Experimental and Numerical Investigations on HYFLEX Gap Heating: Phase 1

In 1996, NASDA and NAL performed a flight test of the hypersonic entry vehicle HYFLEX This vehicle was a hypersonic test bed. In particular, thermal measurements were performed in the gaps between the tiles of the thermal protection windward side. Unexpected discrepancies were observed with the design predictions of the gap heating based on correlations developed for the Space Shuttle. In the frame of an ESA-NASDA co-operation agreement, a. study is being performed to further investigate this problem, with ONERA as a prime contractor, DLR and EADS/LV. This study started with a literature survey to analyse the correlations available for such a situation. Then ground testing experiments were carried out to validate the aerothermodynamics and thermal numerical tools that can be used to consolidate the flight rebuilding and propose a ground-to-flight extrapolation methodology. This paper describes the tests as well as the numerical rebuilding of the flow-field in one of the test conditions together with the thermal rebuilding. The lessons learned from this first phase have been used to direct the second phase of the work that started recently and aims at the completion of the validation of the numerical models and the methodology, as well as the rebuilding of the flight data.