In what may be judged as a bizarre and twisted case of “breaking and entering,” last month a plummeting cylindrical object weighing nearly two pounds hit the roof of Alejandro Otero’s home in Naples, Fla., smashed through a ceiling and punched through a floor.
Although yet to be officially verified as such, the most likely explanation for this high-speed home invader appears to be that it’s a piece of space junk cast off from the International Space Station (ISS) in low-Earth orbit. As the latest close encounter with clutter from the cosmos, the space junk strike has already sparked technical and legal banter about the worrisome escalation of Earth-circling, human-made refuse.
As the saying goes, timing is everything. This event appears to have been years in the making, however.
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Taking Out the Trash
Back in March 2021 astronauts onboard the ISS used a Canada-supplied robotic arm to tip an abnormally hefty hunk of refuse into space—the heaviest object ever jettisoned from the space station, in fact. NASA explained at the time that the trash, called Exposed Pallet 9 (EP9), had the approximate mass of a large SUV “and is safely moving away from the station and will orbit Earth between two to four years before burning up harmlessly in the atmosphere.”
After being ferried to the ISS via a Japanese cargo ship the previous year, EP9 had been filled with 5,800 pounds of spent nickel-hydrogen batteries. But a series of logistical complications—chief among them the fact that the battery pallet could only fit in Japan’s cargo ships, of which there were no more to fly—left EP9 stranded, taking up precious space on the ISS. So NASA decided to throw it overboard. After a few years of drifting aimlessly through space, EP9 finally met its fiery fate on March 8 when its decaying orbit sent it nose-diving into Earth’s atmosphere over the Gulf of Mexico.
The European Space Agency’s Space Debris and Independent Safety Offices closely monitored the reentry of the pallet of used ISS batteries. These batteries were to undergo “a natural reentry,” said ESA in a pre-reentry communiqué, using a twist on the term for an uncontrolled plunge from space.
“The total mass of the batteries is estimated at 2.6 metric tonnes, most of which may burn up during the reentry,” ESA stated. “While some parts may reach the ground, the casualty risk—the likelihood of a person being hit—is very low.”
A Serious Candidate
Marco Langbroek, a devoted satellite tracker and a faculty member in aerospace engineering at the Delft University of Technology in the Netherlands, says it certainly does look possible that the object in Florida stems from the reentry of the EP9 battery pack.
Langbroek has reviewed EP9’s ground track as well as the reported timing and trajectory of its reentry. Handily, there’s also a time-stamped security video and sound clip of the object that pierced the homeowner’s roof.
After entering the atmosphere and losing much of its speed, the debris piece probably spent a couple of minutes in subsonic free fall, Langbroek says.
“Reentries take multiple minutes, with the object fragmenting and the reentering fragments spreading along the trajectory over a stretch that can be hundreds of miles long,” he adds. “Given the force of impact, I think this is a serious candidate for potential debris from this [EP9] reentry. It might well be a part of one of the nickel-hydrogen battery cells.”
There’s not much guesswork here, says Tobias Lips, managing director of satellite aerodynamics company Hyperschall Technologie Göttingen in Germany. As a specialist in reentry analysis, he robustly simulated the fall of the ISS pallet of batteries days before the actual event occurred using “moderately conservative” rather than “worst-case” assumptions. Even so, his results suggested more than 130 fragments would survive to reach the surface. That’s “about 10 times more than for a typical reentry object of this size and mass,” he says.
Most of those predicted fragments, Lips says, would be cylinders made of Inconel—a high-strength nickel-chromium superalloy often used in aerospace applications. Nearly 350 such cylinders were in the EP9 pallet’s payload of spent batteries, where they served as power cells. “The fragment found in Naples, Florida, is most likely one of these cylinders,” Lips says.
“The recovered fragment was reported to be about two pounds in weight. Thirty-eight percent of my [simulation’s] surviving fragments are within this mass class,” he explains. “I would be very surprised if investigations of this fragment don’t confirm it being a battery cell from the ISS.”
Ongoing Analysis
Whatever it is, the Florida object in question was handed over to NASA’s neighboring Kennedy Space Center. NASA spokesperson Joshua Finch tells Scientific American that in cooperation with Otero, the agency collected the item for deeper study to determine its origin. “More information will be available once the analysis is complete,” Finch says.
NASA’s analysis will likely begin with a rigorous examination of the object’s trajectory—as well as that of EP9—tracked against the locations of any other recovered debris, says Mike Weaver, a space debris expert at the Aerospace Corporation.
“In this case, the location of the object in Naples, Florida, appears to be consistent with the timing and the location of the ISS battery pallet reentry,” Weaver says. “However, this is not sufficient to positively identify an object.”
