# [LINK] Finally up to date on the Shuttle

James Pearce james.pearce@zdnet.com.au
Fri, 14 Feb 2003 17:53:48 +1100

```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
> _______________________________________________