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Starship Integrated Flight Test 2 at 7 Am Central Time

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Re: Starship Integrated Flight Test 2 at 7 Am Central Time

#361

Post by x86x87 »

ceejayoz wrote: post #343
x86x87 wrote: post #335

Earlier quoted context omitted.

This is not about laughing or not. This is about if it was objectfully a successful test or not. If you want to take the stance that any test is a success that's fine but remember this depends on what your definition of success is. The other thing to keep in mind is that past success is not always a good predictor of future success.

There's no "objectively" here. It's all feels. Objectively , this test successfully demonstrated the water deluge system, an intact launch pad, all engines on the first and second stage igniting and staying lit, stage separation, hot staging, and a long burn nearly to orbital speeds. That's a pretty good list of ticked boxes. They very openly stated they didn't necessarily expect it to get all the way to splashdown.…

Objectively, for any test to be judged a failure or success you have to define the outcome you want upfront. If you do not any amount of mental gymnastics you you after the test does not matter.

It does not matter you call it a win if you are not respecting other opinions that this is a fail.

Re: Starship Integrated Flight Test 2 at 7 Am Central Time

#363

Post by x86x87 »

lutorm wrote: post #359
x86x87 wrote: post #338

Earlier quoted context omitted.

Are we reading the same comment? I don't see any dismissal of previous accomplishments. Why is calling this failure a failure bad? You need failures to learn and hopefully be successful eventually.

Do you mean this was a launch failure or a test failure? It was obviously a launch failure, but even the most optimistic wouldn't have expected anything else. As for whether the test was a failure: since it successfully did a bunch of things that didn't work the last time, why would you say it's a failure? A failure would have been scattering the pad all over again, and not getting to stage sep. Or worse.

You have to define upfront what you want to get from a test. After that you go back and see if what you got is what you expected.

Optimistic/Pessimistic does not really matter.

By this criteria, I would say failure/partial failure or partial sucess. There is no way this was a success.

Also, everyone can call this what they want. The thing that grinds my gears is not respecting that other people do have a different opinion.

Re: Starship Integrated Flight Test 2 at 7 Am Central Time

#364

Post by lutorm »

aw1621107 wrote: post #300
grecy wrote: post #256

Earlier quoted context omitted.

It also makes the rocket more efficient, because any time spent coasting with no engines lit is time that gravity is acting on the rocket and slowing it down. By always accelerating (with engines lit), hot staging improves the payload to orbit about 10%. So it's well worth doing.

Less gravity losses is another advantage, that's true. I think it'd be interesting to see a breakdown of that 10% improvement number. Hot staging in and of itself resulting in a 10% additional payload capacity seems large enough that I feel it's rather odd that it isn't more commonly used. I'm curious how much of it is due to "direct" improvements from reduced gravity losses and how much is due to "indirect" improvem…

Well, the old staging method tried in the last launch was to rotate the entire vehicle stack and "fling" the ship off. That obviously has a performance penalty in that you're not going to be pointing in the correct direction when you come off. I don't know if the 10% was compared to that or compared to a hypothetical "straight" staging with pushers, though.

Re: Starship Integrated Flight Test 2 at 7 Am Central Time

#365

Post by sbuttgereit »

pelorat wrote: post #347
dotnet00 wrote: post #106

Really surprised by how the Raptors performed! Genuinely didn't expect that they'd have them all lighting up properly already.

I believe this flight used the old Raptor engines, and not the new simplified ones.

Pretty sure they used Raptor V2 which simplifies from V1; Raptor V3 I believe is simpler still, but that's still being tested at the SpaceX MacGregor TX facility.

Re: Starship Integrated Flight Test 2 at 7 Am Central Time

#366

Post by avmich »

dclowd9901 wrote: post #298
aw1621107 wrote: post #173

Earlier quoted context omitted.

To expand on KennyBlanken's answer: Rockets generally want their fuel to be sitting on the bottom of the tank, where the engines are. That's easy enough when the rocket is sitting on the ground and when the engines are firing, but once the rocket starts coasting/decelerating (e.g., when the engines turn off due to reaching the end of their burn) the fuel may drift away from the fuel intakes, resulting in the engines…

Given how successful our Saturn package was, it seems curious to me that we wouldn’t just follow the ullage motor method.

Ullage motors have to be solid - this way they don't need ullage themselves to fire - or to be fed from separate tanks - this is another reasonably complex subsystem which needs to be refueled somehow between flights. If ullage motors are solid, that needs to be re-loaded between flights. So, overall the ullage system is a certain complexity to design, build, refuel, a weight to carry in flight - clearly some drawbacks.

Hot firing simplifies things in this regard.

Re: Starship Integrated Flight Test 2 at 7 Am Central Time

#367

Post by sbuttgereit »

x86x87 wrote: post #361
ceejayoz wrote: post #343

Earlier quoted context omitted.

There's no "objectively" here. It's all feels. Objectively , this test successfully demonstrated the water deluge system, an intact launch pad, all engines on the first and second stage igniting and staying lit, stage separation, hot staging, and a long burn nearly to orbital speeds. That's a pretty good list of ticked boxes. They very openly stated they didn't necessarily expect it to get all the way to splashdown.…

Objectively, for any test to be judged a failure or success you have to define the outcome you want upfront. If you do not any amount of mental gymnastics you you after the test does not matter. It does not matter you call it a win if you are not respecting other opinions that this is a fail.

SpaceX very clearly stated just prior to launch that their goal was for the rocket to get through hot-staging because the hot-staging process they had large unknowns. Sure their flight plan went well beyond that, but I don't see how having an aspirational plan that goes beyond "we'll blow it up after hot-staging", also likely required for the FAA, defeats the "successful" qualification of the test.

Re: Starship Integrated Flight Test 2 at 7 Am Central Time

#368

Post by dang »

runesoerensen wrote: post #35

Link should be updated to https://twitter.com/SpaceX/status/1725637151176659003 or https://www.spacex.com/launches/mission/?missionId=starship-... (no login required)

Fixed now. Thanks!

(Submitted URL was https://twitter.com/i/broadcasts/1dRKZEWQvrXxB but our software got caught in a redirect to a login.)

Re: Starship Integrated Flight Test 2 at 7 Am Central Time

#369

Post by hparadiz »

bryanlarsen wrote: post #167
idlewords wrote: post #113

Earlier quoted context omitted.

They need to redesign the bottom half of the rocket so it doesn't blow up during staging, and figure out what happened to the top half and fix that.

They don't necessarily have to redesign the booster. The booster completed its primary mission of boosting successfully. It survived long enough that it seems reasonable to say that if they wouldn't have attempted boost back it would successfully coasted to a splash in the ocean. So the SuperHeavy booster can likely be used as is, if they're willing to spend an extra ~$50M per mission on not recover the booster.

Pretty sure NASA doesn't care about losing the booster for a moonshot mission. Shuttle was 1.6 billion per flight.

Re: Starship Integrated Flight Test 2 at 7 Am Central Time

#370

Post by pixl97 »

anovikov wrote: post #328
pixl97 wrote: post #250

Earlier quoted context omitted.

Damage to the grid fins mechanism is a potential failure mode here. Even a small amount of damage to the flight control systems could make the procedure uncontrollable and eventually trigger the FTS.

At this altitude, the vehicle is pretty much in the vacuum and grid fins have absolutely no control authority. It could have resulted in failure later on but not at that point where the booster blew up.

Saw that Scott Manley video that came out right after that and it looks like fuel issues to engines probably caused it. All but one engine started up, but they started failing after that.

https://www.youtube.com/shorts/7LYw6gU65ac

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