Thermal Modeling and Performance Measurements of Radiometric Arrays for Near Space Propulsion

: A propulsion system based on an array of radiometer vanes has been proposed for wind disturbance correction on near space vehicles. The radiometric force is produced by a vane due to a temperature gradient between a surface heated by insolation and a convectively cooled surface. Previous research has identified several key parameters that might affect the thrust produced by a radiometer array. These parameters include the heat transfer mechanisms on the individual vanes and between nearby vanes in an array, the proximity or spacing of radiometer vanes in an operational array, the effects of the vanes attached to a near space vehicle operating in the boundary layer near the surface of the vehicle, and the effects of attaching the vanes to a substrate on the vehicle itself. A combined numerical and experimental approach was used to investigate these effects. Numerical codes were used to assess the heat transfer mechanisms and the boundary layer flow. Experiments were designed and carried out to measure the force produced by a small array of radiometers. These results were combined to assess the performance of a notional array of radiometer vanes for the purpose of counteracting drag on a near space vehicle operating at an altitude of 60 km. The array performance was assessed based on the maximum force that can be produced as a function of array mass and area.