Re: Orbit calculations

From: Amara Graps (
Date: Sat Mar 10 2001 - 03:21:43 MST

From: Anders Sandberg <>

>Hmm, maybe reading up on celestial mechanics, astronomical
>coordinate systems, downloading NASA data and doing numerical root
>finding is a bit too tricky for the average roleplaying game? :-)

Maybe the following will be "too real", but...

Don't forget the unit vectors if/when transforming between a
rotating spherical coordinate system and a nonrotating cartesian
coordinate system...

Check if the orbit is prograde (typical in our solar system)
rather than retrograde.

Check if the output from those canned routines is physical and oriented
properly. I have been using an old JPL fortran code (has F66 logical
if conditions!) for expansion of a planet's magnetic field in
harmonics (dipole octupole etc.), and I discovered the positive
B direction coming out of the code was flipped down. Not the code's
fault, it was my own foggy understanding of conventions for orientation
of magnetic fields. My dust particles were ejected from the Jupiter
magnetosphere going the wrong way with that little hiccup.

Recent lessons. Creating universes is fun, but the details
are a bear.


Amara Graps email:
Computational Physics vita: finger
Multiplex Answers URL:
"Whenever I see an adult on a bicycle, I do not despair for the
future of the human race." -- H. G. Wells

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