3 ms·
My suspicion was they were burning excess propellant, rather than attitude adjustment while under the parachutes. Though who knows how much propellant remained
by hydrogen7800 6mo ago
My suspicion was they were burning excess propellant, rather than attitude adjustment while under the parachutes. Though who knows how much propellant remained. It could be quite a bit more than it appears was used.
- devilbunny 6mo agoNot just excess - excess and toxic. Hydrazine derivatives and nitrogen tetroxide, IIRC. They are hypergolic, too, so the easiest way to vent them is just to run the engines until empty. However, to prevent moving the craft too much, you do short bursts.
- TomatoCo 6mo agoThere should be an opposite thruster for each axis. I wonder if the short bursts were due to heating limits.
- devilbunny 6mo agoThere are opposed thrusters, but I assume that in atmosphere and under parachute canopy it’s harder to make sure they are perfectly opposed. Heating likely plays a role as well. I am not a rocket engineer, but I have read How Apollo Flew to the Moon and Ignition!: an informal history of liquid rocket propellants, both of which cover these issues. Highly recommended.
- _moof 6mo agoThe short bursts are just the period of the control cycles. Control cycle starts, loop sees error, commands thrust; next control cycle starts, loop sees error is nulled (or in deadband), commands no thrust.
- m4rtink 6mo agoOn the press conference they mentioned the RCS was used to orient the craft with the most sturdy part facing down for the ocean impact. Otherwise I would also just bet on RCS venting like in Apollo.
- hydrogen7800 6mo agoIn the post splashdown conference, they mentioned that these were indeed attitude control bursts to orient for favorable orientation for water impact.
- _moof 6mo agoIt was for attitude adjustment.