Plasma power could usher in human travel to Mars

Artist's concept of plasma-fueled spacecraft

June 15, 2000
Web posted at: 12:17 PM EDT (1617 GMT)

In this story: Most of cosmos a plasma soup Magnets to control unruly fuel RELATED STORIES, SITES

By Richard Stenger
CNN Interactive Staff Writer

(CNN) -- A rocket fueled by what some scientists consider a fourth state of matter could boost payload capacity and slash travel time to Mars, according to NASA, which agreed this week to work with a Montana company to develop the advanced technology.

Rockets powered by electrically charged plasma gas could carry a cargo of more than 100 tons and reach the red planet in only three months, NASA said. A mission fueled by a conventional chemical rocket would require at least eight months to reach Mars.

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The shorter trip would reduce astronaut exposure to deadly space radiation, and possibly minimize biological changes associated with weightlessness, like bone and muscle deterioration and circulatory changes.

"We don't want to spend a lot of time traveling from point A to point B in space. We want to make that trip very fast," said Franklin Chang-Diaz, the director of plasma propulsion research at NASA's Johnson Space Center in Houston.

Chang-Diaz said plasma could serve as rocket fuel within the decade and that NASA could conduct an orbital test flight as early as 2004.

Elements of a plasma engine (click image for details)

"We'd take it out for a spin and see how it works," the former astronaut told a news conference Wednesday.

The NASA lab will collaborate with MSE Technology Applications in Butte, Montana, to develop the advanced propulsion technology, according to the agreement announced Tuesday. The Montana team is involved in simulating the effects of plasma propulsion.

"We have to use computer models before we actually cut metal to do tests," Chang-Diaz said.

When a gas is heated to tens of thousands or millions of degrees, atoms lose their electrons. The result is a "soup" of charged particles, or plasma, made up of negatively charged electrons and positively charged ions.

Plasma occurs commonly in nature. In fact, most matter in the universe is in the plasma state, including stars, nebulas and, closer to home, lightning and extremely hot flames.

No known material can contain the hot plasmas necessary for rocket propulsion, but specially designed magnetic fields can. Such magnetic fields are integral to the Variable Specific Impulse Magnetoplasma Rocket (VASIMR), a concept designed by Chang-Diaz over three decades of research.

A rocket prototype filled with superhot plasma at Johnson Space Center

The VASIMR engine consists of three linked magnetic cells. In the first, a propellant gas, like hydrogen, is injected and ionized. The second uses radio waves to heat up the plasma more, sort of like a microwave oven. And the third, a magnetic nozzle, converts the energy into a directed flow.

On a mission to Mars, a plasma rocket would continuously accelerate through the first half of its voyage, then reverse and slow down during the second half. Therefore, a key to the technology is the ability to vary the plasma exhaust.

"That's important because there are portions of the mission that require high thrust. And other times that require high efficiency," said Dave Micheletti, manager of MSE's advanced energy and aerospace program.

The propulsion system would create very low artificial gravity, which some scientists have theorized could offset the biological hazards of space travel. Yet the gravity would only be about one-thousandth as strong as that of the Earth, said Chang-Diaz.

"We don't know the thresholds of beneficial gravity. That's one of the things that our medical researchers are still trying to pin down," he said. In the future, when plasma powered ships become much faster, gravity levels would go way up, he added.

Chang-Diaz said his lab and related NASA centers spend only several million dollars a year on plasma research. "That's nothing near a major enterprise. We need to ramp up development" if NASA decides to move forward with plasma propulsion, he said.

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