Nicely compiled video from SpaceX of the Falcon Heavy and Starman launch, including by the way the Center core missing the drone ship!
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I suspect the booster's landing legs were not yet deployed because it was arriving there much sooner than it would have if the engines were all firing, So it wasn't time for them to have deployed. Good thing they aim away from the drone ship and make the landing move over it at the last second or that would have been a pretty bad hit. Can't wait for the next Falcon Heavy launch. BTW- Awe inspiring video huh?
The timing of the legs are preprogrammed. Since the outer engines didn't light and the booster hit at 300 mph, then the legs didn't have time to actually deploy. It's also why SpaceX has the booster come in where it does then shift to the ASDS at the last second. This was a perfect example of the smart planning designed to protect the ASDS.
I suspect the legs deploy at a given air speed. They may not even be able to unfold at high speed, at least without a major upset to the stage's stability.
Earl.detty
Member
Very inspiring. We drove down from Ohio to watch it. Our first launch ever, we will go to every falcon heavy launch till I die. Got this a week later.
I picked up a lot from that amazing and inspiring video. Interesting shots of how the Roadster was prepped for the mission, and finally an image showing the tiny Roadster and Starman fixed to the dashboard!
HankLloydRight
No Roads
My favorite shot in that video is at 22 seconds in; close up of all 3 cores with 27 engines lit!
hill
high fiber member
not to pick nuts, & not certain, but didn't they post that the reason the main section couldn't land on the Sea barge was because 3 of the centre rockets' 9 engines didn't fire?
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The engines all worked for the first 3 burns. That included the full launch sequence. It was only on the center core landing burn that 2 out of the 3 engines they planned to use didn't properly light. The engines ran out of TEA-TEB fluid used to light the engines.
It is as @Grendal explained above. The launch was nominal. Center core re-entry — after 2nd stage separation — was not nominal. But it’s an easy fix for next time.
dhanson865
Well-Known Member
Not that they didn't fire, that they didn't relight. As in the egines start, stop, start, stop, start again. The two engines that didn't restart the last time had already been started and stopped previously in flight. They just ran out of "lighter fluid" known as TEA/TAB and didn't relight for the 4th time that flight (but did light 3 times prior).
The first stage burns are
* launch
* boost back (not always used)
* reentry
* landing 1 engine (can be continuous to surface)
* landing 3 engines (can be continuous to surface or a short burst)
* landing 1 (not always used, if used after a 3 it will be until surface)
The image below shows the burns as orange parts of the path, the gray parts are when the engines are off.
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HankLloydRight
No Roads
So I'm just curious is the TEA/TAB for all nine engines stored in one vessel, or are there individual tanks for each merlin engine? If there are individual TEA/TAB tanks within each engine, would it be possible to detect a failure to light in one engine, and then immediately failover to one of the other 6 idle engines?
That's a good question. I don't know the real answer but I'm willing to make some guesses based on what we know. We know that the center engine lit but the two outer engines did not. I'd say there are three possibilities based on that:
1. Each engine has it's own stored TEA-TEB fuel for relight. In this case, I'd add that the center engine has a larger vessel for storage. This is because SpaceX knows that this engine will be relit many times. In this situation, your idea would work as long as the system switches to opposing engines. Any other situation would create an imbalance.
2. The center engine has its own fluid and the outer ring of engines has its own storage of fluid. I'd say this is the least likely scenario.
3. There is one TEA-TEB storage vessel for all of the engines.
dhanson865
Well-Known Member
I don't know but that is a good question. Elon's response after the flight was that they'd simply increase the amount loaded on the F9 Heavy for next time. But I don't know if that is increasing the amount in 9 individual tanks or increasing the amount in 1 or 2 or 3 tanks (they like redundancy so even if grouped it could have a primary TEA/TAB tank and a secondary TEA/TAB tank or be in pairs or triplets somehow).
Knowing the center engine gets used more on average it either needs more or less TEA/TAB. I think that would be less because it just says lit without needing a continuous feed of TEA/TAB. But it could have more just as a higher safety factor even if it doesn't use it all.
