Mark 30 torpedo mine
The Mark 30 mine was an aircraft-launched, antisubmarine torpedo developed by the Brush Development Company during World War II. It was developed as a backup for the Mark 24 mine due to apprehensions regarding the Mark 24's acoustic steering. Three prototypes of the Mark 30 were built and tested in 1943; results were satisfactory. Production of the Mark 30 was never undertaken due to the success of the Mark 24 mine's acoustic steering.