Applications close at the end of the month for a new group of astronauts to fly the Orion capsule beyond the space station to the Moon, Mars and points in between.

So far more than 1,300 would-be space travelers have applied for the job, hoping that Orion will become the ultimate enabling technology for deep-space human exploration. The figure is comparable to the response NASA received from its calls for space shuttle crews.

Like everyone who has flown in space, the Orion applicants are risk-takers, willing to gamble their lives for a plunge into the unknown. And at this point, the unknown includes specific target destinations for the craft that NASA engineers call the “multi-purpose crew vehicle, or MPCV.” While President Barack Obama has set a goal of sending humans to an asteroid by 2025, that is only one possible destination for Orion.

John Shannon, the last space shuttle program manager at NASA, has been on special assignment reviewing architectures for future human exploration for the past few months, and has started internal briefings on the options. Under the present state of play in U.S. space policy, Orion is almost certain to be the crew-transport element in any of them.

“If you step back and think of what we're doing, we're looking at a capability—both SLS [the heavy-lift Space Launch System] and MPCV/Orion—that can support multiple destinations,” says William Gerstenmaier, associate administrator for human exploration and operations. “So instead of optimizing or building a vehicle that just supports one particular mission, we're trying to look at a vehicle that has enough flexibility without carrying a huge penalty for that flexibility, that can support multiple missions and multiple destinations.”

Inside NASA, Gerstenmaier and other top managers are giving serious consideration to pulling modules from the International Space Station (ISS) when it is retired after 2020 and moving them to one of the Earth-Moon Lagrange points or to lunar orbit as an early destination for Orion. The idea has some international support as the ISS partnership begins to consider post-station human spaceflight (AW&ST Oct. 10, 2011, p. 46).

The first Orion flight on an SLS—tentatively set for 2017—probably will go around the Moon, and the first flight with a crew—in 2021 under current plans—may follow suit. It is also possible that the capsule will dock with the ISS, as a backup crew-transport vehicle to the private spacecraft under development.

Lockheed Martin, selected as the prime contractor on Orion in 2006, has been working on possible human missions with the capsule since 2007 and is looking for things to do with it on top of the original “back-to-the-Moon” plan.

“We basically were looking for other useful, productive ways to use Orion to explore that wouldn't cost a lot,” says Josh Hopkins, Lockheed Martin's space exploration architect, who helped draft a “stepping-stones” concept growing out of that work.

Among productive human missions that could be enabled by Orion is a 35-day trip to the Moon's far side, where the capsule would go into a halo orbit around the L2 Lagrange point. Aside from giving crews longer-duration experience beyond low Earth orbit, a far-side flight could perform useful science by serving as a platform for deploying a low-frequency radio telescope on the surface, or for operating rovers to retrieve samples from the ancient Aitken Basin. The latter would guide development of similar techniques for exploration at Mars, while the former would take advantage of the radio silence on the other side of the Moon to peer into the “cosmic dark ages” after the Big Bang.

“If you could put a low-frequency radio telescope on the far side of the Moon, you'd be able to observe the structure of the hydrogen gas in the universe before the stars lit up, so you could understand how it was that this relatively uniform Big Bang ended up resulting in this non-uniform distribution of clumps of matter in galaxies and stars,” Hopkins says. “So it's a pretty interesting question for cosmologists, that as far as they can tell can only be answered by building a radio telescope on the far side.”

As crews accumulate time at L2, NASA could begin interspersing longer missions to asteroids. Lockheed Martin has identified a 195-day mission to the asteroid 2008 EA9, about 12 million km (7.5 million mi.) from Earth, and a 450-day mission to 2000 SG334, at a distance of 8 million km. NASA could also conduct experiments with artificial gravity for eventual flights deeper into space, spinning an Orion tethered to a counterweight to keep the crew healthy.

For those longer-duration missions, NASA would “definitely” need a habitat module that the crew could reach through the docking port at the top of Orion. Shorter missions, like those to the Moon, could be accommodated in the capsule's 21-day baseline by shrinking the crew size to three or even two from four.

While Mars is considered the ultimate goal, Hopkins says an intermediate mission to Deimos could be another important step along the way.

Measuring only 15 X 12.2 X 10.4 km, and more distant from the planet than the larger moon Phobos, Deimos is easier to reach from Earth and has a couple of spots at the equivalent of its north and south arctic circles that receive 10 months of continuous sunlight for solar power.

“[Deimos] has very little gravity; it has some, but I think something like 5 meters/sec. is the escape velocity, so you could land a spacecraft and take off again using the equivalent of RCS [reaction control system] thrusters,” says Hopkins. “So we've debated, do we call it a lander, or is it just a habitat that happens to be able to land? You do have to have footpads and anchors, and you have to have thrusters in the right place, and you have to design it to interact with the dust on the surface, but it's not a lander in the sense that we normally think of.”

In a notional 900-day mission, a crew would land at the southern site for four months, then go into orbit for 50 days, and then land at the northern site for a 10-month stay before returning to Earth. While at the tiny moon, they could operate rovers on the planet's surface, perhaps to collect samples. Hopkins and his colleague William Pratt calculate that a good time for the mission would be 2033-35, which coincides with a planetary alignment that offers the most protection from galactic cosmic rays.

“We don't look at these first missions as going to a Lagrange point to get your passport stamped,” Hopkins says. “There are some really interesting fundamental science questions about the formation of the Solar System or the universe that you can accomplish.”