Space debris: Time to clean up the sky

Artist's impression of a space collision Fortunately, there have been very few collisions in orbit so far

The US National Research Council's report on space debris is not the first of its kind.

A wide range of space agencies and intergovernmental organisations has taken a bite out of this issue down the years.

The opinion expressed is always the same: the problem is inescapable and it's getting worse. It's also true the tone of concern is being ratcheted up.

There is now a wild jungle of debris overhead - everything from old rocket stages that continue to loop around the Earth decades after they were launched, to the flecks of paint that have lifted off once shiny space vehicles and floated off into the distance.

It is the legacy of more than half a century of space activity. Today, it is said there are more than 22,000 pieces of debris actively being tracked.

These are just the big, easy-to-see items, however. Moving around unseen are an estimated 500,000 particles ranging in size between 1-10cm across, and perhaps tens of millions of other particles smaller than 1cm.

All of this stuff is travelling at several kilometres per second - sufficient velocity for even the smallest fragment to become a damaging projectile if it strikes an operational space mission.

Gravity ensures that everything that goes up will eventually come back down, but the bath is currently being filled faster than the plug hole and the overflow pipe can empty it.

Orbital objects

Man and nature are also conspiring in unexpected ways to make the situation worse. The extra CO2 pumped into the atmosphere down the years has cooled some of its highest reaches - the thermosphere.

This, combined with low levels of solar activity, have shrunk the atmosphere, limiting the amount of drag on orbital objects that ordinarily helps to pull debris from the sky. In other words, the junk is also staying up longer.

DLR DEOS conceptual artwork The German space agency's DEOS spacecraft could capture rogue satellites

Leaving aside the growth in debris from collisions for a moment, the number of satellites being sent into space is also increasing rapidly.

The satellite industry launched an average of 76 satellites per year over the past 10 years. In the coming decade, this activity is expected to grow by 50%.

The most recent Euroconsult analysis suggested some 1,145 satellites would be built for launch between 2011 and 2020.

A good part of this will be the deployment of communications constellations - broadband relays and sat phone systems.

These constellations, in the case of the second-generation Iridium network, can number more than 60 spacecraft.

By and large, everyone operating in orbit now follows international mitigation guidelines. Or tries to.

These include ensuring there is enough propellant at the end of a satellite's life so that it can be pushed into a graveyard orbit and the venting of fuel tanks on spent rocket stages so that they cannot explode (a major source of the debris now up there).

Space junk

Artist's impression of debris in low Earth orbit, released by the European Space Agency (Esa)

The goal is to make sure all low-orbiting material is removed within 25 years of launch.

I say "by and large" because there has been some crass behaviour in the recent past. What the Chinese were thinking when they deliberately destroyed one of their polar orbiting satellites in 2007 with a missile is anyone's guess. It certainly defied all logic for a nation that professes to have major ambitions in space.

The destruction created more than 3,000 trackable objects and an estimated 150,000 debris particles larger than 1cm.

It was without question the biggest single debris-generating event in the space age. It was estimated to have increased the known existing orbital debris population at that time by more than 15%.

A couple of years later, of course, we saw the accidental collision of the Cosmos 2251 and Iridium 33 satellites. Taken together, the two events essentially negated all the mitigation gains that had been made over the previous 20 years to reduce junk production from spent rocket explosions.

There are lots of ideas out there to clean up space. Many of them, I have to say, look far-fetched and utterly impractical.

Uncertain future

Ideas such as deploying large nets to catch debris or firing harpoons into old satellites to drag them back to Earth are non-starters. If nothing else, some of these devices risk creating more debris than they would remove.

It has been calculated that just taking away a few key spent rocket stages or broken satellites would substantially reduce the potential for collision and cap the growth in space debris over coming decades. And in the next few years we're likely to see a number of robotic spacecraft demonstrate the rendezvous and capture technologies that would be needed in these selective culls.

The German space agency, for example, is working on such a mission called DEOS that is likely to fly in 2015.

Dr Robert Massey, Royal Astronomical Society: "It is a serious issue"

These approaches are quite complex, however, and therefore expensive. Reliable low-tech solutions will also be needed.

There is a lot of research currently going into deployable sails. These large-area structures would be carried by satellites and rocket stages and unfurled at the end of their missions. The sails would increase the drag on the spacecraft, pulling them out of the sky faster. Somehow attaching these sails to objects already in space is one solution that is sure to be tried.

"There are a number of technologies being talked about to address the debris issue - both from past space activity and from future missions," says Dr Hugh Lewis, a lecturer in aerospace engineering at Southampton University, UK.

"I think we are a long way off from having something which is reliable, relatively risk-free and relatively low cost.

"There are number of outstanding and fundamental issues that we still have to resolve. Which are the objects we have to target and how many do we remove? Who's going to pay?

"It is also worth remembering there are a lot of uncertainties in our future predictions. Reports that you read typically present average results; we tend to do ensembles in our simulations and some outcomes are worse than others. So, many issues still need to be addressed, but that dialogue is taking place.

"This report paints quite an alarming picture but I think we can be a bit more upbeat, certainly if we are contemplating removing objects.

"Fortunately, space is big and collisions are still very rare. After all, we've only had four known collisions and only one involving two intact objects. It's still not a catastrophic situation, and we need to be careful about using phrases like 'tipping point' and 'exponential growth'."

Jonathan Amos Article written by Jonathan Amos Jonathan Amos Science correspondent

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  • rate this

    Comment number 51.

    I propose a space-based laser decellerator.

