Human spaceflight is likely to remain in low Earth orbit (LEO) for the foreseeable future. The International Space Station and China's Tiangong-1 are the only destinations within reach, and a lot of effort will go into finding better ways to get there and meaningful research to conduct upon arrival.

But Mars is the ultimate destination for this generation of humanity. After a sometimes-brutal struggle over space-exploration resources following the global financial debacle of 2008, work continues at a reduced pace on at least some of the hardware that will be needed to get there. The first stage of NASA's heavy-lift Space Launch System (SLS) has just passed a significant milestone review of system requirements and design and production concepts. The J-2X engine that may someday power its upper stage is moving through ground testing at Stennis Space Center, where the engine's powerpack ran continuously for 19 min. 10 sec. in a June 8 test.

And the first flight version of the Orion multipurpose crew exploration vehicle has reached Kennedy Space Center, where Lockheed Martin workers will prepare it for a test in 2014 designed to bring it back into the atmosphere at speeds roughly 80% of those it would see on a return from the Moon. That unpiloted mission will take Orion well beyond the 220-mi. ISS altitude before it plunges home, into the cislunar space that may very well be the next area of operation for human explorers.

Mindful of the constrained funding they are likely to face for the foreseeable future, NASA managers are considering using a recycled ISS module as the basis for a way station at one of the Earth-Moon Lagrangian points, or perhaps in lunar orbit, to press exploration beyond LEO (AW&ST Oct. 10, 2011, p. 46). While there are problems with the orbital mechanics of the idea, the basic concept of cislunar operations is attractive.

John Karas, vice president and general manager of human spaceflight at Lockheed Martin Space Systems, is one advocate. An aggressive and articulate spokesman for his product, Karas sees Orion as the centerpiece for an “affordable” stepwise push to Mars that will start in cislunar space. The trick is in not trying to land.

Landers are big, heavy and expensive, but there are places near Mars—the two tiny moons—where a human crew could set up shop to explore the planet's surface using teleoperated robots without actually touching down there. And the L2 Earth-Moon Lagrange point over the lunar far side is a good place to practice for that, says Karas.

“Think of cislunar space as an analogy of what Gemini was to Apollo,” he says. “Gemini learned rendezvous/prox ops and this and that. Well, we're going to learn about closed-loop life support, low-g, how to navigate in low gravity fields, those kind of things.”

Some of that work—particularly low-gravity operations—can be done at a near-Earth object (NEO), which is President Barack Obama's stated human exploration goal in the 2020s. Astronomers have spotted NEO “targets of opportunity” that pass close enough to Earth's orbit in 2019, 2021 and 2024, Karas says, with more likely to be found as they draw more attention. A NEO mission using an SLS would take 180 days, with an Orion and a small habitat that could be made from two of the cylindrical sections that go into the Orion pressure vessel.

That same Orion/habitat stack could float in a halo orbit at L2 over the lunar far side while its crew operated robotic rovers on the unexplored surface below to gain experience for Mars (see illustration). Karas says Demos, the smaller of the Martian moons, could be a good choice for a human-exploration base because there is a spot on it that is always in view of Earth and Mars for communications, and the Sun for power. A larger hab could essentially be docked with the low-gravity surface for the 1.5-year stay while the two planets line up again for the return trip, and the crew could use the Orion to move around Demos in the low-gravity environment. The whole process would take six or seven 130-metric-ton SLSs to predeploy the habitat and return stage, and transport the crew there and back.

Karas argues the mission would be affordable, based on NASA funding history. Over the 30-year shuttle era, the U.S. averaged 4.5 missions a year. NASA already has spent more than $5 billion to develop Orion, and the SLS should be cheaper than a shuttle because it uses shuttle-heritage hardware in a simpler configuration.

“Do you think you could afford one or two heavies a year for a couple of years?” Karas asks. “I'm not talking lots and lots of elements like station, so even Mars is less aggressive than station in certain budgetary aspects, as long as you don't land.”