The USS Minnesota was commissioned Saturday at Naval Station Norfolk in Norfolk, Va. The Minnesota joined the Navy's fleet of attack submarines and is the 10th Virginia-class submarine. The 377-foot-long ship is capable of submerged speeds of more than 25 knots and can stay submerged for up to three months. The U.S. is building two Virginia-class submarines a year, at a cost of about $2.6 billion each. The ship will spend several months in Norfolk before moving to its designated home port of Groton, Conn. The submarine was built in Newport News, Va., under a teaming agreement between Electric Boat in Groton and Newport News Shipbuilding.