I ran an experiment today using the QuEST How High altimeter that I thought might be of interest to the group....
The how-high is SUPPOSED to be used inside of a payload bay - away from the hot gasses and high pressure of the ejection charge... but, since I wanted to see if it would work... and because the thing is only $45... I decided to break the rules and put it into the main tube of a rocket.
I used the "4 Square" which is a new square tube rocket from Newway Space models. The tube is 1.375" x 1.375" and is basically a 4FNC rocket - except that it uses square tubes and square tube-fins. It EASILY fits the How High Altimeter. For this experiment, I attached the altimeter to the nosecone and wrapped the altimeter first in a sheet of wadding and then wrapped the wadding in a sheet of aluminum foil. I pushed wadding into the body, then the parachute, then the shockcord and then the aluminum foil wrapped altimeter. I flew this rocket on a B6-4. WRASP simulation predicted 197 ft using a drag coeff of 0.9 and a body "diameter" of 1.66". After the launch the How High blinked out 1-9-4 feet.... (and my eyeball said "around 200'").
I'll need to run more experiments and see if I might be abusing / overpressuring the altimeter or otherwise damaging it... but I doubt it saw much (any) heat working this way. I didn't make any holes in the tube - basically, I didn't care what it was measuring during the ride up, my theory was that it would pop-out at apogee, take a low pressure reading and then it would compare this to the pressure it recorded when I power cycled it on the ground to see the readout blinks. The worst abuse (I think) is that the altimieter likely sees a pretty good pressure pulse at ejection - don't know if that will be a problem or not....
What do you guys think?
(I'll make a seperate posting about the WRASP simulations vs measurements and assumptions under a heading about predictions for square rockets where I will explain how I got the 0.9 and 1.66" guestimates)
