Lockheed Martin has selected Alliant Techsystems (ATK) to develop the Orion crew exploration vehicle's solar arrays. The disk-shaped arrays, each wider than 5m (16.3ft), will be fitted to the Orion's expendable service module and will track the Sun. "The UltraFlex solar array will provide over 25 times the strength and 10 times the stiffness of conventional rigid panel solar arrays, at less than one-fourth the weight," says ATK. Because the service module is expendable, there is a need for continuous solar array production from 2015.UltraFlex solar arrays have already been used for NASA's Phoenix Mars lander.