In 1962, JPL conducted research in low-density gas dynamics, studying the drag on a sphere in a supersonic low-density flow environment, at various temperatures and speeds (Mach 1.8 to 4.4). Experiments were conducted in JPL’s Low Density Wind Tunnel. Nozzles were wrapped in a copper coil containing liquid nitrogen to cool the apparatus. A steel or bronze ball from 1/32 to 1/8 inch in size was suspended from fine tungsten wire in the jet. Two 8 mm movie projector lamps with built-in reflectors were placed at the edge of the jet and used to raise the sphere temperature to about 1,000 kelvins.