These systems are distinguished by their use of new technologies for converting heat from radioisotope fuel into electrical power. The technologies are intended for use in improved radioisotope-power systems, which could provide higher efficiencies and power levels than those used on existing devices, enabling more sophisticated science instruments and spacecraft subsystems. The awards cover several distinct power-conversion technology areas: Thermoelectrics, Thermophotovoltaics, Stirling Engines, and Brayton Engines.

"With this award, NASA is laying the foundation for several technology paths that could enable entirely new classes of missions, from networked science stations on Mars to small spacecraft capable of complex maneuvers in deep space using high-performance electric thrusters," said Dr. George Schmidt, Program Executive for Radioisotope Power Systems at NASA Headquarters. "These new technologies could greatly expand the nation's ability to conduct future robotic planetary-exploration missions in deep space, or in mobile laboratories on the surfaces of planets and moons," he said.

Thermoelectrics, the thermal-to-electric power conversion method used on NASA missions since the early 1960s, has the advantage of employing no moving parts. Proposals selected in this area will concentrate on research of new thermoelectric materials and structures, and could achieve up to two-fold improvements in efficiency over existing systems. The Principal Investigators (PIs) selected by NASA's Office of Space Science:

• Mildred Dresselhaus (Massachusetts Institute of Technology, Cambridge, Mass.): 'Si-Ge Nanocomposites for Radioisotope Power Conversion'
• Saeid Ghamatay (Hi-Z Technology Inc., San Diego): 'Multiwatt Quantum Well Thermoelectric'
• David Moul (Teledyne Energy Systems Inc., Hunt Valley, Md.): 'Segmented BiTe/PbTe-BiTe/TAGS/PbSnTe Thermoelectric Generators'
• Ben Heshmatpour (Teledyne Energy Systems Inc., Hunt Valley, Md.): 'Advanced Superlattice BiTe-PbTe/TAGS Milliwatt Radioisotope Power Systems'

Thermophotovoltaics, another method requiring no moving parts, operates similar to solar cells by converting electromagnetic radiation of heat to electric current. It could double or triple current generator efficiency. Selected PIs:

• Christopher Crowley (Creare Inc., Hanover, N.H.): 'Thermophotovoltaic Power Conversion Technology for Radioisotope Power Systems'
• William Horne (EDTEK Inc., Kent, Wash.): 'Thermophotovoltaic Radioisotope Power Conversion Technology'
• Samar Sinharoy (Essential Research Inc., Brookpark, Ohio): 'A Very High Thermophotovoltaic Converter for the General Purpose Heat Source'

Stirling Cycle Engines (SCE) have the potential of achieving efficiencies three-to-four times greater than existing systems. SCE have been used in space for sensor cooling and cryogenic storage. The selected PIs:

• James Wood (Sunpower Inc., Athens, Ohio): 'Development of a High-Performance Next-Generation Stirling Radioisotope Power Converter'
• Mounir Ibrahim (Cleveland State University, Cleveland): 'Developing the Next-Generation Stirling Engine Regenerator: Designing for Application of Microfabrication Techniques and for Enhanced Reliability and Performance in Space Applications'

Brayton Cycle Engines offer the potential of achieving very high efficiencies and could have the advantage of being compact and scaleable to higher power levels. The proposal selected in this area will apply microfabrication techniques to build and demonstrate a Brayton converter. The selected PI is Mark Zagarola (Creare Inc., Hanover, N.H.): 'A Turbo- Brayton Power System for Radioisotope Power Conversion.'

Each award covers three, one-year performance periods. Continued support from one period to the next is contingent on program need, availability of funds, and each PI team's ability to meet proposed milestones. The total funding for this Research Announcement is $43 million, split into $13.4 million, $7.5 million, $16.9 million and $5.2 million increments for fiscal year 2003 through 2006 respectively.

Project Prometheus, the Nuclear Systems Program, in the Office of Space Science, NASA Headquarters, manages the radioisotope power systems research and development. The Department of Energy, a key partner in this effort, develops the units used in flight applications. Project Prometheus is supported by NASA's Glenn Research Center, Cleveland; Jet Propulsion Laboratory, Pasadena, Calif.; Marshall Space Flight Center, Huntsville, Ala.; and Kennedy Space Center, Fla.