Starlink Burns Up One to Two Satellites a Day

upstart writes:

Kessler syndrome is bad; atmospheric incineration may be worse:

If you had to guess how many Starlink satellites burn up in Earth's atmosphere on an average day, how many would you pick? This isn't a trick question - SpaceX is deorbiting about one or two satellites daily, and that number is only going to grow.

What that means for our planet isn't entirely clear, says Harvard astrophysicist and space tracker Jonathan McDowell. Even so, Starlink isn't the space junk risk that some other satellite operations are.

McDowell commented on the massive volume of reentering Starlink satellites to science news site EarthSky last week. He explained that once Starlink and other planned low Earth orbit constellations together total about 30,000 satellites, roughly five could reenter the atmosphere each day, given an average replacement cycle of around five years.

[...] Starlink isn't the biggest concern when it comes to passing the Kessler tipping point, McDowell told us - but it is still a source of worry.

"Active satellite maneuvers to avoid collisions will help avoid Kessler," McDowell said in a phone conversation. "If they're successful. And that's a big if."

The current strategy to de-orbit Starlink satellites, which operate in a low orbit below 600 kilometers, is to use the satellites' thrusters to move them to such a low orbit that they eventually catch drag in the atmosphere and burn up in what McDowell calls an "uncontrolled but assisted" reentry.

Purposeful de-orbiting, plus successful dodging, mean we can avoid Kessler syndrome, McDowell told us.

[...] Excepting the possibility of unplanned disaster, Starlink's operations aren't the biggest concern, McDowell added. China's satellite plans are far more worrying.

"The region of space closest to Kessler is the 600 to 1,000 kilometer range," McDowell said. "It's full of old Soviet rocket stages and other stuff, and the more we add there, the more likely it is for Kessler syndrome to occur."

While many of China's proposed satellite constellations are going to be in low Earth orbit at the same altitude as Starlink, McDowell noted that a number are planning to fly above 1,000 kilometers. Were something to go wrong up there, McDowell noted, "we're probably screwed."

"That higher altitude means the atmosphere won't drag them down for centuries," McDowell added. "And I haven't seen [China] demonstrate any retirement plans for those satellites."

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