Ion Propulsion is one of the least known form to travel space unless you've read science fiction books. So as a space enthusiast that's why I have decided to write about it, so here is the brief.
Ion Propulsion have high specific impulse (Isp) requiring it to use significantly less fuel during space flight compared to its chemical counterpart. Not only it uses less fuel but it is significantly much more efficient to its chemical rocket counterpart. Ion thrusters are used to keep communication satellites in place, maintaining Low Earth Orbits (LEO), Deep Space missions, refuelling missions and numerous other varieties of missions. Ion Propulsion may seem like a wonder engine but it has several cons not allowing it to be used everywhere.
The Process first begins with injection of the propellant (neutral) from the downstream end of the thruster to maximize ionization, the propellant (neutral) is bombarded with electrons. These electrons are generated by a hollow cathode, called the discharge cathode. The electrons flow out the discharge cathode are attracted to the discharge chamber walls, which are charged by the power supply of the thruster. When a high energy electron bombards the propellant (neutral) a pair of electrons will be knocked off the propellant, making it a positively charged ion. Magnets placed along the discharge wall redirect electrons into the discharge chamber. (1&3)
“In a gridded ion thruster, ions are accelerated by electrostatic forces. The electric fields used for this acceleration are generated by two electrodes, called ion optics or grids, at the downstream end of the thruster. The greater the voltage difference between the two grids, the faster the positive ions move toward the negative charge. Each grid has thousands of coaxial apertures (or tiny holes). The two grids are spaced close together (but not touching), and the apertures are exactly aligned with each other. Each set of apertures (opposite holes) acts like a lens to electrically focus ions through the optics.” (3)
“NASA's ion thrusters use a two-electrode system, where the upstream electrode (called the screen grid) is charged highly positive, and the downstream electrode (called the accelerator grid) is charged highly negative. Since the ions are generated in a region that is highly positive and the accelerator grid's potential is negative, the ions are attracted toward the accelerator grid and are focused out of the discharge chamber through the apertures, creating thousands of ion jets. The stream of all the ion jets together is called the ion beam. The thrust is the force that exists between the upstream ions and the accelerator grid. The exhaust velocity of the ions in the beam is based on the voltage applied to the optics. Whereas a chemical rocket's top speed is limited by the heat-producing capability of the rocket nozzle, the ion thruster's top speed is limited by the voltage that is applied to the ion optics, which is theoretically unlimited.“ (3)
I’ve taken these two extracts from NASA as I could’ve not explained better.
A second hollow cathode is called the neutralizer, it is used to push out needed electrons to neutralize the exhausted propellant. (1&3)
