THERMAL ABSORBER FOR A SOLAR-HEATED HYDROGEN ROCKET ENGINE

SOLAR-HEATED HYDROGEN CAN YIELD MORE THAN THREE TIMES THE SPECIFIC IMPULSE OF CHEMICAL REACTIONS FOR ROCKET PROPULSION. THE DEVELOPMENT OF A SOLAR-HEATED HYDROGEN ENGINE DEPENDS ON BREAKTHROUGHS IN HIGH TEMPERATURE MATERIALS. A KEY COMPONENT IS THE SOLAR ABSORBER, WHICH IS HEATED BY FOCUSED SOLAR RADIATION AND THEN TRANSFERS THE HEAT TO THE GASEOUS HYDROGEN PROPELLANT. BY DEVELOPING A POROUS ABSORBER THAT CAN ACHIEVE A PROPELLANT TEMPERATURE OF 3778 K, THE SPECIFIC IMPULSE OF A SOLAR-HEATED HYDROGEN ROCKET CAN BE INCREASED TO 10,385 SECONDS FROM THE PRESENT RHENIUM TUBE LIMIT OF 8,532 SECONDS AT 2778 K. IN THIS PHASE I PROGRAM, ULTRAMET PROPOSES TO DESIGN, FABRICATE, AND TEST A RETICULATE VITREOUS CARBON FOAM SOLAR ABSORBER/HEAT EXCHANGER THAT WILL RESIST TEMPERATURES UP TO 3500OC. THE CARBON FOAM STRUCTURE WILL BE PROTECTED AGAINST CARBON/HYDROGEN REACTIONS BY MEANS OF A REFRACTORY CARBIDE COATING APPLIED BY CHEMICAL VAPOR INFILTRATION (CVI). THE PROPOSED SOLAR ABSORBER WOULD SIGNIFICANTLY INCREASE EITHER MISSION LIFE OR PAYLOAD FOR SPACE MISSIONS REQUIRING HIGH PERFORMANCE. THE AIR FORCE ASTRONAUTICS LABORATORY (EDWARDS AFB) HAS LONG SUPPORTED EFFORTS IN THIS AREA AND WOULD BE A PRIME BENEFICIARY OF SUCCESSFUL RESULTS FROM THE PROPOSED PROGRAM. BOTH NASA AND COMMERCIAL FIRMS INVOLVED IN LONG-TERM AND/OR DEEP-SPACE MISSIONS WOULD ALSO HAVE A STRONG INTEREST IN CARRYING THIS EFFORT TO FRUITION.