An old Russian engine that’s been aimlessly floating through space for more than a decade has finally met its demise in a sudden explosion, producing at least 16 shards of orbital debris that now threatens satellites and other objects.
On Tuesday, the US Space Force’s 18th Space Defense Squadron confirmed through Twitter that a SOZ ullage engine exploded in space on April 15. At least 16 pieces of debris were created by the event, which the defense squadron is now tracking. The engine was used to launch three Russian GLONASS satellites in 2007, boosting them into the right orbit once they were in space. The motor had been orbiting idly in space since then, but with leftover high energy rocket propellant still packed inside.
“It’s sort of like a little bit of a time bomb, but without an actual timer,” astrophysicist Jonathan McDowell from the Harvard-Smithsonian Center for Astrophysics told Gizmodo.
Something likely happened within the engine that involved the rocket propellant, causing it to explode. Unfortunately, this isn’t the first time a discarded SOZ ullage engine has made a big mess in space. At least 54 of these motors have already exploded, and there are about 64 of them still in orbit, according to McDowell. This latest motor breakup incident is adding to the mounting problem of space debris, or space junk, caught in Earth’s orbit.
“When I saw this, I was massively unsurprised,” he said. “These things have been popping off once or twice a year for many years, and it’s really been a problem.” The motor is an older Soviet rocket design left over from the Cold War, whereas newer designs of spacecraft are designed to avoid these issues. “This particular issue of leftover rocket stages blowing up has mostly been designed out in modern rockets,” McDowell said. “The best practice nowadays is to passivate spacecraft when they’re at the end of their mission.” Spacecraft passivation is the removal or deactivation of all potential sources of explosions.
But even if these older designs are no longer being sent to space, the pre-existing population of these relic motors could continue to generate more debris, and create further risks to satellites, which could in turn result in even more debris—a serious problem known as Kessler Syndrome.
More than 27,000 pieces of orbital debris are tracked by the Department of Defense’s global Space Surveillance Network (SSN) sensors, with many more smaller pieces of debris in the near-Earth environment, according to to NASA. These uncontrolled pieces of junk, whether a retired satellite or a small chunk of metal, travel at high speeds, running a potential risk of crashing into an operational spacecraft and causing considerable damage.
In June 2021, for example, a piece of space junk crashed into the International Space Station, damaging one of its robotic arms. Later in November, astronauts aboard the ISS had to take shelter from a cloud of space debris generated by the destruction of the defunct Russian satellite Kosmos-1408—the result of a reckless Russian anti-satellite test. China’s anti-satellite test in 2007 created more than 3,000 pieces of large debris.
Space agencies are hoping to find solutions to the ongoing orbital littering, with the European Space Agency recently commissioning the first debris removal mission, currently slated for a 2025 launch. The ClearSpace-1 spacecraft will feature four arms designed to clean up space junk in Earth’s orbit.
Big pieces of space debris “have the most risk of not just blowing up, but of hitting each other and creating lots more debris,” McDowell said. “And so if you want to avoid a sort of chain reaction, then getting rid of the big ones is what you want to do, and I think that is going to happen.”