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If Starship 20 will not be recovered, how will SpaceX evaluate the performance of the heat tiles? If a couple of heat tiles fall off and the Starship bursts into flames, how can SpaceX figure out what happened?

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    $\begingroup$ This is just speculation, but with how small and lightweight sensors are, I wouldn't be surprised if they equipped every single tile with a heat probe/integrity sensor and recorded this data to a "black box" or directly transmitted it. Maybe we will see some really cool visualizations of thermal load on the individual tiles later. $\endgroup$
    – Dragongeek
    Sep 11, 2021 at 9:12
  • $\begingroup$ Well, there is the issue of transmitting anything during re-entry, but perhaps the data box could be jettisoned (and recovered) just prior to the "landing". $\endgroup$ Sep 11, 2021 at 11:49
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    $\begingroup$ @RobertDiGiovanni: I hear Elon Musk knows a guy who can hook him up with a satellite data connection. $\endgroup$ Sep 11, 2021 at 18:42
  • $\begingroup$ Two starships later, the TPS tiles start to come into play. And the answer now is : cameras streaming over Starlink. $\endgroup$
    – Florian F
    Mar 21 at 10:45

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SpaceX is collaborating with NASA Langley "to capture imagery and thermal measurements of its Starship vehicle during orbital re-entry over the Pacific Ocean." They will do this via a WB-57F research aircraft equipped with a suite of infrared cameras called "Multispectral Airborne Imaging System (SAMI)".

They won't be able to do post-flight inspection because the first (couple) Starship(s) to reach reentry won't survive it (opinion).

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  • $\begingroup$ They certainly will see plenty of heat outside. That won't really tell them how hot it becomes inside. But it is the most factual answer. Watching the ship from outside will probably give a good picture of whether it works. $\endgroup$
    – Florian F
    Oct 12, 2021 at 22:31
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The primary objectives will be testing 29 engine engine ignition and lift off of the full stack. The performance of Superheavy, stage separation and firing all 6 Starship Raptors at altitude.

If they get to orbit then they will have done well and achieved a lot. The likelihood of some serious destructive problem before reentry is high, so they are not expecting a lot.

However if Starship lands on the water in one piece it will be a massive win and it would prove their approach to the heat shield works more or less as is. If it fails during reentry then I imagine they will have sufficient instrumentation on board to detect and relay where the failure point was and when it occurred. That together with their detailed records of the tiling placement and issues encountered during tiling should provide a lot of useful data to them about how to improve the design.

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If Starship 20 will not be recovered, how will SpaceX evaluate the performance of the heat tiles?

If Starship 20 is in a condition where it can be recovered, then that is the evaluation of the performance of the heat shield tiles: they worked, otherwise there wouldn't be anything to recover.

If a couple of heat tiles fall off and the Starship bursts into flames, how can SpaceX figure out what happened?

If the Starship bursts into flames, there is nothing to recover, so your focus on recovery to figure out what went wrong is somewhat internally self-inconsistent: if something went wrong, there is likely nothing to recover, and if there is something to recover, then likely nothing went wrong.

It is likely that Starship 20 will have sensors on board. (All the previous ones did, as does Falcon 9.) It is also likely that Starship 20 will stream telemetry data in real time. (All the previous ones did, as does Falcon 9.)

In fact, Elon Musk explicitly mentioned the use of cameras inside the tanks in his recent inverview with Tim Dodd, the Everyday Astronaut. Tim Dodd specifically asked about sensors for the heat shield tiles, and Elon Musk semi-jokingly responded that you don't need fancy sensors, you can spot a failure of the heat shield by the rather obvious white-hot glowing stainless steel.

However, chances are very high that the heat shield will not come into play at all. In that same interview, Elon Musk said that the success criterium for the (almost-)orbital flight test is whether or not they need to restart building the launch pad from scratch. In other words, not destroying Starbase will be considered a success, which implies that destroying the launch pad is a possibility that SpaceX is calculating.

