Static Test 77

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This test is almost an exact repeat of static test 76, using the exact same grains cast at the same time. The only change was that I added one more grain to increase the Kn. The results are interesting...

Total Propellant Weight: 1.492 pounds, 677.1 grams

Number of Grains: 7

Total Grain Length: 13.86"

Core Diameter: .5"

Nozzle Diameter: .435"

Kn: 317 initial, 338 maximum, 243 ending

Here's the thrust/time curve of the test.

Burn Time: 2.917 seconds

Total Impulse: 183.78 pound seconds

Isp: 123.12

Peak Thrust: 114.7 pounds

Peak Chamber Pressure: ~560 psi (estimated)

Looking at the curve, it's apparent I need to move the Kn the other direction, that is, with a progressive burn. The Isp was much better at 123, I suspect if more neutral burn can be achieved, the Isp will increase even more. The burn time was very good at still almost 3 seconds.