Beyond the Moon
It’s not a place, exactly. But it could be NASA’s next destination.
- By Guy Gugliotta
- Air & Space magazine, April 2013
The late summer of 2011 was an awkward moment for NASA’s 50-year-old spaceflight program. The space shuttle’s final mission had just ended, and construction of the International Space Station—the shuttle’s signature achievement—was complete.
A year earlier, President Obama had, to the dismay of Congress, cancelled the shuttle’s presumptive follow-on program: a return to the moon. “We can’t keep on doing the same old things,” Obama had said in a speech at Florida’s Kennedy Space Center. “We’ve been there before.”
Instead, he set a new goal—sending astronauts “beyond the moon,” to an asteroid by 2025, then on to orbit Mars by the mid-2030s. Critics who accuse NASA of having no destination for human spaceflight couldn’t be more wrong, according to the agency. “The ultimate destination is to send people to the surface of Mars,” says Doug Cooke, who in 2011 was NASA’s associate administrator for exploration systems (he is now an independent aerospace consultant). The choice of Mars is clear, in part, because anything more ambitious is simply beyond today’s technology. “That’s about as much as we know how to do,” says Cooke.
But as Cooke and everyone else in the NASA hierarchy well knew, we’re not ready for Mars. So the task in 2011 was to plan out the intermediate steps. NASA had been mulling an asteroid mission for years (see “The Million-Mile Mission,” June/July 2008), but as the studies got more detailed, difficulties arose. It became apparent that there were very few good targets to visit in the 2020s. NASA needed an asteroid that was both reachable and “interesting.” Interesting, in scientific parlance, meant “something big enough to have some diversity of features, at least 60 or 70 meters in any dimension,” says Cooke.
Reachable meant finding a target that NASA could handle with a short (months-long) trip, for not too much money. Traveling to an asteroid “can be as difficult as landing on Mars,” Cooke says, “and it’s comparable in transit times and what it implies for crew conditions and habitat.” Some targets would be easier to reach, but the pickier you get for scientific or logistical reasons, “the fewer asteroids there are to choose from.”
The plan had even bigger problems. Hardly anyone wanted to do it. A report by a National Research Council panel on NASA’s strategic direction last December was blunt by Washington standards: “The committee has seen little evidence that a current stated goal for NASA’s human spaceflight program—namely, to visit an asteroid by 2025—has been widely accepted as a compelling destination by NASA’s own workforce, by the nation as a whole, or by the international community.” Furthermore, even though the panel wasn’t asked to assess the plan’s technical feasibility, “it was informed by several briefers and sources that the current planned asteroid mission has significant shortcomings.”
Shelving the asteroid option would leave NASA’s new spaceship, Orion, and its planned shuttle-derived rocket, the Space Launch System, with nowhere to go, at least in the near term. By 2017, the SLS will be ready to launch an unmanned Orion—the shuttle’s successor—into Earth orbit on the spacecraft’s second test flight. Four years after that (the slow pace is dictated by NASA’s declining budget), astronauts plan to board Orion for the first time, to (perhaps) circle the moon and return. NASA could handle such a demo flight easily, Cooke says, but would prefer to try something “more meaningful.”
That more meaningful something emerged during 2011 in a proposal known as Gateway. The mission: Send astronauts to an empty spot in space, high above the lunar far side, where the gravitational pulls of Earth and of the moon are balanced. Such spots are called Lagrange points; the one in the Gateway proposal is Earth-moon Lagrange 2, or EML-2 (see “The Lagrange Points,” p. 27). Circling this spot in a “halo” orbit, an astronaut crew would remain effectively parked in zero gravity, flying in formation with the moon as it orbits Earth every 27.3 days.
At the L2 point, astronauts could learn to work in deep space. They could joystick a robotic rover to explore the craters, hills, and valleys of the lunar far side, 40,000 miles away. They could use the rover to deploy a sensitive radio telescope that would be shielded from terrestrial interference. Biologists could gather critical data on the dangers of galactic cosmic rays, which can increase the risk of cancer, to future deep space travelers. Eventually, the L2 point could serve as a staging site—a gateway—for missions to asteroids and to Mars.
Gateway’s primary advantage, though, may be economic and political. A mission to L2 would send astronauts farther than they’ve ever been, using hardware already under construction. No expensive landers or long-duration spacecraft would be required. Advocates say it would be a worthy interim goal—far enough to push astronauts and their technology, but, at least in theory, close enough to bring them home in case of emergency. It’s both challenging and possible. And, says John Logsdon, former director of the Space Policy Institute at George Washington University, Gateway’s “initial beauty is that it is a reachable destination that’s new.”
Although NASA has been studying Lagrange-point missions for at least a decade, the idea gained new momentum in August 2011, when William Gerstenmaier, NASA’s associate administrator for human exploration and operations, created a special working group to examine NASA’s human spaceflight options. Affordability was a primary requirement, and for space mission planners, a sure way to lower launch costs is to cut down on the consumable supplies, especially fuel, a crew needs to take along. A principal advantage of any Lagrange point is that once a spacecraft arrives, very little energy is required to keep it there. “I’m using the gravity properties to minimize the fuel requirements,” Gerstenmaier says.
The L2 point is about 15 percent farther than the Apollo astronauts traveled. The quickest way to get there—in only three to five days—is to use the Apollo approach: take aim and fire. This, however, requires extra fuel. So NASA would prefer to take a slower and more circuitous route, using a gravity assist from the moon to hurl Orion to its destination.