Today’s news that Chang’e 5 landed on the moon and planning to bring a sample of lunar soil back, called to my memory of my time in Tsinghua.
As I remember this Chang’e mission started about 15 years ago, almost the same time that I started in Tsinghua. If you are not a soil mechanics expert, you may not be able to imagine how this mission could be linked to soil mechanics. Actually, at the very beginning of the Chang’e mission, we were involved. The first task was to estimate the response of soil to the reentry capsule when it landed as planned somewhere in Inner Mongolia. (The planned landing spot for Chang’e 5 this time is still in Inner Mongolia.) The second task was to build a test area in Beijing, modelling the soil in Inner Mongolia, so that some experiment could be carried out in Beijing instead of Inner Mongolia. During those time, discussion on lunar soil sampling project already began, it is about 15 years ago. Now, finally, we see this mission carried out.
To model soil that does not exist on the earth is difficult. Our focus is on the mechanical behaviours of soil so that to provide basis for design of sampling machine and lunar vehicle. Some of issues that need to be considered include low gravity (1/6 of earth), vacuum condition and dry condition. The issue of gravity is especially concerned, because it effects confining pressure so that effects the strength. And this issue effects design of some experiments . For example, when design a triaxial test, distribution of confining stress due to the size of soil sample is always neglected, but when the confining stress is very low, this kind of difference due to soil sample size may not be negligible.
Many problems need to be considered and studied and it is very interesting. I never regret to dedicate in research related to soil. The complexity of soil makes this kind of mechanics very special compared to other mechanics. And today’s news also reminds me a lot of memories about people and time over ten years ago…How time flies!
Now China is going to scoop up 1.5kg lunar soil on the surface and to correct drilling sample about 0.5kg. If all goes to plan, China will become one of three countries to bring back samples from the Moon. US astronauts retrieved lunar soil samples during the Apollo missions in the 1960s and 70s, and the former Soviet Union brought back lunar material through a series of robotic missions in the 1970s. In fact, the last successful lunar sample return mission occurred in 1976 with the Soviet Union’s Luna 24 mission. With Chang’e-5, China could bring the first material back from the Moon in nearly half a century.
We are looking forward to the success of the Chang’e 5 mission.钻进取样试验用模拟月壤