The overall objective of the Direct Conversion Technology task is to develop an experimentally verified technology base for promising direct conversion systems that have potential application for energy conservation in the end-use sectors. Initially, two systems were selected for exploratory research and advanced development. These are Alkali Metal Thermal-to-Electric Converter (AMTEC) and Two-Phase Liquid Metal MD Generator (LMMHD). This report describes progress that has been made during the first six months of 1992 on research activities associated with these two systems. (GHH)

The overall objective of the Direct Conversion Technology task is to develop an experimentally verified technology base for promising direct conversion systems that have potential application for energy conservation in the end-use sectors. Initially, two systems were selected for exploratory research and advanced development. These are Alkali Metal Thermal-to-Electric Converter (AMTEC) and Two-Phase Liquid Metal MD Generator (LMMHD). This report describes progress that has been made during the first six months of 1992 on research activities associated with these two systems. (GHH)

Four detailed intercomparisons were made for a number of models of cavity-type self-calibrating radiometers (pyrheliometers). Each intercomparison consisted of simultaneous readings of pyrheliometers at 30-second intervals in runs of 10 minutes, with at least 15 runs per intercomparison. Twenty-seven instruments were in at least one intercomparison, and five were in all four. Summarized results and all raw data are provided from the intercomparisons.

This study has been made to assess the needs, potential benefits and the applicability of early (circa year 2000) Nuclear Electric Propulsion (NEP) technology in conducting NASA science missions. The study goals are: to obtain the performance characteristics of near term NEP technologies; to measure the performance potential of NEP for important OSSA missions; to compare NEP performance with that of conventional chemical propulsion; to identify key NEP system requirements; to clarify and depict the degree of importance NEP might have in advancing NASA space science goals; and to disseminate the results in a format useful to both NEP users and technology developers. This is a mission performance study and precludes investigations of multitudes of new mission operation and systems design issues attendant in a NEP flight.

A phase 2 study has been initiated to investigate surfactant- assisted coal liquefaction, with the objective of quantifying the enhancement in liquid yields and product quality. This report covers the fourth quarter of work. The major accomplishments were (1) Completion of coal liquefaction autoclave reactor runs and related analysis with Illinois {number_sign}6 coal with time as a variable at 375{degree}C, and pressures of 1800 psig; (2) an investigation into the mechanism of the effect that the lignosulfonate surfactant has in enhancing liquefaction yields; and (3) completion of a bench-scale test with the surfactant in the continuous flow Catalytic Two Stage Liquefaction Process (CTSL) reactor at HRI.

We have found that there is a limited range of solid solutions between the skutterudite compounds CoSb{sub 3} and RuSb{sub 2}Te (about 5% on each side). For the system (RuSb{sub 2}Te){sub x}(CoSb{sub 3}){sub 1-x}, preliminary results obtained on one n-type sample on the CoSb{sub 3}-rich side show that these alloys have good thermoelectric properties and a maximum ZT of about 0.89 was obtained at about 600 C. More experiments will be started to investigate the possibility of a broader range of miscibility in this system which would allow an even further decrease in the lattice thermal conductivity, resulting in better thermoelectric properties. IrSb{sub 3} and RuSb{sub 2}Te form a complete range of solid solutions. Hot-pressed samples in this system have shown p-type conductivity. The thermoelectric properties of these p-type alloys have been measured and results have shown that their potential for thermoelectric applications is limited mainly because of the relatively low Seebeck coefficient values for p-type materials. Efforts will be directed on preparing n-type samples of the same alloys by doping with various dopants such as Ni and Pd.