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选材规范、标准演练;循序渐进、梯度提升;题量丰富、有效提高;技巧同步、一语中的;缩略速记，全面覆盖。 注意直接听写正文 Space junk, also known as space waste, is objects in orbit around Earth created by humans that no longer serve any useful purpose. They consist of everything from entire spent satellites to explosion fragments, deliberate insertion of small needles, and many other objects. As orbits often overlap, the space junk is a potential collision risk for spacecraft. The vast majority of pieces of space junk are small particles. Contact with these particles causes erosive damage. The majority of the damage can be eased by adding a thin layer of mental outside of the main spacecraft body. However, certain portions of many satellites cannot be protected in this way, the solar panels and windows for instance. If a collision with larger pieces occurs, many of the resulting fragments from the damaged spacecraft will also be in the 1 kilogram mass range. Consequently, these objects become an additional collision risk. | 
