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SpaceX SN9 Explodes on Landing

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Re: SpaceX SN9 Explodes on Landing

#251

Post by minikites »

naikrovek wrote: post #162
minikites wrote: post #159

Earlier quoted context omitted.

Why is SpaceX making the same mistakes 70 years later?

I don't recall NASA ever doing a rocket landing so I'm not sure which mistakes you are seeing repeated.

NASA did rocket landings on another planet with 1970s technology: https://en.wikipedia.org/wiki/Viking_program#Entry,_Descent_...

>At an altitude of about 1.5 kilometers (5,000 feet), the lander activated its three retro-engines and was released from the parachute. The lander then immediately used retrorockets to slow and control its descent, with a soft landing on the surface of Mars.

Re: SpaceX SN9 Explodes on Landing

#252

Post by Cogito »

Layke1123 wrote: post #238
alentist wrote: post #219

Earlier quoted context omitted.

> 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 societ…

Well, why did the US actively try to harm the USSR? If it was such a bad way of doing things, why did the US actively go out of it's way to sabotage it rather than just ignore it and let it die?

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 sustained differences in accomplishments come down primarly to the amount of resources each were able to devote to space. The US was able to sustain a high level of investment for a long time, and the USSR was not.

Re: SpaceX SN9 Explodes on Landing

#253

Post by rurban »

Layke1123 wrote: post #48
rurban wrote: post #42

Earlier quoted context omitted.

It's more funny that both primarily used thousands of Germans as their rocket technicians, and both german parties used their german style, based on engineers as heads. This all changed with Lyndon Johnson taking over, getting rid of the Germans, introducing the well known inefficient NASA/gov-style management style known from the Shuttle era, and moved the technicians out of Alabama to Houston. This was the anti-mod…

I have watched PMs actively contribute nothing to a project by entering false metrics. It really is either you can build something, or you can't and contribute nothing to the project.

Well, those managers are only there for the hype. You need liars apparently. I can name a couple of popular of software projects who went this route, and were successful because of this. But NASA?

Re: SpaceX SN9 Explodes on Landing

#254

Post by emilecantin »

GizmoSwan wrote: post #105
avmich wrote: post #101

Earlier quoted context omitted.

You can choose to develop rockets - especially of such size - this way instead of putting (much) more efforts in calculating how it would behave and prepare for all cases.

Nasa did the calculation with with ancient computers and these guys are speculating and not using proper technology to achieve success. It makes no sense in 2021. They should not be experimenting. Their simulations should be been solid before this stage. It is good way to burn cash.

SpaceX does do simulations, and tons of it. SN8 and 9 wouldn't have performed that well during the descent stage without amazing guidance software, which could only have been developed through extensive simulations.

Simulations are always going to be "assume a spherical cow in a vacuum" to a degree, as the real world is unbelievably complex, and you have to use models at some point. These models _can_ be wrong, and the only way to test them is through experimentation.

Re: SpaceX SN9 Explodes on Landing

#255

Post by BurningFrog »

bvm wrote: post #118
BurningFrog wrote: post #87

I'm very impressed by how it's coasting on the fins down the atmosphere. I had never even heard that idea discussed before I saw SN8 do it. Of course, they'll have to land some other way on Mars or the Moon.

it will be coasting on its fins during atmospheric entry for mars EDL. (Old-ish) video simulation here: https://www.youtube.com/watch?v=xDTZEVMArBE That phase wipes off >99% of the total energy required to get to 0 m/s, which is pretty remarkable because Mars' atmosphere is ~1% of Earth's.

Wow. That's very far from what my intuition would guess.

Good thing we have physics and math :)

Re: SpaceX SN9 Explodes on Landing

#256

Post by Layke1123 »

rurban wrote: post #253
Layke1123 wrote: post #48

Earlier quoted context omitted.

I have watched PMs actively contribute nothing to a project by entering false metrics. It really is either you can build something, or you can't and contribute nothing to the project.

Well, those managers are only there for the hype. You need liars apparently. I can name a couple of popular of software projects who went this route, and were successful because of this. But NASA?

Not always. Some of the software guys just zone out in meetings and don't pay attention while their managers and PMs do the talking. Can confirm, I wasn't paid nearly enough in that job to care about what my manager or PM said.

Re: SpaceX SN9 Explodes on Landing

#257

Post by evgen »

sudosysgen wrote: post #248
alentist wrote: post #219

Earlier quoted context omitted.

> 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 societ…

A significant reason why Stalin was able to successfully rise to power and why the Bolsheviks were able to secure total power is because of foreign violence and interference. When all major foreign powers say that they wish for the destruction of your country and would openly prefer you to go back to more suffering, support for monsters like Stalin increases. Equally, when the threat of invasion is as high as it was…

It takes a profoundly ignorant view of historical facts to blame Stalin and Trotsky on foreign interference.

Re: SpaceX SN9 Explodes on Landing

#258

Post by avmich »

simonh wrote: post #233
avmich wrote: post #203

Earlier quoted context omitted.

> but I've never quite been satisfied with the "if we're thinking of it then they probably already tried it" explanation :) Same here :) . I'm still unhappy with their decision to use toxic propellants on Crew Dragon - I'm sure they could use something much more benign.

To be fair they selected it quite some time ago now. There's a lot of very promising research now though, so hopefully they will have better options available down the line.

> To be fair they selected it quite some time ago now.

They've had better fuel options from the very beginning. I guess they didn't have space cycles to additionally solve this issue; hope they'll come back to it.

Re: SpaceX SN9 Explodes on Landing

#259

Post by sudosysgen »

evgen wrote: post #257
sudosysgen wrote: post #248

Earlier quoted context omitted.

A significant reason why Stalin was able to successfully rise to power and why the Bolsheviks were able to secure total power is because of foreign violence and interference. When all major foreign powers say that they wish for the destruction of your country and would openly prefer you to go back to more suffering, support for monsters like Stalin increases. Equally, when the threat of invasion is as high as it was…

It takes a profoundly ignorant view of historical facts to blame Stalin and Trotsky on foreign interference.

It takes a profoundly ignorant view of historical facts to ignore the immense pervasiveness of foreign interference in the Russian Civil War.

The mere presence of the Bolsheviks as a dominant force was due to foreign interference, as the Germans installed him and his friends in an attempt to destabilize the Russian Empire.

Trotsky's growth in authoritarianism, when he was previously a moderating force, started with the opportunistic German attacks at the fleets of the Red Army, and of course his rise to power from a middling figure to a preeminent Bolshevik was only made possible by German incitement of the Bolshevik movement to begin with.

Even Stalin's justification for power was based on (justified) appeals to centrally planned heavy industries, whose main motivation was military power which was necessary to to threats of invasion.

It is clear to anyone that both Stalin and Trotsky would have had much, much less power if they weren't able to justify centralization on the necessity to resist foreign agression, beyond that the consolidation of the Bolsheviks to begin with was a German plot.

Re: SpaceX SN9 Explodes on Landing

#260

Post by simonh »

Cogito wrote: post #249
simonh wrote: post #246

Earlier quoted context omitted.

Oh come on, the Dragon capsule brings people back to the ground, not the first stage booster and it's landing these things that is the issue so far, not launching them. All I am saying is that this vehicle, in it's final qualified form, will be landing human beings on the deck back here on Earth. That's the objective, so it's viability and reliability needs to be considered in that context. For an F9 first stage a fa…

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.
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