Description: NASA Langley Arc-Heated Scramjet Test Facility: Langley 100-Foot Diameter Vacuum Sphere. This is a photograph of the 100-foot diameter vacuum sphere, located behind Building 1247-B. The photo was taken in 1963, several years prior to construction of the Mach 7 Scramjet Test Facility (now called the Arc-Heated Scramjet Test Facility). The facility under construction in 1963 was the Four-Foot Hypersonic Arc Tunnel. It was used for tests of reentry vehicles, such as the Apollo module, at Mach numbers up to 16. Note the facility after cooler on the right-hand side of the photograph (should be left; picture is reversed) which has not yet been connected to the vacuum sphere. Note also that the 1247-B steam ejector had not yet been installed; instead, the 100-foot diameter vacuum sphere could be evacuated to a few microns of mercury pressure using mechanical pumps and diffusion pumps.