Komerath, N., Hariharan, S., Shukla, D., Patel, S. et al., "The Flying Carpet: Aerodynamic High-Altitude Solar Reflector Design Study," SAE Technical Paper 2017-01-2026, 2017.
Our concept studies indicate that a set of reflectors floated in the upper atmosphere can efficiently reduce radiant forcing into the atmosphere. The cost of reducing the radiant forcing sufficiently to reverse the current rate of Global Warming, is well within reach of global financial resources. This paper summarizes the overall concept and focuses on one of the reflector concepts, the Flying Carpet. The basic element of this reflector array is a rigidized reflector sheet towed behind and above a solar-powered, distributed electric-propelled flying wing. The vehicle rises above 30,480 m (100,000 ft) in the daytime by solar power. At night, the very low wing loading of the sheets enables the system to stay well above the controlled airspace ceiling of 18,288 m (60,000 ft). The concept study results are summarized before going into technical issues in implementation. Flag instability is studied in initial wind tunnel experiments. This has forced evolution of the concept to one similar to a hang-glider, the sheet supporting the propelled wing at very low flight speed. Later designs may dispense with the wing altogether. Lift-induced drag can be minimized by joining several elements together in flight to create a large aspect ratio, and by staggering elements in flight as long-distance birds do, with swarm flight control. The primary parameter is the areal density that can be achieved for the reflector sheet under aerodynamic loads. Successful designs can be closed even with 2-mil Mylar sheets, but going to strengthened versions of solar sails would offer strong advantages. Mass-based cost estimation allows an upper bound on architecture cost by comparing equivalent number of launch masses of a well-known large space launch system. The next level of cost analysis shows that the manufacturing cost which is dominant, is best addressed through automotive industry techniques.