Unrotated Projectile

Rocket length: 32 inches (81.3 cm)
Rocket weight: 35 lb (15.9 kg)
Horizontal range: 3,000 feet (910 m)
Sinking speed of mine: 16 to 23 feet per second (5 to 7 m/s).
Mounting weight: 4 tons (4 mt).

From Wikipedia, the free encyclopedia

The Unrotated Projectile was a short range rocket firing anti-aircraft weapon developed by the Royal Navy to supplement the 2 pounder Pom-Pom (gun) due to a critical lack of close-range anti-aircraft weapons. It was used extensively by British ships during the early days of Second World War.

The name Unrotated Projectile comes from the fact that the projectile was not spin-stabilized. The weapon had 20 smoothbore tubes, fired ten at a time. A small cordite charge was used to ignite a rocket motor which propelled the fin-stabilized 7-inch (17.8 cm) diameter rocket out of the tube to a distance of about 1,000 feet (330 m) where it exploded and released an 8.4 oz (238 g) mine. The mine attached to three parachutes by 400 feet (122 m) of wire. The idea was that a plane hitting the wire would draw the mine towards itself where it would detonate.

The weapon was never very effective - as planes could simply avoid the wires, also the weapon was slow loading. The weapon was replaced later in the war by the 2 pounder or Bofors 40 mm gun.