Jack HILLYER, Luke DOHERTY, Matthew McGILVRAY

DOI Number: N/A

Conference number: HiSST-2025-168

This paper presents experimental results from testing aimed to improve force balance measurements in Ludwieg tunnels. This is achieved by leveraging the extended rise time and test duration of the recently commissioned Extended Ludwieg Mode to 1) investigate the effect of nozzle supply pressure rise time on model/force balance natural frequency excitation and 2) assess the suitability of a 6 Degree of Freedom Inertial Measurement Unit for acceleration compensation. It is demonstrated that for Ludwieg Tunnels, addition of a plenum between the fast acting valve and the nozzle throat can reduce the magnitude of the startup loads – typically an order of magnitude greater than the test loads – and consequently enables use of a balance with a lower full scale range and associated lower uncertainties. Furthermore, it is also shown that the duration of the nozzle startup period, not the overall rise time of the facility nozzle supply trace, dictates which model-balance natural frequencies are excited. Finally, it is demonstrated that a 6 Degree of Freedom Inertial Measurement Unit can be used for acceleration compensation, including use of differentiated gyroscope measurements for moment compensation, potentially alleviating some packaging constraints for accelerometer placement inside the model.

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In Categories: 1.Events, 1.HiSST 2025, Testing & Evaluation
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