Four Google TPUs head to orbit to test whether AI chips can shed heat in a vacuum

Google's case for putting AI hardware in orbit is power. The company says satellites in low Earth orbit get near-constant sunlight and can generate up to eight times more solar power than on Earth ^[19]. SpaceX has a larger plan of the same kind. It aims to operate a million-member constellation of Starmind AI satellites and to start building it as soon as next year, according to Space.com ^[20]. This flight is the first time Google has sent its own AI chips into orbit ^[14].

Radiation already has a ground result behind it. At a proton-beam facility, Google ran AI workloads on Trillium TPUs while exposing them to radiation and monitoring errors. It says initial results showed the chips withstood a total dose greater than a five-year space mission would deliver ^[18]. The result is Google's own, from a lab. The coverage reports the dose outcome but no error counts from those runs. For a chip doing inference, how often a calculation comes back wrong is what an operator would ask about first.

The flight will not replace that test on dose. It is planned to last a year, according to The New York Times ^[2]. A year is a fifth of the five-year mission Google used as its benchmark ^[21]. The flight will record a year of radiation effects on chips actually running in orbit ^[3].

Cooling is the harder question. There is no airflow in space to carry heat away ^[4], and TPUs pack their heat into a small area ^[9]. "We're working on a number of different approaches for this, including a combination of heat pipes and radiators to cool the chips," Google wrote ^[5]. "So far, our team has tested the technology in a thermal vacuum chamber that simulates both the thermal and vacuum environment in space," the company added ^[6]. The prototype is meant to gather data about orbital conditions that ground testing cannot provide ^[15].

In my view the radiator readings are the result to wait for. Cooling is the part Google has said it will redesign from what it learns. "We'll see how our new TPU cooling system works in space and refine our designs as we learn more," the company wrote ^[7].

The flight will not show whether the design scales. The prototype carries four TPUs ^[2]. Google's longer-term design calls for satellites carrying dozens of TPUs each, flying in clusters ^[10]. Space.com describes those clusters as dozens of spacecraft ^[11]. A heat-pipe system that clears the heat of four chips says little directly about one handling dozens ^[2][10].

The clusters also need laser links with very high bandwidth over short distances, while the satellites keep track of their positions relative to one another ^[12]. "Maintaining the necessary connection requires extraordinary precision, similar to hitting a coin-size target from miles away while both points are in motion," Google wrote ^[8]. Planet will build the two satellites for that test as well, according to The New York Times ^[13].