Encyclopedia > Variable specific impulse magnetoplasma rocket
The Variable specific impulse magnetoplasma rocket (VASIMR) is a hypothetical form of spacecraft propulsion that uses radio waves and magnetic fields to accelerate a propellant. VASIMRs are intended to bridge the gap between high-thrust, low-specific impulse propulsion systems and low-thrust, high-specific impulse systems, as they are capable of functioning in either mode simply by adjusting their parameters of operation. NASA image of VASIMR rocket test - This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ...
NASA image of VASIMR rocket test - This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ...
A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is used to change the velocity of spacecraft and artificial satellites, or in short, to provide delta-v. ...
In physics, a magnetic field is an entity produced by moving electric charges (electric currents) that exerts a force on other moving charges. ...
A propellant is a material that is used to move an object by applying a motive force. ...
For the land-speed record breaking car, see ThrustSSC and Thrust2 For the computer game, see Thrust (computer game) Thrust is a reaction force described quantitatively by Newtons Second Law when a system expels or accelerates mass in one direction to propel a vehicle in the opposite direction. ...
The specific impulse (commonly abbreviated Isp) of a propulsion system is the impulse (change in momentum) per unit weight/mass of propellant. ...
Current VASIMR designs should be capable of producing specific impulses ranging from 10,000-300,000 m/s (1,000-30,000 seconds) - the low end of this range is comparable to some ion thruster designs. Even if relatively high thrusts become available, VASIMR drives are expected to require a great deal of heavy machinery to confine even relatively diffuse plasmas, so they are will be unusable for very-high-thrust applications such as launch from planetary surfaces. An ion engine test An ion thruster is one of several types of spacecraft propulsion that uses beams of ions for propulsion. ...
 The propellant, usually hydrogen, is first ionized by radio waves and then is guided into a central chamber threaded with magnetic fields. The ions spiral around the magnetic field lines with a certain natural frequency; by bombarding them with radio waves of the same frequency, the system heats the ions to 10 megakelvins. A magnetic nozzle converts the spiralling motion into axial motion, driving the hydrogen ions out the back of the rocket and producing thrust. NASA diagram of VASIMR rocket functioning - This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ...
General Name, Symbol, Number Hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1, s Density, Hardness 0. ...
An ion is an elementary particle or system of elementary particles with a net electric charge. ...
Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...
The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ...
The radio waves and magnetic fields would be produced by electricity, which would most likely be produced by nuclear fission. Any conceivable chemical fuel used in a fuel cell or to activate a generator would be more efficiently used in a conventional rocket. Solar energy might be more efficiently used in a solar thermal rocket, which would have lower specific impulse but higher energy efficiency. The article on electrical energy is located elsewhere. ...
Sketch of induced nuclear fission, a neutron (n) strikes a uranium nucleus which splits into similar products (F. P.), and releases more neutrons to continue the process, and energy in the form of gamma and other radiation. ...
A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ...
A Redstone rocket, part of the Mercury program A rocket is a vehicle, missile or aircraft which obtains thrust by the reaction to the ejection of fast moving exhaust gas from within a rocket engine. ...
Solar thermal propulsion is a form of spacecraft propulsion that makes use of solar power to directly heat reaction mass, and therefore does not require an electrical generator as most other forms of solar-powered propulsion do. ...
By adjusting the manner of heating and a magnetic choke, a VASIMR can control the exhaust rate. Closing the choke shifts the rocket into high gear; it reduces the number of ions exiting the drive (thus producing less thrust), but keeps their temperature high (thus increasing specific impulse). Opening the choke has the reverse effect. A spacecraft would use low gear to climb out of planetary orbit, and high gear for interplanetary cruise.
The method of heating plasma used in VASIMR was originally developed as a result of research into nuclear fusion. One possible future enhancement of the VASIMR system may be to promote fusion among the atoms of the propellant; this could provide a great deal of extra heating, and therefore provide even greater thrust than the electrical input into the system would otherwise allow. However, such an enhancement is not expected to be practical in the near future. The word plasma has a Greek root which means to be formed or molded (the word plastic shares this root). ...
The deuterium-tritium fusion reaction is considered the most promising for producing fusion power. ...
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