Antimatter Could Carry Us to the Edges of the Solar System
Source: New Scientist
October 14, 2000
Bold enterprise
AN antimatter-aided space drive might bring deep-space
missions within our grasp. Engineers at NASA and Pennsylvania State
University say that by the end of the century, spacecraft could reach
the edges of the Solar System and
beyond.
They believe an antimatter drive could lead to a
one-year round trip to Jupiter, a five-year trek to the
heliopause--the boundary separating the Solar System from interstellar
space--and, in a 50-year trip, the Oort Cloud, source of the comets.
Antimatter is a mirror image of the matter we see around
us. Its particles are identical in mass but opposite in electrical
charge to their normal counterparts. Antiprotons can be made in a
particle accelerator by smashing very high-energy protons into one
another. When antimatter comes into contact with normal matter both
are annihilated, releasing enormous
amounts of energy, so it must be carefully contained in electric and
magnetic fields.
Because making antimatter uses up vast amounts of energy
only tiny quantities can be manufactured today--less than 10 nanograms
per year. So many scientists have ruled out an antimatter drive as
impractical. But George Schmidt and colleagues at the Propulsion
Research Center of NASA's Marshall Space Flight Center in Huntsville,
Alabama, think otherwise.
The key, NASA says, is to get away from the idea that
you have to annihilate antimatter to create propulsive power. Schmidt
and his colleagues have calculated that far smaller quantities of
antiprotons would be needed if they were used to initiate a more
efficient hybrid fission/fusion drive.
They studied one scheme, pioneered at Penn State, called
antimatter initiated microfusion (AIM), in which an antiproton plasma
is repeatedly compressed using electric and magnetic fields. A droplet
of deuterium and helium-3 is mixed with uranium-238 and injected into
the plasma. "Antiprotons create a unique type of fission, producing
six times more neutrons in the uranium than normal fission," says
Schmidt. These
neutrons blast the helium-deuterium mixture, making the nuclei fuse.
Hot fusion products create thrust.
An AIM drive needs between 1 and 100 micrograms of
antimatter per mission-- depending on the speed required (see Table).
Such quantities seem huge now, but researchers at the Fermilab
accelerator centre near Chicago are doubling their output of
antiprotons every year, says Elvin Harms of Fermilab's
Antiproton Source. But over the next century, microgram quantities are
"probably not out of the question," he says. Schmidt also expects
private companies to start making antiprotons for new types of medical
imaging.
Source: Journal of Propulsion and Power
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Paul Marks