• Post category:Rocket Science
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Today we will discuss about Ion Thrusters. How it works, different types of ion thrusters, advantages, and applications.

NASA's 2.3 kW NSTAR ion thruster for the Deep Space 1 spacecraft during a hot fire test at the Jet Propulsion Laboratory
NASA’s 2.3 kW NSTAR ion thruster for the Deep Space 1 spacecraft during a hot fire test at the Jet Propulsion Laboratory

The working of Ion Thrusters

Simple layman explanation: Shoot Electrons over the atoms of an inert gas and knock off more electrons from it, there by creating positive ions. Then, accelerate those ions out.

Finally, again shoot electrons over the exiting ions to neutralize it.

Ion thrusters working
Ion thrusters working

Ion thrusters are classified in 2 types on method used for accelerating the ions—

  • Electrostatic ion thrusters use the Coulomb force.
  • Electromagnetic ion thrusters use the Lorentz force.

The method of accelerating the ions varies, but all designs take advantage of the charge-to-mass ratio of the ions. This ratio means that relatively small potential differences can create high exhaust velocities. This reduces the amount of reaction mass or propellant required, but increases the amount of specific power required compared to chemical rockets. Ion thrusters are therefore able to achieve high specific impulses. The drawback of the low thrust is low acceleration because the mass of the electric power unit directly correlates with the amount of power. This low thrust makes ion thrusters unsuited for launching spacecraft into orbit, but effective for in-space propulsion.

Applications

Ion thrusters, in operational use, have an input power need of 1–7 kW, exhaust velocity 20–50 km/s, thrust 25–250 millinewtons, and efficiency 65–80%though experimental versions have achieved 100 kilowatts, 5 newtons.

They have many in-space propulsion applications. The best applications make use of the long mission interval when significant thrust is not needed. Examples of this include orbit transfers, attitude adjustments, drag compensation for low Earth orbits, fine adjustments for scientific missions and cargo transport between propellant depots, e.g., for chemical fuels. Ion thrusters can also be used for interplanetary and deep-space missions where acceleration rates are not crucial. Continuous thrust over a long interval can reach high velocities while consuming far less fuel than traditional chemical rockets.

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