Ever seen the movie Gravity? Did the image of Sandra Bullock tumbling aimlessly through outer space, dodging white-hot spaceship debris give you anxiety on par with realizing you left the oven on in the house, halfway through your work day? Me too. If it were up to me (and it’s not), I wouldn’t want to put any more astronauts through that, even the fake ones. But space debris is a real problem, and situations like those in that spin cycle of a movie could happen if we’re not careful.
Space is not a trash can. But we’re treating it like one.
We have been polluting our Low Earth Orbit (or LEO) with stuff since about 1957, when the Russians launched Sputnik – humanity’s first satellite – into space. Space is now full of this junk: spent rockets, old and retired satellites, lost astronaut tools, a kitchen appliance here and there, and lots and lots of shrapnel. Space may be big, but the occasional collisions between these junked objects results in even more stuff (just smaller), and this cascade effect has led to millions of pieces of orbital debris.
Unfortunately, this debris isn’t just peacefully floating there, either: little pieces of old satellites fly at speeds of up to 6 miles per second, so when they hit the important stuff in space, it has really disastrous results. An object the size of a penny moving at 6 miles per second through space has the same impact energy as a small bus traveling at 60 miles per hour on the ground… if it came into contact with the international space station, both the penny and the wall of the station would be liquefied, depressurizing the module. This has actually happened in the past, and is a real threat astronauts face today; and that’s just from an object the size of a penny. Orbital debris constantly risks the lives of all astronauts on board, and billions of dollars of technological investment by world governments.
On average, humans send a rocket into space about every 4 days, usually carrying satellites. These operational satellites that give us Google Maps and Westworld are now becoming increasingly under threat by the millions of projectiles whizzing around our orbit (can you imagine a world without Google Maps? How would we get anywhere?). The more objects we put into space, the higher the probability that everything is going to eventually explode and we’ll end up with a larger-than-earth cloud of debris ringing our little blue world. We have done a fantastic job so far of polluting our own planet with trash; before we reach a critical threshold, we should be careful to start cleaning up our act.
Thankfully, NASA tracks objects in orbit larger than 10 cm in diameter: about the size of a softball. It is estimated that about 20,000 pieces of space junk larger than this currently orbit our planet, and keeping track of the positions of these objects has allowed us to take precautionary measures when a collision with something important is imminent. These large pieces of debris are therefore pretty easy for us to deal with.
Objects smaller than this, however, cannot be easily tracked, and are considered by NASA to be the “lethal population,” as they often do not provide any warning before causing damage to satellites or the ISS. It is estimated that about 500,000 pieces of this type of debris orbit the earth, which is the largest danger to our space presence. Objects smaller than 1 cm are considered to be the “risk population;” even paint flecks moving at these speeds can cause damage to spacecraft, but can usually be defeated by physical shielding.
Despite the danger that space junk poses to our infrastructure in orbit, there has been no international agreement for regulating space debris yet (bureaucracy wins again – shocker). However, space-faring nations are in the process of passing laws to make sure in the future, large satellites reserve enough fuel to push themselves back into the atmosphere after a certain operational period (for example, 25 years), where the retired debris will burn up upon reentry. It is more difficult for smaller satellites, which don’t use fuel or propulsion, but by placing the satellite carefully in a “decaying” orbit, they can ensure that over time, the earth’s gravity will pull the satellite back into the atmosphere, where it will meet its fiery death.
SpaceX has made clear that their future satellites will have the means to lower their orbits after use, either through orbital decay or propulsion systems, which is a big step forward: especially considering Elon Musk and SpaceX have plans to launch 12,000 satellites in the coming years. Considering the private sector now puts more stuff into orbit than NASA and US and Russian militaries combined, it is comforting to know some private companies are using foresight while continuing their space conquests.
It is pretty established that the only way to combat this problem is to limit the number of inactive objects in orbit, and therefore the chances of a collision. Ideas have been tossed around about dealing with the current junk, ranging from the use of a space harpoon to sweep up the larger nuisance junk to a robotic arm attached to a spaceship to grab the larger pieces and dispose of them. One group even suggested focusing the sun’s radiation onto small junk to burn it up, as one might with ants on a blade of grass. Ultimately, all of these ideas would be massive in scale, difficult to implement, and wildly expensive; what’s easier is making sure what we do put up there has an expiration date.
We are polluting an incredibly important resource, one which will become even more so in the coming years as we develop a stronger space presence. Satellites can and have improved livelihoods, communication and the flow of information across the planet, allowing for a massive technological expansion. But if we expect to continue to benefit from their luxury in the future, we must take into account a new form of environmentalism: that of outer space. Not unlike water, space should continue to be a resource that is free and safe. And that means keeping it clean.