Do we need a recycling truck to take a run to Earth’s orbit?.
It’s with a degree of difficulty that we, as humans, imagine the vastness of space. This is perhaps because we move in ways more akin to 2D space on Earth. Sure, we can move back and forth, side to side, up and down, but our feet are generally firmly planted on the ground.
We can see this change in perception when someone goes from driving a car to driving a boat. In a car, for most of us, we have to follow the roads. Once you’re on the water, however, there are some basic rules to follow but on the open ocean, you can go wherever you please. The likelihood of collision between vessels on the open water is extremely low given this vast expanse of water (and, of course, the number of vessels on the water, compared to the number of vehicles on the roads).
This expansion of available space increases once again when we think about moving in a true 3D space. That is, taking to the air, or similarly underwater. Pilots and underwater divers tend to have a better grasp of this 3D space due to training because they’re navigating true 3D space.
It is perhaps for this reason, that our method of space exploration and consideration for impact has been somewhat careless (even if for reasons of efficiency). But it’s really only now becoming a problem.
THE MIRROR ON EARTH
This is no different to pristine beaches which become “insta-famous” and rapidly become covered in rubbish. If one or two visitors left a piece or two of rubbish behind, nobody was likely to notice. However, if thousands of visitors do the same, it ends up covered in junk, and a crowded place to visit. Earths orbit is no different.
Earth’s orbit is littered with debris from disused satellites, rocket boosters, and other hardware that have been discarded over decades of space exploration. There are now approximately 130,000,000 pieces of small debris in orbit.
THE PHYSICS CHALLENGE
In electronics, we know the impact power can have is a correlation between voltage and current. High current with very little voltage isn’t really an issue under most circumstances, nor is high voltage with very little current under most circumstances. But when you have high voltage and high current together, it has potentially lethal implications.
This is where we can draw a comparison to our space junk problem. These particles aren’t standing still. They’re moving at thousands of kilometres an hour. If they’re all moving in the same direction, such as geostationary satellites, then this overall speed doesn’t matter much. Just like when you’re driving on a multi-lane highway, the speed between vehicles is not much, however you woosh past someone in the breakdown lane.
The trouble is, all this space debris is moving in different directions at those exceptionally high speeds. This has the potential for high impact collisions.
To illustrate, in 2009, two satellites collided. On 10th February 2009, the 950kg Kosmos-2251, a deactivated Russian Military communications satellite collided with the privately owned Iridium 33, a 560kg communications satellite. They collided at an estimated differential speed of 11.7 metres per second. That’s 42,000km/h - nothing to be ignored! They were 789km above Earth at the time, and the Iridium satellite was still active.
The collision created thousands of pieces of debris. While some of this debris ultimately decays and burns up in the atmosphere, it continues to leave its mark.
As (bad) luck would have it, a small piece of debris from this collision raced past the International Space Station at barely 120m distance several months later. While it was predicted to pass-by safely, the six crew members aboard the ISS took safety precautions anyway. However, it demonstrates the compounding and knock-on effects of these events, creating potential challenges for many years after.
While the large impacts such as two large satellites colliding don’t happen very often, each piece of debris which finds its way into orbit, as well as further debris caused by further collisions, can create a cascade of issues.
International efforts continue to try and address this problem, but there’s no broad agreement. Some countries have agreed to send satellites to a “Graveyard Orbit”, which is clear from regular operational orbits. However arguably, this just moves the problem elsewhere.
Just as recycling and waste management is a growing issue on Earth, our orbit is rapidly seeing a need for cleanup too.