The most obvious sign that there is a lot of junk in space is how much of it has been falling out of the sky lately: a defunct Nasa satellite last year, a failed Russian space probe this year.

While the odds are tiny that anyone here on Earth will get hit, the chances that all this orbiting litter will interfere with working satellites or the International Space Station, which dodges pieces of debris with increasing frequency, are getting higher, according to a recent report by the National Research Council. The nonprofit group, which dispenses advice on scientific matters, concluded that the problem of extraterrestrial clutter had reached a point where, if nothing was done, a cascade of collisions would eventually make low-Earth orbit unusable.

“Nasa is taking it very seriously,” Mason A Peck, chief technologist for the National Aeronautics and Space Administration, said. “It is becoming an important issue.” There is a straightforward solution to the problem: Dispose of the space junk, especially the large pieces, before they collide and break into smaller ones.

And so researchers are stepping in with a variety of creative solutions, including nets that would round up wayward items and drag them into the Earth’s atmosphere, where they would harmlessly burn up, and balloons that would similarly direct the debris into the atmosphere. Also on the table: firing lasers from the ground. Not to blow things up, which would only make more of a mess, but to nudge them into safer orbits or into the atmosphere.

Just last week, researchers at a top Swiss university, the Federal Institute of Technology in Lausanne, announced that they were designing CleanSpace One, a sort of vacuum cleaner in the sky – an $11 million one – that will be able to navigate close to a satellite and grab it with a big claw, whereupon both will make a fiery death dive.

The Swiss have only two satellites in orbit, each smaller than a breadbox, but they are concerned about what to do with them when they stop operating in a few years. “We want to clean up after ourselves,” said Anton Ivanov, a scientist at the institute’s space centre. “That’s very Swiss, isn’t it?”

The space junk problem is so old and widely acknowledged that it even has a name: the Kessler Syndrome. In 1978, Donald J. Kessler, who led Nasa’s office of space debris, first predicted the cascade effect that would take place when leftover objects in space started colliding.

Today, Kessler is retired in North Carolina but still contemplating the issue – and the need to clean up. “The sooner they do it, the cheaper it will be,” he said. “The more you wait to start, the more you’ll have to do.” Today, with so many items whizzing around at more than 17,000 miles per hour and shattering as they crash, the threat to working satellites, which are vital to hurricane tracking, GPS systems and military surveillance, has grown more immediate. Three years ago, a derelict Russian satellite slammed into an Iridium communications satellite, smashing both into tens of thousands of pieces.

The Air Force currently tracks 20,000 pieces of orbiting space junk, which includes old rocket parts and dead satellites.

Perilous orbit

For now, the risk is real but manageable Satellite operators can dodge the big debris and armor their satellites to withstand impact with smaller pieces. But eventually, if not cleaned up, low-Earth orbit would become too perilous for people and satellites. “It will be a huge risk for an astronaut to go to space,” said John L Junkins, a professor of aerospace engineering at Texas A&M University, adding: “No one will insure a space launch.”

The US has about 500 pieces of large space junk, Junkins said, and Russia about twice that number. “I’m talking about going after things the size of a Greyhound bus,” he said. “Absolutely, this is the heart of the problem.” Taking down five or six of the large intact objects each year would be enough to halt the cascade effect, he said. Eliminating 10 a year would quickly reverse the trend.

Nasa has started financing research to come up with some solutions. Raytheon, for one, is studying whether a high-altitude balloon might be able to carry a machine that would essentially shoot puffs of air into the path of orbiting debris. Even that slight increase in atmospheric drag could force junk to fall back to Earth. “It actually doesn’t require much,” said Peck, Nasa’s chief technologist.

Nasa just gave $1.9 million to Star Technology and Research, a small company in South Carolina, to develop and test technologies for a spacecraft it calls the ElectroDynamic Debris Eliminator – EDDE, for short. Powered by a 6-mile-long wire – make that ‘space tether’ – that generates energy as it is pulled through the Earth’s magnetic field, EDDE would sidle up to a piece of junk, whip out a disposable net to catch it and then move to a lower orbit, where air friction would coax the item to re-enter the atmosphere. EDDE, staying in orbit, would then move on to its next target.

Jerome Pearson, the president of Star Technology, said it would take only a few years and a few hundred million dollars for a fleet of EDDEs to clean up the near-Earth neighbourhood. (Others suspect that it would take longer and cost more.)

Technology is just one hurdle. International politics might be a more serious one. Space junk, even if it is just junk, still belongs to the nation that put it there. So if the United States tried to lasso part of a spent Russian rocket, Russia would most likely protest. Many nations would certainly worry that a ground-based laser capable of pushing satellites around would also be wielded as a weapon.

Meanwhile, the space junk problem will not be solved unless everyone launching rockets stops adding to it. The US has largely done that: All new satellites are now accompanied by plans for how to bring them safely out of orbit.

Last month, secretary of state Hillary Rodham Clinton suggested setting up a code of conduct for nations to follow, but that may be more easily said than done. European countries have also been putting together a set of ground rules, but the United States called them too restrictive.

Junkins of Texas A&M said the US should not wait for new international agreements, but instead follow the example of the Swiss in cleaning up after itself. “The US alone could reverse the growth by tackling the several hundred things that we’ve put there that are our responsibility,” he said. “That gives us the moral and technical high ground.”