Xprize and tethered space station

On Tue, 16 Dec 2003 15:39:29 GMT, wrote:

Ron, I'm very confused... You wrote
:
:The big thing to remember is that this altitude/velocity combination is
:*inviolate*. Increase your velocity, and you climb into an elliptical
rbit with a higher average altitude or even shoot away, free of the
:Earth's gravity. Decrease the velocity, and you drop into an elliptical
rbit with a lower average altitude...too much lower, of course, and you
:impact the Earth.

OK, I think I understand. If you're in LEO and you want to go to a
higher orbit, you have to add not just altitude, but velocity. So you
point your self forward and up, light the rocket and climb and
accelerate.

Just forward. Increase the velocity, increase the orbit. Just like a
plane, increase the speed, you climb, all other things being equal.

:
:Left to their own devices, the Main Station would require an orbital
:velocity of about 10,000 FPS, and the Way Station about 25,000 FPS. The
:Main station would float in stately grace, fixed above a spot on the
:equator. In truth, though, it doesn't care about what's below it...all it
:knows is that it orbits the Earth once every day. The fact that the Earth
:turns to keep the same point underneath it is trivial. At the same time,
:the Way Station whizzes past underneath, 13 orbits per day.

And that's where I'm confused. Isn't 10,000 fps at GEO a lot less
than the 25,000 FPS at LEO?

Yes. Here's the thing, the way station in LEO is attempting to be
geosynchronous, at the wrong orbit. To do so, it needs to go faster.
But, being tethered to the earth and the mass out beyond GEO keeps it
in place.


I understand that the actual distance, the circumference, of the orbit
at GEO is a lot bigger than at LEO, and I'd always thought that
accounted for lower satellites going "faster" around the earth in
radians or orbits per day.

Correct.


It's the spinning ice skater/angular velocity thing that has me
confused. Pull in the arms, you spin faster, but drag slows you down.
Put out your arms, you go slower - your hands are going the same speed
in FPS as before, but they're going around a bigger circle.

Why is it that in going from LEO to GEO you're getting rid of speed?

Maybe this will do it. Say I'm in a nice, stable, circular orbit at
GEO. I want to drop to a nice, stable, circular orbit 100 miles
lower. I don't care about the orbital period, I just want to do it.
Which way do I point my nose before I light my rocket?

Straight back, tangential to the orbit.

Go to sci.space and ask the questions. Your head will spin with the
math they answer your question with :-)

--
dillon

Life is always short, but only you can make it sweet