Plasma Rocket May Be Tested at Space Station

Aug. 7, 2008 -- NASA is considering flying a prototype plasma rocket engine designed by a former astronaut to the International Space Station for testing, officials said Wednesday.

The engine is called a Variable Specific Impulse Magnetoplasma Rocket, or VASIMR, and if that sounds like something you'd see on Star Trek, you're not too far from the truth.

Rather than heating chemicals and directing the resulting gases through high-temperature metal nozzles, VASIMR uses radio waves to create and speed up free-flying, electrically charged particles known as plasma. The concoction is then herded through nozzles made of magnetic fields, not metals like traditional rocket engines.

The sun and stars are made of plasma and physicists believe magnetic fields shape the tell-tale jets of gas generated by black holes.

Seven-time shuttle flier Franklin Chang Diaz worked on the rocket at NASA until 2005 when he left to start the Ad Astra Rocket Co. of Webster, Tex., to continue its development. The privately financed venture has invested about $25 million so far in VASIMR. NASA has continued to support the project by lending equipment, lab space and personnel.

Now Ad Astra is in negations with the U.S. government to mount its rocket engine to the space station for testing. The engine is designed to work only in the vacuum of space.

It uses solar cells to draw energy from the sun to produce electricity, which in turn generates radio waves to heat argon into plasma. A magnetic field, made by running an electrical current through superconducting magnets, directs the plasma as it is pushed out of the engine, creating thrust.

"The first application we see a market for is hauling things from low-Earth orbit to low-lunar orbit," said Tim Glover, Ad Astra director of development.

The journey would take about six months, but the rocket would be able to haul about 2,000 pounds, roughly twice the load of similarly-sized chemical engines. VASIMR engines also are reusable, so depending on how long the solar cells lasted, each spaceship could make six or more round-trip journeys, Glover said.

NASA has flown ion engines before, most notably on the 1998-2001 Deep space probe that visited a comet and more recently on the Dawn spacecraft, which was launched last year for asteroid studies.

Glover said Ad Astra is currently assessing various locations on the space station where the rocket could be attached -- there are power, radio interference and other operational issues -- and how to get VASIMR delivered.

With the space shuttles due to retire in 2010, Glover said launch options include Japan's cargo hauler, the HTV, which is due for its debut flight next year. The firm also is in informal talks with potential commercial launch service providers in the United States.

NASA is hoping to turn over station cargo delivery services to the commercial sector after the shuttle's retirement but currently none have demonstrated the capability to undertake the work. NASA is backing efforts by two potential providers, Space Exploration Technologies and Orbital Sciences Corp.