Unrotated Projectile

The Unrotated Projectile (UP) was a British anti-aircraft and ground-bombardment rocket of the Second World War. A 7-inch version was developed for the Royal Navy by Alwyn Crow of the Projectile Development Establishment of the Ministry of Supply at Fort Halstead. It proved unreliable and ineffective and was withdrawn from use in 1941. Development of the concept led to the UP-2 and UP-3, which had diameters of 2-inch and 3-inch respectively but were longer. The latter was used as the basis of the Z Battery anti-aircraft weapons and later developed in air-to-ground form as the RP-3, used against ground forces and shipping by aircraft like the Hawker Typhoon and the Bristol Beaufighter. In 1944–1945 several adaptations for general bombardment were produced, including Sea Mattress, Land Mattress, LILO and Tulip.