Free-Flight Models in Wind Tunnels

A radio telemetry system is described which permits the acquisition of aerodynamic data from free-flight models in wind tunnels. Small transistorized telemeters are used. The telemeters are frequency modulated by either variable-capacitance pressure transducers or by variable-resistance heat-transfer transducers. The models are generally recovered intact after tunnel runs, allowing repeated runs using a single model and permitting recalibrations to verify that no calibration changes have occurred. As many as four channels of data have been recorded simultaneously from a single model at Mach 20. These were base pressure and heat-transfer rate, and forebody surface pressure and heat-transfer rate on 9-deg half-angle, blunt cone models. Several single-channel, base-pressure measurements have been made on 10-deg half-angle, sharp cone models at Mach numbers of 4, 8, and 10. Sample aerodynamic data transmitted during these tests are presented to illustrate the performance of these telemetry systems.