A newly launched NASA spacecraft is currently tumbling through space uncontrollably as engineers work to resolve a malfunction that caused the $20 million craft to lose stability.
The spacecraft, named the Advanced Composite Solar Sail System (ACS3), is designed with four reflective ‘sails’ to test an innovative propulsion method.
However, issues arose during sail deployment when engineers detected a slight bend in one of the ‘booms’—the structural beams supporting the sails—hindering its ability to stay on course.
For now, NASA has deactivated ACS3’s attitude control system, which is responsible for stabilizing the spacecraft’s orientation, as engineers evaluate the damage. Consequently, the microwave-sized craft is currently tumbling through space.
The mission aims to trial a new propulsion system that utilizes sunlight pressure for movement, akin to a sailboat harnessing wind. This technology could one day reduce the high costs of deep space missions, but NASA first needs to regain control of the spacecraft.
ACS3 launched from New Zealand aboard Rocket Lab’s Electron rocket on April 23. However, shortly after launch, sail deployment encountered delays when an onboard power monitor registered higher-than-expected motor currents, pausing the unfolding process.
In late August, NASA successfully redeployed the sails in a second attempt, but engineers had to turn off the attitude control system to account for potential dynamic changes as the sails unfolded, and it has remained off since.
The recent discovery of a bend in one of the booms has led to further delay in reactivating the attitude control system, as engineers continue to assess potential damage.
NASA noted, “This likely occurred as the booms and sail were pulled taut to the spacecraft during deployment,” and further analysis suggests that the bend may have partially straightened over time as the spacecraft tumbled.
Currently, engineers are working to reposition the spacecraft, keeping it in “low power mode” until the sails can face direct sunlight. Once in the correct orientation, they plan to reactivate the attitude control system to halt the tumbling motion.
With the spacecraft stabilized, ACS3 will be able to orient its radio antenna toward Earth, allowing it to communicate with NASA engineers. This contact will enable the team to collect further data, refine the sail’s shape, and prepare for solar sailing maneuvers.
These sailing maneuvers will be the true test of the propulsion system, as engineers adjust the sails’ angle to modify the spacecraft’s orbit—a critical function for maneuvering ACS3.
The spacecraft currently orbits about 600 miles above Earth, roughly twice the altitude of the International Space Station.
NASA had originally disengaged the attitude control system and deployed the sails once ACS3 reached a sun-synchronous orbit, which allows the satellite to stay in sync with the sun as it circles Earth.
The ACS3 mission is designed to evaluate solar propulsion as a cost-effective solution for deep space exploration, such as missions to Mars. When fully deployed, the spacecraft’s four sails form a 30-foot-wide reflective square, held up by two diagonal booms.
Sunlight particles, or photons, striking these sails generate small bursts of momentum that push the spacecraft forward, like a sailboat using wind.
NASA describes the force exerted by sunlight as comparable to the weight of a paperclip in one’s hand—just enough for the spacecraft to overcome atmospheric drag and gain altitude.
NASA is not the first to explore solar sail propulsion. The Planetary Society’s LightSail 2, launched in 2019, gained two miles of altitude within two weeks of deploying its 300-square-foot sail. However, it eventually began losing altitude and burned up in Earth’s atmosphere.
Inspired by LightSail 2, the ACS3 mission could provide critical validation for solar sail technology. If NASA proves this propulsion method viable, it could greatly reduce fuel needs for deep space missions, significantly cutting costs.
NASA recently stated that data from this test has already proven invaluable, and the mission will continue generating essential insights for future solar sail missions.
