The prequel of lunar rover Yutu(3)

SURVIVING A MOON NIGHT

One night on the moon is about 14 days on the earth, during which the temperature falls below minus 180 degrees centigrade. The storage battery could provide heat for Yutu during the moon night, but it was abandoned because it was too heavy.

Researcher Shao Xingguo came up with an idea of making use of the gravity of the moon to develop a two-phase fluid circuit. The circuit is like a heating pipeline to convey the heat emitted from the radioisotope heater units outside the rover body to warm the instruments inside.

According to initial plan, Yutu had to find a suitable position before the coming of the moon night, so the sunlight could reawaken it a fortnight later.

However, after Yutu landed on the moon, it couldn't find such a position, so it used its trump card - rolling some of its wheels to dig a little pit to adjust its angle.

The solution was inspired by solving another problem.

The US Mars rover, Opportunity, was trapped in the soft sands on Mars in 2005. Engineers on earth struggled for a long time to get it out.

"It was a warning for us. Being trapped in the lunar soil was possible. So we conducted trials. We buried one third or half of the wheels in soil to test how to get it out by rolling the wheels and adjusting its posture, " says Jia.

"And then we thought the posture adjustment method could be used to prepare for the moon night."

NEW FRONTIERS

About half of the more than 100 times lunar exploration missions by all countries have succeeded.

"The rover was not as complicated as an airplane or aircraft carrier. But the severe and unpredictable environment on the moon and the fact that the rover could not be repaired after its launch increased the difficulty and risk of the mission," Jia says

To ensure the success and safety of China's space missions, the use of new products and new technologies on each spacecraft is usually limited to less than 30 percent, but they exceeded 80 percent on the Chang'e-3 lunar probe.

Many veteran space specialists worried about the success of the mission, and researchers conducted strict tests on Yutu before its journey to the moon.

They built a lab covering 800 square meters within CAST to simulate the lunar environment. A 50-cm deep floor of volcanic ash similar to the lunar soil was dotted with rocks and craters.

Here they tested Yutu's ability to move, turn, climb, cross obstacles, take pictures, send messages and detect soil content.

"Although we did our utmost, residual risks remained. The pressure was huge," Jia says.

Even though China lags far behind the United States and Russia in the space sector, it boasts a large number of young talents in the field.

The average age of the developers of the Chang'e-3 lunar probe was in the early 30s. When Sun Zezhou was appointed chief designer, he was 37, the youngest chief designer in China's space sector.

Sun Jiadong, chief designer of China's lunar exploration project, says these young men will bring China's space industry into a golden age in 20 years.