British Explosive Ordnance
Rockets Introduction
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 anti-aircraft weapon should be given the greatest emphasis. Anti-aircraft 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 anti-aircraft rocket weapons were introduced into service use, the 2-in UP (2-inch Unrotated Projectile) and the 3-in UP. 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 anti-aircraft 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 HE 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 UP, 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 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 the venture variations, spiral rails have been fitted to the inside of the launcher barrel. The short fins engage these rails and impart spin of about 800-900 rpm 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% 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 ----- /SG
Cruciform --------------- /X
Cogged --------------- /C
These code letters and symbols will be found stencilled on all rocket motors giving a complete description of the propellant grain used. Thus, the propellant 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 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.
Nomenclature
British rocket nomenclature differs somewhat from that employed by US forces. American and British equivalents follow.
American ------- British
Rocket Motor ------- Propelling tail
Body ----- Shell - with HE, smoke, chemical, or incendiary filling
----- Head - with flares, targets, etc
----- Shot - solid steel bodies
Nozzle -------- Venturi
Shroud ----- Drum
Tetryl ----- CE
Lead-dinitro-resorcinate ---- LDNR
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 engages 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.
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.
High Explosive Rockets
Introduction
This chapter contains details of the various rocket assemblies, whose main purpose is to carry HE charged shells. As a matter of convenience, several other types of shells, such as the smoke trace, SAP shot, AP shot, etc., are discussed under the assembly with which they are used.
The types of rockets dealt with include anti-aircraft rockets, land and sea barrage rockets, aircraft-launched rockets, a demolition rocket, and an anti-submarine rocket assembly.
2-in UP Anti-Aircraft Rocket (Service)
H.E.
Overall length: 5.25 inches
Diameter: 2.25 inches
Total weight: 2.25 pounds
Fuzes used: No.720
Filling: TNT
Filling weight: 9 ounces
Smoke Trace
Overall length: 5.5 inches
Diameter: 2.25 inches
Total weight: 2.25 pounds
Fuzes used: Thermal Initiator
Filling: Smoke P.N.83(M)
Filling weight: 5.6 ounces
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 anti-aircraft weapon should be given the greatest emphasis. Anti-aircraft 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 anti-aircraft rocket weapons were introduced into service use, the 2-in UP (2-inch Unrotated Projectile) and the 3-in UP. 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 anti-aircraft 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 HE 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 UP, 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 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 the venture variations, spiral rails have been fitted to the inside of the launcher barrel. The short fins engage these rails and impart spin of about 800-900 rpm 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% 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 ----- /SG
Cruciform --------------- /X
Cogged --------------- /C
These code letters and symbols will be found stencilled on all rocket motors giving a complete description of the propellant grain used. Thus, the propellant 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 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.
Nomenclature
British rocket nomenclature differs somewhat from that employed by US forces. American and British equivalents follow.
American ------- British
Rocket Motor ------- Propelling tail
Body ----- Shell - with HE, smoke, chemical, or incendiary filling
----- Head - with flares, targets, etc
----- Shot - solid steel bodies
Nozzle -------- Venturi
Shroud ----- Drum
Tetryl ----- CE
Lead-dinitro-resorcinate ---- LDNR
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 engages 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.
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.
High Explosive Rockets
Introduction
This chapter contains details of the various rocket assemblies, whose main purpose is to carry HE charged shells. As a matter of convenience, several other types of shells, such as the smoke trace, SAP shot, AP shot, etc., are discussed under the assembly with which they are used.
The types of rockets dealt with include anti-aircraft rockets, land and sea barrage rockets, aircraft-launched rockets, a demolition rocket, and an anti-submarine rocket assembly.
2-in UP Anti-Aircraft Rocket (Service)
H.E.
Overall length: 5.25 inches
Diameter: 2.25 inches
Total weight: 2.25 pounds
Fuzes used: No.720
Filling: TNT
Filling weight: 9 ounces
Smoke Trace
Overall length: 5.5 inches
Diameter: 2.25 inches
Total weight: 2.25 pounds
Fuzes used: Thermal Initiator
Filling: Smoke P.N.83(M)
Filling weight: 5.6 ounces
Rocket Motor:
Overall length: 31 inches (approx.)
