Abstract :
The NASA program for applied research and technology (ART) in thermionic energy conversion (TEC) comprises in-house, university-grant, and industrial-contract studies. In a few years this TEC-ART program has produced important results. Although many of these accomplishments are incremental, their integration has yielded performance gains and the knowledge necessary to direct future work. The current emphasis on out-of-core thermionics allows materials and designs previously prohibited by in-core nucleonics and geometrics. The additional degrees of freedom offer new potentialities. But as always high-temperature material effects will determine the level and lifetime of TEC performance: New electrodes must not only raise power outputs but also maintain them regardless of emitter-vapor deposition on collectors. In addition effective electrodes must serve compatibly with hot-shell alloys. Then, of course, space TEC must withstand external and internal high-temperature vaporization problems. And terrestrial TEC must tolerate hot corrosive atmospheres outside and near-vacuum inside. Finally reduction of losses between converter electrodes is essential even though rather demanding geometrics appear to be required for some modes of enhanced operation. In these and other areas from basic material characterizations to possible system definitions, significant progress is being made in the NASA TEC-ART Program.
