fuel if they get a fire alarm and smoke right after take off.
Regarding the aircraft analogy - they are certified to land at any weight they are allowed to take off at, it might just be at a lower vertical speed. This is not the case for Starship as it has a maximum take off weight of ~1500 t.
Definitely wrong on this one 👆
It's very common for an aircraft to have a different maximum takeoff weight than it's maximum landing weight. In fact it's also common to have an even greater taxi weight!
[...]Not sure why you’re being so stubborn about this, seeing as aircraft can always land at their take off weight in a contingency, that the one case where this would’ve applied to Shuttle was deemed to risky and we do not actually know whether this will apply to any variants of Starship. Can you explain your motivation as to why you insist on this, essentially crippling the landing payload of Starship so that it can't land with whatever it’s max ascent payload is?
Not sure why you’re being so stubborn about this, seeing as multiple sources show that it’s common for take off weight to exceed landed weight, that this would’ve applied to Shuttle and will likely apply to at least some variants of Starship. Can you explain your motivation as to why you insist on this, essentially crippling the ascent payload of Starship so that it could always land with whatever it’s max ascent payload is?
There seems to be a widespread belief that Starship has a low ballistic coefficient. I guess it is based on the large and fluffy appearance? ::)Your estimates seem to diverge quite a bit from CALT's: https://forum.nasaspaceflight.com/index.php?topic=56619.0
Shuttle orbiter: ~350 m2 projected, reentry mass 85 t - 105 t.
Perpendicular ballistic coefficient:
240 kg/m2 - 300 kg/m2
At 40° pitch:
380 kg/m2 - 470 kg/m2
Starship: ~580 m2 projected (flaps akimbo), reentry mass 150 t - 300 t.
Perpendicular ballistic coefficient:
260 kg/m2 - 520 kg/m2
At 70° pitch:
280 kg/m2 - 550 kg/m2
The reference area for Starship will actually be significantly smaller as the flaps will have some dihedral and a cylindrical body has roughly half the drag of a flat bottomed one.
While many reentries will be empty and relatively light the heat shield will be designed for the heaviest case.
In what way? For Starship they have 140 t, 545 m2 of "waterline" area and a ballistic coefficient of 275 kg/m2 at presumably 70° of pitch.There seems to be a widespread belief that Starship has a low ballistic coefficient. I guess it is based on the large and fluffy appearance? ::)Your estimates seem to diverge quite a bit from CALT's: https://forum.nasaspaceflight.com/index.php?topic=56619.0
Shuttle orbiter: ~350 m2 projected, reentry mass 85 t - 105 t.
Perpendicular ballistic coefficient:
240 kg/m2 - 300 kg/m2
At 40° pitch:
380 kg/m2 - 470 kg/m2
Starship: ~580 m2 projected (flaps akimbo), reentry mass 150 t - 300 t.
Perpendicular ballistic coefficient:
260 kg/m2 - 520 kg/m2
At 70° pitch:
280 kg/m2 - 550 kg/m2
The reference area for Starship will actually be significantly smaller as the flaps will have some dihedral and a cylindrical body has roughly half the drag of a flat bottomed one.
While many reentries will be empty and relatively light the heat shield will be designed for the heaviest case.
No, the analogy is that an overweight airliner crashes and burns just like how a full Starship crashes and burns because the heat shield can not handle the additional mass.And then you’d potentially have to rebuild the landing gear as it would be potentially yielded.It is called an "Overweight landing". No pilot is going to take the scenic route to get rid of fuel if they get a fire alarm and smoke right after take off.
Regarding the aircraft analogy - they are certified to land at any weight they are allowed to take off at, it might just be at a lower vertical speed. This is not the case for Starship as it has a maximum take off weight of ~1500 t.
Definitely wrong on this one 👆
It's very common for an aircraft to have a different maximum takeoff weight than it's maximum landing weight. In fact it's also common to have an even greater taxi weight!
Inspecting and potentially repairing the landing gear would be like a full Starship reentering just fine but requiring inspections and possibly extra refurbishment which is crazy talk ::)
And then you’d potentially have to rebuild the landing gear as it would be potentially yielded.It is called an "Overweight landing". No pilot is going to take the scenic route to get rid of fuel if they get a fire alarm and smoke right after take off.
Regarding the aircraft analogy - they are certified to land at any weight they are allowed to take off at, it might just be at a lower vertical speed. This is not the case for Starship as it has a maximum take off weight of ~1500 t.
Definitely wrong on this one 👆
It's very common for an aircraft to have a different maximum takeoff weight than it's maximum landing weight. In fact it's also common to have an even greater taxi weight!
The emissive (ablative?) paint is flaking off a bit on S24:
https://twitter.com/cnunezimages/status/1632856594672222208
The emissive (ablative?) paint is flaking off a bit on S24:
https://twitter.com/cnunezimages/status/1632856594672222208
I'm pretty sure this is just a paint and has nothing to do with heat shielding
The emissive (ablative?) paint is flaking off a bit on S24:
https://twitter.com/cnunezimages/status/1632856594672222208
I'm pretty sure this is just a paint and has nothing to do with heat shielding
Why would they only paint next to the heat shield were heat can still be high?
Paint can be a heat shield, using two different methods:
1. The emissivity of stainless steel is 0.35.
I think the paint is just for "pretty".
John
Soot on the F9 first stage is an advertisement for reusability. On the Starship booster they are just using paint to make clean lines that look well "engineered". In neither case is form following function.I think the paint is just for "pretty".
John
Maybe. But i would totally argue that form follow the function is just too strong in spaceX ethos. Jusk check out how Falcon 9 boosters look after couple reentries.
Soot on the F9 first stage is an advertisement for reusability. On the Starship booster they are just using paint to make clean lines that look well "engineered". In neither case is form following function.I think the paint is just for "pretty".
John
Maybe. But i would totally argue that form follow the function is just too strong in spaceX ethos. Jusk check out how Falcon 9 boosters look after couple reentries.
Where are you seeing that?
NASA says (https://ntrs.nasa.gov/api/citations/19840015630/downloads/19840015630.pdf) the emissivity of stainless is <.15 unless the surface has a sandblasted finish. AFAIK Starship does not have a sandblasted finish.
This only reinforces your main point, of course.
A possible alternative: Elon is big on visuals.The emissive (ablative?) paint is flaking off a bit on S24:
https://twitter.com/cnunezimages/status/1632856594672222208 (https://twitter.com/cnunezimages/status/1632856594672222208)
I'm pretty sure this is just a paint and has nothing to do with heat shielding
Why would they only paint next to the heat shield were heat can still be high?
Paint can be a heat shield, using two different methods:
1. The emissivity of stainless steel is 0.35. A black paint, the special kinds, can get to 0.99, same as the tiles. This nearly triples the watts being emitted from a hot section of steel.
2. Ablative
Either of those count towards managing the heat of reentry, and thus count as a heat shield
Otherwise there's zero reason to paint at all. "best part is no part".
I think the paint is just for "pretty".is this really a paint? looks to be a goo they used as the base to clue tiles on. (it is quite thick as you can see in the damaged spots.The form indicates initial design specs.
John
I think the paint is just for "pretty".is this really a paint? looks to be a goo they used as the base to clue tiles on. (it is quite thick as you can see in the damaged spots.The form indicates initial design specs.
John
Now I've been wondering for quite some time about the practical implementation of the problem where the creative tile shapes discussed here have not been used. Instead, dead-straight joints were arranged in the nose cone area. Sorry I haven't gone through all the >170 pages here yet, can someone please give me a link if this has already been discussed and justified here?
Do we have a consensus guess for the maximum entry speed that Starship must handle? Do you think it'll be higher or lower than 11km/s?
Am I correct in assuming that, from a thermal standpoint, it doesn't matter much whether the entry is on Earth or Mars? (Constraining the amount of permissible negative lift needed to keep the vehicle in the atmosphere on Mars is another story...)
Heat loads are significantly higher on Earth than on Mars, due to the higher velocity of entry. Mars entry velocity is typically around 4.5-7.5ish km/s for the various probes NASA has sent.
If entry speed is your limiting factor then wouldn't it be best to include a braking burn almost by definition?Heat loads are significantly higher on Earth than on Mars, due to the higher velocity of entry. Mars entry velocity is typically around 4.5-7.5ish km/s for the various probes NASA has sent.
I was looking for an apples-to-apples, entry-speed-normalized answer to that question. I'm assuming that heat loads for an 11.4km/s entry speed (not v∞) on Earth and Mars should be roughly the same. (If you know the entry speed, you can figure out the v∞, a vice versa.) The Mars entry trajectory will stabilize lower in the atmosphere, but the differences in composition should have only a small effect, correct?
