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SpaceX SN9 Explodes on Landing

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Re: SpaceX SN9 Explodes on Landing

#211

Post by avmich »

GizmoSwan wrote: post #134
avmich wrote: post #132

Earlier quoted context omitted.

No. It's way easier today to test than to solve that problem.

They will get a single rocket from that ideology and get stuck again in the loop later on with any big modification.

Falcon 9 now flies and lands with no crashes, especially comparing to expendable rockets. Of course a modification big enough will require changing control parameters, but that's a routine task for engineering.

Some day we'll have good enough models for air flows in all necessary modes and good enough computers to run those models; we aren't there yet. Testing is still required.

Re: SpaceX SN9 Explodes on Landing

#212

Post by avmich »

smattiso wrote: post #167

Is this a viable landing strategy in the long run? Both SN8 and SN9 landings have ended in total fatalities. What happens if the landing happens to occur during a 50 mph wind gust, etc. If this maneuver isn't designed to be 100% fault tolerant maybe they need to be thinking about an emergency eject? I like the simplicity of the Starship design. How much extra weight would a nosecone eject + parachute add?

> Is this a viable landing strategy in the long run?

I prefer Dream Chaser's approach, but Elon Musk has his own ideas. Together with SpaceX team. Of course to fly to the Moon there are no such options.

Re: SpaceX SN9 Explodes on Landing

#213

Post by WalterBright »

bernulli wrote: post #207
WalterBright wrote: post #206

Earlier quoted context omitted.

The F1 is a bigger (!!) version of the same engine. It's got the same crucial features: 1. turbo-pumps 2. the nozzle is cooled and the fuel warmed by making the nozzle out of tubes through which the fuel passed 3. holes drilled in the tubes so fuel leaked into the combustion chamber to provide boundary layer cooling I think the pogo-ing was solved the same way, too - putting baffles in in various places.

By that logic essentially all cryogenic engines are “the same”.

In a similar vein, all modern jet engines can trace their core features back to the Ohain engine (not the Whittle engine).

Re: SpaceX SN9 Explodes on Landing

#214

Post by avmich »

new_realist wrote: post #165

Feynman on SpaceX’s “Big Bang” design approach. I don’t think he would have been a fan: The usual way that such engines are designed (for military or civilian aircraft) may be called the component system, or bottom-up design. First it is necessary to thoroughly understand the properties and limitations of the materials to be used (for turbine blades, for example), and tests are begun in experimental rigs to determine…

> It has a greater ratio of thrust to weight than any previous engine.

SSME thrust-to-weight ratio: 73.1 https://en.wikipedia.org/wiki/Space_Shuttle_Main_Engine

NK-33 thrust-to-weight ratio: 137 https://en.wikipedia.org/wiki/NK-33 (no gimbaling)

RD-270 thrust-to-weight ratio: 189.91 https://en.wikipedia.org/wiki/RD-270

Re: SpaceX SN9 Explodes on Landing

#215

Post by unanswered »

hyperion2010 wrote: post #186
unanswered wrote: post #120

Earlier quoted context omitted.

> because it sure seems like they can't deal with losing even a single engine Define "deal with". This rocket did 100% of what any rocket was ever supposed to do, before SpaceX came along and redefined what a rocket is supposed to do: go up.

"Deal with" == "Not blow up" == "No RUD" in the event of a single engine failure. Manned space flight kind of has this kind of important additional requirement that things like ICBMs don't, which is that they can't just "go up" the have to come back down and not end in a ball of fire.

Unless I am much mistaken what what blew up was a first stage, not a manned stage. I do not believe that SpaceX plans on doing suicide burns to retrieve humans from flight.

Re: SpaceX SN9 Explodes on Landing

#216

Post by HarryHirsch »

avmich wrote: post #201
HarryHirsch wrote: post #158

Earlier quoted context omitted.

Today's crash was due to failure of one engine to restart. Briz and Fregat Russian upper stages are routinely restarted, with ~ 98 % success, same with Ariane EPS and Chinese Yuanzheng. It's doable, just not for Space-X.

Briz and Fregat start much smaller - 20 kN - engines with no time constraints, while Starship re-lights 2200 kN engine and rocket immediately does rotation by 90+ degrees, and time is of essence.

Where do thrust and chamber pressure even come into the equation? It's not that the engine exploded, the thing failed to ignite.

