The ISS dumps 2.6-tonne hunk of space junk
Words by Mike Wall
The orbiting lab discarded a 2.6-tonne pallet of used batteries on 11 March, the most massive object it has ever jettisoned. The space junk is expected to fall back to Earth in two to four years. The pallet should burn up ‘harmlessly in the atmosphere’, but not everyone is convinced that’s the case. “This strikes me as dangerous. It seems big and dense, so unlikely to burn up completely,” tweeted astronomer and author Phil Plait. “On the other hand, Tiangong-1 was 7,500 kilograms, much bigger. But I would say given how dense EP9 is, it’s concerning,” responded astrophysicist Jonathan Mcdowell, based at the Harvardsmithsonian Center for Astrophysics. EP9, short for ‘Exposed Pallet 9’, is the recently jettisoned object. EP9 came to the station last year on a Japanese H-II Transfer Vehicle (HTV) as part of the effort to replace the orbiting lab’s old nickelhydrogen batteries with lithium-ion ones. Batteries were packed into the HTV, which carried them down to their doom in Earth’s atmosphere. But the October 2018 launch failure of a Soyuz rocket carrying Nick Hague and Alexey Ovchinin disrupted this. EP9 came up on the ninth and final HTV, meaning it was left without a doomsday ride. Space station managers instead decided to jettison the batterypacked pallet, and ground controllers at NASA’S Johnson Space Center in Houston commanded the orbiting lab’s 17.6-metre robotic arm to release EP9 into orbit.