Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

SpaceX SN9 Explodes on Landing

twitter.com

Post reply on HN
Print view View original

91–100 of 317 posts

Re: SpaceX SN9 Explodes on Landing

#91

Post by GizmoSwan »

reasonabl_human wrote: post #81
GizmoSwan wrote: post #58

Earlier quoted context omitted.

You loved the quality of the explosion. Did you? Bigger the explosion, the more promising is the venture! NOT

I loved the explosion. These guys get stuff done. Move fast and break things

It should not have been an experiment leading to explosion at this stage.

You are not seriously willing to justify the explosion, are you? I hope that you are being sarcastic.

The experimental flying of rockets of this size are the 1960s thing. They should have acquired proper specs by now.

Re: SpaceX SN9 Explodes on Landing

#92

Post by waiseristy »

willyt wrote: post #69
waiseristy wrote: post #24

Earlier quoted context omitted.

These smart people did not have any semblance of control in the USSR. The Soviet space program was 95% political, heavily influence by the politburo and Soviet interests. Smart people would not have developed the Buran if all options were on the table

Surely that’s the same with NASA pork barrel politics affecting who gets to build it and therefore the particular companies and manufacturing capabilities the engineers have to work with. The space shuttle wasn’t engineering lead either.

Exactly. Funny how similar the two space programs were when it came to their political, uh, troubles.

Re: SpaceX SN9 Explodes on Landing

#93

Post by jzer0cool »

(1) I think that is a "hard" landing ;) I say it it the mark.

(2) The Question: I ain't no rocket scientist, but even if the engine failure had turned on, did the engines all just turn on quite late?

Just trying here some crazy college physics so not sure if this checks out but, here goes. Again, just for fun. If it takes X: (summation of thrust) to fly that high over x seconds, then it would take the X + some at the very last 4 seconds I saw engines turn on for soft landing.

Are we capable of having enough thrust in the last 4 seconds? Maybe try earlier so there can be more lead way in case of failure?

===

Freefall: 11:06 (all estimates) 12:45 (still free fall, engines off and preparing for vertical) 12:48 (engine on, flipping for vertical) 12:50 (vertical) (4 seconds left to apply thrust) 12:54 (crash landing)

I have about 104 seconds of free fall, and 4 seconds left when engine turned on.

Is 4 seconds enough? Just intuition and genuinely wondering ...

Just for fun - does my physics checkout (at freefall)?

vf = 0 + (1/2) * at^2 vf = 9.8m/s^2 (108s^2) = 57153.6 m/s = 127848.9621 mi/hr (yea, ignoring at moment drag/terminal, physics ;)

===

vf = (1/2) (F/m)t^2, F=ma (vf2m) / t^2 = F (Thrust required)

Again, just for fun. Don't kill me. Physics, it been a long time. If it's right, Elon, are you hiring?

EDIT: SpaceX, Tesla to the -moon- mars!

Re: SpaceX SN9 Explodes on Landing

#94

Post by [deleted] »

omgwtfbyobbq wrote: post #71

Can they relight sooner to improve their odds of landing successfully, or is the window for when they can relight relatively small? Or does it not matter because a few more seconds won't increase the chances they'll be able to relight?

[deleted]

Re: SpaceX SN9 Explodes on Landing

#95

Post by Me1000 »

phkahler wrote: post #66

Soon after SN8 Elon tweeted that they knew the problem. So they quickly added Helium to pressurize SN9, which is a bandaid given their deliberate elimination of Helium and the fact there isnt any on Mars. Now we see what looks like even worse relight capability. I wonder if recent departures are related in some way. They failed plenty before, but this seems different.

That's a lot of speculation. We don't yet know why one of the Raptor engines failed to relight. The Raptor is a very new engine with only a handful of minutes of flight time. Keep in mind they also replaced a couple of the engines before the flight. I imagine SpaceX still be considers them development engines.

You can also see some debris fly off of the bottom of the rocket just as it's performing its flip maneuver.

With SN8 Musk tweeted casually about it, but he's apparently taking a hiatus for a bit.

Re: SpaceX SN9 Explodes on Landing

#96

Post by DennisP »

Alupis wrote: post #85
elmomle wrote: post #62

Earlier quoted context omitted.

