Advanced Space Propulsion
Laboratory
VARIABLE SPECIFIC IMPULSE MAGNETOPLASMA ROCKET
The VASIMR system encompasses
three linked magnetic cells, consisting of a “plasma source,” an
“RF booster,” and a “magnetic nozzle.” With this configuration,
plasma can be guided and controlled over a wide range of temperatures
and densities.
 The
plasma source cell involves the main injection of neutral gas (typically
hydrogen, or other light gases) to be turned into plasma and the
ionization subsystem. The RF booster cell acts as an amplifier to
further energize the plasma to the desired temperature using electromagnetic
waves. The magnetic nozzle cell converts the energy of the plasma
into directed motion and ultimately useful thrust.
The key to plasma rocket
operation is its capability to vary or “modulate” the plasma exhaust
while maintaining maximum power. This technique works like the
function of the transmission in a conventional automobile.
Two parameters are varied
during a typical operation: thrust and the velocity of the particles
leaving at the rocket exhaust. This latter is called the specific
impulse. As the ship accelerates on its journey, the thrust decreases
and the specific impulse increases. The opposite is also true
as the ship slows down at its destination.
Important Technology
- Super conducting magnets
at space temperatures.
- Compact power generation
and conditioning equipment.
- Compact and robust
radio frequency systems.
- Hybrid magnetic nozzle.
- Light weight heat
shields and radiative cooling.
| 
