For decades, the International Space Station has been hovering over Earth, in an orbit somewhere between two hundred and three hundred miles above sea level. Its massive rectilinear structure, resembling an Eisenhower-era TV antenna, contains hundreds of thousands of solar cells and a series of pressurized modules that can support life and equipment, all of it weighing close to a million pounds. Since 2000, people have been living on the station, in an area comparable to a six-bedroom house: humanity’s most expensive real estate. The station is also the fastest structure a person can live in. It orbits the planet at more than seventeen thousand miles an hour, many times faster than the Earth’s rotation. A day on the station, from sunrise to sunrise, lasts just ninety minutes.
In the early hours of July 16, 2015, members of the U.S. Air Force noticed an alarming development involving the I.S.S. Since the Cold War, the military has maintained an extensive space-surveillance network. Every minute, tracking stations across the globe relay a cascade of data to the Cheyenne Mountain Complex, in a bunker carved deep beneath two thousand feet of granite in Colorado. Some of the information is set aside for NORAD and other national-security organizations. Other portions are forwarded to the 18th Space Control Squadron, in California, which works to prevent collisions in the sky.
Sometime before three that morning, the surveillance network glimpsed a hunk of debris hurtling toward the I.S.S. A well-known piece of space trash, it had been labelled Object No. 36912 in an extensive inventory of orbital artifacts known as the NORAD catalogue. It had broken off of a Soviet military weather satellite, which was launched in 1979 from a Cold War facility near the Arctic Circle. The cylindrical satellite—resembling an old-fashioned boiler—was designed to work for less than two years. In the ensuing decades, it had been shedding fragments. That April, another piece of it had threatened the space station.
Object No. 36912 was likely a torn-off piece of thermal shielding; it appeared to be relatively light, and no bigger than a large dinner plate. For years, it had circled safely above the I.S.S. But its mass and shape made it highly sensitive to atmospheric drag—its orbit shifting dramatically as the atmosphere expanded and contracted in response to solar activity. Several weeks earlier, the atmosphere had ballooned, causing Object No. 36912’s orbit to suddenly decay.
As the debris spiralled downward, gathering speed, the Air Force was keeping a close watch, but small things in space can easily evade detection. The object was visible to just two radar stations, in Alaska and in Florida—and then it went entirely dark for more than a week. On July 16th, when it reappeared, Air Force analysts quickly updated their predictions: the object would make a close pass of the space station at 5:29 A.M. (Mission Control time, in Houston). It would clear the spacecraft by about fourteen miles, but penetrate a safety zone around the I.S.S. called “the box.” Then it would loop around the globe, falling farther, and come within striking distance—risking impact, or a “conjunction.” If the chance that something in the box will collide with the I.S.S. is greater than one in ten thousand, the condition is “red.” With Object No. 36912, the probability was more than one in a thousand.
At 2:44 A.M., the Space Control Squadron notified Jim Cooney, the I.S.S.’s trajectory-operations officer. Cooney, a NASA veteran, was asleep at home, but an app on his phone triggers a high-volume alarm for such alerts. “Your brain gets engaged really fast,” he told me. He had become accustomed to late-night calls. Only a month earlier, NASA had adjusted the spacecraft’s trajectory to dodge a fragment of a Minotaur rocket: a former intercontinental ballistic missile repurposed to ferry cargo into space.
These maneuvers have been performed more than two dozen times, and can be executed without much trouble if Houston has five and a half hours’ notice. But, when Cooney called the Air Force, he learned that Object No. 36912 would make its closest approach in about four hours. “I had them repeat the information to make sure I was doing the math right,” he recalled. Never before had the I.S.S. faced such a high probability of collision on such short notice. Moving the station was out of the question.
Instantly, he relayed the news to Houston’s flight director, Ed Van Cise, and then rushed to Mission Control, where he joined a tense meeting to discuss the options. There was only one: instruct the crew to lock down the station—closing hatches between modules—and then shelter in the Soyuz capsule, a Russian vessel that can serve as a lifeboat. There were three people aboard the I.S.S.: one American, Scott Kelly, and two Russians, Gennady Padalka and Mikhail Kornienko. In the Soyuz, they could detach from the failing structure and return to Earth. In the station’s history, its crew had sheltered in the Soyuz only three other times.
Van Cise reached out to Kelly, who was exercising on a treadmill mounted on one of the station’s walls. “Houston on Space to Ground Two,” a voice barked, announcing the call. “We are privatizing.” This meant that the feed from Mission Control, which usually could be accessed freely by the ground crew, would be nonpublic. Kelly later wrote in an expedition log that his first thought was, “Oh, fuck.” In space, unscheduled private conversations portend bad news: in 2011, on an earlier mission, Houston had privatized the channel to inform him that his sister-in-law, the Arizona congresswoman Gabby Giffords, had been shot.
Hearing that the call was for NASA business, he was at first relieved. Then the enormity of the situation sank in. Fuck, he thought again. The privatized call was a courtesy, so that Kelly would be prepared once the alert was relayed publicly. The space station operates on Greenwich Mean Time; for the crew, the moment that Object No. 36912 either slammed into the structure or zoomed past it would be 12:01. Mission Control instructed Kelly to start closing hatches at 10:30 A.M., then retreat with the Russians to the Soyuz at 11:51, and stay there until notified. Kelly cut short his workout.
At ten o’clock, Mission Control contacted Kelly again, to remind him that he and Kornienko had an interview scheduled with morning news programs in Florida and Kentucky. NASA reasoned that there was time to proceed: the interview would take less than twenty minutes, and lockdown was in half an hour. “Seriously?” Kelly wrote in his log. “We have a satellite coming at us.” But he and Kornienko got into their positions without protest. “We are ready for the event,” Kelly said, dryly, and glanced at his watch. Then he answered questions about the Kentucky Derby, performed zero-gravity stunts, and tried not to show that he was in a life-threatening situation.
