Starship heat shield

[SpaceManJoe]

Apparently the heat tiles on the Space Shuttle were not waterproof, I discovered this over on Reddit. This is what someone said on Reddit check it out  "The tiles on the shuttle orbiters were excellent sponges and absorbed/adsorbed moisture while at KSC. During each EDL the high temperature burned out the waterproofing chemical. That chemical, dimethyethyloxysilane (DMES), had to be reapplied before the next launch. DMES is toxic so the technicians had to wear hazmat suits and the building had to be evacuated during the rewaterproofing process that required about five days to complete. I don't see any evidence that SpaceX waterproofs the Starship tiles or needs to waterproof them.

AFAIK, SpaceX has not said anything about whether or not the Starship tiles are waterproofed as part of the production process."

The person who said this on Reddit claims to be a retired Space Shuttle tile engineer.

It rains a lot in Florida right? So you can't have a rapidly reusable launch system if after every single launch you have to re-waterproof the tiles in a process that takes 5 days to complete. So has SpaceX found a way around this problem?

Also, during the webcast they said the crunchwrap they put around each tile, they said it's called "Vulcan felt" did I spell that right? I bet you that felt would soak up water like a sponge if it rained.

So yeah ever since I learned that they had to re-waterproof the tiles on the Space Shuttle after every single launch in a process that took 5 days to complete, I can't stop thinking about it. Surely SpaceX has solved this problem using modern tech right?

So anyone know the answer here?

In fact I'm gonna say it, I bet the tiles and the Vulcan felt are not waterproof, I bet at least one, or both of them are not waterproof at all.

Which means Starship will never be "rapidly" reusable. And who knows, maybe it's impossible to make these tiles waterproof, they certainly couldn't do it back in the 1970s and maybe they still can't do it? Maybe it's impossible to make the felt waterproof as well?

I don't know why this question isn't being taken more seriously by the SpaceX community.

Also to the mods, I'm visiting this website on mobile, on Google Chrome, on my Android smartphone, whilst typing there's a really bad bug where the screen will keep jumping from top to bottom, It's been like this for a long time and I've finally had enough of it so now I'm saying something about it. It's why I typically visit this website on my PC instead of on my phone. There are a couple of bugs whilst typing on this website, on mobile, on an Android smartphone so please look into it?

[KilroySmith]

If I had to guess (and that's all I can do), I would guess that, coming out of the factory, the tiles are waterproof (or proofed).  I'm guessing that the top black layer is rainproof after coming out of the ovens; but that doesn't mean the tile can't absorb humidity.  I'm guessing that the various blankets and crunchwrap are waterproof out of the factory.

I'm not sure that it's a big problem for the ship.  Think about what their near-term plan is:
 - for Tankers, they'll be re-launching quickly (within hours) of landing.  As long as it isn't actively raining, they only need to avoid picking up too much weight via humidity for a couple of hours.
- For Cargo or Humans, they can use factory-fresh or refurbished ships, and trundle them out of the hangar to the launch site a couple hours before flight.  Once again, as long as it isn't actively raining, this should be do-able.   

I don't see them hitting high-rate reuse of anything other than tankers for quite some time.  And I'm sure they're working on something to allow them to get rid of the tiles eventually - they're heavy, and they're a pain in the patootie.

[SpaceManJoe]

It rains all the time in Florida, and it will randomly rain, this was a huge problem for the space shuttle tiles, it would just randomly rain in Florida and those tiles would soak up water.

There was a thread about this on X I read a while back, the guy said the space shuttle would land, and at this point the tiles were no longer waterproof, and so the space shuttle would land and it could just randomly rain before they had a chance to roll the space shuttle back inside, which means the tiles would soak up all the water and then they would have to go through and manually suck the water out of the tiles, and then go through the process of re-waterproofing the tiles before the next launch, so the space shuttle was absolutely not rapidly reusable at all.

I keep sounding the alarm over this, but I don't understand why the SpaceX community isn't talking about this more often!!!?

