Essentially, the atmosphere contracted due to the solar minimum and they want to make sure inoperative satellites decay within months rather than years. Ballistic decay is a safety mechanism in case their satellites break down. Also they will use less fuel for avoiding the crowded 550km band.
"As solar mininum approaches, atmospheric density decreases, which means the ballistic decay time at any given altitude increases — lowering will mean a >80% reduction in ballistic decay time in solar minimum, or 4+ years reduced to a few months," Nicolls wrote in his X post. "Correspondingly, the number of debris objects and planned satellite constellations is significantly lower below 500 km, reducing the aggregate likelihood of collision."
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Won't this make running Starlink more expensive?
Lower orbits > Increased atmospheric drag > More fuel expended to maintain orbit > Heavier sats due to more fuel > Increased launch cost per unit
Or even: Lower orbits > Increased atmospheric drag > Quicker orbit decay > Shorter lifespan of sats > More frequent launches
Forgive my Kerbal-based space knowledge here.
Essentially, the atmosphere contracted due to the solar minimum and they want to make sure inoperative satellites decay within months rather than years. Ballistic decay is a safety mechanism in case their satellites break down. Also they will use less fuel for avoiding the crowded 550km band.