中國：「天宮一號」明年下半年墜落必要時發預警 外媒：顯示已經失控
中國證實首個太空實驗室「天宮一號」將於2017年下半年墜落地球，但暫時未知地點。有外媒認為，中國已間接承認「天宮一號」失控的傳言。
中國載人航天工程辦公室日前就太空實驗室「天宮二號」舉行記者會，期間被問到「天宮一號」的下落，航天工程辦公室副主任武平表示，目前「天宮一號」結構完整，根據當局的計算分析，「天宮一號」在墜落時，大部分會在大氣層燃燒，相信其碎片危及航空活動或地面的機會不大。當局會繼續密切監察「天宮一號」，如果發現墜落有可能引發碰撞事件，會發出預警。她強調，必要時會向國際公布「天宮一號」重返地球的預測報告。
天宮一號於2011年9月升空，今年3月完成任務，武平說，天宮一號設計壽命原本是兩年，但實際工作了四年半，對中國航天科技作出重大貢獻。
華盛頓郵報指，一般退役衛星會被引導到太空的衛星墳場，成為逾數十萬件太空垃圾之一，又或者在指定海域上空墜毀，即使有少量部件未有在大氣層燒毀，也會墜落深海。然而，中國官方表示如有需要會發出預警，則意味「天宮一號」很可能已經失控。
今年6月，一名追蹤衛星的發燒友Thomas Dorman在Space.com表示，他認為中國已失去對天宮一號太空實驗室的控制，「假如它落在人口稠密的地方就相當麻煩......如果我的預測正確，中國會在最後一刻才讓世界知道『天宮一號』出了問題。」
哈佛 - 史密森天體物理中心（Harvard-Smithsonian Center for Astrophysics）的Jonathan McDowell在接受英國《衛報》訪問時說，「天宮一號」可能已經失控，這將會令地面人員難以預測其墜落地點和時間，「人們可能在其墜落前的6-7小時前，甚至更短時間才知道。既然不確定落下的時間，就意味根本不知道它會落在什麼地方。」
天宮一號太空實驗室重8噸（一般衛星小則重1噸，大則重3噸）， McDowell表示，大部分碎片該可以在大氣層燒毀，但一些部件如引擎是很難完全燒毀，所以不能排除對地面構成危險的可能性，「如果是100公斤碎片掉下來是可以造成痛擊，也可能是細碎的金屬碎片像雨般落下，擊中屋頂、汽車甚至飛機。」
一般來說，國際上處理退役航天儀器（如衛星）的做法有幾種，其一是把衛星轉移至不妨礙其他衛星運行的軌道。體積小的可以任由它在大氣層完全燒毀。也可以引導它在指定海域墜落，又或者用反衛星武器將它炸毀。
中國科技網於2013年引述的報導曾經提過當局對「天宮一號」的原定處理方案，就是在結束任務後以最後的燃料進行「變軌」，讓它最終返回地球的南太平洋。不過，日前的記者會並無再提及這個做法。
https://hk.thenewslens.com/article/49761
引用:
Tiangong-1 Space Lab Will Fall to Earth Next Year, China Says
China's first-ever space lab will die a fiery death in Earth's atmosphere toward the end of next year, Chinese officials said.
The 9.4-ton (8.5 metric tons) Tiangong-1 spacecraft is currently intact and orbiting Earth at an altitude of 230 miles (370 kilometers), according to Wu Ping, deputy director of China's Manned Space Engineering office. That's a bit lower than the International Space Station, which usually stays about 250 miles (400 km) above the planet's surface.
Tiangong-1 will likely fall back to Earth in the second half of 2017, and its demise shouldn't cause problems here on the ground, Wu said. [Gallery: Tiangong 1, China's First Space Laboratory]
"Based on our calculation and analysis, most parts of the space lab will burn up during falling," she said during a news conference Wednesday (Sept. 14), according to China's state-run Xinhua news agency.
China is monitoring Tiangong-1 (whose name means "Heavenly Palace" in Mandarin) closely and will issue the appropriate warnings if the space lab threatens to hit a satellite, Wu added. She said that China will release a forecast of Tiangong-1's fall to Earth "if necessary," according to Xinhua.
The update from Wu seems to confirm speculation that China is no longer in control of the 34-foot-long (10.3 meters) Tiangong-1, which launched in September 2011 to test out docking technologies and other skills that China will need to build its planned space station in the early 2020s.
After all, if operators were still controlling the space lab, they could steer it to a guided re-entry over an empty stretch of ocean at a specified time.
Three spacecraft docked with Tiagong-1 during its operational life — Shenzhou-8 in November 2011, Shenzhou-9 in June 2012 and Shenzhou-10 in June 2013. The latter two missions were crewed, each carrying three Chinese "taikonauts" up to the space lab.
Tiangong-1 stopped sending data back to Earth in March 2016, officially ending the space lab's mission. But its successor is now aloft: Tiangong-2 launched atop a Long March 2F rocket on Sept. 15 from the Jiuquan Satellite Launch Center in northwestern China.
Two taikonauts are scheduled to arrive at Tiangong-2 in mid- to late October for a 30-day stay, Chinese officials have said. (The Shenzhou-9 and Shenzhou-10 crews spent eight and 12 days aboard Tiangong-1, respectively.)
China is not part of the multinational consortium, led by the United States and Russia, that operates the 440-ton (400 metric ton) International Space Station. China aims to have its own 60-ton (54 metric tons) space station up and running in Earth orbit by 2022 or so.
http://www.space.com/34089-tiangong-...arth-2017.html
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原來中國都有馬沙
