Researchers at the University of Virginia say a new effort to unlock the complex dynamics of electron kinetic behavior in the plasma beams of electric propulsion (EP) engines using supercomputer simulations could revolutionize space travel.
Led by Chen Cui, a new assistant professor at the University’s School of Engineering and Applied Science, the study was designed to uncover “fresh insights” into the EP engines to increase their overall efficiency and range. Achieving longer ranges and more efficient use of onboard fuel while also designing the engines to integrate seamlessly with the rest of the spacecraft will be critical to reducing the cost, complexity, and viability of missions into deep space.
“For missions that could last years, EP thrusters must operate smoothly and consistently over long periods of time,” Cui said in a statement. “In order to ensure the technology remains viable for long-term missions, we need to optimize EP integration with spacecraft systems.”
Plasma Beams and Electric Propulsion Engines
At present, all spacecraft are launched into space aboard chemical rockets. While most “flyable” spacecraft also rely on rocket power to maneuver in space, newer, more fuel-efficient, and longer-lasting technologies have slowly begun to replace chemical rockets.
Among the most common is a class of engines that use electricity gathered by solar panels and a small onboard propellant to generate a weak yet steady thrust stream. Known as electric propulsion, the most common design uses xenon gas and electricity to generate and accelerate a field of ions. The ejected ions form a plasma beam which pushes the spacecraft forward.
Due to the extremely small amount of gas needed to generate usable propulsion, these electric propulsion engines require significantly less propellant to travel further into space. Given the high cost of launching objects into space, reducing the launch weight is often among the most significant ways to reduce mission costs.
To improve the overall performance of these engines, Cui’s team focused on how electrons, which are microscopic, fast-moving quantum particles, behave within the plasma beams emitted during operation.
“These particles may be small, but their movement and energy play an important role in determining the macroscopic dynamics of the plume emitted from the electric propulsion thruster,” the professor explained.
Supercomputer Simulations Differ From Simple Models
In the published study outlining the research, Cui details the complex computer simulations used to examine the behavior of electrons within the EP engine’s plasma beams. Unlike typical simulations performed in a school computer lab, Cui’s models were run on supercomputers using a method called “Vlasov simulation.” According to the researcher, this computationally intensive method is advanced and “noise-free,” offering insights previously unavailable to EP researchers.
Surprisingly, the plasma beams in Cui’s simulations performed differently than simpler models. For example, the electrons moved differently at different temperatures and speeds. Cui said this movement caused “distinct patterns” within the beams.
“The electrons are a lot like marbles packed into a tube,” Cui said. “Inside the beam, the electrons are hot and move fast. Their temperature doesn’t change much if you go along the beam direction.”
However, Cui explained that if these ‘marbles’ originate from the middle of the tube, they begin to cool down. This cooling effect happens more in the direction perpendicular to the beam than parallel.
Cui’s team also found that the velocity of the electrons within the plasma beam showed a near Maxwellian, or bell curve, shape in the direction of the beam. The team describes this as a “top-hat profile in the transverse direction of the beam.
Finally, Cui’s team found that the movement of energy through the plasma beams, known as heat flux, primarily occurs along the beam’s direction. The researchers say these “unique dynamics” have “not been fully captured” in previous models.
The study “Vlasov Simulations of Electric Propulsion Beam” was published in Plasma Sources Science and Technology.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.