Space Junk : Removal Experiment Will Harpoon & Net Debris in Orbit


The first experiment designed to demonstrate active space-debris removal in orbit has just reached the International Space Station aboard SpaceX’s Dragon capsule.

The RemoveDebris experiment, designed by a team led by the University of Surrey in the U.K. as part of a 15.2 million euro ($18.7 million), European Union (EU)-funded project, is about the size of a washing machine and weighs 100 kilograms (220 lbs.).

It carries three types of technologies for space-debris capture and active deorbiting — a harpoon, a net and a drag sail.

It will also test a lidar system for optical navigation that will help future chaser spacecraft better aim at their targets.

“For this mission, we are actually ejecting our own little cubesats,” Jason Forshaw, RemoveDebris project manager at the University of Surrey, said last year. “These little cubesats are maybe the size of a shoebox, very small. We eject them and capture them with the net.”

A dragsail to slow a satellite so it falls controlled from space is one of several space junk removal concepts to be tested on on the RemoveDebris mission launched into orbit on a SpaceX rocket April 2, 2018.

Credit: University of Surrey

He said the team decided to carry up their own pieces of space junk, due to legal issues that don’t allow the manipulation of space objects that belong to someone else, even if the objects are no longer functional.

The main spacecraft will be launched later this year from the International Space Station using the commercial cubesat deployer operated by Houston, Texas-based NanoRacks. Once the spacecraft reaches a safe distance from the space station, it will eject the two cubesats. After that, the chaser spacecraft will deploy the net, aiming to capture the cubesats.

Forshaw said that for the purpose of this experiment, the chaser spacecraft won’t be connected to the net with a tether, as it would be in a real mission.

“There [are] a lot of problems that could occur with a tether,” he said. “For example, the cubesat could bounce back and hit your main satellite.”

The RemoveDebris mission, newly arrived at the International Space Station, will practice netting and harpooning space junk.

Credit: Max Alexander

The space junk harpoon, built by Airbus Defence and Space in the U.K., will be later fired into a fixed target that will be extended from the main satellite on a boom.

After it completes the harpoon, net and lidar experiments, the RemoveDebris spacecraft will deploy the drag sail that will speed up its deorbiting process.

“We are testing these four technologies in this demonstration mission, and we want to see whether they work or not,” said Forshaw, referring to the harpoon, net, drag sail and lidar. “If they work, then that would be fantastic, and then these technologies could be used on future missions.”

The RemoveDebris mission will fire a net at a target satellite (shown here ensnaring its target) to test how to drag space junk from orbit.

The RemoveDebris mission will fire a net at a target satellite (shown here ensnaring its target) to test how to drag space junk from orbit.

Credit: University of Surrey

The cubesats captured in the net will deorbit naturally within a few months, Forshaw said.

“The absolute maximum for which it stays up there would be one year,” he said. “These things at low altitudes do come down very quickly. We are not going to contribute to any further space debris.”

Some 40,000 space objects — the vast majority of which are defunct satellites and fragments from collisions — are currently being tracked by the U.S.-based Space Surveillance Network.
It is estimated that some 7,600 metric tons (8,378 tons) of junk hurtle around the Earth at speeds of up to 17,500 mph, threatening functioning spacecraft, according to a statement from the University of Surrey.
“It is important to remember that a few significant collisions have already happened,” Professor Guglielmo Aglietti, director of the Surrey Space Centre at the University of Surrey, said in the statement.
“Therefore, to maintain the safety of current and future space assets, the issue of the control and reduction of the space debris has to be addressed. “

International guidelines exist for satellite operators to ensure their spacecraft are removed within a reasonable amount of time after a mission ends.

However, experts agree that without active removal technologies, the space around Earth might become unstable.

The world’s space agencies estimate that five large, defunct satellites need to be removed from low Earth orbit every year to help prevent the Kessler syndrome — the unstoppable cascade of orbital collisions predicted by NASA scientist Donald Kessler in the late 1970s.


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