Bringing Deep-Space Missions Within Our Gasp


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
(vol 16, p 923) Paul Marks

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