starship-design: Plasma power could usher in human travel to Mars

["L. Parker" <lparker@cacaphony.net>]

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Plasma power could usher in human travel to Mars

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

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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.
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 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.

"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.
Most of cosmos a plasma soup
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.
Magnets to control unruly fuel

The VASIMR engine consists of three linked magnetic cells. In the
first, a propellant gas, like hydrogen, is injected and ionized. The
second use 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.
"People do love to go to weird places for reasons we can't imagine --
mostly because they have too much money."
                            - Freeman Dyson

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