Good point about needing to be able to cover the free return case.
I'm fooling with this because I want to be able to constrain arrival v∞ in both directions. That seems to be more of a gating item on time of flight than the departure v∞. However, if you're flying a with a full load of prop, you can keep some propulsive braking prop. But that of course limits your departure speed in a different way...
Heat loads are significantly higher on Earth than on Mars, due to the higher velocity of entry. Mars entry velocity is typically around 4.5-7.5ish km/s for the various probes NASA has sent.
I was looking for an apples-to-apples, entry-speed-normalized answer to that question. I'm assuming that heat loads for an 11.4km/s entry speed (not v∞) on Earth and Mars should be roughly the same. (If you know the entry speed, you can figure out the v∞, a vice versa.) The Mars entry trajectory will stabilize lower in the atmosphere, but the differences in composition should have only a small effect, correct?
Heat loads are significantly higher on Earth than on Mars, due to the higher velocity of entry. Mars entry velocity is typically around 4.5-7.5ish km/s for the various probes NASA has sent.
I was looking for an apples-to-apples, entry-speed-normalized answer to that question. I'm assuming that heat loads for an 11.4km/s entry speed (not v∞) on Earth and Mars should be roughly the same. (If you know the entry speed, you can figure out the v∞, a vice versa.) The Mars entry trajectory will stabilize lower in the atmosphere, but the differences in composition should have only a small effect, correct?
Not really.
Mars has different atmospheric composition which, among other things, means:
* A higher Mach number (for the same velocity). Your 12.5km/s Mach 46 Earth atmosphere entry is Mach 60 in CO2 atmosphere.
* Very different radiative environment in and behind the bow shock.
The net result is that even Mars ballistic entries are considered worse than Earth ones at the same speed.
But all of this is minor.
The major part is that at Mars you must do negative lifting entry at anything even similar to Earth's LEO entry, not to mention interplanetary entry. And the thing is at high Mach numbers your L:D ratio is severely limited. This dictates high g-loads. And high g-loads mean ~proportionally higher heating rates.
IOW At Earth you could limit your heating rate by skidding on top of the atmosphere for quite a while. Not so much on Mars where you must accept high g-load and accompanying heating rate.
I did some simplified sims a while ago - as stated above entries at Mars are generally gentler because they are slower. At the same entry velocity the peak temperature and g-forces are higher due to the smaller radius and gravity.
A 6 km/s entry at Mars has about the same peak temperature as an 8 km/s entry at Earth. If you have a 5 g0 limit the max entry speed at Mars is 12 km/s and at Earth it is 15 km/s.
I expect an fully reusable tile bases heat shield to be good for LEO and multi-pass cis-lunar as well as slow Mars transfer and Mars Orbit. For fast Mars transfers and Earth return I think they will need an ablative heat shield.
Yes, Starship according to various reports has L:D from 0.5 to 0.8.
At reportedly nominal 60° AoA I'd expect L:D ~0.5
Still, at Earth, due to lower curvature you could skim the atmosphere for quite a bit without even trying to produce lift. You could fly for about 2800km (with half of that in a densest zone providing ~90% of braking) with zero lift and stay with g-loads below 1. So you could start your reentry at over 12km/s and without any lift and without exceeding 1g slow down enough to capture.
If you tried the same exercise at Mars, at 12km/s you'd just reduce your velocity to 11.75km/s or so and wouldn't be appreciably closer to capture.
But if you have non-ablative heatshield, you prefer skidding on top of the atmosphere. The heat pulse is larger (often significantly), but you keep peak heating in check by keeping the whole kinetic energy drop rate in check. But if you have to generate more (negative) lift to hold onto a small low planet, you need to increase drag according to L:D ratio of your vehicle, which means higher deceleration which means higher kinetic energy drop rate and higher heating.
"Apparently all the Starship thermal protection system tiles started washing up on South Padre Island yesterday (~3 weeks post launch)"
https://twitter.com/DrChrisCombs/status/1656762126151700480 (https://twitter.com/DrChrisCombs/status/1656762126151700480)
"Apparently all the Starship thermal protection system tiles started washing up on South Padre Island yesterday (~3 weeks post launch)"
https://twitter.com/DrChrisCombs/status/1656762126151700480 (https://twitter.com/DrChrisCombs/status/1656762126151700480)
Good material for a trencadís project.
If China doesn’t have somebody down there in South Texas hunting for heat shield tiles, then they are incompetent.They're sintered silica fibre tiles with a Borosilicate RCG surface layer. The geometry and attachment method is novel (but also already public knowledge), the composition is not. China can already manufacture their own (https://www.mdpi.com/2079-6412/13/2/463/pdf).
Sure, but you would likely not get approval to sell heatshield tiles direct to China.If China doesn’t have somebody down there in South Texas hunting for heat shield tiles, then they are incompetent.They're sintered silica fibre tiles with a Borosilicate RCG surface layer. The geometry and attachment method is novel (but also already public knowledge), the composition is not. China can already manufacture their own (https://www.mdpi.com/2079-6412/13/2/463/pdf).
China have no need to scrabble in the dirt to gather something they can already make.
Flotsam heat shield tiles from SN-24 collected at South Padre Island beaches are now up for bid on eBay (some are mis-identified as SN-11).There were plenty of SN11 tiles picked up. I've used some myself.
Flotsam heat shield tiles from SN-24 collected at South Padre Island beaches are now up for bid on eBay (some are mis-identified as SN-11).There were plenty of SN11 tiles picked up. I've used some myself.
Never thought of that. Maybe on my next visit to the storehouse. i'm wandering around Ireland for some reason at the moment.Flotsam heat shield tiles from SN-24 collected at South Padre Island beaches are now up for bid on eBay (some are mis-identified as SN-11).There were plenty of SN11 tiles picked up. I've used some myself.
Nomadd:
Have you tried a soak/freeze cycle to see how bad they fall apart when frozen while wet?
I would love to hear the result of that experiment.
Flotsam heat shield tiles from SN-24 collected at South Padre Island beaches are now up for bid on eBay (some are mis-identified as SN-11).There were plenty of SN11 tiles picked up. I've used some myself.
They are still property of spacex. But they obligated to clear the debris on their own cost.Im not sure that it is. It didn’t go to space, so the usual OST provision may not apply.
They are still property of spacex. But they obligated to clear the debris on their own cost.Im not sure that it is. It didn’t go to space, so the usual OST provision may not apply.
The Space Liability Convention still applies to launch vehicles that do not reach orbit (or above the Karman line), so SpaceX would be liable for cleanup. Ownership is undefined beyond 'Objects launched into reach Outer Space' - could be interpreted as covering attempted but failed launches to Outer Space, or could be interpreted as only objects that actually reach Outer Space are covered, leaving a grey area for suborbital rocket bodies and failed launches. Presumably all parties would - if ever challenged - wish the interpretation to cover suborbital objects too (to dissuade theft and aid recovery of items from failed launches, e.g. the Discoverer 2 situation) but this would to be clarified unless challenged.They are still property of spacex. But they obligated to clear the debris on their own cost.Im not sure that it is. It didn’t go to space, so the usual OST provision may not apply.
You are posting your supposition about the law as if it is fact. The clear wording of the law does not say it applies to failed launches which never reach space.The clear working of the law is in fact clear, Article I Parts (b) and (d) (https://www.unoosa.org/pdf/gares/ARES_26_2777E.pdf):
(b) The term "launching" includes attempted launching;
[...]
(d) The term "space object" includes component parts of
a object as well as its launch vehicle and parts threof.
You are posting your supposition about the law as if it is fact. The clear wording of the law does not say it applies to failed launches which never reach space.The clear working of the law is in fact clear, Article I Parts (b) and (d) (https://www.unoosa.org/pdf/gares/ARES_26_2777E.pdf):Quote(b) The term "launching" includes attempted launching;
[...]
(d) The term "space object" includes component parts of
a object as well as its launch vehicle and parts threof.
I stand corrected! Thank you.You are posting your supposition about the law as if it is fact. The clear wording of the law does not say it applies to failed launches which never reach space.The clear working of the law is in fact clear, Article I Parts (b) and (d) (https://www.unoosa.org/pdf/gares/ARES_26_2777E.pdf):Quote(b) The term "launching" includes attempted launching;
[...]
(d) The term "space object" includes component parts of
a object as well as its launch vehicle and parts threof.
