Starship heat shield

[DanClemmensen]

Maybe SpaceX has come up with some super clever ingenious workaround like that. I wish someone would just outright ask Elon Musk about it?

EM has said multiple times that the heat shield is among the hardest nuts to crack in full reusability.  If they've made progress on that tech, it's going to be among the most proprietary data they have, and they won't be sharing it publicly.

They may choose to hide the details, but they will demonstrate its existence or non-existence within a year, and if tile adhesion is imperfect or if a Ship RUDs on ascent or descent they will also be providing samples to the public. My guess: it's hard, and they think they have solved it but they are not sure.

[SpaceManJoe]

Are we sure that waterproofing is strictly needed?

Phil Metzger said he briefly worked on heat tile tech 20 years ago and at the time there was no known material that DID NOT need to be waterproofed. He said that 20 years ago when he worked on heat tile tech, they couldn't solve this problem 20 years ago, they couldn't solve this problem 50 years ago.

So the question is, has SpaceX done the impossible? Has SpaceX found a way?

Ever since I found out the heat tiles on the space shuttle had to be waterproofed after every single launch, and that was just the way it was cause it was too hard of a problem to solve, I can't stop thinking about it, I can't stop wondering, has SpaceX finally solved this problem?

And Phil Metzger is saying they still couldn't solve this problem 20 years ago.

And I also really wanted to sound the alarm over this and make you all aware of this, which I think I've successfully done at this point.

Thank you for your time.

[Vultur]

Are we sure that waterproofing is strictly needed?

Phil Metzger said he briefly worked on heat tile tech 20 years ago and at the time there was no known material that DID NOT need to be waterproofed.

I have no doubt there. My question is: what happens if you just don't waterproof?

If it's just "you're carrying the extra weight of the water", that would certainly have been unacceptable 20 years ago, but no one was thinking of Starship then. With Starship's fairly ridiculous size by historical standards, it may be acceptable.

Now, if water getting in the tile destroys the tile somehow, that's different.

[Vettedrmr]

I have no doubt there. My question is: what happens if you just don't waterproof?

If it's just "you're carrying the extra weight of the water", that would certainly have been unacceptable 20 years ago, but no one was thinking of Starship then. With Starship's fairly ridiculous size by historical standards, it may be acceptable.

Now, if water getting in the tile destroys the tile somehow, that's different.

I think it's the absorbed water freezing when cryo is added to the mix and cracking the tile.  SX's "belts and suspenders" approach of having the tiles, backed up by the ablative felt, backed up by the strength of the SS skin, could manage this issue of damaged tiles.  At least until they find a better way.

[Slarty1080]

I have no doubt there. My question is: what happens if you just don't waterproof?

If it's just "you're carrying the extra weight of the water", that would certainly have been unacceptable 20 years ago, but no one was thinking of Starship then. With Starship's fairly ridiculous size by historical standards, it may be acceptable.

Now, if water getting in the tile destroys the tile somehow, that's different.

I think it's the absorbed water freezing when cryo is added to the mix and cracking the tile.  SX's "belts and suspenders" approach of having the tiles, backed up by the ablative felt, backed up by the strength of the SS skin, could manage this issue of damaged tiles.  At least until they find a better way.

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

[Twark_Main]

I have no doubt there. My question is: what happens if you just don't waterproof?

If it's just "you're carrying the extra weight of the water", that would certainly have been unacceptable 20 years ago, but no one was thinking of Starship then. With Starship's fairly ridiculous size by historical standards, it may be acceptable.

Now, if water getting in the tile destroys the tile somehow, that's different.

I think it's the absorbed water freezing when cryo is added to the mix and cracking the tile.  SX's "belts and suspenders" approach of having the tiles, backed up by the ablative felt, backed up by the strength of the SS skin, could manage this issue of damaged tiles.  At least until they find a better way.

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

"Raincoat" clearly.   

They can re-use the same technology as the disappearing curtain in the Dragon 2 reveal. An automatic zipper actuates, the raincoat falls, and it's pulled into hardened blast shelters just before launch. 

[SpaceManJoe]

Are we sure that waterproofing is strictly needed?

Phil Metzger said he briefly worked on heat tile tech 20 years ago and at the time there was no known material that DID NOT need to be waterproofed.

I have no doubt there. My question is: what happens if you just don't waterproof?

If it's just "you're carrying the extra weight of the water", that would certainly have been unacceptable 20 years ago, but no one was thinking of Starship then. With Starship's fairly ridiculous size by historical standards, it may be acceptable.