Diameter: 2.25 inches
Width of fins: 2.375 inches
Total weight: 7.5 pounds
Propellant: Tubular cordite
Propellant weight: 2.5 pounds
Burning time at 60 degrees Fahrenheit: 0.9 seconds
Overall length: 31 inches (approx.)
Diameter: 2.25 inches
Width of fins: 2.375 inches
Total weight: 7.5 pounds
Propellant: Tubular cordite
Propellant weight: 2.5 pounds
Burning time at 60 degrees Fahrenheit: 0.9 seconds
General: This rocket is designed for shipboard use against aircraft in close-range attack. Because of the possible danger to adjacent craft resulting from spent rounds, the HE shell is fitted with a self-destroying fuze. The components of the complete round include a fuzed Shell, H.E., 2-in, Mks I or II or a Shell, Smoke Trace, 2-in, Mk I, and a Propelling Tail, U, 2-in, Mks I-III, complete with fin assembly.
Description
Shell, H.E., 2-inch, Mks I and II: This shell is a normal H.E. type, internally threaded at the nose to receive the fuze, and threaded externally at the base to screw into the shell ring of the rocket motor. The Shell Mk I, having 12 external threads per inch, will fit only the Mk I Motor. The Shell Mk II is machined with 14 threads per inch, and will fit all other motors. The shell is painted buff overall, with a 1/2-inch red band around the nose portion of the shell, and a 1/2-inch green band around the body. The initials of the filling are stencilled in black on the green band.
Shell, Smoke Trace, 2-inch Mk I: This shell consists of an H.E. Shell Body, Mk II, modified by drilling and tapping the base of the shell. A nose plug is threaded into the forward end of the shell and is centrally drilled to allow smoke emission. The drilled hole is closed by a thin metal disc and a cotton cambric disc. Upper and lower perforated tubes surrounded by primed cambric are separated from the nose plug by two millboard washers. The smoke filling is loaded around these tubes in two increments. Beneath the lower perforated tube is located a metal container filled with 7 grains of G.20 gunpowder.
The after end of the shell is closed by a threaded thermal septum of accurately machined thickness, in the center of which are pressed 2.5 grans of LDNR. The shell is painted light green overall, with two 1/2-inch red bands painted around the body. Heat from the rocket motor initiates the LDNR, firing the gunpowder charge and primed cambric, which initiates the smoke composition. The gunpowder explosion also blows the discs out of the nose plug of the shell.
Tail, Propelling, U. 2-inch, Mks I-III: The motor consists of a welded steel cylinder, to the head of which a threaded shell ring is attached by means of spring-locked pins which engage holes in the motor body. A venture tube is welded in the after end of the motor body. The tubular cordite grain is castellated at the forward end and rests in the motor body, supported by a metal grid at the after end. The propellant is initiated by an electric igniter placed in the castellations at the forward end. The tail orifice is sealed by a cardboard, plastic, or metal closing disc, and a silica gel bag is included as a moisture-proofing measure.
Electric leads from the igniter pass through the central channel of the cordite grain to the four brass contacts on the tail. These contacts, two positive and two negative, are so arranged that proper contact is maintained with the knife edges on the projector, regardless of the angle at which the round is loaded.
The motor is generally painted white or green overall, with identification markings stencilled on the outside. Proposed new nomenclature for the motors is as follows: Motor, Rocket, 2-inch, No.1 Mks I-III.
Remarks: These rounds must not be fired outside of the temperature ranges of 0 and 120 degrees Fahrenheit, unless filled with flashless cordite, which may be fired at temperatures between -5 and 130 degrees Fahrenheit.
Description
Shell, H.E., 2-inch, Mks I and II: This shell is a normal H.E. type, internally threaded at the nose to receive the fuze, and threaded externally at the base to screw into the shell ring of the rocket motor. The Shell Mk I, having 12 external threads per inch, will fit only the Mk I Motor. The Shell Mk II is machined with 14 threads per inch, and will fit all other motors. The shell is painted buff overall, with a 1/2-inch red band around the nose portion of the shell, and a 1/2-inch green band around the body. The initials of the filling are stencilled in black on the green band.
