The Mark 48 is a U.S. Navy heavyweight submarine torpedo used against deep-diving submarines and large surface ships. Wire-guided with active and passive acoustic homing, it uses an onboard guidance computer for tracking and responding to countermeasures. Carrying a high-explosive warhead, it is launched from standard 21-inch submarine tubes and has undergone successive upgrades to improve propulsion, sensors, and software. Publicly available descriptions emphasize its role in modern undersea warfare and technical evolution. It remains unclassified in public technical summaries.