Reaching for the Stars - Antimatter Explored

In turn, the mass of the spacecraft would come down from 720 to 230 tonnes, and the 44-metre (144-ft) long engine would have a specific impulse of 130,000 seconds.

"It's quite impressive," Kammash said.

One of the most intriguing possibilities raised actually dates back to the 1950s and a concept developed by Philo Farnsworth, who pioneered most of the fundamental technologies for television in the 1920s and '30s.

"This is a really neat concept, something you can literally put your hands around," said Dr. Jon Nadler of NPL Associates, who is working with the University of Illinois Urbana-Champaign to develop the idea that Farnsworth had in 1950: fusion in a small bottle.

"You can use the power [it would generate] to power electric propulsion, or use the plasma for thrust," Nadler explained.

A star in a bottle
The technique is called inertial electrostatic confinement (IEC), a technique that avoids the use of massive magnets and laser systems used in other fusion-power techniques. Instead, the IEC device uses a hollow cathode, and the natural charges of electrons and ions, to form virtual electrodes that confine ions in a spherical region at the centre of the 61 cm (2 ft) diameter IEC vacuum chamber.

While true antimatter and true fusion propulsion will remain the "rockets of the future" for some time, a hybrid of the two might work in the near term.

"It's a good short cut," Schmidt said of antimatter-catalyzed fusion. In this approach, a small quantity of antiprotons is beamed into a fusion target. The resulting matter-antimatter annihilation heats a target enough to cause thermonuclear fusion.

Because of the energies and expense involved in producing antimatter, this method is not practical for power production on Earth. Overall, it is a net energy loser. Like all other forms of rocket propulsion, it's a sort of battery in which energy is expended to provide a large quantity in a tiny space, available on demand.

But, it could yield a rocket with a specific impulse of 13,500 to 67,000 seconds (30-147 times better than the Shuttle Main Engine), depending on the scheme used.

"Fusion missions would need just micrograms to reach the Oort cloud," the deep freeze of comets beyond the orbit of Pluto, Gerrish said. The antimatter load would cost about $60 million. But reaching the stars would require metric tons.

So a journey to the stars using antimatter alone may remain the stuff of books for just a little while to come.