Shell, Smoke Trace, 2-inch Mk I: This shell consists of an H.E. Shell Body, Mk II, modified by drilling and tapping the base of the shell. A nose plug is threaded into the forward end of the shell and is centrally drilled to allow smoke emission. The drilled hole is closed by a thin metal disc and a cotton cambric disc. Upper and lower perforated tubes surrounded by primed cambric are separated from the nose plug by two millboard washers. The smoke filling is loaded around these tubes in two increments. Beneath the lower perforated tube is located a metal container filled with 7 grains of G.20 gunpowder.
The after end of the shell is closed by a threaded thermal septum of accurately machined thickness, in the center of which are pressed 2.5 grans of LDNR. The shell is painted light green overall, with two 1/2-inch red bands painted around the body. Heat from the rocket motor initiates the LDNR, firing the gunpowder charge and primed cambric, which initiates the smoke composition. The gunpowder explosion also blows the discs out of the nose plug of the shell.
Tail, Propelling, U. 2-inch, Mks I-III: The motor consists of a welded steel cylinder, to the head of which a threaded shell ring is attached by means of spring-locked pins which engage holes in the motor body. A venture tube is welded in the after end of the motor body. The tubular cordite grain is castellated at the forward end and rests in the motor body, supported by a metal grid at the after end. The propellant is initiated by an electric igniter placed in the castellations at the forward end. The tail orifice is sealed by a cardboard, plastic, or metal closing disc, and a silica gel bag is included as a moisture-proofing measure.
Electric leads from the igniter pass through the central channel of the cordite grain to the four brass contacts on the tail. These contacts, two positive and two negative, are so arranged that proper contact is maintained with the knife edges on the projector, regardless of the angle at which the round is loaded.
The motor is generally painted white or green overall, with identification markings stencilled on the outside. Proposed new nomenclature for the motors is as follows: Motor, Rocket, 2-inch, No.1 Mks I-III.
Remarks: These rounds must not be fired outside of the temperature ranges of 0 and 120 degrees Fahrenheit, unless filled with flashless cordite, which may be fired at temperatures between -5 and 130 degrees Fahrenheit.
3-in UP Anti-Aircraft Rocket (Service)
No.1 Mk I
Overall length: 14 inches
Diameter: 3.25 inches
Total weight: 17.75 pounds
Explosive: TNT
Explosive weight: 4.28 pounds
Fuzes used: No.700 or No.701
No.2 Mk I
Overall length: 9.29 inches
Diameter: 3.25 inches
Total weight: 7.6 pounds
Explosive: TNT
Explosive weight: 2.125 pounds
Fuzes used: No.731
Overall length: 14 inches
Diameter: 3.25 inches
Total weight: 17.75 pounds
Explosive: TNT
Explosive weight: 4.28 pounds
Fuzes used: No.700 or No.701
No.2 Mk I
Overall length: 9.29 inches
Diameter: 3.25 inches
Total weight: 7.6 pounds
Explosive: TNT
Explosive weight: 2.125 pounds
Fuzes used: No.731
Rocket Motor Mk I
Overall length: 55.19 inches
Diameter: 3.25 inches
Width of fins: 3.5 inches
Total weight: 31.2 pounds
Propellant: Tubular cordite
Propellant weight: 12.7 pounds
Burning time: 1.6 seconds
Rocket Motor Mk II
Overall length: 55.19 inches
Diameter: 3.25 inches
Width of fins: 3.5 inches
Total weight: 31.5 pounds
Propellant: Cruciform cordite
Propellant weight: 13 pounds
Burning time: 2.25 seconds
Overall length: 55.19 inches
Diameter: 3.25 inches
Width of fins: 3.5 inches
Total weight: 31.2 pounds
Propellant: Tubular cordite
Propellant weight: 12.7 pounds
Burning time: 1.6 seconds
Rocket Motor Mk II
Overall length: 55.19 inches
Diameter: 3.25 inches
Width of fins: 3.5 inches
Total weight: 31.5 pounds
Propellant: Cruciform cordite
Propellant weight: 13 pounds
Burning time: 2.25 seconds
General: These rockets are designed for anti-aircraft purposes, and thus are always fitted with some type of aerial-burst fuzing.
