FILE PHOTO: The Virginia-class USS North Dakota submarine is seen

FILE PHOTO: The Virginia-class USS North Dakota (SSN 784) submarine is seen during bravo sea trials in this U.S. Navy handout picture taken in the Atlantic Ocean August 18, 2013. The Navy commissioned its newest attack submarine North Dakota, during a ceremony October 25, 2014, at Submarine Base New London in Groton, Connecticut, defense officials announced. REUTERS/U.S. Navy/Handout