I bet you SpaceX has not solved this problem. They couldn't solve this back in the '70s and they probably still can't. Which means Starship will never ever be rapidly reusable.

So they need some kind of novel solution, I don't know, maybe Stoke Space has the solution for a rapidly reusable heat shield? I've had my eye on them.

[Stan-1967]

Apparently the heat tiles on the Space Shuttle were not waterproof, I discovered this over on Reddit.

You have made quite a few judgements and bold statements about SpaceX & reusable heat shields based on an admittedly very limited foundation of knowledge.  Good luck with that.

Successful organizations that push new boundaries have to learn how to solve first order problems, then move on to second, third, fourth, and on and on problems.  Time is good judge of that capability.  Readers here can judge for themselves which of our favorite launch providers seem to understand this strategy.

[Vultur]

I really doubt SpaceX has not thought about this. They surely know all the problems Shuttle reuse faced.

I keep sounding the alarm over this, but I don't understand why the SpaceX community isn't talking about this more often!!!?

I think we just don't know what solution they will use.

It might not be that huge an issue, what's the mass difference between wet tile and dry tile? Maybe the tiles just get wet and they absorb the mass penalty, and then vacuum dries them out so they're ok for reentry?

Or maybe they coat the tile with something waterproof. Who knows. There are possibilities, and given the heat shield experiments on the last two flights, SpaceX clearly haven't settled on a final heat shield.

If tile problems prove really unsolvable, they can always go back to transpiration cooling. That might be the best for really rapid smooth reuse.

[Eerie]

SpaceX regularly keep their Starships outside, near the ocean. I think they know what they are doing.

[InterestedEngineer]

I really doubt SpaceX has not thought about this. They surely know all the problems Shuttle reuse faced.

I keep sounding the alarm over this, but I don't understand why the SpaceX community isn't talking about this more often!!!?

I think we just don't know what solution they will use.

It might not be that huge an issue, what's the mass difference between wet tile and dry tile? Maybe the tiles just get wet and they absorb the mass penalty, and then vacuum dries them out so they're ok for reentry?

Or maybe they coat the tile with something waterproof. Who knows. There are possibilities, and given the heat shield experiments on the last two flights, SpaceX clearly haven't settled on a final heat shield.

If tile problems prove really unsolvable, they can always go back to transpiration cooling. That might be the best for really rapid smooth reuse.

The reasons the Space Shuttle was so paranoid about the tiles getting wet are:

1. Inability to handle boil-off robustly in the vacuum due to tightly packed tiles and using "only" glue instead of mechanical means of fastening tiles.
2.  Same problem dealing with freezing of tiles due to cryogenic fuel on the pad
3.  They had humans on board, they literally could not test with wet tiles to see what happens.
4.  Less margins on mass variability due to use of solid rockets (you can't vary the fuel mass in them)


Yet I think it was STS-2 (or 3?) that showed that if you face the tiles towards the sun for about an orbit the combination of heat and vacuum will completely dry out the tiles before re-entry.

So they only problem left is freezing (on the pad, due to cryogenic fuels) and added launch mass.

My guess is the added launch mass is small enough that it's a "don't care", they won't be launching close to mass margins except for fuel tankers.   And fuel tanker turnaround time should be quick, the occasional rain shower means you just load less fuel.  Late-binding fuel calculations are completely normal in the airline industry, it'll be normal here too.

As far as freezing, that's trivial to test in a lab.  My guess is with the mechanical attachment method and space between tiles it isn't a problem.

[thespacecow]

Interesting discussion of the heat shield issue on X:

From Dr. Phil Metzger: https://x.com/DrPhiltill/status/1978456710688776290

I don’t mean this as a negative, rhetorical question, but as a space technologist looking for innovation:  isn’t there a better way to do entry, so that spacecraft can be reusable with less maintenance?

Examples:

1) inflatable heat shields for higher lift, to extend entry over a longer time and reduce heating rate?

2) Better materials than silicon tiles? Maybe higher thermal conductivity for radiating heat away from the cooler parts of the vehicle?

