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Comment by echoangle | Hacker News Reader

I still don’t see what the advantage is. Of course it’s physically possible to build a datacenter in space, but I can’t imagine land prices being that high that the same data center on earth wouldn’t be cheaper. Even just due to launch costs and the more sophisticated equipment needed for space.

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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.

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”)

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.

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.

I doubt it'll make sense any time soon, but some arguments I can think of are that solar in space can easily be ~50% more efficient at any moment while also being continuous (enough) in the right orbit.

An even more radical idea is to put nuclear in space which would sidestep all the earthly hurdles (beyond the launch).

Right, but even if you get 100% solar time in orbit and maybe 20% on the ground, I still don’t see it. Just from a procurement cost and maintenance standpoint. I think spreading a few datacenters around the world to have quasi continuous availability is easier than launching them on satellites.

> An even more radical idea is to put nuclear in space which would sidestep all the earthly hurdles (beyond the launch).

That makes even less sense to me. Why would you launch then and not just stay on the ground? Do you think a country would allow you to launch a rocket with a nuclear reactor from their land but the reactor is so unsafe that you’re not allowed to operate it on the ground?

Then I would just say put it on a boat and park it in international waters, that’s surely cheaper than orbit, right?

Nuclear is used in space, but my understanding is that it is too low power and not really scalable to computing needs for this use case. Bonus side really is that nuclear power can provide power for very long time.

Until now only energy sources based on radioactive decay have been used in space, which have very low power, but they can provide it for many decades.

Nuclear fission reactors, similar to those used on submarines or ships, would enable very different applications.

Until now, they have not been used for fear of what would happen after a failed rocket launch, when the reactor would fall back on Earth.

This could be mitigated by sending only components of the reactor and assembling it in space.

I do not think that routine exploration of the Solar System beyond Mars will ever be possible without using at least nuclear fission reactors, because it is too slow with chemical sources of energy.

Actually in the Cold War there were some actual nuclear reactors in space:

https://en.wikipedia.org/wiki/TOPAZ_nuclear_reactor#TOPAZ-I

> This could be mitigated by sending only components of the reactor and assembling it in space.

How would that help? The main problem if the launch fails is that the radioactive material will spread around (in the worst case, they are encased so exactly that doesn’t happen).

You could maybe spread out the nuclear material in multiple launches but you would just increase the risk of a small contamination in exchange for a smaller risk of a large contamination.

I don’t think the individual parts of the reactor are intrinsically safer than the reactor, it’s not like it’s going to become an atomic explosion during launch.

One advantage that does come to mind in light of the Iran war (and the loss of an AWS DC) is difficulty in attacking it, even when it’s directly above foreign territory. I wonder if one of the intended customers will be gov/military? Conjoined spy satellite/DC for some function maybe?

I don’t know what the end game of the US looks like but surely you’ll always find some territory around the world to relatively safely put datacenters? And if your opponent isn’t Iran but something like russia or china, they’ll just blow up your datacenter in orbit, too.

I see the point to maybe do some onboard data processing on spy satellites etc, but on the other hand, downlink bandwidth seems to be become less of an issue over time, so it doesn’t seem that important to me compared to just sending down the raw data over star link or the military equivalent.

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