Space junk refers to man-made trash floating in space including spent rocket stages, malfunctioning satellites, spanners, nuts, bolts, and small parts of spacecraft.
The United Nations Committee on the Peaceful Uses of Outer Space defines space debris as “all man-made objects, including fragments and elements thereof, in Earth orbit or re-entering the atmosphere, that are non-functional”.
More than 17,000 objects of a size greater than 10cm reside in Earth’s orbit.
New research identifies more than 60 objects at a height of about 850km from earth, and two thirds of those weigh more than three tonnes each and moving at speeds of up to 7.5km/s.
More satellites in orbit tend to breed more space junk, as illustrated by the 2009 collision of a defunct weather satellite and an Iridium telecom satellite, which left thousands of additional junk pieces of debris in orbit.
NASA researchers say there could be a relatively cheap solution for dealing with this “space junk”: aim a medium-powered laser into space and push any objects on a collision course out of harm’s way.
“Spacecraft are supposed to have enough ‘gas’ in their tanks to propel them downward toward the atmosphere when their life cycle is concluded,” say Stanford researchers Lawrence Wein and Andrew Bradley. “But international compliance, while perhaps greater than 50 percent, is not extremely high.”
“It appears that if full compliance of the 25-year spacecraft de-orbiting guidelines can be achieved within the next few decades, then the lifetime risk from space debris may be sustainable at a tolerable level,” write the authors. They call for focusing future policy on achieving full compliance with rules to get equipment out of orbit, and making it taboo to intentionally blow up equipment already in orbit.
Debate about the most appropriate method to deal with space debris is ongoing on many science forums. Space junk is of growing concern but the good news is that scientists are working on solutions to reduce the debris in space so that International Space Station and useful satellites are not destroyed accidentally.