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Comment by XorNot | Hacker News Reader

The real issue is that the power situation in LEO is still actually terrible! Your solar is a little more performant, but you're plunged into hard shade every 45 minutes.

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There exist the so-called Sun-synchronous orbits, which exploit the precession effect caused by the fact that the Earth is not a sphere, to pass over the same point of the Earth at the same local hour. On a small subset of these Sun-synchronous orbits the Sun is always visible from the satellite (i.e. on the subset of orbits whose plane is approximately perpendicular on the radius that connects the Sun to the Earth). Without the precession effect, a satellite that sees the Sun for an entire day would lose this property after a few days, because of the rotation of the Earth around the Sun, which alters the direction in space of the radius from the Sun to the Earth.

However, the number of slots that are available in Sun-synchronous orbits with permanent view of the Sun is limited, and many potential users want them. So those who desire to build datacenters would have to compete for such orbital slots. There are much less such slots than for geosynchronous orbits. Other countries would certainly be outraged if USA occupied all the available slots with datacenters.

Improved control of the satellites for collision avoidance could allow smaller slots, but maneuvering heavy datacenters would require a lot of fuel, so they might require periodic refueling, greatly increasing the costs.

I think calling solar a little more performant is underselling it. Once you have LEO getting to a better orbit costs relatively little. Getting from LEO to the moon is only like 30% more than getting from ground to LEO.

True, but lifting the fuel to power that “small” orbital boost is unintuitively expensive

(Refer to the tyranny of the “Rocket Equation”)

They are mostly planning sun synchronous orbits afaik. That means the orbit is tilted so the earth’s deformed shape continually moves the orbital plane so the satellite is always in the sun (or generally the plane has the same angle to the sun).

Sure: which is a higher and less accessible orbit. The relative fuel cost might be small, but in absolute terms the ship carrying payload is carrying a lot more to do it - see the number of Starships to refuel a Starship in LEO.

And here's the thing: all of this is competing with solar+batteries cost on Earth. The power situation is the only advantage here.

Like why not put a datacenter on a barge and run an HVDC line out to it far offshore? That would be expensive...but more expensive then space? It's not even outside of the capability set of SpaceX, who already run drone ships to facilitate Falcon 9 landings.

> Sure: which is a higher and less accessible orbit. The relative fuel cost might be small, but in absolute terms the ship carrying payload is carrying a lot more to do it - see the number of Starships to refuel a Starship in LEO.

No it’s not, it’s not either SSO or LEO. You can have SSO at 600km which is lower than the normal LEO satellite.

I agree that it doesn’t make a lot of sense (look at the root comment of this thread), but you absolutely can make a LEO datacenter with 100% sun coverage if you want to.

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