Hot-Wall Reentry Testing in Hypersonic Impulse Facilities

Abstract

Hypersonic testing in impulse facilities replicates various flow characteristics accurately; however, because of the short test times, some phenomena cannot be fully simulated. Previous testing has been conducted with preheated walls up to 800 K; however, this falls well short of the typical temperatures characteristic of ablators in hypervelocity reentry (~2000–3000 K). The concept presented here is to use resistive heating on a carbon–carbon model to preheat the model immediately before conducting a test. This method has enabled testing at wall temperatures in excess of 2000 K in the X2 expansion tube at the University of Queensland. The model used was a short half-cylinder with a diameter-to-length ratio of 4.5 and was tested in a Earth-entry flow monitored by ultraviolet spectrometry. The testing campaign showed that there was a significant increase in the cyanogen formation off the surface of the model when it was heated to 2000 K. This testing demonstrates the viability of the presented method, which will enable a new range of testing to be conducted in impulse facilities with emphasis on hypervelocity flows, in particular those in which the real flight vehicle uses a carbon-based ablator as the thermal protection system.