Test 2019-1

This was my first test burn of an APCP motor using grains I cast myself.

2 grain 54mm Everclear motor with #24 nozzle, using one of Terry's igniters, on the test stand in Hartsel at the first Tripoli Colorado launch of the year. The grains used were from teh 7 January 2019 batch:

• Grain 1, 2.990" long, 163.7g gross, 5.50g casting tube, 158.20g net propellant
• Grain 2, 2.992" long, 163.8g gross, 5.51g casting tube, 158.29g net propellant

Used abou 7.5" of ARR liner, the grains were definitely "loose" in the case. The buna-n o-rings were lightly lubed, but the liner was put in without any grease.

Tested without simulation, using the "standard" EX nozzle for a 2-grain 54mm case according to the Loki Research data table. Tapped forward closure for pressure sensor, buna-n o-rings.

Simulation says ...

Results

Test stand data logged as sn 3634, flight 16. Note that the sensor calibration was re-done after the weekend, at which time we observed that the load cell wasn't really linear unless another 10 lb or so were added to the arm vs what we were running with. So all thrust values from this and all prior test sessions are suspect. Chamber pressure numbers are with fairly high confidence but not great resolution due to reduced output on the 2500psi sensor used.

No measurable erosion of nozzle throat. The liner was pretty well cooked, but no signs of burn-through or case damage of any kind. The o-rings on each end looked relatively undamaged, but were of course discarded after use.

This motor burned very cleanly. Almost no visible flame, just some yellow-ish flashes near the end of the exhaust plume. The 2.8 second burn was slightly progressive, starting around 117 N, peaking at 212 N. Peak chamber pressure was around 740psi.

These results make me think it would be "safe" to fly more grains as long as I stick with the Loki recommended EX nozzle throat for each grain count.