BEIJING — The modified Long March 2F rocket that launched China’s Shenzhou 8 capsule on Nov. 1 performed with exceptional precision, space program officials say.
The capsule appears to be a prototype for a new design standard in the Shenzhou series of human-transportation spacecraft, with manual as well as automatic docking systems, even though in this instance it was launched without a crew. Two automatic docking maneuvers with the target module, Tiangong 1, are the chief objectives of the mission, which must demonstrate the technology if China is to build its planned space station.
The latest official state media reports on the manned space program have introduced a note of caution. The next two Shenzhou missions, numbered 9 and 10, are now said to be planned for next year “if all goes well,” while the goal of launching the space station will be achieved “possibly” in 2020, according to the Xinhua news agency.
The carrier rocket, built to a standard called Long March 2FY8, had greater payload, orbital precision and reliability than other Long March 2Fs, says program spokeswoman Wu Ping. Its mass at liftoff was 497 metric tons, including a payload of 8.13 metric tons.
Liu Yu, the official in charge of the mission’s launcher, says 100 changes were made to the design, including iterative guidance technology that improves precision. The rocket performed perfectly, Liu says.
The claim of improved reliability is striking, since the Long March 2F is already China’s human-rated launcher, meaning that it is the one that has sufficiently robust and redundant components to be trusted to carry people. The version that hurtled Tiangong 1 into orbit on Sept. 29 was a Long March 2FT1. The Long March 2F is a product of China’s main carrier rocket builder, CALT, which is part of national space contractor CASC.
The Shenzhou design of spacecraft builder CAST has also been modified. Wu says half of its 600 “sets of equipment” have been changed and 15% are now new, mainly to give it automatic and manual docking systems. Shenzhou 8 therefore seems to be equipped with the complete docking apparatus of future Shenzhous. The maximum error is 20 cm (8 in.), the Chinese officials say, apparently referring to what the mechanical mating equipment demands of the guidance and maneuvering system. Docking guidance relies on microwave radar and laser ranging.
The launcher placed Shenzhou 8 in a position 10,000 km (6,200 mi.) behind Tiangong 1 in an orbit with an apogee of 330 km; it is now closing the range, with the aim of docking on Nov. 3. Its orbit will be changed five times and it will brake four times, Xinhua says. Tiangong 1’s orbit has an apogee of 343 km.
Both were sent to orbit from the Jiuquan launch center, whose latitude is 41 deg. N. Tiangong 1 also will serve as the docking target for Shenzhou 9 and 10.
In preparation for the 60-ton space station, China is working on a cargo craft with a loaded mass of 13 tons, which state media say will resemble Tiangong 1. Both have diameters of 3.35 meters (11 ft.), the same as that of China’s current carrier rockets, probably allowing the manufacturer to use some of the same tools in making them.
The unnamed cargo craft will be built in two modules, Zhou Jianping, the chief designer of the manned space program, told state media after Tiangong 1 was launched. One module would carry the cargo and the other would be the “resource” section of the spacecraft, presumably meaning it will carry the fuel, thrusters and maybe avionics. It will carry up cargo only; there is no mention of an Earth-return module. The launcher will be the Long March 7 rocket, which officials said last year was still in the planning stages and would go into production in 2014. With two 120-ton YF100 engines burning kerosene and liquid oxygen, and with a presumably variable number of strap-on boosters, its throw-weight to low orbit is intended to be 10-20 tons.
The space station will comprise three modules. Its launcher will be the Long March 5, also under development and due to make its first flight in 2014.