dirl wrote:How can I make a parabolic/hyperbolic orbit?
As far as I know, you can't, and perhaps that can be confirmed by checking Selden's documentation here:
How to transform orbital elements into Celestia's SSC format (http://www.lns.cornell.edu/~seb/celesti ... meris.html)
However you seem to be on the right track by using PericenterDistance instead of SemiMajorAxis: the semi-major axes of parabola and hyperbola are undefined so astronomers use
q, not
a.
You don't need to use parabolic/hyperbolic orbits for known comets though. I think so far there is still not an officially accepted comet found to be coming from beyond a captured orbit about the sun. All measured eccentricities are in fact still less than 1 (any appearing greater are by less than the estimated error of measurement).
I think the reason why parabolic/hyperbolic orbits haven't been implemented yet (a term HyperbolicOrbit, instead of EllipticalOrbit would do) is that a developer would have to 'clip' the orbit at some distance because the two arms of the orbit extend to infinity.
I suppose so far, effort for this outweighs benefit.
Spiff.