Awesome video here of someone torching a piece of Starship Heatshield Tile! Look how quickly that heat is dissipated! 🔥
📸: @ Keith Yates | facebook.com/groups/1541938…
I think for thermal you have 2 primary constraints, not 1:
1. Heat pulse, i.e. the one you mentioned. This is the amount of energy which gets to your ship.
2. Peak heating. This is the maximum heating rate. Among other things this dictates skin temperature.
Ablative heat shields are primarily concerned with the first (1). But non-ablative ones are concerned with both (1 & 2), and it's easier to adjust them for 1 if a need arises (generally you improve the insulation layer). But adjusting for a higher peak heating (2) essentially means coming up with a different material which is not an easy change, and often means redoing your heatshield from scratch. And If you ramp peak heating just a tad too much we're simply out of known materials at all.
The thing about (2) is that it depends not just on velocity. It depends on deceleration as well. If you replace 2g braking with 4g braking you essentially doubled your peak heating.
At the same time you have likely reduced(!) heat pulse! This is counterintuitive, because kinetic energy to lose is the same regardless of how quickly you drop it. But the thing is, at certain point the more rarefied the ambient atmosphere the larger fraction of heat gets to the vehicle (and less is taken away by the ambient air). So when you pass entry interface heating initially grows much faster than deceleration. Just look at Shuttle reentry heating and deceleration profiles. Or some (SpaceX?) materials about Starship reentry. You're dropping speed slowly while heating is already high.
So if you have an ablative heatshield, you want to punch through the too thin air fast into high deceleration region. Total heat pulse is less that way, so you need less material to ablate. And you don't care that much about peak heating (within limits), as the temperature is primarily set by your ablative material's phase changes.
But if you have non-ablative heatshield, you prefer skidding on top of the atmosphere. The heat pulse is larger (often significantly), but you keep peak heating in check by keeping the whole kinetic energy drop rate in check. But if you have to generate more (negative) lift to hold onto a small low planet, you need to increase drag according to L:D ratio of your vehicle, which means higher deceleration which means higher kinetic energy drop rate and higher heating.
Heat pulse cooling post aerocapture is still non-trivial. You gotta deploy radiators fairly quickly once you pull out of the reentry dive, plus do a burn at apogee to keep you out of atmosphere for the period necessary to get cooling into a stable state in your elliptical loiter orbit until you decide to come down for another atmosphere run or EDL.
There's also the weird trade space of skip glide reetries post-aerocapture, where the heat pulse problem magnifies but you may be able to reduce peak heating.
I think for thermal you have 2 primary constraints, not 1:
1. Heat pulse, i.e. the one you mentioned. This is the amount of energy which gets to your ship.
2. Peak heating. This is the maximum heating rate. Among other things this dictates skin temperature.
Ablative heat shields are primarily concerned with the first (1). But non-ablative ones are concerned with both (1 & 2), and it's easier to adjust them for 1 if a need arises (generally you improve the insulation layer). But adjusting for a higher peak heating (2) essentially means coming up with a different material which is not an easy change, and often means redoing your heatshield from scratch. And If you ramp peak heating just a tad too much we're simply out of known materials at all.
The thing about (2) is that it depends not just on velocity. It depends on deceleration as well. If you replace 2g braking with 4g braking you essentially doubled your peak heating.
At the same time you have likely reduced(!) heat pulse! This is counterintuitive, because kinetic energy to lose is the same regardless of how quickly you drop it. But the thing is, at certain point the more rarefied the ambient atmosphere the larger fraction of heat gets to the vehicle (and less is taken away by the ambient air). So when you pass entry interface heating initially grows much faster than deceleration. Just look at Shuttle reentry heating and deceleration profiles. Or some (SpaceX?) materials about Starship reentry. You're dropping speed slowly while heating is already high.
So if you have an ablative heatshield, you want to punch through the too thin air fast into high deceleration region. Total heat pulse is less that way, so you need less material to ablate. And you don't care that much about peak heating (within limits), as the temperature is primarily set by your ablative material's phase changes.
But if you have non-ablative heatshield, you prefer skidding on top of the atmosphere. The heat pulse is larger (often significantly), but you keep peak heating in check by keeping the whole kinetic energy drop rate in check. But if you have to generate more (negative) lift to hold onto a small low planet, you need to increase drag according to L:D ratio of your vehicle, which means higher deceleration which means higher kinetic energy drop rate and higher heating.
First, I never thanked you for this post. It's a very clear problem statement, and I refer back to it quite often.
So how do things change if Starship intends to aerocapture instead of doing a direct EDL? (This question applies for both Mars and Earth entry.)
I can think of a few of things:
1) You don't have to kill all the speed in a single direct EDL. You only need enough to get you captured into an eccentric orbit. That presumably makes the path through the atmosphere shorter, which reduces the heat pulse.
2) The Starship can cold-soak or barbecue roll to radiate away the heat pulse before beginning the actual EDL.
3) You also obviously get a chance to null out any guidance irregularities, allowing changes to both periapse altitude and inclination post-aerocapture.
4) The radius of curvature of the path requiring negative lift can be substantially greater, resulting in lower lift, which in turn reduces the amount of drag that's required.
It's #4 that I'm most curious about. (See attachment.) The deeper you can dip into the atmosphere before pulling out, the larger the radius of curvature of the path where substantial drag is produced. But that means that the Starship has to endure a very brief period of high drag, and therefore high peak heating. You obviously can't exceed a dynamic pressure that causes so high a peak heating that the tiles fail, but they're not going to soak at that temperature for very long. This is the kinda-in-between case between pure peak heating and total heat pulse.
Is there a pony in here somewhere? As always, the name of the game is the highest tolerable arrival v∞.
Heat pulse cooling post aerocapture is still non-trivial. You gotta deploy radiators fairly quickly once you pull out of the reentry dive, plus do a burn at apogee to keep you out of atmosphere for the period necessary to get cooling into a stable state in your elliptical loiter orbit until you decide to come down for another atmosphere run or EDL.
There's also the weird trade space of skip glide reetries post-aerocapture, where the heat pulse problem magnifies but you may be able to reduce peak heating.
Why would you need to deploy radiators? Post-aerocapture the heat will radiate away from the tiles and also into the tanks. Tanks would be vented to control pressure. I don't see how radiators would help.
John
.
4) The radius of curvature of the path requiring negative lift can be substantially greater, resulting in lower lift, which in turn reduces the amount of drag that's required.
It's #4 that I'm most curious about. (See attachment.) The deeper you can dip into the atmosphere before pulling out, the larger the radius of curvature of the path where substantial drag is produced. But that means that the Starship has to endure a very brief period of high drag, and therefore high peak heating. You obviously can't exceed a dynamic pressure that causes so high a peak heating that the tiles fail, but they're not going to soak at that temperature for very long. This is the kinda-in-between case between pure peak heating and total heat pulse.
Is there a pony in here somewhere? As always, the name of the game is the highest tolerable arrival v∞.
Heat pulse cooling post aerocapture is still non-trivial. You gotta deploy radiators fairly quickly once you pull out of the reentry dive, plus do a burn at apogee to keep you out of atmosphere for the period necessary to get cooling into a stable state in your elliptical loiter orbit until you decide to come down for another atmosphere run or EDL.
There's also the weird trade space of skip glide reetries post-aerocapture, where the heat pulse problem magnifies but you may be able to reduce peak heating.
Why would you need to deploy radiators? Post-aerocapture the heat will radiate away from the tiles and also into the tanks. Tanks would be vented to control pressure. I don't see how radiators would help.
John
Heat pulse cooling post aerocapture is still non-trivial. You gotta deploy radiators fairly quickly once you pull out of the reentry dive, plus do a burn at apogee to keep you out of atmosphere for the period necessary to get cooling into a stable state in your elliptical loiter orbit until you decide to come down for another atmosphere run or EDL.
There's also the weird trade space of skip glide reetries post-aerocapture, where the heat pulse problem magnifies but you may be able to reduce peak heating.
Only a small fraction (~5%?) of the heat makes it into the tanks.
Why would you need to deploy radiators? Post-aerocapture the heat will radiate away from the tiles and also into the tanks. Tanks would be vented to control pressure. I don't see how radiators would help.
John
Well, I suppose that's a question of how much you're willing to vent. If you need to do an apogee burn anyways and using primary propellant tanks as a temporary heatsink, I suppose you could try to kill two birds with one stone by using gaseous RCS to both relieve pressure and do the burn... not the most efficient method but it is expedient plus uses existing equipment. Hrm, I wonder if you could front end the inputs to RCS with a vortex tube cooler to get some free cooling with your burn...
