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SpaceX SN9 Explodes on Landing

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Re: SpaceX SN9 Explodes on Landing

#291

Post by sudosysgen »

naikrovek wrote: post #283
sudosysgen wrote: post #278

Earlier quoted context omitted.

Failing to restart an engine in a retrograde trajectory. A difficult task that both the Soviets and NASA (and Arianespace and the Chinese) had issues with, but worked out. It's very difficult because of the turbulent airflow in an engine bell pointed against the airspeed vector. Despite this, many rocket engines can do it reliably.

> Failing to restart an engine in a retrograde trajectory That's not a failure, that's the effect of some upstream failure. What failure are they repeating? Pumps sized too small? Improper torquing? You talk like you know the details, so share them.

There are a lot of reasons for which an engine would fail to start in such a scenario. They all boil down to the turbulent airflow and high pressure in the nozzle inhibiting the ignition process.

How exactly you decide to fix it depends on many things. It's impossible to tell. But they are all downstream of the same failure, which is overcoming the high pressure and turbulent flow.

Re: SpaceX SN9 Explodes on Landing

#292

Post by alentist »

sudosysgen wrote: post #285
alentist wrote: post #281

Earlier quoted context omitted.

GP: They did not have a wonderful society. It was very deficient in many ways. I didn't argue that point because we agree. You: Exactly! Glad you also agree with my comments, then.

You're the one that replied to >The USSR, had it not had to fight a cold war against the US, could very well have been a much better system not just for space flight, but for a way to structure and run society in general. thus implying disagreements. Since neither of us have contradicted such a statement, either you've been replying hors-sujet or you were just trying to show agreement, right?

Huh?

Re: SpaceX SN9 Explodes on Landing

#293

Post by Cogito »

Layke1123 wrote: post #273
Cogito wrote: post #252

Earlier quoted context omitted.

This is moving the goalposts. It's possible that the USSR would have been a better system, had the cold war not happened, but that's not the world we live in. If you want to make that argument you have to explain why it's reasonable to excuse how the USSR turned out in reality, and why in your hypothetical world it would have turned out differently. With respect to space advancement, I suspect the main reason for sus…

It's not moving to goalposts to acknowledge that the USSR beat us to space and that a large part of their collapse was due directly to the influence of the US.

Upthread there was a claim by evgen that the way the US vs Soviet approach to the space race had been characterised by mempko was incorrect, and that the current safety of the Soyuz was (at least in part) paid for with the lives of cosmonauts.

You go on to state that Russia beat the US into space (which is a non-sequitur), and later expand that "The USSR, had it not had to fight a cold war against the US, could very well have been a much better system not just for space flight, but for a way to structure and run society in general."

When challenged by alentist, who asked "why did the USSR and its satellite states have to systematically mass murder people who wanted to leave this wonderful society?" you countered with "If it was such a bad way of doing things, why did the US actively go out of it's way to sabotage it" which is moving the goalposts, and starts to slide into whattaboutism.

Specifically you claimed that the USSR "could very well have been" a better way to structure a society, and alentist provided strong evidence that it was not - people were murdered when they tried to leave. Instead of trying to prove your point you deflected, and shifted the goalposts from "this could very well have been a good system" to "the US didn't like it therefore it couldn't have been bad".

Re: SpaceX SN9 Explodes on Landing

#294

Post by imglorp »

yellowapple wrote: post #189
imglorp wrote: post #177

Earlier quoted context omitted.

Neat, seems pretty much any mistake results in a fireball. Scott Manley and daughter have a fun song about other failures, "You will not go to space today", https://www.youtube.com/watch?v=Ayu0GsrvKQA I'm guessing the title is probably an allusion to this https://xkcd.com/1133/ .

I was half expecting: "If an O-ring gets a bit too cold, you will not go to space today" ...but I guess that's a bit too dark, eh?

"If your rocket runs at all engine rich, you will not go to space today..."

Re: SpaceX SN9 Explodes on Landing

#295

Post by Cogito »

simonh wrote: post #260
Cogito wrote: post #249

Earlier quoted context omitted.