As soon as the transmissions ended, Kelly began locking down hatches throughout the American modules. Calmly, he floated through the structure—the lab, the cupola, an air lock—with a flashlight in his mouth, to augment the station’s dim lighting. He had asked Houston if the debris hurtling toward the space station would be visible; as he closed the hatches, he got a response. “It will be in orbital night,” Houston told him. “So, no viewing opportunity.”
“How about relative velocity?” Kelly asked.
“Fourteen kilometres per second.”
“Copy,” Kelly said, plainly, but the number was terrifying: the debris and the station were closing in on each other at a combined speed of thirty-one thousand miles an hour. In orbit, a one-centimetre bolt can have the explosive force of a hand grenade upon impact. Object No. 36912 was at least ten times larger. When the space station’s shielding was being designed, a NASA astrophysicist named Donald Kessler had asked experts to shoot small objects at metal film cannisters at hypervelocities. The ballistics revealed that, even if debris penetrated the I.S.S. cleanly, it could leave a mangled hole upon exit. Object No. 36912 risked triggering a chain of failures that could destroy the entire structure.
Kelly focussed on procedure. Houston had told him to pick up a scientific instrument and a medical kit. He got those, and also some personal items, thinking of an American astronaut, Mike Foale, who had served on the Mir space station, in 1997. Foale had been living in a module called Spektr when a supply ship came in too quickly—like a shark, a cosmonaut onboard recalled, “this black body covered in spots sliding past”—and then smashed into it. To contain the breach, Spektr was sealed, forever separating Foale from his things, including gold pendants he intended to give his wife and children. “You always think about what happened to him when you’re closing a hatch with important stuff on the other side,” Kelly told me.
After locking down the American modules, Kelly caught up with Kornienko and Padalka in the Russian section. Padalka, the commander of the I.S.S., strove to project confidence; when Moscow Mission Control had asked him about the mood onboard, he responded, “Fighting spirit!” Kelly noticed that none of the hatches on the five Russian modules were shut. (Padalka and Kornienko say that they remember this differently.) “The Russians don’t close their hatches like we do,” Kelly wrote in his log. “They think it’s a waste of time—basically thinking the two most likely scenarios are the thing misses, or catastrophic destruction. The stuff in-between is way too unlikely to care about.”
Kelly was amazed to find the cosmonauts having lunch. “We wanted to eat!” Kornienko told me. “Russians have a proverb, ‘War is war, but lunch runs on time.’ ” The Soyuz’s food supply was limited to three days, and who knew how long they might be stranded there? There were fourteen minutes to spare, so Kelly joined them for a can of Appetizing Appetizer—a dish that, he later recalled, resembled cat food, “in appearance, consistency, and probably a little bit in taste.”
In Houston, the crew at Mission Control waited tensely. A wall-size screen contained a depiction of the space station’s orbit and a live feed of its interior. Ed Van Cise fidgeted with a computer mouse. One NASA official stared at a monitor with a hand over his mouth. Another sat with an emergency manual open; he told me, “We know what to do, but we don’t know what the outcome is going to be. This could be terrible, this could be a loss of life.”
At 11:51, the three men in the space station climbed into the Soyuz capsule, a cramped vessel that looked like a pinched cylinder atop the station. It was packed with switches and knobs. “It’s dark outside, so it’s darker than normal inside,” Kelly wrote in his log. “It’s cold.” He was wearing a black NASA sweatshirt, and he had pulled the hood down nearly over his eyes.
The men were instructed to leave the Soyuz hatch sealed, but unlatched—in case the debris hit the capsule rather than the I.S.S. and they needed to rush back in. Kornienko focussed on the latch, imagining the steps he would take in a crisis. “There were no words—silence,” he told me. Kelly, too, was struck by the sudden quiet, as each man retreated into his thoughts. He wrote in his log, “I can only hear the sounds of the fans inside the Soyuz, my breathing.”
With the tension growing, Padalka said, “You know, it will really suck if we get hit.”
“Da,” Kornienko said. “Will suck.”
A monitor indicated the time, and the men watched the minutes elapse, bracing for 12:01. Kelly noticed Kornienko gazing out a porthole. “Finally, I said, ‘Misha, you’re not going to see anything,’ ” he recalled. “ ‘That thing is going thirty thousand miles an hour, and it’s dark outside!’ Then I noticed that I was looking out the window, and listening, and tensing out, and then at some point you realize, We wouldn’t even fucking know if we got hit. We just would’ve been vaporized! ”
The three men fell into silence again. For a while, Kelly listened to his iPod. “As the time approached twelve noon and some odd number of seconds I started to grimace,” Kelly wrote. “Thirty seconds go by. A minute.” At 12:01, nothing happened. Padalka got on the radio. “Moscow,” he said. “Do you read?”
“Loud and clear. How are things?”
“We’re getting into 12:02,” Padalka said. “Everything is very quiet up here.” After nearly three tense minutes of radio silence, Padalka called in again: “Moscow, do we keep waiting?”
The radio crackled. “That’s all,” it finally said. Object No. 36912 had blown past the station. Later, the Air Force put its distance at less than a mile and a half—a gap it could have closed faster than the blink of an eye. Three weeks later, it incinerated in the atmosphere.
In the fourteen billion years between the big bang and the autumn of 1957, space was pristine. Then came Objects No. 1 and 2 in the NORAD catalogue: Sputnik 1—a polished orb of aluminum alloy with four long prongs—and the rocket that the Soviet Union had used to launch it, ushering in the space age. Sputnik circled the planet in an elliptical orbit, but at an altitude so low that atmospheric drag brought it down within three months. The following year, NASA launched Object No. 4, Vanguard 1, farther out into space, but then lost contact with it. Adrift since 1964, it still circles the planet. At the apex of the Cold War, Sputnik and Vanguard were triumphant emblems of a bold future. Today, they are emblems of junk.
