[amsat-bb] Re: info on satellite placement

Robert Bruninga bruninga at usna.edu
Mon Oct 30 05:55:51 PST 2006

> I was wondering if any one can suggest where I might find 
> information on "how a satellite" gets placed into orbit.
> I ... can only find that a rocket gets it there. 

Actually, the only thing the rocket does is get it going fast
enough.  The only way to stay in orbit is to be going 17,500 MPH
You could orbit the earth at tree-top level if it were not for
air friction which would cause you to loose your speed and hence
fall to the ground.

So the only thing the rocket does is 1) Get you going fast
enough to stay in orbit, and conicidently, get you a hundred or
so miles above tha atmosphere so you can keep that speed up long
enough to do something useful.

Notice how the rocket almost immediately starts turning towards
the horizon after launch, because it is horizontal speed that is
what defines an orbit.  It does travel upward at first to get to
less dense air friction as soon as possible, but then begins to
head horizontal until 17,500 MPH is achieved.

> I hope to learn how and when its gets kicked off the rocket,
> and what happens after that. 

Once the rocket gets to 17,500 MPH horizontally at the altitude
you want, that is when you separate the satellite and let it
continue.  Usually the rocket uses some left over fule to
slow-down and hence, fall back to earth.

If you are not perfectly horizontal and not exactly at the right
speed, then your orbit will not be circular but will be an
elipse.  AO-40 was launched into a very eliptical orbit to get
out to 40,000 km at apogee for a very large footprint.
Eliptical orbits are just fine, as long as they do not intersect
the earth or the earth's atmosphere.

I said 17,500 MPH as a representative number.  It is different
for each altitude orbit relative to the center of the earth.
Remember that a 500 mile orbit (above the Earth's surface) 1s
4,500 miles above the center of the Earth.  But a 200 mile orbit
is 4,200 miles above the center, so the speed is not that much

Hope that helps.

More information about the AMSAT-BB mailing list