Re-design of the Strain Gauge Force Balances for the Hypersonic Vacuum Wind Tunnel Göttingen

Abstract

The prediction of the flight stability and of the aerodynamic coefficients in the transition region between the rarefied and the continuum flow regime is important for the design of hypersonic vehicles. For the experimental investigations forces as low as 1 "mN" have to be measured. A corresponding force measurement technique has been re-established on the basis of a former force measurement technique for the 2nd test section of the Hypersonic Vacuum Wind Tunnel Göttingen (V2G) partly within the frame of the EU FAST20XX project. This report describes briefly the wind tunnel facility and, from the operating method resulting, the challenges and constraints. It concentrates on the balance frame design and its analytical pre-estimation, but also on the strain gauge selection, circuitry and the resulting operating conditions. It also explains the construction process and how typical mistakes can be avoided. Furthermore the report describes in detail the calibration procedure and compares the result to the analytical pre-estimation. It also gives a brief overview of the first measurement campaign, which could already been numerically rebuild by CIRA by means of CFD and DSMC calculation. Finally the report gives an overview of the next steps and provides advice for further improvements of this force measurement technique.