Re: SpaceX SN9 Explodes on Landing

#217

Post by elihu »

smattiso wrote: post #167

Is this a viable landing strategy in the long run? Both SN8 and SN9 landings have ended in total fatalities. What happens if the landing happens to occur during a 50 mph wind gust, etc. If this maneuver isn't designed to be 100% fault tolerant maybe they need to be thinking about an emergency eject? I like the simplicity of the Starship design. How much extra weight would a nosecone eject + parachute add?

It looks like both of these particular failures are engine-related, rather than air turbulence. (SN8: lost fuel pressure, SN9: failed to start one engine for unknown reasons.) These are engineering problems that probably have relatively straightforward solutions.

It is a fair point though, that landing in less-than-ideal weather conditions should perhaps be thoroughly tested. Launches generally can be done when conditions are optimal, but it might not always be possible to defer a re-entry until weather improves.

Ideally the lander would have real-time high-resolution air velocity data in the vicinity of the landing pad and would adjust its maneuvers to compensate.

I wonder what SpaceX's current tolerances are for wind for Falcon 9 landings? I assume anything more than a light breeze and they put it off for another day, but maybe those rockets are heavy enough that the wind doesn't knock them around as much as one would expect. (Droneship landings are especially difficult with wind plus a rocking boat.)

Re: SpaceX SN9 Explodes on Landing

#218

Post by GizmoSwan »

nickik wrote: post #178
GizmoSwan wrote: post #145

Earlier quoted context omitted.

You can't say a lot of things, so what! Giant team is not prerequisite for doing proper simulation before launching a gigantic rocket. I am being sincere. Nasa is in fact leading you on, to have some of their people wasting their time on this pseudo venture for optics. You seem to be using faith as your guiding light too rather than reason. It is not a prototype bicycle for experimental launch. It is all evident from…

You are so confident in your opinion and you are so incredibly wrong. Pretty much every NASA engineer that has worked with SpaceX has been incredibly impressed by their methods. Literally every single one of their competitors, including nation states have started to change their who launch strategy because they saw no other way to compete with Spacex (and they are still failing) all of them have expressed how impress…

I just want to know how you know that "you" are incredibly right in this. You are just speculating like everybody else here. There is no quality or quantitative measurement available here for you to make these absolute statements. The only thing that I can gather from your text is that a lot can go wrong in fact.

Having the prototype that is exploding is NOT fine at this stage and that is "my" opinion. Your opinion is yours alone.

You are basically claiming your analysis is indisputable and that it has to be accepted and your belief in people's intelligence makes it so and I am stupid because you believe that they are smarter.

It is not matter of getting it right the first time and improvements in parts and efficiency. It is about having it never explode after the first round.

I don't care who you believe they are beating in the market place and how magnificent you believe this rocket is.

Good luck if you are associated with this venture. If so you are allowed to pump it.

Re: SpaceX SN9 Explodes on Landing

#219

Post by alentist »

Layke1123 wrote: post #168
avmich wrote: post #109

Earlier quoted context omitted.

I was confused by "Russia didn't beat US into space" - you probably meant "to the Moon" (manned flights), while USSR had quite a few space firsts.

No, I meant that the above response calling the other user wrong is wrong itself. 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. But yet, if I say this, I will be immediately downvoted because if I suggest that anything other than the established order in the US is the best sy…

> 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.

What makes you think that? If they had such a wonderful "way to structure and run society in general", why did the USSR and its satellite states have to systematically mass murder people who wanted to leave this wonderful society?

[0] https://en.wikipedia.org/wiki/Emigration_from_the_Eastern_Bl...

[1] https://en.wikipedia.org/wiki/Schie%C3%9Fbefehl

[2] https://en.wikipedia.org/wiki/Mass_graves_from_Soviet_mass_e...

[3] https://en.wikipedia.org/wiki/NKVD_prisoner_massacres

[4] https://en.wikipedia.org/wiki/Holodomor

Re: SpaceX SN9 Explodes on Landing

#220

Post by modeless »

Retric wrote: post #199
modeless wrote: post #195

I don't see how this could ever be as reliable as an airliner for passenger service as SpaceX has been talking about. An airliner can land safely with no engines and even no landing gear if necessary (and it sometimes is).

It’s total safety that’s important not individual aspects of safety. Clearly there are many disadvantages, but when comparing it to 15 hour flights there are several advantages. For example shorter flight times mean fewer chances for in flight human errors. Another is in flight medical emergencies can be more quickly reach a hospital. A few aircraft have been shot down which is again much less likely, etc etc. Initia…

One aspect can ruin the total safety. It can't be more safe than the least safe part of the trip. Sure, maybe in 50 years we'll figure out something better. But SpaceX is talking about flying long haul Earth to Earth routes with Starship, not a hypothetical future craft.
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