The results of a rocket vehicle study indicate that nuclearpowered rocket vehicles will be lighter than comparable chemically powered vehicles for vehicle velocities greater than 15,000 ft/sec with payload weights of 1000 to 10,000 lb, or for vehicle velocities greater than 7000 ft/sec with payload weights greater than 10,000 lb. The reactor core design study shows that high reactor core bulk power densities might be achieved without an undue gas pressure drop across the reactor or an excessive temperature drop from the fuel element to the gas. The best core design appears to be one that utilizes thin, parallel, solid graphite plates as the heattransfer elements. Since the propellant gases are predominantly hydrogen, the use of graphite as the basic structural material will require the development of a hydrogenresistant coating to be applied to the surfaces of the graphite heat-transfer elements of the reactor core in order to inhibit chemical reactions between the gas and the graphite. The feasibility of the reactor core designs considered thus depends on the efficacy of the protective coatings proposed for the graphite heat-transfer elements. Thus the first step in a program of development of a nuclear rocket should be an experimental investigation of protective …

A Pu-Al alloy containing 4 at. % Ad showed no attack after exposure to purified NaK for one month at 400 deg C in the absence of any oxide. The same specimen and other Pu alloys, including pure Pu, showed marked deterioration in shorter exposures in the presence of oxide fllms from a welded stainless steel container. Pure U was found to be resistant in the presence of such oxides. (auth)

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