China's space agency reportedly tested a Stirling converter in orbit

Stirling converters could allow deep space missions to massively reduce their reliance on potentially scarce solar energy.
Chris Young
Chinese Tianhe core module of the Tiangong space station
Chinese Tianhe core module of the Tiangong space station


China's Shenzhou-15 mission crew aboard the China Space Station (CSS) has reportedly completed testing on a free-piston Stirling thermoelectric converter, according to a report from state-owned media in China.

The successful test marks the first time China has verified this type of technology in orbit. The experimental technology, which NASA has also investigated, has the potential to provide crucial backup energy to deep space missions.

NASA and China have both experimented with Stirling converters

The Stirling thermoelectric converter is an energy supply technology for space travel that efficiently converts thermal energy into electric energy, enabling spacecraft to reduce their reliance on solar power.

In the Stirling converter, a piston is set in motion by heat generated by a fuel source. The piston then moves a magnet back and forth through a coil of wire to generate an electrical current. The piston is typically suspended in a helium gas bearing to prevent physical wear.

The Lanzhou Institute of Physics at the China Academy of Space Technology developed an iteration of the Stirling converter. According to the CGTN report, it is lightweight, has a simple structure, makes little noise, starts up quickly, and doesn't vibrate much, making it ideal for spacecraft.

The report also claims the technology could play a vital role in the China National Space Administration's (CNSA's) plans to send crewed missions to the Moon and deep space.

China's space industry has made great strides in recent years. Last week, a Chinese startup called Space Pioneer became the first startup in the world to reach orbit on its first launch attempt. The CNSA, meanwhile, recently finished constructing its Tiangong space station, and it performed the first in-situ detection of water from the lunar surface with its Chang'e-5 lunar probe last year.

NASA has also experimented with Stirling converter technology, though its Advanced Stirling Radioisotope Generator (ASRG) was discontinued in 2013. An animation of the technology NASA was working on can be viewed in the video below.

China's Tiangong space station enables in-orbit Stirling converter test

In order to test the Stirling converter technology, prototypes were sent up to the China Space Station, also known as the Tiangong Station, where they were installed in the equipment cabinet of the station's Mengtian lab module.

The device reportedly ran stably during the test and produced "better-than-expected" performance indicators, according to CGTN. It's worth noting that the CNSA has remained tight-lipped about the technology, and no concrete numbers have been shared.

The Mengtian lab of the CSS was launched in October 2022. It was the third and final module to be launched to orbit, marking the completion of the CSS. The module is used to study microgravity and perform experiments in materials science, fluid physics, and other fields.

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