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 31.

    Space Junk, Hmm...

    There is nothing new about this story, I sense that we are being softened up by the Space Lobby and ESA for either more UK taxpayers cash or the another grand and ultimately open ended and expensive project.

    That said, it's time to revive the polluter pay's principle, the Space Industry can easily afford to clean itself up, if their £7.5 billion UK figure is true.

  • rate this

    Comment number 30.

    I'm confused as to how you landed the job of science correspondent if your basic knowledge is so poor that you think 'what goes up must come down' is a scientific law. This is pop culture nonsense. Objects will generally stay in gravitational orbit indefinitely, and can even drift further away.

  • rate this

    Comment number 29.

    Must be worth a private company getting involved - surely there is a profit to be had? Rare metals etc.

    In any case, space exploration needs private ventures to 'take-off'. When there is profit (greed) to be had out there through mining etc, then we will truly explore at least our own system.

  • rate this

    Comment number 28.

    @headrush: I've put your idea forward to NASA and others whenever this subject has come up, except I proposed tarry goo, and thrusters to shift the goo ball's orbit each time it swept a path clear. It can catch the tiny bits (magnetic or not) and leave the bigger ones to be avoided.

  • rate this

    Comment number 27.

    @25, Rob
    The point is waste not want not; is it not worth picking up after yourself? I thought a good name was better than riches.
    500,000 nuts and bolts sized objects and the numbers are off the chart at 22k not 16k for larger objects.
    Manmade space debris is much more dense than most meteors.
    Johnny ought not worry about friendly fire?

  • rate this

    Comment number 26.

    I thought Space Custard was already the name of the only thing capable of stopping Grey Goo.

    Three predictions:
    a.Lasers will push the debris closer to the Earth and waste it all. 2.The next generation of astronauts sadly wont be bin men. d.Space custard will save us all!

    HG wells perhaps we are ready for a space junkyard wars instead of science fiction.

  • rate this

    Comment number 25.

    Media over-hype of a science paper. Again.
    Recyclable? Really? THINK! Is it easier to recover a few ounces of gold from space or dig a new hole in the ground?
    The article picture suggests we should be seeing shadows on the ground as this space junk passes over. 16000 objects? Golly gee. 1000s of meteorites hit Earth EVERY day. Why is Johnny Astronaut now afraid of a few nuts, bolts, and solenoids?

  • rate this

    Comment number 24.

    I remember Salvage 1 a 1979 TV series about a bunch of chest beaters making a spacecraft from junk and taking it into orbit to retrieve valuable rubbish.

  • rate this

    Comment number 23.

    I like the custard approach headrush proposes although in the scheme of things it looks trifling.

  • rate this

    Comment number 22.

    Dear BBC Team and readers, as a participant of Singularity University '11 at NASA Ames, I would be very happy to share with you my video about space debris :

    I hope you will like it and feel free to publish it and share it.

  • rate this

    Comment number 21.

    1) Some sort of remote control MAGNETIC satellite that can be directed into the orbit of junk or high-density particulates. When it is massive enough, we bring it down to earth.

    2) @Simonm - BRILLIANT: all the material up there Is a resource. Consider China's interest in pulling an meteoroid into orbit to explore/mine it.

    2) @headrush "space custard" there ARE solid gels like this. How to contro

  • rate this

    Comment number 20.

    Dear Washington Post Team and readers, as a participant of Singularity University '11 at NASA Ames, I would be very happy to share with you my video about space debris :

    I hope you will like it and feel free to publish it and share it.

  • rate this

    Comment number 19.

    Outstanding, another report telling us space is full of defunct junk, well duh, we already know this. How about 'experts' stop wasting money on what we already know and come up with a way of reclaiming the waste to reuse on new junk to be sent in to space.

  • rate this

    Comment number 18.

    What's wrong with space debris? Shouldnt we be talking about reviving MANNED SPACE, not wasting time with this bull?

  • rate this

    Comment number 17.

    Sounds like we need a good vacuum cleaner.

  • rate this

    Comment number 16.

    Maybe we will see the first 'space trawler' a solar driven craft with a huge mesh trawl net attached..we may even bag a few aliens !

  • rate this

    Comment number 15.

    It really ought to be used, not burned up. Why aren't we manufacturing in space yet? All the problems of high gravity are left behind in orbit.

  • rate this

    Comment number 14.

    Isn't this just like us humans , we have to touch everything!

  • rate this

    Comment number 13.

    How about a Moon Base Recycle Center?

  • rate this

    Comment number 12.


    Surely those responsible will be charged with building an outer space stationed recycling plant and planning collection before investing any more effort on other endeavours.

    This could be a good idea. After all, it will provide us with a few benefits:
    1. Gets rid of the space junk already there.
    2. Prevents build up of more space junk.
    3. Building platform for future space missions


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