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Low orbit sats spend far less than half the day in darkness; it is only when they are in the penumbra of the earth that they are in darkness. What makes space-b
by evgen 6y ago
Low orbit sats spend far less than half the day in darkness; it is only when they are in the penumbra of the earth that they are in darkness. What makes space-based power interesting is that such sats have a line to sunlight (and therefore power) when a portion of the planet below them does not, enabling them to provide power for a period of time after sunset and also before sunrise.
- deleted 6y ago[deleted]
- adwn 6y ago> Low orbit sats spend far less than half the day in darkness; it is only when they are in the penumbra of the earth that they are in darkness. Yes, and over 24 hours, they are 12 hours in darkness: on a 90-minute orbit, 45 consecutive minutes are spent in Earth's shadow => half the day, they are in darkness. On the upside, they get full insolation during those 12 hours, unlike ground-based solar. On the downside, at night, the satellite will be in Earth's shadow whenever it's above the ground station, so LEO solar power satellites can't supply power at night (unless they carry batteries).
- nfg 6y ago> Yes, and over 24 hours, they are 12 hours in darkness: on a 90-minute orbit, 45 consecutive minutes are spent in Earth's shadow => half the day, they are in darkness. FWIW I don’t think that’s correct. The effect isn’t significant in really low orbits but going by my hasty maths even at the ISS’ orbit of 350km a satellite spends - at worst - about 10 hours a day in darkness. I say at worst because the plane of the orbit also has an effect here. I make it that you can roughly calculate it as: 24 * ((asin (EarthRadius/OrbitRadius) *2) / (2 pi radians)).