[nonesuchluck]

550km is also just the operational altitude. SpaceX initially releases satellites in a much lower initial orbit. If they fail to POST, they fall into the atmosphere months after launch. Starlink climbs slowly to 550km with the same ion thrusters used for station keeping. SpaceX does not want dead birds in their orbital shell.

[shagie]

Looking more closely at https://in-the-sky.org/spacecraft.php?id=45203 - that makes sense. Its released right about 350 km in a rather eccentric orbit which is then stabilized at just under 400, then after about a month there, it climbs to its target orbit over the course of a month up at 550km.

A more natural one is https://in-the-sky.org/spacecraft.php?id=45229 which has the same initial orbit pattern.

The key thing with this is that without anything else, the satellite has a lifespan that is measured in months to years and up to a decade... not centuries. A Kessler syndrome at 550km would certainly be rather up there on the "suck" scale, but wouldn't keep humanity grounded for more than a decade.

One of the important things to remember about debris at a given altitude, without additional energy, an object cannot climb further out of the the gravity well into a higher orbit. It will always come back to the same spot in its orbit one orbital period later.