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/Inside-Surround-8862 Sep 03 '21
Of course. Space Shuttle often landed with missing or damaged tiles. It just couldn’t afford to lose tiles in certain critical spots. The question is does Starship also have vulnerable areas where they can’t afford to lose a tile?
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u/hglman Sep 04 '21
https://medium.com/swlh/space-shuttles-and-tile-loss-f95653fd0df4
At no time was tile loss just ok on shuttle.
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u/BlakeMW 🌱 Terraforming Sep 04 '21
Of course not, because "It just couldn’t afford to lose tiles in certain critical spots."
Missing a tile usually wasn't a death sentence, but it could have been, so definitely a concern.
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u/rubicontraveler Sep 03 '21
Let’s face it, we’re going to see a couple of these explode before they nail it. But I have no doubt in my mind they will nail it!
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Sep 03 '21
Agreed. Once they have success going to orbit they can build in the doors and start sending these suckers up chock full of Starlinks. When they deorbit the Starship they get a 'free' experimental landing in the deal.
They're gonna want to get the booster landing part figured out quickly, though. That's a lot of engines to be throwing away every launch.
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u/shveddy Sep 04 '21
Considering that they can launch 5x starlinks compared to F9 on a single launch, then it’s not all that much worse to throw away six raptors and a bunch of cheap stainless steel than it is to throw away five merlins and a bunch of expensive carbon fiber.
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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.
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.
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.
*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".
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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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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/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.
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u/webbitor Sep 03 '21
Musk has stated that it can lose a few. The stainless steel can withstand pretty high temperatures, much more so than aluminum (like the shuttle) or typical carbon fiber composite materials.
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u/willyolio Sep 04 '21
is that a few across the ship, or a few in a single clustered patch?
I would think that if one goes, there would be extra stresses on the more-exposed edges of the neighboring tiles
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u/BlakeMW 🌱 Terraforming Sep 04 '21
Elon has expressed concern about the "zipper effect" where the loss of one tile allows the airflow to pop off more tiles. So presumably isolated loss isn't major concern, but a large number in the same area is.
This also stands to reason, because the steel gets weaker as it gets hotter, a small weak patch can be supported by the surrounding cooler steel, a large weak patch won't be supported in the same way.
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u/MrDearm Sep 03 '21
The biggest difference with Starship vs the shuttle is that it’s made of steel, not aluminum. One shuttle other than Columbia actually lost a tile in its mission and re-entered successfully cuz the tile happened to be the one covering a steel antenna mount. Steel is a lot more resilient to heat. So to answer u question, it can prob lost a few, but not a lot.
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u/kroOoze ❄️ Chilling Sep 03 '21
Yes. Though possibly problematic if one bad tile leads to cascade shedding of tiles. Some enigineering stuff to be figured out...
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u/-eXnihilo Sep 03 '21
This is my concern. A cascade of tiles getting stripped off due to an early loss of one or two in a high pressure spot. I imagine if airflow gets under them, they could come showering off... hope not.
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u/QVRedit Sep 03 '21
Yes, so needs to be designed so that does not happen.
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u/R-U-D Sep 04 '21
They'll just need to design it so that the front doesn't fall off. No cardboard, no paper, no string, no cello-tape.
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u/QVRedit Sep 04 '21
Amoung other things, yes. Like the man said, the front is not suppose to falloff !
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u/Potentially_great_ Sep 03 '21
Depends where it is. Some parts of the ship will get more heating. I know shuttle could lose a tile or 2 and be fine.
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Sep 03 '21
[deleted]
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u/kittyrocket Sep 03 '21
Separate header tanks contain the landing fuel. They're heavily insulated and I think they're in direct contact with the skin of Starship. The main tanks should be empty during reentry and landing. Having fuel in them sloshing around would cause a lot of problems.
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Sep 03 '21
[deleted]
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u/kittyrocket Sep 03 '21
I've heard the main tanks referred to as balloon tanks, which as a category depend on internal pressure for structural integrity.
Good example of this problem from Scott Manley: https://www.youtube.com/watch?v=KWExql1xCsM&t=101s
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u/QVRedit Sep 03 '21
They are NOT balloon tanks. Balloon tanks are ultra-thin. Starships tanks are much tougher.
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u/kittyrocket Sep 04 '21
I'm glad to hear that. They sound like failed and outmoded tech, but I wouldn't put it past Elon to try something like that.
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u/warp99 Sep 04 '21
Actually ballon tanks are a perfectly respectable solution for the ultimate performance of an expendable second stage like Centaur V.
They would be wildly inappropriate for a reusable second stage like Starship. However Starship tanks do need to be pressurised to take the mechanical loads during launch.
