The Spacex SN8 Starship flew to high altitude but explodes when it came in too fast for landing.
Elon says fuel header tank pressure was low during landing burn.
Successful ascent, switchover to header tanks & precise flap control to landing point! https://t.co/IIraiESg5M
— Elon Musk (@elonmusk) December 9, 2020
Fuel header tank pressure was low during landing burn, causing touchdown velocity to be high & RUD, but we got all the data we needed! Congrats SpaceX team hell yeah!!
— Elon Musk (@elonmusk) December 9, 2020
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So it appeared as if SpaceX's flight profile intentionally shut down engines on the way up, in order to roughly hover and burn off fuel near apogee.
Is that the consensus, or do we suspect that engines cut out unexpectedly?
The fact that the two engines that shut down early were the ones that re-lit later (despite problems) seems to support the idea that it was intentional? But there was that fire inside the engine bay (accumulated unburned fuel?) – that was almost certainly unintended…
Overall a stunning success. Lots of data to process due to the fact they were able to perform 95% of what they wanted to.
Perhaps they're keyed to a certain velocity.
The landings with one engine were with rockets that had one engine. Those rockets probably massed less.
I can't seem to find the source, so this may not be entirely correct. In any case, the information was that the intent was to use all 3 engines for landing, that landing was possible with 2 engines, but that landing was not possible on 1 engine.
The crash was not from "coming in too fast" but from "sudden deceleration".
They really nailed that landing… they just nailed it a little too hard.
I think the "white smoke" – for me – was from the RCS (reaction control system)
I think all the engine behavior was planned including going from 3 to 2 to 1 before cutoff, relighting 2 for the flip and going back to just 1 engine for landing. 1 Engine throttled back should be quite sufficient for soft landing – it was in earlier tests. It just didn’t have quite enough flow in the last second for the soft touchdown. Even more robust landing legs might have done it, but it worked in previous hop without them, single engine matching velocity perfectly.
Just guessing, but I wonder if they were chilling the shutdown engine(s), as they do before launch, to keep them ready for restart and the white smoke was venting from that.
It flew nicely, thrust vectoring control with only 1 engine seemed great. Too bad the landing failed, they could get more data from intact engines. They will do that in one of the next ones. Good.
If you watch the engine compartment feed, there was a white plume coming out the right side since the beginning, and then at some point there was another one coming out the left side too. Looked like both were coming from the walls, not the engines. So maybe something caught fire, but more likely it was either deliberate venting, or a leak of some sort. Might explain the low pressure on landing.
So the methane header tank pressure was too low and this caused the engine to run oxygen-rich? The super heated oxygen is basically cutting torch so that would be "engine-rich exhaust". That would explain the bright-green exhaust. Oxidized copper is green.
Learn from the problem and continue onwards.
This is not easy. They don't call this rocket science for nothing
The fire lasted little. The white smoke I really
don't understand. Leaking oxygen?
I noticed the apparent burning of something around the inside edge of the skirt when they showed the interior view of the engines — more than one time. Also, the white smoke trailing from the rocket seemed wrong to me. As far as I know, burning methane does not produce such smoke, so I wonder whether that was coming from whatever seemed to be burning around the inside edge of the skirt.
Maybe I'm misinterpreting something that is normal and not a problem, but it makes me wonder. It was so obvious that I expect that if it is something that is a problem, the SpaceX folks will address it.
This test was largely successful. I give SN9 a 90% chance of soft landing.
Low header tank pressure, so yes, fuel starvation. The small amount of flame after the crash demonstrates the small amount of fuel left at landing.
Yes, it did, but I know no more than you.
Notice the landing legs did not deploy?
My bad, that would be a lower-quality pic…
Brian, for the free fall picture here may I suggest one with the flaps vortices visible?
All hail engine 42 for it’s valiant effort to reach apogee.
One of two engines at landing gave up—to fuel starvation?
Elon gave it a 3 of 10 chance of landing intact. The maneuver by fins on the way down was the essential data gathered—it went way beyond expectations by achieving the attitude adjustment burn for a vertical landing! Two more seconds from both engines could have stuck the landing. 9.5 for the score!
Same.
It looked like they tried to put it in reverse while doing 65 on the freeway XD
I don't know, but didn't it look like something caught fire when they shutted down the first engine ?.
That. Was. AWESOME!
I also think I saw plumes of oxygen from the bottom of the
ship during ascent. Was the tank leaking?
Looks like Elon Musk tweeted that the fuel pressure was too low during the landing and thus the engines couldn't completely slow the Starship down. Doesn't seem a big deal, lets see if they fix it on the SN9.