Elon Musk has flown so high, so fast, it is hard not to wonder when, and how, he will crash to earth. How could he not? Musk is so many things – inventor, entrepreneur, billionaire, space pioneer, inspiration for Iron Man's playboy superhero Tony Stark – and he has pushed the boundaries of science and business, doing what others declare impossible. At some point, surely, he will fall victim to sod's law, or gravity.
He is only 41, but so far Musk shows no sign of tumbling earthwards. Nasa and other clients are queuing up to use his rockets, part of the rapid commercialisation of space. His other company, electric car manufacturer Tesla Motors, is powering ahead. Such success would satisfy many tycoons, but for Musk they are merely means to ends: minimising climate change and colonising Mars. And not in some distant future – he wants to accomplish both within our lifetimes.