An investigation into internal and external force balance configurations for short duration wind tunnels

Abstract

An investigation is undertaken on the accuracy of an external versus an internal stress wave force balance for the measurement of forces and moments on a re-entry type configuration in short duration test flows. Simula-tions performed using a finite element code suggest superior recovery of the applied forces and moments with an external force balance configuration. This is hypothesized to be due to the increased stiffness and decoupling between force components that can be achieved with an external type configuration. An investigative model based on the Pre-X configuration was chosen for the finite element simulations. Due to the typically high angles of attack experienced by such re-entry craft, the influence of an external force balance mounting on the model forces was found to be negligi-ble.