Recommendations for Hypersonic Boundary Layer Transition Flight Testing

Abstract

Much has been learned about the physics underlying the transition process at supersonic and hypersonic speeds through years of analysis, experiment and computation. Generally, the application of this knowledge has been restricted to simple shapes like plates, cones and spherical bodies. However, flight reentry vehicles are in reality never simple. They typically are highly complex geometries flown at angle of attack so three-dimensional effects are very important, as are roughness effects due to surface features and/or ablation. This paper will review our present understanding of the physics of the transition process and look back at some of the recent flight test programs for their successes and failures. The goal of this paper is to develop rationale for new hypersonic boundary layer transition flight experiments. Motivations will be derived from both an inward look at what we believe constitutes a good flight test program as well as an outward review of the goals and objectives of some recent US based unclassified proposals and programs. As part of our recommendations, this paper will address the need for careful experimental work as per the guidelines enunciated years ago by the U.S. Transition Study Group. Following these guidelines is essential to obtaining reliable, usable data for allowing refinement of transition estimation techniques.

A Vision of Quantitative Imaging Technology for the Validation of Advanced Flight Technologies

“…Until the larger than desired uncertainties in prediction methods used to determine boundary layer transition onset times and surface temperatures from flow turbulence are reduced, unnecessarily large TPS margins will translate to reduced payload capability and degraded mission performance. In Reference 27 Berry et. al., concludes the only viable alternative for allowing fundamental breakthroughs in our understanding of the transition process at hypersonic flight conditions is flight-testing.…”

Crossflow Instability on a Wedge-Cone at Mach 3.5

“…5,6,7 The HyBoLT test article was a symmetric wedge flanked by tangent cones with different transition experiments on each face. On one face, termed "Side A" , a smooth wall crossflow experiment was designed to detect both stationary and traveling crossflow modes .…”