For the past forty years or so, we have heard much about the accomplishments of the first people to flyin space, orbit the earth, land on the moon, and live and work on a space station. We often receive newsabout the latest photographs from space telescopes and probes sent to explore distant planets. However,there is one aspect of the human exploration of space about which we hear very little, even though itmay eventually become a serious problem for future space missions. This is the phenomenon of spacejunk. Almost every time a rocket or satellite is launched into space, bits and pieces have fallen off orhave been deliberately jettisoned. These rocket pieces now form a vast orbiting array of debris.Tiny particles of debris, no larger than a marble, are estimated to number in the millions! Theseparticles include fragments as small as the chips of paint that flake off rockets because of extreme heatand cold. However, even these minuscule bits of matter can pose a problem because each particle istraveling at about 18,000 miles per hour! They can scratch and damage a space shuttle’s windows,which are generally replaced after each mission for this very reason.Slightly larger pieces of matter, up to the size of a small grapefruit, are estimated to number about100,000. Pieces of even larger debris are so potentially dangerous that the U.S. Space SurveillanceNetwork monitors each and every one of them. By 1998, the network was tracking approximately9,000 such objects and is expecting a huge increase in years to come as more and more satellites arelaunched. The network trackers assign a number to each large piece of space junk, and they know itslocation at all times. If a piece falls to Earth, as all of them eventually will, the network can cross it offthe list. We don’t need to worry much about most of these objects because they burn up from thefriction of reentry into Earth’s atmosphere. However, very large pieces could survive reentry and crashsomewhere on Earth.
