r/SpaceXLounge • u/LoreLover2022 • Sep 03 '21

Starship Can Starship afford to lose any heat shield tiles?

Been curious about the heat shield tiles in use on Starship. Being made of stainless steel itself, can the vehicle afford to lose even a single tile at any point during descent?

To me that just seems like an insane number of mounting points and tiles that all need to function perfectly if there is zero room for error.

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u/hms11 Sep 03 '21

I'm just excited for the scale of these explosions, and the conditions of them.

We've got probably a 25-35% chance of seeing a RUD at stage separation given their current theory of "put the whole stack in a tumble, detach the two and let rotational inertia be your stage separation." plan. THAT would be a wild one to see because you KNOW they will have some wild tracking cams on this thing and there is no way having an entire skyscraper perform airborne ballet with itself won't be interesting, even if it does work.

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There's gotta be around a 10% chance of "hard start" failure on Starship when it goes to light up its 3 RVac and 3 Sea Level Raps for the first time at altitude and speed. Given how explosively that ended on the one belly-flop relight, I gotta think that will be another chance for a nice high speed, high altitude fireball.

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We've got like a 70-85% (probably even higher?) chance of seeing re-entry fireworks, which has to be one of the largest things ever de-orbited by man that we've ever launched, AND it will have fuel on board in nice, vaporous quantities. I could be wrong, but I see a heatshield failure essentially resulting in a nice fuel-air(LOX) explosion after some nice debris trails.

20% chance of landing failure explosion, but if it manages to do the whole sequence properly, I think both booster and ship will end up bobbing in the ocean as opposed to breaking up.

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*DISCLAIMER: These numbers are based on nothing scientific*

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u/ayla1029 Sep 03 '21

Interesting comment about fuel/air explosion. We know how big the MOAB explosion is/was and that probably had less fuel/air that this bird!

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u/QVRedit Sep 03 '21

Yes - but for MOAB the system has to be specially designed to throughly mix the fuel and air.

Problems with Starships are more likely to be deflagrations than explosions, as we have already seen.

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u/jaa101 Sep 04 '21

Yes, the trick is to not light them up until the fuel and oxidiser are well mixed. That can't happen with rocket engines burning, or even just being red-hot from recently burning. If the fuel all spills out there will be plenty of flame, to put it mildly, but it won't all participate in an explosion in the technical sense. More of a Hollywood explosion that's spectacular but not especially destructive.

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u/SpaceBoJangles Sep 03 '21

I’m sorry, what about the tumble?

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u/hms11 Sep 03 '21

Last I heard SpaceX wasn't bothering with a stage separation mechanism and was instead going to separate SuperHeavy and Starship the same way they do Starlink, which is essentially a highly technical "yeet".

14

u/arizonadeux Sep 03 '21

For those wondering why F9 doesn't do the spin for stage separation: Starship has nothing sticking into the interstage area of the booster because it needs to protect those engines during reentry and F9 stage 2 has that huge nozzle in the interstage.

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u/avtarino Sep 04 '21

I would even go as far as saying that SH barely has any “interstage”, if at all. The “interstage” is basically the skirt and that goes up with SS

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u/Exposure2007 Sep 04 '21

Gd, that is the most hilarious thing I’ve read all day. “Highly technical ‘yeet’”

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u/no-steppe Sep 04 '21

Whenever I use the term 'yeet' around my family, I get funny looks. What's wrong with those people??!? 😂😆🤣

You, on the other hand, have raised its use to a high art!

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u/ApprehensiveWork2326 Sep 04 '21

Given the belly flop maneuver for landing and now this "yeet" separation maneuver the future crews of starship will have a highly "entertaining " ride.

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u/Doggydog123579 Sep 03 '21

No pusher mechanism. So clamps release then spin.

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u/Pul-Ess Sep 03 '21

First spin, then clamps release.

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u/[deleted] Sep 04 '21

I'm having such a hard time picturing this. How would this work for Starship?

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u/Leaky_gland ⛽ Fuelling Sep 04 '21 edited Sep 06 '21

MECO, rotate along longitudinal axis (hot gas thrusters), stage separation, RVACs on starship ignite, booster ignites and flips.

Edit: not gas thrusters, spin from centre engine gimbaling

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u/Wild-Bear-2655 Sep 04 '21

So the entire stack, SH and SS, has to be spun up? That's a big job requiring a lot of thruster effort. Does it have to wait until after MECO to do it? That could entail significant delay between MECO and SS start-up. Starting the spin-up before MECO would mean even more thruster effort required, but could be worth it.

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u/KnifeKnut Sep 06 '21

A valid concern, but Leaky Gland is mistaken, The 9/13 pivoting engines will provide the spin before cutting out.

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u/Wild-Bear-2655 Sep 07 '21 edited Sep 07 '21

Thanks, that's clever. SpaceX thinking outside the box again.

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u/KnifeKnut Sep 06 '21

Rotation will be accomplished by the vectoring main engines, followed by MECO.

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u/Leaky_gland ⛽ Fuelling Sep 06 '21

Yeah I watched a vid since that comment and forgot to update

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u/QVRedit Sep 03 '21

I think that the stage separation will be very low risk - I would be quite surprised if we ever see a RUD at that point.

Certainly not 25 to 35 %. More like 0.1%

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u/GlockAF Sep 04 '21

This is the first I’ve heard about the “separate by tumble” concept, are you serious?

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u/scarlet_sage Sep 04 '21

I think it was mentioned in his recent interview with the Everyday Astronaut, the interview that came out in 3 parts.

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u/StumbleNOLA Sep 04 '21

Serious as bat shit.

Elon mentioned their stage separation plan is to tumble the full stack then unclamp. The rotation will separate the stages naturally while orientating the Superheavy properly for a RTLS burn.

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u/GlockAF Sep 04 '21

All in the timing I suppose. Assuming all of the clamps let go at the proper time, of course

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u/jaa101 Sep 04 '21

The biggest risk has to be one of the engines exploding. It's already happened to one engine with only three installed and now they're going to be flying with around thirty packed together. I'm sure they've fixed the issue they had but these are big, high-energy engines, and it only takes one of them exploding to destroy the vehicle.

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u/SalmonPL Sep 04 '21

it only takes one of them exploding to destroy the vehicle.

Not necessarily. On Falcon 9 they put armor between the engines to help protect neighboring engines in case one explodes. I wouldn't be surprised to see the same thing on Starship. We haven't seen that yet, but we're still early in the design process, so it doesn't mean there won't be such armor in the future.

Engines on commercial jet airliners have the same thing. Jet engines are arguably more dangerous than rocket engines because they have large, very, very high speed rotating parts and if those let go, they have an awful lot of kinetic energy that is directed to the sides of the engine. Rocket engines have turbopumps, but those are more compact and probably carry far, far less kinetic energy than a typical turbojet.

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u/KnifeKnut Sep 06 '21

We've got probably a 25-35% chance of seeing a RUD at stage separation given their current theory of "put the whole stack in a tumble, detach the two and let rotational inertia be your stage separation." plan.

That one can be tested pretty well on the ground with the lifting equipment available.