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No night? Where are you putting these satellites? The only orbit that doesn't eclipse is sun synchronous, an already crowded orbit. Even GEO satellites experien

No night? Where are you putting these satellites? The only orbit that doesn't eclipse is sun synchronous, an already crowded orbit. Even GEO satellites experience eclipse.

etskinner 3y ago
They address this in the article: Only twice per year are the panels in shadow, at the equinoxes. Presumably all the rest of the time they're slightly above/below the earth with respect to its orbit. It's the same reason the moon is lit nearly all the time.
- mlyle 3y ago
  > It's the same reason the moon is lit nearly all the time. The moon is 10x further away, so the Earth subtends/shades a much smaller angle.
  - DennisP 3y ago
    A geostationary satellite gets eclipsed more than the moon but it's still in full sun 99.5% of the time.
mecko23 3y ago
Respectfully, I believe you are inaccurate on both accounts, sun synchronous orbits (SSO) only have no eclipse if their orbital plane is within a very degrees of the terminator, this of course widens with altitude but there exists far more possible SSOs with eclipses than without. Secondly with GEOs as with any very high altitude orbit the eclipse time trends towards zero so effectively at a GEO the eclipse time is minimal compared to the illuminated time. Of note the length for the eclipse time of GEO varies throughout the year.
- spacemark 3y ago
  Respectfully, you are not correct that eclipse in Geo is insignificant. It drives many engineering constraints for spacecraft systems. Look I get why people are excited about space space solar power, but I've been in this industry for 15 years and when you dig into the numbers and understand the realities of spacecraft engineering, SBSP just seems like a fool's errand. It may not always be that way, but the technical challenges are extreme and costs are still nowhere near what would be required to make it work. You can chalk my comments up to a grumpy engineer tired of the cyclical SBSP pushes that never go anywhere.
  - mecko23 3y ago
    Hmm, well I totally understand how it drives spacecraft design and I don’t know off the top of my head the length of greatest eclipse but it cannot be greater than a small fraction of the period (upwards of 1/12). This is significant for a spacecraft itself but as far as a regionally integrated power grid is concerned it is a clear improvement over current solar PV systems. I get that there maybe some fatigue here with the idea and blue sky optimism that comes with SBSP, I think there are valid criticisms to level at it orbit selection and corresponding ground tracks and eclipses are not one.
  - mlyle 3y ago
    > It drives many engineering constraints for spacecraft systems. Here the only thing it's going to drive are thermal requirements-- which are admittedly significant problems. There's no need to continue to use large amounts of power for comms, etc, like on most GEO birds. And, of course, the grid needs to deal with the power disappearing for an hour in the middle of the night for short periods of the year.
    - spacemark 3y ago
      It drives electrical and battery system requirements more than anything else. Thermal effects impact pointing/ADCS, which impacts propulsion, etc.
      - mlyle 3y ago
c54 3y ago
> Glaser had noticed that a satellite in geosynchronous Earth orbit (GEO), 35,786 kilometers above the equator, would pass through Earth's shadow for only a few minutes each year. The article addresses this. To my mind 4 minutes per year is equivalent to the parent’s layspeak “no night” comment.
- cfraenkel 3y ago
  4 minutes??? Not even close. Each eclipse varies from a few seconds for the first one to practically an hour in the middle, then gets shorter again, over roughly 30 eclipses each season (2 per year)
mlyle 3y ago
So, let's cut down the pedantry a bit. Even in the most pessimal reasonable orbits, up to an hour of outage in the middle of the night for 3-4 months per year is a very different beast from getting just several hours of sun per day. Why? - You still get better duty cycle from the panels - The time the power is missing is very small - The need for storage, etc, is low because it's a short period of relatively low demand that is missing.

No night? Where are you putting these satellites? The only orbit that doesn't eclipse is sun synchronous, an already crowded orbit. Even GEO satellites experience eclipse.

etskinner 3y ago

They address this in the article: Only twice per year are the panels in shadow, at the equinoxes. Presumably all the rest of the time they're slightly above/below the earth with respect to its orbit. It's the same reason the moon is lit nearly all the time.

mlyle 3y ago
> It's the same reason the moon is lit nearly all the time. The moon is 10x further away, so the Earth subtends/shades a much smaller angle.
- DennisP 3y ago
  A geostationary satellite gets eclipsed more than the moon but it's still in full sun 99.5% of the time.

mecko23 3y ago

Respectfully, I believe you are inaccurate on both accounts, sun synchronous orbits (SSO) only have no eclipse if their orbital plane is within a very degrees of the terminator, this of course widens with altitude but there exists far more possible SSOs with eclipses than without. Secondly with GEOs as with any very high altitude orbit the eclipse time trends towards zero so effectively at a GEO the eclipse time is minimal compared to the illuminated time. Of note the length for the eclipse time of GEO varies throughout the year.

spacemark 3y ago
Respectfully, you are not correct that eclipse in Geo is insignificant. It drives many engineering constraints for spacecraft systems. Look I get why people are excited about space space solar power, but I've been in this industry for 15 years and when you dig into the numbers and understand the realities of spacecraft engineering, SBSP just seems like a fool's errand. It may not always be that way, but the technical challenges are extreme and costs are still nowhere near what would be required to make it work. You can chalk my comments up to a grumpy engineer tired of the cyclical SBSP pushes that never go anywhere.
- mecko23 3y ago
  Hmm, well I totally understand how it drives spacecraft design and I don’t know off the top of my head the length of greatest eclipse but it cannot be greater than a small fraction of the period (upwards of 1/12). This is significant for a spacecraft itself but as far as a regionally integrated power grid is concerned it is a clear improvement over current solar PV systems. I get that there maybe some fatigue here with the idea and blue sky optimism that comes with SBSP, I think there are valid criticisms to level at it orbit selection and corresponding ground tracks and eclipses are not one.
- mlyle 3y ago
  > It drives many engineering constraints for spacecraft systems. Here the only thing it's going to drive are thermal requirements-- which are admittedly significant problems. There's no need to continue to use large amounts of power for comms, etc, like on most GEO birds. And, of course, the grid needs to deal with the power disappearing for an hour in the middle of the night for short periods of the year.
  - spacemark 3y ago
    It drives electrical and battery system requirements more than anything else. Thermal effects impact pointing/ADCS, which impacts propulsion, etc.
    - mlyle 3y ago

c54 3y ago

> Glaser had noticed that a satellite in geosynchronous Earth orbit (GEO), 35,786 kilometers above the equator, would pass through Earth's shadow for only a few minutes each year. The article addresses this. To my mind 4 minutes per year is equivalent to the parent’s layspeak “no night” comment.

cfraenkel 3y ago
4 minutes??? Not even close. Each eclipse varies from a few seconds for the first one to practically an hour in the middle, then gets shorter again, over roughly 30 eclipses each season (2 per year)

mlyle 3y ago

So, let's cut down the pedantry a bit. Even in the most pessimal reasonable orbits, up to an hour of outage in the middle of the night for 3-4 months per year is a very different beast from getting just several hours of sun per day. Why? - You still get better duty cycle from the panels - The time the power is missing is very small - The need for storage, etc, is low because it's a short period of relatively low demand that is missing.