A mixed radiative-convective technique for the calibration of heat flux sensors in hypersonic flow

The ability to measure the very high heat fluxes that typically occur during the hypersonic re-entry phase of space vehicles is generally considered a subject of great importance in the aerospace field. Most of the sensors used forthese measurements need to be checked periodically and re-calibrated accordingly. Another bottleneck relates tothe need to procure thermal sources that are able to generate reliable reference heat fluxes in the range between100 and 1000 kW/m ² (as order of magnitude). In the present study, a method is presented by which, starting froma calibration system with a capacity of approximately 500 kW/m ² only, heat fluxes in the range of interest forhypersonic applications are generated. The related procedure takes advantage of established standards for thecharacterization of a radiative heat flux. It also builds on the hybrid radiative-convective nature of typicalhypersonic heat fluxes and the yet poorly explored possibility to use convective sources of heat to producehigh-intensity fluxes. The reliability of such a strategy has been tested using a high enthalpy supersonic flowfacility relying on an electric arc-heater and pure Nitrogen as work gas.