ocr: 20-inch Supersonic Wind Tunnel ouiet vave Pressue relael Conical user Variable - second systen Preheat - - Test Ar Supply Settling To vum pheres to quiet valve Chamber Contraction Flexible noute secion assembly or atmosphere 20 Inch Supersonic Wind Tunnel NASA Langley Research Center 11/2/1992 Image # EL-1996-00115