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I'm using Gmat to turn to zero the eccentricity of an orbit around Mars with an electric thruster. I modeled the initial orbit, introduced the engine, the tank and the solar arrays and created the finite burn. The mission sequence is a target where the program varies the duration of the burn so:

  • Vary Duration
  • Begin finiteBurn
  • Propagate Duration
  • End finiteBurn
  • Achieve ECC = 0

The problem is that even changing the number of iterations or the iteration step, the solver doesn't converge. I'm not sending the whole code, hoping that the error is trivial but if needed I'll send it. Can someone tell me what is the problem? I controlled all the obvious things such as central bodies or things like that.

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Your approach seems wrong. In order to circularize an orbit, you have to raise your perigee until it's equal to your apogee. It is implausible to do that only by varying the duration.

I suggest you propagate towards apogee first, then turn on the thrusters for a small interval, rinse and repeat.

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    $\begingroup$ @uhoh what you say is true, but it's implausible to do it in a single burn as given in the question. As you said, you can vary the timing of your "burns", but you can be smart about when to perform them to increase the efficiency. $\endgroup$
    – EserRose
    May 27, 2023 at 15:04
  • $\begingroup$ Oh, it looks like I misread the question - I was thinking iterations were orbits. In this case I'll delete everything I wrote. Sorry about that! $\endgroup$
    – uhoh
    May 27, 2023 at 16:06
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    $\begingroup$ there are a LOT of untouched GMAT questions of this site that could use some love if you're willing. I don't think we have that many GMAT folks hanging around $\endgroup$
    – Erin Anne
    May 27, 2023 at 16:54

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