Oxidizers, propellant cryogenic

In organizing the symposium, we made the usual division into solid and liquid rocket propellants. Most readers no doubt already know the relative merits of solid vs. liquid systems—viz., the instant readiness of solids (compared with cryogenic liquids), their higher density (important in volume-limited systems), and the relative simplicity of rocket construction liquids offer easy variation in thrust level and the attainment of higher specific impulses, the latter because physical separation permits the use of fuels and oxidizers that would be incompatible if premixed. 

Figure IV. B. 1. concentrates on the storable propellant systems. The morphology obviously can be extended to include the cryogenics. Again, the method by which the metal particles are introduced determines the approach. Both the hybrid and the gelling procedure would be considered. The only perturbation would be in the case of the hybrid in which both fuel and oxidizer are injected as liquids and the binder is used simply as a vehicle to carry the metal particles.

IV. If the fuel or oxidizer has a critical point such that it must be kept at low temperatures in order that it remain liquid throughout the system, then it is termed a cryogenic propellant... 

Petroleum-based propellants are usually made of high-purity refined kerosene, i.e., n-dode-cane (n-C H J denoted by the acronym RP-1. The chemical purity of the petroleum is an important parameter as combustion residues (e.g., soot, coke and tar) must be kept at a minimum to prevent clogging. Petroleum fuels are usually used in combination with liquid oxygen as the oxidizer. Despite dehvering a lower specific impulse than cryogenic fuels, kerosene performs better than hypergolic propellants. 

Combustion temperatures, as indicated in Table I, range from 4000-8000 F. Consequently data on behavior of the propellant at the high temperatures and pressures encountered are necessary in order to evaluate its performance as a coolant. The preheating of the coolant fuel or oxidant also improves the rocket motor efficiency. Cryogenic liquids, particularly the hydrogen—oxygen system, serve well as coolants. 

Liquid propellants can be categorized by their type of storage (cryogenic propellants vs. storable propellants) or by their function in the chemical propulsion system (oxidizers, fuels, or monopropellants). The functional categorization is used here for discussion of the liquid propellants. In addition, liquid propellants, either oxidizer or fuel, can be gelled as a neat material or as a heterogeneous gel mixture containing suspended solid material such as aluminum powder. 

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