A “Dust Curtain” in Gaseous Core Nuclear Reactors for Rockets

Abstract

THE use of nuclear, rather than chemical, energy for the propulsion of space vehicles would greatly extend the possibilities of space travel, and in recent years much progress has been made towards the realization of nuclear propulsion devices. The principle of rocket propulsion rests on the production of a highly heated working fluid, called the propellant gas, which is expanded and ejected through a nozzle, thereby converting its thermal energy to directed kinetic energy. The heating of the propellant can be derived from the reaction of combustibles with a chemical system, or, in the nuclear system, from the nuclear reaction of fissile materials. In the nuclear reactor the fissile material is the fuel, and the thermal energy released by fission is transferred to the propellant, usually hydrogen. This energy transfer can be achieved by the use of a solid core which serves as an intermediate medium for the energy delivery to the propellant. Although the solid core reactor has reached a prototype engine demonstration after a decade of development¹, it does not, however, make the optimum use of the nuclear energy in a rocket engine. This stems from the fact that fission energy is released at very high level (10⁶ eV or 10¹⁰ K) which has been degraded in a solid core reactor to 3,000 K, the limit of the operational temperature of a solid core heat exchanger. It is therefore desirable to use a gaseous core in which the fuel, namely the highly energetic fission particles, and the propellant are intimately mixed, thus transferring energy directly via collisions and radiation.