NASA needs a new strategic plan for mitigating the hazards posed by spent rocket bodies, discarded satellites

　　and thousands of other pieces of junk flying around the planet at speeds of 17,500 miles (28,164 kilomtres) per hour, the National Research Council said in the study。

　　The council is one of the private, nonprofit US national academies that provide expert advice on scientific problems。

　　Orbital debris poses a threat to the approximately 1,000 operational commercial, military and civilian satellites orbiting the Earth -- part of a global industry that generated $168 billion in revenues last year, Satellite Industry Association figures show。

　　The world's first space smashup

　　occurred in 2009 when a working Iridium communications satellite and a non-operational Russian satellite collided 490 miles (789 km) over Siberia, generating thousands of new pieces of orbital debris。

　　The amount of orbital debris tracked by the US Space Surveillance Network jumped from 9,949 cataloged objects in December 2006 to 16,094 in July 2011, the National Research Council said。

　　The surveillance network tracks objects approximately 10 centimeters in diameter and larger。

　　Some computer models show the amount of orbital debris "has reached a tipping point, with enough currently in orbit to continually collide and create even more debris, raising the risk of spacecraft failures," the research council said in a statement released Thursday as part its 182-page report。

　　"The current space environment is growing increasingly hazardous to spacecraft and astronauts," Donald Kessler, the former head of NASA's Orbital Debris Program Office who chaired the study team, said in a statement。

　　据美国上周四发布的一份报告，地球轨道上太空垃圾的数量已经达到“临界点”，有撞击风险，而后可能产生更多碎片，威胁宇航员和人造卫星的安全。

　　美国全国研究委员会在报告中称，美国宇航局需要制定新的战略计划，以减小火箭残骸、报废卫星、以及数千块其它太空垃圾的危害。这些轨道太空垃圾时速高达1.75万英里(28164公里)。