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Comment by jml7c5 | Hacker News Reader

From what I've read, the booster was intentionally being tested to its limits — an explosion isn't necessarily unexpected. They weren't aiming to catch it, it was being ditched in the ocean. Whether this counts as a "true" booster failure depends on exactly what failed.

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They planned to complete the landing burn but it looks like the booster exploded at the beginning of the landing burn so I wouldn't say it was completely successful.

Sure, but this test was basically "let's see if we can put this thing under enormous stress to simulate a worst case scenario and find out if it survives or not"

Exactly. They're still exploring limits and failure modes. Hence the effort to re-fly a used booster on an aggressive trajectory when they have multiple newer revisions ready to go. Looking forward to the first launch with Raptor 3.

Also really can't understate the importance of Starlink in the development program. Apollo jettisoned parachuting return capsules from the interstages so that engineers could get camera footage from inside the rocket during launch. SpaceX just gets an RTSP stream (or something similar).

It's the original definition of "pushing the envelope." You start with a known flight envelope, then push a little past that. Sometimes you learn that the real envelope is bigger than you thought. Other times you find that the envelope is exactly where you thought it was.

I notice I mis-typed and should have said you can't overstate the importance of Starlink on the development program. And I agree with you about pushing the envelope. It was really interesting to hear that they were planning on testing an engine-out scenario with this booster by lighting one of the middle 10 engines and two centers. If they can pull that off, they'll have a measurable increase in fault tolerance over Falcon 9.

is igniting the engine pushing the envelope though?

We don't know all the things they did to the Booster, but among them were deliberately not igniting some engines as well as taking a more aggressive angle-of-attack on descent (the rocket is a fairly effective lifting body, as it turns out!).

There may be more things, but between those two I think the latter was a bigger problem. It would have gotten hotter and more physically stressed. And then weakened to the point to where re-igniting the engines caused it to fail.

They also used a new hot-staging maneuver, where the gases were directed out one side so that it flipped more rapidly in the other direction. It was a really fast flip! A rocket the size of a small skyscraper turning 90 degrees in just a few seconds. That could have jarred something loose, too.

Hopefully we find out in the post-mortem. SpaceX doesn't typically give the public as much detail as we'd like, but they're pretty good at sharing the high-level reasons why something failed.

>SpaceX doesn't typically give the public as much detail as we'd like

It gives magnitudes more details than anyone else.

ITAR unfortunately limits what can be publicly released.

What was unexpected was the lack of images during the booster reentry. And I don't know where this "exploded on impact" comes from - no evidence of this so far, that I noticed. It feels more like it didn't make it to the water in one piece.

Yeah, the video doesn't show it hitting the water at all. It looks like it exploded earlier on in the descent.

Yeah they were pretty clear about intending to fly it until it broke up so that they could understand how hard of a turn they could make in the future without it going splat into the tower.

From what I could gather from the commentary, they were pushing the limits of the booster's control capability. But the booster exploded on engine ignition. They are separate aspects, though they may be related. The commentators also sounded like they were not expecting a failure at that stage. So, concerns may be warranted.

An explosion can be fine, but the details really matter. The yardstick here is whether this iteration was better than the last, and the pace of progress if so.

I don't think this flight reassured anyone that the Starship program is making the improvements we'd expect.

I was watching Everyday Astronaut's feed and he seemed a little bummed. I don't follow SpaceX launches closely enough to know, but when they plan to "fail on purpose" do they not mention it ahead of time?

Of all people, I would expect him to know this sort of information ahead of time, although maybe the booster failure was planned but he was bummed about some some of the other things that didn't work well.

[1]: https://www.youtube.com/watch?v=T6tP0il4z64

It was mentioned ahead of time.

it was but it also failed much earlier than expected.

He was bummed about starship losing attitude control and failing to deploy the Starlink mockup satellites. Starship made it further than the two previous flights and progress is progress but being bummed is understandable.

Yea, the super heavy booster was flying a refurbished engine from a previous super heavy flight.

Explosion was probably expected.

The intended goal is to reuse those boosters, more than once, and without requiring weeks of inspection and maintenance.

(It's actually the entire booster reflying this time; the reflown single engine was in January).

Oh, so it's one of the two boosters they caught with the chopsticks?

Dang, that's actually quite insane.

Shame that block2/block3 starship is such a mess.

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