Astronaut Jing Haipeng displays a capsule used to house silkworm larvae during the 33-day mission aboard Tiangong II. (Photo/Xinhua)
Those used for the Shenzhou XI mission were produced at CASC's No 5 Research Academy. Engineers at the corporation had concluded that most silkworms could not survive the harsh environment of space, so they set about breeding a new, hardier and healthier strain.
What followed was a series of rigorous screenings. The ideal larvae had to be bigger than their peers and whiter in color, according to Wei Xilin, an engineer at CASC, speaking on China Central Television.
The shortlisted larvae were put through a final test, and the engineers finally chose the six healthiest, Wei explained.
In the early stages, experts from China's Manned Space Agency provided the students with knowledge of conditions inside the spacecraft, as well as an understanding of how to breed larvae.
Leung Tsz-wan, 17, one of the students, said the exchanges with space experts from the mainland were essential in shaping their ideas into a meaningful experiment.
Blueprint
The blueprint proposed by the students was a large, square, transparent box fitted with an electric fan to extract the feces excreted by the larvae. In terms of shape and size, it was different from the end product forged by CASC that went into space and contained six compact capsule-shape containers, each housing an individual larva.
The principles of the capsules were not a major departure from the students' original proposal. Speaking to China Daily when they revisited their prototype, the students said many larvae died of dehydration during the early stages of the experiment because they were fed stale mulberry leaves rather than fresh ones. That led to the students proposing replacing the leaves with moistened food pellets.
Later, CASC optimized the students' idea. Instead of using food pellets, the engineers modified the mulberry leaves into a greenish paste that locks in moisture. The paste was then smeared on the insides of both ends of each capsule, allowing the larvae to crawl through the tubes and feed, according to Zhao Danni, the CASC engineer who designed the capsule, in an interview with CCTV.
The inner walls of the capsules were also sheathed in shock-absorbent foam made from aerospace-grade polyurethane and designed to prevent the larvae from coming to harm as the spacecraft juddered skyward, she said.
Once Shenzhou XI had completed its automated docking procedure with the orbiting Tiangong II on Oct 19, the experiment was ready to begin.
"We observed, took care of the larvae and spruced up their homes on a daily basis," Jing said, in a video taken aboard the space lab. He and Chen shared "fatherly" duties for the larvae for the first eight days of the mission, from Oct 19 to 26.
