An old Russian motor has exploded in orbit, creating a further 16 shards of potentially hazardous debris.
The Russian SOZ ullage motor (also known as ullage rockets) was put into orbit 15 years ago, when the GLONASS satellites were launched in 2007. The motors are used to help boost payloads – in this case, a Russian satellite navigation system – into their required orbit. In Zero-G, fuel can float away from where it is required, especially after a craft reduces acceleration. It is the job of the ullage motors to gently accelerate the whole spacecraft, pushing propellant back into position within the tanks ready for the main engines to restart in orbit. Without it, probes or spacecraft could become stranded, as the fuel floats away from where it is needed.
However useful they are, they aren't without their problems.
"The SOZ motors don't use up all their propellant when they fire. And they have an unfortunate tendency to go bang years or decades later, leaving a bunch of debris in highly elliptical orbit," Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics wrote on Twitter. "At least 54 SOZ motors have now exploded."
The latest explosion, announced by the U.S. Space Force’s 18th Space Defense Squadron on Twitter on Tuesday, saw the rocket break up into at least 16 pieces, which are now being tracked. This particular motor will likely reenter the Earth's atmosphere, though it could take years or even decades.
"173 debris objects from those explosions are currently being tracked, but the true number is probably a lot higher because tracking is less complete for high orbits," McDowell added.
Space, it's fair to say, is getting pretty crowded with junk. One concern about debris is that it could cause the "Kessler Effect" (or Kessler Syndrome). Simply put, the Kessler Effect is where a single event (such as an explosion of a satellite) in low-Earth orbit creates a chain reaction, as debris destroys other satellites in orbit. Should this happen, the debris could keep colliding with other satellites or other debris, potentially causing communication problems and leaving areas of space inaccessible to spacecraft. Essentially, it could end up like the film Gravity, but with less George Clooney and more "hey what happened to my GPS". At worst, some speculate it could essentially trap us here on Earth, unable to leave.