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March 27, 2012

Nuclear Propulsion Through Direct Conversion of Fusion Energy

Nuclear Propulsion Through Direct Conversion of Fusion Energy by John Slough (of Helion Energy and MSNW LLC)


The future of manned space exploration and development of space depends critically on the creation of a vastly more efficient propulsion architecture for in-space transportation. Nuclear-powered rockets can provide the large energy density gain required. A small scale, low cost path to fusion-based propulsion is to be investigated. It is accomplished by employing the propellant to compress and heat a magnetized plasma to fusion conditions, and thereby channel the fusion energy released into heating only the propellant. Passage of the hot propellant through a magnetic nozzle rapidly converts this thermal energy into both directed (propulsive) energy and electrical energy

MSNW LLC site on space propulsion


The Electrodeless Lorentz Force (ELF) thruster family has demonstrated operational power levels ranging from 100 Watts to 10 MW. The ELF design is the first steady-state pulsed inductive thruster, and has run continuously for more than 1E8 plasmoids. This design has operated using traditional Electric Propulsion (EP) propellants such as Xenon as well as complex molecular propellants including monopropellants and in-situ resources. MSNW is currently teaming with NASA and the DOD.

We have previously covered John Sloughs work on ElectroMagnetic Plasmoid Thruster (EMPT)

The EMPT thruster, funded by NASA, is a 1 kW-class RMF thruster, operates on the same physics principles as the ELF thruster. This device, less than 4 inches in diameter, has proven that pulsed inductive technolgoies can be succesfully miniaturized. Indeed, this thruster has demonstrated operation from 0.5 to 5 Joules, as well as the first pulsed inductive steady state operation. The EMPT has demonstrated greater than 1E8 continuous plasma discharges.




The Electromagnetic Plasmoid Thruster (EMPT) is a revolutionary electric propulsion thruster and power processing (PPU) system that will allow a dramatic decrease in system mass and increase in thrust efficiency over traditional 500-1000 W propulsion systems. The high specific power (over 700 W/kg) and high efficiency of EMPT will enable a wide range of deep space missions such as Neptune, Pluto and Oort Cloud orbital insertion. Additionally, a solar electric EMPT system would dramatically increase the capability and reduce the travel time of an asteroid or Martian moon sample and return mission due to the variable-power, low-mass propulsion system. The EMPT employs a Rotating Magnetic Field (RMF) to produce large plasma currents inside a conical thruster creating a plasmoid that is magnetically isolated from the thruster walls. The intensified gradient magnetic field from the plasmoid together with the large plasma currents result in an enormous body force that expels the plasmoid at high velocity. The EMPT is a pulsed device, nominally operating at 1 kWe with 1 Joule discharges at 1 kHz. Presented is a full description of the relevant plasma physics as well as the thruster and PPU design. All physical principals behind the EMPT have been demonstrated in the laboratory at the relevant scales. Additionally, the AFOSR-funded ELF thruster has demonstrated RMF formation and acceleration in a thruster application at higher energy levels. The focus of the proposal is the experimental validation of an integrated thruster and PPU operating in a multi-pulse mode. The EMPT will be characterized over a range of parameters: input power from 200-1000 Watts, 50-80 mN thrust, and 1500-4000 seconds specific impulse. The integrated thruster and PPU to be built and tested will have a total system mass of less than 1.5 kg. Successful completion of Phase I will mature the technology from a TRL level 3 to 5. Phase II will be a fully integrated, steady-state demonstration with life test.


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