The International Space Station became a bit lighter last week.
The orbiting lab on Thursday morning (March 11) discarded a pallet of used batteries weighing 2.9 tons (2.6 tons) – the most massive object it has ever thrown overboard, NASA spokesman Leah Cheshier told Gizmodo.
The space junk is expected to fall back to Earth within two to four years, agency officials wrote in an update last week. The update also stated that the pallet will burn “harmlessly in the atmosphere”, but not everyone is convinced that it is.
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“This seems dangerous to me (haha, a pun given the circumstances). It seems big and compact, so it’s unlikely to burn out completely,” astronomer and author Phil Plait, whose blog “Bad Astronomy” runs on Syfy Wire, wrote on Twitter Thursday.
“Yes. On the other hand, for example, Tiangong-1 weighed 7500 kg [kilograms], much bigger. But I would say, given how close EP9 is, it is alarming, albeit on the low side of alarming, ” responded astronomer and satellite Jonathan McDowell, which is located at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
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Tiangong-1 was the first prototype of China’s space station, which hosted astronaut crews in 2012 and 2013. The school bus-sized craft finally crashed back to Earth over the South Pacific in April 2018.
EP9, short for “Exposed Pallet 9”, is the recently discarded object. EP9 came to the station last year on a Japanese H-II Transfer Vehicle (HTV) as part of the effort to replace the orbit lab’s old nickel-hydrogen batteries with new lithium-ion batteries – an extensive process that will require a number of spacewalks in the past five years.
Previously, the old batteries were packed in the disposable HTV, which took them to doom in Earth’s atmosphere. But the failed launch of a Soyuz rocket with NASA astronaut Nick Hague and cosmonaut Alexey Ovchinin in October 2018 disrupted this pattern, Spaceflight Now reported. (Hague and Ovchinin eventually landed safely, thanks to their Soyuz capsule’s launch-abort system.) And EP9 came out on the ninth and final HTV, meaning there was no doomsday ride.
So space station managers decided to toss the battery-packed pallet overboard. On Thursday morning, ground controllers at NASA’s Johnson Space Center in Houston commanded the orbit lab’s 17.6-meter robotic arm to put EP9 into orbit, NASA officials wrote in the update.
The SUV-sized pallet has plenty of room clutter up there. According to the European Space Agency, researchers estimate that Earth’s orbit is full of about 34,000 debris objects at least 4 inches (10 centimeters) wide and 128 million pieces that are 1 millimeter wide or larger.
Mike Wall is the author of “Outside(Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the quest for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.