Closest Point between two orbits Question

[TriggerAu]

Anyone ever used any of the below functions to determine when the closest point between two orbits is to occur. Looking for some help on what some of the parameters are:

• Orbit.FindClosestPoints
  
• Orbit.SolveClosestApproach
  
• OrbitCloseEncountersTest.FindClosestPoints
  

Don't need all of them, just one obviously - I think I'm closest to working out the solveclosestapproach function, but "epsilon" and threshold are giving me some grief.

[EndlessWaves]

I haven't looked into orbits but Epsilon is traditionally the allowable degree of error when comparing whether two floating point numbers are equal.

EDIT: Have you looked at the protractor mod? I believe that calculates closest approach.

Edited May 13, 2013 by EndlessWaves

[TriggerAu]

I haven't looked into orbits but Epsilon is traditionally the allowable degree of error when comparing whether two floating point numbers are equal.

EDIT: Have you looked at the protractor mod? I believe that calculates closest approach.

Thanks EndlessWaves, have looked at some other bits where people calculate this manually (including protractor) and I can do something similar. Have two challenges though - am looking to look multiple orbits in advance - and most of the ideas I have seen are very coarse (or very proc intensive) at that timeframe, and theres a function there already - would be nice to use it

Hopefully someone can help out with that other param (or one of the other functions), or I will need to do some maths - which is always fun...

[adammada]

I was trying to use those functions when I created this plugin:

http://forum.kerbalspaceprogram.com/showthread.php/21111-PLUGIN-0-17-AdamKSP-Show-Phase-and-Ejection-Angle-DRAW-trajectory-on-map-v0-6

And they just seem to not work. I think that Protractor author also tried to use them, but failed.

But i just opened MONO Develop and it seems that they all use same approach like that in Protractor mod, which is using getPositionAtUT of bodies to get body position at give times (with dT step), and just looking for closest.

So i don't think that using your own strategy (like in protractor) would be slower.

Edited May 14, 2013 by adammada

[TriggerAu]

I was trying to use those functions when I created this plugin:

http://forum.kerbalspaceprogram.com/showthread.php/21111-PLUGIN-0-17-AdamKSP-Show-Phase-and-Ejection-Angle-DRAW-trajectory-on-map-v0-6

And they just seem to not work. I think that Protractor author also tried to use them, but failed.

But i just opened MONO Develop and it seems that they all use same approach like that in Protractor mod, which is using getPositionAtUT of bodies to get body position at give times (with dT step), and just looking for closest.

So i don't think that using your own strategy (like in protractor) would be slower.

Thanks Adammada, good to know I'm walking in other peoples steps and not just being dense Is a bit of a shame to write something that obviously has a function already in use, but if thats where it goes I'll just take it. Thanks for responding

[adammada]

Just borrow code. Protractor and MechJeb are open soruce and free ( GPL if i remember correctly), so it will be perfectly fine to do that.