The humble harpoon will be used to snare dangerous space debris as the European Space Agency attempts to clear up Earth’s orbit.
A halo of space junk circling the Earth, left by decades of launches, is threatening working missions with catastrophic collision, and Esa’s Clean Space project has investigated numerous options to clear up the mess including nets, clamping systems and robotic arms.
But the agency has decided to back a tethered harpoon based system after promising initial investigations by Airbus Defence and Space in Stevenage, UK, and has invited tenders to build and test a prototype of the concept.
Esa is hopeful of adopting the concept for its e.DeOrbit mission in 2021, which will see a space vehicle use sophisticated sensors and autonomous control to identify and home in on a target – potentially of several tonnes and tumbling uncontrollably – and reel it in and steer it down into a controlled burn-up in the atmosphere.
More than 17,000 trackable objects larger than a coffee cup are known to be circling the Earth, posing a serious threat to space missions and even a one centimetre-wide nut could slam into a valuable satellite with the force of a hand grenade.
The only way to control the debris cloud across crucial lower orbits is to remove large items such as derelict satellites and rocket upper stages before they are involved in a collision or explode due to leftover fuel or partially charged batteries heated up by sunlight.
Harpoons rely on three physical actions to ensure safe and clean grasping: a high-energy impact into the target, piercing the structure and then reeling it in.
In the Airbus research a prototype harpoon was shot into representative satellite material to assess its penetration, its strength as the target is pulled close and the generation of additional fragments that might threaten the e.DeOrbit satellite.
As a next step, ESA plans to build and test a prototype by investigating all three stages of harpooning through computer models, analysis and experiments, leading to a full hardware demonstration.