Optimization of an external compression fixed geometry ramp scramjet intake for performance across a wider range of Mach numbers

Abstract

Scramjets are a type of air breathing propulsion that operate at speeds above Mach 5, and provide opportunities for cheaper and more efficient transport to space. Traditional LH2/LOX rocket engines have a specific impulse (Isp, a measure of efficiency) of around 450s, whereas scramjets can have an Isp of around 3500s. However, scramjets face a multitude of issues, one of which being that fixed geometry scramjets are a point design optimized for a single speed, resulting in performance losses when not at the optimum speed. This paper is intended to optimize the performance across a wider range of Mach numbers in fixed geometry ramp intakes. The optimum number of ramps and the angles of them will be optimized to increase pressure recovery and prevent shock impingement. Typically, a greater number of shocks with oblique shocks at a less extreme angle results in better such performance. Research on such improvement has been done, but have focused on different inlet designs. This research instead focuses on fixed geometry external compression ramp intakes based on Oswatitsch and Kantrowitz criteria, and optimizes the inlet for speeds from Mach 6 to 8.