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When the ISS Needs to Dodge
The ISS is 450 tons of spacecraft that’s mostly intended to stay put. Unfortunately, orbit is a little bit messy…much of it our fault…and every so often, the ISS crosses orbits with a piece of space junk.
The junk, of course, is on a fixed trajectory.
This means that a couple of times a year, the ISS has to engage in an “avoidance maneuver.” Which is a fancy way of saying that a 450 ton spacecraft has to dodge.
How does the ISS Avoid Debris?
The ISS is in a set orbit, but it is not in a 100% stable orbit. For the most part it handles station keeping by the use of 220-pound gyroscopes that keep the spacecraft balanced, stop it from tumbling, and secure its orbit.
To dodge, however, the ISS has to shift to a slightly different orbit. So, how do they do this? It depends on who’s at home.
If there is a Progress supply ship docked, then the supply ship uses its eight engines in a specific pattern that applies thrust safely to the station.
If not, then the Zvezda service module does have thrusters, although they are not as powerful and generally they try to use the Progress.
The ISS moves every time a ship docks to optimize the orbital transfer. They also have plans to raise the orbit because there is…