This is part of IEEE Spectrum's Special Report: Why Mars? Why Now?
Many people believe that a manned mission to Mars is a venture best left to the next generation. They’re wrong. We have in hand all the required technologies; we don’t need to build giant spaceships, a lunar base, or a space station grander than the one we have. Instead, we can go straight to Mars in relatively small spacecraft powered by boosters like those that carried Apollo astronauts to the moon 40 years ago.
With this ”Mars Direct” approach, traveling light and living off the land whenever possible, humans could reach the Red Planet within a decade. Here’s how it might work.
In the spring of 2014, a heavy-lift booster similar to Apollo’s Saturn V launches from Cape Canaveral and uses its upper stage to throw an unmanned payload weighing 40 metric tons onto a trajectory to Mars. The payload includes an Earth return vehicle (ERV) that will eventually bring a human crew home; it’s carried to Mars with its two methane-oxygen propulsion stages empty. Also on board are 6 metric tons of liquid hydrogen, a 100-kilowatt nuclear reactor mounted in the back of a truck that is also fueled by methane and oxygen, a set of compressors, an automated chemical-processing unit, and a few scientific rovers.
Arriving at Mars eight months later, the payload uses atmospheric friction to brake its way into orbit and then lands with the help of a parachute. Next, the rovers explore and characterize the landing site while a human operator back on Earth telerobotically drives the truck a few hundred meters and then deploys the reactor, which powers the chemical-processing unit and the compressors. The chemical-processing unit begins to create a reaction between the bottled hydrogen brought from Earth and the Martian atmosphere, which consists largely of carbon dioxide, to produce methane and water. It electrolyzes the water, producing oxygen and hydrogen, and the compressors liquefy the methane and the oxygen, which are stored in the propellant tank of the ERV. The hydrogen, meanwhile, is recycled to produce more methane. Still more oxygen is produced by dissociating carbon dioxide in what’s called a reverse water-gas-shift reactor; some of that oxygen will go into the ERV’s tanks, and the rest will be stockpiled, both for breathing and for synthesizing water later on.