NASA’s experimental solar sail is ready to take flight in Earth orbit, using the pressure of sunlight to test a new way of propulsion through the cosmos.
The Advanced Composite Solar Sail System(ACS3) is scheduled for launch on Tuesday, April 23 on board Rocket Lab’s Electron rocket from New Zealand. The mission will use composite booms in Earth orbit for the first time, testing their ability to deploy the sail in orbit.
The rocket will deploy the microwave-sized cubesat about 600 miles (966 kilometers) above Earth (more than twice the altitude of the International Space Station), where it will begin unfurling its solar sail to stretch across 30 feet (9 meters) per side.
The process of unfurling will take about 25 minutes, and NASA has equipped the mission with a suite of onboard digital cameras to capture images of the sail during and after deployment to assess its shape and alignment.
Once unfurled, the solar sail system will become around the same size as a tiny studio apartment in Bushwick. The sail has to be large enough to efficiently generate thrust, and at a high enough orbit to be able to gain altitude and overcome atmospheric drag using the tiny force of sunlight on the sail, which is roughly equivalent to the weight of a paperclip resting on your palm, according to NASA.
The solar sail will be deployed using four composite booms that span the diagonals of the square to reach 23 feet (7 meters) in length. They work the same way as a sailboat’s boom, except they are designed to catch the propulsive power of sunlight rather than wind. The composite booms are made from a polymer material; they’re lightweight while still being stiff and resistant to bending and warping when exposed to different temperatures.
The mission’s initial flight phase will last for around two months and will include a series of pointing maneuvers to demonstrate orbit raising and lowering using only the pressure of sunlight acting on the sail, NASA wrote.
Solar sails run on photons from the Sun, causing small bursts of momentum that propel the spacecraft farther away from the star. If a spacecraft is able to surpass the drag from Earth’s atmosphere, it could potentially reach very high altitudes.
In theory, solar sails can operate indefinitely. They are, however, limited by the durability of the solar sail materials and spacecraft electronic systems. The Planetary Society’s LightSail 2 launched in June 2019 and gained 2 miles (3.2 kilometers) of altitude just two weeks after unfurling its 344-square-foot (32-square-meter) solar sail. In November 2022, the mission came to a fiery end after it began losing altitude and reentered through Earth’s atmosphere.
The legacy of LightSail 2 inspired several other missions in its wake, including ACS3, as well as NASA’s NEA Scout mission to a near-Earth asteroid and NASA’s Solar Cruiser (scheduled for a 2025 launch).
The composite boom technology used for this demo mission could be used to deploy solar sails up to 500 square meters (5,400 square feet), or about the size of a basketball court.
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