The prequel of lunar rover Yutu(2)

GETTING ABOUT

Experts and designers pondered every conceivable question. One question was if the rover turns rolled over, could it right itself?

"After many trials, our conclusion was no, it couldn't. If the delicate equipment on the rover, as well as the solar panels, were covered with lunar soil, they could not work. So we could only consider how to keep the rover from overturning," says Jia.

Sometimes researchers argued fiercely. After they decided on a six-wheel rover, they debated for months on two plans for connecting the three wheels on each side.

Plan A had only a strong forward movement, while computer simulations showed plan B had a better ability to reverse. Researchers imagined a situation where the rover crossed a small obstacle and then faced an insurmountable obstacle. Then it must retreat. If they chose plan A, the rover could have problems. Finally, plan B won.

SLIMMING

Long before the launch of the lunar probe, Jade Rabbit's weight troubled its developers.

Designing the prototype, the researchers were required to keep its weight within 120 kilograms. The moon rovers of the former Soviet Union were more than 700 kilograms, while those of the United States were more than 200 kilograms.

The weight restriction was a result of China's rocket capacity and industrial capabilities.

"At the beginning, many veteran specialists thought it was impossible to make such a light rover. Even if we made it, it could be unreliable," Zhang Yuhua says.

"We tried everything we could think of to reduce the rover's weight," Jia says.

For instance, the antenna and the pole holding the cameras were combined. Changing from two foldable solar panels to one fixed and one foldable took off 500 grams.

Researchers replaced seven instruments for thermal control, navigation, data processing, with an integrated electronic device, taking off 20 kilograms.

Even the amount of solder and the number of screws was discussed and tested.

Little by little, Yutu's weight fell from 200 kilograms to the final 136 kilograms.

Experience gained from reducing the weight, such as the multi-functional design of the solar panel and the integrated electronic technology, could be adapted for future spacecraft, says Jia.