IMPROVED THERMAL ENERGY STORAGE SYSTEM FOR ADVANCED SOLAR DYNAMIC SPACE POWER GENERATION

CONTAINMENT IS A MAJOR TECHNICAL ISSUE ASSOCIATED WITH THE USE OF HIGH TEMPERATURE PHASE CHANGE MATERIALS (PCM'S) FOR TRANSIENT THERMAL STORAGE IN SOLAR-HEATED SPACECRAFT POWER PLANTS. A NUMBER OF APPROACHES HAVE BEEN EXAMINED TO DATE, BUT NONE IS ENTIRELY SATISFACTORY. THIS PROPOSAL RECOMMENDS FOR STUDY A NEW, PROMISING APPROACH FOR THEIR CONTAINMENT - ONE THAT OFFERS POTENTIALLY SIGNIFICANT ADVANTAGES OVER OTHER CONTAINMENT SYSTEMS. IT IS PROPOSED THAT METALLIC PCM'S BE INCORPORATED INTO THIN, HIGHLY POROUS SHEETS OF CARBON-CARBON COMPOSITE BY HOT ISOSTATIC PRESSING. THESE PCM/CARBON-CARBON SHEETS ARE ENCAPSULATED IN A THIN, CARBON- AND PCM-COMPATIBLE COATING OF SI3N4. THESURFACES OF THE CARBON-CARBON ARE MODIFIED, IF NECESSARY, PRIOR TO INFILTRATION TO MINIMIZE CHEMICAL INTERACTIONS AND PROMOTE WETTING. GERMANIUM IS THE METALLIC PCM SELECTED FORSTUDY IN PHASE I. THE PROPOSED PROGRAM WILL EVALUATE (1) THE FEASIBILITY OF INCORPORATING HIGH TEMPERATURE PCM GERMANIUM INTO CARBON-CARBON AND (2) THE EFFECTIVENESS OF A SI3N4-ENCAPSULATED GE/C-C COMPOSITE HEAT STORAGE SYSTEM IN TERMS OF ITS THERMAL CHARACTERISTICS AND ITS MECHANICAL/CHEMICAL STABILITY UNDER FREEZE-THAW CYCLING.