Pulsed inductive thruster

A pulsed inductive thruster (PIT) is a form of ion thruster, used in spacecraft propulsion. It is a plasma propulsion engine using perpendicular electric and magnetic fields to accelerate a propellant with no electrode. A nozzle releases a puff of gas which spreads across a flat spiraling induction coil of wire about 1 meter across. A bank of capacitors releases a pulse of high voltage electric current of tens of kilovolts lasting 10 microseconds into the coil, generating a radial magnetic field. This induces a circular electrical field in the gas, ionizing it and causing charged particles (free electrons and ions) to revolve in the opposite direction as the original pulse of current. Because the motion of this induced current flow is perpendicular to the magnetic field, the plasma is accelerated out into space by the Lorentz force at a high exhaust velocity (10 to 100 km/s). Unlike an electrostatic ion thruster which uses an electric field to accelerate only one species (positive ions), a PIT uses the Lorentz body force acting upon all charged particles within a quasi-neutral plasma. Unlike most other ion and plasma thrusters, it also requires no electrodes (which are susceptible to erosion) and its power can be scaled up simply by increasing the number of pulses per second. A 1-megawatt system would pulse 200 times per second. Pulsed inductive thrusters can maintain constant specific impulse and thrust efficiency over a wide range of input power levels by adjusting the pulse rate to maintain a constant discharge energy per pulse. It has demonstrated efficiency greater than 50%. Pulsed inductive thrusters can use a wide range of gases as a propellant, such as water, hydrazine, ammonia, argon, or xenon, among many others. Due to this ability, it has been suggested to use PITs for Martian missions: an orbiter could refuel by scooping CO2 from the atmosphere of Mars, compressing the gas and liquefying it into storage tanks for the return journey or another interplanetary mission, whilst orbiting the planet.