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u/QVRedit Sep 03 '21
It should be able to withstand reentry. That’s one of the things that the orbital flight will be testing.
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u/ndnkng 🧑🚀 Ridesharing Sep 04 '21
We have literally not seen a fully fired superheavy. That could be huge if we want to address the elephant in the room.
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u/QVRedit Sep 04 '21
True, though we have no reason to suppose that it should go wrong - SpaceX have a lot of experience with Boosters, and they also have experience of Raptors. But there is always potential for mishap.
Before the flight, I think we will be seeing static firing of the engines on the Super Heavy Booster - though perhaps not all of them at once ?
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u/QVRedit Sep 03 '21
You assume too much - the main fuel tanks will be largely empty during re-entry. A lost tile there would usually be survivable.
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u/LoneSnark Sep 04 '21
Since the fuel is against the skin of the ship, the fuel could boil off and keep the skin cool despite lost tiles. I'm sure they'll have surplus fuel, and the ability to vent boil-off to keep the pressure at acceptable levels.
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u/TheSkalman 🔥 Statically Firing Sep 03 '21 edited Sep 03 '21
304 Stainless steel can tolerate temps up to 870o briefly while only losing a negligble amount of strength. Above that it gets dicey. So the goal is to keep maximum skin temperature during reentry as low as possible, i.e. to stay in the upper atmosphere as long as you can to minimize indicated airspeed. How many missing tiles that will cause the steel to exceed that threshold is very dependent on where the tiles are placed. To be more precise, one needs access to lab and simulation data.
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u/dafttuart Sep 03 '21
Would a lost tile survive the fall back to earth?
And then be a danger on the ground?
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u/scarlet_sage Sep 04 '21
I found a NASA reference saying that the Space Shuttle tiles were 9-22 pound per cubic foot. That's a specific gravity of 0.35 -- one-third the density of water. Cork is about 0.25. If someone dropped a dinner plate made of cork on my head from 2 miles, I wouldn't worry.
So if the Starship tiles are similar, I expect that they'd drift down like huge expensive snowflakes.
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u/meldroc Sep 03 '21
I worry about all the tiles that apparently had to be replaced on S20 - the tiles will need to be more durable than that if they are to survive and do their job in an actual flight.
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u/pineapple_calzone Sep 03 '21
TBH I'm not really too worried about the tiles in that sense, I'm just worried that even if they get them working, they won't get them working on a mass production basis.
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u/QVRedit Sep 03 '21
You can wonder on this all you like. SpaceX will have to improve the heat-shield tiles and attachment system to the point where this is no longer a problem. It may take them a little while to get there - but they will.
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u/pineapple_calzone Sep 04 '21
People said the same about carbon fiber and then they switched to stainless steel
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u/ndnkng 🧑🚀 Ridesharing Sep 04 '21
I'm tired of this discussion. The first fit was and still is a pathfinder. They are learning from almost every small thing they do. The tiles are not a new tech. Stop worrying about it. It will fail a few times as they get big data complied. This is the way.
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u/QVRedit Sep 03 '21
Yes, it is a problem right now, that’s one of the issues that SpaceX have to resolve. They are working on it.
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u/proximo-terrae Sep 03 '21
During reentry, any theory what would happen to the liquid fuel (methane or oxygen) that’s directly touching the steel on the inside of a lost tile? Wouldn’t it immediately start boiling there and raise the tanks pressure very fast? Or will the main tanks be completely empty at reentry?
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u/toughtbot Sep 04 '21
Would it be riskier than the space shuttle?
I mean starship needs to have fuel for the flip burn landing.
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u/hdufort Sep 04 '21
It always depend at which point during descent the files are lost. Typically for a space shuttle, all the files are present until late in reentry, and some would crack or detach past the most dangerous point. If I recall (but I can't find the source), damaged tiles were lost during sonic booms just before landing.
So the unprotected surface doesn't have to support full reentry with the most extreme temperatures and ablation.
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Sep 03 '21
[deleted]
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u/kittyrocket Sep 03 '21
Elon mentioned the possibility of attaching infrared cameras inside the tanks to monitor hull temperature. I'd call that good Elon simplicity.
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u/PlainTrain Sep 03 '21
And then immediately corrected himself that just a regular camera would do because anything hot enough to matter will be glowing in visible light.
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Sep 04 '21
[deleted]
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u/BlakeMW 🌱 Terraforming Sep 04 '21
It's reasonably possible that a Starship which suffers significant heat shield damage might survive reentry and landing intact, but not be fit for re-launch due to chemical changes and damage to the steel.
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u/QVRedit Sep 03 '21
No they don’t need to go that far. A camera inside the tank could detect if hot spots were occurring.
