Apart from conventional propulsion, plasma propulsion system in spacecraft is a very futuristic concept. This concept is very efficient to control a spacecraft in different long range space mission. So, researchers from the different side around the globe are already working for this advanced propulsion project.
Previously, this concept faced some overweight and complexity issues due to a device called neutralizer. That's why a research team found a new concept called Neptune to design a plasma propulsion system without neutralizer.
Plasma is the fourth state of the material just after Solid, Liquid and Gas. Plasma propulsion is a type of electric propulsion that generates thrust from quasi-neutral plasma. In this system, electric power ionized the propellant gas and transform it into plasma. Therefore, thrust is generated by an ion thruster engine that extracting the ion current from the plasma source.
However, the stream of charged ions or ion current is accelerated by using grids or anodes which create an exhaust beam to generate thrust and propel the spacecraft. Basically, plasma propulsion system consumes much less propellant than chemical propulsion because they have a higher exhaust speed than chemical propellant rockets.
According to American Institute of Physics (AIP), the gridded ion thruster which is only creating thrust from accelerated positively charged particles rather than the negative ion. But a spacecraft must need to remain charge-neutral, that's why a device called neutralizer used in plasma propulsion system. Principally, neutralizer injects electrons to balance the positive ion charge in the exhaust beam.
Though the basic problem of neutralizer device is, it requires an additional power from the spacecraft which increases the size and weight of the propulsion system. A research team from the University of York and école Polytechnique are finding a way to eliminate neutralizer altogether. Regarding the study, they published a paper in the journal Physics of Plasmas.
According to this Neptune concept, there are no longer needed for neutralizer in plasma propulsion system. The theory explained that, due to comparable numbers of positively and negatively charged particles presence in the exhaust beam which already neutralizes the spacecraft. Now researchers are working on further development of the Neptune concept to find the interaction between plasma and the accelerating grid which generates the neutral beam.
Additionally, they also studied the dynamics of negatively charged electrons in the exhaust beam of the thruster. From which, they try to understand the behavior of these negative particles which will play a key role in beam neutralization.
