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SpaceX Starship rocket explodes minutes after launch from Texas

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Re: SpaceX Starship rocket explodes minutes after launch from Texas

#811

Post by pfannkuchen »

ShamelessC wrote: post #236
ianai wrote: post #189

Let’s not move the goalposts. This company develops differently than historical aerospace. Success was defined as blowing up any point beyond the launch pad. It made it well past max-q which is the point of highest atmospheric stress on the rocket.

What provoked this response? The headline makes no assertions about success or failure. It is extremely literally a description of what occurred. It’s one thing to feel defensive about a misleading headline. This is just fanboyism.

There are, of course, multiple ways to describe any situation in a literally accurate way. A canonical example is "glass half empty" vs "glass half full".

If a glass is expected to be at one tenth of its capacity, but then, by surprise, it is found to be at one half of its capacity, then it is a bit odd to write the headline "Glass Half Empty". We would instead expect something like "Glass Half Full by Surprise", or at least "Glass at 50% Capacity". I don't think one has to be a fanboy of glasses or liquids to take issue with that framing.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#812

Post by jpgvm »

RetpolineDrama wrote: post #664
pfannkuchen wrote: post #524

I am really surprised at the negativity, it makes me want to stop coming here. How many here are actual engineers by profession? The default state of any novel engineering project is “not working”. Rockets are very hard among engineering projects. Failure here would look like the rocket doing nothing visible, perhaps a little bit of smoke. Neutral is the rocket exploding. Success is the rocket moving at all. The rock…

>How many here are actual engineers by profession? Almost none, because "software engineers" aren't _actual_ Engineers! (ducks for cover) But really, this was a huge step in the right direction on the cutting edge of propulsion science and spaceflight. SpaceX will iterate and in a few months/years everyone here will be telling you how "they always knew it would work" and "starship succeeding was obvious"

Can confirm, am "Software Engineer" but from a family of Real Engineers™, what we do on a day to day basis only resembles engineering in the weakest sense.

Both professions iterate on failure but Real Engineers actually spend a significant amount of time studying each failure and drawing strong conclusions based on collected data. We can do that (and sometimes do) but usually just hack it and re-run the tests until it works, can't really do that with a physical test though unless you have reduced your problem down to a small test article (something programmers should always do because it's cheap and easy).

Our field is young and lacks the rigorousness of Real Engineering. We probably don't want to adopt all of it because our cost and risk profiles are hugely different but there is a lot to learn from Real Engineers about how to iterate better and get better bang for our buck out of our failures.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#813

Post by jpgvm »

mjamesaustin wrote: post #775
nonethewiser wrote: post #691

Earlier quoted context omitted.

Does SpaceX build the actual engines? Are they as complicated as airplane engines which are famously hard to produce?

SpaceX designed and built all the engines. The Raptor engine is the world's first full flow staged combustion engine to fly in a rocket.

i.e not only do they make rocket engines they make the worlds most advanced and complicated rocket engines and they make so many of them you could consider them mass produced. (as far as rocket engines go that is)

These engines require a very delicate dance of chamber pressure, temperature, fuel/oxidiser mix, turbo pump speeds, etc to get started but it's all worth it in the end for their insane efficiency and thrust/weight.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#814

Post by chasd00 »

ChuckMcM wrote: post #798
kortex wrote: post #365

Initially posted this as a reply, but going top-level, cause the hot takes are too spicy for my liking. So the plan was to test x, y, and z. Launch sequence and takeoff, stage separation and Starship engine light, and the post-launch stuff like booster wet landing, reentry, and heat tiles. The booster by itself is not aerodynamic, so the only way to test x is with a starship on top. And if you have starship, you migh…

Good analysis of the goals of this test. That said, the failure was interesting to me. In the SpaceX feed they were waiting for the second stage to separate and light, and it didn't do either. So first question is why didn't it separate? I think that is the relevant one because I would expect them to have interlocks that would prevent the second stage from starting up if it were still attached to the booster. The int…

a few seconds after liftoff a hydraulic unit on the bottom of the booster blew off. That could have had all kinds of ramifications for further events down the road like stage separation and MECO. I'm actually surprised it maintained as good of control is it did given i'm sure that controlled at least some of the gymbaling too.

The cartwheel is on purpose. They're using the angular momentum of the flip for boost back to fling the starship off instead of the usual explosives. I think it cartwheeled multiple times because of multiple attempts to get Starship to separate. Whatever was holding Starship to the booster wasn't letting go which could have been a hydraulic failure (see my first paragraph).

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#815

Post by chasd00 »

Cthulhu_ wrote: post #786
kortex wrote: post #365

Initially posted this as a reply, but going top-level, cause the hot takes are too spicy for my liking. So the plan was to test x, y, and z. Launch sequence and takeoff, stage separation and Starship engine light, and the post-launch stuff like booster wet landing, reentry, and heat tiles. The booster by itself is not aerodynamic, so the only way to test x is with a starship on top. And if you have starship, you migh…

I think the thing that a lot of people are still stuck at is the NASA attitude of "we've spent a lot of money on this already, we Need to make sure it works first try". Whereas SpaceX is more like Kerbal Space Program in that if it blows up, at least you're having fun. And while they had some failures early on with their early rockets, the Falcon 9 is now a very reliable craft that's done dozens of successful mission…

i think people forget they crashed a lot of starships doing the suborbital tests before they got one right. I think we'll see the same with the booster, expect more qualified tests success before you see something a layperson would call 100% success.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#816

Post by ChuckMcM »

chasd00 wrote: post #814
ChuckMcM wrote: post #798

Earlier quoted context omitted.