Description
Shell, H.E., No.1 Mk I: This shell consists of a steel cylinder, reduced in diameter at the base and threaded externally to screw into the shell ring of the rocket motor. The forward end of the shell is threaded internally to receive the base of the Fuze No.731 or the adapter ring employed with the Fuze No.700. Held in the nose fuze cavity by a locking ring is an exploder container with a booster charge, consisting of a 26-dram CE pellet and a 4-ounce TNT pellet, separated by a felt disc. A Gaine, or Booster, No.13 Mk I is employed with fuzes used in this shell.
Shell, H.E., No.2 Mk I: This shell consists of a light steel ogive struck with a 30-inch radius. The after part of the shell body is reduced in diameter and threaded externally to screw into the shell ring of the rocket motor. An internally threaded fuze adapter is welded to the forward end of the shell body. A cardboard exploder container is inserted into the main explosive filler beneath the fuze adapter and contains a 12-dram CE booster pellet.
Tail, Propelling, U. 3-inch, Mks I and II: These motors are identical, except that the Mk I contains a tubular grain, while the Mk II grain is cruciform in shape. The motor body consists of a steel cylinder, slotted at the tail end to receive the four tail fins. A shell ring, fitted in the head end of the body, is internally threaded to receive the base of the shell, and has eight holes to correspond with those in the motor body. Locking pins, flanged on their inner ends, are inserted through these holes and are retained in position by two circular band springs. A copper- or cadmium-plated steel obturator is placed in the rear of the shell ring and is separated from the propellant grain by a cardboard disc and two cardboard washers.
The propellant grain is castellated at the forward end to receive the igniter, and a washer of dummy cordite, attached to the base of the grain, bears against the ring of the grid. Spacing discs and tabs are attached to the exterior of the cordite grain by a special cement.
The igniter consists of a 10-gram charge of magnesium with an electric squib enclosed in a paper tube. The insulated electric leads pass through the central channel of the cordite grain to the contacts at the after end of the motor body.
The tail obturator, positioned between the grid and the venturi tube, is made in the form of a steel cup with a central perforation. The steel venturi tube is attached to the motor body by screws and welding, and contains a small bag of silica gel as a moisture-proofing measure. The leads from the igniter are connected to the four contacts around the outside of the motor body, so positioned that they make contact with the knife edges on the launcher, regardless of the angle at which the rocket is loaded.
Though generally fin-stabilized, these rockets are sometimes fitted with narrow 3/4-in fins, stabilization being obtained by spiralling the rails on the inside of the launcher barrel.
Proposed new nomenclature for the rocket motors is as follows: Motor, Rocket, 3-inch, No.1 Mk I for Propelling Tail, Rocket, 3-inch, Mk I, and Motor, Rocket, 3-inch, No.2 Mk I for Propelling Tail, Rocket, 3-inch, Mk II.
Although originally designed for use in this assembly, the H.E. Shell No.2 Mk I has never been so employed.
Remarks: The shells are painted buff overall and carry a stencilled ring of red crosses 1/2-inch wide 1 inch behind the forward end of the shell body. A green band, upon which are stencilled in black the letters TNT, is located 4.5 inches behind the forward end of the shell. Complete identification, filling, and manufacturing information is stencilled in black on the shell body between these painted rings.
Description
Shell, H.E., No.1 Mk I: This shell consists of a steel cylinder, reduced in diameter at the base and threaded externally to screw into the shell ring of the rocket motor. The forward end of the shell is threaded internally to receive the base of the Fuze No.731 or the adapter ring employed with the Fuze No.700. Held in the nose fuze cavity by a locking ring is an exploder container with a booster charge, consisting of a 26-dram CE pellet and a 4-ounce TNT pellet, separated by a felt disc. A Gaine, or Booster, No.13 Mk I is employed with fuzes used in this shell.
