Abstract
Starcloud have claimed that a single 100-ton Starship launch could suffice to create a 40 MW space data centre (SDC) for $8.2 M. My analysis finds that this is infeasible in a single launch but requires a total of upto 22 launches. The SDC’s solar arrays require 4 launches determined by examining existing solar arrays on the ISS. Similarly, the ISS’s radiator benchmarks indicate that 13 launches would be needed for the SDC’s thermal management system. The server racks would require an addition 5 launches. I have not analysed the effects of MMOD/radiation shielding and the impact of propellant use for in-orbit assembly on launch numbers—this requires specifications and mission architectures that have not been made public and might not yet be fully developed. On the note of launch costs, the whitepaper’s (miscalculated) assumed launch cost is $30/kg. This makes their comparative economic analysis to terrestrial data centres unmoored from reality in the near term. Some experts speculate that $1000/kg would be an optimistic launch cost, which means $100M per launch and a total cost of $103.2M In 2021 dollars, a Falcon-9 launch costs $2600/kg and a Falcon Heavy’s at $1500/kg. So, even $500/kg is also a fairly optimistic estimate. . So, even if costs drop to $500/kg, a single launch results in an overall cost of $53.2M, not the purported $8.2M. If a second launch is needed, then the worst case number is $200M making it more than their reported cost of running a terrestrial data center (TDC).
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Introduction
On Earth, data centres run on the existing electricity grid that, crudely put, use a combination of fossil fuels or terrestrial solar. Recently, technologists and entrepreneurs have talked up placing data centres in space to resolve three issues with terrestrial data centres (TDC):
Data centres require tremendous amounts of energy, which is plentiful and “free” in space. There, 24/7 solar power is unhindered by day/night cycles, weather, and atmospheric losses (attenuation). A lot of waste heat is generated running TDCs, which contributes to climate change—so migrating to space would alleviate the toll on Earth’s thermal budget. This seems like a compelling environmental argument. TDCs already consume about 1-1.5% of global electricity and it’s safe to assume that this will only grow in the pursuit of AGI. Real estate for data centres is a massive bottleneck and this land could be used for other purposes.
Now, Sam Altman has also talked up nuclear energy as a solution, which I suspect is maybe a more desirable solution from an energy and climate angle but the regulatory barriers need to be resolved. So, space, in theory, sounds like a speedier answer from a regulatory perspective—as a space person, I’d love nothing more than for there to be a strong economic case for space. But delivering a GW-scale SDC requires engineering solar arrays in the km scale, which will not be easy. Even the 40 MW system, that Starcloud used to benchmark against TDCs, needs a square of side 357 m. This would far exceed the span of the largest space structure ever built—the ISS is about 100 m in its longest dimension.
So, there’s now at least one YCombinator-backed company, Starcloud Inc., working on building SDCs—they released a whitepaper on this and I decided to dive in (with Claude to speedrun my analysis, of course). They begin by pointing us to some of the unique benefits of space solar, the main one being its 95%+ capacity factor versus just a median capacity factor of 24% for US terrestrial solar (under 10% in northern Europe). They continue to say that combined with 40% higher peak power due to no atmospheric losses, you get over 5x the energy output from the same solar array. This is not exactly my forte so I am not fact-checking these claims—let’s accept them as true.
My qualifications
If I can claim a bit of domain expertise, it’s on the space side. Reading Starcloud’s whitepaper, I felt I could use my limited expertise from designing mission for in-space assembled large space telescopes and analysing them to understand their techno-economic analysis.
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