Since 1957, humanity has placed nearly ten thousand satellites into the sky. All but twenty-seven hundred are now defunct or destroyed. Collectively, they cost billions of dollars, but they were launched with the understanding that they were cheaper to abandon than to sustain. Some, like Sputnik, have burned up. Thousands, like Vanguard, will stay in orbit for decades or centuries, careering around the planet as ballistic garbage: a hazard to astronauts and unmanned spacecraft alike.
These satellites are joined by thousands of spent rocket bodies and countless smaller items—space flotsam created by wear or collision or explosions: things like bolts and other bits of metal. There are odder specimens, too. Object No. 43205 is a functional Tesla Roadster (with a mannequin driver) that Elon Musk launched in 2018. A company called Celestis fires capsules loaded with human remains into orbit, where they will stay for nearly two and a half centuries. (The ashes of Gene Roddenberry, the creator of “Star Trek,” were sent aloft in Object No. 24779.) For years, Space Shuttles emptied their septic systems during missions: astronaut urine, instantly transformed into glimmering snowflake clouds, is reputed to be among the more beautiful visions in space. In 2007, a shuttle jettisoned a fourteen-thousand-pound tank of ammonia. (It later burned up over the South Pacific.) Astronauts, too, have accidentally let objects fall into orbit during space walks: a camera, a spatula, a glove, a mirror, a bag filled with a hundred thousand dollars’ worth of tools.
Small or large, personal or industrial—retrieving anything from space is immensely difficult, and has been done on just a handful of occasions. The military tracks about twenty-six thousand artifacts orbiting Earth, but its catalogue recognizes only objects larger than ten centimetres; the total number is much greater. By one estimate, there are a hundred million bits of debris that are a millimetre in size, a hundred trillion as small as a micron. We live in a corona of trash.
The first person to apprehend that space pollution posed a strange form of high-speed environmental damage was Don Kessler, the NASA astrophysicist who had helped assess the International Space Station’s vulnerability to debris. From his earliest calculations, the stakes were clear: the problem, if ignored, could destroy all the satellites that orbit near the Earth—a loss that would be more acutely felt as humanity increasingly relied on space. Communication systems would fail; scientific instruments—to study climate, or pandemics, say—would become inoperable. The losses could be measured in billions of dollars, and perhaps in lives, too.
For Kessler, space was a childhood passion. When he was growing up, in Texas, his father bought him a telescope to gaze at the stars, and he never lost interest. After high school, Kessler enlisted in the Army, and served in the Air Defense Command. In 1962, he enrolled at the University of Houston to study physics. Genial, confident, and mathematically adept, Kessler quickly found his way to the frontier of space research. Before graduating from college, he began working at NASA, through a program that allowed students to split their time between classes and the agency. “He was brilliant,” Darren McKnight, an aerospace engineer who has collaborated on research with Kessler, told me. “He could take a very complex problem and go, ‘Huh, it’s inversely proportional. It’s not that complicated.’ ”
In those years, the Apollo program had achieved a run of successful suborbital flights and was advancing toward a lunar mission. Kessler told me, “They said, ‘We’re going to Mars after this, and we’re going through a trajectory that’s going to take us into the asteroid belt.’ ” Although he was still a student, NASA asked him to research the environment between Earth and Mars, to understand how a spacecraft could journey through giant clusters of rocks that were continually smashing into one another.
Kessler spent five years thinking about asteroids, using statistics to represent the effects of their colliding and fragmenting; his work became NASA’s official meteoroid model for interplanetary space. But he wanted to go further. By the nineteen-seventies, humanity had launched more than three thousand satellites—which, like space rocks, could eventually collide and fragment. “It was just a matter of when,” he said. Kessler suspected that his models would illuminate these dangers, but he was unable to pursue the research. Amid agency-wide budget cuts, NASA dissolved his department, reasoning that its work was done.
Kessler became a flight controller for Skylab—an American space station that NASA had launched in 1973. Then he was assigned to the Johnson Space Center’s Environmental Effects Office, to study the impact of Space Shuttles on Earth’s atmosphere. He didn’t love the work. He was in his thirties, still trying to find his place.
At NASA, Donald Kessler was the first to grasp that space pollution posed a strange form of high-speed environmental damage. In the worst case, he warned, collisions of debris could trigger one another in an unstoppable cascade—a scenario that became known as the Kessler syndrome. Photograph by Anna Knott
In the mid-seventies, with the country racked by an energy crisis, the director of the Johnson Space Center, Christopher Columbus Kraft, decided that the agency should pursue an ambitious new mission: launch dozens of gigantic solar-power stations into orbit, where they would harvest the sun’s energy and then send it to Earth in microwave beams. Strong-willed and bold, Kraft was so integral to the creation of America’s space program that Neil Armstrong once called him the “control” in Mission Control. His new vision would require space engineering on an unprecedented scale: each of the orbiting power stations would have to be constructed from millions of tons of material. Even if they could be built, no one knew whether the high-energy microwaves were safe. Kessler told me, “They were concerned about what the beam would do to the ozone layer, to birds—or even to people who happened to be near it coming down.”
The head of the Environmental Effects Office asked Kessler to conduct an assessment of the space-based power stations. Kessler had no interest in the effects of beams zapping Earth—but he saw in the project a chance to return to his earlier research. He proposed modelling the effects of a power station breaking apart in orbit, arguing that it could threaten Space Shuttle missions. “That was my excuse,” he told me. “It really did get their attention.”
Throwing himself into the work, Kessler discovered that the prevailing attitude about orbital debris at NASA was based on a mistaken assumption—that the only artifacts worth worrying about were in the NORAD catalogue. Analysts preparing for the first Apollo mission had decided that smaller fragments were so trivial that they could be “neglected in the calculation of collision probability.” Debris was not an environmental problem. It was a traffic problem. You just needed to avoid what had been documented.
