The Variable Specific Impulse Magnetoplasma Rocket (VASIMR®)

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR®) represents the future of translunar and interplanetary transportation as well as propulsion within Earth orbit. Its superb efficiency compared to that of a conventional chemical rocket allows double the payload mass for lunar delivery and half the transit time to Mars. Its robust design allows much greater power levels than existing electric propulsion systems and promises longer lifetimes. 

The Variable Specific Impulse Magnetoplasma Rocket, sometimes referred to as Electro-thermal Plasma Thruster or Electro-thermal Magnetoplasma Rocket, uses radio waves to ionize and to heat propellant and magnetic fields to accelerate the resulting plasma to generate thrust. This type of engine is electrodeless and as such belongs to the same electric propulsion family (while differing in the method of plasma acceleration) as the electrodeless plasma thruster, the microwave arcjet, or the pulsed inductive thruster class. It can also be seen as an electrodeless version of an arcjet, able to reach higher propellant temperature by limiting the heat flux from the plasma to the structure. Neither type of engine has any electrodes. The main advantage of such designs is elimination of problems with electrode erosion that cause rival designs of ion thrusters which use electrodes to have a short life expectancy. Furthermore, since every part of a VASIMR engine is magnetically shielded and does not come into direct contact with ionized plasma, the potential durability of this engine design is greater than other ion/plasma engine designs.

The engine design encompasses three parts: turning gas into plasma via helicon RF antennas; energizing plasma via further RF heating in an ion cyclotron resonance frequency (ICRF) booster; and using electromagnets to create a magnetic nozzle to convert the plasma’s built-up thermal energy into kinetic force. By varying the amount of energy dedicated to RF heating and the amount of propellant delivered for plasma generation VASIMR is capable of either generating low-thrust, high-specific impulse exhaust or relatively high-thrust, low-specific impulse exhaust.

For more information on the market applications or the science and story behind VASIMR®, navigate to the Missions or Technology pages. The VX-200 and VF-200 pages contain information on the experimental and flight models currently being tested. The inventor of VASIMR® and current Chairman and CEO of Ad Astra Rocket Company is, Dr. Franklin Chang-Díaz.

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