(http://seattlep-i.nwsource.com/national/nasa261.shtml)

Standby to engage the warp drive, "Star Trek" fans: NASA scientists say that spacecraft fueled by antimatter engines could be only decades away.

Since the 1950s, science fiction writers have dreamed of a spaceship that would harness the enormous power of antimatter -- a material that explodes on contact with ordinary matter -- to voyage among the stars. Antimatter is itself no fantasy, but as a fuel it runs on the expensive side, currently about $6,400 trillion per gram.

Now, though, researchers have devised engines that would generate massive thrusts using minuscule amounts of antimatter, perhaps as little as 1 millionth of a gram for a one-year manned mission to Jupiter, according to a report in the current issue of the Journal of Propulsion and Power.

"The requirements for antimatter propulsion are much lower than anyone thought before," said physicist Gerald Smith, one of the co-authors and founder of Synergistic Technologies, a consulting firm that specializes in antimatter applications for the National Aeronautics and Space Administration and the Air Force.

Combined with technology that could bring the price of antimatter down by several orders of magnitude, the study concluded that "the prospects of exploiting antimatter for space propulsion are not so bleak after all and may indeed be quite favorable."

Antimatter propulsion would send space exploration hurtling forward. Scientists would be able to send advanced probes far beyond Pluto, through the mysterious Kuiper Belt, thought to be a birthplace of comets, and onward to the "heliopause," where the sun's radiation ends in the shock of interstellar space. And antimatter would bring rocket scientists a step closer to their ultimate goal: missions between the stars.

"If you look at the conventional technologies, they're just not good enough," said NASA's George Schmidt, another study co-author and deputy director of the Propulsion Research Center at the Marshall Space Flight Center. "That's why we are so excited about this."

Physicists believe every one of the fundamental particles that make up the universe has an antimatter twin, with the same characteristics but the opposite electrical charge.

Using high-energy particle accelerators, physicists can coax this antimatter into existence and peer into the "mirror world of the microcosmos," said Kurt Riesselmann, a spokesman for the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., one place where antiprotons are made.

Physicists usually hold antimatter in a vacuum, contained by powerful magnetic fields, because when it touches ordinary matter, the result is what physicists call an "annihilation event" -- the particles vanish in a burst of energy. Just one gram of antihydrogen, for example, would release the energy delivered by 23 of the space shuttle's external fuel tanks.

But together, the two main producers of antimatter, Fermilab and a European consortium known as CERN, now produce only about 10 nanograms (billionths of a gram) of antimatter annually, nowhere near the metric tons currently needed to reach other stars.

Development of antimatter as a fuel will require considerable research. But Smith has proposed engines that would use antiprotons to superheat tiny pellets of material, setting off tiny nuclear explosions and propelling the craft forward.

He said one technique, called "antimatter-initiated microfusion," could send a 100-kilogram payload on a 50-year trip outside the solar system while only burning 100 micrograms of antimatter.

The designs have been analyzed with computer models, but not tested, because there is not yet enough antimatter available.