OVERVIEW: The Mk 48 Mod 4 is a heavyweight U.S. Navy submarine-launched torpedo introduced in 1982, designed for dual anti-submarine and anti-surface warfare. It features enhanced TELCOM wire guidance, a fire-and-forget mode, and improved depth and speed envelope.

DETAILS: “Mark 48” designates the U.S. Navy’s standard 21‑inch heavyweight torpedo; “Mod 4” is the envelope-expansion upgrade to the earlier Mod 3. It retains existing dimensions (~5.8 m long, 533 mm diameter, ~1 579 kg weight) and a ~295 kg high-explosive warhead, powered by Otto Fuel II through a swash-plate piston engine. Mod 4 introduced expanded operating envelope including increased speed, diving depth, and a fire-and-forget capability that allows immediate evasive action post-launch and enhanced TELCOM guidance for better mid-course updates. It began production in 1980 and achieved Initial Operational Capability in 1982, remaining in service through the introduction of ADCAP variants.

TYPE: Heavyweight submarine-launched wire-guided dual-purpose acoustic homing torpedo

FUNCTION: Launched from 21‑inch tubes, Mk 48 Mod 4 uses two-way TELCOM wire-guidance for mid-course updates before transitioning to active/passive homing. Its fire-and-forget mode enables independent terminal phase operation, detonating via proximity or contact.

NOTE:
IOC: 1982
Manufacturer: Gould/Honeywell, Hughes Aircraft (guidance upgrades), USA
Operators: United States; allied navies (e.g., Australia, Canada, Netherlands, Brazil, Taiwan)
Platforms: U.S. Navy submarines equipped with 21‑inch torpedo tubes (e.g., Los Angeles-class SSNs, Ohio-class SSBNs)
Conflict used in: No confirmed combat deployment

SOURCE: Advanced Capabilities: U.S. Mark 48 Torpedo (Mod 4 description, envelope expansion, fire-and-forget) ; U.S. Naval Undersea Museum “MK 48 ADCAP Torpedo” (production timeline, Mod 4 entry) ; Nuclear Companion / GlobalSecurity Mod 4 specifications