Unrotated Projectile

The Unrotated Projectile, or UP, was a short range rocket firing anti-aircraft weapon developed for 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 World War II. The UP was also used in ground-based 128-round launchers known as Z Batteries.

Operation

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 convert|7|in|cm diameter rocket out of the tube to a distance of about convert|1000|ft|m where it exploded and released an convert|8.4|oz|g mine attached to three parachutes by convert|400|ft|m of wire. The idea was that a plane hitting the wire would draw the mine towards itself where it would detonate.

Development

The UP was developed by Sir Alwyn Crow who was the director of the Projectile Development Establishment at Fort Halstead. In November 1939, Winston Churchill as First Lord of the Admiralty asked Dr. Crow to produce urgently a means of laying an aerial minefield and to consider other methods of protecting ships against aircraft. It is likely that Churchill was influenced in his request by his friend and advisor Frederick Lindemann who had previously advocated a scheme for "dropping bombs hanging by wires in the path of attacking aircraft". [Furneaux-Smith, 1961, p210.] A high-altitude barrage was developed: an aerial minefield up to convert|19000|ft, the fast aerial mine up to convert|2000|ft, the PE fuse up to convert|18000|ft and the UP up to convert|20000|ft. All three services, including the Home Guard, used the UP in various forms. [Furneaux-Smith, 1961, p234.]

Combat effectiveness

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

pecifications

* Rocket length: convert|32|in
* Rocket weight: convert|35|lb
* Horizontal range: convert|3000|ft
* Sinking speed of mine: 16 to 23 feet per second (5 to 7 m/s).
* Mounting weight: convert|4|t|MT.

ee also

* AA Mine Discharger, a Japanese anti-aircraft mortar.
* Holman Projector, a steam powered anti-aircraft grenade launcher.

References

Notes

ources

*cite book | title=The Professor and the Prime Minister: The Official Life of Professor F. A. Lindemann Viscount Cherwell | author= Furneaux-Smith, F. | authorlink = Frederick Smith, 2nd Earl of Birkenhead | year=1961 | publisher=Boston: Houghton Mifflin Company

External links

* http://navweaps.com/Weapons/WNBR_UP.htm
* http://www.hmshood.com/ship/specifications/aaa.html
* [http://www.undergroundkent.co.uk/z_rocket.htm Z Rocket]