USNS Mizar, a 1850-ton Eltanin class ice-breaking cargo ship, was built at Avondale, Louisiana, for use in Arctic and Antarctic waters. Placed in service with the Military Sea Transportation Service (MSTS) in March 1958, she spent the next several years supporting military construction, base operations and scientific endeavors in Greenland and northern Canada. In late 1961, she also made one supply trip to Antarctica.

In 1963, Mizar was converted to an oceanographic research ship, with a deep-submergence support capability. She was reclassified T-AGOR-11 in April 1964, and was operated by MSTS on behalf of the Naval Research Laboratory. During the 1960s she played an important role in locating and examining the wrecks of the lost nuclear submarines Thresher and Scorpion and in finding and recovering a lost thermonuclear weapon off the coast of Spain. Later, she helped locate other sunken submarines, including the French Eurydice and the Soviet "Golf" type K-129.

Mizar was assigned to the Military Sealift Command Pacific in 1975 and was heavily modified in about 1980, resulting in a greatly changed appearance. She continued her research functions throughout that decade, but left active service in the early 1990s and was turned over to the U.S. Maritime Administration. Her classification was subsequently changed back to AK-272. At present, Mizar is part of the National Defense Reserve Fleet in the James River, Virginia.