Using Fusion To Propel an Interstellar Probe
astroengine writes "We've heard of nuclear pulse propulsion being the ideal way to travel through interstellar space, but what would such a system look like? In the 1970's, the British Interstellar Society's (BIS) Project Daedalus was conceived to fire pellets of fusion fuel out the rear of an interstellar space probe that were ignited using a powerful laser system. The 'pulsed inertial confinement fusion' wouldn't be 'vastly different from a conventional internal combustion engine, where small droplets of gasoline are injected into a combustion chamber and ignited,' says Richard Obousy, Project Leader and Co-Founder of Project Icarus. Now, building on the knowledge of Daedalus, the researchers of Project Icarus have prepared a nifty animation of a fusion pulse propulsion system in operation on the original Daedalus vehicle."
http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)">Project Orion from the 1950s
And theoretically, you can get to 0.01c with solar sails. The original calculation is a bit screwy since it assumes a solar sail with mass including payload of 1 kg per square kilometer. But it ignores the effects of the Sun's gravity well. Acceleration deep in a gravity well and for which the vehicle escapes the gravity well results in more delta v than acceleration outside of a gravity well. This is called the Oberth effect. Further on down, someone cites a researcher who supposedly came up with a beryllium sail that could achieve 0.03c.