Having studied the way asteroids slammed into one another, Kessler knew that very small objects were far from negligible. Even a minuscule shard could smash a satellite to pieces, dispersing more high-velocity debris. If the population of objects became dense enough, collisions would trigger one another in an unstoppable cascade. The fragments would grow smaller, more numerous, more uniform in direction, resembling a maelstrom of sand—a nightmare scenario that became known as the Kessler syndrome. At some point, the process would render all of near-Earth space unusable. Theoretically, Kessler mused, our planet could acquire a ring akin to Saturn’s, but made of garbage.
In 1976, Kessler wrote up an “internal note” that explored three scenarios, based on various rates at which satellites were launched: conservative, realistic, and worst-case. In the realistic scenario, he speculated, the runaway collisions would begin in fifteen years, and by 2020 would cause certain altitudes to be so hazardous that a power station would not survive a decade. In the worst case, based on the assumption that the collisions were already cascading, the debris environment would be ten times that bad by 2020; within two centuries “all tracked objects would be completely destroyed and space would be filled with millions of fragments.”
Kraft dismissed the report as too theoretical; although Kessler’s predictions drew upon some old experimental data, they relied mostly on math. Undeterred, Kessler searched for more data. “All of my management said, ‘You’re supposed to be doing other things—what are you doing this for?’ ” he told me. When he learned that an Air Force radar station in North Dakota had briefly been recalibrated to take more sensitive readings, he reached out, and discovered a large uncatalogued population of debris. With a NASA colleague, Burt Cour-Palais, he sharpened his predictions—arguing that the flotsam could quickly pose a greater danger than meteoroids. Still, after another presentation to Kraft, he was instructed to spend no more than ten per cent of his workday on the research. The head of the Environmental Effects Office took to muttering, “Kessler and his damn debris!”
Then, in 1978, a Soviet intelligence satellite, called Kosmos 954, fell from the sky. It was nuclear-powered, with a reactor core containing more than sixty pounds of enriched uranium. Breaking up over remote northwestern Canada, Kosmos 954 scattered radioactive wreckage for hundreds of miles. Recovery crews dressed in hazmat suits, working in extreme conditions—in some places colder than forty degrees below zero—struggled to reclaim it.
Kosmos 954’s breakup became an international incident, prompting officials from around the world to scramble for information about derelict satellites. Suddenly, the Secretary of State was speaking about hazards in space. An expert on nuclear warfare, testifying before Congress, described Kessler’s predictions as “chilling.” United Nations officials, suspecting that Kosmos 954 had collided with something in orbit, sought Kessler out. Burt Cour-Palais reported that NASA had brought up their research at the SALT II negotiations with the Soviets. “Our work has hit pay dirt,” he said.
Kessler decided that he would have to work on the project either fully or not at all. He insisted on meeting with Kraft, who invited him to make another presentation. Looming over the meeting was the impending fate of Skylab—then the largest structure in space, and by that time derelict for years. “We had abandoned Skylab without a full appreciation of what that meant,” one of Kessler’s superiors later recalled. It was only a matter of time before Skylab, like Kosmos 954, came crashing back to Earth or was hit by something and splintered into pieces. Already, the rocket that launched it had smashed into the Atlantic.
When Kessler arrived at the meeting, he found it packed with NASA V.I.P.s, including officials who had objected to his research. He was convinced that his career was on the line, but, he told me, “I knew I had a story to tell.” Determined to offer pragmatic solutions, he explained that he had discovered that the largest source of debris at the time was spent Delta rockets, which were exploding in orbit, often long after they were “presumed dead.” A simple design change would prevent the explosions. “The solution was not to spend less time in space,” he recalled. “It was to do it more responsibly.”
Kraft became a convert. “We would be crazy not to continue!” he told Kessler, vowing to obtain funding for a full-time study of the problem. “Go do it,” he declared. “Forthwith!”
Three months later, Skylab was hurtling downward over the Indian Ocean—“a blue fireball in the starry predawn sky,” according to a NASA history. The fireball then turned red-orange and splintered into five pieces. Early risers in southwestern Australia saw the blazing fragments; in Perth, they rattled windows with a sonic boom. The disintegrating machine rained tons of debris across the outback. No one was hurt. But one town, the Shire of Esperance, later issued NASA a littering ticket with a four-hundred-dollar fine.
The universe may be infinite—a “big sky,” as some NASA officials have described it—but even an endless amount of space is too small if you can occupy only a tiny bit of it. Kessler knew that the most worrisome region was the closest one: low Earth orbit, or LEO, which extends to about twelve hundred miles above sea level. At the bottom of LEO, where gravity holds together a semblance of sky, the atmosphere is thick enough to cause circling objects to lose energy and return to Earth quickly, a self-cleaning process that keeps the density of debris low; the International Space Station is kept there, in part for safety. About four hundred miles above the Earth, the exosphere begins. The atmosphere there is so thin that molecules can circle the planet without colliding with one another. This part of LEO is an engineering sweet spot: far enough from Earth that keeping a satellite in orbit requires no energy, but close enough that the cost of shielding against solar radiation and powering communication systems is relatively low.
With a budget of just seventy thousand dollars, Kessler pulled together a scrappy team: five specialists who agreed to help him, part time, to study LEO’s growing congestion. They became space detectives, piecing together clues from the kinetic, chaotic world above. To measure the quantity of debris that had been left out of the NORAD catalogue, they got access to an M.I.T. telescope, at New Mexico’s White Sands Missile Range, which could glimpse fragments as small as a centimetre. When a Space Shuttle returned to Earth, the team treated it as a source of evidence. Shuttle windows were often marred by impacts, but typically could not be removed for analysis. During one flight, however, an oncoming object gashed a window so badly that it had to be scrapped. The team, seizing the discarded component, learned that the damage had been caused by a minute speck of paint that had flaked off another orbiting machine.