    These objects will fall out of the sky eventually, the lower they get the faster they will fall. The solar-powered laser directs a beam against each small particle, imparting a tiny nudge against the particle's orbital velocity, just enough to start its fall before moving on to the next.
    Eventually the system would remove large numbers of tiny objects.

  • rate this

    Comment number 50.

    National interest will prevail as with climate change non-agreement and everything else. Neither China nor the US will ever agree on any restraint on their activities. The rest of us are doomed to mumble to ourselves and grumble to each other.They created the problems and they won't pay for them to be solved because their systems now depend upon defense and hydrocarbons. Satellites and oil/coal.

  • rate this

    Comment number 49.

    We are NOT above it. Mt.Everest is a tip, and now Earth orbit is congested with junk to create the Kessler syndrome of collisions multiplying collisions exponentially into a smog of particles larger than 1cm. In this atmosphere, who would venture or invest? That took no time at all to achieve in geological history. The legacy of humans is not benign.

  • rate this

    Comment number 48.

    "Gravity ensures that everything that goes up will eventually come back down" ! - This from a Science Correspondent? Ye Gods!

  • rate this

    Comment number 47.

    Lets clean the oceans first shall we? We can’t get together to complete this relatively simple task which has a huge impact on the environment yet we want to go into space and clean up 1000's of object to protect a hand full of human beings in a tin can?

    Typical selfish and greedy human response!

  • rate this

    Comment number 46.

    For larger pieces of debris there are plans for 'cubesats' that would deploy small solar sails and accelerate the orbital decay of the junk, As was pointed out earlier one problem is getting all the space launching nations to agree to a clear up,

  • rate this

    Comment number 45.

    As to Headrush's idea I believe this has been proposed but using aerogel rather than a liquid.

  • rate this

    Comment number 44.

    This is a poignant example of the "tragedy of the commons". Humans rush into a new, seemingly vast, frontier... and promptly start exploiting and polluting it. Over time, the common resource (Earth orbit) is degraded to the point of being unusable. What is clearly required is an effective international agreement (binding on countries and commercial entities) to deal with the problem.

  • rate this

    Comment number 43.

    Maybe the simplest solution here is brute force. A big and powerful enough laser on the ground could be used to vaporise those small dust like items that are so much trouble. Maybe it could also destroy larger items as well, or be used as a laser thruster to push them out of orbit.
    Such a machine might even be used for laser lifting.
    Cost- 1 - 10 B -maybe a tax on space operators could pay for it.

  • rate this

    Comment number 42.

    37, good luck in trying to point out some basics to some posters on here whose only contribution is to abuse, whinge, spout nonsense.
    Used to be a good blog until the tin foil hat wearers noticed it.
    As for China, they should be ashamed, be ironic if one of their sats gets hit by debris.

  • rate this

    Comment number 41.

    It is not dirty space, but rather a junkyard in the sky and a very serious menace. All created by man. Who has done horrible such things to the air, soil, water ( seas and oceans) . The attitude is out of sight out of mind. The greed creed industry does not care and neither do some Governments.

  • rate this

    Comment number 40.

    One of the main problems is that international law/ treaties have to be changed. Only the Country owning the satellite can remove it. As space is the 'High Frontier' many Countries would count it as an act of aggression if you can close or touched their active or defunct satellite or the remains of.

  • rate this

    Comment number 39.

    All the little boys, playing with their space toys, but no-one ever wondered who'd clean up after them... as on Earth, so it is in Heaven MWAAAAAAAAAAAAAH! Pathetic!

  • rate this

    Comment number 38.

    Spacecraft have always been at risk from 'normal' space debris,bits of meteors etc as have astronauts doing space walks.In comparison,the amount of man made 'hazards' floating around out there is miniscual.I think there might be some 'over-playing' of the problem to try and get extra money for space work full stop.

  • rate this

    Comment number 37.


    Jonathan is right, what goes up does eventually come down, at least in the context of space junk. The Earth's atmosphere extends half way to the moon and this slows everything within this distance down; it just takes a lot of time because it's very thin up there. The ISS drops a few kilometres per month because of this drag which is why they have to keep sending fuel up to boost it.

  • rate this

    Comment number 36.

    This is basically a mother telling her son to tidy his room and put the empty boxes in the bin.

    It needs doing but it is not a big problem (yet).

  • rate this

    Comment number 35.

    Tommy Lee Jones played an elderly ex astronaut, alongside a few veterans from the acting fraternity. It was he who was jettisoned into space on some part of the aircraft, to save the crew and to get them back to earth safely. It was all a lie - I don't believe it!!

  • rate this

    Comment number 34.

    In sci-fi movies the astronaut who's cord is cut and then drifts off into endless space is bunkum then, how sad for us space romantics. The poor so and so is actually stuck in some scrap metal carousel. There's me thinking he drifts off for eternity to other galaxies till one day he is discovered by an alien race who wear spandex and Dicky bow ties. First Pluto then this.Come back Dan Dare !

  • rate this

    Comment number 33.

    I am just waiting for the mantra 'we inherited all this space junk from the last Government'. Can you imagine the scrap value of all the fragments? We had an 'any old iron' merchant round today on our road - he could live like a king, if he could get his hands on it. Seriously, we are the messiest species on the planet or in the universe. Perhaps one of the black holes could hoover it up!

  • rate this

    Comment number 32.

    @F4thertime: There's no harm talking about how you'd do it, but no: it's not worth picking up now and riches and our "name" has nothing to do with it. Wait until our launch costs are lower. And Johnny Astro should not fear space debris - not when he's prepared to strap a million pounds of rocket fuel to his back for a 5 minute trip to orbit.


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