Static Test 70

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I had some KN/XY grains cast from the XL-4 batch on the Xylitol page, they weren't the best grains in the world. They were cast in cardboard tubes that weren't perfectly round, I had cut off some ends of the grains to see how they were curing so the grains were short, and I drilled the cores out and didn't get them centered very well. All that said, the only thing I could do with them was re-melt them or test them in a motor. These are the only grains I had on hand that were totally cured, so I decided to burn them in the T-4 motor.

I should note, these grains have been sitting for about 4 weeks, they fully cured in that time to a very hard state. The drilling of the cores was much easier than with regular KN/SU propellant as there was very little "gumming" of the drill bit. The drilling process left a very fine powder, and a very smooth hole.

I didn't even have an accurate weight on the grains because I didn't know the weight of the paper casting tubes. So the numbers from the test are "iffy" at best. But it does give me a general idea of burn rate, ignition properties etc.

Grain Number: (Estimations for the most part)

Grains: 4) at 2" long, 1.4" diameter with a .625" core

Grain Weight: .6111 pounds

Nozzle Throat: .42" diameter

Kn: 184 initial, 190 max, 166 ending

Here is the thrust time curve from the test.

Burn Time: 2.2 seconds

Peak Thrust: 55.8 pounds

Total Impulse: 73.52 pound seconds

Isp: ~120

Note the long burn and the slow tapering off of thrust. That's partly due to the poorly center cores I'm sure, and partly due to the grain geometry. I used one of my regular igniters, with no ignition enhancement. I was pleased at the quick build up of thrust, while the propellant is harder to get burning in the open air, it does seem to ignite fairly quickly in a motor.