While Kessler strove to understand the environment, he also took on an activist role to protect it. Many people at NASA remained skeptical of his assignment; some scientists who had mapped debris for the Apollo program were even defensive. “I had the chance to ask them, ‘Why didn’t you consider this cascading phenomenon?’ ” Kessler recalled. “Their response was ‘We didn’t have the computer power.’ And I thought, My goodness, they had the computers that were used to go to the moon, and I did my calculations on a programmable calculator. But I didn’t try to embarrass them.”
Kessler was well suited to the task of convincing his peers; an easygoing Texan, he had a knack for elegant mathematical insights that could be sketched on an envelope, and a quiet flair for showmanship. After examining the damaged segment of Space Shuttle window, he kept it, and sometimes enlivened presentations by dramatically pulling it from his pocket. To address the issue outside the agency, he joined with allies at NASA to push the makers of the Delta rockets for a redesign; later, he helped form the first international organization for space-faring nations, whose work on orbital debris was absorbed into the United Nations.
But space diplomacy wasn’t always easy during the Cold War. In 1968, the Soviets had initiated a series of antisatellite, or ASAT, experiments, in which a spacecraft packed with explosives would approach a target satellite, then self-destruct, its own shrapnel serving as a weapon. Kessler spent months tracking a mysterious swarm of tiny, perfectly spherical objects, suspecting that they had come from a Soviet ASAT test intended to prepare for a nuclear war. The source turned out to be stranger: a Soviet naval satellite that had ejected its reactor core before it fell to Earth. The spherical objects were globs of liquid-metal coolant that had been jettisoned at the same time. “When we approached the Soviets, they said, ‘Yup, we did that,’ ” Kessler recalled. “Then they said, ‘Nope, nope, we didn’t.’ Then they said, ‘Oh, they’re going to evaporate! ’ ”
America had its secrets, too. In 1985, Kessler was drawn into Ronald Reagan’s Star Wars initiative when the Air Force decided to conduct its own ASAT: shooting down a satellite with a missile fired from an F-15. He begged the military to forgo the test. “We said, ‘It’s going to cause a lot of debris,’ ” he recalled. The Defense Department was unmoved. “They told us, ‘You don’t know what’s going to happen. It may just leave a clean hole.’ ” Making the best of the situation, Kessler flew to Alaska to observe the satellite blowing apart in the darkness of space. He tried watching from a ground telescope, but bad weather blocked his view. A NASA colleague used a high-altitude Air Force plane to observe the event from above the clouds—but, while military radar indicated hundreds of pieces, he could see only two. “Those fragments must be black,” he radioed. Kessler’s instinct was to disagree—the debris was mostly shiny aluminum—but he eventually concluded that electronics on the exploding spacecraft had been singed, coating the remnants in carbon. Further research indicated that most orbiting fragments were very dark—which meant that the telescope at White Sands had been underreporting the environmental damage. There were more objects in space—larger and more destructive ones—than even Kessler and his team had been able to see.
The more Kessler studied Earth’s near-space environment, the more worrying the trend lines looked. By the nineties, he had become convinced that collisions in the most populous orbits were cascading, spraying fragments across hundreds of miles. “These unstable regions will act as an increasing source of small debris in all of low Earth orbit for centuries,” he warned. In 1986, a European rocket body had broken apart, most likely because something collided with it; one of its fragments orbited for years before smashing into a stabilizing boom on a French reconnaissance satellite. In 1994, a Defense Department satellite, MSTI-2, went dark shortly after launch; NASA speculated that a shard had collided with a bundle of wires, causing a short. MSTI-2 then became debris itself, nearly colliding with the Space Shuttle Endeavour and then with Mir.
Kessler had retired from government by then, but he continued to work with NASA, first as a Lockheed employee and then, after 2005, as an independent consultant. At the time he left NASA, the number of man-made objects in space was declining. ASAT tests were less frequent, exploding rocket bodies were becoming less of an issue, and the collapse of the Soviet Union had put a temporary halt to Moscow’s space program; a surge in solar activity hastened the burn-up of many items in low orbit. But the momentum was difficult to sustain. Moscow’s space program eventually ramped up again, and new space-faring nations came to behave as heedlessly as the Cold War superpowers had. In 2007, the Chinese military conducted a surprise ASAT test, firing a missile at a weather satellite, scattering so much shrapnel that the I.S.S. is still maneuvering around the fragments. At the same time, satellites and rocket bodies were beginning to collide, as Kessler had predicted—a trend more worrying than deliberate explosions, because it indicated self-generating hazards.
In February, 2009, four hundred and ninety miles above Siberia’s Taymyr Peninsula, on Russia’s Arctic coast, two intact satellites rammed into each other for the first time. One was owned by Iridium, the American communications company, and the other was a derelict Soviet Kosmos satellite. They were travelling at tremendous speeds; upon impact, plumes of shrapnel spread outward like ribbons around the globe. The collision—combined with the debris caused by the Chinese ASAT test—added nearly six thousand objects to the NORAD catalogue.
The Iridium-Kosmos smashup marked a dramatic escalation. “We are entering a new era of debris control,” Kessler noted. “An era that will be dominated by a slowly increasing number of random catastrophic collisions.” He urged space programs to stop abandoning satellites and rocket bodies in orbit, and suggested that it might even be time to retrieve some derelict objects. “As is true for many environmental problems, the control of the orbital debris environment may initially be expensive, but failure to control leads to disaster in the long-term,” he argued. One NASA official went so far as to declare, “The Kessler syndrome is in effect.” And yet, space was becoming more crowded: more satellite launches, more debris. As of July, 2018, a NASA report states, more than half the items that the 18th Space Control Squadron tracks are fragments. Collisions are now their dominant source.
