Physicist Fatima Ebrahimi in front of an artist’s conception of a fusion rocket.
Credit: Elle Starkman, PPPL Office of Communications, and ITER

The prospect of propelling humans at greater speeds to Mars and beyond is an upshot from a new concept for a rocket thruster, one that exploits the mechanism behind solar flares.

This new notion would accelerate the particles using “magnetic reconnection,” a process found throughout the universe, including the surface of the sun. It’s when magnetic field lines converge, suddenly separate, and then join together again, producing lots of energy. Reconnection also occurs inside doughnut-shaped fusion devices known as tokamaks.

Long-distance travel

“I’ve been cooking this concept for a while,” said physicist Fatima Ebrahimi, the concept’s inventor at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL).

The Red Planet as seen by Europe’s Mars Express.
Credit: ESA/D. O’Donnell – CC BY-SA IGO

That faster velocity at the beginning of a spacecraft’s journey could bring the outer planets within reach of astronauts, Ebrahimi said in a PPPL statement.

“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,” Ebrahimi said. “But if we make thrusters based on magnetic reconnection, then we could conceivably complete long-distance missions in a shorter period of time.”

Turn a knob…fine-tune velocity

According to Ebrahimi, there are three main differences between her thruster concept and other devices.

The first is that changing the strength of the magnetic fields can increase or decrease the amount of thrust. “By using more electromagnets and more magnetic fields, you can in effect turn a knob to fine-tune the velocity,” Ebrahimi said.

Image of sun shows magnetic reconnection.
Credit: NASA’s Solar Dynamics Observatory, or SDO. NASA’s Living With a Star Program

Second, the new thruster produces movement by ejecting both plasma particles and magnetic bubbles known as plasmoids. The plasmoids add power to the propulsion and no other thruster concept incorporates them.

Third, unlike current thruster concepts that rely on electric fields, the magnetic fields in Ebrahimi’s concept allow the plasma inside the thruster to consist of either heavy or light atoms. This flexibility enables scientists to tailor the amount of thrust for a particular mission.

“While other thrusters require heavy gas, made of atoms like xenon, in this concept you can use any type of gas you want,” Ebrahimi said. Scientists might prefer light gas in some cases because the smaller atoms can get moving more quickly.

Next step

Support for this research came from the DOE Office of Science (Fusion Energy Sciences) and Laboratory Directed Research and Development (LDRD) funds made available through the Office of Science.

Chalkboard physics. Fatima Ebrahimi looks to speedy space travel.
Credit: Fatima Ebrahimi

“This work was inspired by past fusion work and this is the first time that plasmoids and reconnection have been proposed for space propulsion,” Ebrahimi said. “The next step is building a prototype!”

 

 

Fatima Ebrahimi’s idea — An Alfvenic reconnecting plasmoid thruster — can be found in the Journal of Plasma Physics here:

https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/abs/an-alfvenic-reconnecting-plasmoid-thruster/F296E45CC504E8FF2586EA79117E2514

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