While NASA has officially given up its plans to send humans back to the surface of the moon anytime soon, a contractor is proposing a mission to send a crew to a stationary spot in orbit over the far side of Earth's neighbor.
Lockheed Martin has begun pitching an L2-Farside Mission using its Orion spacecraft under development. [Illustration of the L-2 Farside Mission]
The company says such an endeavor could sharpen skills and technologies needed for a trip to an asteroid ? as well as showcase techniques useful for exploring Mars by teleoperation as astronauts orbit the red planet. Both are stated goals under the new direction for NASA outlined by President Obama.
Last February, the White House issued its proposed NASA budget that aced out former President George W. Bush's Constellation program. That plan had benchmarked 2020 as the date to replant the feet of U.S. astronauts on the moon after the last set of moonwalkers departed the landscape back in 1972.
Instead, President Obama laid out the goal of sending astronauts beyond the moon and into deep space. He aimed to land people on an asteroid for the first time in history by 2025, and send a crew to Mars by the mid-2030s.
Lunar halo orbit
Space planners at Lockheed Martin Space Systems in Denver proposed using their Orion capsule to support an L2 farside moon mission ? one that allows an astronaut crew to have continuous line-of-sight visibility to both the entire far side of the moon and Earth.
The crewmembers aboard NASA's Apollo 8 mission in 1968 were the first to set human eyes on that hidden real estate permanently turned away from the Earth.
The Earth-moon L2 Lagrange point is where the combined gravity of the Earth and the moon allows a spacecraft to hover over one spot and be synchronized with the moon in its orbit around the Earth.
From a halo orbit around that L2 point, a crew would control robots on the lunar surface. Teleoperated science tasks include snagging rock specimens for return to Earth from the moon's South Pole-Aitken basin ? one of the largest, deepest, and oldest craters in the solar system ? as well as deploy a radio telescope array on the farside. [Graphic: The moon's far side explained]
"We have come up with a sequence of missions that we've named 'Stepping Stones,' which begins with flights in low Earth orbit and incrementally builds towards a human mission to the moons of Mars in the 2030s," said Josh Hopkins of Lockheed Martin's Human Spaceflight Advanced Programs department.
The first Orion missions to the moon's far side, viewed as feasible by 2016 to 2018, would accomplish science goals on the lunar surface using robotic rovers controlled by astronauts in space "as practice for doing the same thing at Mars," Hopkins told SPACE.com.
Hopkins said that the L2 missions would also be a "shakedown cruise" to practice medium duration missions and the higher-speed reentry needed for exploration missions before the next step - missions to asteroids. Those in turn, he added, demonstrate additional capabilities for longer and more distant exploration before the Mars orbit mission.
According to a Lockheed Martin white paper on the proposed concept, a number of benefits stem from such a mission:
- Astronauts on an L2-Farside mission would travel 15 percent farther from Earth than the Apollo astronauts did - and spend almost three times longer in deep space.
- Each flight would prove out the Orion capsule's life support systems for one-month duration missions before attempting a six-month-long asteroid mission.
- It would demonstrate the high speed reentry capability needed for return from the moon or deep space ? 40 percent to 50 percent faster than reentry from low-Earth orbit.
- The mission would measure astronauts' radiation dose from cosmic rays and solar flares to verify that Orion provides sufficient protection, as it is designed to do. Currently the medical effects of deep space radiation are not well understood, so a one-month mission would improve our understanding without exposing astronauts to excessive risk.
As scripted by mission designers at the aerospace firm, the mission plan is straightforward, performed using new or existing rockets and a configuration of Orion designed for lunar missions.
To land unmanned spacecraft on the surface of the moon's farside, NASA would have to develop a new moon lander, since plans for the Altair human moon lander under the Constellation program were axed.
The robotic lander and rover would be launched first on a slow but efficient trajectory to the moon, to ensure that the rover is on its way before risking the crew launch.
Next, three astronauts would be launched in an Orion spacecraft. If NASA has built a heavy lift launch vehicle by then, it would be capable of launching the crew directly to the moon.
If that mega-booster is a no-show, smaller rockets can be used instead, but a more complex arrangement would be required.
First, Orion would be launched to low-Earth orbit on a rocket such as a Delta 4 Heavy. Then, a modified Centaur upper stage would launch on a separate rocket. Orion would dock to the Centaur stage in orbit, and the Centaur would boost Orion toward the moon.
Using either launch method, Orion would fly past the moon for a gravity slingshot maneuver toward the L2 point. Orion would use its propulsion system to enter a halo orbit around the L2 point.
Once at this vantage point ? 40,000 miles above the far side of the moon ? the Orion crew would be able to see both the entire far side of the moon, and the Earth.
From this unique slot in space, astronauts would control robots to perform various lunar duties. Astronauts would orbit the L2 point for about two weeks ? long enough to operate a rover through the full length of a lunar day.
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Leonard David has been reporting on the space industry for more than five decades. He is past editor-in-chief of the National Space Society's Ad Astra and Space World magazines and has written for SPACE.com since 1999.