Richard Branson and Elon Musk have taken very different paths in their race to the heavens. But one is far ahead.

Elon Musk has just blown my mind. In an astonishing interview with Ross Andersen in the online magazine Aeon, he combines a apocalyptic view of earth's future with a visionary assessment of the practicality of space travel. This came just a week after a cargo-carrying Dragon space capsule, built by Musk's company SpaceX, arrived at the International Space Station. Following a flawless journey from Cape Canaveral in Florida, it delivered more than two tons of much-needed supplies. This is the point: Musk isn't just another Trekkie musing on the future of manned space travel; starting from scratch, he's successfully building the stuff to go there.

Musk thinks the earth's future is so dubious that it's urgent and crucial to seek an escape route to another planet. Mars, for example. There is, he says, "a strong humanitarian argument for making life multi-planetary."

I couldn't help thinking of that other self-made billionaire with long and loudly-promoted galactic ambitions, Richard Branson. At around the same time the Dragon docked with the space station, some 200 miles below on earth, Branson was announcing a new sponsor for his Virgin Galactic program to introduce space tourism: Grey Goose vodka.

Nothing could better describe the differences between Branson and Musk than these two events. This was the Dragon's fourth successful mission into space. Virgin Galactic's space program has yet to reach space, even though it was originally supposed to be taking tourists for the ride of their lives by 2007.

Indeed, early this year Branson said he expected the first passenger flight of his SpaceShipTwo would take place around now. Then it slipped to Christmas. Branson's latest prediction is "February or March" of 2015.

Meanwhile, Musk has just scored another coup by winning a $2.6 billion NASA contract to provide a space vehicle able to regularly ferry as many as seven astronauts to the space station. SpaceX will share that mission with Boeing, whose own space ship will cost a lot more: $4.2 billion. As in all his endeavors, Musk is a creative disruptor, claiming that his private company is leaner, nimbler and more innovative than traditional aerospace contractors like Boeing. (The Sierra Nevada Corporation, whose bid was rejected, is challenging in court NASA's award of these contracts.)

I've never had any doubt of Branson's passion is in his own mission to put ordinary mortals into space; if he could personally have willed it to happen he would have, long ago. His previous promotion of the first round-the-world solo flight without refueling, achieved by pilot Steve Fossett in 2005, and similar attempts with balloons, displayed total commitment and courage. 

But the problem with Virgin Galactic is that Branson has never had any real grasp of how serious the technical challenges are. As a result, he continually overpromises and under-delivers.

Musk is a different animal, personally and professionally. Against Branson's piratical beard and flowing locks he has the barbered and polished look of a natural CEO (with more than a hint of steel in the soul) and the gift of technical fluency. Branson has no technical background; he's an engaging, flamboyant and brilliant salesman and creator of a brand, Virgin, that has gone through many iterations ranging from airlines to cola, music to cell phones, some hits, some not. 

Musk moved seamlessly from a degree in physics at the University of Pennsylvania and an economics degree at the Wharton School to applied physics at Stanford. But he self-ejected from there after only two days and scorched a path into technical entrepreneurship, seeing the potential of PayPal, selling it to eBay and cashing out as a billionaire. He founded SpaceX in 2002. (And Tesla Motors a year later.)

It may be that, paradoxically, it is a lot harder to get six passengers and two pilots into a sub-orbital joy ride than it is to get seven astronauts to the space station — simply because it has never been done before.

Along the way Musk has become as much — or more — of a space promoter as Branson. In his Aeon interview, he balances extraterrestrial hubris — "At our current rate of technological growth, humanity is on a path to be god-like in its capabilities" — with End of Days pessimism: "It could be that there are a whole lot of dead, one-planet civilisations." And some of his terrestrial projects can seem far-fetched, like a giant vacuum tube through which people would hurtle in capsules between Los Angeles and San Francisco. But there has been nothing dream-like about his selection of engineers at SpaceX or his tight focus on upending what he sees as the scientific orthodoxy of corporations grown fat on military and NASA contracts. 

The Boeing and SpaceX ferries will replace the Russian Soyuz capsules that are now the only means of getting astronauts to and from space. The Russians charge $71 million a seat. So far this year NASA has spent more than $400 million on these rides.

