Space junk collision. Computer illustration of an explosion on space shuttle Atlantis due to a collision with space junk. Such an impact would almost certainly be fatal for the crew. Space junk is the debris left in orbit by the countless space missions since the 1950s. It consists mainly of old dead payloads, and operational debris such as deployment equipment and optics covers. There are thousands of such objects in orbit, posing a serious threat to future space missions.