CHINA’S FIRST ‘KISS’IN SPACE

By YIN PUMIN

CHINA’S FIRST ‘KISS’IN SPACE

By YIN PUMIN

The schematic of docking between Shenzhou 8 and Tiangong-1

Shenzhou 8spacecraft successfully docks withTiangong-1

At 1:36 a.m. on November 3,nearly two days after it was launched, the unmanned spacecraftShenzhou 8docked with space lab moduleTiangong-1, orHeavenly Palace-1. The docking represents another significant milestone for China’s space program.

Shenzhou 8was carried into space by a modified Long March-2F rocket,which took off from the Jiuquan Satellite Launch Center in northwest China’s Gansu Province at 5:58 a.m. on November 1. TheTiangong-1space module was sent into space on September 29.

The success of the docking procedure makes China the third country in the world,after the United States and Russia, to master the technique. The mastery of space docking technology takes the country one step closer to establishing its own permanent space station by 2020.

“China is now equipped with the basic technology and capacity required for the construction of a space station,” said Zhou Jianping, chief designer of China’s manned space program.

“This will make it possible for China to carry out space exploration on a larger scale,” he said.

“The capability increases China’s ability to act independently in space, as well as its ability to cooperate with others,” said Gregory Kulacki, senior analyst and China project manager at the global security program of the Union of Concerned Scientists,a nonpro fi t scienti fi c advocacy group based in the United States.

“China’s pursuit of an original solution to space docking could lead to innovations or experiences other space-faring nations may fi nd useful,” Kulacki said.

Making preparations

While the docking itself was completed in a matter of hours the planning and preparation for the mission involved over a decade of research.

JOB WELL DONE: Staff at the Beijing Aerospace Flight Control Center celebrate with each other after the successful docking of Shenzhou 8 with Tiangong-1 in the early morning on November 3

Space docking technology is considered one of the most advanced proficiencies required for space exploration as it requires the precise handling of two high-speed spacecraft that must meet and link up in space.

The world’s first space docking was achieved in 1966, when the manned U.S.spacecraftGemini 8docked with an unmanned Agena Target Vehicle.

Forty-five years later, the maneuver remains a technological challenge. Many of mankind’s 300-plus space-docking attempts have been met with difficulties or resulted in failure.

“To connect two vehicles traveling at 7.8 km per second in orbit, with a margin of error of no more than 20 cm, is really like ‘ fi nding a needle in a haystack,’” Zhou said.

“In order to guarantee the smooth operation of the mission, nearly 100 contingency plans had been prepared to address problems that may occur during the mission,” said Wu Ping, spokeswoman for China’s manned space program.

“The automated control system and docking system were crucial to the mission, and simulations had been performed several times on the ground,” according to Wu.

Meanwhile, Chinese space engineers made “considerable modifications” to theShenzhou 8, making it significantly different from previous versions of China’s unmanned spacecraft.

Shenzhou 8, with a length of 9 meters and a maximum diameter of 2.8 meters, has a liftoff weight of 8.082 tons.

“More than half of the spacecraft’s 600 or so sets of equipment had been modi fi ed technically, while newly designed devices account for about 15 percent of the total,”Wu said.

“The system for voice transmission between the spacecraft and the ground on this mission was completely new and significantly more advanced than the one used inShenzhou 7,” said Sun Yadu, chief engineer with Beijing Special Engineering Design and Research Institute, the main designer of the launch system used at the Jiuquan Satellite Launch Center.

“The modifications were mainly intended to equip the spacecraft with automatic and manual rendezvous and docking capacities, and to enhance the vehicle’s performance, safety and reliability,” Wu said.

“After the improvements, the spacecraft will be able to stay attached to the target spacecraft,Tiangong-1, for 180 days,” Wu said.

It’s not just the technology on board theShenzhou 8that ensured the mission’s success, the timing and precision of the spacecraft’s launch was crucial. The satellite had to enter the same orbital plane asTiangong-1.