But the impression I get is you will end up needing to run the cryocooler to deal with the remaining heat to prevent all the propellant going to gas and exceeding tank pressure, plus the Raptors expect liquid propellants so you can't let it all go to gas even if you could keep it in the tank. Well, assuming you don't offload any remaining propellant to some other storage system, since Starship isn't ideal for long term propellant storage anyways. The consensus is Starship will have a cryocooler for interplanetary cruise, but a cooler sized for that is much smaller than one trying to overcome structural heat pulses.
What exactly is the TPS material in Starship?
Apologies in advance since it's probably been discussed to no end already, but this thread is gigantic and I couldn't find it.
What exactly is the TPS material in Starship?Sintered silica fibre bricks, with an outer coating of borosilicate reaction-cured glass, methyl-trimethoxy silane (MTMS) waterproofing agent [1], with embedded metallic 'track' inserts (metal unknown [2]) used to latch onto the pins for the flat tiles - the curved tiles (e.g. for the nose tip, flap leading edges, etc) that are glued in place using silicone adhesive lack the metal inserts.
Apologies in advance since it's probably been discussed to no end already, but this thread is gigantic and I couldn't find it.
I think for thermal you have 2 primary constraints, not 1:
1. Heat pulse, i.e. the one you mentioned. This is the amount of energy which gets to your ship.
2. Peak heating. This is the maximum heating rate. Among other things this dictates skin temperature.
Ablative heat shields are primarily concerned with the first (1). But non-ablative ones are concerned with both (1 & 2), and it's easier to adjust them for 1 if a need arises (generally you improve the insulation layer). But adjusting for a higher peak heating (2) essentially means coming up with a different material which is not an easy change, and often means redoing your heatshield from scratch. And If you ramp peak heating just a tad too much we're simply out of known materials at all.
The thing about (2) is that it depends not just on velocity. It depends on deceleration as well. If you replace 2g braking with 4g braking you essentially doubled your peak heating.
At the same time you have likely reduced(!) heat pulse! This is counterintuitive, because kinetic energy to lose is the same regardless of how quickly you drop it. But the thing is, at certain point the more rarefied the ambient atmosphere the larger fraction of heat gets to the vehicle (and less is taken away by the ambient air). So when you pass entry interface heating initially grows much faster than deceleration. Just look at Shuttle reentry heating and deceleration profiles. Or some (SpaceX?) materials about Starship reentry. You're dropping speed slowly while heating is already high.
So if you have an ablative heatshield, you want to punch through the too thin air fast into high deceleration region. Total heat pulse is less that way, so you need less material to ablate. And you don't care that much about peak heating (within limits), as the temperature is primarily set by your ablative material's phase changes.
But if you have non-ablative heatshield, you prefer skidding on top of the atmosphere. The heat pulse is larger (often significantly), but you keep peak heating in check by keeping the whole kinetic energy drop rate in check. But if you have to generate more (negative) lift to hold onto a small low planet, you need to increase drag according to L:D ratio of your vehicle, which means higher deceleration which means higher kinetic energy drop rate and higher heating.
First, I never thanked you for this post. It's a very clear problem statement, and I refer back to it quite often.
So how do things change if Starship intends to aerocapture instead of doing a direct EDL? (This question applies for both Mars and Earth entry.)
I can think of a few of things:
1) You don't have to kill all the speed in a single direct EDL. You only need enough to get you captured into an eccentric orbit. That presumably makes the path through the atmosphere shorter, which reduces the heat pulse.
2) The Starship can cold-soak or barbecue roll to radiate away the heat pulse before beginning the actual EDL.
3) You also obviously get a chance to null out any guidance irregularities, allowing changes to both periapse altitude and inclination post-aerocapture.
4) The radius of curvature of the path requiring negative lift can be substantially greater, resulting in lower lift, which in turn reduces the amount of drag that's required.
It's #4 that I'm most curious about. (See attachment.) The deeper you can dip into the atmosphere before pulling out, the larger the radius of curvature of the path where substantial drag is produced. But that means that the Starship has to endure a very brief period of high drag, and therefore high peak heating. You obviously can't exceed a dynamic pressure that causes so high a peak heating that the tiles fail, but they're not going to soak at that temperature for very long. This is the kinda-in-between case between pure peak heating and total heat pulse.
Is there a pony in here somewhere? As always, the name of the game is the highest tolerable arrival v∞.
That technique is known as 'aerocapture', and the major barrier is knowing atmosphere state at time of entry in order to properly plot a trajectory to scrub just enough velocity to enter the target orbit (too much = early entry at an uncontrolled location on an undesired trajectory, too little = escape). Proposals to solve that problem include a swathe of probes sent ahead by a few hours to map multiple runs through the atmosphere to map density & temperature, and pre-placing Mars weather satellites to continuously measure the atmosphere in order to build and regularly update a volumetric atmospheric model.I think for thermal you have 2 primary constraints, not 1:
1. Heat pulse, i.e. the one you mentioned. This is the amount of energy which gets to your ship.
2. Peak heating. This is the maximum heating rate. Among other things this dictates skin temperature.
Ablative heat shields are primarily concerned with the first (1). But non-ablative ones are concerned with both (1 & 2), and it's easier to adjust them for 1 if a need arises (generally you improve the insulation layer). But adjusting for a higher peak heating (2) essentially means coming up with a different material which is not an easy change, and often means redoing your heatshield from scratch. And If you ramp peak heating just a tad too much we're simply out of known materials at all.
The thing about (2) is that it depends not just on velocity. It depends on deceleration as well. If you replace 2g braking with 4g braking you essentially doubled your peak heating.
At the same time you have likely reduced(!) heat pulse! This is counterintuitive, because kinetic energy to lose is the same regardless of how quickly you drop it. But the thing is, at certain point the more rarefied the ambient atmosphere the larger fraction of heat gets to the vehicle (and less is taken away by the ambient air). So when you pass entry interface heating initially grows much faster than deceleration. Just look at Shuttle reentry heating and deceleration profiles. Or some (SpaceX?) materials about Starship reentry. You're dropping speed slowly while heating is already high.
So if you have an ablative heatshield, you want to punch through the too thin air fast into high deceleration region. Total heat pulse is less that way, so you need less material to ablate. And you don't care that much about peak heating (within limits), as the temperature is primarily set by your ablative material's phase changes.
But if you have non-ablative heatshield, you prefer skidding on top of the atmosphere. The heat pulse is larger (often significantly), but you keep peak heating in check by keeping the whole kinetic energy drop rate in check. But if you have to generate more (negative) lift to hold onto a small low planet, you need to increase drag according to L:D ratio of your vehicle, which means higher deceleration which means higher kinetic energy drop rate and higher heating.
First, I never thanked you for this post. It's a very clear problem statement, and I refer back to it quite often.
So how do things change if Starship intends to aerocapture instead of doing a direct EDL? (This question applies for both Mars and Earth entry.)
I can think of a few of things:
1) You don't have to kill all the speed in a single direct EDL. You only need enough to get you captured into an eccentric orbit. That presumably makes the path through the atmosphere shorter, which reduces the heat pulse.
2) The Starship can cold-soak or barbecue roll to radiate away the heat pulse before beginning the actual EDL.
3) You also obviously get a chance to null out any guidance irregularities, allowing changes to both periapse altitude and inclination post-aerocapture.
4) The radius of curvature of the path requiring negative lift can be substantially greater, resulting in lower lift, which in turn reduces the amount of drag that's required.
It's #4 that I'm most curious about. (See attachment.) The deeper you can dip into the atmosphere before pulling out, the larger the radius of curvature of the path where substantial drag is produced. But that means that the Starship has to endure a very brief period of high drag, and therefore high peak heating. You obviously can't exceed a dynamic pressure that causes so high a peak heating that the tiles fail, but they're not going to soak at that temperature for very long. This is the kinda-in-between case between pure peak heating and total heat pulse.
Is there a pony in here somewhere? As always, the name of the game is the highest tolerable arrival v∞.
I wonder if since SS will be the first vehicle heading to mars with a reusable heat shield it will not do a capture burn, but instead only aerobrake.
IIRC all missions to mars have either 1) directly plunged in the atmosphere and EDLed, because they had ablative heat shields 2)did a capture burn aided by aerobraking
This maneuver would save a lot of dV, but the heating pulse and peak heating would need to be carefully studied. Also SS could aerobrake in a very elliptical orbit, but that orbit might be month long, and so they would probably want to get deeper in the atmosphere to scrub more velocity.
