The greatest concern the authors raise is space debris-pieces of "junk" that orbit the earth, with the potential to cause serious damage if they collide with operational units, including the ISS.

两位作者提出的最大担忧是太空垃圾——环绕地球运行的“垃圾”碎片，如果它们与包括国际空间站在内的运行单位相撞，可能会造成严重损害。