Most people are familiar with various types of mainline fighting ships used by modern navies - frigates, destroyers, missile cruisers, and aircraft carriers come readily to mind - but navies also have special purpose vessels that receive much less attention.
Here's a sampling of a few of the latter type used by the US navy in the late twentieth century.
Click on the pictures for complete details of these postcards.
The USS Norton Sound started out its service career as a seaplane teader with the Pacific Fleet at the end of WW II but underwent conversion to a floating laboratory platform for guided missile projects during the Cold War.
The USNS Observation Island was a forerunner for use in the Polaris/ Poseiden missile programs, operating in the Military Sealift Command of the US Navy.
The USNS Hayes served as an oceanographic research ship operated by the Military Sealift Command for the Office of Naval Research. It's catamaran design was adopted to provide a stable work platform with a center well to operate research equipment at great depths.