# [amsat-bb] simple ways to demonstrate orbital mechanics. (Earth and Ball)

Robert Bruninga bruninga at usna.edu
Thu Feb 25 16:06:07 UTC 2016

```Our kid demo of orbits uses a large globe.  We hang a small golfball
satellite on a string from the ceiling.  There are several demos we like:

1) Center the globe under the string and the golf ball sticks to the
globe. (gravity)

2) Try to push the ball in a circle.  If you get a perfect circle or a big
enough one, you will have an orbit and not hit the earth.

3) If you have too much vector "up" in any one direction (not circular)
then on the next pass it crashes into earth.. (all orbits are elipses and
you don't want part of your ellipse to run into the earth.

4) Now move the earth about a radius or diameter away from under the
string.  Now try to launch an elliptical orbit where the ball just grazes
the earth at perigee and goes way out at apogee.  You can get a nice
Molnya orbit.

5) For GEO transfer, we had a mark on the floor and a mark out 5 earth
radii where we had a little tiny bowling pin on a pedestal.  Here the
object was to launch the ball from behind the earth so that it would go
out and intersect the bowling pin and knock it off.  Thus demonstrating a
transfer orbit to GEO.

No, this is not the same physics of a central force (gravity) driving
Keplers laws, but it is a perfect demo of circular and elliptical paths.
For example in this case, the orbital speed is the same at perigee and
apogee (non Keplerian), but still it is an elliptical path with the earth
at one foci...

Kids love it.  Especially #5 is a real challenge.  And even #1 is hard if
you are trying to orbit only 1 inch above a 24" diameter earth globe.

Do not use an expensive valuable globe (from your wife for example)
because there will be LOTS of crashes from bad "orbits"...

Bob, WB4APR

-----Original Message-----
From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of
skristof at etczone.com
Sent: Thursday, February 25, 2016 9:17 AM
To: Tom Schuessler
Cc: amsat-bb at amsat.org
Subject: Re: [amsat-bb] simple ways to demonstrate orbital mechanics.

Don't forget that you can download data from AO-73 off of the amsat-uk
website. Their data is great for looking at temperature increase and
decrease, spin rate, voltage changes in the solar panels as the satellite
goes between light and dark, and how the battery discharges during the
dark periods. Easy access and good teaching material.

Steve AI9IN

On 2016-02-24 08:47, Tom Schuessler wrote:

> Hello all,
>
> Several of us AMSATers in North Texas will again be representing AMSAT
> at the annual "Moon Day" at the frontiers of Flight Museum at Dallas
> Love Field this coming July 16. "Moon Day" is a celebration of
> spaceflight past/present and future and is also a very large STEM fair
> with exhibits from many different scientific and Engineering
> organizations. Many young people including Boy and Girl Scouts are in
attendance.
>
> Since there is such a large youth component to this event, I have been
> looking for some fun ways to demonstrate satellites and orbital
> mechanics to the people who drop by the booth/table. There is a
> special STEM patch that they can earn by visiting different displays
> and asking questions/filling out a worksheet. I am looking for simple
> but creative/fun ways to demonstrate orbital mechanics and also how a
> satellite like our Fox birds work. I plan to build a big poster with
> images of different types of orbits, and have already been given an
> idea on how to demonstrate the different between a
> geostationary/synchronous orbit and a LEO but would like some more
ideas.
>
> If any of you have done some similar outreaches and would like to
> share ideas, please reply on list or off. I would appreciate it much.
>
> Tom Schuessler, N5HYP
>
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