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.