Sphere Drag Data at Supersonic Speeds and Low Reynolds Numbers

Drag forces on spheres have been measured in a low-density supersonic wind tunnel. Mach Numbers were from 2.1 to 2.8, and the Reynolds Number (based on free-stream properties and sphere diameter) ranged from 15 to 800. Available experimental data for the same Mach Numbers as the present tests, but with Reynolds Numbers in the order of magnitude 10, showed tha t the drag coefficients could be correlated as a function of Mach Number alone and were not altered by a sixfold change in Reynolds Number. The present data showed an increase of drag coefficient by a factor of 2 y 2 over the test range. Flow visualization photographs indicated a possibility that interaction occurred between the sphere boundary layer and shock wave at low Reynolds Numbers. Additional experimental data are required before the relative importance of viscous, molecular flow, and shock-wave effects can be evaluated completely.