Space, the final frontier. The one place humanity hasn’t defiled with litter.
Or so I thought. But if you’ve ever seen Wall-E, you’ll notice the striking image of the Earth – our home planet, big and blue and wonderful – surrounded by a dense cloud of grey space junk.
In reality, our satellite hoarding problem hasn’t gotten quite that bad; however, a man named Donald J. Kessler came up with an interesting theory about space debris during his time at the Johnson Space Center. While NASA was busy pumping out spacecraft after spacecraft (thank you, Cold War) Kessler was the only man to realize just how long these satellites would last. Long enough to, say, start smashing into each other as more and more of them clouded up low Earth orbit. As they collided, the satellites would fragment into smaller pieces of debris, which would then in turn increase the chances of even more collisions. This theory – or rather, this terrifying, looming problem – was aptly named Kessler Syndrome.
Houston, we have a problem. Don’t get me wrong – satellites are absolutely vital for communications, GPS systems, weather monitoring, and hosts of other faculties that we use in our everyday lives. They are also the reason we have incredible space telescopes (Hubble) and a floating research laboratory that is possibly the biggest show of international cooperation of the 21st century (the ISS). The problem arises with decommissioned satellites and their sheer number – their continued presence in orbit threaten all of the systems that share that space.
When initially postulating his theory about space debris, Kessler borrowed natural physicists’ kinetic energy equations and used thermodynamic models of molecules bouncing around inside a box in order to investigate his hunch. Obviously, satellites aren’t really atoms contained in a box, but these models did a good job backing up his theory, and were later validated by simulations of orbital dynamics.
And as much as it pains me to admit, the movie Gravity does a great illustration of this kind of collision:
So why is this a huge problem?
Keep in mind, these objects are traveling at a little over 17,000 miles per hour – the standard speed for maintaining low Earth orbit. (Speed = altitude in orbital dynamics speak) And when we have people living in a little metal tube the size of a few school buses floating around up there, collisions are something we want to avoid. The International Space Station already has to change course about once a month, forcing the crew to shelter in the Soyuz re-entry capsule until the threat has passed. The debris is already destroying one satellite a year; this threatens not only our astronauts, but our GPS, weather monitoring, TV, and military satellites. That smartphone you have? Surprise, now it’s just a phone. Or maybe just a $600 paper weight.
So what can we do about it?
Despite popular belief, the vacuum of space isn’t really a vacuum – or at least not in the few hundred miles above Earth. See, our atmosphere is a bit leaky – and there’s still a bit of air all the way up in low Earth orbit. Satellites will eventually succumb to the air drag and tumble down into the atmosphere, but this often takes years, or even decades.
While there’s not much to be done about the current decommissioned spacecraft in LEO (low Earth orbit), the Russians have developed a potential solution for future satellites. Their Mayak spacecraft was designed to be a low-cost technology demonstration of something called aerobraking. Aerobraking has a long history of being a cool idea that no one at NASA has really wanted to get behind, because it sounds ridiculous and risky.
When you want to use an aerobrake to slow down and re-enter Earth’s atmosphere, you just deploy a giant balloon from your spacecraft and let your drag increase by orders of magnitude. It’s low-weight method to slow your craft down that would be used early in re-entry before parachute deployment or retro-rocket engagement.
Essentially, Mayak deploys a giant parachute-like balloon and waits for the craft to drag itself down to Earth, where it will burn up in the atmosphere. This new feature could be installed on all future satellites in order to deorbit them after their functional lifespan.
So while we may not be able to declutter the space we already occupy, the Ruskies have found a pretty good solution in self-disposing space junk. Other ideas have been thrown around by Americans and Russians alike in order to address the current multitude of unused satellites; some involve lasers, others involve giant fishing nets. In the meantime, when you look up at the sky, just wonder if that star you see is really just a floating piece of space trash.