Contrary to many sci-fi depictions of crafts in orbit, which seem to simply float once they reach a certain altitude, objects like satellites must travel at speeds of up to 17,500 mph in order to stay aloft.
As a result, earth orbit is something of a racetrack. There are hundreds of satellites, 8,000 tons of junk and more than 500,000 pieces of debris that are tracked as they circle the planet. This orbital debris and the speeds at which it travels increases the potential danger to both manned and unmanned space vehicles due to the increased potential for collision-related damage.
What Constitutes This ‘Space Junk?’
According to NASA, orbital debris is any man-made object in orbit about the Earth which no longer serves a useful function. Such debris includes nonfunctional spacecraft, abandoned launch vehicle stages, mission-related debris and fragmentation debris.
In March, India shot down one of its own satellites in low-Earth orbit with a ground-to-space missile. This show of force led to an outcry among scientists who worry that there is already too much dangerous orbital debris. Similarly, the U.S. Space Command has identified 200 lingering pieces of India’s satellite, all hurtling around the earth at speeds that could severely damage space vehicles.
At a recent conference in Hawaii called the Advanced Maui Optical and Space Surveillance Technologies (AMOS), scientists are increasingly worried about clusters of objects in low-Earth orbit. Specifically, there are hundreds of rocket upper stages still orbiting Earth, primarily left by Russia between 1980 and 2000. These upper stages are massive and have no maneuverability.
What Can We Do about the Existing Orbital Debris?
In the 1970s, NASA scientist Donald Kessler pointed out the danger of orbital debris, noting that debris collisions generate even more debris in a cascading effect. The Kessler Syndrome is a catastrophic, runaway scenario that could conceivably occur within a few decades; debris fragments will start to dominate low-Earth orbit or at orbits around 800–1400 km in altitude.
In the most probable scenario, debris fragments will initially collide with large, intact objects. The resulting fragments from that initial collision will start to collide with such objects, and ultimately more and more collision fragments will collide with each other until all remaining orbiting objects are reduced to subcritical sizes; that is, sizes that won’t do any damage to space vehicles.
This self-sustained debris creation process poses huge risks to ongoing space operations unless something is done soon.
Various Solutions to the Problem of Orbital Debris Have Been Proposed
Both NASA and the European Space Agency (ESA) are alarmed enough by orbital debris that several unique concepts have been proposed.
The e.DeOrbit mission, a concept created by the ESA, proposes the use of a vehicle with several kinds of “capture mechanisms” to pick up orbital debris. These tools include nets, harpoons, robotic arms, and tentacles.
The Swiss have a potential solution as well. CleanSpace One is a 66-pound spacecraft designed to link up with out-of-commission satellites — and safely remove the target craft from orbit.
Perhaps most exciting, the Japanese Aerospace Exploration Agency proposes to use an electrodynamic tether whose current would slow down the speed of satellites or space debris. Slowing the speed of spacecraft or debris would cause it to gradually fall closer to Earth and burn up in the atmosphere.
With an increasing space operations tempo by both nations and private corporations, it’s time to look seriously at the increasing orbital debris problem.
Like ancient mariners navigating a perilous reef, humanity’s future in space may depend on our ability to successfully navigate the dangers standing between us and the universe. But unlike navigating a reef, this danger is one of our own making.