That technique is known as 'aerocapture', and the major barrier is knowing atmosphere state at time of entry in order to properly plot a trajectory to scrub just enough velocity to enter the target orbit (too much = early entry at an uncontrolled location on an undesired trajectory, too little = escape). Proposals to solve that problem include a swathe of probes sent ahead by a few hours to map multiple runs through the atmosphere to map density & temperature, and pre-placing Mars weather satellites to continuously measure the atmosphere in order to build and regularly update a volumetric atmospheric model.I think for thermal you have 2 primary constraints, not 1:
1. Heat pulse, i.e. the one you mentioned. This is the amount of energy which gets to your ship.
2. Peak heating. This is the maximum heating rate. Among other things this dictates skin temperature.
Ablative heat shields are primarily concerned with the first (1). But non-ablative ones are concerned with both (1 & 2), and it's easier to adjust them for 1 if a need arises (generally you improve the insulation layer). But adjusting for a higher peak heating (2) essentially means coming up with a different material which is not an easy change, and often means redoing your heatshield from scratch. And If you ramp peak heating just a tad too much we're simply out of known materials at all.
The thing about (2) is that it depends not just on velocity. It depends on deceleration as well. If you replace 2g braking with 4g braking you essentially doubled your peak heating.
At the same time you have likely reduced(!) heat pulse! This is counterintuitive, because kinetic energy to lose is the same regardless of how quickly you drop it. But the thing is, at certain point the more rarefied the ambient atmosphere the larger fraction of heat gets to the vehicle (and less is taken away by the ambient air). So when you pass entry interface heating initially grows much faster than deceleration. Just look at Shuttle reentry heating and deceleration profiles. Or some (SpaceX?) materials about Starship reentry. You're dropping speed slowly while heating is already high.
So if you have an ablative heatshield, you want to punch through the too thin air fast into high deceleration region. Total heat pulse is less that way, so you need less material to ablate. And you don't care that much about peak heating (within limits), as the temperature is primarily set by your ablative material's phase changes.
But if you have non-ablative heatshield, you prefer skidding on top of the atmosphere. The heat pulse is larger (often significantly), but you keep peak heating in check by keeping the whole kinetic energy drop rate in check. But if you have to generate more (negative) lift to hold onto a small low planet, you need to increase drag according to L:D ratio of your vehicle, which means higher deceleration which means higher kinetic energy drop rate and higher heating.
First, I never thanked you for this post. It's a very clear problem statement, and I refer back to it quite often.
So how do things change if Starship intends to aerocapture instead of doing a direct EDL? (This question applies for both Mars and Earth entry.)
I can think of a few of things:
1) You don't have to kill all the speed in a single direct EDL. You only need enough to get you captured into an eccentric orbit. That presumably makes the path through the atmosphere shorter, which reduces the heat pulse.
2) The Starship can cold-soak or barbecue roll to radiate away the heat pulse before beginning the actual EDL.
3) You also obviously get a chance to null out any guidance irregularities, allowing changes to both periapse altitude and inclination post-aerocapture.
4) The radius of curvature of the path requiring negative lift can be substantially greater, resulting in lower lift, which in turn reduces the amount of drag that's required.
It's #4 that I'm most curious about. (See attachment.) The deeper you can dip into the atmosphere before pulling out, the larger the radius of curvature of the path where substantial drag is produced. But that means that the Starship has to endure a very brief period of high drag, and therefore high peak heating. You obviously can't exceed a dynamic pressure that causes so high a peak heating that the tiles fail, but they're not going to soak at that temperature for very long. This is the kinda-in-between case between pure peak heating and total heat pulse.
Is there a pony in here somewhere? As always, the name of the game is the highest tolerable arrival v∞.
I wonder if since SS will be the first vehicle heading to mars with a reusable heat shield it will not do a capture burn, but instead only aerobrake.
IIRC all missions to mars have either 1) directly plunged in the atmosphere and EDLed, because they had ablative heat shields 2)did a capture burn aided by aerobraking
This maneuver would save a lot of dV, but the heating pulse and peak heating would need to be carefully studied. Also SS could aerobrake in a very elliptical orbit, but that orbit might be month long, and so they would probably want to get deeper in the atmosphere to scrub more velocity.
EDL spends a decent amount of time in the lower atmosphere, which is more 'stable' (e.g. for Mars a 1 Pa variance at 20km is a 1% change in pressure, a 1 Pa variance at 60km is a 100% variance in pressure), and for EDL a velocity residual has less of an effect on final trajectory than for aerocapture (an extra 100m/s may land you a few km down your landing ellipse, but an extra 100m/s after capture may be an escape trajectory or need 100m/s extra deltaV to correct).That technique is known as 'aerocapture', and the major barrier is knowing atmosphere state at time of entry in order to properly plot a trajectory to scrub just enough velocity to enter the target orbit (too much = early entry at an uncontrolled location on an undesired trajectory, too little = escape). Proposals to solve that problem include a swathe of probes sent ahead by a few hours to map multiple runs through the atmosphere to map density & temperature, and pre-placing Mars weather satellites to continuously measure the atmosphere in order to build and regularly update a volumetric atmospheric model.I think for thermal you have 2 primary constraints, not 1:
1. Heat pulse, i.e. the one you mentioned. This is the amount of energy which gets to your ship.
2. Peak heating. This is the maximum heating rate. Among other things this dictates skin temperature.
Ablative heat shields are primarily concerned with the first (1). But non-ablative ones are concerned with both (1 & 2), and it's easier to adjust them for 1 if a need arises (generally you improve the insulation layer). But adjusting for a higher peak heating (2) essentially means coming up with a different material which is not an easy change, and often means redoing your heatshield from scratch. And If you ramp peak heating just a tad too much we're simply out of known materials at all.
The thing about (2) is that it depends not just on velocity. It depends on deceleration as well. If you replace 2g braking with 4g braking you essentially doubled your peak heating.
At the same time you have likely reduced(!) heat pulse! This is counterintuitive, because kinetic energy to lose is the same regardless of how quickly you drop it. But the thing is, at certain point the more rarefied the ambient atmosphere the larger fraction of heat gets to the vehicle (and less is taken away by the ambient air). So when you pass entry interface heating initially grows much faster than deceleration. Just look at Shuttle reentry heating and deceleration profiles. Or some (SpaceX?) materials about Starship reentry. You're dropping speed slowly while heating is already high.
So if you have an ablative heatshield, you want to punch through the too thin air fast into high deceleration region. Total heat pulse is less that way, so you need less material to ablate. And you don't care that much about peak heating (within limits), as the temperature is primarily set by your ablative material's phase changes.
But if you have non-ablative heatshield, you prefer skidding on top of the atmosphere. The heat pulse is larger (often significantly), but you keep peak heating in check by keeping the whole kinetic energy drop rate in check. But if you have to generate more (negative) lift to hold onto a small low planet, you need to increase drag according to L:D ratio of your vehicle, which means higher deceleration which means higher kinetic energy drop rate and higher heating.
First, I never thanked you for this post. It's a very clear problem statement, and I refer back to it quite often.
So how do things change if Starship intends to aerocapture instead of doing a direct EDL? (This question applies for both Mars and Earth entry.)
I can think of a few of things:
1) You don't have to kill all the speed in a single direct EDL. You only need enough to get you captured into an eccentric orbit. That presumably makes the path through the atmosphere shorter, which reduces the heat pulse.
2) The Starship can cold-soak or barbecue roll to radiate away the heat pulse before beginning the actual EDL.
3) You also obviously get a chance to null out any guidance irregularities, allowing changes to both periapse altitude and inclination post-aerocapture.
4) The radius of curvature of the path requiring negative lift can be substantially greater, resulting in lower lift, which in turn reduces the amount of drag that's required.
It's #4 that I'm most curious about. (See attachment.) The deeper you can dip into the atmosphere before pulling out, the larger the radius of curvature of the path where substantial drag is produced. But that means that the Starship has to endure a very brief period of high drag, and therefore high peak heating. You obviously can't exceed a dynamic pressure that causes so high a peak heating that the tiles fail, but they're not going to soak at that temperature for very long. This is the kinda-in-between case between pure peak heating and total heat pulse.
Is there a pony in here somewhere? As always, the name of the game is the highest tolerable arrival v∞.
I wonder if since SS will be the first vehicle heading to mars with a reusable heat shield it will not do a capture burn, but instead only aerobrake.
IIRC all missions to mars have either 1) directly plunged in the atmosphere and EDLed, because they had ablative heat shields 2)did a capture burn aided by aerobraking
This maneuver would save a lot of dV, but the heating pulse and peak heating would need to be carefully studied. Also SS could aerobrake in a very elliptical orbit, but that orbit might be month long, and so they would probably want to get deeper in the atmosphere to scrub more velocity.
