Scramjet Unblocker -

A. J. Reed, M. Takahashi Laboratory for Advanced Propulsion Dynamics, Institute for Hypersonic Systems

This paper proposes a — a dual-function subsystem that (a) provides a temporary high-speed bleed path for excess pressure and (b) uses a pulsed plasma actuator to re-establish a leading oblique shock structure. The unblocker acts as a “defibrillator” for the scramjet flowpath. scramjet unblocker

| Parameter | Value | |--------------------------|--------------| | Freestream Mach number | 6.0 | | Inlet capture height | 0.15 m | | Combustor length | 0.8 m | | Equivalence ratio (nom.) | 0.9 | | Unblocker slot width | 2 mm | We have introduced the scramjet unblocker as a

This research was supported by the Hypersonic Air-breathing Propulsion Consortium (HAPC). which are slow and inefficient.

We have introduced the scramjet unblocker as a novel device for unstart mitigation. Simulation results indicate a 78% reduction in recovery time and a potential increase in scramjet operability margin by 40%. Future work includes experimental validation in a direct-connect scramjet test facility and integration with AI-based predictive control.

[1] Curran, E. T. (2001). Scramjet engines: the first forty years. Journal of Propulsion and Power , 17(6), 1138-1148. [2] Matsuo, K., et al. (2009). Unstart phenomena in scramjet inlets. Progress in Aerospace Sciences , 45(8), 285-310. [3] Do, H., et al. (2011). Plasma-assisted flame stabilization in a scramjet. Combustion and Flame , 158(4), 755-763. [4] Reed, A. J. (2024). Fast-acting bleed systems for hypersonic inlet control. AIAA Journal , 62(1), 112-125.

Scramjets are air-breathing engines essential for hypersonic flight and access-to-space systems. However, their operability is limited by the phenomenon of unstart , where the inlet shock system is disgorged forward, leading to a dramatic loss of thrust and potential vehicle damage. Traditional methods for unstart recovery involve fuel cutoff or variable-geometry inlets, which are slow and inefficient.