In theory, how much thrust could an ion thruster generate?

Question

Ion thrusters require a lot of electrical power, while their thrust is incredibly low. However, the more power is available, the more thrust can be achieved. What would be the theoretical limit to that? Is there a limit to the thrust force that a given ion thruster can produce, or an upper thrust limit without restricting to a given thruster?

Also, what are the practical problems an ion thruster would face at high energy levels? Is there a formula that would allow me to calculate the thrust of any particular ion thruster based on its energy? Thanks in advance!

Answer 1

1. Your formula is Power = 0.5 * Thrust * Exhaust velocity/efficiency.

This equation gives to the beam power for all forms of propellant based propulsion. There could be several terms for efficiency, e.g. describing losses from the engine to the beam, electrical power conversion within the engine, power conversion from an external power source (e.g. the sun) to the engine. Its similar in concept to Kinetic Energy = 0.5 mass V^2 except that power is the time derivative of energy.

2. The main practical problem so far, after the mass of the power generation (solar panels), is the mass of the thruster itself. Ion thrusters have charateristically low thrust to weight ratios.

Beyond this rather hand-wavy claim the scaling-up is going to depend upon the type of ion thruster and you will need to do some digging. To some this just means the kaufman type or the RF type though some people consider these just to be gridded ion engines where the hall effect thruster is another, non-gridded, type.

Further reading:

Operational satellites with Electric Propulsion (from 2012)

What is the performance of ion thrusters in actual deployed spacecraft?