June 21, 2024
1 Solar System Way, Planet Earth, USA

Uncontrolled re-entry of space debris poses a real and growing threat

In March, a high-speed cylindrical object, approximately 0.7 kilograms in mass, crashed through the roof of a home in Naples, Florida, crashing through a roof and through a floor.

NASA later confirmed that the object was an International Space Station object: a small remnant of a multi-ton platform discarded and released about three years earlier.

That multi-ton Exposed Pallet 9 (EP9) hardware was loaded with 2,631 kilograms (5,800 pounds) of spent nickel-hydrogen batteries. The platform itself had been transported to the ISS via a Japanese cargo ship carrying Orbital Replacement Units of high-tech lithium-ion batteries, swapping them out for the old nickel-hydrogen batteries that were jettisoned into space.

Sent to wander through space over the years, EP9 and the collection of spent batteries were meant to meet their fiery end by plummeting into Earth's atmosphere, but at least one fragment survived the journey.

That event, and subsequent confirmation that the errant object was, in fact, an old piece related to the ISS battery, has raised worrying opinions about the escalation of human-made space debris falling to Earth uncontrollably.

Debris evaluation

There was a bit of detective work in evaluating the Florida object's pedigree.

Joshua Finch, a spokesman for the Kennedy Space Center, provided a NASA statement on the matter to SpaceNews.

“NASA's Kennedy team initially evaluated the owner's photographs and noted key features still present in the debris, similar to a NASA flight support equipment strut used to mount the batteries on the charging pad,” explains the NASA team. NASA statement.

To determine the origin of the debris, the team examined configuration and shipping documentation for battery flight support equipment sent by the agency to Japan for installation on the exposed platform that was lifted in 2020 via the Japanese cargo ship. HTV-9.

“This investigation yielded the correct part number for the strut, and when reviewed, the engineering drawings confirmed the same key features found in the images,” NASA said.

A new battery mount was obtained from the space station's parts inventory and compared to debris for positive visual confirmation, NASA added.

This object survived re-entry through Earth's atmosphere on March 8, 2024 and collided with a house in Naples, Florida. NASA analysis found that it was a stud recovered from NASA flight support equipment used to mount the International Space Station's batteries on a cargo platform. Credit: NASA Kennedy Space Center

“The team also had NASA's Kennedy Chemistry and Metrology Laboratories evaluate the debris to determine dimensional and material properties and compare the results to engineering drawings. “Finally, X-ray equipment and dimensional analysis confirmed that all debris properties matched engineering drawings for a space station main battery strut, most likely used on HTV-9,” the statement concluded. from NASA.

Wanted: data exchange

“I'm pretty sure there are more surviving fragments,” said Tobias Lips, managing director of Hyperschall Technologie Göttingen in Bovenden, Germany. As a reentry analysis specialist, he simulated the fall of the ISS battery pallet days before the actual reentry event.

“But some of them could have fallen into the ocean before reaching the Florida coast,” Lips said. Some pieces, however, could have landed on dry land and gone unnoticed as typical terrestrial remains, Lips added. “Imagine you see a piece like this on the street. What would you think?”

Lips said he expects (but hasn't yet seen) some international cooperation, such as agreeing on which modeling tools to use and sharing data.

Risky readmissions

“Companies and governments continue to abandon objects in orbit instead of responsibly disposing of them through controlled re-entries,” said Ewan Wright, Ph.D. candidate at the University of British Columbia and a junior fellow at the Outer Space Institute. “In any other industry, this abandonment would be illegal, but since it's in space, it's out of sight and out of mind… until it crashes again.”

“In this case, someone's house was hit and someone was inside. The consequences could have been much worse,” Wright said. “Equally risky re-entries occur weekly, meaning the chance of someone somewhere being hit is considerable.”

Researchers are still unsure how exactly space debris burns up in Earth's atmosphere, Wright said, as the ISS battery episode illustrates. “In this case, NASA's models were wrong. With more satellites and rockets launched each year, the potential consequences of this uncertainty are increasing,” he stated.

Dragon Trunk Fragments

The Florida impact may not be as rare an event as it seems, as more space debris appears to have reached dry land even more recently.

The latest incident, on May 21, occurred inside The Glamping Collective, a secluded 160-acre mountaintop site featuring outdoor travel and leisure structures near Clyde, North Carolina. A field worker at the site reported finding a large object, now believed to be fragments of the discarded trunk associated with the SpaceX Dragon Crew-7 mission.

Space object tracker Jonathan McDowell had previously posted via X that the SpaceX trunk re-entered the atmosphere over Birmingham, Alabama. Given its northeastward trajectory, possible debris could have fallen in Tennessee, western Virginia and West Virginia, he said.

Clutter has also been found in the trunk of SpaceX in Australia and Canada.

Increasingly common event

The problem of incoming space junk It's not going away anytime soon. In fact, the problem appears to be getting worse, experts said. SpaceNews.

Tommaso Sgobba, executive director of the International Association for the Advancement of Space Security, said SpaceNews that the rule that currently governs uncontrolled re-entry (what he called Rule 10-4/event which dictates that “uncontrolled re-entry is permitted if the probability of casualties on the ground is less than 1 in 10,000 re-entries”) is “obsolete because it is “refers to a time when reentries were a rare event.”

“Uncontrolled re-entries must be prohibited,” added Sgobba, who previously headed the European Space Agency's Independent Safety Office.

Sgobba said the risk that debris poses to Earth's population depends on the kinetic energy and composition of the falling object, as well as population density. He added in an email that he supports prohibiting uncontrolled reentry unless the probability of risk is less than one in 100,000. Both large and light debris pose less of a risk on land, he said; Even a 300-gram piece of debris would be considered catastrophic for an aircraft in flight.

Carmen Pardini, from the Space Flight Dynamics Laboratory of the Institute of Information Sciences and Technologies of the National Research Council in Pisa (Italy), has published articles focused on uncontrolled re-entries, with special attention to mitigating the risks posed by their fall to Earth. “Based on our analyzes over several decades, the overall risk posed by uncontrolled re-entries is increasing,” Pardini said. SpaceNews.

Furthermore, the situation is changing rapidly.

“In the coming years, in fact, while the expectation of casualties on the orbital stages could remain basically stable, or increase slightly, that of the satellites could progressively increase by a factor of 20 or more,” Pardini said. “Therefore, it is necessary to take effective mitigation measures as soon as possible, for example by requiring the widespread adoption of controlled deorbits for large orbital stages, satellites and discarded payloads.”

The problem must be addressed now, Pardini said, while new launchers and large constellations of low-orbit satellites are developed and deployed, “otherwise the situation is likely to get out of control within a decade.”

This article first appeared in the June 2024 issue of SpaceNews. Magazine.

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