Neptune: Neutralizer-free plasma propulsion

May 23, 2017, American Institute of Physics
An image of the Neptune thruster (right) with plasma expanding into a space simulation chamber. Credit: Dmytro Rafalskyi

Plasma propulsion is an important and efficient technology used to control spacecraft for Earth observation, communications and fundamental exploration of outer space.

Plasma systems use electric power to ionize propellant gas and transform it into the fourth state of matter, known as . Electrically charged ions and electrons are accelerated in an exhaust beam to generate thrust and propel the spacecraft.

The most established electric propulsion concepts, for example gridded-ion thrusters, accelerate and emit a larger number of positively charged particles than those with negative charge. To enable the spacecraft to remain charge-neutral, a "neutralizer" is used to inject electrons to exactly balance the positive ion charge in the exhaust beam. However, the neutralizer requires additional power from the spacecraft and increases the size and weight of the propulsion system.

A team from the University of York and École Polytechnique is investigating how the neutralizer can be removed altogether. The researchers report their findings this week in the journal Physics of Plasmas.

In 2014, Dmytro Rafalskyi and Ane Aanesland from the Laboratory of Plasma Physics, École Polytechnique, France demonstrated a new electric propulsion concept. The concept, called Neptune, leverages the technological heritage of gridded-ion thrusters. However, as comparable numbers of positively and negatively charged particles are present in the exhaust beam the neutralizer is no longer needed.

To further develop the Neptune concept towards spaceflight, the researchers were interested in understanding how the plasma interacts with the acceleration system so that a charge-neutral beam is generated. They teamed up with James Dedrick and Andrew Gibson from the York Plasma Institute, University of York, U.K. to study how plasma behavior varies in relation to spatial location, time and particle energy.

"The direct observation of how energetic plasma species behave on nanosecond timescales in the Neptune beam will help us to better control the processes that underpin neutralization," Dedrick said.

As part of their investigation, the researchers studied the dynamics of negatively charged energetic electrons in the exhaust beam of the thruster and their behavior was observed to play a key role in neutralization.

"We believe that this arises from a complex interaction between the plasma and acceleration grids, which is highly dependent upon the particle dynamics nearby to the grid surface," Dedrick said.

Explore further: Where does laser energy go after being fired into plasma?

More information: James Dedrick et al, Transient propagation dynamics of flowing plasmas accelerated by radio-frequency electric fields, Physics of Plasmas (2017). DOI: 10.1063/1.4983059

Related Stories

FLASHForward accelerates first electron bunches

February 28, 2017

The plasma accelerator project FLASHForward achieved an important milestone in January: for the first time, the facility's high-power laser accelerated electron bunches in a plasma cell. Later in the operational phase, the ...

Scientist uncovers physics behind plasma-etching process

January 27, 2017

Physicist Igor Kaganovich at the Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) and collaborators have uncovered some of the physics that make possible the etching of silicon computer chips, which ...

Recommended for you

Information engine operates with nearly perfect efficiency

January 19, 2018

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine's efficiency ...

Team takes a deep look at memristors

January 19, 2018

In the race to build a computer that mimics the massive computational power of the human brain, researchers are increasingly turning to memristors, which can vary their electrical resistance based on the memory of past activity. ...

Artificial agent designs quantum experiments

January 19, 2018

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.