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The recent sinking of the Iranian warship IRIS Dena by a single Mk 48 torpedo has brought renewed attention to the U.S. Navy’s primary underwater weapon. This heavyweight torpedo, which first became operational in 1972, has seen continuous upgrades to meet the demands of modern naval combat.
The attack on the IRIS Dena marks a significant event, as it is the first instance since World War II where a U.S. submarine has utilized a torpedo to sink an enemy vessel.
“In the Indian Ocean, an American submarine took out an Iranian warship that mistakenly believed it was secure in international waters. Instead, it met its demise with a torpedo. Quiet Death,” stated War Secretary Pete Hegseth during a press conference on Wednesday.
The Navy emphasizes that the Mk 48 has been its primary undersea weapon for decades, crafted to “neutralize all threat surface ships and submarines in any ocean environment.”
In a demonstration of the U.S. Navy’s capability to load weapons at unconventional locations within the U.S. 6th Fleet area, Equipment Operator Constructionman Travis Fryar was seen directing a crane to position a hook onto an inert MK 48 training torpedo during an ordnance loading exercise at Naval Station Rota in Spain on January 13, 2017. (U.S. Navy Photo by Mass Communication Specialist 1st Class Michael C. Barton/Released)
The Mk 48 is a submarine-launched torpedo that uses information from the launching submarine and its own sensors to find and strike submarines or surface ships.
Physically, the weapon is built for destructive power. According to Navy specifications, the torpedo measures 21 inches in diameter, weighs about 3,744 pounds and carries a 650-pound high-explosive warhead.
According to the Department of the Navy’s fiscal year 2025 budget estimates, a single Mk 48 torpedo costs approximately $4.2 million.
Sailors position a Mk 48 Advanced Capability torpedo onto the Los Angeles-class submarine USS Scranton (SSN 756) on June 24, 2021, as part of ongoing U.S. Navy operations in the Indo-Pacific. (U.S. Navy photo by Chief Mass Communication Specialist Josue L. Escobosa/Released)
Lockheed Martin, one of the Mk 48 torpedo program’s primary contractors, says it can be guided in real time by wire from the launching submarine, allowing operators to update targeting information and adjust its course after launch.Â
If the wire connection is lost, the torpedo can switch to autonomous homing, relying on digital guidance systems and onboard signal processing to continue its pursuit independently.
Over time, the torpedo has evolved through hardware variants known as “Mods,” each integrating upgraded sensors, guidance and control systems, and propulsion improvements.Â
U.S. Navy Petty Officer Devin Simpson checks an MK 48 torpedo aboard the Virginia-class fast-attack submarine USS Minnesota during a port visit at HMAS Stirling in Rockingham, Western Australia, on Feb. 26, 2025. (Colin Murty/Pool/AFP via Getty Images)
The current fleet includes the Mod 7 configuration, developed in partnership with the Royal Australian Navy, while Mod 8 is in development and Mod 9 is being pursued as a rapid prototyping effort, according to the Department of War’s Fiscal Year 2024 Annual Report by the Director of Operational Test and Evaluation.
In addition to hardware upgrades, the Mk 48 undergoes recurring software updates known as Advanced Processor Builds, or APBs, which modify tactics, classification algorithms and operator interfaces to improve performance in increasingly complex undersea environments.
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