Focusing on the short term

There are three big reasons NASA can't lay out a comprehensive Mars plan: flat budgets, a perilous political landscape, and the sheer scale of a 20-plus-years program. Thus far, NASA's most audacious human exploration program kicked off in 1961, when John F. Kennedy declared Americans would walk on the moon by the end of the decade. The nine-year program was a success, but it was bolstered by a strong political mandate and more than double the funding NASA receives today. The agency's budget peaked in 1966 at $43.5 billion (in 2014 dollars). Today, NASA gets about $18 billion. There's not much political will to go to Mars, and no indication that NASA's budget will change significantly. In fact, NASA doesn't even have a fiscal year 2015 budget yet, as it operates under a stopgap continuing resolution.

So NASA has less than half the money to execute a program that is twice as ambitious and will take twice as long. Nevertheless, they'll need a methodical, step-by-step approach like the one used in the 1960s with Mercury, Gemini and Apollo. Furthermore, officials like Gerstenmaier want to avoid Apollo-style one-and-done Mars visits. They'd rather see NASA establish a sustainable, long term presence in deep space. "The intent is not a single Mars mission," Gerstenmaier said, "but to put in place an infrastructure where we can eventually do repeat Mars missions."

To do this, Gerstenmaier and NASA focus on short-term missions they believe will develop the technologies and techniques needed to put humans on Mars. The current political and budgetary environment makes it impossible to say what a mid-30s Neil Armstrong-esque moment might look like. What NASA does know is that any Armstrong wannabes will need big rockets, advanced in-space propulsion, practice working in deep space, radiation protection, advanced habitats, and up to 20 tons of cargo waiting for them on Mars. With this in mind, seemingly unfocused programs like the Space Launch System and Asteroid Redirect Mission start to make a little more sense. While they may look like publicity stunts or knee-jerk reactions to politicians with constituents in space districts, they are actually NASA's way of getting the horse ready to pull the cart.

Beyond Earth orbit

NASA's journey to Mars begins in the place humans have continually lived since 2000: the International Space Station. Here, in low-Earth orbit, the agency is testing technologies that will be used on future Mars missions. One such advancement is 3D printing, which allows astronauts to swap out heavy toolkits for containers of reusable powder. These printers create specialized, one-off tools that can be grinded back out of existence. During an Oct. 27 panel discussion at NASA Marshall, Niki Werkeiser, the project manager for the station's 3-D printer, said NASA intends to scale up the technology so that lunar and Martian regolith can be used for feedstock. This would drastically reduce the amount of mass that has to be carried to a planetary surface. "We're looking at large-scale printers to be able to print things such as small habitat structures, radiation shielding, storage shelters and landing pads," she said.

Another low-Earth orbit technology demo happens next year, when private company Bigelow Aerospace is scheduled to connect an inflatable habitat to the station. Gerstenmaier said NASA will test how well the habitat shields occupants from radiation. Also in 2015, NASA astronaut Scott Kelly and cosmonaut Mikhail Kornienko will spend a full year aboard ISS to further quantify how long-term weightlessness affects the human body.

The real proving ground for Mars, though, is near the moon. It is there that NASA plans to spend a large part of the 20s, learning how to live and work in lunar Distant Retrograde Orbit, or DRO. Lunar DRO is a highly stable orbit where objects can remain steady for about a hundred years. At a June 19 briefing, Asteroid Redirect Mission Program Director Michelle Gates said NASA is currently interested in a lunar DRO with an altitude of about 75,000 kilometers. That's almost a fifth of the distance between the Earth and moon—a unique orbit unlike any humans have ever visited.

For NASA, lunar DRO is intriguing for several reasons. First of all, it offers a low delta-v transfer capability, meaning it's a place where spacecraft can enter and exit the Earth-moon system without using a lot of propellant. NASA plans to establish a permanent habitat here to serve as a waypoint for Mars-bound missions.

Secondly, establishing a presence in lunar DRO is a challenging but attainable milestone. It requires NASA to master deep space rendezvous and construction techniques. Astronauts living here would be far more independent than they are in low-Earth orbit—but close enough to home to bail out in an emergency. Such a quick return would come courtesy of NASA's new Orion capsule, designed with these scenarios in mind. Orion is more robust than any capsule operating today, said Mark Geyer, the vehicle's program manager, speaking to reporters at NASA Marshall. "When you're at the moon, you're somewhere between five and eleven days away from home," he said. "Orion is built to support the crew in their seats, in their suits, in a depressurized cabin, for up to six days. So it won't be a nice ride, but they'll be safe. That's the kind of stuff you have to think about when you're a long way from home."