USS Makin Island's 13-month maintenance period completed SAN DIEGO, Jan. 22 (UPI) -- The USS Makin Island, a Wasp-class amphibious assault ship, has completed sea trials following 13 months of maintenance tests, the Navy reports. The ship, built by Northrop Grumman Ship Systems, is the first U.S. Navy ship to deploy using a hybrid-electric propulsion system, which is designed to run on auxiliary propulsion motors at low speeds and on gas turbines at higher speeds. The Navy said it expects to save $250 million in fuel costs over the course of the ship's life cycle through the use of the system. During nine days of sea trials, a number of shipboard systems, including communication circuits, damage control systems, navigation systems and propulsion plant, were tested. Crew of the ship also conducted full-power runs, ballasting demonstrations and flight operations. The 13-month maintenance period included repairs, upgrades and design changes to the ship's exhaust stacks. The USS Makin Island is 847 feet long, 118 feet in the beam and has a speed of 25 knots. The ship's keel was laid down in 2004 and the ship was delivered in 2009.