In 2021, as part of its Clean Space Initiative, ESA plans to launch the e.DeOrbit mission. The aim of this mission is to clean up the important polar orbits between altitudes of 800 to 1,000 km (500 to 625 mil) that face the prospect of becoming unusable due to the increasing buildup of space debris. The ESA has now announced plans to examine the potential for the mission to use space harpoons to capture large items, such as derelict satellites and the upper stages of rockets.
The ESA has previously revealed it is considering a number of approaches to meet the challenge of capturing and securing space debris. These include snaring the debris in a net, securing it with clamping mechanisms, or grabbing hold of it using robotic arms. Another option is a tethered harpoon, which would pierce the debris with a high-energy impact before reeling it in.
Such an approach wouldn't be applicable for smaller debris, but is aimed at reeling in uncontrolled multitonne objects that threaten to fragment when colliding with other objects, resulting in debris clouds that would steadily increase in density due to the Kessler syndrome.
The ESA says the space harpoon concept has already undergone initial investigations by Airbus Defense and Space in Stevenage, UK, whose preliminary design incorporates a penetrating tip, crushable cartridge to help embed it in the target satellite structure and barbs to keep it sticking in so the satellite can then be reeled in.
The initial tests involved shooting a prototype harpoon into a satellite-like material to assess its penetration, the strength of the harpoon and tether as the target is reeled in, and the potential for the target to fragment, which would result in more debris that could threaten the e.DeOrbit satellite.
The ESA now plans to follow up these initial tests by building and testing a prototype "breadboard" version of the harpoon and its ejection system in the hope of adopting it for the e.DeOrbit mission. The project will examine the harpoon impact, target piercing and the reeling in of objects using computer models and experiments, ultimately leading up to a full hardware demonstration.
The space agency has put out the call for bidders to compete for the project contract.