This test used CXP22 propellant formula.
Burn Time: 1.784 seconds
Total Impulse: 165.05 pound seconds
Isp: 140.6
Maximum Thrust: 166.76 pounds
Average Thrust: 93.47 pounds
Maximum Pressure: 420 psi (calculated)
Kn: 114 to 124 max
Here is the motor at thrust. Click here for the video.
Here is a chart of the time thrust curve.
This test had a several things going against it. First, the nozzle was not optimized with the proper expansion ratio. Second, I cast one grain with a smaller core which would result in the end of the burn having a very low Kn. Third, I was running it at a very low Kn overall. That was on purpose for this first test, but it resulted in very low chamber pressure. So the Isp of just 140 was expected, I think with an optimized design I'll get an Isp of around 160 or better.
With that in mind, I was very pleased with the results. If you look at the graph above, you see a spike at the onset of thrust, I'm sure that was the caused by the igniter. The curve then follows a nice rapid increase in thrust then levels off to a stable increase. I'm not sure about the little hump at the top, then the thrust drops off steadily, the tail end of low thrust is no doubt the top grain with the smaller core still burning. The little spike at the end is the PVC spacer being ejected. With a shorter grain I decided I wanted the extra thermal protection the PVC would supply, I kind of figured it would be ejected anyway.
I was anxious to see how the EPDM rubber liner held up. As you can see in the photo above, it did very well. The liner slid right out.
Here is the seam side of the liner. It held up very well too. The aluminum casing was in clean, pristine condition.