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Why It's So Hard (and So Important) to Track the Trash We Leave in Space

The space junk challenge.

Just take a moment to consider: we could be trapped on Earth by our trash in space.

In 1978, NASA scientist Donald Kessler wrote a paper on how the problem of space junk is prone to a domino effect. The quantity of space trash is continually growing as missiles destroy satellites, dead satellites crash into live ones, and rockets jettison engines. These and other activities leave behind observable hunks, along with tiny bits of paint, rock and metal that regularly collide with operational space gear at speeds of up to 17,500 mph (ten times faster than a bullet).

There are 500,000 pieces of space debris the size of a marble or larger, according to NASA. Kessler wrote that the more bits there are in space, the more likely those bits are to crash into each other. Crashes create more bits, which creates more crashes, in what's called an ablation cascade. At a certain point, there will be so many bits hurtling around the Earth that it will become effectively impossible to put anything else in space.

However, by modeling that trash, engineers can find the most efficient plan to clean it up.

One team of young programmers participating in the Space Apps Challenge, a hackathon where people respond to challenges posed by NASA, built a real time visualization of some of the larger pieces of space junk. They called themselves Team Kessler.

Team Kessler's simulation shows a 3D image of the Earth rotating, with 150 pieces of known space junk represented as white, orbital lines. As you watch, red blobs appear on the model. These represent areas of possible collision. Predicting collisions is still tricky, which is why it's useful for more people to simulate it in different ways.

A rocket fragment that crashlanded in Saudi Arabia. The rocket broke up after eight years in orbit. Image: NASA

Everything from ground-based lasers, to fishing nets, to robot cleanup patrols have been proposed to clear the skies, but executing a cleanup plan is years off (the European Space Agency is looking at a first cleanup mission starting in 2021). There is still lots of time to catalogue and analyze what's up there. The Joint Space Operations Center within the US Strategic Command tracks objects in space as does the European Space Agency. Simulations like Team Kessler's and SatView's are private complements to their work.

Every little bit helps, because predicting collisions is still hard. That's why the International Space Station takes evasive maneuvers when the odds are only 1:10,000 of a strike by a 4-inch or larger object. When the first two manmade satellites collided in 2009, models had predicted they would miss each other by 584 meters.

NASA holds hackathons because it needs help on problems like these. The more models get made of these objects in space, the more likely someone will innovate in the accuracy of predicting these collisions—and then maybe we can do something about them.

Perfect Worlds is a series on Motherboard about simulations, imitations, and models. Follow along here.