Boeing's contender will return to earth using the same technique as the Soyuz capsule, originally designed in the 1960s — after re-entering the earth's atmosphere it will deploy parachutes and, finally, a cushion to soften touchdown. Musk's contender is, typically, more sophisticated and more challenging. Instead of descending suspended from parachutes it will descend under its own power, in the final stage using rocket thrust to brake the fall and — it is claimed — land with the precision of a helicopter. 

Virgin Galactic is, literally, aiming far lower than SpaceX. It will barely reach space at all, given that the entry point of space is fixed at 62 miles above earth and SpaceShipTwo is designed to reach an apogee of 68 miles and then fall back to earth — these are sub-orbital flights, more ballistic than galactic. 

Musk's capsules — the cargo ship and the future astronaut ferry — are launched atop his own Falcon 9 rockets. To reach orbit they have to exit the pull of gravity at a speed of more than 17,000 miles an hour. Compare that with SpaceShipTwo, which needs to top out at 2,500 miles an hour and is yet to reach that speed.

In fact, Branson's chosen system is looking increasingly problematic. It combines two vehicles, a jet-powered mother ship, WhiteKnight Two, which climbs to 50,000 feet and SpaceShipTwo, which drops from the mother ship and then blasts away with a short rocket burst.

It's the rocket engine that has failed to deliver. Coming as close to acknowledging this as he ever has, Branson told Bloomberg Television last week, "It took us a lot longer to build rockets that we felt completely comfortable with." On its last test flight SpaceShipTwo reached its highest point yet, 71,000 feet, but that was with only two pilots on board and the vehicle has still not reached half of its intended 2,500 miles an hour top speed. There are suspicions that the rocket engine is not powerful enough to get a full load of eight people — the pilots and six passengers — into the planned trajectory. 

Galactic's test flights — over the years they have decreased greatly in frequency — take off from an airfield at Mojave, Calif. However, their lack of progress is keenly felt in New Mexico, where Virgin Galactic is the anchor tenant of the purpose-built Spaceport America, located just outside of a town called Truth or Consequences. It was built to be ready for the first passenger flights in 2012.

Building the Spaceport cost New Mexico taxpayers $212 million. Sierra County, where it is based, is funding the project to the tune of $300,000 a year and Walter Armijo, the county commissioner, is not happy. "They promised jobs, tourism and housing and we haven't seen any of that," he told Reuters. "None of these expectations and promises have come true." 

(Musk is there, too, having taken a three-year lease at Spaceport for testing reusable rockets.)

Galactic has taken more than $80 million in deposits from around 800 people (the actual number is a bit squishy) who are prepared to pay $250,000 each for a ride. They have been promised spectacular views with a curved horizon and about five minutes of weightlessness before the ship glides back to earth.

Technical challenges aside, there are safety issues to be resolved. The FAA will have to certify SpaceShipTwo as airworthy, but there are as yet no protocols in place for that process. Passengers will need to take out special insurance policies, and given the ticket price, most will be high net worth individuals with families and businesses averse to risks — they include Leonardo DiCaprio, Stephen Hawking and Brangelina.

It may be that, paradoxically, it is a lot harder to get six passengers and two pilots into a sub-orbital joy ride than it is to get seven astronauts to the space station — simply because it has never been done before. The test program has shown that the science is tricky and sometimes uncertain — aerodynamic glitches have surfaced and had to be fixed. 

Musk, on the other hand, is riding on the back of several generations of manned space travel in which the basic parameters were established long ago. It requires a hugely powerful rocket to carry a vehicle into orbit and a space vehicle able to withstand the furnace heat of re-entry and get its occupants safely back to earth. 

Nonetheless it is remarkable that a newcomer like Musk can gatecrash an industry as entrenched and as experienced as this one and demonstrate not only an ability to equal the best minds in the business but also to deliver a quality that matters above all others: dependability. He has underpinned his future program by winning from NASA a 20-year lease on the legendary launch pad 39A at Cape Canaveral. 

Branson's achievement with Virgin Galactic is to have created a market that appeals to people like him — the ultimate trip. Space tourism is not going to break any scientific boundaries, and it's an expensive way to earn bragging rights. But those 800 early adopters are still waiting for the ride to show up. Right now, Branson might do well to raise a toast to Musk (Grey Goose, of course) and reflect on the fact that sometimes a dream that involves defying gravity can turn into an albatross.