At New Scientist, Michael Marshall describes ten hypothetical technologies that could propel spacecraft at greater distances and higher speeds than ever before. These aren't warp drives and hyperspace wormholes, but real science. One example is the ion thruster, which may be just a few years away from actuality:
Conventional rockets work by shooting gases out of their rear exhausts at high speeds, thus generating thrust. Ion thrusters use the same principle, but instead of blasting out hot gases, they shoot out a beam of electrically charged particles, or ions.
They provide quite a weak thrust, but crucially they use far less fuel than a rocket to get the same amount of thrust. Providing they can be made to keep working steadily for a long time, they could eventually accelerate a craft to high speeds.
They have already been used on several spacecraft, such as Japan's Hayabusa probe and Europe's SMART-1 lunar mission, and the technology has been improving steadily.
A particularly promising variant is the variable specific impulse magnetoplasma rocket (VASIMR). This works on a slightly different principle to other ion thrusters, which accelerate the ions using a strong electric field. Instead, VASIMR uses a radio-frequency generator, rather like the transmitters used to broadcast radio shows, to heat ions to 1 million °C.
Link via Gizmodo | Image: NASA