Starship heat shield

[Twark_Main]

could you vacuum pack the ship in plastic to quicly outgas water? Sit it on a mount with a sealing ring flange to set the plastic jacket into. Vacuum pump underneath the mount.

No.

...

In electronics we bake the chips typically for 24 hours at a low temperature (relative to soldering) to remove moisture, but if the tiles have larger pores they may allow the moisture to be expelled at a more rapid rate

The idea is to promote evaporation by pressure swing, not temperature swing. You reduce the pressure so the boiling point is below the ambient temperature. Obviously you reduce pressure slowly so it doesn't all boil at once and crack the tiles.

In eletronics once your chips are dry you have to vacuum pack and hermetically seal them, add dessicant sachets and humitiy strips.  There's no way to do that with something as large as Starship.

Different goals (hermetic sealing vs vacuum drying).

[InterestedEngineer]

could you vacuum pack the ship in plastic to quicly outgas water? Sit it on a mount with a sealing ring flange to set the plastic jacket into. Vacuum pump underneath the mount.

 I do wonder if the re-entry profile is part of the picture here.  In electronics we bake the chips typically for 24 hours at a low temperature (relative to soldering) to remove moisture, but if the tiles have larger pores they may allow the moisture to be expelled at a more rapid rate, and Starship does seem to take a longer shallower re-entry profile than some missions.

Re-entry isn't the problem.  You bake the tiles in the sun every orbit, and you have a vacuum.  No moisture is going to survive more than an orbit or two.

The main problem is probably water freezing and expanding during cryogenic fuel loading on the pad.  A secondary problem might be too rapid a transition to vacuum at launch (about 45 seconds or so).

I do wonder if mounting tiles on pins alleviates some of the problem, allowing the rear of the tile to outgas where a bonded tile might otherwise need further protection, we'll see if they do something around the hinges and flat leading edges where they seem to have bonded tiles

That's a good point, they still have some bonded tiles.

But an important point is those tiles are on the flaperons or not on the cryogenic fuel tanks directly - so they don't freeze (I think).  That leaves the secondary outgassing during rapid ascent to orbit.  It's likely that the spacing between them allows this to happen without damage.

[CMac]

Ah, I see, main concern is frosting at fuel loading time?
I assume that's going to happen even for hydrophobic surfaces, if at a lower rate of freezing.

I wonder how it would be if you had very thin walled (light) steel tubing running along and welded to the body with the tubing having perforations. You seep N₂ out from the tubing, underneath the tiles. With sufficient flow, moisture wouldn't enter between the tiles or would be limited. It would be like a ventilation system. Tubing could be run around in the circumeral direction connected into a verticle manifold tube. The weight penalty could be quite small. Perhaps it could be done with 100 kg of tubing? It sounds a lot like transpiration cooling system but it is gas flow.

[OTV Booster]

Ah, I see, main concern is frosting at fuel loading time?
I assume that's going to happen even for hydrophobic surfaces, if at a lower rate of freezing.

I wonder how it would be if you had very thin walled (light) steel tubing running along and welded to the body with the tubing having perforations. You seep N₂ out from the tubing, underneath the tiles. With sufficient flow, moisture wouldn't enter between the tiles or would be limited. It would be like a ventilation system. Tubing could be run around in the circumeral direction connected into a verticle manifold tube. The weight penalty could be quite small. Perhaps it could be done with 100 kg of tubing? It sounds a lot like transpiration cooling system but it is gas flow.

Ooh. That would be some seriously fiddly fabrication. To ensure something close to a uniform flow rate from the holes one or some combination of the following needed:
- a complex, possibly fractal distribution manifold
- tapered tubing
- a hole size gradient down the length of the delivery tube.


From the techs point of view it's delicate tubing (it has to be delicate at that weight) close to where a bit of heel of the hand persuasion can be expected.


The physics probably works out but it would be expensive, probably more than 100kg and a pain to work with.

