OVERVIEW: The Mk 9 is an unguided, surface-deployed naval depth charge introduced by the United States Navy in 1943. Its streamlined, teardrop design and fin stabilization enabled faster sinking to target submarines at depth.

DETAILS: The Mk 9 depth charge was designed in 1941 and entered service in spring 1943. It measures approximately 27.5 in (70 cm) in length with a diameter of ~18 in (46 cm) and weighs around 380 lb (172 kg), carrying a 200 lb (91 kg) Torpex warhead. The teardrop case and fins induce a spin-stabilized descent at ~22.7 fps (6.9 m/s), significantly faster than earlier cylindrical models. Depth settings ranged from 50 to 300 ft (15–91 m), with Mod 3 versions able to reach 600–1,000 ft (183–305 m).

FUNCTION: The Mk 9 is deployed from stern racks or K‑guns following sonar contact, sinking rapidly and detonating at preset depths via hydrostatic pistols. Its purpose is to inflict sufficient underwater shock to damaged or destroy submerged submarines.

NOTE:
IOC: 1943 (Mk 9 base), Mod 3 by mid-1944
Operators: United States Navy, U.S. Coast Guard
Platforms: Destroyers and destroyer escorts equipped with stern racks and K‑gun projectors
Conflict used in: World War II (Atlantic and Pacific escort operations)

SOURCE:
Warships.com.cn: USA ASW Weapons – Mk 9 depth charge; Bill Maloney (US Navy Museum): Mk 9 Depth Charge Cutaway; International Military Antiques LLC listing (Mk 9 Mod 3 inert); Paperzz: “An Explosive Story – Mk 9 development”; William Maloney Slater DE photos; Infogalactic & QA.edu.vn depth charge data.