Re: [FT] Orbit and FT

Brian Bilderback wrote:
> 
> >From: "B Lin" <lin@rxkinetix.com>
> 
> >It's only a problem at low orbits, where you still have wisps of
> >atmosphere.	Sky Lab came down because it was low enough to have a
slight
> >drag and it ran out of fuel for the thrusters.  It was thought
uneconomical
> >to try to push that much mass into a higher orbit.  When you get a
few
> >thousand miles out, there isn't much atmosphere to deal with so it
would be
> >negligible.
> 
> So maybe the lowest orbital band in the game would have this facotered
in,
> but no others.

Just a point of real satellite ops, the Hubble Space Telescope's nominal
operating height is ~370 miles above sea level. Over the years the wisps
of atmosphere drag on it, dropping its orbit anywhere from 20-50 miles
in
~3 years. During each Servicing Missions (which we just finished up with
a successful 3b last week) the shuttle reboosts the Hubble back up to
approx 370 miles (this time I think they only went to 360). The effects
of atmospheric drag are relatively negligible in the time frame of a
single game/scenario even up a few hundred miles [from a planet very
much like our own; obviously other planets with different atmospheric
composition, and stellar interactions, will vary this to some extent].
During times of high solar activity, the Earth's atmosphere expands.
During low solar activity, it contracts (hence the 20-50 mile drop in
our orbit over a period of 3 years). If you are assuming 1 mu is
equivalent to 1000 miles, "low Earth orbit" (which is where the Hubble
and most other satellites are) is well within 1 mu of the planet. Your
lowest orbital band is going to be pretty tight if you want to model
atmospheric effects.  ;-)

Just some stuff to chew on.