High Temperature Hypersonic Force Measurement System

The use of electrical foil strain gages to measure aerodynamic loads on sting balances during wind tunnel testing has been extremely successful for relatively low temperature applications. Problems arise, however, in strain gages when the wind tunnel is operated at high temperatures. The bonding agent used to attach the sensor to the specimen often limits the maximum working temperature of the gage to below approximately 650º F. Another important disadvantage of the electrical foil gage is their sensitivity to electromagnetic interference (EMI). Previous work by AEDC and Virginia Tech investigated the ability to use optical fiber-optic based strain and temperature sensors in lieu of foil strain gages to improve wind tunnel force balance capabilities. Absolute optical fiber sensors were found to offer many advantages over conventional foil strain-gage technology (e.g., increased frequency response, increased temperature range, EMI immunity, multiplexing, and decreased size). During Phase I, Lambda Instruments, Inc. proposes to build upon previous successful results obtained by AEDC, Virginia Tech, and the Lambda PI to investigate the feasibility of extending the temperature rating of an optical fiber sensor-based force balance up to 900 ºF.