Solar Sails

Dreamt up at the beginning of last century, solar sails are now moving a step closer to reality, as one of the most feasible ways of traveling into deep space.  They are lightweight panels made from reflective material that act like the sails of a boat.  Rather than using wind, the sails are actually propelled by light.  Unbelievable as it may seem, the stream of light particles (called photons) emitted from the Sun are strong enough to push a mini-spacecraft right out of the Solar System and beyond into interstellar space.

One of the major limitations on our current missions is the weight of the fuel needed to blast rockets out of the Solar System.  To travel further, a rocket needs more fuel, but more fuel means more weight, slowing the spacecraft down and making it less efficient.  As solar sails are powered by sunlight, they don't need to carry onboard fuel like conventional rockets and so are lighter and easier to propel.  Steering vanes at each corner of the solar sail panel could pilot the spacecraft through the Solar System.  For long missions, an on-board laser or microwave transmitter would be fitted to provide power when the Sun is just a distant memory.

Initial acceleration is low, meaning that solar sails could only carry robotic probes.  However, because they are so lightweight and have a continuous source of energy, they could eventually accelerate to speeds of around 90 km per second.  At that speed, they could travel from London to New York in just over a minute; that's over 10 times faster than the Space Shuttle.  In addition, unlike current spacecraft, they are reusable and do not require costly refueling for new missions.

Source: Outbound, by George Mason  

Picture: http://www.nasa.gov.com/