Good analysis of the goals of this test. That said, the failure was interesting to me. In the SpaceX feed they were waiting for the second stage to separate and light, and it didn't do either. So first question is why didn't it separate? I think that is the relevant one because I would expect them to have interlocks that would prevent the second stage from starting up if it were still attached to the booster. The int…

a few seconds after liftoff a hydraulic unit on the bottom of the booster blew off. That could have had all kinds of ramifications for further events down the road like stage separation and MECO. I'm actually surprised it maintained as good of control is it did given i'm sure that controlled at least some of the gymbaling too. The cartwheel is on purpose. They're using the angular momentum of the flip for boost back…

I have seen that analysis too, the twitter thread suggested that both HPUs on the booster eventually failed before second stage separation. That could be quite significant.

Also the lack of gimballing capability could presumably have the booster continuing to thrust as it attempted to maintain attitude control even as it reached the MECO point.

I wonder how much of this learning can be applied to the next launch as they may have design issues that are already "baked in" to the built boosters.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#817

Post by gvb »

ChuckMcM wrote: post #798
kortex wrote: post #365

Initially posted this as a reply, but going top-level, cause the hot takes are too spicy for my liking. So the plan was to test x, y, and z. Launch sequence and takeoff, stage separation and Starship engine light, and the post-launch stuff like booster wet landing, reentry, and heat tiles. The booster by itself is not aerodynamic, so the only way to test x is with a starship on top. And if you have starship, you migh…

Good analysis of the goals of this test. That said, the failure was interesting to me. In the SpaceX feed they were waiting for the second stage to separate and light, and it didn't do either. So first question is why didn't it separate? I think that is the relevant one because I would expect them to have interlocks that would prevent the second stage from starting up if it were still attached to the booster. The int…

In the SpaceX feed they were waiting for the second stage to separate and light, and it didn't do either. So first question is why didn't it separate?

T+00:16 - Shortly after liftoff, when the engine graphic first appears, three engines were out. https://youtu.be/-1wcilQ58hI?t=2721

T+00:28 - Sparks are seen in the engine exhaust and some flashes. https://youtu.be/-1wcilQ58hI?t=2733

T+00:40 - A fourth engine is marked out. https://youtu.be/-1wcilQ58hI

T+01:02 - A fifth engine is marked out (just after the announcer says "we're throttled down and throttled back up") https://youtu.be/-1wcilQ58hI?t=2766

T+01:08 - More sparks (streaks) come from the engine https://youtu.be/-1wcilQ58hI?t=2773

T+01:16 - There is a shot of the aft of the rocket and it looks like six engines are out https://youtu.be/-1wcilQ58hI?t=2781

T+01:19 - MaxQ is called https://youtu.be/-1wcilQ58hI?t=2783

My totally uninformed speculation is that the first stage did not achieve the target velocity (and trajectory?) due to the 6(?) engine failures so the first stage continued to burn and the second stage never separated because the separation conditions were not met (velocity/trajectory).

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#818

Post by outworlder »

JumpCrisscross wrote: post #697
outworlder wrote: post #481

Earlier quoted context omitted.

The thing that bothers me about this rapid unplanned disassembly development methodology is all the environmental damage that this thing is doing. It was bad enough blowing up next to a wildlife preserve, but now they are (with some degree of certainty) blowing it higher up and scattering fragments across a huge area. The rockets are not getting any smaller. > so the only way to test x is with a starship on top. Why…

> couldn't they have delayed and tested when they had a more reasonable chance of success Probably not. These are new designs. Modelling only goes so far. The way you learn is testing, refining and repeating. I frankly didn’t expect it to clear the tower; max Q on the first shot is a testament to how far computational methods have come.

> These are new designs. Modelling only goes so far.

It went pretty far in the case of the SLS.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#819

Post by wahern »

marktangotango wrote: post #809
mrandish wrote: post #731

Earlier quoted context omitted.

There were multiple unexpected "energetic events" seen by observers apparently due to some of the engines failing around liftoff. These "energetic events" could have contributed to greater than expected downward force under the launchpad. If correct, it seems positive that the excess energy was directed downward still permitting the liftoff. That the ship was able to continue the flight through Max-Q and up to MECO a…

> I believe they've already started construction of upgraded launch facilities which include fire trenches and water deluge systems. Ah, so excavating the launch tower was intentional; demo tower 0.1 to make room for tower 0.2!

"test-to-failure" means that when you realize you may have made a mistake, you don't automatically scrap all your work to fix the mistake before continuing down the development path. You complete that prototype and test it because there are a thousand more mistakes to discover. Even if the known mistake will for sure result in a catastrophic failure, there may still be a large window of opportunity for productive mistake discovery before that for-sure failure ends that test run. You want to discover and fix mistakes in parallel, not serially.

Obviously there are judgment calls for when a mistake might prove too costly even in a test run. But manifestly SpaceX has damn good judgment in that regard. If you don't like how the sausage is made, just avert your eyes; don't complain about how ugly the sausage making process is.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#820

Post by outworlder »

chasd00 wrote: post #740
outworlder wrote: post #481

Earlier quoted context omitted.

The thing that bothers me about this rapid unplanned disassembly development methodology is all the environmental damage that this thing is doing. It was bad enough blowing up next to a wildlife preserve, but now they are (with some degree of certainty) blowing it higher up and scattering fragments across a huge area. The rockets are not getting any smaller. > so the only way to test x is with a starship on top. Why…

this was a test, they didn't have anything left to test except for a flight. delaying would be pointless, everything else had already been tested. edit: one other thing, they crashed and burned a lot of starships too. I don't see this being that different it's just bigger.

> this was a test, they didn't have anything left to test except for a flight. delaying would be pointless, everything else had already been tested.

Apparently not, since:

1) the launch site was damaged

2) several engines did not work

3) the RUD

I'd say, there's plenty that they could have tested before launching.

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