[Slarty1080]

Odd thought, but could they just cover starship with a huge waterproof er hood / sock (cough ...or something). Just to keep the rain out? A bit of a pain, but maybe easier than other options. SpaceX are not adverse to trying unusual things to get them out of a difficult spot - like feeding the autogenous pressurization system with oxygen side turbine exhaust

So OT but do we know that R3 is still doing the "dirty" (water ice and co2 ice) oxygen pressurization?

Why?

Less mass is less mass. If the filters have less mass (per engine) than adding a huge surface area heat exchanger (per engine) then that's the only thing that matters.

Well one thing. Water ice floats in LOX and co2 ice sinks. When it comes time to refuel for another booster launch in 1 hour has the co2 sublimed? Has the water ice melted? Same thing in space newly arrived to orbit ship wants to refuel at depot. Does the ice in its tanks matter.

I asked about the filtration here:
https://forum.nasaspaceflight.com/index.php?topic=63447.msg2727183#msg2727183
V3 was expected not to require filters but nobody knows for sure.

It shouldn't be that difficult to pressurize the tank with hot nitrogen and vent / drain it

[OTV Booster]

Odd thought, but could they just cover starship with a huge waterproof er hood / sock (cough ...or something). Just to keep the rain out? A bit of a pain, but maybe easier than other options. SpaceX are not adverse to trying unusual things to get them out of a difficult spot - like feeding the autogenous pressurization system with oxygen side turbine exhaust

So OT but do we know that R3 is still doing the "dirty" (water ice and co2 ice) oxygen pressurization?

Why?

Less mass is less mass. If the filters have less mass (per engine) than adding a huge surface area heat exchanger (per engine) then that's the only thing that matters.

Well one thing. Water ice floats in LOX and co2 ice sinks. When it comes time to refuel for another booster launch in 1 hour has the co2 sublimed? Has the water ice melted? Same thing in space newly arrived to orbit ship wants to refuel at depot. Does the ice in its tanks matter.

I asked about the filtration here:
https://forum.nasaspaceflight.com/index.php?topic=63447.msg2727183#msg2727183
V3 was expected not to require filters but nobody knows for sure.

It shouldn't be that difficult to pressurize the tank with hot nitrogen and vent / drain it

I'm a skeptic on fast turnaround for the ship in the next few years but bullish on the booster.


Being realistic, the most intense launch tempo in the near future will be tankers and each OLM will only launch every 24 hours to sync up with a depot. This would leave plenty of time for an N2 purge.


Still, it feels like a bandaid for a problem that shouldn't be there.

[eriblo]

I'm inclined to assume that if SpaceX were actually concerned about the tiles getting wet then they will have made sure some of the flight 10 or 11 tiles were soaked, and then monitored them during the flight. Maybe they are still concerned after that, maybe not.

If it is actually a problem then they may need to move early ships indoors if there is going to be heavy rain. Maybe they'll even have to replace the tiles if something goes wrong and a ship gets caught out in heavy rain for a significant period.

I would think that instead of replace tiles that leaving it in a protected storage for weeks would dry it out. We up here in the north regularly dry out cord wood to heat with. So cellulose in large chunks 6-12 inches dries out in months.

the whole story of some moisture vulnerability of SpaceX tiles is way overblown. NASA did quite a bit successful work on tiles in post (and late) Shuttle times. It is quite "easy" to dig some obvious names and works. Really really obvous names and tech.

Might you perchance provide a few example search terms or resources? The reason we discuss it is because every spaceflight nerd and their dog knows it was a problem throughout the space shuttle program but at least I have obviously missed the easily available obvious information and have yet to see anything concrete like patents/papers or definitive statements by people directly involved in relevant programs. For example we know that Dream Chaser uses a lot of the lessons learned - and will still require rewaterproofing after each flight.

Since SpaceX like to point out:

Indeed, Starship's heat shield is the lynch pin to full and rapid reusability. We can't launch, land, refuel, and launch again if we have to spend months refurbishing the heat shield after every launch like they did in the space shuttle program.

I can certainly understand those who question the complete lack of any statements from SpaceX regarding one of the major factors in that refurbishment, especially if it is a completely solved problem.

