At the start of the month, Elon Musk announced that two of his companies — SpaceX and xAI — were merging, and would jointly launch a constellation of 1 million satellites to operate as orbital data centers. Musk's reputation might suggest otherwise, but according to experts, such a plan isn't a complete fantasy. However, if executed at the scale suggested, some of them believe it would have devastating effects on the environment and the sustainability of low Earth Earth orbit.
Musk and others argue that putting data centers in space is practical given how much more efficient solar panels are away from Earth's atmosphere. In space, there are no clouds or weather events to obscure the sun, and in the correct orbit, solar panels can collect sunlight through much of the day. In combination with declining rocket launch costs and the price of powering AI data centers on Earth, Musk has said that within three years space will be the cheapest way to generate AI compute power.
Ahead of the billionaire's announcement, SpaceX filed an eight-page application with the Federal Communications Commission detailing his plan. The company hopes to deposit the satellites in this massive cluster in altitudes ranging between 500km and 2000km. They would communicate with one another and SpaceX's Starlink constellation using laser "optical links." Those Starlink satellites would then transmit inference requests to and from Earth. To power the entire effort, SpaceX has proposed putting the new constellation in sun-synchronous orbit, meaning the spacecraft would fly along the dividing line that separates the day and night sides of the planet.
What a data center would endure in orbit
Almost immediately the plan was greeted with skepticism. How would SpaceX, for instance, cool millions of GPUs in space? At first glance, that might seem like a weird point to get hung up on — much of space being around -450 Fahrenheit — but the reality is more complicated. In the near vacuum of space, the only way to dissipate heat is to slowly radiate it out, and in direct sunlight, objects can easily overheat. As one commenter on Hacker News succinctly put it, "a satellite is, if nothing else, a fantastic thermos."
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Scott Manley, who, before he created one of the most popular space-focused channels on YouTube, was a software engineer and studied computational physics and astronomy, argues SpaceX has already solved that problem at a smaller scale with Starlink. He points to the company's latest V3 model, which has about 30 square meters of solar panels. "They have a bunch of electronics in the middle, which are taking that power and doing stuff with it. Now, some of that power is being beamed away as radio waves, but there's a lot of thermal power that's being generated and then having to be dissipated. So they already have a platform that's running electronics off of power, and so it's not a massive leap to turn into something doing compute."
Kevin Hicks, a former NASA systems engineer who worked on the Curiosity rover mission, is more skeptical. "Satellites with the primary goal of processing large amounts of compute requests would generate more heat than pretty much any other type of satellite," he said. "Cooling them is another aspect of the design which is theoretically possible but would require a ton of extra work and complexity, and I have doubts about the durability of such a cooling system."
What about radiation then? There's a reason NASA relies on ancient hardware like the PowerPC 750 CPU found inside the Perseverance rover: Older chips feature larger transistors, making them more resilient to bit flips — errors in processing caused most often by cosmic radiation — that might scramble a computation. "Binary ones and zeroes are about the presence or absence of electrons, and the amount of charge required to represent a 'one' goes down as the transistors get smaller and smaller," explains Benjamin Lee, professor of computer and information science at the University of Pennsylvania. Space is full of energized particles traveling at incredible velocities, and the latest GPUs are built on the smallest, most advanced processing nodes to create transistor-dense silicon. Not a great combination.
"My concern about radiation is that we don't know how many bit flips will occur when you deploy the most advanced chips and hundreds of gigabytes of memory up there," said Professor Lee, pointing to preliminary research by Google on the subject. As part of Project Suncatcher, its own effort to explore the viability of space-based data centers, the company put one of its Trillium TPUs in front of a proton beam to bombard it with radiation. It found the silicon was "surprisingly radiation-hard for space applications."
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