RE: Um, eh? (Orbital Mechanics for Dummies)

Well, this isn't obviously true.  Note that Skylab came down without the
benefit of thrusters (in fact that was why it came down).  Also note
that the Space Shuttle requires tons of fuel and two solid rocket
boosters to reach orbit, but essentially it glides back to earth using
only small thrusters to pop it out of orbit.

When you go up, you are buying potential energy and when you come down
you get it back.  Most of the time, you are worried about too much
energy on re-entry and have to take a gradual slope that allows you to
bleed off speed in the upper atmosphere before hitting the thick stuff. 
If you hit it too shallow though, you can skip off, like a flat rock on
a pond.

I can't remember if any Jupiter probes did this, but there is the idea
of aerobraking, where you skip in and out of the atmosphere a couple of
times to bleed off the interplanetary speeds and reduce you down to
orbital speeds without having to use a lot of thrusters.

--Binhan

> Randy said:
> >This is actually one of the flaws in orbitally dropped 
> munitions (like
> >Thor from Renegade Legion).	It takes just as much work to drop
> something
> >from orbit as it takes to get it up there (aside from the 
> fact that on
> the
> >way down you can use atmospheric drag to do some of the work).
>