Test 2017-12
5 grain 75mm sorbitol motor with pyrodex pellet ignition in 4-inch Wildman rebuilt airframe at NCR North.
Trimmed CTI 5-grain case (25.75" overall), Loki #42 nozzle, CTI aft closure ring, 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.
Liner 23.125" long with about 22.25" available for fuel load.
Simulation says this is a 57% L-1366 with 3804 Ns total impulse, 797 psi max, 76% volume loading, and about 2.6 seconds burn time.
| CTI mod Sorbitol | |||||
|---|---|---|---|---|---|
| Rating: | 57% L-1366 | Max Pressure: | 5.5 MPa | ||
| Total Impulse: | 3804 Ns | Specific Impulse: | 131 s | ||
| Max Thrust: | 1706 N | Volume Loading: | 76% | ||
| Average Thrust: | 1366 N | Fuel Mass: | 2958 g | ||
Neglected to re-weigh grains after trimming and before epoxying into the liner. These were the pre-trim masses:
- Grain 2017-7-1, 590g gross, 574g net, trimmed to 4.5" long
- Grain 2017-7-2, 594g gross, 578g net, trimmed to 4.5" long
- Grain 2017-7-3, 592g gross, 576g net, trimmed to 4.5" long
- Grain 2017-7-4, 584g gross, 568g net, trimmed to 4.4375" long
- Grain 2017-7-5, 580g gross, 564g net, cut to 4" long
Total propellant load thus somewhat less than 2860g.
Results
Had to trim grains to fit. Four just required squaring up the ends and trimming excess casting tube away. Fifth one was cut in miter box with saw.
O-rings made forward closure a very snug fit.
Flight data logged as sn 3121, flight 3 on 2017-10-08. 8353 ft apogee, Mach 0.7, 3.4 sec boost.