Alongside the trajectory work, scrutinizing the candidate chunk of space junk for signs of scorching, melting and other effects of reentry heating would be desirable, Weaver says. Metallurgical analysis to determine its composition could be useful as well.
Sometimes serial numbers or part numbers can be found on an object, Weaver notes, which would rapidly simplify things.
What Goes up Must Come Down
Threats from incoming orbital rubbish are real and set to grow, says Darren McKnight, a senior technical fellow at LeoLabs, a commercial provider of space domain awareness services, based in Menlo Park, Calif. As more space systems are deployed in low-Earth orbit, the old adage applies: what goes up must come down.
The vexing nub of the problem is that removing ever proliferating small pieces of orbital debris is vital for maintaining a safe space environment—and uncontrolled atmospheric reentry is by far the easiest way to do it. In fact, this happens automatically for objects in low-Earth orbit, which begin to fall as they bleed off momentum against the outer edges of our planet’s atmosphere. Yet the hands-off nature of this process means any sizable piece of unguided debris has a large swath of the planet upon which it or its fragments might fall, potentially constituting a low but real risk to multiple aviation corridors and population centers.
“The issue of aviation and ground hazard from space operations is a problem that will not go away any time soon,” McKnight says.
Legal Liability
If the downed debris in question is confirmed as coming from the ISS, a dialogue about liability would likely begin, says Joanne Gabrynowicz, a professor emerita of space law at the University of Mississippi and editor in chief emerita of the Journal of Space Law.
Some of the provisions of the United Nations Outer Space Treaty and its Convention on International Liability for Damage Caused by Space Objects, as well as the ISS International Governmental Agreement (IGA), could be relevant, Gabrynowicz says.
An analysis of various provisions in these sources and how they interrelate would probably be necessary, Gabrynowicz says, including Article II of the U.N.’s Liability Convention. Article II states that any country launching anything into space shall be responsible for damage any associated space objects may cause back on Earth’s surface.
In the case of an object striking a house, the launching nation would, at minimum, be liable for funding requisite structural repairs. Gabrynowicz adds, however, that while this protocol is simple in principle, its translation to reality can become extremely complex. Things get murky, for instance, if the errant object that struck Otero’s house is proved to be part of the spent batteries from EP9’s reentry: the batteries are NASA’s property, but they were attached to EP9—a payload launched by the Japan Aerospace Exploration Agency (JAXA).
“That could be complicated, requiring analysis of various contracts, treaties, insurance policies and the IGA. Of course, the entities involved can also agree as to how to resolve the situation,” Gabrynowicz concludes.
An Act of Abandonment
“NASA will want to minimize this by saying chucking stuff off the ISS is rare and this isn’t a satellite or rocket body ... and therefore is disconnected to increasing launch rates,” says Ewan Wright, a Ph.D. candidate at the University of British Columbia and a junior fellow of the Outer Space Institute.
“But clearly there is an issue here that uncontrolled reentries are fairly accepted, and nobody thought to look into it much further,” Wright says. One reason for laxity, he notes, is that the risks from uncontrolled space debris reentry are literally and figuratively dumped in the ocean, which covers most of Earth’s surface. But treating Earth’s seas as a space junkyard is unlikely to be sustainable forever.
“There are over 50,000 ships in the ocean at any given time and hundreds of thousands of smaller boats. The chance of a ship being hit by space debris is likely to be small, but it’s growing, and we don’t know the number for sure,” Wright says. “A cruise ship being hit by uncontrolled space debris may not kill someone, but it would raise serious questions about our continued abandonment of space debris in orbit. And the launching state would be liable to pay damages.”
Many aerospace companies employ an ethos of “design for demise” for their space-bound components to try to ensure that if the parts do reenter, they reliably burn up at high altitude. Yet even leaving aside growing concerns about the resulting contamination of Earth’s upper atmosphere with heavy metals and other pollutants, some experts consider the practice ill-advised at best.
Moriba Jah, an expert in space debris tracking and management at the University of Texas at Austin and a co-founder and chief scientist at Privateer Space, a group focused on space sustainability issues headquartered on the island of Maui in Hawaii, is one such critic.
Jah emphasizes that discarding our detritus in low-Earth orbit in hopes that this material will “naturally reenter” the atmosphere “is not a responsible disposal method but rather an act of abandonment.” Even if not legally classified as such, uncontrolled reentry “is inherently irresponsible due to the potential risks it poses to life and property on Earth,” Jah says.
In some sense, the unlikely intersection of a probable piece of orbital debris with a home could ultimately prove to be a good thing: it could provide another wake-up call to policymakers, major aerospace players and the public at large that when it comes to space junk in low-Earth orbit, the sky really is falling.