ChristianKl's Shortform

ChristianKl

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Elon Musk seems to have decided that going to Mars isn't that important anymore.

For those unaware, SpaceX has already shifted focus to building a self-growing city on the Moon, as we can potentially achieve that in less than 10 years, whereas Mars would take 20+ years.

[...]

That said, SpaceX will also strive to build a Mars city and begin doing so in about 5 to 7 years, but the overriding priority is securing the future of civilization and the Moon is faster.

This means not only won't they begin with Mars this transfer window but also not the next one. At the same time, the merger between SpaceX and xAI, seems like SpaceX now wants to refocus on data centers in "space".

Given the problems with getting rid of heat from space satellites might be solved with building the data center on the moon where everything is cold and the moon is a big heat sink.

Transporting data centers to the moon is even more expensive than transporting them to an Earth orbit. It is very hard to compete with the Earth surface in terms of data center cost. It seems hard to believe to me that moon data centers could be viable.

But I wonder how serious he is about his stated plans are anyway. Perhaps he mainly needs more cash for xAI (which owns X which is loaded with expensive debt from the inflated Twitter acquisition, also paying for Grok GPUs/DRAM is expensive), and SpaceX can provide money from its substantial Starlink revenue... (read more)

3ChristianKl9mo

For Elon motivating SpaceX employees is important, so he needs to tell the public a story about how SpaceX isn't just about building AI datacenters even if he thinks building superintelligence is the main goal of SpaceX and it's important to build AI datacenters for that and he can't build enough of them on earth. As far as the AI datacenters in orbit go, it's not clear to me that the thermodynamics work out for that project and it's easy enough to lose the heat that the datacenters produce.

2Garrett Baker9mo

In the interview he argues that the reason he wants to build a ton of solar panels to capture a bunch of the sun's energy is because of AI, he really comes across as extremely AI pilled, he is not downplaying his exciting singularity-inducing AI-related objectives in order to convince SpaceX employees to work on making solar panels from moon dust. [...] What thermodynamics are you concerned about? It is extremely efficient to radiate heat in space (a good thing too because that is your only option!). The equation here is the Stefam-Boltzmann law, which says P=εσAT4 where P is the power you radiate away, ε is your emissivity, σ is the Stefan-Boltzmann constant, A is your surface area, and T is your temperature. Note that that is T4, small changes in your temperature have large bang-for-your-buck in your radiation power. Intuitively, this should make things easy. I got Claude to run the numbers, and Claude found that the launch cost of the radiator would only add $3M, assuming $200/kg. Meanwhile AI "hyperscaling" datacenters cost around $100M to build, and (assuming solar panels are already up there) weigh 200 tons leading to a launch cost of $40M. That is to say, compared to the other costs involved, the radiator seems very minor. Claude's radiation analysis Alright, let's just do vanilla flat-panel radiators at elevated chip temps. Assumptions * Data center thermal load: P=10 MW (moderate — a hyperscaler pod is 20-50 MW, but let's start here) * Emissivity: ε=0.92 (anodized aluminum or similar high-ε coating) * Two-sided radiation (both faces of panel radiate to space) * Background sink temperature: Tsink≈3 K (negligible, so we ignore it) * Sun-shielded radiators (no solar absorption) Stefan-Boltzmann q=εσT4 where σ=5.67×10−8 W m−2K−4. Per side, per m²: Radiator Tempq (W/m²)Two-sided (W/m²)350 K (77°C)7831,566400 K (127°C)1,3362,671450 K (177°C)2,1394,278500 K (227°C)3,2616,522 Required Area for 10 MW A=P2εσT4 Radiator TempArea (m²)Equiv. sq