Submersible's developers reveal winning formula

The institute put nearly 100 researchers and elite engineers on the Fendouzhe project. The team was responsible for the vehicle's coordinated manufacturing, which entails several stages of designs, integration of hardware and software, and debugging, according to Hu Zhen, the submersible's deputy chief designer.

"Our team members come from all kinds of specialties to meet the comprehensive design and assembling requirements of Fendouzhe," Hu said.

"But that's still not enough. More than 100 scientific units from across the country have our back, providing their technologies and inventions," Hu added.

The submersible's spherical cabin alone is a joint effort of dozens of research institutes and companies, said Li Yanqing, another deputy chief designer of Fendouzhe.

The cabin uses a new titanium alloy that is lightweight and has the strength and toughness for the appallingly high pressure in the abyss. The material was created by the Institute of Metal Research of the Chinese Academy of Sciences, which also developed a new welding and manufacturing technique to make the giant titanium sphere.

The cabin, after being welded, went through complicated flaw and residual stress detection by professional testing organizations in Wuxi, he added.

Even after the submersible rolled off the line, the job for the engineers was far from being done, as they had to perform meticulous checkups and maintenance each time before the vehicle was tested in the water.

Du Kun, a senior technician responsible for the cabin's sealing operation, revealed that during cabin work he didn't wear a helmet, watches or rings – anything that could cause a scratch on the delicately sealed windows and gate by chance, however tiny it was.

This protocol proceeded due to the special working environment, he explained.

"All three pilots' lives were in the hands of Mr. Du. You can say that," said pilot Zhang. "Any human error, such as missed impurities or unconfirmed seals, could put us at life-threatening risk."

Fendouzhe is now docked at the southern Chinese port city of Sanya for post-expedition checkups before being officially put into use for ocean exploration purposes.

But for its engineers, the mission doesn't stop here.