Advanced Space Propulsion
The first step to understanding
how a plasma rocket operates is learning about plasma. A plasma
state can be achieved when a substance in its gaseous state is
heated to very high temperatures -- tens of thousands to millions
of degrees. At these temperatures, electrons are stripped, or
lost, from the neutral atoms. The result is electrons, which hold
a negative charge, and ionized atoms, which hold a positive charge,
mixed together making an electrically neutral "soup" of charged
particles that is a plasma.
This is a very common
occurrence in nature. In fact, 99 percent of the universe is in
some form of a plasma state, including lightning, very hot flames,
nebulas, the Sun and other stars. The plasmas at the extreme temperatures
required of a plasma rocket cannot be contained by any known material.
Fortunately, plasmas can be controlled by a magnetic field.
plasma generation, heating and controlled exhaust from the magnetic
nozzle are key challenges to the ASPL's experimental effort. Powerful
electromagnets create a strong magnetic field, which is similar
to a MRI medical scanner, necessary to control the hot plasma.
A large chamber creates the vacuum environment of space where
VASIMR must operate.
100 kilowatts of radio frequency power is available to study efficient
plasma heating techniques, key to impulse rocket operation. Experimenters
from around the world collaborate at the ASPL in developing and
installing diagnostic probes, which can unobtrusively measure
the properties of the plasma while withstanding its extreme temperature.