Atomic surfing: A pulse-propulsion craft would detonate small nuclear bombs behind it, and could surf the shockwaves all the way to Mars in as little as one month (artist's impression pictured).
Credit: NASA
SYDNEY: What does it take to boldly go where no man has gone before? Conventional rockets fire hot gas through a nozzle to get thrust, but that can't get us to deep space.
Rocket scientists have come up with a raft of solutions – some remain in the realm of science fiction, but others verge on reality. Here's a selection of those that might one day carry us across the final frontier.
NUCLEAR PULSE PROPULSION
Propelling your spaceship by setting off teeny atomic explosions isn't as crazy as it sounds, according to NASA. A pulse-propulsion craft would detonate small nuclear bombs behind it, and could surf the shockwaves all the way to Mars in as little as one month. Leaving radioactive debris as space junk in the vicinity of Earth (or other planets) probably isn't a good idea, though.
SOLAR THERMAL PROPULSION
For this you'll need some serious bling: NASA's prototype uses a sapphire concentrator to collect light from the Sun or other stars and create a powerful beam to heat hydrogen gas, which is ejected through a nozzle to provide thrust. But it's worth noting that this method would not work on the dark side of a planet or far away from a star.
VACUUM-POWERED SPACECRAFT
Arthur C. Clarke used "vacuum fluctuation" to send characters to deep space decades ago. But G. Jordan Maclay of research company Quantum Fields LLC in Wisconsin, USA, says vacuum-powered spacecraft are possible. His idea is to build a spacecraft that harnesses the Casimir effect: the attractive force between two uncharged metal plates set a few micrometres apart, caused by quantum vacuum fluctuation in the electromagnetic field. As the plates move closer together, the force gets stronger, and Macleay's engine would use energy generated by moving the plates closer before separating them again. The catch? Materials engineers are still light-years away from making this technique practical.
MAGNETIC SAILS
Unlike well-known solar sails, magnetic sails are completely invisible. Much like the Earth's protective magnetic field, an artificial magnetic field around a spacecraft would deflect the solar wind. This would be used to provide thrust; acceleration would start slowly, but NASA says that after three months a magnetic sail-powered spacecraft could be zipping along at more than 280,000 km/h.
ARTIFICIAL GRAVITATIONAL FIELDS
Anti-gravity engines might be possible according to the controversial Extended Heim Theory, which attempts to reconcile general relativity and quantum physics. Scientists have reported anti-gravitational effects, generated with a spinning, superconducting magnet. Jochem Häuser, a physicist at the University of Applied Sciences in Salzgitter, Germany, says that this should produce particles called 'gravitophotons', which have both electromagnetic and gravitational properties. They would produce a gravitational field that pushes against the engine itself, thus accelerating a spacecraft.
SOLAR SAILS
Instead of catching a light breeze, a solar sail catches sunlight – and the minute force of photons bouncing off can move a craft through space without fuel. The sail itself is a reflective sheet 100 times thinner than paper. It might sound too delicate to move anything, but both the NASA Jet Propulsion Laboratory and the Planetary Society, based in Pasadena, California, plan to test real prototypes in space soon. Like solar thermal propulsion, this method leaves the spacecraft helpless in the dark.
DARK ENERGY WARP DRIVE
As any sci-fi fan could tell you, a warp drive creates a bubble of normal space-time and expands or contracts the space-time around it to move a spacecraft faster than the speed of light. According to a 2008 study from string theorists at Baylor University in Texas, the power required might come from manipulating dark energy, the mysterious force accelerating the expansion of the universe. Exactly how to harness it, though, is anyone's guess. Even then, the researchers say the spacecraft would consume the entire mass of Jupiter just to move 10 m at light speed, so it wouldn't get any points for fuel efficiency.
ANTIMATTER ENGINES
How could antimatter engines whisk a spacecraft to Mars in six weeks? At first glance, it looks like a conventional rocket – the products of matter-antimatter collisions would heat a gas and propel it through a nozzle. But researchers at Pennsylvania State University say it's a case of less being more: just one gram of antimatter could provide as much energy as 1,000 external fuel tanks currently strapped to NASA's s pace shuttle prior to take-off.
