This paper presents a description of a novel millisecond aerodynamic force measurement technique and the first experiments in hypervelocity flow with a model, which is equipped with laterally blowing jets and a set of accelerometers. A fast-acting mounting support releases the model and grips it again after a free flight duration of some milliseconds. Using measured acceleration and Pitot pressure histories allows direct straightforward time-dependent evaluation of the aerodynamic coefficients. This procedure is insensitive against nonlinearities or disturbances in the starting phase of the flow and compensates flow variations, if the flow is quasistationary and maintains a roughly uniform Mach number. The results quantify the time necessary to establish quasistationary flow for the actual test conditions. Quantitative results are also obtained for the force, which is produced by interaction of side jets and ambient flow and acts on the surface of the model. At the tropospheric hypervelocity conditions of our test, the interaction force on a flat plate substantially increases jet thrust.
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Naumann et al. (1993) studied this question.