“People are not really worrying about this, because it is inconvenient to act responsibly,” Darren McKnight, who works as a technical director at the aerospace-services company Centauri, told me. Recently, he and some colleagues studied a debris cluster six hundred miles above sea level; there are now sixty close calls in it every day. A hundred miles beneath that cluster is an even more worrying one, where eighteen of the most massive derelict objects in space pass in close proximity on a daily basis. Last year, two of them—a three-ton Soviet intelligence satellite and an eight-ton Soviet rocket body—missed each other by just ninety-five yards. Had they smashed, the effect would have been disastrous. “It would have doubled the catalogued population,” McKnight told me. “Sixty years’ worth of space-debris growth would have been matched by that one event! ”
By his estimate, the collision would also have created two hundred thousand bits of “lethal” shrapnel, too small for the military to track but capable of damaging spacecraft. McKnight, like Kessler and others, has come to believe that clearing away artifacts from low Earth orbit is essential to keeping the environment stable enough to use. There is no pragmatic way to vacuum up swarms of microdebris. But removing the largest items can stop more from forming. In 2006, Kessler’s successor at NASA, Nicholas Johnson, and an analyst named J.-C. Liou wrote in Science that “only remediation of the near-Earth environment—the removal of existing large objects from orbit—can prevent future problems.” Developing Kessler’s models, they argued that, by 2020, at least five of those had to be removed every year to prevent the number of runaway collisions from spiking disastrously.
Currently, McKnight is working with researchers around the world on a list of the top fifty derelict objects to target for removal. “People think that Iridium-Kosmos was the worst breakup,” he told me. “No, it’s not! It was really pretty small. If you think that was bad, wait until you see the real thing.”
In April, 2018, a SpaceX Falcon 9 rocket took off from Cape Canaveral, achieved an altitude of about three hundred miles, and then released a large unmanned capsule, called Dragon, which propelled itself to the International Space Station. Dragon was ferrying tons of supplies—everything from an HP inkjet printer to space-walk equipment. The largest item in its hold was a foam box, weighing more than two hundred pounds. Aboard the station, the box was kept in storage for two months. It did not have the normal labelling that NASA requires for I.S.S. cargo. In Magic Marker, someone had written on the foam, “NanoRacks Remove Satt P/N: NR-MS-06.” For the astronauts on the I.S.S., the box was a mystery. Ricky Arnold, an American serving there at the time, asked Houston if he could use it as a makeshift worktable. The answer was quick and unambiguous: negative. “It was like the large present under a Christmas tree,” Arnold told me. “No one knew what it was.”
The first week of June, Houston told the I.S.S.’s crew that the box contained an unmanned spacecraft, scheduled to launch from the station later that month; once in orbit, it would test technology to remove debris. Although a number of methods had been proposed for extracting space junk—ranging from sticky foam to blasts of air—no technology had been tested successfully in space.
Drew Feustel, a NASA astronaut who was serving as the I.S.S.’s commander, had seen the hazards firsthand: divots in the station’s cupola windows and holes punched through solar panels. Here and there, shards had blasted through exterior handrails—a danger during space walks, because the resulting burrs could tear through spacesuits. As alarming as these were, Feustel knew that the I.S.S.’s low altitude meant that its encounters with flying junk were relatively minor. In 2009, he had been on a Space Shuttle mission to service the Hubble telescope, which orbits about a hundred miles above the I.S.S. As he floated from the shuttle to the telescope, Feustel noticed that Hubble’s exterior was so pitted that it resembled a moonscape. “In one instance, we found an impact that entirely penetrated the structure,” he told me. “No doubt, any particle that can put a hole in a spacecraft can put a hole in your body.” Arnold told me that the most worrying thing about debris was the randomness: a fleck could come from anywhere, at any time.
The foam box on the I.S.S. was stored in the station’s largest inhabitable room, the Japanese Experiment Module, a laboratory for tests conducted both inside and outside the space station. Near a cylindrical air lock in the JEM, the two astronauts unpacked the box, following instructions issued by Nanoracks, a kind of FedEx for space, which oversaw the parcel’s delivery and deployment. The men secured their feet to the floor to keep from floating away, and wore surgical gloves as they worked. Inside the box, they found a cube-shaped device sheathed in glossy solar panels, with semitranslucent gold-colored tape running along its edges. One side of the cube was open, revealing an interior filled with instrumentation. “It was just this magnificent piece of hardware,” Arnold told me.
The two astronauts mounted the satellite on a tray, called a slide table, which rolled on tracks through an air lock to the outside. No satellite so large had ever been deployed from the I.S.S.; this one had to be measured precisely to fit. Feustel initiated the slide table, and the cube entered the air lock. On June 20th, the crew released it into the coldness of space. A sixty-foot robotic arm mounted on the station grabbed it, held it a safe distance away, and then let it go.
Feustel asked Houston, “Are we expecting anything to deploy from the satellite?”
“No,” Houston said. “That’s all we’re expecting. It’s going to hang there for a while.”
Extremely slowly, the cube drifted from the robotic arm, tracing its own orbit over the Earth—a pearl of crystalline blue and snow white, below. Arnold had rushed to the cupola to shoot video of the machine drifting away; satellites are almost never photographed from space. This one reminded him of boxy spaceships from “Star Trek,” used by a collective of cyborgs called the Borg. He hoped to post a video of it on Instagram, with the tagline “Resistance is futile!” Houston told him that he could not. The cube was proprietary.
As the I.S.S. and its payload slowly spread apart above the planet, they passed over the University of Surrey, an hour outside London. On its sprawling campus, a group of engineers had gathered in a two-story brick building named for the science-fiction writer Arthur C. Clarke. The building is home to the Surrey Space Centre, which oversaw the creation of the boxy satellite—a machine called RemoveDebris. They had crowded into a control room with wall-mounted screens, one of which relayed a live feed from a camera on the I.S.S.’s exterior, showing RemoveDebris in orbit. They had spent six difficult years building the machine. Seeing it aloft, they were ecstatic.