It might be more understandable if they have a highly proprietary solution that they are fairly sure will work eventually, but you don't have to be super pessimistic to at least acknowledge that there is a sliding slope towards "it's on the To Do list and well surely have it figured out by the time we need it, somehow".

[eriblo]

I'm inclined to assume that if SpaceX were actually concerned about the tiles getting wet then they will have made sure some of the flight 10 or 11 tiles were soaked, and then monitored them during the flight. Maybe they are still concerned after that, maybe not.

If it is actually a problem then they may need to move early ships indoors if there is going to be heavy rain. Maybe they'll even have to replace the tiles if something goes wrong and a ship gets caught out in heavy rain for a significant period.

I would think that instead of replace tiles that leaving it in a protected storage for weeks would dry it out. We up here in the north regularly dry out cord wood to heat with. So cellulose in large chunks 6-12 inches dries out in months.

the whole story of some moisture vulnerability of SpaceX tiles is way overblown. NASA did quite a bit successful work on tiles in post (and late) Shuttle times. It is quite "easy" to dig some obvious names and works. Really really obvous names and tech.

Here's some of that research.

1. Detecting water remotely:

https://www.researchgate.net/publication/233587042_A_Capacitive_Sensor_for_Detection_of_Water_in_the_NASA_Space_Shuttle_Orbiter_Tiles

2.  The surface is no longer porous, so water has a much harder time penetrating

https://ntrs.nasa.gov/citations/19920006808
https://ntrs.nasa.gov/citations/20240002574
https://ntrs.nasa.gov/citations/20080018811


3. Waterproofing chemicals were surviving for more re-entries by the end of the shuttle program:

https://ntrs.nasa.gov/citations/19990110102


4. The attachment system for Starship reduces damage from outgassing and freezing because it's not tight tolerance and glued like the Shuttle.

While helpful, these seem to be far from examples of improvements that enable the ideal minimum work rapid reusability.

1. Simplifies water detection so you know when you can start rewaterproofing the tiles.

2. Slightly confusing, since it states that the coating is impervious to water but that the increased porosity helps with chemical penetration during the rewaterproofing process. TUFI still needs rewaterproofing (even if the coating is completely waterproof it can still get into the tiles through the uncoated sides) as does presumably the TUFI portions of TUFROC (which is not relevant to the Starship tiles anyway).

3. Improvements regarding the instrumentation used to measure the vapors released during rewaterproofing.

4. While it keeps intact tiles from falling of it should not matter much for the freezing/boiling related failures of the bulk tile material (i.e. tiles flaking off parallel to the surface and leaving the back side happily glued to the skin).

[rsdavis9]

I'm inclined to assume that if SpaceX were actually concerned about the tiles getting wet then they will have made sure some of the flight 10 or 11 tiles were soaked, and then monitored them during the flight. Maybe they are still concerned after that, maybe not.

If it is actually a problem then they may need to move early ships indoors if there is going to be heavy rain. Maybe they'll even have to replace the tiles if something goes wrong and a ship gets caught out in heavy rain for a significant period.

I would think that instead of replace tiles that leaving it in a protected storage for weeks would dry it out. We up here in the north regularly dry out cord wood to heat with. So cellulose in large chunks 6-12 inches dries out in months.

the whole story of some moisture vulnerability of SpaceX tiles is way overblown. NASA did quite a bit successful work on tiles in post (and late) Shuttle times. It is quite "easy" to dig some obvious names and works. Really really obvous names and tech.

Here's some of that research.

1. Detecting water remotely:

https://www.researchgate.net/publication/233587042_A_Capacitive_Sensor_for_Detection_of_Water_in_the_NASA_Space_Shuttle_Orbiter_Tiles

2.  The surface is no longer porous, so water has a much harder time penetrating

https://ntrs.nasa.gov/citations/19920006808
https://ntrs.nasa.gov/citations/20240002574
https://ntrs.nasa.gov/citations/20080018811


3. Waterproofing chemicals were surviving for more re-entries by the end of the shuttle program:

https://ntrs.nasa.gov/citations/19990110102


4. The attachment system for Starship reduces damage from outgassing and freezing because it's not tight tolerance and glued like the Shuttle.

