|Simulation image of Chang'e-3: seperation of lander and rover. (Xinhua/Li Xin)|
Recently, the China Association for Science and Technology sponsored a meeting where scientists and the media were able to communicate face to face. The theme of the session was “Lunar Exploration---My Chinese Dream”. Scientists including Wu Weiren, chief designer of China’s lunar exploration project, Liu Jianzhong, deputy chief designer of the Chang’e-3 carrier rocket system, Zhang He, deputy chief designer of the lunar probe system, and Su Yan, deputy chief designer of the ground application system, answered questions about the next stages of China’s lunar exploration project and the possible Mars venture.
The success of Chang’e suggests that China is ready to explore Mars
According to Wu Weiren, after the successful launches of Chang’e-1 and Chang’e-2, China already has the capacity to explore Mars. Mars’ orbit around the sun takes more than 700 days, and during this time Mars and Earth will have one encounter. This provides the ideal launch window since the distance between the two planets is at its shortest. The Long March 5 carrier rocket currently under development will have a maximum thrust of nearly 1100 tons, so it will be more than capable of launching a probe to Mars.
Wu Weiren further explained that the decision whether and when to explore the Mars depends on the financial resources available, and the priorities of the country as a whole.
The Long March 5 research is proceeding smoothly, and the Wenchang launching site is under construction (Wenchang City is located in the northeast of Hainan province, an island in the South China Sea).
According to Wu Weiren, Chang’e-5 will be launched around 2017 with a mission of bringing lunar soil samples back to Earth. The main difficulties the mission will encounter are: rendezvous and docking in lunar orbit, obtaining samples after landing on the moon, taking off from the moon, and returning to earth at high velocity.
It is not easy to collect samples on the moon. The Soviet Union tried several times, but its three successful attempts only managed to bring back a little more than 300g of lunar soil. Chang’e 5 plans to bring back 2 kg. It will dig two meters into the ground in search of uncontaminated samples, and bring them back in sealed containers. Chang’e-5 is also equipped with a lander and a return capsule, so rendezvous and docking in lunar orbit will be much more difficult. Lift-off and high-speed return to Earth are also turning out to be technical challenges.
In response to the question “Why choose Wenchang as the launch site of Chang’e-5?” Liu Jianzhong explained that Chang’e-5 will be launched by the Long March 5 carrier rocket. Development of the rocket is going well, as is the construction of the Wenchang launch site. The choice of Wenchang as the launch site for Chang’e-5 is based on two consideration: Firstly, the Long March 5 rocket is massive, so transportation will be a problem. Launching from Wenchang will allow the rocket to be transported to Hainan by sea. And secondly, the Wenchang launching site will allow the rocket to be launched eastward over the sea where there is little population - a major advantage for the site in terms of safety considerations.
In comparison with other countries, China’s investment in lunar exploration is limited.
Talking about China’s investment in lunar exploration, Wu Weiren said: “Compared with other countries and looking back to the 20th century, China’s investment is limited.” It is known that in the 1960s and 1970s, 118 lunar expeditions were carried out, of which the Soviet Union made 64 launches and the US 54, and the success rate was about 40 percent. Since then the US, India, China, Japan and other countries collectively have conducted just over 10 lunar expeditions. China’s Chang’e-1, 2 and 3 all launched successfully, representing a high success rate. The US Apollo Project lasted more than 10 years and represented an investment of at least 25 billion USD. The US invested 2-2.5 percent of its GDP in lunar exploration over the decade. In contrast, China’s current investment is less than one thousandth of its GDP. In comparison with the Apollo program, our investment is therefore quite limited.
In terms of the contribution of space technology to the national economy, Wu Weiren added that the input-output ratio of the Apollo Project was about 1:15. As time goes on, China will surely benefit from the expertise developed for lunar exploration in areas such as control technology, simulation technology, information technology, new materials, etc.