Thus, solar sails are common but only i a narrow range of applications - civilian freighters, passenger liners and research system ships. They will never be found as military, courier or pirate craft. Since their power plants generate minimal energy emissions, solar sail equipped ships are invisible to energy sensors. Deploying and reeling in a sail requires 1 turn per 10,000 square meters of sail area. Primitive sails were built using ultrathin thin mylar for the sails and high-strength copper alloys for the support cables.
Solar sails are the only drive that can be mounted in addition to traditional engines.
Where traditional engines are mounted at the back of a ship's hull, sails are mounted at the front end, towing the ship along behind. This allows them to be stowed in compartments mounted on the outer hull of a ship or in internal cargo bays.