High Energy Laminated Rocket Propellants

Chris, Sun Oct 28 2007, 11:18AM

This is not really meant to be a practical thing, but I find the idea of pushing rocket propellant chemistry to the limits fascinating. Though the method I describe is tedious, and many of these propellants are very hazardous materials that require special handling and demand the utmost respect, I hope to push the limits of solid rocket specific impulse to the max. Since many of these propellants are difficult and expensive to synthesize or obtain, this mainly applies to rather small engines.

I have considered the possibility of some very energetic and reactive solid fuels and oxidizers for rocket engines. Examples of some of these fuels are lithium hydride and other light metal hydrides or borohydrides or light metals themselves such as lithium, sodium, or beryllium, or other things like cubane (actually quite safe/stable), decaborane or mixtures thereof, or mixtures containing hydroxylamine. Some of the possible oxidizers are N2O5 (very volatile) or other nitronium salts, perfluorate or fluorate salts, mixtures containing hydroxylammonium salts, or alkali metal peroxides and superoxides. I have been considering combinations of many of these with each other or with other less exotic propellants.

Clearly many of these propellants are so sensitive and reactive that they could not even come in contact with each other, much less be mixed into a composite propellant. They would simply explode, many as soon as they came into contact. Some of them are quite volatile, subliming solids, and some of them are very pyrophoric and cannot even be handled outside of an inert atmosphere. As a method to allow them to be used anyway, I have proposed laminate propellants.

For core burning or ring burning designs the fuel or oxidizer constituents would be individually cast or grown into solid plates of appropriate thickness with strochiometric mass and a hole in the center for the burn chamber. They could be combined with a suitable fibrous material such as fiberglass or steel wool (where compatible) for strength, or cast or grown as a single crystal plate. The plates of fuel and oxidizer material would then be stacked alternately in the rocket tube throughout its length and glued or mounted in with a thin dividing layer between each. A protective lining would then be applied to the inside of the burn chamber, and a line or layer of flash powder or similar would be applied down its length, bridging all the plates. This would be connected to an electric ignition, and the burn chamber would be sealed with argon gas inside by a cover film over the nozzle. Some of the more volatile propellants would require that the rocket be kept refrigerated until ignition.

The basic equipment needed for building such rockets would include an isolation glove box, possibly refrigerated, casting trays, and most importantly thorough knowledge of the properties and compatibilities of each of the propellant constituents, as well as testing with small samples.

A thickness for the plates would have to be chosen, probably through experimentation, so that the burn rate would be controlled, and yet the burn is even and complete. There could be issues regarding differing melting points of thermal conductivity of the different constituents, and there may be other unexpected issues with the burn rates of the plates.

Suggestions? Criticism? Comments? All are welcome.