The ESA has been testing the possibility of using one of mankind's earliest inventions to cope with one of its newest challenges, by testing a concept that would allow satellites to net and de-orbit space debris in a safe and controlled manner. Space debris is an ever-increasing problem, and agencies around the world are starting to take steps to preserve the low-Earth orbit environment vital for a sustainable space industry.
Currently, there are around 12,000 objects exceeding 10 cm in size, and millions smaller orbiting Earth at speeds up to 15 km per second (9.32 miles p/s). If any such object impacted with an operational satellite, or possibly even the International Space Station, the results could be catastrophic. In order to prevent such an occurrence, any satellite due to be placed into an orbit of less than 2,000 km (1,243 miles) above the Earth are now required to incorporate technologies that would either de-orbit the satellite automatically, or push it in to a safe graveyard orbit upon reaching the end of its lifespan.
However the question remains, what can you do with the numerous defunct satellites that are already cluttering up low-Earth orbit? Such objects represent a significant long term hazard, as a collision between a satellite and another object could produce a cloud of smaller debris. To tackle the challenge, ESA has proposed placing satellites in orbit designed to capture large inert objects and manipulate them back into Earth's atmosphere.
However, there are inherent difficulties that make such an operation a daunting prospect. For example, one could not simply dock with the object as you would with another spacecraft, as the debris would most likely be tumbling in an unpredictable manner. Instead, ESA proposes to snag the harmful objects with a simple, low-tech net.
ESA recently tested the possibility by firing a series of 20 weighted nets at a mock satellite during a sequence of 21 parabolas in a Canadian Falcon 20 aircraft. Two types of net were shot from a compressed air ejector in order to determine which would be best suited to grappling objects in a low-Earth orbit environment.
It was discovered that thinner hewed versions of the nets were better suited to grappling and snagging the contours of the satellite, over the thicker variant. The success of the test means that the nets may be included in ESA's e.Deorbit mission, which, set to launch in 2021, will test the feasibility of removing large items of space junk from orbit.
Other potential technologies being considered for de-orbiting defunct satellites under ESA's Clean Space initiative include harpooning, utilizing a robotic arm to grapple debris, or even making use of a satellite-mounted ion beam. These concepts and numerous others are set to be discussed at a planned ESA workshop on reducing the impact of the space industry on low-Earth orbit, set to take place on March 17 and 18 this year.
The following video courtesy of ESA shows footage from one of the parabolic test flights.