Gregory Benford, professor of
physics at UC Irvine (and noted science fiction author) believes that a
spacecraft powered by a special kind of solar sail could reach Mars in just one
month.
Dr. Benford and his brother James were testing a very
thin carbon-mesh sail, using microwaves as the energy source for propulsion.
Unexpectedly, the sail experienced a force considerably greater than predicted.
They theorized that the heat from the microwave beam was causing carbon monoxide
gas to escape from the sail's surface; the recoil from the escaping molecules
provided what could be a useful adjunct to the propulsive force experienced by
light sails.
They believe that by beaming microwave energy up from
Earth to boil off volatile molecules from a specially formulated paint applied
to the sail will provide enough added force to propel a spacecraft to Mars in
record time. "It's a different way of thinking about propulsion," Gregory
Benford says. "We leave the engine on the ground." Their research will be
published this month in the journal Acta Astronautica.
This is how it would work: a rocket would take the
craft to low-Earth orbit, whereupon the craft would unfurl a 100 meter diameter
sail. A transmitter on Earth would fire a one-hour burst of microwaves at it to
heat it up, accelerating the craft to 60 kilometres per second. This would set
an interplanetary speed record for space probes.
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Flying away on a wing and a
prayer: The Canadian Solar Sail Project for a
proposed race to the
moon in 1992 in honor of the 500 year anniversary of
Columbus coming to
America.
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However, more work is needed to make this possible.
The plan would require a 60-megawatt microwave beam with a similar diameter as
the sail that was capable of tracking the craft. The deep-space communications
network that NASA uses to communicate with Mars rovers and the Cassini probe now
orbiting Saturn can only output half a megawatt.
If this design could work, it would make significant
progress in the use of ground-based beam-propulsion designs. As science fiction
readers know, this topic was explored in the 1974 novel Mote in God's Eye
by Larry Niven and Jerry Pournelle. They used the idea of laser cannon from Robert L. Forward's
1961 paper Ground-Based Lasers For Propulsion In Space to bring an alien
spacecraft to our solar system. Readers may also wish to explore early sf looks
at solar sails.
Read a bit more about Gregory Benford; the
article First Flight By A Laser-Powered Airplane chronicles an earlier effort at ground-based propulsion. See
also Solar super-sail could reach Mars in a
month and Acceleration of Sails by Thermal
Desorption of Coatings (pdf).
(This Science Fiction in the News story
used with permission from Technovelgy.com - where science meets
fiction.)
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