Re: How would you measure how high a model rocket goes?

Hi Mary,

The best method for doing it, and the way the best amateur rocketeers do
it, is with a little electronic device that measures air pressure and
records the minimum pressure  experienced during the flight. You can buy a
tiny box that you plug into a laptop PC to set it, fire it off in your
rocket, then plug it back in after the flight.

If youcan't get one of those, then the other classic method is to use a
CLINOMETER. A clinometer measures angles, from level. Make one with a
protractor and a piece of string with a little weight on the end. Hang the
string from the protractor centre, so that as you change the angle of the
flat bit, you can read it out on the protractor by looking where the string
crosses the scale.


Make several clinometers, make all your class use one! Get a long, long
tape measure, or pace out a long base line from the launch pad, 600 feet
would be pretty practical, whatever the rocket engine makers recommend. 
Ideally, you want to spread around in a BIG circle around the rocket launch pad

Now all of you get ready for lift off ! All of you, line up your clinometer
with the rocket ! Fire ! Follow the rocket all the way UP. When it appears
to stop, before it falls, hold the string of the clinometer against the
protractor.  You NEED to remember the angle !!

Now for the math !

Rocket height = TAN (angle) * base line.

A PC usually has a calculator that can work out TANgents of angles.

Make a little map, plot everyone's position relative to the rocket and
their angle measurements, then calculate the heights they measured.

They won't all agree, we always expect some experimental error, you would
need to fire lots and lots of rockets, and make many measurements, even if
everything else was perfect to get an answer that you would believe.

Of course, what you don't know is just where the rocket actually reached
its maximum height ? It didn't go STRAIGHT up did it ? The wind moved it a
bit didn't it ?

You CAN work out a much more accurate answer from all the readings you
make, and that takes much more complicated geometry. Drop me another line
and I'll try and help somemore.


Good Luck with your rocket !

Steve