Thanks for the insight.
I wonder why such precise information on the state of the atmosphere is needed for aerocapture, that does not need to be extremely precise, but is not needed for standard EDL. The landing ellipse for Perseverance was about 7 miles, and that precision is not due to the sckycrane that only separates at 1.3 miles. Is the upper athmospere of mars so much turbolent and unpredictable and so an EDL is easier to perform accurately because it can go in the lower atmosphere?
Another example: the Orion capsule performs a skip reenty, on Earth. That meneuver is used to increase the accuracy of the landing, and is similar to aerocapture. Orion doesn't employ any probes sent in advance.
Going a tad in the OT direction: if the first mission plans on long distance excursions a minimal StarLink constellation makes sense. If low enough, the sats get good data for a broad picture of the state of the atmosphere. Not sure if this is good enough for an aerobreaking map. It's in the right direction.That technique is known as 'aerocapture', and the major barrier is knowing atmosphere state at time of entry in order to properly plot a trajectory to scrub just enough velocity to enter the target orbit (too much = early entry at an uncontrolled location on an undesired trajectory, too little = escape). Proposals to solve that problem include a swathe of probes sent ahead by a few hours to map multiple runs through the atmosphere to map density & temperature, and pre-placing Mars weather satellites to continuously measure the atmosphere in order to build and regularly update a volumetric atmospheric model.I think for thermal you have 2 primary constraints, not 1:
1. Heat pulse, i.e. the one you mentioned. This is the amount of energy which gets to your ship.
2. Peak heating. This is the maximum heating rate. Among other things this dictates skin temperature.
Ablative heat shields are primarily concerned with the first (1). But non-ablative ones are concerned with both (1 & 2), and it's easier to adjust them for 1 if a need arises (generally you improve the insulation layer). But adjusting for a higher peak heating (2) essentially means coming up with a different material which is not an easy change, and often means redoing your heatshield from scratch. And If you ramp peak heating just a tad too much we're simply out of known materials at all.
The thing about (2) is that it depends not just on velocity. It depends on deceleration as well. If you replace 2g braking with 4g braking you essentially doubled your peak heating.
At the same time you have likely reduced(!) heat pulse! This is counterintuitive, because kinetic energy to lose is the same regardless of how quickly you drop it. But the thing is, at certain point the more rarefied the ambient atmosphere the larger fraction of heat gets to the vehicle (and less is taken away by the ambient air). So when you pass entry interface heating initially grows much faster than deceleration. Just look at Shuttle reentry heating and deceleration profiles. Or some (SpaceX?) materials about Starship reentry. You're dropping speed slowly while heating is already high.
So if you have an ablative heatshield, you want to punch through the too thin air fast into high deceleration region. Total heat pulse is less that way, so you need less material to ablate. And you don't care that much about peak heating (within limits), as the temperature is primarily set by your ablative material's phase changes.
But if you have non-ablative heatshield, you prefer skidding on top of the atmosphere. The heat pulse is larger (often significantly), but you keep peak heating in check by keeping the whole kinetic energy drop rate in check. But if you have to generate more (negative) lift to hold onto a small low planet, you need to increase drag according to L:D ratio of your vehicle, which means higher deceleration which means higher kinetic energy drop rate and higher heating.
First, I never thanked you for this post. It's a very clear problem statement, and I refer back to it quite often.
So how do things change if Starship intends to aerocapture instead of doing a direct EDL? (This question applies for both Mars and Earth entry.)
I can think of a few of things:
1) You don't have to kill all the speed in a single direct EDL. You only need enough to get you captured into an eccentric orbit. That presumably makes the path through the atmosphere shorter, which reduces the heat pulse.
2) The Starship can cold-soak or barbecue roll to radiate away the heat pulse before beginning the actual EDL.
3) You also obviously get a chance to null out any guidance irregularities, allowing changes to both periapse altitude and inclination post-aerocapture.
4) The radius of curvature of the path requiring negative lift can be substantially greater, resulting in lower lift, which in turn reduces the amount of drag that's required.
It's #4 that I'm most curious about. (See attachment.) The deeper you can dip into the atmosphere before pulling out, the larger the radius of curvature of the path where substantial drag is produced. But that means that the Starship has to endure a very brief period of high drag, and therefore high peak heating. You obviously can't exceed a dynamic pressure that causes so high a peak heating that the tiles fail, but they're not going to soak at that temperature for very long. This is the kinda-in-between case between pure peak heating and total heat pulse.
Is there a pony in here somewhere? As always, the name of the game is the highest tolerable arrival v∞.
I wonder if since SS will be the first vehicle heading to mars with a reusable heat shield it will not do a capture burn, but instead only aerobrake.
IIRC all missions to mars have either 1) directly plunged in the atmosphere and EDLed, because they had ablative heat shields 2)did a capture burn aided by aerobraking
This maneuver would save a lot of dV, but the heating pulse and peak heating would need to be carefully studied. Also SS could aerobrake in a very elliptical orbit, but that orbit might be month long, and so they would probably want to get deeper in the atmosphere to scrub more velocity.
Going a tad in the OT direction: if the first mission plans on long distance excursions a minimal StarLink constellation makes sense. If low enough, the sats get good data for a broad picture of the state of the atmosphere. Not sure if this is good enough for an aerobreaking map. It's in the right direction.
If starship could produce enough lift there will be margin of error that could be fixed by manuvering.And maneuvering can get you cross-range. Nothing like some high hypersonic moves while making plasma. I'm a fan.
EDL spends a decent amount of time in the lower atmosphere, which is more 'stable' (e.g. for Mars a 1 Pa variance at 20km is a 1% change in pressure, a 1 Pa variance at 60km is a 100% variance in pressure), and for EDL a velocity residual has less of an effect on final trajectory than for aerocapture (an extra 100m/s may land you a few km down your landing ellipse, but an extra 100m/s after capture may be an escape trajectory or need 100m/s extra deltaV to correct).That technique is known as 'aerocapture', and the major barrier is knowing atmosphere state at time of entry in order to properly plot a trajectory to scrub just enough velocity to enter the target orbit (too much = early entry at an uncontrolled location on an undesired trajectory, too little = escape). Proposals to solve that problem include a swathe of probes sent ahead by a few hours to map multiple runs through the atmosphere to map density & temperature, and pre-placing Mars weather satellites to continuously measure the atmosphere in order to build and regularly update a volumetric atmospheric model.I think for thermal you have 2 primary constraints, not 1:
1. Heat pulse, i.e. the one you mentioned. This is the amount of energy which gets to your ship.
2. Peak heating. This is the maximum heating rate. Among other things this dictates skin temperature.
Ablative heat shields are primarily concerned with the first (1). But non-ablative ones are concerned with both (1 & 2), and it's easier to adjust them for 1 if a need arises (generally you improve the insulation layer). But adjusting for a higher peak heating (2) essentially means coming up with a different material which is not an easy change, and often means redoing your heatshield from scratch. And If you ramp peak heating just a tad too much we're simply out of known materials at all.
The thing about (2) is that it depends not just on velocity. It depends on deceleration as well. If you replace 2g braking with 4g braking you essentially doubled your peak heating.
At the same time you have likely reduced(!) heat pulse! This is counterintuitive, because kinetic energy to lose is the same regardless of how quickly you drop it. But the thing is, at certain point the more rarefied the ambient atmosphere the larger fraction of heat gets to the vehicle (and less is taken away by the ambient air). So when you pass entry interface heating initially grows much faster than deceleration. Just look at Shuttle reentry heating and deceleration profiles. Or some (SpaceX?) materials about Starship reentry. You're dropping speed slowly while heating is already high.
So if you have an ablative heatshield, you want to punch through the too thin air fast into high deceleration region. Total heat pulse is less that way, so you need less material to ablate. And you don't care that much about peak heating (within limits), as the temperature is primarily set by your ablative material's phase changes.
But if you have non-ablative heatshield, you prefer skidding on top of the atmosphere. The heat pulse is larger (often significantly), but you keep peak heating in check by keeping the whole kinetic energy drop rate in check. But if you have to generate more (negative) lift to hold onto a small low planet, you need to increase drag according to L:D ratio of your vehicle, which means higher deceleration which means higher kinetic energy drop rate and higher heating.
First, I never thanked you for this post. It's a very clear problem statement, and I refer back to it quite often.
So how do things change if Starship intends to aerocapture instead of doing a direct EDL? (This question applies for both Mars and Earth entry.)
I can think of a few of things:
1) You don't have to kill all the speed in a single direct EDL. You only need enough to get you captured into an eccentric orbit. That presumably makes the path through the atmosphere shorter, which reduces the heat pulse.
