Physical Sciences Inc. and Purdue University propose to develop a novel approach to scavenging heat from high intensity thermal environments encountered during space missions and converting this thermal power to electrical power at high efficiency. Examples include extremely hot heat shields during vehicle entry into planetary atmospheres (Mars/Venus probes) and during high speed ascent through planetary atmospheres (Sample return from Mars/Venus), hot claddings of radioisotope thermoelectric generators used for powering outer planetary spacecraft and multi-decade planetary bases (Mars/Venus/Lunar), as well as combustors/nozzles of space and launch propulsion systems, specifically, nuclear propulsion systems of renewed interest. The technology is also applicable commercially to high temperature sources encountered in terrestrial systems, such as portable electrical power converters from machinery (engines, stoves) used by soldiers and civilians in outdoor environments, In this STTR we will develop an integrated metal hydride (MH) system and spectrally-tuned thermophotovoltaic power converter (PC) system that can extract heat during periods of high thermal intensity and convert it to electricity at greater than 25 percent efficiency. The MH system provides the high temperature reservoir needed for PC operation.
In Phase I, for the PC system, we demonstrated feasibility of fabricating a critical emitter component in larger areas (5 cm x 5 cm), and for the metal hydride (MH) system, we experimentally characterized the MH decomposition reactions. In Phase II, we will produce and functionally characterize an integrated engineering prototype of the MH-PC heat scavenging electrical power generator system, fully tested in the laboratory and in simulated thermal-vacuum environments, together with an analytical model of the functional system. We will identify candidate facilities (e.g., NASA/Stennis) for field testing of the system in Phase III.
The proposed heat scavenging electrical power converter will find applications in NASA exploration missions to planets with atmospheres, such as Venus, Mars, and likely others. Examples include small, power-limited probes released from an orbiter to enter the atmosphere, gather data during descent, land on the surface, and possibly continue data gathering operations for some time. The proposed technology would generate electrical power during the hot atmospheric descent as well as surface operations using other high temperature sources. Another example would be a planetary sample return mission, where a small probe ascends a high speed through the atmosphere, with the electrical power generated from scavenging heat from the vehicle’s heat shield. Planetary missions to Venus and Mars are presently a part of the NASA roadmaps. Other applications include generation of electricity from hot cladding of radioisotopes used in thermoelectric generators on years-long planetary missions and proposed to be used on decades-long planetary bases. A new NASA application would be for remotely powering and monitoring wireless sensors/control systems during nuclear propulsion engines tests, where high temperature surfaces are readily available for conversion to electrical power. Additional NASA applications include remote, wireless powering and control of sensors monitoring cryogenic propellant tanks, where the high temperature source is provided by combustion of LH2-LOX boil-off.
The proposed compact power generator devices have several aerospace and commercial applications. For example, power generator can be adapted for long range hypersonic vehicles reentering the earth’s atmosphere. The customers for this application are the U.S. Air Force and the Navy. Compact, portable power generators are particularly suited for power generation on a small scale, such as for individual soldiers and campers/backpackers. In these applications, the hot source would be a burner consuming hydrocarbon fuel such as a portable propane cylinder, a camping stove, or an engine. The government customers for this application include the U.S. Army, the U.S. Special Operations Command, and the Marines. Manufacturers of camping equipment would form a very large commercial customer base for this technology. The regenerative hydrides capability of our technology will have wide commercial applications in hydrogen storage systems for a variety of uses in the future hydrogen economy, including automobiles. Customers include various DoD agencies as well as a range of commercial manufacturers.