On the road to creating an electrodeless spacecraft propulsion engine
Physical picture of the applied magnetic field lines (blue lines) and the magnetic field lines (red lines) modified by the plasma flow, i.e., sum of the applied and plasma-induced magnetic fields. The plasma decreases the axial field component at the upstream side of the magnetic nozzle and increases it at the downstream side of the nozzle as described by the insets, where the transition between these two states are identified as shown by the upper left inset.
Credit: Kazunori Takahashi
The universe is made up of plasma, which is easily influenced by magnetic fields and forces, leading to complex behavior. Plasmas are found throughout the solar system in places such as the planetary magnetosphere, solar wind and in the tails of comets.
Magnetic fields stretched by plasma flows result in an increase in the field component along the plasma flow. These fields are frequently observed in space. By contrast, scientists in terrestrial laboratories often see the magnetic fields decreased by plasma due to its diamagnetism. This implies that the plasma can generate a magnetic field in the opposite direction to the one applied so the field lines diverge.
Researchers from Tohoku University have been trying to find out how the plasma flow is influenced by its environment via laboratory experiments, and have made headway on research toward an electrodeless plasma thruster to propel spacecraft.
There are many methods of spacecraft propulsion, and while they all have their pros and cons, electric propulsion is now mature and widely used. Electrically powered plasma thrusters can deliver large thrust density without the need to expose electrodes to plasma, which cuts down on damage from erosion over time.
While nearly all spacecraft use chemical rockets for launch, once the hardware is in space, propulsion is needed to manoeuvre the craft for orbit maintenance, supply missions and space exploration. Here, electric propulsion, with its higher exhaust speed, is preferred, as it typically uses less propellant than chemical rockets. Because it's difficult to make general repairs on spacecraft once they have left Earth, the reliability of their internal components is essential for long-term missions.
Some new concepts for plasma thrusters involve an expanding magnetic field called magnetic nozzle (MN), where the plasma is spontaneously accelerated to propel a spacecraft when exhausted into space.
Read more ~ phys.org/news/2017-06-road-electrodeless-spacecraft-propulsion.html#jCp
