As far as home planets go, the Earth ticks most of the boxes: oxygen, water, food and lovely views. But there are risks to be considered too. What if a nuclear war, an asteroid collision or a rogue AI sent it all up in smoke, blotting out our own fragile existence?

Luckily, Elon Musk is one step ahead and last year outlined his ambition to send humans to Mars as a “backup drive” for civilisation. Now, the billionaire entrepreneur has provided further details of his vision to make humans a multi-planetary species in a breezy paper, published in the appropriately-titled journal New Space.

The paper outlines early designs of the gigantic spacecraft, designed to carry 100 passengers, that he hopes to construct.

“The thrust level is enormous,” the paper states. “We are talking about a lift-off thrust of 13,000 tons, so it will be quite tectonic when it takes off.”

Creating a fully self-sustained civilisation of around one million people – the ultimate goal – would take 40–100 years according to the plans. Before full colonisation takes place, though, Musk needs to entice the first pioneers to pave the way.

The current situation is summed up in a Venn diagram showing two non-intersecting circles representing, on one side, the kind of people who would be up for getting on the Mars rocket and, on the other, those who could afford this kind of adventure. An optimistic estimate of the current cost is put at $10bn per person.

“What we need to do is to move those circles together,” Musk explains. If the mission cost could be dropped to the cost of an average US house price, he predicts, people would start to sign up in big enough numbers to kick off project multi-planetary civilisation. “Given that Mars would have a labor shortage for a long time, jobs would not be in short supply,” he points out.

Throughout, the paper strikes a buoyant, even jocular tone and doesn’t get excessively bogged down in technical detail. One section entitled “Why Mars”, spells out that red planet is essentially the best of a bad lot. “Venus is a high-pressure – super-high-pressure – hot acid bath ... not at all like the goddess,” Musk writes. “So, it would be really difficult to make things work on Venus.”

The moon is dismissed for being too small for the overarching vision: “I actually have nothing against going to the moon, but I think it is challenging to become multi-planetary on the moon because it is much smaller than a planet.”

“It would be quite fun to be on Mars because you would have gravity that is about 37% of that of Earth, so you would be able to lift heavy things and bound around,” he adds, predicting that journey times could eventually be cut to 30 days.



The spaceship’s design is summed up as: “In some ways, it is not that complicated,” which critics might point out runs contrary to the reputation of this field of science.

Financially, there are some challenges ahead, the paper acknowledges: “We have to figure out how to improve the cost of trips to Mars by five million percent”.

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However, Musk has some ideas for how such tremendous savings might be achieved. Reusing rockets could reduce the cost of spaceflight one thousandfold and refilling fuel in orbit rather than landing could make considerable savings too.

Space scientists remain sceptical about the vision, however.

In a recent interview, Ellen Stofan, former Nasa chief scientist, dismissed the idea that there would ever be a mass transfer of humans to another planet, adding that trumpeting the idea risked being a distraction from the problems faced on our home planet. “I don’t see a mass transfer of humanity to Mars, ever,” she said. “Job one is to keep this planet habitable ... There isn’t a planet B.”

Commenting on Twitter, Mark McCaughrean, senior advisor for science and exploration at the European Space Agency, struck a combative tone. “It’s a wild-eyed investment pitch, pumped up by the enthusiasm of credulous fanboys brought up on comic book sci-fi, wrapped in evangelism of saving humanity from itself and the problems we’ve wrought on this planet, a kind of modern day manifest destiny,” he tweeted in response to the paper.

“I’m less concerned about making humans a multi-planetary species than I am about making the Earth a sustainable multi-species planet, before we go gadding off colonising the solar system,” he added.

Facebook Twitter Pinterest An “intentionally fuzzy” timeline for the next steps in the SpaceX Mars programme. Photograph: SpaceX/Elon Musk

Prof Andrew Coates, who works on the ExoMars rover at University College London’s Mullard Space Science Laboratory, said that the question of whether present or past life existed on Mars needed to be answered before a manned mission, which could contaminate the surface, could be considered. “There’s a moral imperative to keep Mars as it is for the moment. Until we’ve conclusively answered that question we should keep our feet on the ground ... going there would be cosmic vandalism.”

And what is the timescale for the project? Musk states that he is being “intentionally fuzzy” about when the vision might become a reality, though one slide specified the first flights could start as early as 2023. “If things go super-well, it might be in the 10-year timeframe, but I do not want to say that is when it will occur,” the paper said.