NASA's newly unfurled solar sail has started 'tumbling' end-over-end in orbit, surprising observations show

A NASA spacecraft that recently unfurled a state-of-the-art solar sail in Earth orbit is "tumbling or wobbling" through space as it circles our planet, new observations show. NASA representatives told Live Science that the unusual motion was expected but did not explain exactly what is happening.

The Advanced Composite Solar Sail System (ACS3) mission aims to test the efficacy of a new type of solar sail — a device potentially capable of propelling spaceships to faster-than-currently-available speeds using radiation pressure exerted by sunlight. Researchers hope that this type of technology could one day help propel humans to the edge of the solar system and beyond.

The ACS3 spacecraft consists of a roughly 860-square-foot (80 square meters) foil sail that, until recently, was tightly folded up within a microwave oven-size satellite, known as a CubeSat. The sail deploys from the small box using a novel series of folding booms, which are made from a new composite material that is 75% lighter and more resistant to solar radiation than the frames used in previous solar sails deployed by Russia, Japan, NASA and other private companies.

ACS3 was successfully launched into space on April 23 on board a Rocket Labs Electron Rocket that lifted off from the private company's launch pad in New Zealand. The CubeSat was positioned in a low-Earth orbit around 600 miles (965 kilometers) above our planet's surface, where it remained until scientists carried out the necessary preparations for the sail to be deployed.

The ACS3 team first attempted to unfurl the sail on Aug. 26 but abandoned the roughly 25-minute-long procedure after an "onboard power monitor detected higher-than-expected motor currents," Gizmodo previously reported. After addressing the issue, the sail was fully unfurled on Aug. 29, according to a statement from mission scientists at NASA's Ames Research Center in Silicon Valley, California.

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Initial photos of the spacecraft from Earth — including a timelapse image of the sail streaking across the night sky above the Netherlands, taken by multidisciplinary scientist Marco Langbroek — confirmed that the sail had properly deployed. But soon after, observers began to notice something unusual.