Researcher assisted on 1st nuclear submarine

"It was extremely difficult to find a little piece of information," he said. "The information was either too fragmented or hard to tell whether it was true or false."

They finally came up with five plans after piecing together all the information they found and carefully analyzing and studying two US submarine models.

"We believed the complex cutting-edge technologies were still based on basic knowledge," Huang said.

The team members didn't have any computers or digital calculators, so they used abacuses and rulers to solve problems. To ensure accurate calculation results, they were divided into three groups to do the math at the same time and would recalculate if the three values reached were not the same.

Their worked continued, even when the project was suspended from 1962 to 1965, when China endured economic difficulties.

In 1970, China's first nuclear attack submarine underwent maritime tests. Named Long March No 1, it entered Navy service in 1974, making China the fifth nation to have a nuclear submarine.

In 1988, the vessel was ready for its initial dive test, a very dangerous task that had led to the sinking of the US sub Thresher in 1963 with all hands in one of the deadliest submarine disasters in history.

Although the research team, the Chinese sub's manufacturer and the Navy overhauled all equipment and prepared comprehensive emergency plans for all operating systems and devices, many personnel still wrote farewell letters in the event of their deaths.

Under those circumstances, Huang, 62, decided to go onboard and participate in the test himself.