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Comment by hydrogen7800 | Hacker News Reader

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.

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Not 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.

There should be an opposite thruster for each axis. I wonder if the short bursts were due to heating limits.

There 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.

The 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.

On 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.

In the post splashdown conference, they mentioned that these were indeed attitude control bursts to orient for favorable orientation for water impact.

It was for attitude adjustment.

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