The film Gravity starts with a bang: A satellite explodes, sending a deadly wave of debris hurtling toward two astronauts repairing the Hubble Space Telescope.
Art, in this case, imitates life. On Jan. 11, 2007, the Chinese government fired a missile into one of its aging weather satellites, smashing it into smithereens. Viewed as a provocative step toward the militarization of space, the strike drew sharp condemnation from the international community. Less discussed, though, was a different danger: those innumerable pieces of broken metal now orbiting the Earth.
Each piece, traveling up to 17,500 miles per hour, can seriously damage anything it hits. NASA estimates the total number of pieces of orbital debris larger than a grapefruit at over 500,000. Smaller debris could number in the millions. And when they collide, they break, creating more bits of potentially deadly space junk. A BB-sized piece can strike with the force of a Jeep speeding down a highway at 60 miles per hour. A single fleck of paint cracked the windshield of the Space Shuttle Challenger.
In the half-century after Sputnik kicked off the space race, orbital debris increased at a gradual, linear rate. The exploding Chinese satellite, however, created a huge spike in that rate; so did a 2009 collision between the Iridium 33 communications satellite and a long out-of-use Russian satellite. Previously, “space junk” mostly meant the cast-offs from launch vehicles—engines and other equipment used to get satellites into orbit, then discarded. But the two satellite incidents changed the game: Orbital space debris has reached a “tipping point,” according to a 2011 report by the National Research Council, potentially threatening our modern, satellite-based communications systems.
Luckily, while the destruction in Gravity happened in minutes, the real-life problem has been building for decades, and there’s time to do something about space junk. A growing international community works tirelessly to keep the world’s spacecraft safe. From a military agency tracking nearly everything in the sky to a sprawling network of researchers developing sci-fi technologies to vaporize orbital garbage, humanity is finally starting to solve the problem.
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In March 2012, the six astronauts aboard the International Space Station awoke to a potentially dire alert. A piece of debris from the Iridium satellite crash three years prior was careening perilously close to the station.
They quickly began evacuation procedures, getting as far as loading into the Russian Soyuz spacecraft docked at the facility before receiving the all clear. In orbital terms, the nine-mile gap between the station’s position and the space junk whizzing by was barely a hair’s breadth. In a dozen years, it was the third time the station’s occupants had loaded into the escape pods. A year before, the gap between the station and a piece of debris was a breathtakingly close 1,100 feet.
Orbital space debris has reached a “tipping point.”
It might seem obvious: If space debris is such a problem, why not armor the satellites and space stations? But the six inches of sheet lead that could protect against collisions would be prohibitively heavy; it’d be impractical to even get off the ground.
The current system involves literally avoiding the problem. Spacecraft operators need advance warning of possible collisions, and then they need to play dodge-the-debris. They need the Space Surveillance Network.
During the Cold War, the United States created a radar network to warn of incoming Soviet missile attacks. Thankfully, a Soviet first strike never happened, but the system remains useful: It can track anything in the sky, including satellites and space debris. Based at Vandenberg Air Force Base on the central California coast, it’s grown to include 20 telescope and radar sites across the globe—from Alaska to Cape Cod to the Indian Ocean’s remote Diego Garcia atoll.
Map of Space Surveillance Network sites, U.S. Space Surveillance Network/Wikimedia Commons (PD)
The Space Surveillance Network—which in 2006 was incorporated into the Joint Space Operations Center (JSpOC), an international effort that also includes the United Kingdom, Australia, and Canada—tracks some 23,000 man-made objects in orbit and publishes daily updates on Space-Track.org.
Anyone can use the data, from researchers and governmental space agencies to private satellite operators and space flight companies like SpaceX. However, aided by the Space Surveillance Network, JSpOC goes one step further.
“Every day we do what we call ‘conjunction assessment,’ which is an analysis to determine if two objects in orbit are going come within a certain distance of each other and potentially cause a collision,” says Lt. Col. Scott Putnam, who runs the Space Surveillance Division at JSpOC. It then warns satellite owners of a possible crash.
The network averages 23 warnings a day. In 2014, warnings led to a satellite moving once every three days; the International Space Station had to move three times that year. But the JSpOC doesn’t demand any moves. It only makes recommendations, even to NASA, and advises how to proceed.
We need to clear out the clutter.
Prior to Iridium, JSpOC had been screening about 140 satellites for collisions; after the crash, it also started including the 60 satellites in Iridium’s satellite fleet. Within a year, that number increased to more than 1,000.
