by godelski | 2025-05-14 00:17:36+00:00
How did this get funding?

Seriously! There is just so much wrong and some of is trivial.

> radiating primarily towards deep space, which has an average temperature of about 2.7 Kelvin or -270°C.

Are they suggesting putting these things in deep space? I guess for training you can handle hours of delay time but still it is really bandwidth limited. But they say they're using solar, so I assume they ARE NOT operating in deep space but rather near Earth or maybe even on the Moon.

In these locations you have to deal with cooling AND heating. On the moon you swing from -130C (LRO got down to -250C) on the dark side and 121C on the light side. The ISS swings from -160C to 120C. These are too cold for most electronics. Not to mention that these temperature swings create a lot of physical stress on parts, and we're talking about putting up up some of the smallest objects we commercially make? They will rip right off the circuit-board if you don't get it right.

Not to mention that radiating into space is quite difficult. There's a reason we use convection ovens and why we put fans in our computers. It isn't about the temperature of the atmosphere nor the thermal efficiency, it is because convection is just a hell of a lot more efficient. Thermal radiation is like shedding your heat via a lightbulb.

Their claim here is that they can radiate 633W/m2. For supercomputers we're talking on the order of 10s of MW of waste heat. That's 10^7! These are going to be BY FAR the largest radiators in space and going to cost tons of money for the mass alone.

Not to mention the size of the solar panels they'll need... But at least they mention this one: "A 5 GW data center would require a solar array with dimensions of approximately 4 km by 4 km," These are GIGANTIC structures and far larger than anything we've put into space.

> The mass of radiation shielding scales linearly with the container surface area, whereas the compute per container scales with the volume. Therefore the mass of shielding needed per compute unit decreases linearly with container size.

This one really got me, because it can be sniffed out with high school physics.

Density (ρ) is mass (m) divided by volume (V): m = ρV. We'll assume a sphere due to its efficient surface area. You use Δr as the shell's thickness: V = 4/3(Δr)^3

Let: m = ρV Let: V = 4/3(Δr)^3 ∴ m ∝ ρ(Δr)^3

What is linear? What is decreasing?

> This effect, combined with the shielding afforded by the cooling blocks, means that radiation shielding is proportionally a much smaller concern compared to electronics on typical satellites today.

Now this might be partially accurate, but it does require some very specific conditions to be true. It is quite common for spacecraft to dual purpose their cooling systems to also act as part of their radiation shielding since essentially the most important part of shielding is mass[0]. But also most spacecraft aren't giant computers in space. You're going to need extremely uniform shielding and I doubt you can efficiently design the cooling system to also be uniform.

But also you have to remember that you can't shield your solar panels. To do so would prevent light from reaching them. That leads to a weird constraint here and I would not expect these machines to be meaningfully long lived. The alternative is you could go repair them, but that's expensive too.

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I think the idea is cool and worth exploring, but given the white paper I'm not sure why anyone gave them money. The idea itself is old and there has been a lot of work done in this space (pun intended). It just seems like it is riding the hype of space and AI. Exciting things, but that can make people naive. Maybe there's more than is shown in this whitepaper and I hope investors are doing more due diligence but there's definitely a lot of red flags here.

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https://www.nasa.gov/smallsat-institute/sst-soa/thermal-cont...

https://ocw.mit.edu/courses/16-851-satellite-engineering-fal...

https://www.jpl.nasa.gov/nmp/st8/tech/eaftc_tech1.php

https://www.nature.com/articles/s41597-024-03913-w

[0] I know this because I've research for NASA on radiation shields. I got multiple SBIR and STTR grants for this work. Material choices still do matter but the right material is proportional to the radiation level. But the higher the energy level, the less atomic properties matter and the more density does. You can get benefits from the electromagnetic properties of protons and electrons (beta-), but these don't help you with neutrons. That is, until after you slow these things down, which is why there is typically layering.