Advanced Space Propulsion Laboratory

PLASMA STUDY

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.

Efficient 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.

About 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.