@thorny_locust : You seemed to be asking in the other thread about the risks Starlink presents to spaceflight in general, and presumably related to space junk mitigation efforts.
The short and sweet version is that Starlink aims for a 5-year maximum time in orbit after the end of useful activity. They accomplish this in a few different ways:
- The satellites are at a low altitude and experience a fair amount of atmospheric drag. The amount of drag varies based on solar activity, but within a 5-year window there is enough to bring the satellites down.
- The satellites have a low ballistic coefficient, which is just a fancy way of saying that they have a giant sail on them. There’s a lot of surface area compared to mass.
- They have thrusters which can actively bring the craft out of orbit
- They have reaction wheels which can orient the satellite to present the maximum surface area
- They are initially flown to orbit at an even lower altitude, requiring the thrusters bring them up to the operational altitude
With the active measures enabled, the satellites can be disposed of in months. With partial measures, some small number of years. And even with a completely dead and unresponsive satellite, they are estimating 5 years.
Note that 5 years is the new target for the FCC (yet to be fully enacted):
The previous rule was a 25-year life. I think the new rule is the right thing to do, and also that SpaceX should be commended to building to that new standard even before it was a requirement.
Anyway, feel free to ask further questions.