The sinking of the Iranian warship IRIS Dena by a solitary Mk 48 torpedo has brought renewed attention to the nation’s primary undersea weapon, a heavyweight torpedo that first entered operational service in 1972 and has been continuously upgraded for modern naval combat.
The attack on the IRIS Dena signaled the first instance where a U.S. submarine employed a torpedo to sink an enemy vessel.
“In the Indian Ocean, an Iranian warship that believed it was safe in international waters was targeted. Instead, it was sunk by a torpedo. A quiet demise,” War Secretary Pete Hegseth stated during a press conference on Wednesday.
The Navy states that the Mk 48 has long functioned as its key undersea weapon, engineered to “defeat all threatening surface ships and submarines in all ocean settings.”
The Mk 48 is a torpedo launched from a submarine that utilizes data from the launching submarine and its own sensors to locate and target submarines or surface ships.
Physically, the weapon is constructed for destructive capability. As per Navy specifications, the torpedo has a diameter of 21 inches, weighs approximately 3,744 pounds, and carries a 650-pound high-explosive warhead.
According to the Department of the Navy’s cost estimates, a single Mk 48 torpedo is approximately $4.2 million.
Lockheed Martin, one of the main contractors for the Mk 48 torpedo program, states that it can be guided in real time via a wire from the launching submarine, enabling operators to update targeting information and adjust its course post-launch.
If the wire connection is lost, the torpedo can switch to autonomous homing, relying on external cues and onboard signal processing to continue its pursuit independently.
Over time, the torpedo has advanced through hardware versions called ‘Mods,’ each incorporating upgraded sensors, guidance and control systems, and propulsion enhancements.
The current fleet includes the Mod 7 configuration, developed in collaboration with the Royal Australian Navy, while Mod 8 is under development and Mod 9 is being pursued as a rapid prototyping initiative, as per the Department of War’s Fiscal Year 2024 Annual Report by the Director of Operational Test and Evaluation.
In addition to hardware upgrades, the torpedo undergoes recurring software updates referred to as Advanced Processor Builds, or APBs, which modify tactics, classification algorithms, and operator interfaces to enhance performance in increasingly complex undersea environments.