Europe plans a space claw to capture debris in orbit | Science

By Daniel CleryDecember 1, 2020 at 2:00 p.m.

The European Space Agency (ESA) today finalized a contract to launch a mission in 2025 that will be the first to capture and clear a piece of space debris in orbit. The ClearSpace-1 mission, built by Swiss start-up ClearSpace, will attach itself to a piece of debris the size of a washing machine, grab it with a four-armed claw, and escort it to a lower orbit where the duo will enter the atmosphere and burn.

Darren McKnight, a space debris expert at tech company Centauri, praises ESA for being one of the few agencies taking action. But he is concerned about the slow progress in removing orbital debris, which he says will increasingly threaten active satellites and astronauts. “If we don’t start quickly, we’re going to have big problems,” he says. “We have to take baby steps quickly.”

Space around the Earth is increasingly congested because satellites are traditionally left in orbit at the end of their useful life. In higher orbits, they can stay there for hundreds or even thousands of years. Another major source of space waste is discarded rocket stages, if not blown into the atmosphere after use.

The 5,500 launches over 60 years of the space age have left 23,000 objects larger than a grapefruit in orbit. There are several million smaller objects that cannot be tracked. At the speed at which things move in low earth orbit, even a collision with a stray bolt can be catastrophic. But larger objects are of more concern, as they can collide and create cascades of smaller collisions. This is what happened in 2009, when a working Iridium communications satellite collided with a dead Russian military satellite, generating thousands of new traceable debris and many smaller ones. Two years later, the International Space Station had to move to avoid the debris from the crash; in 2012, some went to less than 120 meters.

ClearSpace starts with something simple. In 2013, one of ESA’s Vega rockets launched a payload of two satellites. The 112-kilogram payload adapter that connected ESA’s PROBA-V earth observation satellite to the launcher has been in orbit ever since, between 664 and 800 kilometers. It is now in the ClearSpace reticle. “It’s a simple structure, like a small satellite,” explains Muriel Richard-Noca, chief engineer at ClearSpace.

The challenge is to design an imaging system that can quickly and autonomously characterize the object before the claw catches it, says Luisa Innocenti, head of ESA’s Clean Space Office. “You don’t know how it moves and the only way to find out is to go up and watch,” she said. Innocenti says she and her colleagues have also argued over the catching technique: gripping with pliers requires a close approach, while catching in a net can be done from a safe distance – but must work first. times. Richard-Noca says ClearSpace went with the hot shoe because you may have multiple attempts. “You can repeat the whole procedure. This gives us the flexibility we need for this first mission, ”she says.

Other missions test similar ideas with debris they create themselves. An EU-funded mission called RemoveDEBRIS, designed by the University of Surrey, flew in 2018 and tested a harpoon and net on small deployed targets. His attempt at a trailed sail, to accelerate his descent into the atmosphere, failed to deploy, so he is advancing more slowly towards re-entry. In March 2021, the Japanese company Astroscale plans to launch a privately funded mission called ELSA-d. During the mission, a service vessel will release a target vessel with a ferromagnetic docking plate and capture it using magnets. That’s an option if future satellite designers embrace the idea, but not for legacy waste.

ClearSpace has bigger plans. “We will gradually move to larger and more ambitious goals,” says Luc Piguet, CEO of ClearSpace, as well as missions that may have multiple goals to reduce costs.

It’s going to be necessary, says Hugh Lewis, who models space debris at the University of Southampton. He points out that ClearSpace-1 will spend 100 million euros (86 million euros from ESA) to clean up just over 100 kilograms of space waste. At that price, Envisat – a former ESA satellite, the size of a bus, 8,000 kilograms and Earth observation – would be prohibitively expensive to take down, even though Lewis says it’s is “the riskiest object in orbit”.

At the International Astronautical Congress in October, McKnight presented an analysis of the 50 Debris of Most Concern in Low Earth Orbit. He asked 11 teams around the world to come up with their top 50 list based on criteria such as mass, expected orbital life and proximity to operating satellites. He then compiled a composite list. The first 20 items on the list are stages of Soviet and Russian rockets launched between 1985 and 2007 and left in congested operational orbits. Each is heavier than an elephant and as big as a school bus. These giant objects, he says, are more of a threat than the swelling fleets of relatively small internet communication satellites that have been launched by companies like SpaceX with deorbiting plans and capabilities. “Clusters of dead things are more dangerous than constellations of living things,” he says.

But, according to experts, although the technology is starting to develop, the political will is lacking. The policy of space agencies, says McKnight, is “to study, wait, and hope” while we want to “watch, characterize and act.” Almost all of the debris on McKnight’s Top 50 list was dumped there by government space agencies. “It’s a super villainous problem,” says Lewis. “The people who try to fix the problem are the ones causing it too.”