2) The Starship can cold-soak or barbecue roll to radiate away the heat pulse before beginning the actual EDL.
3) You also obviously get a chance to null out any guidance irregularities, allowing changes to both periapse altitude and inclination post-aerocapture.
4) The radius of curvature of the path requiring negative lift can be substantially greater, resulting in lower lift, which in turn reduces the amount of drag that's required.
It's #4 that I'm most curious about. (See attachment.) The deeper you can dip into the atmosphere before pulling out, the larger the radius of curvature of the path where substantial drag is produced. But that means that the Starship has to endure a very brief period of high drag, and therefore high peak heating. You obviously can't exceed a dynamic pressure that causes so high a peak heating that the tiles fail, but they're not going to soak at that temperature for very long. This is the kinda-in-between case between pure peak heating and total heat pulse.
Is there a pony in here somewhere? As always, the name of the game is the highest tolerable arrival v∞.
I wonder if since SS will be the first vehicle heading to mars with a reusable heat shield it will not do a capture burn, but instead only aerobrake.
IIRC all missions to mars have either 1) directly plunged in the atmosphere and EDLed, because they had ablative heat shields 2)did a capture burn aided by aerobraking
This maneuver would save a lot of dV, but the heating pulse and peak heating would need to be carefully studied. Also SS could aerobrake in a very elliptical orbit, but that orbit might be month long, and so they would probably want to get deeper in the atmosphere to scrub more velocity.
Thanks for the insight.
I wonder why such precise information on the state of the atmosphere is needed for aerocapture, that does not need to be extremely precise, but is not needed for standard EDL. The landing ellipse for Perseverance was about 7 miles, and that precision is not due to the sckycrane that only separates at 1.3 miles. Is the upper athmospere of mars so much turbolent and unpredictable and so an EDL is easier to perform accurately because it can go in the lower atmosphere?
Another example: the Orion capsule performs a skip reenty, on Earth. That meneuver is used to increase the accuracy of the landing, and is similar to aerocapture. Orion doesn't employ any probes sent in advance.
So that's how you remove a heat tile.
Heatshield performance at launch still looks like it needs relevant redesign. Note the tiles are primarily -but noy only- missing at welded sutures and flaps, and this happened during apparently nominal liftoff/first stage flight conditions (probably still subsonic?).I wouldn't put too much stock into missing tiles on this test. Doesn't sound like SpaceX really worried about them at all.
https://twitter.com/johnkrausphotos/status/1725877991312376190
https://twitter.com/rgvaerialphotos/status/1685091648991068160Wow imagine in-orbit EVA tile replacement. Gonna be heck of a debris cloud.QuoteSo that's how you remove a heat tile.
Heatshield performance at launch still looks like it needs relevant redesign. Note the tiles are primarily -but noy only- missing at welded sutures and flaps, and this happened during apparently nominal liftoff/first stage flight conditions (probably still subsonic?).I wouldn't put too much stock into missing tiles on this test. Doesn't sound like SpaceX really worried about them at all.
Heatshield performance at launch still looks like it needs relevant redesign. Note the tiles are primarily -but noy only- missing at welded sutures and flaps, and this happened during apparently nominal liftoff/first stage flight conditions (probably still subsonic?).I wouldn't put too much stock into missing tiles on this test. Doesn't sound like SpaceX really worried about them at all.
There was clearly some "worrying" since they went to the trouble of replacing some single lost ones, and R&R'ing quite some more due to unspecified reasons, plus performing lots of detailing work overall. If they expected dozens of them to fall right off at the beginning of flight, they would have dedicated much less time and effort.
I wish they were able to weld the studs and installing the tiles AFTER stacking the whole ship - much harder for the robots, but it is just an engineering problem. That would reduce the need to use glue as much. Automating the whole process would be a good goal.
That works for the cylindrical barrel welds but you also have the glued tiles on the highly curved parts of the hull (nose, flap edges and roots). It will be much harder to implement studded tiles there and it might be undesirable to start with - glued tiles can have the gaps filled much more easily which could be necessary where the tangential flow is high and the radius of curvature is small. As long as there are any glued tiles you need to solve it anyway.
I wish they were able to weld the studs and installing the tiles AFTER stacking the whole ship - much harder for the robots, but it is just an engineering problem. That would reduce the need to use glue as much. Automating the whole process would be a good goal.
YES!
Even using the stud installer for "gap" tiles would be another way. So pre tile sections and then once sections are welded together use a stud installer and install the gap tiles without glue.
True, but if fewer tiles have to be glued they can use heavier glues, tiles or backers to solve it for the remainder that really need glue.That works for the cylindrical barrel welds but you also have the glued tiles on the highly curved parts of the hull (nose, flap edges and roots). It will be much harder to implement studded tiles there and it might be undesirable to start with - glued tiles can have the gaps filled much more easily which could be necessary where the tangential flow is high and the radius of curvature is small. As long as there are any glued tiles you need to solve it anyway.
Even using the stud installer for "gap" tiles would be another way. So pre tile sections and then once sections are welded together use a stud installer and install the gap tiles without glue.
Any guesses about why many more tiles fell of from S25 than S24?Are we sure we know how many tiles fell from each?
Lower aero loads? Less precise installation?
Any guesses about why many more tiles fell of from S25 than S24?Are we sure we know how many tiles fell from each?
Lower aero loads? Less precise installation?
As for a guess why; IFT-1 had a very "gentle" (slow) start sequence that was aimed at reducing stress on the vehicle but ended up being much worse for the pad. IFT-2 started much more quickly, so likely more stress on the vehicle, possibly more vibrations and more tiles falling off. IFT-1 also lifted off with fewer Raptors lit and then lost raptors pretty quickly, so likely lower aero loads even at the low altitudes where we can see missing tile spots.
Do we know for a fact taht the liftoff profile of IFT-1 was deliberately a "very "gentle" (slow) start sequence that was aimed at reducing stress on the vehicle", and not a result of the early engine failures?Yes, I believe we do, although I don't have a citation handy. To be clear it wasn't the "liftoff profile" it was the startup sequence I am referring to.
Do away with those stupids SS clips, a thin smear of red silicone will be fine, also get rid of the fishing net type material beihnd the tiles.........problem solved. The SS clips also have stainless pieces embedded in the tile, get rid of it and will also save quite a bit of weight. No need for the clips its over enginered.Are you missing a sarcasm marker? A disproportionately large fraction of the tiles that fell off where glued...
Predicated a long time ago it would be problemmatic.
yes a stupid post on my behalf perhaps, also the temp of the SS will be problem for silicone,Yup you got it, problem solved.
heres a better idea:
velcro made from material that can handle the temps...........or similar to velcro, the SS clips are just not good.
heres pic of early in flight showing approx 100 cells gone........need to zoom to count them.
https://twitter.com/labpadre/status/1732419872079204851QuoteNew in the Ring Yard: A test barrel with what appears to be pins arranged for much smaller TPS tiles. Current theory is that these might be placed over the ship section seams instead of using glued-on tiles.
@CosmicalChief
@Ringwatchers
Cross posting this, correctly I hope. My thought was that the size of the TPS tiles being reduced also reduces several issues, such as strength of the tile, gap size and spacing, geometry in non-symmetrical areas of the vehicle, etc . Notice the frames already attached in the image, suggesting more frame and less tile body might also be beneficial. Obviously, far greater number of tiles to manufacture and mount, but I thought it interesting to consider the possibilities of this new approach.
https://twitter.com/labpadre/status/1732419872079204851https://twitter.com/labpadre/status/1732419872079204851QuoteNew in the Ring Yard: A test barrel with what appears to be pins arranged for much smaller TPS tiles. Current theory is that these might be placed over the ship section seams instead of using glued-on tiles.
@CosmicalChief
@Ringwatchers
I find it very interesting that even after all these years, the Thermal Protection System(TPS) remains such a challenge. Darned laws of thermodynamics, but I'm sure they'll get there.
"I've always considered the heat shield the single most critical element of Starship."The reason they have moving surfaces is to trim and steer during EDL so they will be moving. Starship is also, unlike capsules, at best marginally stable in several axis so it would most likely tumble without active control.
This has problem answered many times, so please delete if necessary:
I've always assumed that the heat shield of the moving surfaces to be the most critical element of Starship, especially the area where the surfaces hinge. Is it known if the moving surfaces with be locked into a particular orientation during entry, because if they are not then there are effectively many more heat shield and reentry heating profiles to be modelled and tested than if they are fixed for a period.
