Antimatter would 'give us the stars'

By Dr David Whitehouse
BBC News Online science editor

The next few years will see a revolution in unmanned space probes as new technologies are developed, according to Les Johnson of the US space agency (Nasa).

Deep space missions will not be the same

Johnson, In-Space Transportation manager at the Marshall Space Flight Center, is a member of a team looking at new ways to propel spacecraft. This includes nuclear power, solar sails, tethers and even antimatter.

Some of these new technologies will find their way on to space missions within the next decade, allowing them to traverse the Solar System with unprecedented speed.

When they get to their goals, probes will not just fly past them; they will have the ability to go into orbit for long-term scientific studies.

Looking far into the future, Les Johnson says an antimatter drive would be the development to "give us the stars".

Reaching the limit

"It all boils down to the availability of energy. With a chemical rocket, energy is not released efficiently," he told BBC News Online. "We have reached the limits of what chemical rockets can do."

Les Johnson and his team are working on three technologies that will come to fruition over the next few years.

If we get to the point where we will be making kilograms of antimatter then the stars are going to be ours

Les Johnson, Nasa

Solar-electric propulsion systems that draw energy from the Sun, converting it to electrical power to accelerate on-board fuel to generate thrust.

Compact, kilowatt-strength solar-electric propulsion systems onboard spacecraft could reduce fuel loads and make room for larger science payloads.

"We could use electric propulsion to get a space mission going and when it reaches its goal use the technique of aerobraking - if the destination world has an atmosphere," he says.

Aerobraking involves dipping into the atmosphere briefly to allow friction to reduce the spacecraft's speed so that it can enter orbit.

The technique - not unlike a child on a swing dragging its feet in the dirt to slow down - has already been used successfully on Mars missions.

Aye, aye captain

Huge solar sails that use sunlight as a propulsive force are also being developed.

So too is so-called tether technology, which involved dragging an electrically conducting wire, possibly several kilometres long, through the Earth's magnetic field. The interaction produces a propulsive force that can be utilised.

Les Johnson examines tether technology

"Once you think about the more challenging missions that could be done, you soon realise how inadequate chemical propulsion is," Johnson adds.

Dreams about Star Trek notwithstanding, the use of an antimatter propulsion system could revolutionise manned and unmanned space travel. However, it is a long way off.

At the moment, we are far from understanding even the basics of antimatter production and containment. In the few experiments conducted so far, only a few thousand antimatter atoms have been made.

Faster and larger probes will be able to visit the planets

But the enormous energy that is released when matter and antimatter combine could, in principle, provide a far more efficient propulsion system.

For small unmanned probes, only grams of antimatter would be required.

"With small amounts of antimatter we would be able to conceive of sending robotic probes to the closest star system - Alpha Centauri - and getting data back within a human lifetime," says Les Johnson.

"If we get to the point where we will be making kilograms of antimatter then the stars are going to be ours."