Plenty of American rockets failed, especially early on! https://www.youtube.com/watch?v=13qeX98tAS8

*While building the first space rockets in the world, literally making it up as they went. That's not quite the same situation SpaceX is in right now.

Actually it is the same situation. The launch was fine. What blew it up is something nobody has attempted before.

Re: SpaceX SN9 Explodes on Landing

#97

Post by ctdonath »

GizmoSwan wrote: post #91
reasonabl_human wrote: post #81

Earlier quoted context omitted.

I loved the explosion. These guys get stuff done. Move fast and break things

It should not have been an experiment leading to explosion at this stage. You are not seriously willing to justify the explosion, are you? I hope that you are being sarcastic. The experimental flying of rockets of this size are the 1960s thing. They should have acquired proper specs by now.

SpaceX Starship is way outside established industry specifications.

Re: SpaceX SN9 Explodes on Landing

#98

Post by jjoonathan »

ggreer wrote: post #83
fpgaminer wrote: post #37

Earlier quoted context omitted.

But the U.S. has sent 3x as many citizens into space: https://en.wikipedia.org/wiki/List_of_space_travelers_by_nat... So combining with your statistic the U.S. has a fatality rate of 4.4% versus Russia's 3.3%. Given the low N it's probably within margin of error.

At least 60 of those Americans were sent up on the Russian Soyuz: https://en.wikipedia.org/wiki/List_of_Russian_human_spacefli... Also, How are you doing the math to get a 4.4% fatality rate? The numbers are much lower than that. Soyuz has launched 394 people and killed 4 of them. The most recent fatality was 50 years ago. The Shuttle launched 833 people and killed 14 of them, most recently in 2003 (8 years before th…

Of course proving a simple design and sticking with it is safer! Not going to space and being content with remaining on the ground is safer still! Water is wet! The sky is blue!

We can all see what happened: the soviets stopped spending money on innovation and tried to re-frame their stagnation as operational brilliance. Sure, Soyuz has a reliability niche, and I'd rather ride on it too, but I'd rather fund efforts to advance space exploration, even if they wind up being a clusterfuck like the shuttle.

Re: SpaceX SN9 Explodes on Landing

#99

Post by avmich »

hyperion2010 wrote: post #88
aeternum wrote: post #73

Earlier quoted context omitted.

The issue is that the Raptor engines can only throttle down to 40% which represents a large thrust-to-weight ratio when you have basically just an empty tank. There is also a startup time for each engine, so if one fails Starship will likely hit the ground before they can light another. There are enough engines that a failure on ascent can be handled gracefully but landing is another story.

Ah ok, this sort of clarifies the issue, which is that you can't really run more engines at lower thrust, and if you deal with the tank pressure issues from S8 then I imagine it should be able to go down on 2 engines alone without catastrophic issues. With respect to failure on ascent, I imagine in that case they just send up another starship and transfer in orbit (coming down has always been the hard part).

There could be a delicate dance somewhat similar to what Soviet lunar lander was planned to do at launch: start all engines, and if all is well, shut down those backups. Here with Raptors one could imagine launching two engines, but if one runs well - during the startup sequence - shut the other down mid-sequence.

But this is totally question to Raptor creators. Might be not really feasible or even meaningful.

Re: SpaceX SN9 Explodes on Landing

#100

Post by onethought »

jzer0cool wrote: post #93

(1) I think that is a "hard" landing ;) I say it it the mark. (2) The Question: I ain't no rocket scientist, but even if the engine failure had turned on, did the engines all just turn on quite late? Just trying here some crazy college physics so not sure if this checks out but, here goes. Again, just for fun. If it takes X: (summation of thrust) to fly that high over x seconds, then it would take the X + some at the…

I think they are doing it the most efficient way (similar to the Falcon 9) - that is with 0 hover.

The timing doesn't mean much because an entire engine didn't light... so it would have flipped up right faster and slowed down faster. Timing on a failure case doesn't really work.

Also it was only 1 engine compared with two, they could gimbal independently and have one course correcting while the other decelerates

Post reply on HN