The unique design of the plasma thruster could enable spacecraft to travel to distant planets much faster than they can now.
Dr Fatima Ebrahimi has invented a new fusion rocket thruster concept which could power humans to Mars and beyond.
The physicist who works for the US Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) designed the rocket which will use magnetic fields to shoot plasma particles – electrically charged gas – into the vacuum of space.
According to Newton’s second and third laws of motion, the conservation of momentum would mean the rocket was propelled forwards – and at speeds 10 times faster than comparable devices.
While current space-proven plasma propulsion engines use electric fields to propel the particles, the new rocket design would accelerate them using magnetic reconnection.
This process is found throughout the universe but is most observable to humanity on the surface of the sun. When magnetic field lines converge there, before separating and then reconnect again, they produce an enormous amount of energy.
Similar energy is produced inside torus-shaped machines known as tokamaks, a magnetic confinement device which is also a leading candidate for a practical nuclear fusion reactor.
“I’ve been cooking this concept for a while,” said PPPL’s principal research physicist Dr Fatima Ebrahimi, whose paper detailing the invention has been published in the Journal of Plasma Physics.
“I had the idea in 2017 while sitting on a deck and thinking about the similarities between a car’s exhaust and the high-velocity exhaust particles created by PPPL’s National Spherical Torus Experiment (NSTX),” she said.
The NSTX is the forerunner of the laboratory’s present flagship fusion facility, which is being investigated with funding by the US Department of Energy.
“During its operation, this tokamak produces magnetic bubbles called plasmoids that move at around 20 kilometres per second, which seemed to me a lot like thrust,” Dr Ebrahimi added.
Nuclear fusion is the power that drives the sun and stars. It combines light elements in the form of plasma – the hot, charged state of matter composed of free electrons and atomic nuclei that represents 99% of the visible universe – to generate massive amounts of energy.
If a reactor functioning on the same principles could be recreated on Earth, it would provide a “virtually inexhaustible supply of power to generate electricity” according to the PPPl.
Dr Ebrahimi’s new concept performs much better than existing plasma thrusters in computer simulations – generating exhaust with velocities of hundreds of kilometres per second, 10 times faster than those of other thrusters.
That faster velocity at the beginning of a spacecraft’s journey could bring the outer planets within reach of astronauts, the physicist said.
“Long-distance travel takes months or years because the specific impulse of chemical rocket engines is very low, so the craft takes a while to get up to speed,” she said.
“But if we make thrusters based on magnetic reconnection, then we could conceivably complete long-distance missions in a shorter period of time.”
She stressed that her thruster concept stems directly from her research into fusion energy. “This work was inspired by past fusion work and this is the first time that plasmoids and reconnection have been proposed for space propulsion,” Dr Ebrahimi said. “The next step is building a prototype!”