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The space shuttle launch program was based on a target attitude profile calculated for the mission and the latest winds. The attitude profile would include roll, pitch, and yaw as functions of time for the thrust vector controllers to track, and it would be loaded to the space shuttle computers shortly before launch.

I've read they would determine the target attitude profile from numerical simulation.

But since the purpose of the simulation was to figure out the appropriate attitude profile, that attitude profile could not serve as an input to the model used in the simulation. So you would have to constrain the model---e.g., to have the vehicle track the velocity vector (or a velocity frame constructed from that vector) in the gravity turn phase---in order to solve for the attitude profile.

But I've never read how any of this is done, and this is me guessing based on the few bits I've read. Can someone comment on how the space shuttle simulation would have been set up/constrained in order to solve for the launch programs they would eventually I-load to the flight computers before launch?

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  • $\begingroup$ I suggest you read this:ntrs.nasa.gov/api/citations/20110003654/downloads/… I'm not sure summarizing it would really serve your purpose, so not writing an answer. If you have specific questions after reading that, feel free to modify your question. See part VIII especially. FYI, I-loads were data, not programs or processes. $\endgroup$ – Organic Marble May 17 at 15:59
  • $\begingroup$ Thank you! Yes, yes, I meant "data" and not "program." Just trying to figure out to set up a simulation to get that data to drive my attitude error calculation to feed my thrust vector controllers. What I have now works, but there are space-shuttle things I want to capture in my model that my current scheme won't allow. Figuring out how to get the I-load data would be the first step toward correcting this :) $\endgroup$ – user39728 May 17 at 16:04
  • $\begingroup$ If you don't have wind in your simulation, you don't really have to calculate new values for each run. The roll and yaw commands didn't change much after the "roll program" aka SAR anyway, just the pitch (except for the roll-to-heads-up comm maneuver introduced late in the program). space.stackexchange.com/a/12010/6944 $\endgroup$ – Organic Marble May 17 at 16:16
  • $\begingroup$ OK, already I have something good out of that paper! So DOLILU would target a -4 deg angle of attack to minimize wing loads. That number happens to be my angle of attack when I transition from pitchover to gravity turn, and it's been problematic because... my (current, but probably not final) gravity turn program works by holding a zero angle of attack... so when I transition from pitchover to gravity turn, the rocket wants to pitch up by 4 degrees... I don't imagine a -4 deg AoA would make sense for a rocket without wings, would it? $\endgroup$ – user39728 May 17 at 16:21
  • $\begingroup$ I don't have detailed knowledge of non-winged launch vehicles, but my understanding is that yes, the negative alpha before Mach 1.7 was to minimize wing loading. $\endgroup$ – Organic Marble May 17 at 16:23

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