Thermionic converters for an Integrated Solar Upper Stage (ISUS)

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:438817

Anderson, W G; Horner-Richardson, K ^[1]

---

1. Thermacore, Inc., Lancaster, PA (United States)

The Integrated Solar Upper Stage (ISUS) is a solar bimodal system which combines thermal propulsion and electric power generation in a single integrated system. A thermionic converter was designed and fabricated for the ISUS system. The ISUS thermionic energy converters differ from previous designs, due to the significant changes in operating temperature prior to and during an eclipse, with the emitter temperature increasing from 1,900 K to 2,200 K, and then back again. A complete thermal and electrical model was developed for a planar diode to determine optimum operating dimensions and parameters. The model includes an overall energy balance for the diode, and changes the interelectrode gap spacing due to thermal expansion of the parts as the emitter and/or collector temperatures change. Cesium pressure can be chosen from an external liquid reservoir, an integral reservoir using cesium intercalated into graphite attached to the collector heat pipe, or optimum cesium pressure. With optimum cesium pressure, the maximum efficiency increases from 14% to 16% as the emitter temperature increases from 1,900 K to 2,200 K. The improvement in efficiency is only 2% as the emitter temperature is increased. Optimum efficiency requires an external, actively controlled liquid reservoir.

• OSTI ID: 438817
• Report Number(s): CONF-960805--
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
30 DIRECT ENERGY CONVERSION
DESIGN
HEAT SOURCES
MATHEMATICAL MODELS
NESDPS Office of Nuclear Energy Space and Defense Power Systems
OPERATION
PERFORMANCE
SPACECRAFT POWER SUPPLIES
THERMIONIC CONVERTERS
THERMIONIC DIODES