Space junk: what goes up …

Posted: September 26, 2011 - 11:35 , by Ian Nicklin
Natural History, What's New | Comments (0) | Comment

The ability to place man-made devices – satellites – in orbit around our planet has revolutionized the ways in which we communicate and allowed us to study our planet, our solar system and our universe in ways not otherwise possible. In fact, satillites are so useful that there is a growing lack of space in outer space. Our planet is surrounded by literally tens of millions of pieces of man-made material ranging from dust and flecks of paint, to multi-tonne satellites and spent rocket components. You might not think that a fleck of paint is much to worry about, but if you factor in the speed at which objects need to travel to maintain orbit around Earth you may have a change of heart.  Moving at speeds in the order of many kilometers per second even a tiny chip of paint can do a lot of damage!

Damage caused by a small paint chip.

An impact crater on one of the windows of the Space Shuttle Challenger following a collision with a micrometeoroid during STS-7. Photo Credit: NASA

There is growing concern that the amount of debris orbiting our planet is reaching a critical mass – it may start to seriously impinge on a satellite’s lifespan or even threaten manned space missions due to potentially catastrophic collisions. And while NASA maintains an accurate inventory of the amount and size of this material, there’s also a good deal of debate over just how we are going to clean up our cosmic backyard.

You may be asking, what happens when these things come back down to Earth? Depending on the location of the object, it’s orbit may last for decades, even centuries. Vanguard 1 was launched in the 1960s yet it’s still up there and won’t be coming down for another 240 years!

Most other satellites however have a much shorter life. The Upper Atmosphere Research Satellite (UARS ), which fell to Earth on Friday, September 23, has only been in orbit for about ten years. In some instances the various space agencies responsible for satellites are able to perform a controlled re-entry, causing the object to burn up over uninhabited areas as they plummet to Earth’s surface. In other instances – such as with the UARS – they are unable to accurately predict just where pieces that may survive re-entry will land. The window for debris from UARS was anywhere from 56 degrees north latitude to 56 degrees south latitude. In other words from the tip of Terra del Fuego to Hudson’s Bay.  It isn’t the first instance of falling satillites either…in 1979 the 77.5 ton Skylab (more than ten times the size of UARS) crashed to Earth, scattering debris across the Australian outback.

The liklihood of being hit by falling space junk is low (estimated to be several thousand to one against) however there is one reported case. In January 1997 Lottie Williams, living in Tulsa, Oklahoma, was apparently struck by a piece of space debris. Thought to be a hoax by many, her story was confirmed by NASA and the object was identified as a piece of woven fabric from a rocket fuel cell. Very fortunately it was small and weighed very little.

So, will there be more space junk falling to Earth in the future? The simple answer is yes. With a renewed interest in space exploration and an increasing demand for satellite communications technology, we will be launching more and more objects into outer space. Planning for the re-entry of many of these vehicles will most likely become a standard part of future launch strategies and mission out-comes.