Many things can be said about Elon Musk, but there are a few worth noting: he thinks big, he thinks in a straight line and he's got very rich that way. And, he can really pull a crowd.
Speaking to a full house at the Royal Aeronautical Society on 16 November, the man who made a fortune as co-founder of the ubiquitous internet funds handler PayPal (Forbes magazine pegs his net worth at $2 billion), before going on to launch electric car and space rocket companies, spoke almost exclusively about the future. Like many entrepreneurs, Musk's vision of the future includes features - from which he hopes to make money - that the rest of us have not thought of. But to hear him talk about the wildly ambitious is to be turned on to ideas that would have seemed mad earlier in the day. Indeed, by the time he had finished, more than a few engineers in the crowd were visibly crackling with inspiration.
His rocket company Space Exploration Technologies, or SpaceX, is already turning space travel on its head as a nimble private company venturing into territory formerly controlled by big government bureaucracies. Now, SpaceX has earned some $2 billion worth of contracts from NASA to rocket supplies and, perhaps from 2015, even astronauts, to the International Space Station. But while his Falcon 1 and Falcon 9 rockets have so far chalked up some successes - including one trip to the Space Station - low-Earth orbit is barely a stepping stone.
As spacex.com puts it plainly: "the company was founded in 2002 by Elon Musk to revolutionise space transportation, with the ultimate goal of enabling people to live on other planets." Nobody thinks bigger than that, and Musk left the RAeS crowd in no doubt that Mars is not an idle "mission statement". Musk isn't really putting a date on it, but he imagines he will have to go to Mars himself and live in the self-sustaining human colony that SpaceX will be instrumental in establishing.
The genius of Musk - or at least the force that brings an audience along with him - is a great ability to draw a straight line between some starting point (Falcon 1) and a desired end point (self-sustaining colony of at least 8,000 people on Mars) and not get too bogged down in the details of intermediate steps. Musk reckons a round-trip ticket to Mars needs to cost half a million dollars because that's an amount of money that makes it accessible to middle-class people prepared to work hard and save for it.
Working backwards from $500,000, he sees two critical enabling technical pillars. One is "total and frequent" reusability of spacecraft. Another is a rocket much bigger than Falcon 9 that is powered by liquid oxygen-methane fuel, because methane is easier to handle than hydrogen and for the return trip, it can be synthesised in Mars's CO2 atmosphere. Everything in between is details.
Those details, of course, might easily derail Musk's dream. SpaceX has started work on a fully-reusable rocket stage for vertical landing. But rocket development is costly, and as Musk admitted to the RAeS, after three failures of the Falcon 1 rocket, in 2008, "I'd run out of money". A fourth flight - thankfully, he says - was a success, giving customers and investors the confidence to stay on board.
As a private company, SpaceX's financial condition is opaque, but all will be revealed if, as anticipated, Musk takes it public in 2013. An initial public offering would be a high-profile US media event, led as it would be by a technology entrepreneur who is filling in where the Space Shuttle left off and served as the inspiration for Marvel Comic's Tony Stark character in the Iron Man films.
But beyond underpinning SpaceX finances, an IPO might also give some indication of whether or not Musk is out on his own with his Mars dreams. Prospective investors may calculate that a 40-launch manifest stretching through 2017 and a reusable rockets and capsules development programme is a good growth prospect, even if they dismiss Mars as too distant a project to worry much about. Or, investors might ask if SpaceX's "ultimate goal of enabling people to live on other planets" is not a financially dangerous distraction.
Musk told his RAeS audience that he is "hopeful" the first Mars mission will be a government-private partnership, but added that he had to prepare for an all-private effort: "It needs to happen one way or the other."