Nevertheless, more collisions are inevitable, because there’s so much debris to dodge. The strategy, a JSpOC spokesperson admitted, doesn’t address the fundamental problem. We need to clear out the clutter.
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“If you increase the number of objects that you cannot control, it becomes more and more difficult for the ones you do control,” says Massimiliano Vasile. “It’s like dodging traffic on a highway against the flow of cars and hoping you don’t crash.”
Vasile, an aerospace engineering professor at Scotland’s University of Strathclyde, has spent the past four years thinking deeply about the dangers of space junk. Most of Vasile’s career was devoted to studying asteroids, until he realized his work was equally applicable to orbital debris.
“I started looking at them as the same problem at different scales,” he says. “From the scale of the Earth to the scale of the solar system. From the scale of tiny particles flying around the Earth, to the scale of asteroids that can reach the size of a moon.”
Vasile’s vision, made possible by a €4 million European Commission grant, begat Stardust, an ambitious research network comprising universities from Rome to Madrid, the European Space Agency, and private nonprofits like Germany’s DFKI.
Each partner has different specialties. Some focus on robotics, some on applied mathematics, others on astrodynamics. The goal is to encourage collaborations otherwise impossible in the often cloistered world of academia.
“It’s like dodging traffic on a highway against the flow of cars and hoping you don’t crash.”
Stardust Network Manager Peter McGinty explains that looking at space debris and asteroids simultaneously allows researchers to understand the similarities. In both cases, researchers need to be able to spot the debris, calculate its future trajectory, and then either destroy or deflect it somewhere harmless.
“We’re taking what we can learn from one issue—asteroids or space debris—and applying it across to the other,” McGinty says.
In 1978, NASA scientist Donald Kessler argued that every piece of orbital debris could crash into another, creating more debris and more collisions. Eventually, a belt of debris would ring the Earth, damaging everything it collided with. Fellow scientists dub this Kessler Syndrome; you see a version of it in Gravity, as the debris storm races around the planet. Vasile argues that simply removing five to 10 large objects from orbit each year would go a long way toward avoiding Kessler Syndrome.
To do so, Vasile and Stardust have pursued many different techniques. The most ambitious sounds like science fiction. Called Laser Bees, it involves creating a swarm of small spacecraft to blast debris with high-energy laser beams. As the lasers raise the temperature over a period of weeks, months, or even years, the material starts to vaporize, releasing gas, which acts like a thruster. The debris can then be directed either out into space or into Earth’s atmosphere, where it burns up upon reentry.
Vaporizing debris creates a whole host of questions. How does the debris move? Does it lose mass? Does it change shape? Does it start to spin? Does it stop spinning?
The answers can feed Stardust’s other work. For example, a project at the University of Southampton is investigating using robotic arms to move debris. Catching tumbling space junk is difficult; if the Space Bees lasers can slow the objects’ spin, the robot arms will have an easier job.
“We’re taking what we can learn from one issue—asteroids or space debris—and applying it across to the other.”
The lasers could also play a role in guiding debris back to Earth. Dr. Piyush Mehta models what happens to an object re-entering the atmosphere—how it burns up, or where surviving parts might land. It’s the difference between dropping an obsolete satellite harmlessly into an ocean or having it fall into a populated area.
Mehta argues it’s impossible to know exactly where an object will enter the atmosphere, but it is possible to predict probabilities of where it might land. His analysis, he adds, would be equally useful in case of an asteroid that could send humanity the way of the dinosaurs.
“If tomorrow we learned that an asteroid was headed to Earth, we could use the laser ablation technology developed in Stardust,” he says. “If that doesn’t work and the asteroid was still going to hit Earth, we could use this research as a way to inform policy makers about where the asteroid will hit, so they’d know where to evacuate and what the casualty rates might be.”
As with all ongoing scientific inquiry, there’s no guarantee any of Stardust’s plans will be implemented. And it’s not the only group tackling the problem. Scientists in Japan, for example, have tested a electrified, magnetic “space net” to catch debris, then destroy it on the return to Earth. A researcher in the United States even suggested blasting debris with air pulse cannons mounted on suborbital balloon platforms.
However outlandish or improbable the solutions, space junk remains a growing problem. The circling butt of shrapnel that threatened Sandra Bullock in Gravity is not far removed from the growing butt of rubbish threatening our satellites, the International Space Station—even the possibility of space exploration itself. Luckily there’s an unsung community of scientists and researchers working to make sure Kessler Syndrome doesn’t blanket the atmosphere, and that Gravity remains a work of science fiction.
Illustration by J. Longo