When Feustel had asked Houston if anything was going to deploy from RemoveDebris, the engineers at the Surrey Space Centre, listening to the transmission, burst out laughing. The satellite was packed with ballistic instruments designed to shoot from multiple cavities—among them a titanium harpoon, strong enough to pierce a spacecraft wall, and a twenty-five-foot Kevlar net designed to grab an object in space and haul it down toward Earth.
The net was a particular source of anxiety. Officials at NASA were so concerned that it would deploy prematurely, entangling the multibillion-dollar space station, that they insisted RemoveDebris be allowed to drift away from the I.S.S. for a full month before the experiment began. Standing in the Surrey Space Centre’s control room earlier this year, Richard Duke, a project engineer on the RemoveDebris team, recalled, “Of course, we didn’t want anything to deploy.” He chuckled. “We were doing this for the first time, and there were so many things that could cause damage.” Simon Fellowes, RemoveDebris’s program manager, put it differently: “No one is going to forget it if you are the guy who took out the I.S.S. with a net!”
In a field that epitomizes Big Science, the Surrey Space Centre is an unusual player: a tiny, low-budget, academic-minded operation that has pioneered the development of tiny, low-budget satellites, called CubeSats, some of which are no bigger than shoeboxes. “We demonstrate new technologies cheaply,” Duke told me. “Nobody ever wants to fly anything new on the big spacecraft, because you don’t want to risk it. But if you can’t fly it, then how do you get experience?”
In the eighties, the university spun off a private company, Surrey Satellite Technology, which manufactures medium-sized spacecraft; that company was later acquired by Airbus. RemoveDebris emerged from a brainstorming session among all three parties, in 2013. By then, it was possible to imagine a market for technology that regained control of derelict objects in space. The United Nations had issued a guideline that satellite operators must remove their spacecraft from orbit after twenty-five years. There was also a suggestive test case: in 2012, the European Space Agency lost control of a satellite called Envisat in the most crowded region of space, and began to express an interest in funding the development of debris-removal technology. Envisat was an eight-ton machine, the size of a school bus, spinning uncontrollably—as a former ESA official said, “Quite a huge beast.”
Within Airbus, groups of engineers across Europe were already experimenting with tools that could bring down such a thing. A team in France was working on a laser-based imaging system, called LIDAR, that could allow a junk-collecting satellite to navigate around an abandoned object. A team in the United Kingdom was working on a harpoon gun, inspired in part by nineteenth-century whaling technology. A team in Germany was developing a net. In zero gravity, the net would have to open with perfect symmetry, then collapse around an object without pushing it away. Airbus had tested it in a vacuum, and in the “vomit comet”—an airplane that took a steep dive to simulate a gravity-free environment.
On Earth there is no way to test such a device both weightlessly and in a vacuum. But the Surrey Space Centre had experience designing low-cost orbital experiments; after the meeting, it applied for a fourteen-million-euro grant from the European Union to oversee a consortium that would test the Airbus technologies in space. Fellowes was brought in to lead it in 2015. “A harpoon and a net,” he told me. “Other than a stone, how much more basic can you get?” And yet nothing about the work was simple. Several years earlier, NASA’s J.-C. Liou had warned that, though debris removal was urgently needed, attempting it would involve “tremendous technical challenges and costs.” The Surrey Space Centre was effectively seeking to prove this assessment wrong. As Fellowes told me, “To be completely honest, it looked like an impossible project.”
The problems weren’t confined to the engineering. Legal complications prevented Fellowes’s team from grabbing actual debris during a test: even after a spacecraft is blasted to pieces, those pieces remain sovereign property. The experiment would have to deploy its own targets. Over time, the design began to resemble a Russian matryoshka doll: nested inside the satellite ferrying the Airbus technology were several smaller CubeSats that would fire out of it. In order for the spacecraft to relay data to one another, radio frequencies had to be secured around the world. “Not easy!” Duke said. “We were having to talk to Japan, saying, ‘Well, we know we are on the same frequency as your TV!’ ”
Even getting RemoveDebris onto the International Space Station posed complications. “We were in a safety briefing with NASA,” Duke recalled. “We were talking about this thing called the H.T.A., and eventually they ask, ‘Well, what’s the H.T.A.?’ We go, ‘The harpoon target assembly,’ and, instantly, they go, ‘Uh, what did you say?’ ” The Surrey team screened an animated film to demonstrate the device, but it only elevated the NASA officials’ concern. Fellowes told me, “They were stunned—just silence—until they were, like, ‘Let’s watch that again.’ Then it was, ‘You guys must be crazy!’ If you think about it, everything onboard RemoveDebris is specifically designed to bring a spacecraft down! The LIDAR—one guy at NASA was, like, ‘Let me get this right. You’ve got a laser, and, if you turn it on, it will blind you, but it is not visible to the human eye?’ We were, like, When you put it like that, it sounds really bad!”
Fellowes’s team worked for months to meet NASA’s safety requirements—going so far as to blow up batteries in a parking lot. When NASA was finally satisfied, in 2017, the team installed a metallic port on RemoveDebris, for the I.S.S.’s robotic arm to grab onto once it left the air lock.
Shortly after the engineering was finished, the team received disconcerting news: the Japanese Aerospace Exploration Agency had launched a similar device, a half-mile “electrodynamic tether” designed to grab junk in space. (The tether was made with the help of a Japanese company that has been weaving fishing nets for more than a century.) It had just failed—even though the project had the support of a national space agency. “It was upsetting and worrying,” Fellowes told me. “You think, Those guys know what they are doing as much as anyone. What did they miss?” By then, there was little that his team could do. RemoveDebris was packed in foam and delivered to Cape Canaveral, to wait for its own try in space.
