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Space harpoon could tackle satellite debris problem

UK engineers have developed a space harpoon that could help tackle the growing problem of space debris orbiting the Earth.

The team from satellite firm Astrium wanted to create a relatively simple and therefore reliable way to capture some of the larger pieces of junk from among the thousands currently in orbit, which pose a serious risk to functioning satellites.

A craft carrying a pneumatic launcher would fire a harpoon into its target and use a tether to drag it out of orbit and down into the atmosphere where it would burn up, in order to prevent it from colliding with other objects.

It makes sense to target bigger objects, said Jaime Reed, project leader and specialist mission systems engineer at Astrium, because they have a higher chance of causing collisions and any impacts would produce a large increase in the number of smaller fragments.

‘It’s more cost effective to go for the big objects unless you can come up with a way of sweeping up lots of small ones,’ he told The Engineer.

He added that NASA studies suggested that around 10 to 15 large objects of over one tonne in mass needed to be removed from orbit in the next five to 10 years otherwise collisions would cause the number of small fragments to increase exponentially, making the problem much harder to deal with.

The idea of the harpoon came from the mechanism that will be used by the Rosetta space probe that is currently en route to intercept and attach itself to a comet between Earth and Mars.

The point of the spear is under 10cm in length to prevent it from travelling through whatever item it is fired at and piercing a fuel tank or damaging internal mechanisms that could create more debris.

There are around 22,000 trackable objects larger than 10cm in diameter in orbit, 94 per cent of which are debris: disused rocket stages, old satellites and fragments of collisions between these items.

Authorities also estimate there are around 700,000 objects larger than 1cm and 170 million objects larger than 1mm, all of which can cause damage to working satellites and spacecraft.

Numerous ideas for tackling the space debris problem have been put forward in recent years, including robotic arms, nets and sweepers, and scientists are due to meet next week at ESA’s space debris conference in Germany to discuss different options.

But Astrium missions systems engineer Andrew Ratcliffe pointed out that the cost of developing overly complicated solutions could be higher than the cost of doing nothing.

‘The problem with nets is that the gauze could create smaller particles and break bits off,’ he said. ‘One of the big requirements is not creating more debris than you remove.’

The space debris issue has received growing publicity in the last few years and space authorities have introduced guidelines limiting the time that satellites can remain in orbit, forcing manufacturers to devise ways to pull them down after 25 years.

Government satellites and spacecraft are routinely moved out of the path of suspected incoming debris but the space agencies have yet to firmly schedule any cleanup missions to remove existing objects, although ESA has announced intentions for a Space Cleanup initiative to start in 2015.


Readers' comments (10)

  • Extra drag is what you need. Something you fire at the junk that adheres or even punctures, or envelopes in a net that is attached to a large fluffy long tail. Something that open up like a christmas tree of umbrella to have a lot more drag than the object. This tail will gradually lower the orbit through drag and it will spiral in. The ship that attaches the 'tail' needs to be maneuverable and to have a number of tails to attach to many objects in succession, and when it is done, to have a small de-orbit thruster to make it spiral in.

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  • This might work for objects in a low orbit, but the lack of any significant atmosphere would make this a non-starter for objects in a higher orbit. Attaching a long conductive tail might help slow the satellite down due to the electromagnetic effect but simply adding a 'tail is unlikely to do much.

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  • It's not just a tail - the craft carrying the harpoon launcher would use thrusters to pull the object out of orbit.

  • I'd like to see something as in moonraker, when the space shuttle gets gobbled up. It sould be easy match the course and speed of an object since it won't be changing too much.

    Then, I know it is more expensive, but perhaps send the junk to the moon. One day we will build there are there will be lots of scrap metal to recycle. Instead of bringing raw material from earth.

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  • About time, thirty years or more too late. Irresponsibility of dumping material/trash in orbit or letting artificial objects fall back to earth. Having messed up a lot of the planet, start on its surroundings!

    Why bring debris/objects back to earth, why not accumulate it in one or more orbiting recyclables cache?

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  • I whole heatedly agree why spend millions getting that stuff into orbit just to bring it down push it all to a lagrange point and store it there and create a large smelter to reclaim all the materials in the space junk. Most of it cost thousands or millions to put up there, just use the sail to push it into a junk yard, then whe in the future we need some material that might be inthe junkyard we can recycle it rather than spread it across multiple countries and spread poisonous hydrazine which is the thruster fuel across the world we live in.

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  • The simplest way to get rid of debris is to have a net connected to two spaceships that will fly around and catch the trash..then on the way back to earth they will bring down the debris which will burn up in the atmosphere. Done and done!

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  • "...have a net connected to two spaceships that will fly around and catch the trash" The article suggests that they already thought of that and discounted it!

    Randomly trawling space would take a very long time anyway - it's an awfully big place, even just the bit we are interested in. Think about trying to trawl the oceans of all floating debris within 10m of the surface (how many ships and nets, what size to cover the 361 million sq km) Now think of space where we are interested in orbits heights from 2000 to 36000km all round the earth and you get a scale of the problem.

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  • Net-based solutions are being pursued by other groups such as the German Aerospace Center (DLR), but this tends to focus on capturing individual objects rather than sweeping up a whole lot.

  • Correction to my previous post - the lower limit of Low Earth Orbit (LEO) is around 250 km. 2000 km is the upper limit of LEO. GPS satellites are in Medium Earth Orbit at 20,350 km and Geostationary orbit is 35,786 km.

    The gross volume of space within the Low Earth Orbit, where the problem is greatest, is about 1240 billion cu.km. So the only practical way to collect space debris has to be selectively!

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  • geosynchronous orbits (which are high and above drag)tend to have less debris because the items placed there were mainly communications satellites, and none of those has collided or fragmented.

    The lower orbits have debris and the drag varies with altitude and the weather in space. Many of them will decay in a few years, but higher ones will last for centuries. careful targeting and attaching a harpoon, whereupon retrograde force is applied to make the orbit decay quickly is viable. The need for thrust shortens the active life of the hunter-killer bird, which must spend thrust to maneuver to and then to drag down the target. An adhesive tether with a long fluffy tail - possibly 100 meters or more, would produce drag that would make the orbit decay rapidly. The rate would depend on the height of the orbit and the length and number of these draggy tethers attached. It may not work at higher orbits, but if the bird had a low point in it's orbit, the drag would work.

    Nets may not work, high relative velocities might cause punch through, but a tough fiber, like spider webbing, would tolerate elongation and allow debris to be accumulated, piece after piece as they were hunted down and enmeshed - the full net then being de-orbited by thrust

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  • Why not use a giant funnel with an exit tube that can be moved in various positions. It would be easy to construct in such a way that it would unfurl in orbit, then small objects would be caught inside it and the bottom of the cone would be directed in a particular direction. The items caught would go either into space or could be redirected back to Earth to burn up.

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