Low-Thrust Trajectory Computation in GMAT

Dynamics and environment models, spacecraft model, solver algorithms, etc.

Low-Thrust Trajectory Computation in GMAT

I am interested in knowing whether GMAT is able to compute finite burn low-thrust trajectories. The trajectory may either be feasible (e.g. computed via differential correction) or optimal (e.g., uses optimal control theory and minimizes or maximizes a performance index).

In particular, I am wondering whether I can specify an initial spacecraft state, a time of flight, a final spacecraft state, and thruster parameters (e.g., Isp, max. thrust) and have GMAT then compute the time history of thrust direction and magnitude that will take the spacecraft from the initial to final state whilst respecting all other constraints -or- tell me that a feasible solution does not exist for the states and constraints I specified. I am primarily interested in interplanetary trajectories (heliocentric inertial frame, J2000 ecliptic coordinates). Also, the force model can be as simple as restricted two-body gravitation with the Sun as the central body.
bbarbee

Posts: 4
Joined: Mon Jun 01, 2009 2:57 pm

Re: Low-Thrust Trajectory Computation in GMAT

We are currently testing low thrust modeling in GMAT. Once the testing is complete, you will be able to compute feasible low-thrust trajectories, or sub-optimal trajectories. By suboptimal, I mean you will be able to break up the trajectory into constant thrust arcs, and minimize a performance index such as mass expenditure.

Our long-term plan is to implement a direct transcription or pseudospectral method to solve this problem more rigorously. That's at least a year or two down the road though.

Steve
shughes

Posts: 443
Joined: Mon Jun 09, 2008 6:27 pm

Re: Low-Thrust Trajectory Computation in GMAT

Thanks, Steve.

When do you think testing might be complete? I'd like to try running some feasible or sub-optimal low-thrust trajectories in GMAT when it is ready.

Your long-term plans for the trajectory optimization sound quite good.
bbarbee

Posts: 4
Joined: Mon Jun 01, 2009 2:57 pm

Re: Low-Thrust Trajectory Computation in GMAT

If all goes according to schedule, in about a month.
shughes

Posts: 443
Joined: Mon Jun 09, 2008 6:27 pm

Re: Low-Thrust Trajectory Computation in GMAT

Ok. Thanks!
bbarbee

Posts: 4
Joined: Mon Jun 01, 2009 2:57 pm

Re: Low-Thrust Trajectory Computation in GMAT

Has this been implemented yet in any of the newer builds? If so would it be possible to post an example script of how to use this feature? If not is there a better estimated date of release?

Thanks!

cheetham

Posts: 9
Joined: Wed Jul 15, 2009 8:11 pm

Re: Low-Thrust Trajectory Computation in GMAT

We had to push this off until the end of september. Sorry for the delay.
shughes

Posts: 443
Joined: Mon Jun 09, 2008 6:27 pm