This story was updated at 12:26 p.m. ET, Jan. 19.
It's been nearly 40 years since people last set foot on the moon, but momentum is building for a return to Earth's nearest neighbor — and for the establishment of a permanent manned presence on lunar soil.
But if we do set up lunar bases, what will they look like? How will they function? NASA scientists have been working on these questions, as have folks in the private sector who see loads of money to be made on the moon's frigid surface.
Suffice it to say that any future operation would look very different than past lunar missions. After all, the first humans to walk on the moon — Apollo 11 astronauts Neil Armstrong and Buzz Aldrin — spent only 21 hours on the lunar surface in July 1969. The last people on the moon — Apollo 17’s Eugene Cernan and Harrison Schmidt — stayed for just over three days in 1972.
NASA's vision: Mobile robot convoys
With the cancellation of the moon-bound Constellation program last year, NASA's focus has shifted away from returning to the moon and toward visiting asteroids and Mars.
The idea is to send bots and astronauts up together — at first, likely to Shackleton crater near the moon's south pole, said Matt Leonard, deputy project manager for lunar surface systems at NASA's Johnson Space Center in Houston.
Getting to the poles requires less fuel than other moon destinations, Leonard said, and the area in and around Shackleton — a 12-mile-wide (20-kilometer-wide) crater whose floor is in perpetual shadow — looks to have lots of water ice.
The first few human crews would stick around for a week, then a few weeks, then a month — gradually building a presence at Shackleton, performing research and gaining knowledge about how to live and work on the moon, Leonard said.
The robots that would assist these crews would likely include the 176-pound (80-kilogram) K10 scouting rover, along with the All-Terrain, Hex-Limbed, Extra-Terrestrial Explorer (ATHLETE) — a six-legged, heavy-lift cargo carrier. The Space Exploration Vehicle (SEV), an updated version of Apollo's old "moon buggy," would also chip in.
"We might leave some science sensors behind, but for the most part we'd take everything with us," Leonard told SPACE.com. The ATHLETEs would carry big loads like the astronauts' living and working quarters, as well as heavy equipment.
About six months after the robotic convoy sets out, another astronaut crew would meet up with it at Malapert, and the cycle would begin again. Robots would move around the moon's southern half, doing scouting and scientific survey work for astronauts, who would rendezvous with them at various spots.
"We'd just keep kind of leapfrogging around to sites that are interesting," Leonard said. "We'd try to work ourselves up toward the equator."
NASA is also considering inflatable habitat modules, which would pack very tightly aboard a launch vehicle but expand greatly in space or on the lunar surface, potentially providing astronauts with much more room. The agency is planning to test a hybrid module — a rigid one with an inflatable structure atop it — this year at Desert RATS, its annual series of field trials in the Arizona desert, Leonard said.
"In the first eight years we'd bring all of our logistics with us that we would need," he said. "But we'd bring those production plants down with us right away. As soon as they're up and running, our logistics train is a lot smaller and we can do a lot more exploration."
"Obviously,nuclear would make you much less light-sensitive," Leonard said. "If we went in that direction, we might arrange our missions in a different way."
NASA's mobile bases would be research operations. But some people are looking to set up lunar outposts as a way to make money.
The Shackleton Energy Co., for example, wants to mine the moon's water ice and turn it into rocket fuel. Shackleton Energy Co. (SEC), which was formed in 2007, would sell the propellant from fueling stations in low-Earth orbit (LEO).
Because spaceships burn so much fuel just lifting off from Earth, letting them top up in orbit could spur a huge wave of travel and discovery in space, according to SEC founder Bill Stone. And it makes sense to supply the filling stations from the moon, since it's about 15 times cheaper to launch something to LEO from there than from Earth, Stone added.
"In our view, the moon is a stepping stone," Stone told SPACE.com. "What we extract from there will enable the exploration of the inner solar system."
SEC's mining bases would likely be at one or both lunar poles, in craters whose frigid depths have trapped lots of water over the past several billion years. Craters like Cabeus, perhaps, where water ice makes up 5.6 percent of the lunar dirt by weight.
Like NASA's outposts, SEC's bases would rely heavily on machines.
"This will be a man-tended, mostly robotic operation," Stone said.
The robots would include scouting rovers, likely developed using NASA's experience and technology as a guide, Stone said. Heavier machinery would perform the water-ice extraction, which would basically consist of heating, after which lunar soil would be put back in place.
"We have to have nuclear power," said SEC president Dale Tietz. Solar just won't cut it, since the company needs to work extensively in and around dark crater bottoms that can be as cold as minus 396 degrees Fahrenheit (minus 238 Celsius).
"By the end of the decade, there's a high likelihood we'll be up and running," Tietz told SPACE.com.
After piling some lunar dirt over the habitats — to protect against micrometeorite strikes, thermal extremes and radiation — clients could move into the ready-made moon base, using it for whatever they wished.
"We've had it partially designed for five or six years," said Robert Bigelow, the company's founder. "From all aspects, it looks very doable."
"We can use the moon as a pathfinder," Bigelow told SPACE.com. "It's the perfect ground to get our feet wet for Mars."
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