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.
Attaching the VASIMR engine likely would require the services of spacewalking astronauts, but after installation it would be run from inside the outpost or remotely from ground control stations. It could actually be used to position the station, though the timing would be tricky, Glover added.
The company is looking to launch the engine in 2011 or 2012.
The purpose of having it on the station would be to test how the engine performs in the vacuum of space without having to undertake the additional costs and complexities of developing and flying communications systems, power supplies and other services to support the tests.
Glover sees no conflict with his firm's hopes to capture lunar transport business from NASA and the agency's plans to develop its own crew and cargo haulers under the Orion program.
"NASA has said repeatedly that it's open to private enterprise," Glover said. "If we develop on our own nickel this lunar cargo transportation system that would be complementary and helpful to NASA's efforts."
NASA plans to return astronauts to the moon by 2020 as the first step toward permanently extending humanity's presence beyond low-Earth orbit.
While the VASIMR engine Ad Astra plans to test would not be suitable for transporting people, it could stash fuel in lunar orbit for return trips to Earth. Eventually, the rocket engine could be upscaled to run off a nuclear reactor to power forays to Mars and beyond.
The advantage of nuclear-produced electricity to generate radio waves is that travel time to Mars could be cut from about nine months to 39 days.
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