Variable Specific Impulse Magnetoplasma Rocket

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an electromagnetic thruster for spacecraft propulsion. It uses radio waves to ionize and heat a propellant. Then a magnetic field accelerates the resulting plasma to generate thrust (plasma propulsion engine). It is one of several types of spacecraft electric propulsion systems.

The VASIMR method for heating plasma was originally developed from nuclear fusion research. VASIMR is intended to bridge the gap between high-thrust, low-specific impulse and low-thrust, high-specific impulse systems. VASIMR is capable of functioning in either mode. Former NASA astronaut Franklin Chang Díaz created the VASIMR concept and has been developing it since 1977.

VASIMRs units for development and test are assembled by Ad Astra Rocket Company.

VASIMR, sometimes referred to as the Electro-thermal Plasma Thruster or Electro-thermal Magnetoplasma Rocket, uses radio waves to ionize and heat the propellant, which is then accelerated with magnetic fields to generate thrust. This engine is electrodeless, of the same propulsion family as the electrodeless plasma thruster, the microwave arcjet or the pulsed inductive thruster class. It has been described as an electrodeless version of an arcjet rocket that can reach higher propellant temperature by limiting the heat flux from the plasma to the structure. Neither type of engine uses electrodes. This eliminates the electrode erosion that shortens the equipment life of rival ion thruster designs. Since every part of a VASIMR engine is magnetically shielded and does not directly contact plasma, the durability of this engine is predicted to be greater than many other ion/plasma engines.

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