Orlando Sentinel: NASA Considering L2 Spaceport As Beyond-LEO Destination
The Orlando Sentinel reports that NASA is considering a new idea for the next human spaceflight destination -- a "gateway spacecraft" at the Earth-Moon L2 Lagrange point. Under current presidential policy, the agency is focused on sending astronauts to an asteroid by 2025 as the next step in human spaceflight beyond low Earth orbit (LEO).
The newspaper's description of the proposal, which it says was briefed to the White House earlier this month by NASA Administrator Charlie Bolden, suggests that it would be a smaller version of concepts proposed decades ago. The idea is essentially to have a space station at an Earth-Moon Lagrange point whose purpose is to serve as a transportation hub to other solar system destinations.
The Earth-Moon L2 Lagrange point is on the other side of the Moon, that is, further from the Earth than the Moon itself.
There are five points in any two-body system where the gravitational forces are in equilibrium; three are unstable (L1, L2 and L3) and two are stable (L4 and L5). Also called libration points, they were defined by the French-Italian mathematician Joseph-Louis Lagrange. Putting an object at one of these points reduces the need for fuel to keep it in position. The European Space Agency (ESA) and NASA have descriptions of Lagrange points on their websites that are very useful in explaining these difficult to visualize locations.
NASA and ESA have made good use of the Sun-Earth L1 and L2 Lagrange points already. Sun-Earth L1 is the place for spacecraft that study the Sun and provide early warning of bursts of solar particles heading to Earth that could disrupt communications or endanger International Space Station crews. The Sun-Earth L2 point is good for astrophysics and is the home of NASA's WMAP spacecraft and ESA's Herschel and Planck. It also will be the location of the James Webb Space Telescope (JWST).
NASA's ARTEMIS spacecraft are the first to be placed in the Earth-Moon L1 and L2 Lagrange points. These two spacecraft, P1 and P2, were part of another NASA satellite constellation, THEMIS, that were repurposed to investigate those two Earth-Moon Lagrange points.
According to the Sentinel, NASA is now thinking of using the Earth-Moon L2 point for an outpost that would "support a small astronaut crew and function as a staging area for future missions to the Moon and Mars." The newspaper says the cost of such a mission is not mentioned in the NASA plannning documents it reviewed. Those documents reportedly say it could be built with "only 'modest increases'" to the NASA budget.
The idea of using Earth-Moon Lagrange points for space stations/transportation hubs is hardly new. Gerard O'Neill popularized the idea of a very large space station -- a "colony" -- at the Earth-Moon L5 point in the 1970s and 1980s. He was one of the members of the 1985-1986 National Commission on Space (NCOS), chaired by former NASA Administrator Thomas Paine, that adopted the notion of Earth-Moon Lagrange-point space stations (not necessarily at L5) as part of a much bolder "Bridge Between Worlds" -- a transportation system between cis-lunar space and Mars that would make such trips routine rather than individual "flag planting" missions.
More recently, the 2009 Augustine Committee report on the future of the human spaceflight program included Lagrange points as possible destinations in its "flexible path" category that also includes asteroids. On April 15, 2010, President Obama announced that he had decided that the next destination for human spaceflight beyond LEO should be an asteroid, but a consensus has not developed to support that policy. Last month in an Internet chat, he referred to it as a "potential" mission, which could suggest that he may be having second thoughts.
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