Editor's note: This is the second of three feature articles Ars is publishing to explore the financial, technical, and competitive dimensions of orbital data centers. Although the idea of putting data centers into space has long been discussed on a theoretical basis, the technology has rapidly become a red-hot topic. This series attempts to ground-truth some of the rhetoric flying around.
In this article, we discuss the technical challenges of building an orbital data center constellation: launching all of it, dissipating heat in space, dealing with radiation, and addressing latency issues in orbit. Read part one here.
SpaceX has pinned the bulk of its future value on orbital data centers. Not rockets. Not spacecraft.
Instead, it envisions launching and maintaining a constellation of 1 million satellites capable of generating 120 GW to power tens of millions—and potentially up to 100 million—frontier-class GPUs for data center services.
The company’s founder, Elon Musk, revealed plans for this massive constellation months ago, but until recently, the scope of the individual satellites was largely unknown. That changed in June, when Musk and Ian Dahl, director of satellite engineering for SpaceX, spoke in a promotional video about the company’s plans to develop the first iteration of an orbital data center, called an AI1 satellite. The video finally provided the company’s numbers about the satellite’s size and power capabilities.
“There’s not some magic that’s necessary that doesn’t exist,” Musk said during the video, reflecting on the challenge of building AI1 satellites. “A lot of this is technology we’ve already made for Starlink V3 satellites. Basically, we don’t think this is a super hard problem.”
As Ars wrote in part 1 of this series, the physics of orbital data centers are indeed non-magical. But the economics are, to put it mildly, challenging.
This subject has sparked a broad debate about the near-term viability of this technology, both in terms of feasibility and whether it’s all hype now that SpaceX is a publicly traded company.
Iridium Communications chief executive Matt Desch, a long-time, level-headed satellite industry executive, was asked during an earnings call earlier this year what he thought about the concept.
“It’s a hot, hot area right now of discussion, mainly because of Starlink’s announcement and some others,” Desch replied. “It looks like a problem that can be solved in space… (But) there’s massive technical challenges to overcome.”
Desch speculated that the recent enthusiasm for orbital data centers is not driven by a profound need to put them into space but by pecuniary reasons.
“It’s a really, really long-term opportunity at best, and I wonder if all the discussion isn’t for other reasons than maybe just solving an immediate problem,” he said. “I could jump on that bandwagon to try to, you know, hitch our wagon to that for a valuation. But we’re a really pragmatic company that focuses on really delivering results in cash and growth, so I’d rather kind of stick to the themes that I’m currently around.”
So who is right? With part 2 of this series, we want to see if we can put some rough numbers on the true viability of orbital data centers in general and SpaceX’s concept in particular.
The short answer is that a lot has to go right.
A chief reason to put orbital data centers in space is the free, limitless power from the Sun. Based on the schematic SpaceX released, each of its AI1 satellites would have solar panels encompassing about 600 square meters, or about 1.5 times the size of a basketball court. These solar panels would generate 150 kW of peak power and 120 kW of average power for computing.
The weight of these solar panels adds up quickly—we’re looking at probably 1 to 2 metric tons. Satellite industry consultant Stuart Taylor told Ars that SpaceX might consider using a newer material called perovskite (there are some Internet rumors about this) instead of silicon, which could enable much lighter solar panels. But questions remain about the long-term stability of perovskites, so we’ll base our analysis on standard silicon solar cells.
The satellites’ on-board computing power will generate significant heat, requiring a large radiator (more on this below). Estimates from various sources put this at around another 1 to 2 metric tons at a minimum. Adding everything else in, such as a bus (backbone), GPUs, and other components, the satellites will likely weigh between 3.5 and 7.5 metric tons.
To get all of this mass into orbit, you need a super heavy lift rocket. SpaceX’s Starship V3 rocket is estimated to have a payload capacity of 100 metric tons to low-Earth orbit, but the company’s engineers are already planning a V4 with a significantly higher capacity: 200 metric tons.
A final variable to consider is launch costs. The platonic ideal for Starship is full reusability, with both the first and second stages returning to the launch site and being re-stacked for launch within hours. The only costs would be propellant (perhaps $1.5 million per launch for liquid oxygen, methane, and other consumables) and personnel to manufacture and maintain the rockets and ground support equipment. For the sake of argument, let’s assume an idealized Starship launch cost of $20 million, which would translate to a truly remarkable $100 per kg to low-Earth orbit. That’s not unattainable if things go well for Starship, but it would take time.
So those are the basic numbers. For the purposes of this analysis, we will consider three cases: optimistic, neutral, and pessimistic.
SpaceX likely plans for each satellite to last five to seven years before being moved into a heliocentric disposal orbit or burning up in Earth’s atmosphere. Assuming a five-year lifetime, putting the 1-million satellite constellation into orbit and then replenishing it over time would require thousands of launches per year.
How many depends on your assumptions in each case above:
Even in the best-case scenario, that’s 10 launches a day. Worst case is 42 launches a day.
Clearly, that’s a lot. Last year, the world set a new record for orbital launch attempts: 329, with 321 reaching at least a marginal orbit, according to astrophysicist Jonathan McDowell. Of these, more than half—170—were conducted by SpaceX.
So for SpaceX, this data center megaconstellation would represent at least a 20-fold increase in its launch capacity. SpaceX currently has one Starship launch pad at its Starbase facility in Texas, and within a couple of years, it should have a total of four launch towers at sites in Texas and Florida. Those launch pads are optimized for equatorial orbits, so SpaceX may need launch sites for missions to Sun-synchronous orbits. It is considering sites in Louisiana and elsewhere to launch due south.
How much would the satellites cost? The analytics firm Quilty Space has estimated that Starlink V3 satellites—the template upon which the orbital data centers will be based—will cost around $1 million. Even if we allow for some economies of scale in building so many new satellites, an estimate of $1 million per spacecraft seems like a reasonable best-case scenario given that orbital data centers will have significantly larger solar panels and expensive computer hardware.
Finally, there are the ground systems to handle all the data moving to and from orbit all across the globe. Let’s estimate that at roughly $100 billion for all three scenarios.
This leads to our all-in, cocktail-napkin estimates for the cost of a 1-million satellite SpaceX orbital data center constellation:
