Differences in Thrust between GMAT versions

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Differences in Thrust between GMAT versions

Postby walsjona » Tue Jan 10, 2017 1:38 pm

I recently updated from GMAT R2015a to R2016a and have found that for the same script I am getting very different results.

I am currently using GMAT to look at very low earth orbit satellites with thrust compensation. The Satellite is in a circular orbit at around 200 km altitude and the model was run over 90 days of simulation time at various side slip angles. The thrust is calculated by varying the thrust scale factor and targeting the orbital average RMAG after 15 orbits (roughly a day).

What I have found is that while both R2015a and R2016a have consistently been predicting higher Thrust than the Drag, R2016a always predicts significantly higher Thrust (around 16-22% higher compared to 1.2% for R2015a) despite no apparent increase in the simulated drag.

R2015
Image

R2016
Image

The difference in the drag and thrust appears to occur from the very first Target (see figure 3). There is a settling period for R2015a, however, beyond 15 days the thrust tracks the average drag as expected, bar the odd altitude adjustment. R2016a simply remains high throughout.

R2015
Image

R2016
Image

I have tried many different script configuration removing for instance all major perturbations including Earth gravity model but this had no impact.
Has anything changed between versions that could affect these results? I had a look through the change log and none of the changes seemed to suggest they would have an effect.

Thanks for your help
walsjona
 
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