The free flight technique (C4/was extended to low density flows to measure sphere drag at approximately Mach 15 over a free stream Knudsen number range of .0027 to .25. Comparison of the data obtained with those of other investigators indicates that: 7he free flight technique is useful for shock tunnel measurements of aerodynamic forces in non-continuum flows., '-b) There is little to choose from betweena, a correlating variable for experimental sphere drag coefficients. c) 6 The parameter"'CD

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... GD? ields a useful correlation of sphere drag over a wide ra g.-gya.numbers, Reynolds number and wall Temperatures. -7 =7. * These data and the comparisons with other data first appeared as part of Ref. 2. -I-B, 6uilag ow idS ,uSEqg end elI on W& 4e~No Ma. We okews " cam be low Ife a OsldwO wd Me. Arr J A 6"' I0W1S~_" P,