While helpful, these seem to be far from examples of improvements that enable the ideal minimum work rapid reusability.

1. Simplifies water detection so you know when you can start rewaterproofing the tiles.

2. Slightly confusing, since it states that the coating is impervious to water but that the increased porosity helps with chemical penetration during the rewaterproofing process. TUFI still needs rewaterproofing (even if the coating is completely waterproof it can still get into the tiles through the uncoated sides) as does presumably the TUFI portions of TUFROC (which is not relevant to the Starship tiles anyway).

3. Improvements regarding the instrumentation used to measure the vapors released during rewaterproofing.

4. While it keeps intact tiles from falling of it should not matter much for the freezing/boiling related failures of the bulk tile material (i.e. tiles flaking off parallel to the surface and leaving the back side happily glued to the skin).

Well we do know one thing. The current tiles work with moisture from rain etcetera and cryogenic propellants and ascent and descent. Whether this is a one time only thing or more than one we don't know yet. In other words does their waterproofing burn off from reentry and then the next flight will get so much water under the tiles and then get ice popping off the tiles.

I'm betting it wont require re-waterproofing. I am not an expert. I am guessing. If nothing else they can try to protect the ship from rain between flights.

BTW does anybody have a quick way to see which tiles are pinned and which are glued? For example on the nose cone you can see the pins stop before they get to the top. I don't have a good pic of this. Does anybody else? I mostly want to see if they are increasing the pinned tiles.
 

[dondar]

I'm inclined to assume that if SpaceX were actually concerned about the tiles getting wet then they will have made sure some of the flight 10 or 11 tiles were soaked, and then monitored them during the flight. Maybe they are still concerned after that, maybe not.

If it is actually a problem then they may need to move early ships indoors if there is going to be heavy rain. Maybe they'll even have to replace the tiles if something goes wrong and a ship gets caught out in heavy rain for a significant period.

I would think that instead of replace tiles that leaving it in a protected storage for weeks would dry it out. We up here in the north regularly dry out cord wood to heat with. So cellulose in large chunks 6-12 inches dries out in months.

the whole story of some moisture vulnerability of SpaceX tiles is way overblown. NASA did quite a bit successful work on tiles in post (and late) Shuttle times. It is quite "easy" to dig some obvious names and works. Really really obvous names and tech.

Might you perchance provide a few example search terms or resources? The reason we discuss it is because every spaceflight nerd and their dog knows it was a problem throughout the space shuttle program but at least I have obviously missed the easily available obvious information and have yet to see anything concrete like patents/papers or definitive statements by people directly involved in relevant programs. For example we know that Dream Chaser uses a lot of the lessons learned - and will still require rewaterproofing after each flight.

first thing first.
Philip T. Metzger is an astrologist by vocation and was working all his life in Florida university (Kennedy center), if he was ever involved in tiles anything he would be involved only in administrator position.
 NASA tiles research was concentrated in Ames. (san jose, santa cruz uni).  Since nobody else pointed anything usefull I have no desire to be the first one. Keep on digging, it is useful if you want to learn anything.

What DreamChaser is supposes to do is actually irrelevant. It is pure power-point project designed to consume some old "completed" NASA research (think Axiom) and to provide retirement positions for relevant personnel. What they will do in the end if they ever accidentally end with factual hardware will be very different from their plans or claims.

[DanClemmensen]

first thing first.
Philip T. Metzger is an astrologist by vocation ...

That explains a great deal. Which Zodiac sign was the born under?

[Vettedrmr]

Philip T. Metzger is an astrologist by vocation

Best I could find, I'd characterize his vocation as "planetary physicist".

[InterestedEngineer]

I've completely lost track - is Metgzer brought up here because he's predicting doom and gloom on water & tiles, or is it something else?

[eriblo]

I've completely lost track - is Metgzer brought up here because he's predicting doom and gloom on water & tiles, or is it something else?

