The International Space Station Just Jettisoned the Largest Piece of Space Junk Ever. We Asked a Space Debris Expert What to Expect.

The 2.9-ton pallet of old batteries are traveling towards Earth at 4.8 miles per second.

An external pallet packed with old nickel-hydrogen batteries is pictured shortly after mission controllers in Houston commanded the Canadarm2 robotic arm to release it into space. [Credit: NASA]

The International Space Station just discarded 2.9 tons of old batteries — the largest piece of space debris to be dropped from the space station to date.

Engineers in Houston used the Canadarm2 robotic arm to drop the pallet of nickel-hydrogen batteries from the space station’s orbit, 260 miles above Earth. A NASA statement explained the pallet of batteries will orbit Earth for two to four years “before burning up harmlessly in the atmosphere.”

The Canadarm2 robotic arm, with an external pallet packed with old nickel-hydrogen batteries in its grip, is pictured as the International Space Station orbited 260 miles above the Sahara in the African nation of Chad. [Credit: NASA]

The batteries were used to store energy collected from solar arrays. The ISS recently completed a four-year initiative to upgrade the space station’s batteries from nickel hydrogen to lithium-ion. On a February 1 spacewalk, astronauts Mike Hopkins and Victor Glover, who traveled to the ISS on the SpaceX Crew-1 mission, completed the last of the battery upgrades, and NASA made the decision to discard the old ones.

“The External Pallet was the largest object — mass-wise — ever jettisoned from the International Space Station. At 2.9 tons, [it’s] more than twice the mass of the Early Ammonia Servicing System tank jettisoned by spacewalker Clay Anderson during the STS-118 mission in 2007,” wrote NASA spokesperson Leah Cheshier in an email to Gizmodo.

The pallet is currently being tracked by U.S. Space Command.

We spoke with Dr. Roger C. Thompson, senior engineer specialist at the Center for Orbital and Reentry Debris Studies (CORDS) at The Aerospace Corporation about the battery jettison, reentry and future of space debris.

What will ultimately happen to this pallet?

The altitude of the EP Battery pallet will decay over time until it is low enough to reenter in a final “plunge” into the atmosphere. Then it will ignite and burn up due to the intense heat of reentry.

This is the heaviest single piece of garbage to be jettisoned from the International Space Station. Is this concerning?

There isn’t really anything to worry about. Most if not all of the mass will burn up in the atmosphere. Also, there is a 66% chance of anything that survives reentry, again if there is anything that survives, will land in the ocean because water covers 2/3 of the Earth’s surface.

What is the biggest threat from space debris?

The biggest threat from space debris is to other satellites in orbit. There is so much space debris that satellite operators have to plan several times a year to maneuver to avoid a collision. Some space debris does survive reentry, but those are most often empty propellant and pressure tanks which are very low density. High density objects like the batteries from the ISS are more likely to burn up completely. There is an extremely small risk that reentering object will hit someone. It is so small that if I knew there was a reentry near where I live, I would go outside to watch it!

How does Aerospace help with managing orbital debris?

Aerospace works with the government to design satellite architectures that consider debris risk. Orbit choices take into account both on-orbit risk and post-mission disposal to minimize future debris. Aerospace works with government and contractors to design spacecraft that can maneuver to avoid collisions, withstand small debris strikes, and move to disposal orbits or reenter the Earth’s atmosphere at end of life. If a spacecraft is intended for reentry, Aerospace considers design changes that will minimize the risk to life on the ground from falling debris.

We also screen launch trajectories to avoid collisions with any tracked objects and compare all potential launch trajectories at all possible launch times to calculate the positions of all tracked space debris. Aerospace aggressively seeks new ways of computing close calls with space debris, and of developing better processes to ensure smooth operations.

Where can people track the ISS battery pallet?
Several sites track different space objects, including our own CORDS Reentry Database. Track the descent of the ISS battery pallet here.

We operate the only federally funded research and development center (FFRDC) committed exclusively to the space enterprise.