On March 31, Richard Dinan, the CEO of British start-up Pulsar Fusion, took to the stage at the Mars Conference organized by Amazon founder Jeff Bezos in Ojai, California, to pitch his company’s tech to a crowd of space exploration enthusiasts. Dinan, now 40, is a one-time contestant on a reality show about rich young Londoners, but has lately gained attention with his pet project — a venture developing nuclear fusion propulsion systems for spaceships bound for Mars and beyond.