Hotshot Wind Tunnel Force Measurement

A description is given of an internal balance capable of withstanding tunnel starting loads of the order of twenty times the amplitude of the forces to be measured during brief-duration hotshot tunnel runs. Large starting forces applied as shock loads necessitate inertia compensation to nullify parasitic signals. Quartz sensing elements statically are used. Dynamic response is within one percent of the final value for a duration of three milliseconds. The inertia compensation and compensation coefficient determinations are described. The readout system uses involving analog computation techniques are presented. Typical results are given and the advantages of inertia compensation are described.