Now, if water getting in the tile destroys the tile somehow, that's different.

READ THIS THREAD! The answer to your question is in this thread https://x.com/DrPhiltill/status/1801435436478304472?t=SGKDgMKuQf6VNvqWCZ3XPg&s=19

[rsdavis9]

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?

[OTV Booster]

I have no doubt there. My question is: what happens if you just don't waterproof?

If it's just "you're carrying the extra weight of the water", that would certainly have been unacceptable 20 years ago, but no one was thinking of Starship then. With Starship's fairly ridiculous size by historical standards, it may be acceptable.

Now, if water getting in the tile destroys the tile somehow, that's different.

I think it's the absorbed water freezing when cryo is added to the mix and cracking the tile.  SX's "belts and suspenders" approach of having the tiles, backed up by the ablative felt, backed up by the strength of the SS skin, could manage this issue of damaged tiles.  At least until they find a better way.

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

I've great hope for rapid booster turnaround but little hope for rapid ship turnaround in the near future. This means that for rapid flight turnaround there needs to be a pipeline of ships, probably mostly tankers, waiting for stacking.


On orbit storage probably needs a depot shepherd for keep alive duty so forget that for now. Store em on the ground and in the weather. Build a megabay or gigabay sized facility for tile referb and storage. Use an enclosed bay with an adjacent bakery for the next ship in line and bake it out with waste heat from the bakery.

[tenkendojo]

Are we sure that waterproofing is strictly needed?

Phil Metzger said he briefly worked on heat tile tech 20 years ago and at the time there was no known material that DID NOT need to be waterproofed.

I have no doubt there. My question is: what happens if you just don't waterproof?

If it's just "you're carrying the extra weight of the water", that would certainly have been unacceptable 20 years ago, but no one was thinking of Starship then. With Starship's fairly ridiculous size by historical standards, it may be acceptable.

Now, if water getting in the tile destroys the tile somehow, that's different.

I think you might have underestimated how much water these tiles could absorb. Silica glass fibres are inherently hydrophilic. Those oxygen atoms on SiO2 surface just love to form hydrogen bonds with water. It's the same reason makes our bath sponge (mostly made of cellulouse fibres) hydrophilic as well. Whereas a typical bath sponge is around 70% air by volume, TPS tiles are >90% air by volume. In this regard heat tiles are essentially bricks of Perlitehttps://www.perlite.org/the-water-holding-capacity-of-perlite/  After being exposed to a typical Gulf Coast rainstorm unprotected, the Starship would be great for hydroponics horticulture but it's definitely not going to orbit.

[steveleach]

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.

[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.

[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.

[InterestedEngineer]

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.

[Twark_Main]

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.

[rsdavis9]

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.

[CMac]

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.

[J.Burton]

Do you get the feeling the heat shield tiles need to be overlapped like scales  to cover that soft underbelly. A silicate version of keratin in an integumentary system! Just a thought! Look at the implications of using such a system as a reference to solve the problem!

[OTV Booster]

Do you get the feeling the heat shield tiles need to be overlapped like scales  to cover that soft underbelly. A silicate version of keratin in an integumentary system! Just a thought! Look at the implications of using such a system as a reference to solve the problem!

This idea gets thrown out periodically. IIRC there are two objections.


First, it would mildly impact installation. Related and more serious, it would radically impact spot repairs.


Second, it presupposes that the airflow will always be from nose to tail. There is a stagnation point just below the nose that shifts with EDL attitude and velocity. Gas flow above this point flows away from the tail. Then there is the landing flip. The stagnation point shifts lower as the flip progresses resulting in airflow trying to pry off yet more tiles. Once the flip is complete all airflow is from aft to nose. The gas flow on the fins is all over the place.


None of this is IMO a total deal killer but it does add complications that aren't  justified at this point. Sure would look cool though.


BTW, welcome to the fun house.

[rfdesigner]

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.

I spent a career in Electronics R&D.   There is a persistant issue with water absorbtion in chips that then need to be infrared soldered to circuit boards.  The rapid heating can fracture chips, on a per chip basis it's low liklihood, but on a complex board with a lot of chips it can become a serious problem simply because the board can pass all tests then fail in the field.

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.

Additionally ships don't need to be rained on for water absortion to be a problem.  I'm not familiar with the water absorbtion of the ship tiles, but going from other posts above I would expect tiles to absorb moisture from humid air, even if they never get rained on, that's the problem we have in electronics.  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.

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