by Morris Jones
Sydney, Australia (SPX) Mar 23, 2012
Manufacturing has begun on China's first lunar lander, Chang'e 3, which is expected to launch in 2013. This spacecraft will release a rover onto the surface. If all goes well, we can expect the Chang'e 4 mission to land a year or two later, and perform a repeat of the previous mission.
Beyond Chang'e 4, things become even more interesting. China has discussed its plans for robot sample-return missions for years, and seems to have kept those plans on track. Previous reports suggested that the first sample-return mission, Chang'e 5, would launch in 2017 or soon afterwards. China has previously released illustrations of its proposed sample-return mission. The overall design of the spacecraft seemed to draw inspiration from the Soviet Union's Luna sample-return missions from the 1960s and 1970s.
The Soviets developed a robust, flat Moon lander with four footpads. This was used to carry the "Lunokhod" Moon rovers to the surface. The same landing stage was also used with the Luna sample-return missions. Instead of a rover, the landing stage carried a small sample-return rocket, along with a drill and arm to retrieve the sample.
The sample would be placed in a small capsule on top of the rocket, which then lifted off on a direct return to Earth. Approaching home, the capsule would separate from the rocket and parachute to the ground.
Chinese artwork, animation and models of their own proposed sample-return mission looked very similar. It seemed reasonable to develop a similar mission architecture, as it is simple and proven.
Now, things seem to be changing. Recent Chinese media reports suggest that there has been a re-design of the whole sample-return mission. It's more ambitious and more complex.
Details are sketchy, and we have seen no illustrations of the new hardware. But there has been a major change in the basic mission architecture. Instead of a direct return to Earth, the Chinese sample-return mission now uses Lunar Orbit Rendezvous.
Lunar Orbit Rendezvous is the same type of mission architecture used by the Apollo missions. Basically, a spacecraft that is departing from the surface of the Moon enters lunar orbit, where it joins up with another spacecraft already in lunar orbit. The Apollo missions featured a Lunar Module as the landing spacecraft, and an Apollo Command and Service Module spacecraft in lunar orbit.
China apparently intends to launch a robot sample-return spacecraft from the surface of the Moon, then stage a docking in lunar orbit with an Earth-return spacecraft. The samples will be transferred to this second spacecraft, then returned to Earth.
Chinese reports suggest that both spacecraft will be launched together on the same rocket. Why the change? One immediate reason would be a potentially larger cache of samples. Lunar Orbit Rendezvous reduces the amount of mass and fuel that must be landed on the surface of the Moon, and launched afterwards. This could permit more mass to be retrieved from the surface. Samples from the Soviet Luna missions were very small, and this new architecture overcomes this problem.
Of course, it's more difficult. Rendezvous and docking is complex. It's potentially even more difficult at such a great distance from Earth. But China seems bullish about is capabilities in rendezvous and docking, which were demonstrated on the Shenzhou 8 mission. In any case, the added complexities of the mission will probably push back the launch date by a year or two.
There's another potential advantage in flying a Lunar Orbit Rendezvous mission in the near future. It gives China further experience in technologies that will be needed to land Chinese astronauts on the Moon.
The Chinese are becoming more open in discussing this as a long-term objective. Ongoing advances in Chinese space technology suggest that China is moving steadily toward this ultimate goal in spaceflight.
Dr Morris Jones is an Australian space analyst and writer. Email morrisjonesNOSPAMhotmail.com. Replace NOSPAM with @ to send email.
The Chinese Space Program - News, Policy and Technology
China News from SinoDaily.com
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