SpaceX's Orbiting AI Data Centers

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In a Monday video: https://x.com/SpaceX/status/2064099405758906727 SpaceX CEO Elon Musk revealed more about his plans to operate a giant fleet of orbiting data centers around Earth. The presentation included “draft” technical details about version 1 of the “AI satellite,” which appears to have shrunk in size from an estimated 170 meters in the initial rendering to 70 meters (230 feet), roughly the size of a Boeing 747.

The company also revealed how it plans to cool the AI satellite, which will be designed to harness the Sun’s energy to continuously power enterprise-grade GPUs, generating heat. SpaceX’s slide shows each satellite will feature a “deployable liquid radiator” system measuring 110 square meters (1,184 square feet).

In the video, Musk says version 1 of the AI satellite is using Nvidia’s latest Rubin GPU chips as a reference design. In addition, he suggested that the initial satellite will carry the equivalent of a GB300 server “rack,” which contains 72 GPUs.

The cooling system will feature “redundant pumping loops,” presumably to keep the liquid flowing. The video didn’t explicitly say what kind of liquid SpaceX plans to use, but Hugh Lewis, a space debris expert and professor of astronautics at the University of Birmingham, doesn't expect water.

“The freezing point and boiling point of water are not ideal for an unpressurized system operating in a vacuum and subject to potentially high and low temperatures,” he tells in an email. Instead, he expects the satellite cooling system to use ammonia, similar to the International Space Station (ISS). “Ammonia remains as a liquid down to low temperatures."

Since space is a vacuum, heat can't travel through the air or by direct contact as it does on Earth. To keep its systems cool, the ISS uses both a water-cooling system in the interior for the pressurized oxygen environment and an ammonia-based cooling system outside the station.

“The heated ammonia circulates through large radiators located on the exterior of the Space Station, releasing the heat by radiation to space that cools the ammonia as it flows through the radiators,” a NASA document says: https://www.nasa.gov/wp-content/uploads/2021/02/473486main_iss_atcs_overview.pdf. The closed-loop system can thus collect the heat, transport it, and then dissipate it through “cold plates and heat exchangers, both of which are cooled by circulating ammonia loops on the outside of the station.”

So, it’s possible SpaceX’s AI satellites will take a similar approach, with the radiators pointing away from the Earth and Sun. In the video, Musk also framed his orbital data center project as achievable, even though the concept remains unproven and faces doubts.

“There's not some magic that's necessary that doesn't exist for the Al satellites,” he said. “A lot of this is technology we've already made for the Starlink V3 satellites,” which the company plans on launching later this year.

“The AI satellite is much simpler than a Starlink satellite,” he added. “A Starlink satellite has gigantic phased array antennas, it’s got parabolic antennas, it’s got a lot of laser links, it’s much more complicated than an AI satellite.”

However, Lewis isn’t so sure about that. “Most satellites do not use active thermal control because of the high mass and power requirements—exceptions are for human spaceflight,” he said. “These systems add complexity and important points of failure. Hence, SpaceX has referred to a redundant fluid loop (which is even more mass!) Still, I would expect a relatively high failure rate on these compared with the Starlink satellites, because of the added mechanical complexity.”

The other issue is that ammonia is toxic, and a “pollutant,” Lewis said, meaning it could be harmful to retire the AI satellites by de-orbiting them and letting them burn up in the atmosphere. SpaceX has plans to launch up to 1 million AI satellites. But the company recently told the FCC it wants to retire 80% of the constellation by placing the satellites in graveyard orbits around Earth or, perhaps, the Sun. It's possible that those AI satellites might struggle to disintegrate in the atmosphere, given the large GPUs they'd be carrying. Hence, the orbiting data centers could create significant space junk since each satellite is designed to operate for only five years, according to an FCC filing.

SpaceX's plan to deploy the orbiting data centers is already facing opposition from astronomers, environmentalists, and concerned citizens. However, the company has signaled it’ll start small with the AI satellite plan as FCC approval remains pending.

"We don't think this is a super hard problem compared to what we already do," Musk says in the video. "It's not like space is going to get crowded. Space is enormous."

In addition, the company has argued that orbiting satellites are a better solution than Earth-based data centers, which have already raised concerns about their environmental toll and strain on the electric grid. SpaceX plans on deploying the first data center satellites "as early as 2028."