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As early as 2005, when Earth and Mars are in their once-every-26-months alignment, the plan envisions launching a four-person spacecraft to Mars--but launching it with its tanks empty of fuel and its cabin empty of crew. Landing on the surface, the craft would begin pumping Martian atmosphere--which is 95% carbon dioxide--into a reaction chamber, where it would be exposed to hydrogen and broken down into methane, water and oxygen. Methane and oxygen make a first-rate rocket fuel; water and oxygen are necessary human fuels. All these consumables could be pumped into tanks inside the ship and stored there.
Two years later, when Mars and Earth are again in conjunction, another spacecraft--this one carrying a crew--would be sent to join the robot ship on the surface. The astronauts could work on Mars for 18 months, living principally in their arrival craft, and then, at the end of their stay, abandon that ship, climb into the robot craft and blast off for home. "Fly several of these missions," says Robert Zubrin, author of the book The Case for Mars and one of the engineers who developed the plan, "and you leave the surface scattered with a series of warming huts that serve as the beginnings of a base."
What makes the Mars Direct plan remarkable is how unremarkable the science behind it is. The spacecraft in which the astronauts will live are descendants of the same pressurized vessels NASA has been building since the Mercury days. The boosters that will lift the ships off the ground are reconfigured engines cannibalized from the shuttle. The technology needed to distill the Martian atmosphere is the stuff of first-year chemistry texts. For this reason, Zubrin believes, Mars Direct could be surprisingly affordable: about $40 billion for five missions, or less than half the cost of the Apollo program in today's dollars.
But is traveling to Mars on the cheap the best way to go? As the recent failures of NASA's unmanned Mars probes suggest, makeshift machines built with off-the-shelf parts may save money, but when it comes time to fly, they often fall short. At the Johnson Space Center, engineers are thus looking at other Mars scenarios that still include frugal, on-site fuel manufacturing but also call for six-person crews, bigger vehicles and Apollo-style motherships in Martian orbit. "We're trying to take the best ideas and fold them into a reasonable approach," says Drake.
Whichever approach is chosen, what all of them have in common is the speed with which they could be pulled off. Unlike the early Apollo planners, who weren't even sure they could get astronauts into near-Earth space, much less fling them out to the moon, Mars-mission directors have the basic space-travel technology down cold. All they need is the go-ahead to design and build their machines.