3) Active cooling in the aeroframe designed for minimal mass and high reliability?

4) Spray-on ablative coating over the tiles?

5) Biologically inspired ideas like sweat glands in the tiles (like active ablation via phase change) or feathers (like thinner, overlapping tiles to create multiple layers so losing one doesn’t expose skin)?

6) Textured surfaces on the tiles to shape the boundary layer flow in the deepest sublayer to minimize heat transfer?

7) Other ideas?

Jon Edwards, SpaceX's VP of Falcon and Dragon replied: https://x.com/edwards345/status/1978516372859847126

Any thermal protection system (TPS) we consider must be capable of full and rapid reusability. “Reusable” and “fully & rapidly reusable” are not the same thing. The former typically leads to costly, time-consuming refurbishment cycles (think Space Shuttle), while the latter targets aircraft-like turnaround and per-flight economics — an entirely different design and operations paradigm.

To enable human civilization beyond Earth and the sci-fi future in space we all dream of, we must focus only on TPS concepts for which true full and rapid reuse is achievable. Some of the ideas mentioned could potentially work, while others likely will not (for example, spray-on ablatives).

As @elonmusk has said publicly, this remains one of the biggest challenges we’re tackling on the Starship program. Replicating the exact heating, dynamic pressure, and structural loading profiles for each tile across the entire vehicle is extremely difficult to achieve on the ground. That’s why we fly a wide variety of TPS experiments on every test flight.

All that said, please keep the good ideas coming!

[SpaceManJoe]

So my Dr. Phil Metzger thread here is totally different from @thespacecow's one above ⬆️

So Dr. Phil Metzger has an interesting thread on the space shuttle tiles on X, apparently he used to work on the space shuttle https://x.com/DrPhiltill/status/1801435436478304472 and he says that the tiles were mostly just empty space and so they couldn't fully encapsulate the tiles because they had to let the air escape when in space (there would be air inside the tiles), but this created a problem because it rains a lot in Florida and the tiles would absorb water like a sponge, if the tiles absorbed water then the shuttle would be too heavy to make it to orbit. So they couldn't fully encapsulate the tiles because they needed to be able to vent the air in space but this also allowed the tiles to soak up water when it rained.

So this is why on the top of each tile there would be a hole where they could squirt waterproofing chemicals into it, they had to do this to each tile. Oh and the waterproofing chemical would burn off during re-entry so they'd have to repeat this process after every single launch.

You can't have a rapidly reusable spacecraft, if after every single launch you have to re-waterproof the tiles in a process that takes 5 days to complete!

[SpaceManJoe]

There was a thread about this on X I read a while back, the guy said the space shuttle would land, and at this point the tiles were no longer waterproof

Yeah this thread right here https://x.com/DrPhiltill/status/1801435436478304472?t=SGKDgMKuQf6VNvqWCZ3XPg&s=19

Dr. Phil Metzger sure is a wealth of knowledge.

[Robotbeat]

5 day turnaround time isn’t that bad!

Note shuttle just never had the opportunity to fully streamline and solve these problems.

It only did 135 launches over 30 years, about 4-5 per year averaged over the whole period. Falcon 9 is 40 times that launch rate now. Starship is already at Shuttle’s rate & basically expendable, is still in test flight mode. Shuttle at its very peak did 9 missions per year, about a twentieth Falcon’s current rate.

I’m not pessimistic about Starship at all, even if Shuttle shows the best possible tile materials and construction. SpaceX will be able to iterate to a faster refurb time simply because of the higher launch and production rate. They can invest in tooling and automation to do the same kind of tasks Shuttle needed but at a faster rate and lower cost. And having a stainless structure makes Starship far safer even if the tiles are just as fragile as Shuttle’s.

BTW, the 4 tile clusters removed all over the belly of Starship are exactly the same size as the hole in Columbia’s wing, the professor just has a bad sense of scale (and an inability to approach the topic of Starship in completely good faith). The landings that Starship did with flap burn through show that even with pretty analogous damage, the stainless can withstand scenarios where shuttle’s aluminum airframe failed.

