Why can Google's AI chip in orbit only run in bursts?

On 30 October 2026 Google said a TPU, its own AI chip, had run Gemma 4 on board its first Project Suncatcher satellite and sent back its first complete answer from orbit, a haiku: “Blue marble below, / Data streams in silent grace, / Starlight feeds my core.” The satellite, built with Planet and carrying four TPUs, launched on SpaceX’s Transporter-18 rideshare on 1 October. But NPR reported that its chips run a Gemma model for only about 15 minutes at a time, because of heat. Why can an AI chip in orbit only run in bursts?

▶ Try it yourself in Orbit Chip Lab: turn up the chip’s power, grow the radiator or change the time in Earth’s shadow, and watch the temperature climb to the limit and the bursts shrink or vanish.

Space is cold but empty

On Earth a hot chip hands its heat to the air: a fan pushes cool air across metal fins and carries the warm air away. In orbit there is almost no air, so there is nothing for a fan to push, and the vacuum around a satellite insulates it like the walls of a vacuum flask. Heat has one way out: light. Every surface glows in the infrared, and a radiator’s glow grows with its area and with its temperature to the fourth power. A white radiator panel at 60 °C glows away about 590 watts per square metre, less whatever sunlight and Earth light it soaks up.

A small radiator can’t keep up

Google hasn’t published its chips’ power or the size of its radiators, so the tool uses an illustrative satellite: a 300 W chip, heat pipes, and a 0.5 m² radiator that can glow away at most about 220 W before it reaches 60 °C. The chip makes more heat than that, so the extra soaks into the metal of the chip, the pipes and the panel, and the temperature climbs. The model is tuned so it reaches the 60 °C limit in 15 minutes, the figure reported for Google’s prototype. Then the chip must stop, and the radiator takes about 11 minutes in sunlight to cool it back to 30 °C, or 8.5 in Earth’s shadow, where it soaks up less light. Run, rest, run: bursts.

Twice the power, less than a third of the run

A burst lasts about as long as the metal takes to absorb the surplus: the heat it can hold between 30 and 60 °C divided by what the chip makes beyond what the radiator sheds. Double the chip to 600 W and the surplus more than doubles, so each burst shrinks from 15 minutes to about 4, while the cool-down stays the same. Over a 95-minute orbit the chip computes about 31 minutes instead of 65. A radiator big enough to shed the chip’s whole output at 60 °C lets it run nonstop: about 0.7 m² for 300 W, 1.4 m² for 600 W, and about 90 m² for a 40 kW data-centre rack, a third of a tennis court.

Radiators are heavy

That is the trade. Travis Beals, who leads Project Suncatcher, told NPR the radiators are among the heaviest components of the current mission, and every kilogram has to be launched. Google calls cooling the chips a crucial research challenge. Heat isn’t the only limit, either: TechCrunch reported that the satellite’s power demands allow only one TPU on at a time, for about 20 minutes. Google’s long-term design puts satellites in a dawn–dusk orbit with nearly constant sunlight, which helps the power but gives the radiators no shade. For how radiators work in general, and why space data centres are as much a radiator problem as a power one, see Space Radiator Lab.

The tool is an illustrative model with one temperature for the whole heat path, not a model of Google’s satellite; a real chip runs tens of degrees hotter than its radiator. The film uses two short clips, credited on screen: the Falcon 9 launch from Google’s post (@Google) and the ground-station terminal as the haiku arrived, from Sundar Pichai’s post (@sundarpichai); the satellite, Earth, graphs and numbers are drawn from the model.

Sources: Google Research, Exploring a space-based, scalable AI infrastructure system design (Travis Beals, 4 Nov 2025); NPR, Google launches Project Suncatcher, a step towards AI data centers in space (1 Oct 2026); Google, the satellite’s first response from orbit (30 Oct 2026); TechCrunch, Google’s first data center satellite is online and writing poetry (30 Oct 2026); Wikipedia, Stefan–Boltzmann law.