“Tiangong-1’s orbital plane intersects with the launch site, we launchedShenzhou 8at the ‘zero launch window,’” said Wu,referring to the precisely prescribed launch time.

Technological modi fi cations were also made to the carrier. “The rocket features a new control system and an improved thruster, which means the Long March-2FY8 can carry a larger payload, features higher orbital precision and is more reliable than previous rockets,” Wu said.

The 58.3-meter-long Long March-2FY8 rocket has a total lift off weight of 497 tons and can carry a payload of 8,130 kg.

Meanwhile, the target vessel,Tiangong-1, had also been fully prepared for the upcoming docking.

On October 30, theTiangong-1completed a 180-degree turn-around under the control of the Beijing Aerospace Flight Control Center. The space module was then lowered to the 343-km-high docking orbit through a series of maneuvers which took place over the course of a month.

A historic meeting

Before the docking,Tiangong-1made fi ve orbital changes and four “brakes” over a 1.3-million-km journey.

After the maneuvers,Shenzhou 8entered an orbit belowTiangong-1, which circles 343 km above the Earth’s surface.

When the distance between the two craft narrowed to 52 km, sensors onShenzhou 8took over from ground control and safely guidedShenzhou 8’s approach toTiangong-1. Once the aircraft were in relatively close proximity it took two and a half hours of maneuvers to take the craft to within centimeters of theTiangong-1.

Then the even more delicate and precise docking process began.

“If spacecraft rendezvous is like two people getting closer together and meeting each other, then spacecraft docking is like the two people joining hands,” said Bai Mingsheng, vice chief designer of the space lab system of China manned space program.

The two spacecraft will fly as one for 12 days under the command ofTiangong-1. Then the two will unhook and remain 140 meters apart to await a second docking.

The two craft will then fl y together for two more days, beforeShenzhou 8separates fromTiangong-1and withdraws to a safe position 5 km away. “Its return capsule will head back to Earth in mid-November,” Wu said.

“Next year, China will launch two more Shenzhou spacecraft,Shenzhou 9andShenzhou 10, to dock withTiangong-1and at least one will be manned,” Wu added.

Ultimately this series of space docking tests and experiments will provide crucial experience for China’s construction of a permanent manned space station.

“AlthoughShenzhou 8is unmanned, we equipped the spacecraft with devices which record real images and mechanical parameters during its fl ight, both of which are vital to future manned missions.Tiangong-1is also in full readiness for the entry of astronauts next year,” Wu said.

Equipment for astronauts to use for physical exercises, medical monitoring and health maintenance has already been installed insideTiangong-1.

Chen Shanguang, Director of the Astronaut Center of China, was quoted by Xinhua News Agency as saying that a crew of nine, including two women, has already been selected and is being trained in manual docking skills.

He said that the seven men are from the country’s fi rst batch of 14 astronauts,which includes Yang Liwei, China’s fi rst man in space in 2003, and Zhai Zhigang,the fi rst to conduct an extra vehicular activity in 2008.

The two female astronauts, both airfreighter pilots before their enrollment, are from the second batch of astronauts trained between 2009 and early 2010.

“We must assess the performance of both male and female astronauts, it is important to monitor the impact of space travel on both genders, and space exploration activities would be incomplete without the participation of female astronauts,” said Chen.

“Besides testing docking technology,theShenzhou 8will also carry out scienti fi c experiments,” Wu said.

On this mission, Chinese and German scientists will conduct 17 space life science experiments. “German scientists designed bio-incubators for the experiments, while their Chinese counterparts were in charge of the development of control equipment,” Wu said.

The experiments will help promote the study of microgravity and space life science, 10 of the experiments will be controlled by China, six by Germany, and one will be a joint effort.

“It is the first time China’s manned space program has conducted joint experiments in the fi eld of space life science,” Wu said.

“New knowledge obtained through space science research should be used for the common wealth of all human beings and should bene fi t the whole world,” chief designer Zhou said.