What is the difference between Navy ships called USS (United States Ship) and USNS (United States Naval Ship)?
United State Naval Ships are in Military Sealift Command, and usually carry a contingent of U.S. Navy – radiomen, etc – and a civilian crew. They also can carry additional technicians and support, depending on their mission. USS (United States Ship) are commissioned warships and auxilaries, and while they may occasionally carry some civilians, are always fully crewed with sailors. It’s not a size thing.