Throughout the summer of 2018, RemoveDebris inertly orbited the planet, while the team in Surrey worked to insure that all systems were functional. Then, that September, the engineers instructed the satellite to launch the CubeSat and fire the net at it. The commands had to be given when the satellite was over England, but the experiment was scheduled to happen over Asia, where lighting would be good. Fellowes spent a restless night checking his phone. The 18th Space Control Squadron was keeping a close watch. At 2 A.M., it sent a note: something had accelerated from the satellite. Duke recalled, “They say, ‘We’ve got two objects.’ It could have been that the CubeSat came out, but the net hasn’t. It could have been that the net worked, but the CubeSat didn’t.”
At 6:30 A.M., Duke rushed to the office, where he found Fellowes going through data that the satellite had transmitted. RemoveDebris had recorded about a minute of video, but it was possible to download only a few frames each time the satellite passed overhead. In ghostly black-and-white, the footage depicted a silent, zero-gravity technological ballet. The target CubeSat shot itself out of RemoveDebris into the darkness of space. Its reflective exterior looked like a gleaming brick, until pressurized gas forced aluminum tubes to burst outward from each side, transforming the satellite into something resembling a jack, with sails between its spokes—a target with greater volume. But, because of a leak in one of the tubes, they had unfolded asymmetrically, causing the target to start spinning wildly. Duke and the others watched the footage, rapt. “As engineers, we had visualized this as charts, as graphs, as timetables,” he said. “I don’t think we thought about what it would look like.”
Moments later, the net deployed. Along its perimeter, Airbus had fixed a series of small motors, which acted as weights. They surged out in a starburst pattern, causing the net to resemble a silvery undersea creature preparing to consume its prey. To keep the experiment simple, the net was not tethered to the RemoveDebris satellite; it traversed space on its own. As it hit the target, the motors on the webbing activated, drawing in the strands around the CubeSat, the two entangling into a single spinning mass. The imagery was part technical study, part Man Ray. “I was in shock,” Fellowes told me. “I went for a walk and got a coffee, and then all I did for the next hour was watch it repeatedly.” The experiment was conducted at a very low altitude, to insure that the tangled net and CubeSat—Object No. 43621—would not remain in orbit. Within months, they plummeted, the years of research reduced to ash.
As RemoveDebris deployed its net, it recorded about a minute of video to transmit to the team on the ground—footage that is part technical study, part space ballet. “All I did for the next hour was watch it repeatedly,” one engineer said. University of Surrey, RemoveDebris project
Last year, the team instructed RemoveDebris to fire its harpoon at a panel mounted on an extendable boom. The force was so great that the panel snapped off. But the puncture was dead on, and the harpoon locked itself in, without throwing out shards that would become more space junk. Duke told me that the team originally thought the harpoon was better suited than the net to capturing large payloads like Envisat; it might risk destroying the target, but it was simpler. (At an Airbus facility, I saw a huge next-generation harpoon gun that looked as if it could take out a whale.) The net system was far more difficult to operate—but, in his view, the success of the experiment made it seem like the more appealing option. “That’s what this was about,” he told me. It was still far from clear that either tool could be deployed on a real mission, but that was for future trials to study, he said: “We wanted to demonstrate the technology, prove it fundamentally could work.”
In 1979, Arthur C. Clarke imagined a future in which giant lasers kept space clear of debris—an idea that NASA has considered but not pursued. There is no shortage of alternatives. Companies are competing to develop technology that can either dispose of derelict machines or repurpose or service them. Nanoracks is hoping to convert orbiting rocket bodies into habitable space stations, and is even preparing a space-based test of a tool that can slice metal without shedding debris. A Tokyo-based company, Astroscale, has raised a hundred and forty million dollars in venture capital, and this year plans to launch an experiment to grab and control an orbiting artifact; members of the RemoveDebris project are building it a test target.
Kessler, who is now eighty, told me that he sees no obvious technical solution. “It’s a very difficult problem,” he said. “I’m glad I don’t have to work on it. You have to start small.”
A few years ago, the European Space Agency decided that Envisat might be too challenging as a first goal, and so it drew up a list of other derelict objects and issued a tender to bring one down. Thirteen consortia applied, including groups led by Airbus and Astroscale. In December, 2019, ESA announced a surprise winner: a group led by a tiny Swiss startup, ClearSpace, which committed to retrieving a rocket body for more than a hundred million euros. It plans to use untested technology—robotic pincers—that theoretically could be reused. “Imagine how dangerous sailing the high seas would be if all the ships ever lost in history were still drifting on top of the water,” ESA’s director general said at the time. “That is the current situation in orbit, and it cannot be allowed to continue.”
Europe has become a leader in the effort to clean up space, while the program that Kessler created within NASA has come to look increasingly anemic. In 2018, just after RemoveDebris’s net experiment, I spoke with J.-C. Liou, who now runs the program. The Trump White House had recently issued NASA a new goal, to return people to the moon—a budget-dominating mission. Despite Liou’s earlier work illustrating the need for debris removal, he described it to me as an unrealistic priority, and instead emphasized prevention—better compliance with existing rules—and the importance of further study. He had been cleared to use a satellite to measure millimetre-size objects. This year, when I checked in on the project, I learned that it had been killed. NASA barred me from calling Liou again.
And yet, as Liou’s own models show, a new orbital catastrophe is only growing more probable. Mega-constellations of satellites, such as Elon Musk’s Starlink, are being put into orbit; by one estimate, at the current rate, there will be fifty thousand new satellites serving the Internet in ten years. Meanwhile, in the low exosphere, the environment continues to degrade. This January, many miles above Pittsburgh, a decommissioned telescope and a defunct military satellite missed each other by roughly fifty feet. In May, a twenty-ton Chinese rocket nearly fell into Central Park, instead smashing into the Atlantic off West Africa—a reminder that there are huge masses moving at immense speeds not so far above the surface of the Earth. Almost simultaneously, a Russian Fregat rocket blew up hundreds of miles above the Indian Ocean. As best as could be discerned, it fragmented into sixty-five more pieces. The NORAD catalogue had to be updated. ♦