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Starship – SN9 – High-Altitude Flight Test

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Re: Starship – SN9 – High-Altitude Flight Test

#61

Post by numpad0 »

rbanffy wrote: post #26
djaychela wrote: post #8

It felt much less eerie as it had commentary this time (and probably because it wasn't the first Starship high-altitude flight), but on the face of it, it looked to be a rougher 'landing' than SN8. I'm sure they got a lot of data from it, but it looked like some of the debris was headed towards SN10 - definitely squeaky bum time then! Can't wait to see this work, though, it really will be a step change for space expl…

Win SN8 at least they had the engine firing itself through the nozzle. This time it seemed the others failed to start. Suicide burns are probably a very bad idea when they have crews and passengers anyway. I assume they'll fire up the landing engines sooner and leave enough time for the vacuum engines to fire as backups if needed.

Vacuum engines can’t be used at low altitudes, exhaust underexpansion cause flow to delaminate which will damage the nozzle which goes the way rocketry goes

Re: Starship – SN9 – High-Altitude Flight Test

#62

Post by Mountain_Skies »

bredren wrote: post #60
dgritsko wrote: post #13

I've been so conditioned by how flawless SpaceX launches have tended to be over the last few years. It's exciting going back to not knowing what will happen during the stream. I'm reminded of the enthusiasm around the early Falcon 9 first-stage landing tests, when folks were attempting to reconstruct individual frames of footage from the first "ocean landings" just to get a small taste of what happened. I'm sure they…

The day before the NASA-crewed SpaceX rocket launch, Starship SN4 blew up on the pad in a massive explosion in south Texas. I noticed the news barely covered it, and I thought at the time it might be to avoid casting doubt on the human-crewed launch. https://www.dallasnews.com/business/technology/2020/05/29/wa...

COVID19 and the riots were the big stories. Without them, doubt the media would have been able to resist the drama of astronauts possibly blowing up by connecting the two different rocket projects.

Re: Starship – SN9 – High-Altitude Flight Test

#63

Post by m4rtink »

natch wrote: post #54
le-mark wrote: post #38

Earlier quoted context omitted.

Seems like there are two different things here; launching passengers and freight, and returning passengers in comfort and without neck injuries. One could easily envision a passenger only winged glider similar to the space shuttle to serve the passenger return role. Indeed, although spacex has nothing like that planned, these BFRs enable damn near anything.

The atmosphere on Mars is not as thick as ours so there might be an issue with that winged glider vision. And then there is the moon...

Both have much weaker gravity though.

Re: Starship – SN9 – High-Altitude Flight Test

#64

Post by zaroth »

gvb wrote: post #33
guardiangod wrote: post #12

Looks like 1 of the engines failed to re-lit during the landing. At least this time 1 of the engines was functioning correctly all the way to the explosion. This is an improvement over SN8 where all the engines failed to re-lit properly.

It is interesting and informative to compare SN9 to SN8. SN8: https://youtu.be/ap-BkkrRg-o?t=6884 SN9: https://youtu.be/_zZ7fIkpBgs?t=704 With SN8, you can clearly see two engines lighting and burning properly until just before it (crash) lands. With SN9, you can clearly see one engine lighting and burning properly, but the second engine did not light cleanly and did not stay lit.

I don’t think that’s quite right. With SN8 they ended up with low pressure in the header tank and not enough fuel for the turbo pumps.

A so called “engine-rich” burn resulted, which is why there’s a flash of green flame.

Total thrust was much lower than spec, hence the hard landing even though both engines ignited.

Re: Starship – SN9 – High-Altitude Flight Test

#65

Post by [deleted] »

samcheng wrote: post #43
dgritsko wrote: post #11

Earlier quoted context omitted.

Yeah - it really looked like they just got lucky with the debris somehow avoiding SN10. I wonder what the reasoning was behind them even having SN10 on the other pad during this launch - surely it would have been safer to just keep it in a hangar until afterwards?

That opening shot with one spaceship launching while the other was still on the pad was priceless, though... and they are iterating so quickly that much of the value from SN10 was already gained in the manufacturing process.

[deleted]

Re: Starship – SN9 – High-Altitude Flight Test

#67

Post by stopChanging »

AnimalMuppet wrote: post #53
elihu wrote: post #36

Earlier quoted context omitted.

I think it was the opposite; they rotated past vertical. I'd guess they were probably counting on the vectored thrust of a second engine to halt the angular momentum.

Sure, could be. I'd like a few seconds earlier on the shot that showed the landing pad to be sure.

dodd's stream shows that more clearly https://twitter.com/Erdayastronaut/status/135674067395381658...

Re: Starship – SN9 – High-Altitude Flight Test

#68

Post by rbanffy »

numpad0 wrote: post #61
rbanffy wrote: post #26

Earlier quoted context omitted.

Win SN8 at least they had the engine firing itself through the nozzle. This time it seemed the others failed to start. Suicide burns are probably a very bad idea when they have crews and passengers anyway. I assume they'll fire up the landing engines sooner and leave enough time for the vacuum engines to fire as backups if needed.

Vacuum engines can’t be used at low altitudes, exhaust underexpansion cause flow to delaminate which will damage the nozzle which goes the way rocketry goes

They can't be used for long. The Raptor was test fired with the vacuum nozzle at sea level. Not perfect, but beats hitting the ground.

Re: Starship – SN9 – High-Altitude Flight Test

#69

Post by rbanffy »

_Microft wrote: post #41
rbanffy wrote: post #26

Earlier quoted context omitted.

Win SN8 at least they had the engine firing itself through the nozzle. This time it seemed the others failed to start. Suicide burns are probably a very bad idea when they have crews and passengers anyway. I assume they'll fire up the landing engines sooner and leave enough time for the vacuum engines to fire as backups if needed.

I think they will practice until they get the landing right all the time. The engines with vacuum optimized nozzles are not suited for landing. They can not be gimbaled and are very over-expanded as well. I would not be surprised if the engines with vacuum nozzles destroyed themselves if they were fired at sea-level.

The engines were tested at sea level with the vacuum nozzle. Not being gimballed is bad, but they are throttleable, at least.

All these crazy failure modes will have to be tested before Starship is human rated.

Re: Starship – SN9 – High-Altitude Flight Test

#70

Post by _Microft »

rbanffy wrote: post #69
_Microft wrote: post #41

Earlier quoted context omitted.

I think they will practice until they get the landing right all the time. The engines with vacuum optimized nozzles are not suited for landing. They can not be gimbaled and are very over-expanded as well. I would not be surprised if the engines with vacuum nozzles destroyed themselves if they were fired at sea-level.

The engines were tested at sea level with the vacuum nozzle. Not being gimballed is bad, but they are throttleable, at least. All these crazy failure modes will have to be tested before Starship is human rated.

You are correct. There is even footage from a test on Youtube. Thanks for pointing this out.
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