Well November went by and I didn't get much done on the new motor. I did do a little testing with Erythritol based propellant. My first attempt was a little surprising given the fact that others have expressed that the combination is really easy to work with and cast. I found that the Erythritol based propellant "froze" quickly once removed from the heat source. Casting was challenging at best. I think there may be at least a couple of different factors at play. In my initial attempt I used a stainless steel pot which has thin walls and not much ability to retain heat. The other possible factor is the brand that I used. In contrast to the pure white Erythritol that other experimenters are using the brand that I have seems to have a hint of color which means that it may have some contaminant that is affecting it. I don't think that the quick freezing of the propellant is something that could not be overcome, but since I tend to cast out at the RRS facility where it's difficult to escape the wind and sometime surprisingly cold weather. Since I have around 50 lbs. of Sorbitol I decided to try an alloy of fuel consisting of 50/50 Sorbitol/Erythritol. This combination cast very well and was cured enough to remove from the mould after about 1.5 hours. A test strand had a burn rate that fell right in the middle of KNSB and KN/ER, so I'm expecting motor performance to be roughly the average of the the two fuels. Expected chamber pressure is expected to be around 1250psi.
The first image at the bottom is a sample segment of KN/ER, the middle image is a segment of KN/ER/SB, and the top image is a frame of the test strand burn test of the KN/ER/SB.
The RRS Christmas party/launch where I was expecting to test this motor was canceled this year so I'm hoping to find some time between Christmas and New Years to test.