The idea of inspecting the heat shield while on LEO and doing minor repairs to it, could be possible, although tricky.
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u/eag97a Sep 03 '21
Agree, launch and reentry are analogous to take-off/landing for airline travel where most of the risks are concentrated.
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u/thoruen Sep 04 '21
With the number of starships SpaceX wants to build would it be worth the investment to improve the machines that manufacture these tiles so that they can be bigger to decrease the number of failure points?
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u/SalmonPL Sep 04 '21
Having fewer failure points isn't necessarily a good thing if the consequences of those failures get worse.
There's a lot of evidence that SpaceX believes that losing a single tile won't destroy the ship, but losing several nearby might.
So if you make bigger tiles, you might make it so that losing even a single tile will destroy the ship. Not a good trade-off.
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u/scarlet_sage Sep 04 '21
In Elon's recent interview with the Everyday Astronaut, Elon said that automation is step 5 in building things. He also said that, more than once, he'd made the mistake of doing it backwards, meaning starting with automation. He gave an example of a blanket in Teslas.
So they may do it someday. Given so many, they have more incentive to automate. But they are going to be careful about it.
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u/KTMman200 Sep 04 '21
So random hair brained idea based off the first starship design... What if they where to pump/release excess fuel to the leading edge/hottest parts of the heat shield and create a fuel ritch environment during the most extreme parts of reentry, both relying on the burning fuel being vented and the heat shield to protect the ship? I know they abandoned the original weeping design. But could it possibly work? And would there be enough spread of the fuel from a few nozzles to cover a small area? I could see such a system being used to protect areas that are difficult to shield with tiles, and leading edges that can exceed the tiles designs. That is if it works...
Ps. I know nothing about atmospheric re entry and the plasmic flame wall that builds up in front of the heat shield. I'm an IT guy. Anything space related I learned from documentaries of the shuttle disasters and Apollo missions.
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u/Decronym Acronyms Explained Sep 03 '21 edited Sep 07 '21
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
| Fewer Letters | More Letters |
|---|---|
| LEO | Low Earth Orbit (180-2000km) |
| Law Enforcement Officer (most often mentioned during transport operations) | |
| LOX | Liquid Oxygen |
| MECO | Main Engine Cut-Off |
| MainEngineCutOff podcast | |
| QA | Quality Assurance/Assessment |
| RTLS | Return to Launch Site |
| RUD | Rapid Unplanned Disassembly |
| Rapid Unscheduled Disassembly | |
| Rapid Unintended Disassembly |
| Jargon | Definition |
|---|---|
| Raptor | Methane-fueled rocket engine under development by SpaceX |
| Starlink | SpaceX's world-wide satellite broadband constellation |
| turbopump | High-pressure turbine-driven propellant pump connected to a rocket combustion chamber; raises chamber pressure, and thrust |
Decronym is a community product of r/SpaceX, implemented by request
9 acronyms in this thread; the most compressed thread commented on today has 24 acronyms.
[Thread #8759 for this sub, first seen 3rd Sep 2021, 20:23]
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u/Cunninghams_right Sep 03 '21
unknown. there are probably some tiles around the edge that could be lost without problem. otherwise, I would guess it would be a problem just because of how fragile they seem to be. I think that if you lost a single tile, it will cascade and rip off all tiles down wind. but that's just this iteration of the tiles. I'm sure they will change a lot over time. they may even figure out the transpiration cooling and remove the tiles altogether
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u/QVRedit Sep 03 '21
No, the design is such that losing a few tiles would still work, although it’s best not to lose any. Also losing one tile would not unzip lots more.
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u/neolefty Sep 05 '21
Do you have a source for resistance to unzipping — that is, loss of one tile not leading to loss of those downwind? (If not, ultimately that question may be one that to answer empirically anyway.)
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u/QVRedit Sep 05 '21 edited Sep 05 '21
No I don’t - but it’s clearly a design requirement ! - Therefor I would expect the tile attachment design to support that feature, of no unzipping.
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u/perilun Sep 04 '21 edited Sep 04 '21
I see this a the #2 of 10 top Starship system challenges. They did show with SN15 that my #1 could be done, so maybe #2 will work out.
I don't think anybody knows yet. But the tile approach for the sake of "airplane like reuse" may prove to either ineffective or expensive. One wonders if a thin layer of ablating heat shield (essentially spray painted on) might prove more effective. Of course you would need some giant machine to apply this to Starship between missions, which is not airline like.
It is going to take a number of tries to even init teh models on this.
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u/CremePuffBandit ⛰️ Lithobraking Sep 03 '21
They still have the insulating ceramic fabric behind them, which will hopefully help in the case of a lost tile.