Thanks to the Google Lunar XPrize competition, humans are sending not one but multiple probes to the moon. But the scientists are not your usual space explorers.
The moon. We humans left flags, footprints and three moon buggies on it, but stopped going there after the Soviet Union's Luna 24 mission in 1976. Until late 2013, when China's lander Chang'e 3 and its companion the Yutu rover (also known as Jade Rabbit) arrived.
Soon, Earth may send a stream of robotic probes to the moon, as a new race to our 'eighth continent' is heating up. This time, though, the running will not be made by government-led agencies like Nasa and Esa. Instead, private companies are leading the way, with tech giant Google providing the incentives. Spurring inventors from around the world is a $30m reward, the Google Lunar XPrize. The mission: to successfully deploy a robotic craft on the lunar surface, make it move at least 500 metres, and send high-definition 'mooncasts' back to Earth.
Five of 16 teams in the race – Astrobotic (US), Hakuto (Japan), Moon Express (US), Part-Time Scientists (Germany), and Team Indus (India) – recently received a boost from Google in the form of so-called Millennium prizes worth a combined $5.25m.
Promising the moon
The Lunar XPrize may not quite spark the same excitement as the Apollo 11 landings in 1969. But this privately-funded race to the moon may make space exploration cheaper and help to create the Apollo moment for the current generation,' says Chanda Gonzales, senior director of Google Lunar XPrize.
In the long term, says Becker, 'the moon could be our stepping stone' to boldly go where no man has gone before.
Here is a preview of some of the technologies that may take humankind's new envoys back to the moon.
The first challenge is actually getting to the moon.
Team Indus wants to use the Indian Space Research Organization's Polar Satellite Launch Vehicle (PSLV).
Astrobotic, meanwhile, hopes to hitch a ride on the commercial SpaceX Falcon 9 rocket. After reaching low Earth orbit, the Falcon 9's second stage would re-ignite for trans-lunar injection, propelling the spacecraft on a 4.5-day cruise to the moon.
Part-Time Scientists plan to use the DNEPR rocket, a former intercontinental missile from the Russians. Meanwhile, the Moon Express team is working on its doughnut-shaped MX-1 spacecraft, which will rely on solar energy for power and hydrogen peroxide as rocket fuel. It will launch as a secondary payload aboard a rocket like the Falcon 9. Once deployed in Earth orbit, the MX-1 can make to to the Moon and land by itself without assistance from any other rocket stages.
Landing softly is probably the trickiest part of the venture, not least because of the lack of atmosphere, which rules out the use of a parachute.
Team Indus is building a four-legged lander called HHK, similar to the landers used by the Apollo programme and by China's Chang'e. The lander would switch off all thrusters about 5 metres above the surface and fall down freely. The landing gear has a primary leg made of a metallic crush material that absorbs energy at touchdown, and two secondary legs for lateral stiffness.
Astrobotic's Griffin Lander will carry the team's own rover and two rovers from the Hakuto team. To land, Griffin will use a visual guidance system to process surface pictures in real time and compare them to on-board maps, to determine its exact position. "On approach to the intended landing site, the system scans the ground to detect and avoid obstacles, ensuring a safe touchdown," says John Thornton, Astrobotic's chief executive.
Moon Express hopes that its MX-1 will not only travel to the moon but land on it, too. The craft will rely on "onboard intelligence to guide it to its landing," says the company's co-founder and CEO Bob Richards. MX-1 won't have legs - it will land softly on one of its empty fuel tanks, which will collapse to cushion the impact.
Communications between ground control and the moon will be crucial for the success of any mission. The craft will send back data, video and still images, using a radio link for communication. It takes about 1.5 seconds for data to reach Earth, simply because of how fast (or slow) radio waves travel, plus the processing and transmission delays.
The distance between the Earth and moon is 384,400km, which means that to any lunar vehicle Earth is just "a small dot. Therefore the antennas on the spacecraft need to be carefully pointed after landing to enable high speed communication," says Mounika Palreddy of Team Indus.
Astrobotic and Hakuto will use the Griffin lander as their central communication hub, similar to a Wi-Fi hotspot.
Moving around was the Achilles’ heel of China’s Jade Rabbit – it broke down after just a few weeks, and it’s here that the Lunar XPrize teams differ most in their approaches. Moon Express won’t have a rover – its MX-1 spacecraft/lander will simply take off and fly to new locations after landing.
Team Indus is building a four-wheeled rover called ECA. Weighing just 12 kg, it’s much lighter than, say, Nasa’s 900kg Curiosity rover on Mars. Still, ECA will have HD cameras to make a 3D map of its surroundings, so that its backup team on Earth can then plot the safest path for the rover to use.
Astrobotic is aiming to deploy Andy, a rover developed by Carnegie Mellon University. The team has already managed to move 500m through a lunar-like landscape at Robot City, a testing facility in an industrial wasteland near the Monongahela River.
Hakuto will have two rovers: Moonraker, a four-wheeled vehicle,and Tetris, with two wheels. Tetris is designed to descend into a possible cave entrance discovered on the moon. The team has performed lab tests for radiation, thermal vacuum and vibration, and a field test in the Hamamatsu Nakatajima sand dunes, which are “an excellent lunar analogue site because of its varied soft sand terrain and rock fields, but little vegetation,” says Kyoko Yonezawa of Hakuto.
Germany’s Part-Time Scientists are also betting on four wheels, with their Asimov R3 rover. It will be powered by a solar panel, with backup batteries “for power-peaks and unexpected situations,” says Karsten Becker. The rover has a head that can pan and tilt and houses three cameras – two of them are stereoscopic colour sensors with a wide-angle lens, while the middle one is a mono-colour camera with a filter wheel “to allow us to analyse the composition of various materials on the lunar surface by looking at different wavelengths of the light,” says Becker.
Our return to the moon is expected to yield not just great engineering, but also important science.
Team Indus aims to measure solar incidence, illumination and associated parameters at the landing site. Other planned scientific instruments include a UV telescope and a visual range camera.
Both Astrobotic and Hakuto hope to explore a pit in the moon’s Lacus Mortis (Latin for ‘Lake of Death’). Pictures taken by orbiters suggest that there could be a cave, which one day might provide shelter for astronauts and equipment “from solar radiation, micrometeorite strikes, and extreme surface temperatures ranging from -180°C in the lunar evening and reaching up to +120°C throughout the course of a lunar day,” says Thornton of Astrobotic.
Moon Express eventually aims to mine the moon for precious resources. And, says Richards, many of the firm’s customers “have scientific objectives, and we are flying a number of scientific payloads for a fee. This includes the International Lunar Observatory and the LPX Lunar Plant Growth experiment from Nasa”.
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