High Efficiency RF Heating for Small Nuclear Fusion Rocket Engines

High power nuclear fusion propulsion systems will require high efficiency radio-frequency heating systems in the MHz range for plasma heating. This proposal is for a novel scalable solid state Class E amplifier using Silicon Carbide switching transistors for plasma heating. This system is potentially 100% efficient compared to 40% for linear amplifiers and can be scaled to any desired size by adding additional segments in parallel. The system includes a novel closed loop feedback control system at the antenna and from the plasma. This eliminates the need for lossy transformers and other non-ideal components. The RF amplifier will be prototyped in Phase I in preparation for a plasma heating experiment in Phase II.

This technology is applicable to all radio-frequency applications for NASA. This includes microwave-heated thrusters, such as Ad Astra's VASIMR. VASIMR is a revolutionary new in-space propulsion system that heats a plasma with two types of microwave radiation. It can provide high thrust and high specific impulse in the 100 kW+ range. The technology is also applicable to scientific experiments using radio-frequency technology. Current RF applications use tubes or Solid State Power Amplifier (SSPAs). These are typically linear amplifiers and only 40% efficient. Communication systems up to S-band will also be applications of this technology Laboratory research and aerospace manufacturing using radio-frequency radiation done by NASA will also benefit. It will reduce costs of RF equipment and reduce power consumption.

This technology is applicable to a wide variety of commercial applications. These include: HF band radars for coastal and over horizon systems (OTH) Medium (MF) and High Frequency (HF) Radio (ITU Bands 5 and 6) Communications channels up to S-band Materials processing Plasma heating for terrestrial fusion reactors RF heating for manufacturing Current RF systems use tubes, such as Traveling Wave Tube Amplifiers (TWTAs) and Solid State Power Amplifiers (SSPAs). These are less efficient than the switching amplifiers in this proposal.

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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