Thermionic generator for re-entry vehicles

A novel design of a thermionic generator for use on re-entry vehicles is analyzed analytically and experimentally. Equations are derived for prediction of the output current, output power, and conditions of maximum power for the device. The electrical power output potential of a typical re-entry vehicle is obtained by solving the temperature history of a thin-walled emitter. Given the wall temperature and the work function, the saturated Richardson current is easily obtained. Other parameters needed for predicting output power are obtained from curves in the literature. To simulate re-entry conditions, a test model was built and inserted in either a nitrogen or argon plasma jet. Graphite, thoriated tungsten, tungsten and molybdenum were used for the emitter and collector. Of the materials tested, graphite was the only material that met, to some degree, the qualifications needed for operation of the hypersonic plasma thermionic generator.