Improvements to a High-Attitude Wind-Tunnel Sting System for Improved Data Quality

Successful wind tunnel testing requires careful attention to how model mounts may affect data quality. In several past sting-mounted tests at the Oran W. Nicks Low-Speed Wind Tunnel (LSWT), the High-Attitude Robotic Sting (HARS) pitch/roll actuator system has been suspected to cause undesirable aerodynamic interference in collected data. The size of the mounting bracket and roll actuator “bullet” fairing causes undesirable upflow at the aft end of sting-mounted models. Furthermore, the motors that drive position of the HARS assembly introduce excessive electronic noise. This makes data collection from sensitive instrumentation like accelerometers nearly impossible. This thesis details the design changes to the HARS system that mitigate these sources of aerodynamic and electronic interference. The HARS bullet was completely redesigned and rebuilt to decrease its diameter from 10.5 inches to 6.0 inches. Additionally, all drive components and motors were replaced by new motors with passive holding brakes to improve functionality and decrease electronic noise. Performance was verified using a 6.25%-scale WB-57 aircraft tested at the LSWT in 2014. Differences in aerodynamic performance data measured by an internal balance were compared and analyzed for differences between the redesigned system and the previous system. Additionally, accelerometer data was compared for differences in noise reduction by the new motors. The redesigned system and components show clear improvements to data quality, both in aerodynamic force and moment coefficients as well as accelerometer data. These improvements will allow more accurate measurements and allow more sensitive measurement techniques to be utilized, expanding the HARS system capabilities