曝光臺 注意防騙 網(wǎng)曝天貓店富美金盛家居專營店坑蒙拐騙欺詐消費(fèi)者

Nonetheless, China’s space program has encountered signifi-cant technical problems, particularly with satellites. China’s domesti-cally designed high-capacity communications satellite platform, called
LEO is generally defined as the region from the lowest altitude at which an object can be maintained in orbit (about 160 km) up to about 2,000 km. GEO is an orbit in which the satellite orbits in the same plane as the earth’s equator and at an altitude such that it revolves around the earth at the same angular rate as the earth’s rotation (42,164.km). This results in the satellite appearing to hover over a fixed location on the earth’s equator, hence the term “geostationary.” Most communications satellites are in GEO.
Dongfanghong 4 (DFH-4), has experienced multiple failures. The Huanjing series of environmental and disaster-monitoring satellites and the Haiyang series of oceanographic satellites, although they have experienced no known failures, are being deployed more slowly than originally announced. Three out of 10 Beidou-series PNT satellites have also experienced technical problems. It is not clear whether these problems are due to underlying design issues, insufficient quality con-trol in construction, or simple poor luck, but China’s space capabilities will probably not develop as quickly as outlined in the “National Guid-ance for Medium- and Long-Term Plans for Science and Technology Development (2006–2020).” Nonetheless, comparison with the suc-cesses of China’s space program suggests that any technical problems will be overcome eventually. The ultimate effect on U.S. national secu-rity will be the same, but that effect might not emerge as quickly as current plans would imply.
Despite some technical setbacks, Chinese satellites now provide increasingly sophisticated intelligence, surveillance, and navigation capabilities that have significantly advanced China’s military capabili-ties. Though the capabilities of the satellites fall short of U.S. stan-dards, they are more than sufficient for most military purposes. China’s commercial space prospects seem more limited given extensive foreign competition, but its space launch program has achieved a number of successes that make it potentially appealing to other countries inter-ested in launching commercial satellites.
Launch Vehicles
All of China’s operational space launches have been performed by the Chang Zheng (CZ) family of rockets, although China is apparently developing a family of small solid-fuel launchers called Kaituozhe (Pio-neer). The design of the CZ family was based on the Dongfeng series of ballistic missiles developed in the 1960s. The first CZ rockets were launched in 1969 (that rocket failed), 1970, and 1971 from Jiuquan Space Launch Center. There are currently three operational series of CZ missiles: CZ-2, CZ-3, and CZ-4. All use liquid-bipropellant-fueled engines, and all can be launched from one of China’s three currently operational launch sites. The most powerful versions are capable of carrying at least 8,000 kg (the weight of the Shenzhou manned space modules) into LEO and more than 5,000 kg into GEO. As of June 2010, there had been 125 launches of the CZ series (“Long March [Chang Zheng],” 2010; “Shenzhou Series,” 2009).
　
中國航空網(wǎng) www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：Ready for Takeoff China’s Advancing Aerospace Industry(58)