04 · Coverage
Drag
400 km is not vacuum. Lifetime is exponential with altitude and sulks when the Sun is angry. Low LEO is self-cleaning. High LEO is a storage unit.
In English
There is still air. It is thin, and it puffs up when the Sun is loud. Lifetime grows fast as you climb. Below ~500 km, dead hardware comes home. Above ~1_000 km, it does not.
- Try this
- 400 km vs 1 200 km. Toggle solar max. Read the cartoon lifetime.
- Keep this
- Low LEO is self-cleaning. High LEO stores junk.
Lab · the air is still there
400 km is not vacuum. It is a thin thermosphere that swells when the Sun is angry. Lifetime is exponential with altitude. Starlink stations-keep. Dead sats at 550 km come home in years. Dead sats at 1_200 km do not.
Altitude 550 km
Cartoon lifetime 2.1 years
Ballistic coefficient m/(Cd A) and atmospheric density (which follows F10.7 and Ap) set decay. The exponential cartoon matches orders of magnitude, not a particular NORAD object.
Station-keeping on Starlink is a tiny ion or Hall burn against drag. Fail that, and 550 km is a multi-year reentry, not a graveyard.