Data Evaluation

The videos are here! See the firing or the gauge. There are pictures on the update page of the larger motor. More pictures are available.

After returning home, video of the pressure gage was examined With the following results. (1) In the first second, the pressure gage values went from 0-80 PSI. There was absolutely no overshoot on this value indicating a nice smooth start of the motor. (2) The pressure stayed at 80 PSI for the next 10.5 seconds. The constant thrust was not unexpected. A paint ball regulator in the second bulkhead was set to regulate at 600 PSI. The motor was designed for a working pressure of 400 PSI giving a differential of 200 PSI to force the H₂0₂ and kerosene into the combustion chamber.

The thrust developed by the motor is then

Where F = thrust of rocket
P = pressure
A = area of piston (3.14 x radius²_piston

Then

Because the rocket was thrusting upward lifting the rocket, the weight of the rocket must be taken into account. I have used an average value weight

Adding this to the thrust value on the piston gives the total thrust per second

The total thrust is the burn time x thrust/second

In metric units, this is equivalent to 6630 Newtons or a mid size M Motor. The total weight of the H₂0₂/ kerosene was 9.5 lbs. However, because of poor welds in the H₂0₂ tank (patched with JB Weld and shim stock) , I am estimating a 1/4 Ib loss of H₂0₂.

The specific impulse is then