Test 2018-1

7 grain 75mm sorbitol motor with pyrodex pellet ignition in 4-inch Wildman rebuilt airframe flown on 2 September 2018 at Airfest in Argonia, KS.

CTI Pro75 6xl case, Loki #50 (long) nozzle with 2 o-rings, CTI forward and aft closure rings, forward bulkhead from Terry's pile machined to have 0.5" inside snap ring plus 0.25" inside liner, with two o-rings, one pushing against liner.
Original simulation says this should be a a 34% M-2293 with 6520 Ns total impulse, 1056 psi max, 76% volume loading, and about 2.25 seconds burn time. After casting and weighing the grains, the adjusted simulation says this will be a ...

Results

Flown at Airfest in Argonia, KS, off Terry's launch trailer. Motor cato'd about 0.45 seconds after launch, blowing forward closure through the ebay and ripping the forward end of the case apart violently. Clearly a significant over-pressure event. Pretty sure this was the first time I actually few the Pro75 6xl case with KNSB, and I dialed up the max pressure at the same time... which was clearly a bad plan.

The burning grains were sent up in a fireworks-display-worthy fashion, generally acknowledged as the most impressive-looking CATO of the weekend.

Flight data logged as sn 3121, flight 5, stored in cato.eeprom.