The hybrid motor has worked reliably and repeatably in temperatures as low as 30 degF. The next question is whether the motor will work at 100 degF. Since the Nitrous is cooled via boil-off, it is also worth measuring how much Nitrous is lost while cooling the chemical from 100 degF to 23 degF (400 psi). Calculations using Evan Daniel's HSIM calculator indicate the motor should consume 8.4 lbs of Nitrous and boil-off another 3.5 lbs.
Unforuntately the motor failed to light.
The injector is configured as a 5 port UC valve. The central port is 0.190" dimeter, and the four outter ports are 0.073" each. A large central APCP grain sits on the main central fill tube, and four smaller APCP grains sit on the outter injector ports. Two eMatches are placed on the core APCP grain (not shown) about 75% of the distance to the edge.
The central APCP grain lit. When the Nylon tube ruptured, it blew the burning APCP grain 12" downstream, where it created a second burn-through on the Nylon. The motor lit about 4" from the aft end of the PVC.
The good news is that the motor did reach equilibrium at 400
psi and 23 degF despite ambient temperature exceeding 100 degF.
Total Nitrous consumed for fill and boil-off was a little more
than 10 lbs.