I don't know in this case specifically but it's usually because he is a NASA associated scientist who has a lot of interesting things to say on X so a lot of people have heard about him. He has worked (briefly) on the shuttle tiles and did a fairly comprehensive thread ~3 years ago specifically about the waterproofing problem but has as recently as November clarified that he does not know if SpaceX has a solution for it or any ideas about how it could be done.

[clongton]

first thing first.
Philip T. Metzger is an astrologist <snip>

Philip T. Metzger is NOT an astrologist. He is an American planetary physicist with the Florida Space Institute. Mr. Metzger’s work is in planetary science and space engineering, grounded in physics, geology, and space technology — not astrology.

[dondar]

Philip T. Metzger is an astrologist by vocation

Best I could find, I'd characterize his vocation as "planetary physicist".

same thing. Still good (and regrettably a valid) joke about astronomers.
Explore some history:
https://en.wikipedia.org/wiki/Observations_and_explorations_of_Venus.
Current developments (especially in most hot topics) are not any better.

My point was that he is not equipped technically to judge anything in physically intensive subjects.
Jabb is just part of "bad grammar".

[spacenut]

I've always thought the best idea for a heat shield is what Phillip Bono came up with in the 1960's using a large capsule shaped spacecraft with a large plug nozzle circular engine around the base.  Or, what Stoke Space is developing.  Easier return from space.  SpaceX could still do this using say a 12m diameter large capsule shaped spacecraft on top of their booster.  Stretch the booster and stage higher to get a similar payload that could be attached to the top of the capsule.  Enough room near the top of the capsule could be used for a small crew and then attach a 9m fairing on top for payload, and or docking equipment for crew transfer and for fuel connections for refueling. 

[eriblo]

I've always thought the best idea for a heat shield is what Phillip Bono came up with in the 1960's using a large capsule shaped spacecraft with a large plug nozzle circular engine around the base.  Or, what Stoke Space is developing.  Easier return from space.  SpaceX could still do this using say a 12m diameter large capsule shaped spacecraft on top of their booster.  Stretch the booster and stage higher to get a similar payload that could be attached to the top of the capsule.  Enough room near the top of the capsule could be used for a small crew and then attach a 9m fairing on top for payload, and or docking equipment for crew transfer and for fuel connections for refueling.

That would be harder to return as the design runs into square-cubed problems, especially if you do not need big fluffy hydrogen tanks. To get the same cross section for reentry you need a 24 m diameter capsule (and more for future versions).

[Action]

I've always thought the best idea for a heat shield is what Phillip Bono came up with in the 1960's using a large capsule shaped spacecraft with a large plug nozzle circular engine around the base.  Or, what Stoke Space is developing.  Easier return from space.  SpaceX could still do this using say a 12m diameter large capsule shaped spacecraft on top of their booster.  Stretch the booster and stage higher to get a similar payload that could be attached to the top of the capsule.  Enough room near the top of the capsule could be used for a small crew and then attach a 9m fairing on top for payload, and or docking equipment for crew transfer and for fuel connections for refueling.

That would be harder to return as the design runs into square-cubed problems, especially if you do not need big fluffy hydrogen tanks. To get the same cross section for reentry you need a 24 m diameter capsule (and more for future versions).

What exactly would be the problem with a 24 meter diameter capsule?  It's a more efficient shape in almost all respects.  For example, it ought to be quite a bit lighter. 

Furthermore, you don't actually need to match area, because the capsule base is a much better shape for reentry - it can have a much higher radius of curvature than the radius of the long, thin cylinder Starship presently uses, so it has more drag per unit area and keeps the hot shock farther from the reentry vehicle.

This ship has sailed, but it seems like this configuration choice is one of SpaceX's few big errors with respect to Starship.  The other being ceramic tiles, but they kind of go hand in hand.

[SpaceLizard]

What exactly would be the problem with a 24 meter diameter capsule?

1. That it would be extremely difficult and cumbersome to transport without completely redesigning a lot of essential infrastructure.
2. That you would require a similarly bloated and difficult to transport launch vehicle.
3. ?
4. ?