Test Program for a Dual-mode Scramjet

Abstract

Since flow at hypersonic Mach numbers (M≥5) behaves very differently from flow at subsonic or supersonic Mach numbers, the testing of hypersonic engines involves challenges not encountered in engine testing for flight in other regimes. For hypersonic Mach numbers, thermal, chemical, radiative, and ablative effects become important.Energy and heat transfer considerations make continuous-run, full scale testing at hypersonic Mach numbers difficult or impossible. While facilities have been devised specifically to study certain aspects of hypersonic flight, no single facility has the ability to simulate all the flow conditions that a hypersonic vehicle or engine may encounter.Flight can be considered the ultimate test of a hypersonic vehicle or engine because no facility effects are present. It is often the case, however, that budgetary, thermal, structural, or other logistical limitations restrict the range of diagnostics available for flight vehicle testing. Flight programs also incur significant risk that is generally not present or is significantly reduced for ground testing programs. If an unguided rocket is used to minimize cost, the likelihood that the payload will achieve the desired test conditions decreases. If a reactive control system is utilized to increase the likelihood that the payload will achieve the desired test conditions, both complexity and cost increase significantly. As such, flight programs are nearly always augmented with significant ground testing to reduce risk and confirm engine operability limits. Often a range of wind tunnels is used in order to resolve the inherent deficiencies of any one type of ground test facility. Two common shortcomings of hypersonic test facilities are the short test time associated with shock-heated facilities and the contaminated or vitiated test gas associated with combustion-heated facilities.