& Starship flying hundreds of times per year will provide ample opportunity to exceed STS TPS materials and construction, beyond just streamlined tooling and automation.

(In the meantime, I do think Stoke’s approach for solving this in a totally different way IS promising, although challenging to apply to Starship due to scale difference and not using hydrogen fuel.)

[envy887]

You can't have a rapidly reusable spacecraft, if after every single launch you have to re-waterproof the tiles in a process that takes 5 days to complete!

Ground processing isn't limited by mass. If necessary, you automate the process, and then run many machines in parallel. The limit is how fast you can inject waterproofing agent, which is maybe a minute.

Alternatively, if you can rollout, stack, and launch in an hour or two, you just wait until it's not raining. Shuttle had to live outside for weeks because it had hard infrastructure limits. Starship doesn't need to do that. It doesn't rain ALL the time, even in Florida.

[InterestedEngineer]

It still blows my mind that after all this discussion about water in tiles someone hasn't grabbed a tile from the Caribbean from flights 8 or 9, set it in some water, and stuck it in a freezer to see what happens.

[StraumliBlight]

The Flight 11 livestream had heat shield updates:

[21:45] Tile production already has surpassed the Space Shuttle program in 3 years.
[12:20] It takes ~40 hours to produce a tile from raw materials, currently producing ~1000 tiles a day.
[22:30] Factory is setup to produce enough tiles for 10 ships per month (7,000 tiles per day).
[22:50] Crunch wrap is called "Vulcan Felt".

[Tony- edit link to start at 15:30 - adjusted timestamps - used approved NSF rebroadcast stream by The Space Devs]

[InterestedEngineer]

https://youtube.com/watch?v=cYegpMZW2Vw#t=1304s

The Flight 11 livestream had heat shield updates:

[21:45] Tile production already has surpassed the Space Shuttle program in 3 years.
[12:20] It takes ~40 hours to produce a tile from raw materials, currently producing ~1000 tiles a day.
[22:30] Factory is setup to produce enough tiles for 10 ships per month (7,000 tiles per day).
[22:50] Crunch wrap is called "Vulcan Felt".

[Tony- edit link to start at 15:30 - adjusted timestamps - used approved NSF rebroadcast stream by The Space Devs]

When I Google `Vulcan Felt` I get a carbon based felt that is black.   not white.  (but it does match the needs of the crunch wrap as far as I can tell)

https://www.vulcanhz.com/en/product/carbon-fibre-soft-felt/70.html

[equiserre]

I think we have seen sort-of transpirational shielding in action.

In the two spots where they removed the tiles and the tank was breached, the holes were small enough to not blow up and not depressurize the whole tank. Autogenous pressurization was able to keep up with those leaks.

Maybe it´s because as soon as there was a hole, cryo fluid started gushing out, shielding the area and preventing further enlargement of the hole?

[Kazioo]

https://youtube.com/watch?v=cYegpMZW2Vw#t=1304s

The Flight 11 livestream had heat shield updates:

[21:45] Tile production already has surpassed the Space Shuttle program in 3 years.
[12:20] It takes ~40 hours to produce a tile from raw materials, currently producing ~1000 tiles a day.
[22:30] Factory is setup to produce enough tiles for 10 ships per month (7,000 tiles per day).
[22:50] Crunch wrap is called "Vulcan Felt".

[Tony- edit link to start at 15:30 - adjusted timestamps - used approved NSF rebroadcast stream by The Space Devs]

When I Google `Vulcan Felt` I get a carbon based felt that is black.   not white.  (but it does match the needs of the crunch wrap as far as I can tell)

https://www.vulcanhz.com/en/product/carbon-fibre-soft-felt/70.html

It could be this one:

https://www.vulcanshield.com/product/alumina-fiber-needled-blanket/

[catdlr]

It could be this one:

https://www.vulcanshield.com/product/alumina-fiber-needled-blanket/

Thanks for finding that. I saw that product discussed in another video, and I just couldn't find it.

