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; in this case, the Earth-moon Lagrange 2. 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.
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, the mission’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.
“That is a trick that NASA has been using in robotic missions for the last 40 years, but it would be the first time for human spaceflight,” says NLSI’s scientist Jack Burns, director of the NASA-funded University of Colorado space Lunar University Network for Astrophysics Research, who has been studying options for L2 missions. “We’re talking a week to get to L2 because of the gravity assist and the resulting trajectory.”
Read the full story at AirSpaceMag.com
Posted by: Soderman/NLSI Staff
Source: Jack Burns; http://www.airspacemag.com/space-exploration/Beyond-the-Moon-198839211.html?c=y&story=fullstory#