The European Space Agency (ESA) has just released a video announcing its award of a contract to Polish company SKA Polska for their design of a net deployment system for capturing derelict satellites from orbit.
As anyone who has seen the 2013 blockbuster movie “Gravity” can tell you, space debris is a problem. Space debris can range in size from small paint chips and explosive bolts from spacecraft, all the way up to discarded rocket upper stages and large satellites (in the region of 8 metric tons).
There are an estimated 500,000+ pieces of space debris measuring 1.27cm or more currently orbiting Earth. To give you an indication of the destructive nature of space debris, a small nut measuring 1cm in diameter (and travelling at 8 km/s) can impact a satellite with the kinetic energy equivalent to a hand grenade exploding.
If any of these larger pieces collide, they can fragment into thousands of smaller pieces which can veer off in all directions (making them much more difficult to track). These smaller pieces can then collide with other debris, causing more destruction and scattering even more debris.
This cascade of destruction is referred to as the Kessler Syndrome, and it has many people worried. The worst case scenario for such an event is an unpredictable cascade of exploding debris in low Earth orbit (LEO), which could potentially prevent space access for decades.
Every space agency takes this issue very seriously, and the European Space Agency has its eyes locked firmly onto one target in particular: Envisat.
There exists a list of top space debris targets, ranked according to their risk level, and at the top of that list sits Envisat. Envisat is a now-defunct Earth observation satellite launched by ESA in 2002. It ceased operations in 2012, due to a loss of contact with the satellite preventing any more control from the ground.
So Envisat is effectively tumbling uncontrollably in orbit. To make matters worse, due to a lack of control, the 8,211kg runaway satellite will remain in orbit for 150 years, with a 15-30 percent chance of collision within that timeframe.
So how exactly does one grab hold of an 8-ton uncooperative target as it tumbles blindly in orbit flailing a 20 square meter solar array?
Many options have been considered. Harpoons were an early possibility (although there is legislation preventing weapon systems in space), as were robotic tentacles. It seems according to the new video that they have settled on a satellite equipped with a deployable net. The net design offered the most flexibility with regards to uncooperative targets of a variety of sizes and attitudes.
ESA will launch the e.Deorbit mission, which will consist of a 1,300kg net-carrying satellite on top of a Vega launcher. Once in space it will enter a polar orbit (the same as Envisat). After intercepting Envisat, the satellite carrying the net will synch orbits with its target and fire the net at Envisat. Once captured, thee. Deorbit satellite will become a tug and engage its engines, hopefully pulling Envisat to a controlled but fiery demise, high in the atmosphere.
The net mechanism was designed by SKA Polska, which also designed specialist simulation software to simulate the net deployment in microgravity. SKA Polska plans to conduct parabolic flights with the net mechanism, to prove that the simulations measure up with the real world physics.
There is a final design review scheduled for the latter part of 2016 with the actual mission due to launch in 2021. eDeorbit will be the world’s first act of active space debris removal.
A video showing an animation of the e.Deorbit mission can be seen here.