Thermionic Capabilities and Potential Applications

As can be surmised from my discussion, Air Force conceptual system work is directed toward eventual solar and nuclear applications. Because of weight and volume limitations posed by launch vehicles, solar thermionic generators will probably be limited to the upper limit of 3 - 5 kw. Beyond this power level it is expected that nuclear thermionic power generators will take over but these generators are most promising from the 50 kw power level upward. At low power levels below 1 kw isotope heated thermionic generators appear very feasible and for certain ground applications chemically fueled thermionic generators may prove feasible. Although thermionic power systems are five to ten years away from mission application fundamental concepts for their utilization are being investigated. When utilized with solar energy, thermionic converters will probably be mounted inside a cavity. Solar energy will enter the cavity through a small aperture and the entire generator will be mounted at the focal point of a parabolic reflector. This design concept permits rather compact units or modules and minimizes re-radiation losses from the extremely hot emitter surfaces. By the end of 1963 ground based tests of such designs should be complete enough to determine the basic feasibility of such a power system for space applications. Although ground based experiments cannot exactly duplicate space conditions and rather elaborate vacuum systems are required to eliminate oxygen and nitrogen from the system, it is believed that feasibility of the concept can be proven.