sci.physics

On Feb 18, 8:32 am, Dave Typinski wrote:
> On Sat, 16 Feb 2008 22:22:52 -0800 (PST), nottoo
>
> wrote:
> >I bet if you call a physics professor at a local university he'll be
> >happy to talk it through. Those guys don't seem to have much to do
> >anyway :P
>
> Heh - that's an option. On the other hand, isn't that what
> is for?
>
> >I would suspect tho, that using atmospheric drag to reduce the radial
> >velocity to zero wouldn't work because you have to still have some
> >radial velocity to get out of the draggy atmosphere, and that can no
> >longer be lost.
>
> Sure it can. You're moving upward against a gravitational field. The
> radial volocity drops to zero when sqrt(2gh) uses it all up.
>
> Throw a baseball up into the air. Aerodynamic drag has very little to
> do with the fact that it'll come back down. Before it does, its
> radial velocity will be zero.
> --
> Dave Typinski

Oh yes I forgot that :P

Maybe think of it this way. Put a "gun" in the projectile's path where
it leaves the atmosphere. Now you have effectively the same situation
but with no atmosphere and a higher starting point. We already know
the orbit will intersect the imaginary gun's position and direction
with no atmosphere, that means on the next cycle it'll again fly out
of the atmosphere - so it still has to pass through and suffer some
drag.

I think your problem was an orbit which didn't touch the ground, maybe
you can solve that, but it seems to me you can't solve one that
doesn't touch the atmosphere - and therefore eventually crashes.