Free-Flight Measurements of Sphere Drag at Subsonic, Transonic, Supersonic, and Hypersonic Speeds for Continuum, Transition, and Near-Free- Molecular Flow Conditions

Abstract : A comprehensive set of measurements was made in a ballistic range which permits the sphere drag coefficient to be derived with an uncertainty of approximately +2 or -2 percent in the flight regime 0.1 < M < 6.0 and 20 < Re < 100,000 for Tw/T approx = 1.0. Sufficient information is also presented to predict the effect of wall temperature on sphere drag coefficient when Tw/T is not = 1.0 for 2 < M < 6. This investigation represents the most comprehensive experimental program to date to define sphere drag in the velocity-altitude regime applicable to the falling sphere technique for defining upper air density.