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NASA’s advanced composites solar sail system

Engineers at NASA’s Langley Research Center test deployment of the Advanced Composite Solar Sail System’s solar sail. The unfurled solar sail is approximately 30 feet (about 9 meters) on a side. Since solar radiation pressure is small, the solar sail must be large to efficiently generate thrust. NASA

Advanced Composites Solar Sail System’s, or ACS3’s, 12-unit (12U) CubeSat spacecraft bus undergoing assembly and testing. The complete ACS3 spacecraft measures approximately 9 inches x 9 inches x 13 inches (23 centimeters x 23 centimeters x 34 centimeters), or about the size of a small microwave oven.

NASA is developing new deployable structures and materials technologies for solar sail propulsion systems destined for future low-cost deep space missions. Just as a sailboat is powered by wind in a sail, solar sails employ the pressure of sunlight for propulsion, eliminating the need for conventional rocket propellant. NASA’s Advanced Composite Solar Sail System, or ACS3, technology demonstration uses composite materials – or a combination of materials with different properties – in its novel, lightweight booms that deploy from a CubeSat. Data obtained from ACS3 will guide the design of future larger-scale composite solar sail systems that could be used for space weather early warning satellites, near-Earth asteroid reconnaissance missions, or communications relays for crewed exploration missions.

The primary objective of the ACS3 technology demonstration is the successful deployment of the composites boom solar sail in low-Earth orbit. After reaching space, the ACS3 spacecraft will deploy its solar power arrays and then begin unfurling its solar sail via four booms that span the diagonals of the square and unspool to reach 23 feet (about 7 meters) in length. After approximately 25 minutes, the solar sail is fully deployed, and the square-shaped solar sail measures approximately 30 feet (about 9 meters) per side, or about the size of a small apartment. A suite of onboard digital cameras will obtain images of the sail during and after deployment in order to assess its shape and alignment.

ACS3’s sails are supported and connected to the spacecraft by booms, which function much like a sailboat’s boom that connects to its mast and keeps the sail taut. The composites booms are made from a polymer material that is flexible and reinforced with carbon fiber. This composite material can be rolled for compact stowage, but remains strong and lightweight when unrolled. It is also very stiff and resistant to bending and warping due to changes in temperature. Solar sails can operate indefinitely, limited only by the durability of the solar sail materials and spacecraft electronic systems in the space environment. The ACS3 technology demonstration will also test an innovative tape-spool boom extraction system designed to minimize jamming of the coiled booms during deployment.

Interest in solar sailing as an alternative to chemical and electric propulsion systems continues to increase. Using sunlight to propel small spacecraft in lieu of consumable propellants will be advantageous for many mission profiles and offers flexibility in spacecraft design to help NASA meet its missions’ objectives most efficiently.