Sen— The USA's present roadmap to space for humans includes a return to the Moon, a visit to an asteroid and eventually a landing on Mars.
But a free-thinking group of space scientists have proposed a novel alternative early mission to NASA - a journey to a region of space beyond the far side of the Moon.
Their concept would involve flying the agency's planned new Orion space capsule to a spot known as the lunar L2 (Lagrange) point - a location where the combined gravity of the Earth and Moon allows a spacecraft to sit permanently above the lunar far side.
Though this so-called L2 halo orbit means they would not visit the Moon's surface, the mission would be a testing ground for NASA to discover more about long-duration missions away from Earth before astronauts venture further into deep space.
Such a mission would take Orion's astronauts 65,000 km beyond the Moon - 15 per cent further away from Earth than the Apollo crews journeyed - and they would spend nearly three times longer in space than the later 12 day Apollo missions.
They would be able to test operational spaceflight capabilities such as life support, communication, high speed re-entry, and radiation protection. But the mission plan also envisages the astronauts controlling robotic explorers on the lunar far side which has never been visited by a lander.
Because the Moon is tidally locked in its orbit around the Earth, it always presents the same face towards us. (A slight rocking, called libration, actually allows us to see close to 60 per cent of the Moon's surface over time). Most of the far side is permanently hidden.
The Lunar L2-Farside Exploration and Science Mission Concept has been proposed by a team led by Jack Burns of NASA's Lunar Science Institute in Moffet Field, California. The report's authors comment: "Such telerobotic oversight would also demonstrate capability for human and robotic cooperation on future, more complex deep space missions such as exploring Mars."
Their proposal would see a robotic lander and rover launched first on a slow trajectory to the Moon known as ballistic lunar transfer. Three astronauts would then be launched in an Orion spacecraft using NASA’s heavy-lift Space Launch System (SLS).
The spacecraft would fly past the Moon for a gravity slingshot manoeuvre towards the L2 point where Orion would use its propulsion system to enter a halo orbit. From this point, the spacecraft would enjoy continuous line-of-sight links with both the lunar far side and the Earth, say the mission's designers.
And because their radio commands would take less than half a second to reach the Moon, compared to about 1.3 seconds from Earth to the Moon, it would be easier to control the robots in real time as they performed tasks such as probing for water ice in the Schrödinger crater that lies within the South Pole-Aitken basin.
Schrödinger basin from Japan's orbiting Kaguya moon probe. Credit: JAXA
Basins are impact craters with diameters greater than 300 km. They are seen as suitable for landers because they have broad flat floors. The mission proposers say that Schrödinger basin is the best preserved impact basin of its size on the Moon and provides tremendous science and exploration opportunities, safe landing zones, and a landscape that could be navigated by robotic rovers.
Other scientific projects that could be overseen by the astronauts would be a robotic sample return mission to bring lunar rock from the far side back to Earth, plus the installation of a radio telescope shielded from interference from Earth that could study faint signals from the dawn of the Universe.
The first Exploration Flight Test of Orion is scheduled for 2014 to verify that the crew module can survive high-speed reentry into the Earth’s atmosphere from a lunar return trajectory.
Three additional test flights are planned for the spacecraft including an unmanned flight around the Moon in 2017, and a crewed flight soon after that.