I mostly agree with you, but I'm not sure on why you're focusing human passenger safety on this at this early development stage, as if it's somehow a reasonable thing to focus on. Launching these things IS the issue so far, by far the main objective of these tests. Landing them would be nice, but the primary objectives are to launch the whole thing (in particular including aero surfaces and multiple engines, as compa…

I suppose that’s fair, but I think public perception might be a bit different. The public aren’t used to watching prototype jet airliners crashing in flames on runways, so some people are going to be concerned about it.

Completely agree, and the messaging is really hard to get right.

They are doing these dramatic tests out in the open which sure gets a lot of attention, but there is a real risk of reputation damage or fodder in the hands of their competitors lobbyists.

I don't know a good way to resolve that, but I certainly prefer the current approach and trust that anyone who really cares about the safety will be able to understand what's important about these tests and what isn't.

Even on the crappy morning news here, where they certainly gave a lot of airtime to the fireball, they had an expert on who focused on what the test was aiming to achieve. There certainly was no focus on the idea that Starship is intended to eventually carry passengers (even though they mentioned it alongside stock renders of Starship going to mars and the moon).

Re: SpaceX SN9 Explodes on Landing

#296

Post by nielsole »

yellowapple wrote: post #191
jacquesm wrote: post #80

Earlier quoted context omitted.

That's a good question actually, given that they had another engine as well. Or maybe light up all three and then shut down the one they decide not to use. But these are all in the 'why don't they' category, SpaceX has some pretty clever cookies, experts in their field, the chances that anything we can think of has not been thought of by them are nil.

I'm reminded of the story of two economists walking down the street. One sees a dollar bill on the ground, and the other decides "that can't be right; if there was a dollar bill on the ground someone would've picked it up already". Not saying that a bunch of random folks on HN are seeing dollar bills in this analogy, but I've never quite been satisfied with the "if we're thinking of it then they probably already trie…

"Question: Why only light 2 engines for landing? Any engine failure means loss of vehicle, so you have two single points of failure. Why not light all 3, do the flip, then pick the best two and turn off the other?"

"We were too dumb" https://twitter.com/elonmusk/status/1357256507847561217

Re: SpaceX SN9 Explodes on Landing

#297

Post by Layke1123 »

alentist wrote: post #289
Layke1123 wrote: post #287

Earlier quoted context omitted.

So you agree, capitalism has been responsible for slavery and mass murder?

Not at all. That's nonsense. Now, can you please answer the question you keep dodging? If the USSR had such a wonderful society, why did they have to systematically mass murder ordinary people who wanted to leave this wonderful society ?

The US fought an actual civil war over the right to OWN people. How is capitalism, THE economic system the US has used since it's inception, not responsible for that, as well as the current demand for slave labor that exists today? I will answer your question when you can answer that one honestly.

Re: SpaceX SN9 Explodes on Landing

#298

Post by Layke1123 »

alentist wrote: post #290
Layke1123 wrote: post #288

Earlier quoted context omitted.

Lol we didn't agree mate but way to try and take a quick win by "selectively" ignoring the parts you don't want to quote.

> Lol we didn't agree mate Your comment says otherwise.

No, my comment agreed with the idea that the US is the most significant factor responsible for what happened in the USSR.

Re: SpaceX SN9 Explodes on Landing

#299

Post by alentist »

Layke1123 wrote: post #297
alentist wrote: post #289

Earlier quoted context omitted.

Not at all. That's nonsense. Now, can you please answer the question you keep dodging? If the USSR had such a wonderful society, why did they have to systematically mass murder ordinary people who wanted to leave this wonderful society ?

The US fought an actual civil war over the right to OWN people. How is capitalism, THE economic system the US has used since it's inception, not responsible for that, as well as the current demand for slave labor that exists today? I will answer your question when you can answer that one honestly.

To our fellow readers: Notice how Layke1123 has dodged my original question no fewer than 4 times (!), all while continuing to launch barrages of new questions in an effort to derail the conversation and avoid having to answer it. This tactic has a long history in Soviet propaganda.

Let's try again:

If the USSR had such a wonderful society, why did they have to systematically mass murder ordinary people who wanted to leave this wonderful society?

Don't deflect. Don't evade. Answer.

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