Chain reaction of debris generation by collisions in space - a final threat to spaceflight?

Abstract The number of man made objects orbiting around the earth has already reached a level that the collision risk has become a serious consideration for all larger spacecraft. However, a far greater threat to spaceflight in general may emerge: the debris generated by collisions in space can initiate a self sustained chain reaction which could lead to the formation of an artificial debris belt. Spaceflight could then become impossible in certain altitude regions for many centuries. As a result of the detailed analysis, it was found that the population of larger space objects is of decisive importance for the fragment generation by collisions. The critical population for the setting-in of a chain reaction is only about 2 to 3 times the current population and could be reached within 20 to 50 years, if spaceflight activities will be continued as in the past. Therefore, within this time frame the number of larger space objects must be limited, e.g. by active controlled reentry manoeuvres after the end of their missions. In addition to that it could become necessary in the future to remove larger objects already in orbit, especially in the critical higher altitudes, in order to reduce an unacceptable or critical high population level.