Thermionics for Hypersonics

Spark Thermionics proposes to develop thermionic devices that integrate directly into hypersonic vehicles. Thermionic energy conversion has the potential to leapfrog competing technologies but has largely been neglected for decades. Today, we have demonstrated best-in-class thermionic performance using novel materials and manufacturing techniques, as well as fully encapsulatedp rototypes meeting solicitation targets, including power density (1-10 W/cm2). Using these devices as a baseline, we propose to demonstrate a new device that is compatible with harvesting heat directly from high temperature surfaces in the vehicle, relying on existing thermal pathways within the vehicle to simultaneously generate electricity while thereby displacing and reducing the vehicle thermal load. Our Phase I effort resulted in a design that is a fraction of the height and weight of our prior devices and that is compatible with two compelling space charge mitigation techniques, as well as proof of principle experiments of these techniques. Once we demonstrate devices as part of a Phase II effort, we believe these devices can increase the Mach number in any vehicle and we believe will be enabling for long-duration and reusable hypersonic vehicles. If successful, our solution will add virtually no extra weight or volume vs the existing skin / liner, becoming the “APU” for all next-generation long-duration hypersonic vehicles.