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 pro-ceed in all types of rocket weapon, the development of a satisfactory antiaircraft wea-pon should be given the greatest emphasis. Antiaircraft rockets, though fas less accu-rate than artillery, none the less were inexpensive to procedure and could be manufactu-red 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 of a long length of pi-ano 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 evaise 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 land 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 purpose, 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 type incorporate fins of greatly reduced surface. To decreace 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 sence 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 sol-ventless extruded cordite proved remarkably adaptable to rocket use. Solventless cor-dite, identified by the code letter "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 cryclite. 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 follows:

Propellant Shape

These code letters and symbols will be found stencilled on all rocket motors giving a complete description of the propellant grain used. Thus letters "S.U./K./X." would indi-cate 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 conists of an electric squib (Fuze, Electric, No. F 53), inserted in a paper tube or metal cylinder, which also consists a quantity of igniting composition. The composition comprises magnesium, potassium nitra-te, 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.

Figure 181 – Examples of propellant grain shapes

Nomenclature

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

American

Rocket motor

Body

Nozzle

Shroud

Tetryl

Lead-dinitroresorcinate

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 mo-tor body.

The following charts set forth the available information on complete round assemblies for the various types of British rockets. They include the designation of the assembly, and the designations of its various components, including both the old and the proposed new designations for the propelling tail unit, or rocket motor.

U.P. 2-in., Anti-aircraft

Shell, H.E., 2-in. Mks I and II

No. 729 Mk IV

Tail Propelling, U. 2-in., Mks I - III

Motor, Rocket, 2-in., No. 1 Mks I - III

SU/D

Rocket

Shell, Smoke Trace, 2-in., Mk I

Thermal Initiator

2-in. Target Rocket

Head, Rocket Target, 2-in., Mk I

Pressure Armed Igniter

Propelling, Rocket Target, 2-in., Mks I

Motor, Rocket, 2-in., No. 4 Mks I and II

SU/C

and II

2-in. Flare Rocket

Head, Rocket Flare, 2-in., No. 1 Mk I

Ejector, Contents, No. 4 Mk I

Propelling Tail, Rocket Flare, 2-in., Mk VI

Motor, Rocket, 2-in. No. 1 Mks VI and VII

SU or SU/K

Head, Rocket Flare, 2-in., No. 1 Mk II

Ejector, Contents, No. 4 Mk II

and VII

Head, Rocket Flare, 2-in., No. 2 Mk I

Ejector, Contents, No. 5 Mk I

Head, Rocket Flare, 2-in., No. 3 Mk I

Ejector, Contents, No. 8 Mk I

U.P. 3-in. Anti-aircraft

Shell, H.E., 3-in. No. 1 Mk I

No. 700 Mks I - III,

Propelling Tail, U. 3-in., Mk I, or

Motor, Rocket, 3-in., No. 1 Mk I, or

SU, SU/D, SU/K,

Rocket

No. 730 Mk I, or

Propelling Tail, U. 3-in., Mk II

Motor, Rocket, 3-in., No. 2 Mk I

or SU/K/X

No. 731 Mk I

SU/K/X

Shell, H.E., 3-in. No. 2 Mk I

No. 701 Mk I

3-in. Assault Rocket, "Lilo"

Shell, H.E., 3-in., No. 5 Mk I

No. 297 Mk I

Motor, Rocket, 3-in., No. 7 Mks I and II

SU/C or SU/K/C

Shell, H.E., 3-in., No. 6 Mk I

3-in. Barrage Eocket "Land

Shell, H.E., 29-lb., 3-in., Mk I

No. 721 Mk I (with spoilers), or

Propelling Tail, Rocket, U. 3-in., Mks II

SU/X or SU/K/X

Mattress"

No. 725 Mk I

and III

and II

and II

(with delay)

(without delay)

Shot, 25-lb., S.A.P., Mk I

None

Shot, 25-lb., A.P., Mk I

Shot, 25-lb., A.P., Mk II

3-in. Aircraft Rocket

Shell, H.E., 3-in., No. 2 Mk I

No 720 Mk IV

Motor, Rocket, A/C, 3-in., Mks I and II

SU or SU/K

Air to Air

(Sunflower-Seed)

3-in. Aircraft Rocket Flare

Head, Rocket Flare, A/C, 3-in., Mk I

Ejector, Contents, No. 7 Mk I

Motor, Rocket, A/C, 3-in., Mk I,

Motor, Rocket, A/C, 3-in., No. 4 Mk I,

SU, SU/K, SU/X,

Motor, Rocket, A/C, 3-in., No. 1 Mk I or

Motor, Rocket, A/C, 3-in., No. 1 Mk I, or

or SU/K/X

Motor, Rocket, A/C, 3-in., No. 1 Mk II - IV

Motor, Rocket, A/C, 3-in., No. 5 Mks I - III

U.P. 5-in. Barrage Rocket

Bomb, U., Smoke, 5-in., Mk I/L

No. 721 Mks I - III

Propelling Tail, Rocket, U. 5-in., No. 1 Mk

SU/SG

"Sea Mattress"

Bomb, U., Incendiary, 25-lb., 5-in., Mk I/L

6/N

Shell, U., H.E., 29-lb., 5-in., Mk I/L

5-in. Cordtex Net Rocket

Cordtex Net (Obsolete)

Motor, Rocket, 5-in., Cordtex Net, Mk I

Motor, Rocket, 5-in., No. 3 Mk I

SU or SU/K

Antisubmarine Rocket

Depth Charge Mk XI

Depth Charge Pistols Mks XIV and

Motor, Rocket, 2-in., No. 5 Mk II

SU/K/CO 29

Assembly

XVI

Wire Barrage Rocket, Ap-

Head Canister, A.D. Type B

Thermal Initiator

Special Motor

SU/K

parature A.D. Type B Mk I

(Containing Bomb, H.E., A.A.D., No. 2 Mk I)

Special Fuze

Wire Barrage Rocket, Ap-

Head Canister, A.D. Type J

Thermal Initiator

Propelling Tail, U. 2-in., Mk IVA, or

Motor, Rocket, 2-in., No. 2 Mk I, or

parature A.D. Type J Mks

Propelling Tail, U. 2-in., Mk VA

Motor, Rocket, 2-in., No. 2 Mk II

SU or SU/K

I and II

Wire Barrage Rocket, Ap-

Head Canister, A.D. Type L, Mks I and II

Electric Squib and Safety Fuse

Propelling Tail, U. 2-in. Mk IVB, or

Motor, Rocket, 2-in., No. 3 Mk I, or

SU or SU/K

paratus A.D. Type L Mks

(Containing Bomb, H.E., A.A.D., No. 8 Mk I)

Special Fuze

Propelling Tail, U. 2-in. Mk VB

Motor, Rocket, 2-in., No. 3 Mk II

I and II