Evaluation of Hafnium-Carbide Wafers for Use in a Solar Calorimeter.

The Solar Propulsion Group SPG at Phillips Laboratory will determine the efficiency of transferring heat from sunlight to a gas using carbon wafers. There will be a series of tests using a calorimeter containing porous carbon and hafnium carbide coated carbon wafers that will absorb the sunlight and transfer the heat to the gas passing through them. We had half the wafers coated with hafnium carbide to prevent carbon loss in a hydrogen rich atmosphere at high temperatures. They will degrade with each test if they are not suitably coated. We conducted a wafer bake-out test to determine if they were suitable for the calorimeter testing, and to develop a baseline for degradation checks to be conducted throughout the calorimeter test series. The preliminary results indicate that the wafers will be unaffected by the environment in the calorimeter. We developed a weight baseline to use in checking the integrity of the wafers throughout the calorimeter testing. The experiments talked about in this paper are not bi-modal in the strictest sense a single unit supplying both power and propulsion to the spacecraft or satellite. However, in the future, we may find the solarlaser thermal propulsion system that the wafers fit into lends itself to both power and propulsion in a single unit. Therefore, the information is pertinent to this forum.