British Rockets

General

The development of rocket-type ammunition was begun by the British several years prior to the entrance of Great Britain into World War II. As early as 1936 experiments were begun in the field of rocketry. It was felt that, though experimentation should proceed in all types of rocket weapons, the development of a satisfactory antiaircraft weapon should be given the greatest emphasis. Antiaircraft rockets, though far less accurate than artillery, none the less were inexpensive to produce and could be manufactured in quantities sufficient to allow complete saturation of a defensive area.

Accordingly, in 1940 when the German “blitz” began, two antiaircraft rocket weapons were introduced into service use, the 2-in. U.P. (2-inch Unrotated Projectile) and the 3-in. U.P. These consisted of high explosive heads fitted to a standard type, fin stabilized rocket motor, and fuzed with impact or pyrotechnic delay aerial burst fuzes.

Not much later, a novel type antiaircraft defense was developed in the “Wire Barrage” or “Aerial Mine Field” apparatus. This device was propelled or towed by a standard rocket motor. Its function was to suspend from a parachute a steel cable or a long length of piano wire with a small H.E. bomb attached. The apparatus served to break up an aircraft, if it struck the wire or cable, or to cause the aircraft to take evasive action and thus leave its target run. This type of apparatus was found to be particularly effective for defense of merchant ships against low-level or dive-bombing aircraft.

At about the same time, a 5-in. chemical rocket, the 5-in. U.P., was adopted for service use. The rocket proved to have few profitable uses and was turned over to the British Navy. The Navy manufactured a high explosive, a smoke, and an incendiary shell for the rocket, mounted the launcher on a converted landing craft, and used it for beach barrage purposes, christening it the “Sea Mattress”.

Developments in other fields of rocketry included aircraft rockets for attacks against armored vehicles, merchant shipping, and submarines. More recently an assault rocket for infantry' use and a land barrage rocket, designed as a medium-range artillery support weapon, have been introduced.

Stabilization

Though all British service rockets are designed solely for fin stabilization, more recent types incorporate fins of greatly reduced surface. To decrease the amount of dispersion caused by venturi variations, spiral rails have been fitted to the inside of the launcher barrel. The short fins engage these rails and impart a spin of about 800-900 r.p.m. to the rocket. However, this is not spin stabilization in the accepted sense of the term.

Propellant

The British rocket program was aided in its early stages by the ready availability in large quantities of a good and relatively inexpensive rocket propellant. The British have long employed a type of cordite as their principal projectile propellant charge, and solventless extruded cordite proved remarkably adaptable to rocket use. Solventless cordite, identified by the code letters “S.U.”, is a double-base powder consisting of 41.5% nitroglycerine, 49.5% nitrocellulose, and 9.0% carbamite, as a stabilizer. Flashless cordite is obtained by adding potassium cryolite. Flashless charges are identified by the symbol “/K.” added to the propellant code letters.

Several different propellant shapes have been designed by the British, always in an attempt to gain the most efficient burning of the propellant. The charge shapes and identifying symbols are as follows:

Propellant Shape

Symbol

Tubular, drilled

/D

Tubular, slotted

/S

Tubular, slotted and grooved

/S.G.

Cruciform

/X

Cogged

/C

These code letters and symbols will be found stenciled on all rocket motors giving a complete description of the propellant grain used. Thus the letters “S.U./K./X.” would indicate a cruciform grain of flashless solventless cordite; the letters “S.U./S.G.”, a tubular grain of solventless cordite, slotted and grooved; etc.

The standard ignition mechanism for British rockets consists of an electric squib (Fuze, Electric, No. F. 53), inserted in a paper tube or metal cylinder, which also contains a quantity of igniting composition. The composition comprises magnesium, potassium nitrate, and a small amount of acaroid resin as a stabilizer The igniter is generally fitted into castellations cut in the head of the propellant grain.

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Nomenclature

British rocket nomenclature differs somewhat from that employed by U.S. forces. American and British equivalents follow.

American

British

Rocket motor

Propelling tail

Body

Shell—with H.E., smoke, chemical, or incendiary filling Head—with flares, targets, etc.
Shot—solid steel bodies

Nozzle

Venturi

Shroud

Drum

Tetryl

C.E.

Lead dinitro resorcinate

L.D.N.R.

Note: Propelling tail is the original British nomenclature. It has been recently proposed by the British to revise their nomenclature, using the term rocket motor. Where applicable, the proposed new nomenclature has been included in the discussion of the individual rocket motors.

Complete Round Assemblies

A complete assembly will usually consist of a fuze, shell, a motor, and fins. Rockets employing separate shells generally employ a shell ring to join the shell and the motor. The shell ring consists of a cylindrical metal tube which fits inside the motor body and is held in place by a number of pins protruding from its wall. These pins are spring-loaded outward by a circular spring, and engage holes in the forward end of the motor body. The forward end of the shell ring is threaded to take the shell. Motors employing large tail fins usually employ separate fins for convenience in packaging for shipment. These fins are fitted with a double set of hooks, which engage slots in the after end of the motor body.

Source(s)

OP 1665, British Explosive Ordnance (1946)