INTEGRATED force and moment data are crucial for the success-ful development of aerodynamic and aeropropulsive systems.

With engine integration into the airframe of hypersonic flight vehicles, such as in the HyperX scramjet experiment, 1 the operation of the engine has a significant influence on the aerodynamic performance of the entire vehicle. It would be advantageous in such cases to be able to make ground-test measurements of the aerodynamic performance of the vehicle with the engines operating. However when it comes to hypersonic vehicles, reproducing hypersonic flight conditions above Mach 8 on the ground is usually restricted to impulse tunnels with test times lasting only several milliseconds. These short test times preclude the use of conventional force-balance techniques for models of typical size. 2 Because of the difficulties in measuring the aerodynamic performance of fueled scramjet-integrated vehicles, separate component tests are sometimes combined or integrated with theoretical analysis or computational-fluid-dynamics (CFD) calculations to determine the overall performance of a vehicle (eg, Refs. 3 and 4). Most of the testing that has been done to directly measure forces associated with combusting scramjet engines has been restricted to direct-connect tests in facilities with longer duration flows, such as vitiated-air blowdown tunnels (eg, Refs. 5 and 6). Advances have been made in the past decade on techniques for measuring forces in flows with very short durations, such as occur in impulse hypersonic facilities (eg, Refs. 7–9). One technique, which has been shown to be quite suitable for force measurement in impulse facilities, is the stress-wave force-balance technique, originally proposed for single-component (drag) force measurement. 10 This technique has been extended for measurement of the three components of force on a cone at incidence11 and has been used to measure the thrust produced by scramjet vehicles, with fuel injection