It was a warm introduction from existing investor Khosla Ventures, a venture firm set up by Vinod Khosla, the billionaire founding chief executive of Sun Microsystems, that led to the Wexford-born chief executive of Realta Fusion talking to Future Ventures. Kieran Furlong was raising a series A round for Realta Fusion, an energy start-up exploring nuclear fusion, and Steve Jurvetson, the billionaire co-founder of Future Ventures, was interested in finding out more.  Jurvetson has a long track record of picking winners at an early stage, backing companies like Tesla, SpaceX and New York Stock Exchange-listed Planet Labs. Khosla and Future…