Direct Fusion Propulsion with the PFRC

PSS and the Princeton Plasma Physics Lab (PPPL) are collaborating on a new fusion technology. Direct Fusion Drive is a revolutionary direct-drive, fusion-powered rocket engine concept. Compact and clean-burning, each 1-10 MW Direct Fusion Drive (DFD) engine would produce both power and thrust with high specific power (low mass). Producing propulsion directly in the fusion engine is highly efficient, shortening trip times and increasing capability for a wide variety of space missions: robotic missions to the outer planets, human missions to the moon or Mars, missions to near interstellar space. Here on Earth, portable fusion microreactors will enable modular power plants and integrate seamlessly with the future distributed power grid.

DFD is based on the Princeton Field-Reversed Configuration (PFRC) reactor, a technology developed by Dr. Sam Cohen of PPPL. The reactor employs a unique “odd-parity” RF heating method, producing a steady-state, closed-field configuration with a highly efficient current drive. The PFRC-2 experimental machine is currently in operation at PPPL, a plasma pulse is shown below. Read more on the PFRC technical papers page!


PFRC-2 has been supported by the Department of Energy, ARPA-E, NASA Innovative Advanced Concepts and two NASA STTRs. Our NIAC context mission was a Pluto orbiter and lander that are delivered in just 4 years, and can send back the equivalent of HD video!

We have analyzed DFD for many missions and applications:

  • Human Mars orbital mission
  • Deploying the James Webb Telescope to a Lagrange point
  • Asteroid deflection
  • Jupiter Icy Moons Mission
  • Pluto orbiter and lander
  • Alpha Centauri
  • 600+ AU gravity lens telescope
  • Mobile and modular terrestrial power

In all cases, DFD reduces trip times and increases payload capability and science return! For the latest updates on our research, check out our DFD blog posts.

Publications and News:

PSS has licensed five patents from PPPL for commercializing the PFRC:

  • “System and method for small, clean, steady-state fusion reactors”, S. Cohen and M. Chu Cheong, US 11,322,265 issued 5/3/2022
  • “System and method for reducing heat loss from FRC bulk plasma,” US 11,164,681 issued
  • “Fueling Method for Small, Steady-State, Aneutronic FRC Fusion Reactors,” US 10,811,159  issued 10/20/2020
  • “Method To Produce High Specific Impulse and Moderate Thrust From a Fusion-Powered Rocket Engine,” S. Cohen, G. Pajer, M. Paluszek, Y. Razin, US Patent Number 9,822,769 issued 11/11/2017
  • “Method To Reduce Neutron Production in Small Clean Fusion Reactors,” S. Cohen, US Patent Number 9,767,925 issued 9/19/2017

In addition we have patents specific to PFRC operation in space:

  • “In Space Startup Method for Nuclear Fusion Rocket Engines,” Paluszek, M., Ham, E., Cohen, S., and Razin, Y. US Patent 10,811,143 issued 10/20/2020

Princeton Satellite Systems has a doing-business-as name for terrestrial fusion applications: Princeton Fusion Systems. Visit our sister site for more information on PFRC!