…remains a problem, even with the recent successful flight.
This is the kind of technology that (as it did as the NACA, before it became NASA) that NASA should have been prioritizing for decades. But it was more important to build a giant expendable rocket without a design reference mission.
And the article has NO references to the data from Starship Flight 13 or earlier flights . It is talking to some “expert” from NASA who references the SHUTTLE. It is clear that the shuttle had issues (CF Colombia although that was the leading edge, which did NOT use tiles but carbon fiber that was damaged by material shed from the fuel tank). Starship has learned lfrom the Shuttle. Its tiles are mostly identical and tessellated across the belly of the Starship. The shuttle’s tiles were often unique. They were pushing higher MAX Q this time to stress the tiles. Pretty much until they catch and look at reflying a Starship they won’t have a good idea of how much repair they’ll have to do, all the more reason to push the Starship catch forward in preference to resolving a Super Heavy catch in flight 14. Otherwise, it’s a lot of grousing from NASA engineers who haven’t actually built a reentry vehicle since the Shuttle. I’d bet most of those folks are LONG retired as the first shuttle flights were in the early ’80’s (and the last were 15 years ago) and I started working in 1983 and retired after 40 years of work. Better to look at the existing X-37, although much of that data is classified.
The article brings up some fair points and misses others. Overall, I agree that tiles have problems for reusability because they are delicate. However, the biggest advantage Starship has over Shuttle is that the tiles don’t sit next to or behind a tank shedding debris all over them. Unfortunately, I’m not sure what they’ll face in terms of debris when landing on the Moon or Mars.
While I did hear the speaker during the SpaceX coverage of the flight mention missing tiles; I wasn’t seeing any. I did see several damaged tiles that they did zoom in on. The white streak is offgassed material from the adhesive and probably a bit more noticeable due to being recently applied. You could see similar streaking on the space shuttle from the RTV adhesive, but as not every tile was freshly applied, it wasn’t as noticeable as flights continued. The streaking is interesting and shouldn’t be ignored, but hardly a reason to discontinue use.
The biggest problem with the article is the two quoted experts that come with their own biases. I don’t know if there is a suitable heatshield for Charlie Camarda. As for the creator of PICA, the A stands for Ablator. That means it works to reject heat by breaking off pieces as it gets hot, like a pencil eraser removing graphite. Sure, it has reuse potential by either using a lot of it or reapplying it entirely after every flight, but neither sounds a better option than replacing a few tiles, if any. It is used on Dragon, because Dragon doesn’t have the flight tempo expected of Starship, and therefore can have a new heatshield applied.
Still, the premise is correct. Re-entry vehicles need a heatshield, and very little science has gone into making a better one. I know, because I helped get a small experiment approved for use on the Shuttle heatshield. I was told initially to make sure it never got approved.
The white streaks are from the back-up layer of ablator. All the tiles have a fail-safe. I think it is also the gap filler and what you are seeing is the ablation of a bit of the gap filler material.
That seems like a good solution for both adhering the tiles and filling the gaps.
In a really obtuse way of thinking. I could imagine that at least for crewed vehicles, if you needed to conserve on heat shields, you’d park crews in one of the new commercial space stations for holding in order to aggregate crews for a return to Earth vessel. Like in the old West, where folks would hotel at towns and way-points awaiting arrival of a stage coach to take them elsewhere. This doesn’t work for fuel transports. Which is the key [re-]use of Starship. For Lunar HLS systems, you never return to Earth in them, so no heat shield needed. Mars a whole different animal.
Another less radical approach. A removable heat shield that can be replaced completely and quickly between launches. Admittedly a half-a-loaf reuse situation, ala Falcon 9 / Falcon Heavy.
Without the ability to recover SuperHeavy, all this becomes moot.
Even Elon admits the Starship TPS has been its toughest problem.
And Miller, Camarda and Rasky are not random cranks off the street or clueless retirees. Rasky actually worked at SpaceX during development of the Dragon heat shield.
It is true, so far as I know, that their TPS experience has all been with ablating materials and ablation is simply a non-starter for Starship for all sorts of reasons. But, if any or all of them have a non-ablative idea that is different from the current Starship tiles to proffer, they should do so. It should hardly be a problem arranging a meeting with Elon – especially for Rasky who has history with him.
As I’ve noted elsewhere, Elon is in the lowest percentile of people who are excessively in love with their own ideas and/or with current practice. The man who called the switch from carbon fiber composite to stainless steel for Starship as, in effect, an audible at the line of scrimmage would go for any really good new TPS idea in a New York minute.
Elon announced today they intend to recover 40 intact.
Better SpaceX than China! Arrr, ye matey!!!
Back in the days of VentureStar, there was all this talk about a metallic TPS, and how it was going to be so much better than ceramic tiles. Did that concept turn out to have an insuperable problem?
The money ran out?
The answer I recall about metal as a heatshield material was problems with atomic oxygen. I tried to find some papers for you, but honestly, the information I found gave different answers.
This one is straight forward in the title:
http://esmat.esa.int/Atox_on_metals.PDF
This one seems to be somewhat close to the original research and doesn’t suggest significant problems:
https://s3vi.ndc.nasa.gov/ssri-kb/static/resources/19990064119.pdf
This article seems to be a follow on to the second link:
https://ntrs.nasa.gov/api/citations/20030062195/downloads/20030062195.pdf
All that research is prior to Starship, which has video evidence of metallic surfaces facing re-entry plasma, and for the most part, holding up fairly well. Not well enough for re-use as is, but still well enough that exposed flight surfaces managed to operate.
It’s rather odd to make these claims now, when SpaceX has successfully returned several ships to a pinpoint splashdown. Even with many tiles intentionally removed in some cases, others lost, and at times portions of the ship blasted or melted off.
I’d say it’s worked pretty impressively well.
Perfect? No.
Resusable? Sure.
Rapidly reusable? Probably in an iteration or two. And those iterations come quickly at Starbase.
At one point it said in “NASA Tech Briefs” that it took 80 man hours to remove and replace a single tile. SpaceX is obviously doing it much faster. It looks like what they have works good enough for now, by the time rapid reuse becomes an important requirement, they’ll have lots of chances to improve. I bet they will.