MILLISECOND AERODYNAMIC FORCE MEASUREMENT WITH SIDE-JET MODEL IN THE ISL SHOCK TUNNEL

This paper presents a description of a novel millisecond aerodynamic f orce 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 mo del and grips it again after a free flight duration of some millisecon ds. Using measured acceleration and Pitot pressure histories allows di rect straightforward time-dependent evaluation of the aerodynamic coef ficients. This procedure is insensitive against nonlinearities or dist urbances in the starting phase of the now and compensates flow variati ons, if the now is quasistationary and maintains a roughly uniform Mac h number. The results quantify the time necessary to establish quasist ationary 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 tr opospheric hypervelocity conditions of our test, the interaction force on a flat plate substantially increases jet thrust.