OVERVIEW: The Mark 8 Straight Runner is a heavyweight U.S. Navy torpedo introduced in 1911 for anti-surface warfare. It is a straight-running, gyroscope-stabilized steam-powered weapon primarily launched from destroyers and PT boats.

DETAILS: “Mark 8” was the first 21‑in (533 mm), 21‑ft (6.51 m) torpedo in U.S. service, developed by Bliss–Leavitt and entering production in 1913. It weighs approximately 1 200–1 260 kg, carrying a 211 kg TNT (or later Torpex) warhead, and reaches speeds around 36 kn over ~15 km range using a turbine with air‑alcohol and water steam propulsion. It uses gyroscopic straight-run guidance with no homing capability. The Mark 8 saw service on destroyers, PT boats, and battleships; it remained in use through World War II, with PT boats relying on it until mid-1943, and lend-leased units used by the Royal Navy.

TYPE: Heavyweight straight-running steam-powered torpedo

FUNCTION: Fired from destroyer or PT-boat tubes, it runs a preset course using gyroscopic stabilization, powered by a steam turbine, to strike surface ships on contact.

NOTE:
IOC: 1911–1913
Manufacturer: Naval Torpedo Station Newport; Naval Gun Factory, USA
Operators: United States; Royal Navy (via Lend-Lease)
Platforms: U.S. destroyers, PT boats, battleships
Conflict used in: World War I; World War II (limited use, PT boats until 1943; sinking of HMS Belgrano off UK destroyers also reported for British Mark VIII)

SOURCE: Bliss–Leavitt Mark 8 torpedo – Wikipedia; Mark VIII torpedo – WeaponsSystems.net