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I've read the superdracos have a deep throttle range suited for attitude control during powered landings---an old requirement that's long been dropped.

This has me wondering: are the superdracos throttled for pitch and yaw control during launch escape? Or do they rely on aerodynamic forces alone to keep Dragon pointed the right way?

The center of pressure is below the center of mass while the trunk is still attached, so Dragon + trunk is aerodynamically stable with nose pointing forward, so maybe no active attitude control is required until the launch escape engines shut down and the trunk separates?

Then again, what if launch escape happens during stage-2 flight, well above the thick atmosphere, where aerodynamic forces are negligible? You couldn't rely on aerodynamics alone to keep the rocket pointing forward then, and if something caused Dragon to begin rotating, then it seems possible it could flip end over end without some type of active attitude control?

Also curious how Dragon would realign itself with heat shield forward. In the thicker atmosphere, drag would be enough to do this, once you separate the trunk, which would only happen after the superdracos shut down. But high up where drag is negligible? Wouldn't you need to fire the draco RCS thrusters to cause Dragon to start rotating, and then fire them again to stop the rotation once Dragon is heat-shield forward?

So it seems you would need active attitude control both while the trunk is attached and after it separates...? Before the trunk separates, the superdracos would be more sensible for attitude control (no need to fire the smaller dracos, since the superdracos can handle the job?). After the trunk separates, the dracos would be the only sensible thrusters to use for attitude control...

...But anyway, since the superdracos are absolute complete utter fuel guzzlers, and they'll empty out the whole MMH/NTO fuel tanks in just a few short seconds... would you even have any of that fuel left to power the smaller dracos for attitude control once the superdracos shut down?

And if you don't, then... would you just let Dragon descend in whatever attitude it happens to have---and with whatever rotational momentum it happens to have, meaning... possibly tumbling around---until it hits the thicker atmosphere where drag would take over the job of ensuring the heat shield is facing forward?

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The SpaceX In-Flight Abort webcast (3:14 in vid, T+2:45) announcer says that the Dragon capsule uses its Draco attitude thrusters to re orient the vehicle after the trunk has separated. I think this is what we see ~@3:47 in that video where it looks like the gases from the attitude control system are visible being blown behind (?above) the spacecraft.

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  • $\begingroup$ Ah! Thanks for the link! OK, so dracos for active attitude control post-trunk-separation. I wonder if/how they do attitude control while the superdracos are firing. Hm... $\endgroup$
    – user39728
    Apr 29 at 21:50

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