Wind tunnel tests of a Gerdien capacitor vehicle combination

Wind tunnel tests at MIT and AEDC of a rocket borne upper atmospheric probe for measuring atmospheric charge density are reported. The Gerdien capacitor probe consists of a short section of a coaxial capacitor. This is mounted on pylons from a model of the Tomahawk vehicle. Results are reported for the Mach number range 2 to 4 and altitude range 38 to 95 Km and compared with previous data. Over this range the ratio of mass flow through the probe to mass flow in an equal cross section of the free stream ranged from .2 to .80. Reported measurements extend the range of altitude and Mach number for which data is available. Best correlation of mass capture efficiency is obtained as a function of the viscous interaction parameter M times square root of Re. In terms of this parameter capture efficiency exhibits a minimum of .2 at 50; rising to 0.5 at 15 and .8 at 1000.