We are surrounded by waste. Our rubbish is fly-tipped into railway cuttings, buried in landfill sites, and dumped at the bottom of oceans and rivers. Despite increasing recycling rates, we live on a planet awash with trash.
And in the latest manifestation of our throwaway society, we’re starting to clog up space too, or at least that slither of it regularly visited by rockets, satellites and space stations.
Space junk is a growing problem, and one that experts now accept could put future space exploration at risk. Since 1958, around 6000 satellites have been launched into space, and of those only around 800 are currently operating.
In other words, thousands of pieces of this spent space hardware are currently orbiting the earth – unused, unwanted, and dangerously in the way. And they’re not alone.
Spent booster stages, discarded nuts and bolts from the construction of the International Space Station (ISS), and lost astronaut gloves and cameras all add to a floating cosmic rubbish tip.
Only last November, a spacewalking astronaut, busy making repairs to the ISS, watched helplessly as her high-tech toolbox slipped from her grasp and floated off into orbit.
According to Eugene Stansbery, Program Manager of NASA’s Orbital Debris Program Office, a large proportion of space junk comes from abandoned spaceships that explode and break up, scattering debris far and wide.
"During much of the space age, operators left energy sources on board derelict spacecraft and rocket bodies, in the form of residual fuel left in thrusters, or compressed gas, or a battery that was not discharged properly," he says. "Any stored energy left on a spacecraft can fail over time and cause an explosion."
Even more of the growing cloud of space junk may be made up of stamp-sized fragments of frozen nuclear reactor coolant, leaking from old satellites. It all adds up to a lot of trash.
"The US military maintains a worldwide network of sensors which tracks and catalogues individual orbital debris objects," says Stansbery. "This network is capable of detecting objects down to about 10 cm diameter in low Earth orbit and down to about one metre diameter at geosynchronous (higher) altitudes. The network is currently tracking about 13,000 objects."
In fact, estimates suggest that there might be over one million pieces of man-made junk currently blanketing the strip of space directly above our heads, if you include tiny items like paint chippings from spaceships. Many will be harmless, but the larger ones tracked by the US military pose a real risk to future space missions and to the lives of any astronauts on board.
And in fact, collisions between spacecraft and space junk already occur with alarming regularity. NASA has been forced to replace windows on various Space Shuttles on at least 80 occasions, thanks to damage from space junk.
Satellites that have been in orbit for years and eventually fall back to Earth are found to be peppered with tiny craters, the result of thousands of collisions with paint chips and small fragments of solid fuel.
NASA has re-routed Space Shuttle flight paths on eight occasions to avoid more dangerous pieces of space debris. The International Space Station sometimes has to manoeuvre around space junk, too.
That’s not as easy as it sounds. To think of space debris floating around like so much millpond driftwood is a major misconception. When a paint chip hits the Space Shuttle, it’s doing so at a relative speed of about 21,600 miles per hour. That’s like being hit by a rifle bullet.
Small but deadly
And when a pea-sided ball of frozen fuel hits it, it’s the equivalent of a collision with a 400lb safe travelling at 60mph. In other words, even quite small particles can do extensive and potentially fatal damage to a spacecraft, especially if they hit a critical component like the flight computer.
That has yet to happen, but scientists are concerned that one day it might. "There is a real threat to future missions," says Eugene Stansbery. "Fortunately, the current threat is still relatively small, but it’s growing."
Some dismiss the threat. In his book, Do your ears pop in space?, former astronaut Mike Mullane says, "You have to remember these objects are swirling around in a huge sky. The chances of a collision are very, very small."
But according to NASA, the threat is small at the moment because the Space Shuttle and ISS operate at very low altitudes where there is less debris. Future space missions may aim a lot higher.
And a very real fear is that high-velocity collisions between large pieces of spent rockets and satellites will increase the amount of junk in space exponentially over the next few decades.
Space junk even presents some threat to those of us with our feet firmly on the ground, albeit a small one. Most space junk that re-enters the Earth’s atmosphere burns up before it reaches the ground. One exception was Skylab, an early US space station that was launched in 1973 and fell to Earth six years later. Nobody was hurt, but dangerous debris rained over a large expanse of the Australian outback.
In 1996, meanwhile, wreckage from a Russian spy satellite re-entering over the Pacific Ocean passed dangerously close to an airliner carrying 270 passengers.
Environmental problems we have created here on Earth are increasingly finding a mirror in those we are creating hundreds of miles above it. Eugene Stansbery says measures are being taken to clean up our act. Space agencies are being educated about the problems of explosions in spent rockets and spacecraft, for example, and scientists are trying to find ways of removing derelicts satellites from orbit.
But the difficulties of cleaning up space seem all too familiar. Like the Amazonian rain forests and Arctic ice flows, space seems a long way away. Clearing the mess properly would be costly and complicated. For the time being at least, our great cosmic rubbish tip will only get bigger.
Space Junk Facts:
The oldest piece of hardware still in orbit is probably the Vanguard 1 satellite, launched in 1958.
In its first ten years of operation, the Russian Mir space station released 200 objects – mainly rubbish bags – into orbit.
About 2,300 pieces of tracked debris came from just one explosion, a Chinese anti-satellite missile test conducted in 2007.
When the upper stages of the Pegasus rocket, launched in 1994, exploded two years later, it created a cloud of some 300,000 fragments of space debris, of which 700 were big enough to be catalogued.
Items of space junk have included at least one camera, one glove, and one toothbrush. Oh, and now one toolbox.