Comparative Surface Heat Transfer Measurements in Hypervelocity Flow

Abstract

Reliable prediction of the high heat transfer rates experienced during the hypersonic portion of planetary entry and descent is critical to vehicle survival. Two types of sensors that can be used to measure surface heat flux are coaxial thermocouple gages and thin film resistance thermometers. Individually, both types of gages have been used successfully in a number of studies [1–19]. Both thermocouple and thin film gages measure surface temperature from which heat transfer can be calculated. Both have µs response times, and can be flush-mounted in models. Coaxial thermocouples are robust, can survive challenging experimental conditions, and are typically used in higher enthalpy flows. Thin film resistance gages typically provide improved signal levels, but are less robust, have to be individually calibrated, and are typically used in lower enthalpy flows. As a result, there are few studies which directly compare measurements from the two types of gages. In the present work, we perform experimental measurements at a range of intermediate enthalpies in hypervelocity flow and make direct comparisons between temperature histories and heat flux data obtained from thermocouple and thin film gages.