I find it very interesting that even after all these years, the Thermal Protection System(TPS) remains such a challenge. Darned laws of thermodynamics, but I'm sure they'll get there.But the TPS hasn't even got hot yet.
Short version: gluing glass to stainless steel is difficult.I find it very interesting that even after all these years, the Thermal Protection System(TPS) remains such a challenge. Darned laws of thermodynamics, but I'm sure they'll get there.But the TPS hasn't even got hot yet.
I don't get it.
well on most of the tiles they are machanically attached via the pins on the vehiclesShort version: gluing glass to stainless steel is difficult.I find it very interesting that even after all these years, the Thermal Protection System(TPS) remains such a challenge. Darned laws of thermodynamics, but I'm sure they'll get there.But the TPS hasn't even got hot yet.
I don't get it.
well on most of the tiles they are machanically attached via the pins on the vehiclesShort version: gluing glass to stainless steel is difficult.I find it very interesting that even after all these years, the Thermal Protection System(TPS) remains such a challenge. Darned laws of thermodynamics, but I'm sure they'll get there.But the TPS hasn't even got hot yet.
I don't get it.
It was the other way around on S25, most if the lost tiles looked to be glued.Which actually is a fair point. I don't think any of the glued tiles have come off, only the ones mechanically attached with pins.well on most of the tiles they are machanically attached via the pins on the vehiclesShort version: gluing glass to stainless steel is difficult.I find it very interesting that even after all these years, the Thermal Protection System(TPS) remains such a challenge. Darned laws of thermodynamics, but I'm sure they'll get there.But the TPS hasn't even got hot yet.
I don't get it.
Yes, but interestingly not in the nose?It was the other way around on S25, most if the lost tiles looked to be glued.Which actually is a fair point. I don't think any of the glued tiles have come off, only the ones mechanically attached with pins.well on most of the tiles they are machanically attached via the pins on the vehiclesShort version: gluing glass to stainless steel is difficult.I find it very interesting that even after all these years, the Thermal Protection System(TPS) remains such a challenge. Darned laws of thermodynamics, but I'm sure they'll get there.But the TPS hasn't even got hot yet.
I don't get it.
Hello, I’ve been finding tiles from SN25 in the Caribbean. I’ve also found others that I don’t think are from SN25, can anyone help me identify these? The heat-scorched one is really cool! Thanks
Here's my estimate of tile loss for IFT-3 during launch - 8 tiles.
Much improvement, and the distribution and location of these losses would not be mission critical
From Everyday Astronaut's "cosmic perspective" video.
I'm not familiar with the tides, currents, etc. So I am curious if it's possible that these could have washed up, after having detached themselves after the booster entered the water?
I'm not familiar with the tides, currents, etc. So I am curious if it's possible that these could have washed up, after having detached themselves after the booster entered the water?The booster doesn't have tiles though. So unless they are from a previous launch, they would have to come from the ship during launch.
Two intact (https://www.reddit.com/r/Damnthatsinteresting/comments/1bgxbwq/i_got_a_souvenir_from_the_3rd_spacex_starship/) tiles (https://www.reddit.com/r/SpaceXMasterrace/comments/1bevzly/got_mine_im_the_latest_happy_owner_of_a_fully/) were found after launch.Looking at the beautiful picture above, 4.jpeg, how did the tile come off the vehicle?
I appreciate the poetry butTwo intact (https://www.reddit.com/r/Damnthatsinteresting/comments/1bgxbwq/i_got_a_souvenir_from_the_3rd_spacex_starship/) tiles (https://www.reddit.com/r/SpaceXMasterrace/comments/1bevzly/got_mine_im_the_latest_happy_owner_of_a_fully/) were found after launch.Looking at the beautiful picture above, 4.jpeg, how did the tile come off the vehicle?
Ceramic cracked and failed? --- no, it's intact.
Adhesive failure? --- no, this isn't a glued tile.
Metal piece pullout? --- no, they're still in place.
Pin welded to vehicle failed? --- seems unlikely!
Design that still doesn't result in the tile clipping onto the pin with reasonably attentive installation? --- surely not!
Tile manufactured and thrown into the sea to confuse NSF readers? --- by nefarious forces?
Two intact (https://www.reddit.com/r/Damnthatsinteresting/comments/1bgxbwq/i_got_a_souvenir_from_the_3rd_spacex_starship/) tiles (https://www.reddit.com/r/SpaceXMasterrace/comments/1bevzly/got_mine_im_the_latest_happy_owner_of_a_fully/) were found after launch.Looking at the beautiful picture above, 4.jpeg, how did the tile come off the vehicle?
Ceramic cracked and failed? --- no, it's intact.
Adhesive failure? --- no, this isn't a glued tile.
Metal piece pullout? --- no, they're still in place.
Pin welded to vehicle failed? --- seems unlikely!
Design that still doesn't result in the tile clipping onto the pin with reasonably attentive installation? --- surely not!
Tile manufactured and thrown into the sea to confuse NSF readers? --- by nefarious forces?
So we're going with a failure of "reasonably attentive installation" + lack of QC....Two intact (https://www.reddit.com/r/Damnthatsinteresting/comments/1bgxbwq/i_got_a_souvenir_from_the_3rd_spacex_starship/) tiles (https://www.reddit.com/r/SpaceXMasterrace/comments/1bevzly/got_mine_im_the_latest_happy_owner_of_a_fully/) were found after launch.Looking at the beautiful picture above, 4.jpeg, how did the tile come off the vehicle?
...
Design that still doesn't result in the tile clipping onto the pin with reasonably attentive installation? --- surely not!
...
So these are easy fixes with a QA procedure that does vacuum pulls on the tiles - I seem to have read about that process being used on another vehicle somewhere?!
This is just a single tile. Likely pins were damaged or adhesive remains on the ship.4.jpg was obviously attached by pins, so no adhesive. Weak pins (realistically, weak welds) is consistent with what we see, but seems unlikely, I think SpaceX has got welding down pat.
I appreciate the poetry butTwo intact (https://www.reddit.com/r/Damnthatsinteresting/comments/1bgxbwq/i_got_a_souvenir_from_the_3rd_spacex_starship/) tiles (https://www.reddit.com/r/SpaceXMasterrace/comments/1bevzly/got_mine_im_the_latest_happy_owner_of_a_fully/) were found after launch.Looking at the beautiful picture above, 4.jpeg, how did the tile come off the vehicle?
Ceramic cracked and failed? --- no, it's intact.
Adhesive failure? --- no, this isn't a glued tile.
Metal piece pullout? --- no, they're still in place.
Pin welded to vehicle failed? --- seems unlikely!
Design that still doesn't result in the tile clipping onto the pin with reasonably attentive installation? --- surely not!
Tile manufactured and thrown into the sea to confuse NSF readers? --- by nefarious forces?
1. The first tile shows signs of being glued on despite being specifically designed to clip on
2. The second tile shows absolutely no sign of scarring or pullout damage around the slots - but it does have a series of dents around all three retention slots as if the end of a stud had been banging on the metal bracket with the vibration during launch - implying that the clips were not engaged on all three slots and friction from compression of the tile material and presumably positive airflow pressure was holding it on during launch until it wasn't
So these are easy fixes with a QA procedure that does vacuum pulls on the tiles - I seem to have read about that process being used on another vehicle somewhere?!
I thought the pin was welded to the ship. If the weld fails, the pin would still be attached to the tile, which is not the case here. It appears that the tile pulled cleanly away from all three pins, which means the press-fit detention clip system failed. That system needs some attention, either a more positive one-way clip configuration, or a fool-proof non-invasive inspection system, or both.This is just a single tile. Likely pins were damaged or adhesive remains on the ship.4.jpg was obviously attached by pins, so no adhesive. Weak pins (realistically, weak welds) is consistent with what we see, but seems unlikely, I think SpaceX has got welding down pat.
What is exact weight of complete hexagonal tile?
Two intact (https://www.reddit.com/r/Damnthatsinteresting/comments/1bgxbwq/i_got_a_souvenir_from_the_3rd_spacex_starship/) tiles (https://www.reddit.com/r/SpaceXMasterrace/comments/1bevzly/got_mine_im_the_latest_happy_owner_of_a_fully/) were found after launch.
What is exact weight of complete hexagonal tile?
A long time ago I pixel counted a tile as 24.35cm flat to flat(instead of point to point). Anybody know what the size is?
EDIT:
We heard in the broadcast that there are 18000 tiles. So 18000*.381kg=6.8t
I can't remember all the specifics, but I came up with 26 ounces a square foot using a complete tile I found, not including underlayment or pins.What's that in long tons per acre? :D