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Center Innovation Fund: JSC CIF

Solid-State Thermionic Power for Megawatt Propulsion, Planetary Surface and Commercial Power

Completed Technology Project

Project Introduction

Thermionic (TI) power conversion is a promising technology first investigated for power conversion in the 1960’s, and of renewed interest due to modern advances in nanotechnology, MEMS, materials and manufacturing.  Benefits include high conversion efficiency (20%), static operation with no moving parts and the potential for high reliability, greatly reduced plant complexity, and the potential for reduced development costs.  Thermionic emission, credited to Edison in 1880, forms the basis of vacuum tubes and much of 20th century electronics. Heat can be converted into electricity when electrons emitted from a hot surface are collected across a small gap. For example, two “small” (6 kWe) Thermionic Space Reactors were flown by the USSR in 1987-88 for ocean radar reconnaissance.  Higher powered Nuclear-Thermionic power systems driving Electric Propulsion (Q-thruster, VASIMR, etc.) may offer the breakthrough necessary for human Mars missions of < 1 yr. round trip.  Power generation on Earth could benefit from simpler, more economical nuclear plants, and "topping" of more fuel and emission efficient fossil-fuel plants.

Thermionic (TI) power conversion is a promising technology first investigated for power conversion in the 1960’s, and of renewed interest due to modern advances in nanotechnology, MEMS, materials and manufacturing. Benefits include high conversion efficiency (20%), static operation with no moving parts and the potential for high reliability, greatly reduced plant complexity, and the potential for low Design, Development. Test and Evaluation (DDT&E) costs. Thermionic emission, credited to Edison in 1880, forms the basis of vacuum tubes and much of 20th century electronics. Heat can be converted into electricity when electrons emitted from a hot surface are collected across a small gap. For example, two “small” (6 kWe) Thermionic Space Reactors were flown by the USSR in 1987-88 for ocean radar reconnaissance. Higher powered Nuclear-Thermionic power systems driving Electric Propulsion (Q-thruster, VASIMR, etc.) may offer the breakthrough necessary for human Mars missions of < 1 yr round trip.

This project targets one of the most critical barriers to human deep space exploration – the means to efficiently power and rapidly propel human missions to Mars and beyond.  The project will explore the implementation of a high efficiency “Solid-State” Thermionic-based nuclear fission power systems to serve Electric Propulsion systems such as Q-thrusters, VASIMR, Hall, or other approaches.  A Solid-State approach centered around advanced Thermionic power converters would combine the high efficiency of traditional dynamic power conversion (Rankine, Brayton, Stirling) with the simplicity of a static converter with no moving parts.  The resulting system could enable Human Mars missions of < 1 year round trip by affording a system of megawatt power, low specific mass (<10 kg/kWe), greatly reduced plant complexity, and associated savings in development cost.   This project provides the initial foundation and confidence for high efficiency solid-state power converters, and early definition of enabled human exploration systems and missions (ex. Megawatt Electric Propulsion, Moon/Mars Surface Power).  Subsequent converter development will improve readiness and lifetime, leading to “flight ready” articles.  An intermediate NASA infusion step would demonstrate kilowatt-class nuclear power systems applicable to Moon or Mars surface.  Human vehicle system development would then integrate these converters with DOE nuclear reactor technology, NASA balance of plant (ex. radiators, PMAD), and electric propulsion (ex. Q-thrusters, VASIMR, Hall thrusters) to develop an “ultimate” NASA application of a Human Mars Megawatt-class Nuclear Electric Propulsion vehicle and mission.  Terrestrial applications would be informed/infused resulting in high efficiency power systems with greatly reduced complexity and cost.                       

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