The specialized-1 rocket propelled mine, also known as the EM-52, was developed by the 710th Research Institute in 1981, and completed by 1987 after more than 100 major design changes. Specialized-1 mines are planted by surface ships in up to 200 m (660 ft) of water. The maximum speed of the mine is greater than 50 m/s (112 mph). In the early 1990s, the Specialized-1 was upgraded with a larger warhead, and the maximum depth of plant was more than doubled.