There are many unknowns in the field of space exploration. What came before the Big Bang? What is dark matter? Will we ever make contact with another civilization, or are we destined to remain alone, floating along on this tiny, insignificant speck in the universe?
The latest unknown to captivate the space community is something a little less grand: Where is that giant rocket going to land when it falls out of the sky?
The rocket in question belongs to China, and it is currently hurtling through the atmosphere, circling the planet about every 90 minutes, toward what is known as an “uncontrolled reentry” sometime this weekend. The expendable hardware was once part of a larger vehicle, the Long March 5B, which launched last month with the first piece of China’s new space station. Once the payload successfully reached space, the rocket, emptied of fuel, slipped away and became space junk.
Launch providers usually try to ensure that their discarded rocket bits descend soon after a flight, and the hardware mostly falls into the ocean, though some pieces, on rare occasions, hit land. But this empty rocket is different. The Long March 5B vehicle was designed in such a way that its expendable rocket ended up in orbit, tumbling around at more than 17,000 miles per hour. Parts of the rocket are expected to survive the fiery reentry through Earth’s atmosphere and reach the surface, and who knows where they might land? The U.S. military is tracking the object, but even the best available data can’t predict its final destination.
Considering the size of this thing—nearly 100 feet tall, more than 15 feet across, weighing 23 tons—the idea of even parts of it hurtling toward us is particularly unnerving, enough that a friend whom I haven’t seen in ages sent me this text message last night: “Are you following this China rocket thing? Are we doomed??"
No one is doomed! Not because of this, at least. While the chances are not zero, the likelihood that debris from the Long March 5B will drop onto a populated area is extremely low. Even without a controlled entry, it is far more likely to smash into the ocean, which our planet thankfully has a lot of. (Honestly, the reentry we should probably be more preoccupied with is the return to social interaction after vaccination.) Stuff falls into the atmosphere every day, burning up as it goes. You’re more likely to get struck by lightning than smacked with a piece of falling space debris.
“The chance of someone being hurt is maybe a percent or so,” Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics who is well known in the space community for his expert monitoring of artificial space objects, told me. “The chance of you being hurt is 8 billion times smaller than that, so don’t worry about it.”
Careening, out-of-control space debris is one of those problems that we hear about precisely because it’s so rare. It’s also quite solvable, McDowell said—just don’t build your rocket, as China did, to reach orbital velocity and start zooming around. The few times that very large pieces of space junk have come crashing down to Earth over the years—rockets, satellites, even entire space stations—no one was doomed.
In the 1970s, Skylab, the first American space station, came plummeting through the atmosphere. NASA astronauts had used the floating outpost to conduct science experiments and generally get the feeling of life in microgravity. By the end of the decade, the station, now abandoned, started losing altitude. The station wasn’t designed to maneuver itself into a higher orbit, and the space shuttles that NASA thought could help haul it up weren’t ready yet, so down the station went. NASA did have the power to give it a nudge or two, but mostly Skylab was carving its own path.
In 1979, as the public followed the station’s descent with, according to Time magazine, “varying degrees of fear, anger and fascination, but mostly with a detached kind of bemusement,” NASA controllers worried that some debris could hit North America. The Federal Aviation Administration even closed off airspace over Maine to protect planes. Hours before reentry, engineers commanded Skylab to fire some engines and produce a wobble that would adjust its path just a bit, bringing its descent over the ocean. The last-minute adjustment was partly successful; most of Skylab fell into the Indian Ocean, but some debris was scattered along the coast of western Australia. Suddenly, space litter became a souvenir, and people scoured the coast for remnants of Skylab, eager for a trophy or something to sell. The city council of Kalgoorlie even hauled a piece of the station into its town hall, which the mayor said was “very good for the tourist industry."
When something is moving as fast as Skylab was—or the Long March 5B is now—even the slightest shift can change its trajectory by thousands of miles, bumping it from one continent toward another. NASA’s decision pushed Skylab “to fly safely over southern Canada and Maine, but may have been responsible for its Australia landing,” The New York Times reported. President Jimmy Carter even apologized to the Australian people for the mess.
An empty Soviet space station came down in 1991 in a similarly uncontrolled manner over Argentina, appearing as a fireball in the sky. Some debris managed to reach the ground, igniting small fires in a trash dump in a southern coastal city, but there were no injuries. More recently, a Chinese space station, Tiangong-1, fell back to Earth in 2018, burning up over the South Pacific, with remnants landing in the water near Tahiti. Chinese officials had lost contact with the spacecraft two years earlier, sparking anxious speculation about where the out-of-control station would come down. Last spring, a disintegrating Long March 5B rocket sailed directly over Los Angeles and New York City on its final orbit of Earth before entering the atmosphere over the Atlantic Ocean and raining debris in the Ivory Coast in Africa. Again, no one was injured.
So, yes, the Long March 5B does not threaten immediate catastrophe. But it’s still not great, and China isn’t doing much to alleviate worries. The country is known for being secretive about its space activities, both at home and abroad. Foreign-ministry officials declined to answer questions about the reentry at a press conference this week, saying only that China is “committed to the peaceful use of outer space and stands for international cooperation in this regard.”
Already the White House press secretary has fielded questions about what the Biden administration would do if the rocket causes damage on Earth. Although one might imagine that fiery events that cross international borders would have inspired some kind of serious regulation, there’s no space law covering objects plunging to Earth. It’s up to nations to supervise their own space objects and where they fall. “In terms of the legal mechanisms governing reentry, there actually aren’t any obligations on this. There isn’t any international treaty,” Chris Newman, a space-law professor at Northumbria University at Newcastle, in the United Kingdom, told me.
But there are some rules about who’s responsible if space litter damages property or injures people. Many countries are party to the 1972 Space Liability Convention, which allows one nation to hold another financially responsible for space litter. In 1978, after a fallen Soviet satellite scattered radioactive debris over northwestern Canada, the Canadian government asked the Soviet Union to fork over $6 million to cover cleanup efforts; the Soviet Union waffled for a few years, but eventually paid $3 million. This rule comes with all sorts of political entanglements, Newman said; if the Long March rocket does cause damage somewhere inhabited, the leaders of that country may decide that seeking recompense isn’t worth the potential diplomatic ripple effects of challenging China. “This is going to be a foreign-policy decision as much as a legal one,” Newman said.
A more pressing concern about space debris involves the type that most people don’t notice or worry much about. The space around Earth is brimming with satellites, rocket parts, and other hunks of metal, and some objects occasionally pass dangerously close to each other and even collide. Space law doesn’t have much to say about space traffic either, but space is getting more congested every day, even without a rogue rocket.