[StraumliBlight]

Thanks for finding that. I saw that product discussed in another video, and I just couldn't find it.

The link was mentioned in the latest NSF recap video at 23:20.

[J.Burton]

Re-tiles on Starship
Just a light hearted look at the Starship heat shield/tile problem!
The only way I can see the tiles (Tiles! Don't they belong in the bathroom?) working effectively on Starship is to overlap them - like roof tiles/slates/shingles,
scales on a fish or even better on a dragon! (If only they where available! Fire proof - sure - the dragons wouldn't be too happy - Rockets dressed in animal skins!- all though they  would probably look rather smart!
I think they are too closely trying to following a fundamentally flawed - or at least an unreliable design from the shuttle era!
I'm not a big fan of glues/resins on flexible structures - too much fatigue!- and open glue lines - all that erosion - Yeah Right!
I consider plastic and glues/resins as such, as a bit of a bad* 'vampire' type material that doesn't fare too well when exposed to sunlight, weather and heat etc. *Even worse some of it  doesn't even  age very well! It'll kill you if not careful.
That crunch rap - if it's similar to the to the type of material I've used to make furnaces = rapidly wears away under a naked blowtorch (health hazard) it at least needs a harder surface - coating it with potassium/sodium silicate (water glass) helps but although being brittle the  solid cement type  works better! Using it as a 'backup' ablative layer rather than an insulative layer in my option is next to worthless! 
The expansion between extreme cold and heat must be quite considerable.
In essence the ship 'breathes' - tiles are good on very rigid structures - but in this case they need to be able to flex.
Is this sounding a bit George and the Dragon - just want to get the fiery beast home safe!
Overlapping  will of course make them very directionable and perhaps possibly very vulnerable, if one tile comes off it could pull many others off especially coming in arse first -  Direction and orientation of the ship and any flip manoeuvres/speed would be crucial -  Marilyn Munroe standing over that underground vent! As a  reference to roofing slates - they tend to fix the loose end down these days -  would that help! 
Then there is fur - Skins again! Just thinking of all the critters that swim and fly etc. and create a very fire proof version!
How about a woven carbon fibre merkin! (The Queens - sorry Kings guards headgear come to mind) - I should probably say a fur (artificial) coat. Then again - it is going to be used to cover it's 'vitals!'.
Carbon fibres advertised properties reports it to be reasonably flexible and light and very temperature resistant, you could stroke it in either or any direction.
Would/could it be enough in this form to insulate the Starship? How would you attach/manufacture it? Too expensive?
I haven't had much experience with this material - so how long would it last or how resilient it actually is, is probably open to debate.
What about  a bit of both! Shingles made of woven carbon fibre - no resins involved. Artificial  scales! Again orientation of each tile would need to be taken into account.
Now after that  - I keep getting this mental picture of an astronaut clamouring outside  with a mouthful of nails and a hammer replacing the tiles that blew off on the way up or 'Bones' in Startrek  fixing that tunnelling turtle with some fire cement!
There must be something better than rigid glued/pinned on flat tiles - One little raised edge! -  Would it be better to dome/dish/ profile/sharkskin the tiles?  I can't see them, ever, being reliable enough in their present form  to last - perhaps the only thing they have going for them is being easily and cheaply replaceable! Simplistic technology - although I must admit that's sometimes it's the best way! I'm all for easily replaceable/universal parts!
No doubt they have thought up every feasible solution for this problem - but have they? Being pedantic here! Use your imagination like a child! (I don't like 'out of the box')
Hopefully you get the gist!
This a very good discussion/debate topic! - Someone out there may - will? - have the answer to this conundrum no matter how ludicrous the idea may sound at first and it can come from the most unlikely of places!  SpaceX or someone should offer a prize, if they haven't already!
Summary - Starship heatshield - Bathroom Tiles - Dragon Scales - Carbon Fibre Fur Coat or something else?
Fanciable thinking - idiot - very likely!
What do you reckon?