Early Dual Burn Motor Test

This is a video of a static test that I conducted back in 2005 when I first got involved with the Sugar Shot project. The dual burn concept is not new, but I haven't heard of any amateurs pursuing it. At this size, I don't think you'd realize much benefit. However, in a slightly larger motor, such as the one that we are currently constructing, you begin to see some real benefits. The concept is similar to staging, but in some ways simpler to execute. One of the major difficulties is that the first half of the casing and the nozzle are subjected to twice the heating that they would have to endure in a two stage design. The motor that we are currently working on has the potential to reach nearly 50,000 feet, which is considerably higher than you would expect to go with a "standard" motor that expends all of it propellant close to the ground in denser air. Despite some minor problems, I considered this early test to be successful. The o-ring on the upper bulkhead was damaged, and I didn't have a replacement. That resulted in a small leak during the 2nd burn. However, there were several key things that did seem to work. Most notably:
The first propellant grain burned properly and ignited the epoxy plug .

The epoxy plug burned through without igniting the second propellant grain.
The burnt remains of the epoxy plug did not obstruct the nozzle.
The mid-bulkhead did not seem to have a significant effect on the 2nd phase thrust.

Norton's Surplus

It's been really busy at work lately; long hours, skipped lunches, etc. I skipped lunch again yesterday, but instead of working through lunch James and I drove over to Norton's Surplus in North Hollywood to look around. Nothing has changed much since the last time I was there. The outside area had been cleaned up quite a bit though, which allowed me to get a picture of a large cylindrical motor that was nearly buried under debris last time. Four or five years ago on my first visit there I noticed a 318mm rocket motor with its nozzle pointed up in the air. It had a bunch of hoses piled in front of it. I was able to climb on top of the pile and snap a few close-up pictures. I'm not sure what it's from, but a quick Google search turned up this photo of a Little John rocket on display at the Smithsonian Air and Space museum that looks very similar. I got the photo from this blog. I took a photo of the inside of the casing . In that photo you can see four "rods" that run the length of the casing. I'm not sure what they were for, maybe they supported the propellant grain or maybe they are resonance rods like those pictured in this diagram of what I believe is a Nike Ajax motor. The nozzle appears to be all steel construction with no throat insert. The entire nozzle is badly rusted, but the throat doesn't seem to have suffered any asymmetrical erosion.

Static Firing Video

I plan to start posting some videos form the past. I'll post them as I find the time, many of them were shot on an analog camcorder and need to be converted to digital. This one is a close up view of the nozzle during the second firing of the ballistic evaluation motor for the Sugar Shot to Space effort. It really illustrate well the amount of heat generated. It was a disappointing test in that the casing failed and we had problems with the data acquisition. You can find the complete report here. It did provide some useful data though and I managed to get some good video.

Minisshot Motor Progress

I started threading the motor components. I've only done the six holes that connect nozzle shell to the nozzle ring, so I have a long way to go. It's exciting that those 12 holes line up so well, though. The nozzle design consists of two main pieces. The purpose is to reduce the amount of heat transfer from the throat region to the composite motor casing. The two pieces are separated by a extremely high temp. gasket. In addition to that, the shell flange has a slightly smaller diameter than the ring so that there is no direct metal to metal contact between the two pieces.

MiniSShot Motor Update

I just completed the mid-bulkhead, pictured in the middle above. That's the last of the major components for the Minisshot motor. There is still a lot to do, not the least of which is to tap the 102 screw holes. It feels good to have the major metal cutting completed though. The next major milestone in my mind is putting all the components together for the first time and seeing how it all fits together. I wonder what the motor assembly time is going to be with all those screws?