Eight high-tech ways to propel a spaceship

From COSMOS magazine - News:

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.

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