An experiment that recently arrived at the International Space Station will test a new solar array design that rolls up to form a compact cylinder for launch with significantly less mass and volume, potentially offering substantial cost savings as well as an increase in power for satellites. Smaller and lighter than traditional solar panels, the Roll-Out Solar Array, or ROSA, consists of a center wing made of a flexible material containing photovoltaic cells to convert light into electricity. On either side of the wing is a narrow arm that extends the length of the wing to provide support, called a high strain composite boom. The booms are like split tubes made of a stiff composite material, flattened and rolled up lengthwise for launch. The array rolls or snaps open without a motor, using stored energy from the structure of the booms that is released as each boom transitions from a coil shape to a straight support arm. ROSA can be easily adapted to different sizes, including very large arrays, to provide power for a variety of future spacecraft. It also has the potential to make solar arrays more compact and lighter weight for satellite radio and television, weather forecasting, GPS and other services used on Earth. In addition, the technology conceivably could be adapted to provide solar power in remote locations. The technology of the booms has additional potential applications, such as for communications and radar antennas and other instruments. The ROSA investigation looks at how well this new type of solar panels deploys in the microgravity and extreme temperatures of space. The investigation also measures the array's strength and durability and how the structure responds to spacecraft maneuvers. "When the array is attached to a satellite, that spacecraft will need to maneuver, which creates torque and causes the wing, or blanket, to vibrate," said Jeremy Banik, principal investigator and senior research engineer at the Air Force Research Laboratory, Kirtland Air Force Base in New Mexico. "We need to know precisely when and how it vibrates so as not to lose control of the spacecraft. The only way to test that is in space." The investigation will monitor the array deployed in full sun and full shade and collect data on how much it vibrates when moving from shade to light. This vibration, known as thermal snap, could present challenges in operating satellites with sensitive functions, and the researchers want to learn how to avoid those challenges with ROSA. The investigation will also measure power produced by the array to see how ROSA's thin, crystalline photovoltaic cells hold up during launch. In addition, researchers want to see how the array handles retraction. "Recognize that we are trying to learn how it behaves — this is an experiment and not a demonstration — so we'll glean useful data even if it doesn't behave the ways we expect," Banik said. ROSA was developed as part of the Solar Electric Propulsion project sponsored by NASA's Space Technology Mission Directorate. NASA tested the ROSA technology in vacuum chambers on Earth several years ago, and this is its first test in space. This solar array technology was developed to power large spacecraft using highly efficient electric propulsion on missions to deep space including Mars and the moon.