There are so many milestones to reach before reentry, a lot of which have never been done before, that the heat shield is probably pretty far down on the list. This is going to be the first flight of a Superheavy booster, ever. This is going to be the first flight of the combined stack. It is the first time more than 3 Raptors are ignited at the same time. It is the first time the Raptor Vacuum is ignited in flight. It is the first flight from the Orbital Launch Mount. It is the first use of the Orbital Tank Farm. It is the first use of the Quick Disconnect System of the Superheavy booster. It is the first use of the new Quick Disconnect System of Starship. (The old one was on the bottom under the skirt, the new one is on the side.) It is the first use of this crazy state separation mechanism where they just put the booster into a spin and "fling" the Starship away. (Yes, they do this with the Starlink satellites as well, but that is a much smaller rocket, outside the atmosphere, and during cruise – here it is the biggest rocket ever built, in the upper atmosphere, and during ascent.)

It is very likely that Starship will not reach orbit.

There is also the question whether SpaceX even cares about Starship 20's heat shield tiles anymore. A huge number of tiles fell off simply driving from the High Bay to the Launch Site, so SpaceX already knows they have problems with the heat shield. Also, the biggest problems with the heat shield are going to be around the body flaps and on the nose, and SpaceX already knows that Starship 21 will have a significantly different nose cone and significantly different body flaps. In particular, the new nose cone is much smoother and more regular and the forward body flaps will be smaller and move leewards (and might not need heat shields at all, depending on how far out of the wind stream they will be moved).

Considering that SpaceX already knows they have problems, and that the hard part of the heat shield is in places that are going to change anyway before Starship 21, it might even be the case that they don't care about data about the heat shield.

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  • $\begingroup$ Actually I am a bit puzzled about all the fuss around the heat tiles, checking or replacing every single one, making the maximum to make them work. Because SpaceX seem to believe it is not very likely the flight will go so far. You also stress that point, so why bother? And even if it goes so far, in some sense it doesn't make a big difference whether the ship is destroyed or sinks intact. The only reason they spend so much time on the heat tiles would be to get valuable test data. But yes, sensors, a camera and telemetry is probably the answer provided they can transmit during reentry. $\endgroup$
    – Florian F
    Sep 11, 2021 at 23:18
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    $\begingroup$ They need to practice putting the tiles on. Not breaking the tiles, aligning the tiles and understanding why they don't quite fit right or why they do. You can't do that from an armchair. So they will give it their best shot and may be as a bonus get a 20% chance of testing it out. If it doesn't work then they will try again (and again) until it does work. making improvements all the time. Eventually they will sort it out by shear weight of numbers. They are currently preparing to launch booster #4, booster number 5 is well underway and booster #6 is also being built. similar with Starships. $\endgroup$
    – Slarty
    Sep 13, 2021 at 15:30
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This was an issue when they were blowing up earlier SN models, but SN 20 may be a bit different in that it could be recovered nearly intact if it executes a soft landing on water (not unlike a capsule splashdown) and is able to float long enough to be recovered.

Landing is somewhere off Hawaii, and it would be a shame just to let it sink (with all those Raptor engines). Although the odds may be low for the first orbital shot to go well, placing a recovery barge out there should not be outside the realm of reason.

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    $\begingroup$ It might be able to be recovered nearly intact, but Elon is on record (IIRC) in saying that they won't recover it. The Raptor engines will be so much scrap metal by then anyway as the design is advancing quickly and those old engines will be obsolete and will also have been smashed into the sea with some force and had a good rinse in salt water as well. $\endgroup$
    – Slarty
    Sep 11, 2021 at 0:09
  • $\begingroup$ Well, the flight plan may be advancing too. Sans barge, they could bring it to a hover around 20 feet ASL, then let it drop onto some inflatables. Dented a bit, yes, but let's check those tiles. $\endgroup$ Sep 11, 2021 at 0:18
  • $\begingroup$ Perhaps the could but they won't $\endgroup$
    – Slarty
    Sep 11, 2021 at 1:04
  • $\begingroup$ Once you dunk something in salt water that isn't engineered to take it, it's usually just trash. $\endgroup$ Sep 11, 2021 at 2:29
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    $\begingroup$ Trash, as in it isn't worth repairing. That's not to say they can't analyze it. $\endgroup$ Sep 12, 2021 at 2:10
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If, buy chance, it lands smoothly I would expect it would float for days if not weeks. Remember; buoyancy is a function of displacement and upon the return to earth Starship 20 will be, mostly, a huge empty fuel tank.

In a smooth landing scenario, if they elect to not recover it, they may have to deliberately scuttle it.

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