After nearly three years of careening around Earth, a bundle of exhausted batteries from the International Space Station fell out of orbit and re-entered the atmosphere on Friday. It’s likely that the majority of the debris burnt up on reentry, but some pieces might have made it to Earth’s surface undamaged.

Bigger space junk fragments frequently descend to Earth on random paths; nevertheless, these are mostly abandoned spacecraft or spent rocket stages. This concerned a pallet of space station batteries weighing more than 2.6 metric tons (5,800 pounds). NASA purposefully set the space debris on a course for an uncontrolled descent.

Self-Cleaning by Nature

NASA “conducted a thorough debris analysis assessment on the pallet and has determined it will reenter the Earth’s atmosphere harmlessly,” according to NASA spokesperson Sandra Jones. This was by far the largest thing that the International Space Station has ever thrown overboard.

US Space Command reports that the batteries reentered the atmosphere around 2:29 p.m. EST (1929 UTC). The pallet would have been flying between Mexico and Cuba at that point. According to Jones, “We do not expect any portion to have survived reentry,” Ars said.

The battery pallet’s trajectory was also seen by the European Space Agency (ESA). The ESA stated last week that although there is “very little chance” that a human will be struck by a piece of the pallet, “some parts may reach the ground.” Astrophysicist Jonathan McDowell, who keeps a close eye on spaceflight operations, calculated that roughly 500 kg (1,100 lbs) of debris would collide with Earth’s surface.

“The general rule of thumb is that 20 to 40 percent of the mass of a large object will reach the ground, though it depends on the design of the object,” according to the Aerospace Corporation.

On February 21, a deceased ESA satellite similarly reentered the atmosphere without warning. This satellite weighed about 2.3 metric tons, which was comparable to the abandoned battery pallet. A website offering daily tracking information on the satellite’s declining orbit was established by ESA, an organization that prides itself on being a global leader in space sustainability.

Officials from NASA and ESA have stated that there is very little chance of harm or death from a spacecraft reentry. Death from falling space debris is a myth. The European Space Agency (ESA) estimates that the probability of an individual being struck by space debris is around 65,000 times lower than that of a lightning strike.

Because of the peculiar nature and source of the trash in orbit, NASA purposefully sent it hurtling back toward Earth on an unpredictable course.

On March 11, 2021, the robotic arm of the space station released the pallet containing batteries. The batteries have been floating in orbit ever then, revolving around the earth roughly every 90 minutes. The effect of aerodynamic drag allows low-Earth orbit to self-clean over months or years. The pallet’s speed was progressively reduced by the resistance of rarefied air molecules in low-Earth orbit until Friday, when gravity eventually forced it back into the atmosphere.

The cargo pallet transported six new lithium-ion batteries to the International Space Station when it launched in 2020 onboard a Japanese HTV cargo ship. With the help of astronauts on spacewalks, the station’s two-armed Dextre robot replaced its outdated nickel-hydrogen batteries with the updated ones. Before the HTV cargo pallet was released from the robotic arm of the station, nine of the old batteries were placed on it.

Delayed Repercussions

NASA does not like to dispose of waste in low-Earth orbit, despite its study indicating that the abandoned battery pallet would burn up on descent. Launch providers are required by NASA to hold onto enough propellant in reserve during satellite launches so that the rocket’s upper stage can be removed from orbit or diverted to a path that won’t interfere with other missions.

Following their supply delivery to the International Space Station, cargo ships haul tons of junk and extra equipment out of the outpost. This cargo is returned to Earth undamaged by SpaceX’s Dragon capsule, while waste is disposed of by autonomous supply ships from Northrop Grumman and Russia using targeted destructive reentries over the ocean.

Nine voyages to the ISS saw a similar use of Japan’s HTV cargo freighters. As part of a mid-life upgrading of the lab’s electrical system, 24 of the upgraded lithium-ion batteries were carried to the station by four Japanese resupply flights.

Initially, officials intended to launch the new batteries on the same HTV spacecraft that would be used to dispose of the majority of the old batteries. For long-term storage as spares, a portion of the older batteries were kept on the station.

The HTV was still attached to the space station, but the batteries were replaced automatically with assistance from astronauts participating in spacewalks. The initial plan was to robotically load the battery tray back into the HTV before departure, retrieve the fresh batteries from the cargo pallet of the HTV, and replace the old batteries. The HTVs reentered the atmosphere over the South Pacific Ocean after departing the station. The majority of the spacecraft and battery gear caught fire, and what was left of them plummeted into a secluded area of the ocean.

This plan was followed by NASA until 2018, when Russian commander Alexey Ovchinin and NASA astronaut Nick Hague were unable to reach the space station due to a Soyuz launch mishap. The crew members arrived in Kazakhstan without incident, but Hague was meant to assist with installing the new batteries that an HTV cargo ship had brought to the station a few weeks earlier.

Hague remained on the ground while the robotic arm of the station took the battery pallet out of the HTV and stored it until a fresh crew of astronauts was available to install them. Finally, the robot arm completed its task by releasing the Japanese cargo ship. This broke the cycle of exchanging new batteries for old ones, and every HTV mission after that left the cargo pallet from the previous HTV behind when it left the station.

However, the HTV program was discontinued in 2020, and the battery pallet, which is roughly twice as tall as a typical refrigerator, cannot be loaded onto any of the station’s other cargo freighters. There was no way to get rid of the last nine batteries on the tray because the new Japanese freight spaceship, the HTV-X, had not yet taken to the air.

Without any propulsion of its own, the cargo pallet couldn’t steer itself toward reentry over an unpopulated area. The space station’s orbit takes it between 51.6 degrees north and south latitude. “Large uncertainties, primarily driven by fluctuating levels of atmospheric drag, prevent more precise predictions at this time,” ESA said Thursday. “The closer we get to the expected reentry window, the better the concerned region can be geographically constrained.”

US Space Command’s return projection initially shrunk to a six-hour window, then to four hours early on Friday. Later, at 2:29 PM EST (1929 UTC), Space Command verified in a Trajectory Impact Prediction (TIP) communication that the pallet had descended from orbit, or had reentered the atmosphere.

Topics #Earth #International Space Station #NASA