Shenzhou docking is good news for China's manned space station plans
By David Szondy
November 2, 2011
On November 2, 2011, China joined an exclusive club of space-faring nations when two unmanned Chinese spacecraft rendezvoused and docked 211 miles (340 km) in orbit above the Earth. At 17:29 GMT, the Shenzhou 8 capsule docked with the Tiangong 1 target vehicle. Though continuously monitored by ground control, the ten minute docking operation from first physical contact to seal confirmation was carried out entirely on automatic by the two robot craft.
Such an exercise is not new in the history of spaceflight. The first orbital rendezvous was achieved by two American manned Gemini spacecraft in 1965 and the next year the American astronaut Neil Armstrong commanded the fist docking between a Gemini and an Agena unmanned target vehicle. Since then such maneuvers have been achieved by Russia, Europe and Japan and were the main method for constructing the International Space Station. However, with this successful docking, China takes a major step forward in its goal to become a major space power and constructing its own manned space station by 2020.
The vehiclesThe Shenzou 8 spacecraft was launched on October 31, 2011 at 21:28 GMT from the Jiuquan Satellite Launch Center in the northwest Gobi desert of China's Inner Mongolian province. Carried aloft by an upgraded Long March 2F booster rocket, the unmanned craft was then run through a series of orbital maneuvers over the next two days to catch up with the Tiangong 1, which was launched on September 29. The two craft are scheduled to remain linked for the next 12 days, after which they will separate and the Shenzhou 8 will withdraw to a distance of 87 miles (140 km) before returning to re-dock. Two days later, the craft will uncouple for a final time and Shenzou 8 will return to Earth. Aboard the returning craft will be 17 life science experiments devised by German and Chinese scientists involving fish, worms, bacteria and human cancer cells.
Through the Shenzou 8 has no crew, the Shenzou "Divine Vessel" class is China's first manned spacecraft. With an overall length of 27 feet (9 m) and a maximum diameter of 9 feet (2.8 m), the craft has a liftoff weight of 8 tons. It is composed of three detachable parts.
First, there is the Orbital Module, which acts as docking system and airlock and is capable of being left behind in orbit to operate independently. This was the case with many of the previous Shenzhou flights and Western sources have speculated that they were used for military reconnaissance after being left in orbit.
Second is the Re-Entry Module where the crew sit. Resembling the re-entry module of a Soyuz spacecraft, as the name implies, this part of the ship is used to return the astronauts or (in this case) payloads to Earth safely by entering the atmosphere on a ballistic trajectory behind a heat shield and then drifting to the ground on parachutes where a recovery team is waiting.
And finally, the stern of the craft is made up of the Service Module, which contains the craft's rocket motors, fuel and other support systems including the solar panels needed to generate electricity and allows the manned version of the spacecraft to operate in orbit for up to 20 days. Like the Orbit Module, this is module jettisoned before re-entry.
The standard Shenzou spacecraft is designed with an additional set of solar panels on the Orbital Module up forward to power it while flying independently, but these were removed from the Shenzou 8 to reduce weight and make room for the universal docking system needed for the rendezvous with Tiangong 1 and for modifications that allow the unmanned craft to remain operational in space for up to 180 days.
If the Shenzhou 8 bears more than a passing resemblance to a Russian Soyuz spacecraft, this is not entirely a coincidence. Ever since the 1960s, the People's Republic of China has nursed an ambition to be a major player in space and, despite a history of waxing and waning support on the part of the Communist party, space was seen as being a way for China to "leap-frog" into the 21st century. The conceptual ancestor of the Shenzhou looked more like an American Space Shuttle or Dyna Soar space plane, but it was soon determined that such hypersonic engineering was beyond the grasp of Chinese technology and a capsule option was selected. In 1991, Russia began a policy of cooperation with China in space. The Russians briefed their Chinese counterparts on the design of the Soyuz, transferred space technologies and provided training for Chinese astronauts. The Chinese even acquired an incomplete Soyuz spacecraft, which caused some analysts in the West to suspect that the Shenzhou was a product of reverse engineering-a claim that the Chinese have always denied.
The "Heavenly Palace", Tiangong 1 Target Module is basically an elongated and simplified version of the Shenzhou. Thirty four feet long (10.5 m) and 11 ft (3.4 m) in diameter, it weighs the same eight tons as the Shenzhou and it's made up of its own service module and a pressurized module for the astronauts to visit. Its purpose is to act as a passive target for the Shenzhou and therefore doesn't require elaborate thrusters or maneuvering systems. It only has to remain on station and stationary while the other craft comes in to dock. Since its main purpose is to act as a test target, it is much more basic inside than the sort of instrument-packed modules one is used to seeing aboard the International Space Station. Its spartan accommodations consist of little more than exercise gear and monitoring equipment. There are also only two sleeping stations ("bed" is hardly the right word in free fall), so during future visits one astronaut must sleep in the visiting Shenzhou where all the cooking and other household chores are carried out as well.
What's nextAfter the completion of the current mission, the Tiangong 1 will remain in orbit for additional visits by manned and unmanned Shenzhou spacecraft until the module is retired and de-orbited to burn up in the atmosphere in 2013. It will then be replaced by the Tiangong 2 "Space Laboratory", which will, in turn, be replaced by the Tiangong 3 "Space Station". If these prove successful, then China plans to begin work on its 60-ton manned space station to be completed by 2020. This will be considerably smaller than the 15-nation International Space Station, but China will have joined a very exclusive club along with the United States and Russia as the only nations to have established manned outposts in orbit.
Whether China achieves its goal of a space station remains to be seen, but it is part of a very ambitious program. Within a week of the historic docking, China plans to launch its first deep space probe to Mars. Its manned spaceflight program for next year includes regular visits by astronauts to Tiangong 1 including two of China's first female astronauts. Having already sent two unmanned orbiters around the Moon, China next plans follow this up by landing a rover on the lunar surface as the vanguard of an eventual manned landing and the establishment of a Moon base.