[Starlink] Re: Data centers are racing to space — and regulation can’t keep up

[Ulrich Speidel <u.speidel@auckland.ac.nz>]

On 27/02/2026 2:56 am, Nitinder Mohan via Starlink wrote:
>    1.
> The downlink bottleneck is the real motivation for space computing, not replacing ground data centers.

Now how bad is that bottleneck really when you're operating a large 
constellation, in which each satellite can downlink?

Currently, there is a significant bottleneck in terms of downlinking to 
end users with Dishys. Why?

1) You only really have the Ku band. Lower down is crowded, further up 
there's a problem with the atmosphere between your sats and the Dishy.
2) You have the need to keep end user devices cheap (read: small), which 
limits gain and phased array directionality and selectivity.

But when we're talking data centers, we're not talking downlinking to 
end users with Dishys. We're talking downlinking to other 
infrastructure. Unlike an end user, where there's no choice in terms of 
geographical location to downlink to, infrastructure is already 
geographically diverse. SpaceX have gateways all over the place in Ka 
and higher bands, so in principle they can downlink to wherever the 
weather is in their favour - which likely it is pretty much all the time 
somewhere in their empire. ISLs help the data get there.

If we go beyond classic TCP and use, say, linear network coding for 
delivery via multiple downlink paths, then this could even look elegant.

So the only issue that then remains in this respect is latency / jitter.

>   2.
> Orbital data centers serving Earth-based users face fundamental physics constraints, exactly as this thread has identified. Heat dissipation is the hardest problem. Satellites can only radiate heat, and available radiator surface area is strictly limited. Unlike ground facilities with active cooling, there is a hard thermodynamic ceiling on how much computation any individual satellite can sustain. The seminar reached strong consensus that the "data center in space" concept for general Earth-centric workloads is not validated, and the sustainability math does not currently work out.
Now that assumes conventional computation. The reason why we get all 
that heat in our computers is because their logic gates spend a lot of 
their time in no-man's land between 0 and 1 bits: 0 bits might be 
"switch open", i.e., voltage but no current, which means no power being 
dissipated, while 1 bits might mean "switch closed", with current but no 
voltage, so also no power being dissipated. But *while* they're 
switching, there's both current and voltage, and hence power being 
dissipated to the gates' environment.

Compute in ways that either reduce the time spent switching or that use 
less power (e.g., adiabatic logic) and this becomes less of an issue.

A lot of the other issues persist, though.

-- 
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Dr. Ulrich Speidel

School of Computer Science

Room 303S.594 (City Campus)

The University of Auckland
u.speidel@auckland.ac.nz
http://www.cs.auckland.ac.nz/~ulrich/
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