Research efforts are being conducted by the NASA Lewis Research Center to formulate and characterize the properties of Al/RP-1 and RP-1 gelled propellants for rocket propulsion systems. Twenty four different compositions of gelled fuels were formulated with 5 and 16 micron, atomized aluminum powder in RP-1. The total solids concentration in the propellant varied from 5 to 60 wt percent. Tests were conducted to evaluate the stability and rheological characteristics of the fuels. Physical separation of the solids occurred in fuels with less than 50 wt percent solids concentration. The rheological characteristics of the Al/RP-1 fuels varied with solids concentration. Both thixotropic and rheopectic gel behavior were observed. The unmetallized RP-1 gels, which were formulated by a different technique than the Al/RP-1 gels, were highly viscoelastic. A history of research efforts which were conducted to formulate and characterize the properties of metallized propellants for various applications is also given.

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Characterization of aluminum/RP-1 gel propellant properties

: The Army is interested in those fuels that have a high-energy content per unit volume and therefore result in increased payload capabilities and/or extended operational range of the vehicle. A series of screening processes are being used to identify those fuels and/or fuel components that could result in an increase of 10 percent in the range of the vehicle without an increase in the fuel tank size, i.e., fuels with a high-energy content percent volume. The chemical and physical properties of various candidate fuels and fuel components are described. The fuel components included both liquids and solids (at room temperature). The blending of the various components and the characterization of the resulting fuels are outlined. Solubility studies were done on some of the solid components to assist in obtaining the resulting fuel in the more desirable liquid state. Those solid components, such as anthracene, that were insoluble in the tests conducted but judged to have good high-energy potential, were studied as slurries. Catalyzed 'carbon black' was investigated. Settling studies with carbonaceous fuels included the effect of temperature upon the stability, the stability of FRF-carbon slurries, and the refinement of the previously reported 'Freezing Tube Technique' for measuring stability. Impact dispersion tests were conducted to study the fire-safety characteristics of energy-augmented fuels. The screening of candidate fuels with the Petter engine is described in detail. Other engine studies with the CLR engine are also included.

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Development of Army High-Energy Fuel for Diesel/Turbine-Powered Surface Equipment. Phase II

: A convenient apparatus for dispersing uniform clouds of solid particles for laboratory dust-flame experiments has been tested. The combustion characteristics of premixed laminar graphite-oxygen-nitrogen flames, both with and without added hydrocarbon, have been studied at atmospheric pressure. The variation of particle burning time with initial oxygen partial pressure and oxygen/fuel ratio has been described by first-order combustion kinetics, with due consideration for oxygen depletion during burnout. Flame velocity measurements indicate very slow propagation of the above mixes when compared with that of hydrocarbon sprays and aluminum clouds of similar particle diameter and concentration. Added chlorine did not measurably affect graphite combustion up to concentrations of 2.5 vol. % in the presence of added hydrocarbon, but mixes of less than 0.8 vol. % of chlorine extinguished pure graphite-oxygen flames. The addition of 1.5 to 4.75 wt. % of lead acetate visibly stabilized the graphite-oxygen flame, but the effect on the flame velocity and burning rate could not be measured. Stable suspensions of 60 wt. % carbon black in various hydrocarbons have been prepared. The initial phases of the chemical and physical properties evaluation of these are reported. (Author)

J. T. Bryant

Papers

Ramjet Fuel Studies. Part 1. Carbon.