|China's third unmanned lunar spacecraft Chang'e-3 deploys only the thrid teleoperated lunar rover on the Moon, the first in 37 years, in 2013 [CNTV/CLEP].|
The United States scrubbed plans to land a robotic lunar rover on the Moon as unnecessary, originally an extension of the successful Surveyor program (1966-1968), in favor of concentrating all effort on carrying out the Apollo missions. Between 1968 and 1972 a total 24 Americans left Earth orbit to visit the Moon's vicinity (three of these went the distance twice), and 12 astronauts explored the lunar surface. Though the U.S. deployed three Mars rovers, with a fourth on the way, Russia alone holds the distinction of having landed and operated the only robotic rovers on the Moon.
Though many U.S. and international teams are competing for the Google Lunar X-Prize, and the U.S. presently has a total of five sophisticated probes in lunar orbit, it now seems almost certain that China will become the first nation to soft land anything on the Moon since the Soviet sampler Luna 24 came to rest in the far eastern Mare Crisium in 1976.
The U.S. has no hard commitment to land a vehicle on the Moon at present, though the International Lunar Network and a South Pole-Aitken basin farside sampling mission continue in the planning stages. Internal challenges in both Russia and India have caused delays to ambitious plans for lunar surface missions set alone and in tandem with one another. Japan's SELENE program, which at one time called for lunar rover, continues to muddle through severe budget challenges.
Though China admits to being somewhat behind on the timeline it has set for building its third lunar mission, Chang'e-3, intended as a rover deployed following a soft landing on the Moon, the PRC does not express concern over plans to carry out that mission in 2013. Articles about Chang'e-3 published by China's state-owned media continue to surface regularly.
Only 12 Americans have so far walked on the moon. The next person to do so could be from China.
According to a white paper, China's Space Activities in 2011
, released in December, preliminary research on a manned moon landing will be carried out in the next five years, along with research on a heavy-thrust carrier rocket, vital for launching manned spacecraft to the moon.
Scientists expect a manned moon landing could be achieved by China in 20 years, though there is no fixed timetable yet.
Experts, however, say that before taking the giant step, China needs to complete its robotic lunar exploration program, as it will lay the platform for successful moon landings.
The chief scientist for the lunar exploration program, Ou-yang Ziyuan, has already indicated that China has the ability to launch men to moon, but it's "a single-trip ticket", meaning the nation does not have the capability to ensure that astronauts can return to Earth.
"The three steps set in the unmanned lunar exploration program are something China must undertake before commencing the plan to send men to the moon," he says.
China adopted the robotic lunar exploration program in 2004, which includes three steps - circling the moon, landing on the moon and returning with a sample.
China has completed the first step by launching the Chang'e-1 probe in 2007 to orbit around the moon, thereby becoming the fifth country in the world to independently launch lunar orbiters.
It is now in the second phase of achieving a soft landing on the moon. Chang'e-2, the backup satellite for Chang'e-1, was modified and launched in 2010 to test some key technologies for soft landing.
"Next year, the country's third lunar probe, Chang'e-3, is expected to be launched as planned and will conduct a soft landing on the moon," says Ye Peijian, chief designer of Chang'e-1 and chief commander of the satellite system of the Chang'e-2 and Chang'e-3 missions.
The orbiter will carry a lunar rover and other instruments for territory survey, assessment of living conditions and space observations.
"Chang'e-3 will be the first spacecraft with the first-ever China-designed 'legs' The lunar rover is also the first of its kind to be tested in the harsh environment on the moon," he says.
Preparations have also been advanced for the third phase, which aims to bring soil samples back to Earth before 2020.
Both the United States and the former Soviet Union have already sent spacecraft to the moon, but in two different ways. Hu Hao, chief designer of the program's third step, says that scientists have finally decided on how to achieve the goal of returning soil samples from the moon.
According to Hu, China will carry out a "Lunar Orbit Rendezvous" - the mode used by the Apollo Programs - to collect as many samples as possible.
Under the plan, a rocket will be launched from Earth that will put four modules into the lunar orbit. Two modules will land on the moon, while one will scoop up soil. The soil sample will be placed into the ascending module that will blast off from the lunar surface and dock with the orbiting module. The sample will then be transferred from this module to another one that will be jettisoned for Earth re-entry.
Though the US has done this kind of exercise more than four decades ago, the Chinese aerospace scientists have no one to count on, but rely on themselves to solve the major technical problems, Hu says.
China plans to scoop up as much as 2 kilograms of soil samples, but how to do it could also be a tricky problem.
|The Automatic Lunar Surface Exploring Vehicle, China's planned Chang'e-3 lunar rover, "a solar powered vehicle designed and built by the China Academy of Space Technology (CAST). The six-wheeled rover has a designed life of 90 days to explore three square kilometers, a total mass of 120 kg (with a 20kg payload capacity) designed to travel up to 10 kilometers."|
"The vehicle is capable of autonomously navigating around obstacles, selecting optimal routes and areas of interest. On-board equipment includes subsurface radar and an optical telescope. An on-board camera can capture images of the lunar surface and a mechanical arm, designed by Hong Kong Polytechnic University, will allow the vehicle to collect samples for analysis. The vehicle can transmit image and data back to the Earth in real-time and all on-board equipment are capable of operating normally during the 14 day-long lunar night."
The former Soviet Union's three missions collected just over 300 grams of lunar soil. The US had better success and returned 381.7 kg of rocks and other material from the moon, thanks to astronauts' participation.
"China's mission is also a robotic one. The probe could land on an unknown spot that could be rocky, and drills could fail to deeply penetrate the lunar surface, just like a mission by the former Soviet Union," he says.
The difficulties also include how to launch the ascending module from the lunar surface and how to conduct rendezvous and docking operations in the lunar orbit.
"China conducted its first spacecraft rendezvous and docking operation in the low-Earth orbit successfully last year. But how to do it in a lunar orbit more than 300,000 km away from Earth is a new challenge," he says.
The space docking last year relied on the global positioning system, which, however, will not be of much use during a lunar orbit rendezvous. The docking ports on the ascending module and the orbiting module need to be redesigned and tested, as the modules are much smaller in size.
Finally, scientists also have to solve the problem to have the probe re-enter the Earth atmosphere safely.
China also lacks experience in how to make the sample-carrying capsule re-enter the Earth atmosphere safely, he says.
While previous re-entries of unmanned and manned spacecraft were made at 7.9 km per second, the return capsule with the lunar soil sample will be hurtling to Earth at, or close to, speeds of 11.2 km per second.
He says that the third phase will launch two orbiters to achieve the goals before 2020. Earlier reports said that the first of these is likely to be launched around 2017.
"We are under pressure as only a short time is left," he says.
Scientists are also stressed due to the public's unrealistic high expectations for success, he says. In recent years, consecutive successes in the space sector have buoyed expectations for more missions.
"People now tend to underestimate risks in space activities. They think it is easy and have little tolerance for failure. But even space powers like the US and Russia have had several failures," he says, adding that more tolerance is essential for the healthy development of China's aerospace industry.