The International Space Station (ISS) recently had to activate the thrusters of a docked spacecraft in order to change its trajectory. The aim of the maneuver was to avoid debris that has been orbiting the Earth for more than seventeen years, remnants of a military test ordered by the Chinese government during which a missile had destroyed a satellite (also Chinese). It was the second time in just six days that the ISS had to perform such an action, the shortest interval between two maneuvers of this type, explains an article in the Washington Post.
Space debris in orbit is a problem that is getting worse every day and whose management is particularly complex. Projects like SpaceX’s Starlink rely on launching thousands of small satellites to provide high-speed Internet access anywhere in the world, but those satellites must be protected from debris in orbit—a real headache. And the Chinese space missile test has not helped the situation.
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According to analysts, the most worrying threat is the cloud of debris from Fengyun 1C, the weather satellite intentionally destroyed by a Chinese missile in 2007. The US Space Force estimates that there are 3,500 pieces of debris generated the explosion, and a majority are still orbiting the Earth today. With each new passage, their trajectory changes slightly and the debris descends, which suggests a way out: their disintegration in our atmosphere.
Unfortunately, one study says it would take more than 100 years for this to happen. “A decade and a half later, we still see problems because this debris continues to fall”said Marlon Sorge, executive director of the Aerospace Corporation’s Center for Orbital Debris and Debris Reentry Studies. Since 2012, NASA says, the ISS has already had to dodge remnants of Fengyun 1C five times, the last of which was as recently as November 25. More generally, since 2020, fifteen maneuvers of this type have been carried out to avoid space debris. Last month’s six-day interval is “just a statistical fluctuation”explained Harvard astrophysicist Jonathan McDowell, “but it is true that the problem is slowly getting worse”.
1 chance in 100,000
Obviously NASA is very careful, and during the last operation in November, the passage of debris did not directly represent a danger for the four NASA astronauts and the three Russian cosmonauts present on board. A collision was not guaranteed, and the ISS may be “the best armored spacecraft ever launched” as the American agency states, but prevention is better than cure. If only to avoid a scenario like Gravity.
At more than 27,000 kilometers/hour, even a tiny object can cause significant damage. In 2021, the astronauts of the ISS had to take refuge in adjacent vessels, already after a military test destroyed a satellite, this time Russian. To be alerted in time, the ISS relies in particular on the network of telescopes, radars and sensors of the American Space Force. This grid of our orbit makes it possible to identify fragments of less than 10 centimeters which could fly into the security perimeter surrounding the station.
If the chances of collision are greater than or equal to 1 in 100,000, NASA moves the ISS. Thus, on November 25 (and after consulting the Russian space agency Roscosmos), it was decided to activate the thrusters of Progress 89, a Russian vessel which was then docked to the ISS, for approximately three minutes. and thirty seconds. Just enough to get out of harm’s way.
«The Space Force issued about 700 “conjunction” notifications last month, or about twenty-three per day, according to Erin Leon, director of public affairs for the Space Force. Five years ago, when space was less crowded, this figure was only six per day»explains the Washington Post. A job which is not made easier by certain countries such as China and Russia which do not communicate the details of their launches, nor their actions in orbit, complicating the monitoring of debris and the risk of collision.
This lack of transparency can pose a problem, explained Gwynne Shotwell, president of SpaceX, during a presentation at the Center for Strategic and International Studies. “If you don’t know where things are deployed, you can’t predict potential collisions or decide if you need to move”she concluded.
