Uh oh.

Rough and Tumble

NASA’s Advanced Composite Solar Sail System (ACS3), a dazzling spacecraft designed to make use of the tiny amounts of radiation pressure exerted by sunlight for propulsion, is still spinning through space uncontrollably.

In an update last week, the space agency admitted that the solar sail is “still slowly tumbling” in orbit because its “attitude control system is not yet reengaged.”

After launching the unusual payload on April 23, ACS3 unfurled its 860-square-foot sail in early September. Since then, NASA has taken things slow, allowing for the significantly changing dynamics of the unfurling spacecraft to take effect before turning on its attitude control system, which points it in the right direction.

Unfortunately, the space agency is dealing with a “slight bend in one of the four booms” stretching out the sail.

“This likely occurred as the booms and sail were pulled taut to the spacecraft during deployment,” NASA wrote in its update. “Analysis indicates that the bend may have partially straightened over the weeks since boom deployment, while the spacecraft was slowly tumbling.”

Boom Stick

It’s especially unfortunate given ACS3’s primary objective is to test out new “composite boom technology” for even larger solar sails in the future.

However, NASA says that “data collected from this flight test has already proven highly valuable, and the demonstration will continue producing critical information to enable future solar sail missions.”

The bend isn’t expected to pose any major issues to the ongoing mission, NASA said.

Teams at the agency are now waiting for ACS3 to keep spinning until it’s facing directly towards the sunlight for optimal power generation. At that point, its attitude control system will reactivate to allow it to right itself.

It’s far from the first solar sail to be deployed, but ACS3 could lay important groundwork for future solar sails like it — a clever, extremely low-cost form of propulsion that could enable an entirely new generation of spacecraft.

More on the solar sail: NASA’s Experimental Solar Sail Is Tumbling in Orbit

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