# [LINK] Finally up to date on the Shuttle

Chirgwin, Richard Richard.Chirgwin@informa.com.au
Sun, 16 Feb 2003 16:46:18 +1000

```Thanks to all who helped with this.

So, to my clumsy understanding - you preserve momentum. In descending orbit,
you decelerate; but acquire angular velocity because of the descent.

Ie, to begin decending, you slow down; but the ACT of decending speeds you
up. Or to ascend, you speed up, but the result is lower velocity. Yes?

Richard

-----Original Message-----
From: James Pearce
Sent: 14/02/03 16:53
Subject: Re: [LINK] Finally up to date on the Shuttle

That's phenomenal, Bernard!

As a body in orbit decelerates towards the earth (or at least, reduces
it's
acceleration) it's speed increases! That would happen, too. Physics is
weird...

----- Original Message -----
From: "Bernard Robertson-Dunn" <brd@austarmetro.com.au>
Sent: Friday, February 14, 2003 4:07 PM
Subject: Re: [LINK] Finally up to date on the Shuttle

> Re all this orbital mechanics stuff.
>
> The dynamics of an orbiting body is a combination of kinetic and
potential
> energy.
>
> An orbitting body at (say) 500km altitude has a particular velocity.
To
get
> to an alltitude of 1000km, it has to fire its rockets. Once it gets
into
> its higher orbit it is actually going slower than at 500km. The energy
from
> the rocket firing has initially been converted kenetic energy but with
an
> increase of altitude this changes into potential energy.
>
> Every orbital altitude equates to a particular velocity (both angular
and
> rotational).
>
> The reason why a body has to decelerate to go into a lower orbit, but
> higher velocity, is because it has excess potential energy. Total
energy
> level (KE+PE) needs to be reduced in order to get to a lower orbit.
This
is
> done initially by reducing the KE. As it moves to a lower orbit the PE
> reduces but the KE increases to a level that was greater than at the
higher
> orbit.
>
> --
> I know that this defies the law of gravity, but, you see, I never
studied
> law.
> --Bugs Bunny
>
> Regards
> brd
>
> Bernard Robertson-Dunn
> Canberra Australia
> brd@austarmetro.com.au
> _______________________________________________