LONDON — Elon Musk, the billionaire founder and chief executive of the private spaceflight company Space Exploration Technologies (SpaceX), wants to help establish a Mars colony of up to 80,000 people by ferrying explorers there for perhaps $500,000 a trip.
In Musk’s vision, the ambitious Mars settlement program would start with a pioneering group of fewer than 10 people, who would journey to the red planet aboard a huge reusable rocket powered by liquid oxygen and methane.
“At Mars, you can start a self-sustaining civilization and grow it into something really big,” Musk said in a speech at the Royal Aeronautical Society here Nov. 16. Musk was here to talk about his business plans and receive a medal for his contribution to the commercialization of space.
Accompanying the founders of the new Mars colony would be large amounts of equipment, including machines to produce fertilizer, methane and oxygen from Mars’ atmospheric nitrogen and carbon dioxide and the planet’s subsurface water ice.
The pioneers would also take construction materials to build transparent domes, which when pressurized with Mars’ atmospheric carbon dioxide could grow Earth crops in martian soil. As the Mars colony became more self-sufficient, the big rocket would start to transport more people and fewer supplies and equipment.
Musk’s architecture for this human Mars exploration effort does not employ cyclers, reusable spacecraft that would travel back and forth constantly between Mars and Earth — at least not at first.
“Probably not a Mars cycler; the thing with the cyclers is, you need a lot of them,” Musk said in an interview. “You have to have propellant to keep things aligned as [Mars and Earth’s] orbits aren’t [always] in the same plane. In the beginning you won’t have cyclers.”
Musk also ruled out SpaceX’s Dragon capsule, which the company is developing to ferry astronauts to and from low Earth orbit, as the spacecraft that would land colonists on Mars. When asked what vehicle would be used, he said, “I think you just land the entire thing.”
Asked if the “entire thing” is the huge new reusable rocket — which is rumored to bear the acronymic name MCT, short for Mass Cargo Transport or Mars Colony Transport — Musk said, “Maybe.”
Musk has been thinking about what his colonist-carrying spacecraft would need, whatever it ends up being. He reckons the oxygen concentration inside should be 30 to 40 percent, and he envisions using the spacecraft’s liquid water store as a barrier between the Mars pioneers and the sun.
Musk’s $500,000 ticket price for a Mars trip was derived from what he thinks is affordable.
“The ticket price needs to be low enough that most people in advanced countries, in their mid-40s or something like that, could put together enough money to make the trip,” he said, comparing the purchase to buying a house in California.
He also estimated that of the 8 billion humans who will be living on Earth by the time the colony is possible, perhaps one in 100,000 would be prepared to go. That equates to potentially 80,000 emigrants.
Musk figures the colony program — which he wants to be a collaboration between government and private enterprise — would end up costing about $36 billion. He arrived at that number by estimating that a colony that costs 0.25 percent or 0.5 percent of a nation’s gross domestic product would be considered acceptable.
The U.S. gross domestic product in 2010 was $14.5 trillion; 0.25 percent of that is $36 billion. If all 80,000 colonists paid $500,000 per seat for their Mars trip, $40 billion would be raised.
“Some money has to be spent on establishing a base on Mars. It’s about getting the basic fundamentals in place,” Musk said. “That was true of the English colonies [in the Americas]; it took a significant expense to get things started. But once there are regular Mars flights, you can get the cost down to half a million dollars for someone to move to Mars. Then I think there are enough people who would buy that to have it be a reasonable business case.”
The fully reusable rocket that Musk wants to take colonists to Mars is an evolution of SpaceX’s Falcon 9 booster, which launches the Dragon cargo capsule that has flown twice to the international space station.
“It’s going to be much bigger [than Falcon 9], but I don’t think we’re quite ready to state the payload. We’ll speak about that next year,” Musk said, emphasizing that only fully reusable rockets and spacecraft would keep the ticket price for Mars migration as low as $500,000.
SpaceX is already testing what Musk calls a next-generation, reusable Falcon 9 rocket that can take off vertically and land vertically. The prototype, called Grasshopper, is a Falcon 9 first stage with landing legs.
Grasshopper has made two short flights. The first was Sept. 21 and reached a height of 2 meters; the second test, on Nov. 1, was to a height of 5.4 meters. A planned milestone for the Grasshopper project is to reach an altitude of 30 meters.
“Over the next few months, we’ll gradually increase the altitude and speed,” Musk said. “I do think there probably will be some craters along the way; we’ll be very lucky if there are no craters. Vertical landing is an extremely important breakthrough — extreme, rapid reusability. It’s as close to aircraft-like dispatch capability as one can achieve.”
Musk wants to have a reusable Falcon 9 first stage, which uses Grasshopper technology, come back from orbit in “the next year or two.” He then wants to use this vertical-landing technology for Falcon 9’s upper stage.
Musk hopes to have a fully reusable version of Falcon 9 in five or six years, but he acknowledged that those could be “famous last words.”
Another steppingstone toward the planned reusable Mars rocket is SpaceX’s Falcon Heavy launcher. With a first flight planned for next year from Vandenberg Air Force Base in California, the Heavy is a Falcon 9 that has two additional Falcon 9 first stages bolted on either side.
Musk expects the Falcon Heavy to launch from Florida’s Cape Canaveral Air Force Station eventually. This triple-first-stage rocket will be able to put 53,000 kilograms into a 200-kilometer low Earth orbit. But the Falcon Heavy is still much smaller than Musk’s envisioned fully reusable Mars rocket, which would also employ a new engine.
While Musk declines to state what the Mars rocket’s payload capability will be, he does say it will use a new staged combustion cycle engine called Raptor. The cycle involves two steps. Propellant — the fuel and oxidizer — is ignited in preburners to produce hot high-pressure gases that help pump propellant into the engine’s combustion chamber. The hot gases are then directed into the same chamber to aid in the combustion of the propellants.
Because Raptor is a staged combustion engine — like the main engines of NASA’s space shuttle fleet — it is expected to be far more efficient than the open-cycle Merlin engines used by the Falcon 9.
While the Falcon 9’s engines use liquid oxygen and kerosene, Raptor will use liquid oxygen and methane. Musk explained that “the energy cost of methane is the lowest, and it has a slight ISP [specific impulse] advantage over kerosene and doesn’t have any of the bad aspects of hydrogen.” Hydrogen is difficult to store at cryogenic temperatures, makes metal brittle and is very flammable.
