Ascent Trajectory

[thylow23]

Does anyone know how or the approach on determining the initial pitch rates as good guesses for a trajectory optimization program? Is there another software out there that does this?

 

[StarBound]

Ther are several codes available via NASA (does require US citizenship approval) one in particular is OTIS, soem others that I've heard about but not too familiar with are POST and Maverick. Good luck.

 

[GregLocock]

What are you trying to optimise against? The approach used by the space shuttle team has been well described.

Cheers

Greg Locock

 

[thylow23]

I'm working with POST and currently, the trajectory is very sensitive to the U-Vector/Initial guesses of the control variable. How do I come of with a good approach to determine an initial guess within he ball park of the solution. I hate to make a guess cause I feel like if the solution converges then I just got lucky. I also know that one converged case isn't the necessarily the best optimized solution for an optimization problem. The space shuttle example doesn't really explain how they got those values as their initial guess. My company doesn't have any problems obtaining OTIS or SOAP. Is there any other trajectory programs that you can refer me to that doesn't have the issues tha POST does?

 

[GregLocock]

I am a dabbler, I wrote my own simulation in Scilab, and then optimised the trajectory using a GA search.

Perhaps you could write a script that runs POST as the evaluator in a GA optimiser.

Incidentally I found that the solutions were quite robust, that is, large changes in trajectory only resulted in small changes in energy used.

Cheers

Greg Locock

 

[thylow23]

I have just started my trajctory course for grad school. This issue would probably be clarified after/during the course. Part of the course... I will be learning how to creat my own propagator and hopefully I'll understand the details behind it.