Orbital debris such as non-functional satellites, objects released during satellite deployment and fragments from the collision of space objects are now beginning to crowd space, posing a major risk to space missions. They have the potential to destroy or damage a spacecraft or a satellite, as well as endanger the life of astronauts and cause potential challenges for the International Space Station (ISS).
The figures are startling: according to statistics released by analysts, there are presently more than 29,000 useless objects that are greater than 10cm in volume, and 750,000 from 1cm to 10cm floating around in space. Furthermore, there are 166 million particles from 1mm to 1cm in size, all of which are space junk.
Many initiatives have been developed by universities to de-orbit space debris. The Space Engineering Centre at the Swiss Federal Institute of Technology Lausanne and Swiss Space Centre, in cooperation with the universities of Bern, NTB, and HES-SO in Switzerland have designed and developed CleanSpace One, a small debris recovery satellite that is designed to track an object the size of a milk brick flying at 7km/s at 720km above sea level. It will capture non-cooperative derelict satellites or debris, remove it and free its orbit for future space operations and reduce risks of collision, and open the path for recycling those satellites.
CleanSpace One will first be used to collect SwissCube satellites that have expended their useful lifespan. If they succeed, it will be used to de-orbit much larger debris of up to 300kg after the adjustment of the capture system. CleanSpace One is scheduled to be launched in 2021-2022.
Engineers at Stanford University along with the NASA Jet Propulsion Laboratory designed a ‘Robotic Gripper’, which uses gecko-inspired adhesives. The gripper is not as intricate as a gecko’s foot – the flaps of the adhesive are about 40 micrometers across while a gecko’s are about 200 nanometers – but the adhesive works in much the same way. Like a gecko’s foot, it is only sticky if the flaps are pushed in a specific direction but making it stick only requires a light push in the right direction.
This gripper comes with a grid of adhesive squares on the front and arms with thin adhesive strips that can fold out and move toward the middle of the robot from either side. The grid sticks to flat objects, like a solar panel, and the arms grab curved objects, like a rocket body.
A small gripper was sent up to the International Space Station (ISS), where they tested how well the grippers worked inside the station. Next steps for the gripper involve readying it for testing outside the space station, including creating a version made of longer lasting materials able to hold up to high levels of radiation and extreme temperatures.
The ‘MAYAK mission’ by Moscow State University is designed to de-orbit debris by using aerodynamic breaking systems and drag it to a lower orbit where it burns up on re-entry. Once in orbit, the satellite is designed to unfurl a giant pyramid-shaped solar reflector. The goal is for this satellite to shine brighter than any other star in the night sky. To do this, its reflector made of Mylar will span 16sqm and is apparently 20 times thinner than human hair. This mission, however, is said to have failed to deploy its reflective sail after launching.
European Space Agency (ESA) and Airbus Defence and Space are creating a solution and concept for debris removal called ‘e.Deorbit’ using net and robotic arm capture. Here again, they look at approaching the target, capturing it by firing the net or arm followed by removal. Once captured, deorbited satellite will be taken to a lower orbit, where it will burn upon atmospheric re-entry. This is scheduled to be launched in 2021.
What may seem individually small steps are nonetheless critical efforts in the right direction; the more initiatives we can make now, the better our chances of stopping space debris reaching a critical mass that may seriously impede exploration and our quest to reach further beyond our boundaries.