Composite Propellants

I've been testing different composite formulas, they can be found in the Experimental Propellants 4 page. This page is password protected, so you'll need to contact me to view it.

I've been working primarily with sugar propellants in the past, I like the inexpensive nature of the sugar based propellant and its locally available ingredients. However, there are numerous drawbacks.

  1. The fast burn rate.
  2. Brittle nature of the propellant.
  3. Low Isp.
  4. Heat casting.

None of the above are terrible problems by themselves, but combined they make for a propellant that can be frustrating to incorporate into a rocket design. Make the propellant less brittle and you lose Isp, slow the burn rate and again lose Isp.

There are many good formulations for composite propellants out there. What I would like to do is come up with a formulation that meets some of my own criteria. I would like to keep the chamber temperature fairly low, have a motor tested Isp of 180 or better, use AP and Mg in only limited amounts.

With those goals in mind, I ordered enough chemicals to keep me busy for a while in the testing phase. I also ordered a large amount of graphite to form nozzles from. My plan is to make graphite inserts and steel nozzle retainers for my motors. That way I can quickly and easily change out graphite nozzles of different throat diameters, as well as use a given graphite nozzle in different size motor casings.

One other thing I needed to work with composites was a vacuum degasser. I have a fairly new ice cream cabinet that had had an internal cabinet coolant leak. The freezer has a huge compressor on it that is in great working condition, so I salvaged the compressor unit and I'm in the process of setting it up as a vacuum pump.

I completed a steel nozzle retainer and graphite insert for use with composite propellants.

Here is the graphite insert and the steel retainer. They fit my 2.25" aluminum casing material.

Here is the assembled nozzle next to the casing.

Here is the insert in the retainer. I'm going to try a little high temp RTV to hold and seal the insert into the retainer. Hopefully the steel around the outside of the graphite won't melt! This graphite insert has a .625" diameter throat for a short burn motor. Of course, new nozzle inserts can be made with any throat size for a variety of propellants and grain geometry.