Error when using atm. drag for more than 1 spacecraft

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Error when using atm. drag for more than 1 spacecraft

Postby ramirez » Mon Jul 18, 2011 1:30 pm

Hi,
I am running into trouble running some simulations.
When I try to propagate more that one spacecraft and include drag effects in the propagator it throws an exception:
ODEModel Exception Thrown: Drag modeling only works at the Earth in current GMAT builds

(I am using Earth, so it is not the issue). It works fine for one spacecraft, but when I try to propagate more than one vehicle it throws the exception, if I turn drag off, it propagates well more than one spacecraft.

It might be a simple issue, and I will try to find the problem in the code, but would like to know if any of you has also noticed it and/or have any comments about it.

BTW I am using the latest windows distribution.
Thanks.
ramirez
 
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Re: Error when using atm. drag for more than 1 spacecraft

Postby shughes » Wed Jul 27, 2011 2:30 pm

I tried to duplicate this issue but was not able to. Is it possible for you to attach your script? If this is a bug I would like to enter into our bug tracking system.
shughes
 
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Re: Error when using atm. drag for more than 1 spacecraft

Postby ramirez » Wed Jul 27, 2011 8:06 pm

Attached is the script. Before placing in the bug tracker I wanted to make sure I was not doing something silly since I am new using GMAT.
The script works if you switch the commented line in the mission sequence.
Attachments
3FormationFlight.script
(8.81 KiB) Downloaded 412 times
ramirez
 
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Re: Error when using atm. drag for more than 1 spacecraft

Postby shughes » Thu Jul 28, 2011 7:14 pm

this is a bug but at least there is an easy workaround. I believe the force model is throwing an exception because Sat2 and Sat3 have Sat1 as their origin. I change the mission sequence to look like this and it worked fine:


Code: Select all
BeginMissionSequence;
Sat2.CoordinateSystem = EarthMJ2000Eq;
Sat3.CoordinateSystem = EarthMJ2000Eq;
For I = 1:1:20;
   Propagate DefaultProp(Sat1, Sat2, Sat3) {Sat1.ElapsedSecs = 1200.0};
EndFor;
shughes
 
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Re: Error when using atm. drag for more than 1 spacecraft

Postby DJCinSB » Thu Jul 28, 2011 8:30 pm

I suspect this is another case of the root cause of an existing bug (2450, and possibly 2443 as well). We have several bugs now that are associated with force model origins different from the origin needed for the force computations. We are missing a coordinate system transformation from the Spacecraft CS to the force CS. That is definitely the issue in 2450; it looks like it is the same issue for this one, though the fix here is slightly different from the fix for 2450.

Steve, please do file a bug report, and mark this one as "depends upon 2450." It's on my plate to fix as soon as I have current work under control.

- Darrel
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