Shell, H.E., No.2 Mk I: This shell consists of a light steel ogive struck with a 30-inch radius. The after part of the shell body is reduced in diameter and threaded externally to screw into the shell ring of the rocket motor. An internally threaded fuze adapter is welded to the forward end of the shell body. A cardboard exploder container is inserted into the main explosive filler beneath the fuze adapter and contains a 12-dram CE booster pellet.
Tail, Propelling, U. 3-inch, Mks I and II: These motors are identical, except that the Mk I contains a tubular grain, while the Mk II grain is cruciform in shape. The motor body consists of a steel cylinder, slotted at the tail end to receive the four tail fins. A shell ring, fitted in the head end of the body, is internally threaded to receive the base of the shell, and has eight holes to correspond with those in the motor body. Locking pins, flanged on their inner ends, are inserted through these holes and are retained in position by two circular band springs. A copper- or cadmium-plated steel obturator is placed in the rear of the shell ring and is separated from the propellant grain by a cardboard disc and two cardboard washers.
The propellant grain is castellated at the forward end to receive the igniter, and a washer of dummy cordite, attached to the base of the grain, bears against the ring of the grid. Spacing discs and tabs are attached to the exterior of the cordite grain by a special cement.
The igniter consists of a 10-gram charge of magnesium with an electric squib enclosed in a paper tube. The insulated electric leads pass through the central channel of the cordite grain to the contacts at the after end of the motor body.
The tail obturator, positioned between the grid and the venturi tube, is made in the form of a steel cup with a central perforation. The steel venturi tube is attached to the motor body by screws and welding, and contains a small bag of silica gel as a moisture-proofing measure. The leads from the igniter are connected to the four contacts around the outside of the motor body, so positioned that they make contact with the knife edges on the launcher, regardless of the angle at which the rocket is loaded.
Though generally fin-stabilized, these rockets are sometimes fitted with narrow 3/4-in fins, stabilization being obtained by spiralling the rails on the inside of the launcher barrel.
Proposed new nomenclature for the rocket motors is as follows: Motor, Rocket, 3-inch, No.1 Mk I for Propelling Tail, Rocket, 3-inch, Mk I, and Motor, Rocket, 3-inch, No.2 Mk I for Propelling Tail, Rocket, 3-inch, Mk II.
Although originally designed for use in this assembly, the H.E. Shell No.2 Mk I has never been so employed.
Remarks: The shells are painted buff overall and carry a stencilled ring of red crosses 1/2-inch wide 1 inch behind the forward end of the shell body. A green band, upon which are stencilled in black the letters TNT, is located 4.5 inches behind the forward end of the shell. Complete identification, filling, and manufacturing information is stencilled in black on the shell body between these painted rings.
3-in Assault Rocket, "Lilo" (Service)
No.5
Overall length: 14.25 inches
Diameter: 3.25 inches
Total weight: 21 pounds
Filling: TNT
Filling weight: 4 pounds
Fuzes used: No.297 Mk I
No.6
Overall length: 17.5 inches
Diameter: 6 inches
Total weight: 60 pounds
Filling: TNT
Filling weight: 16.75 pounds
Fuzes used: No.297 Mk I
Overall length: 14.25 inches
Diameter: 3.25 inches
Total weight: 21 pounds
Filling: TNT
Filling weight: 4 pounds
Fuzes used: No.297 Mk I
No.6
Overall length: 17.5 inches
Diameter: 6 inches
Total weight: 60 pounds
Filling: TNT
Filling weight: 16.75 pounds
Fuzes used: No.297 Mk I
Rocket Motor
Overall length: 34.6 inches
Diameter: 3.25 inches
Width of fins: 1.75 inches (approx.)
Total weight: 18.25 pounds
Propellant: Cog-shaped cordite
Propellant weight: 4.25 pounds
Burning time at 60 degrees Fahrenheit: 0.5 seconds
Overall length: 34.6 inches
Diameter: 3.25 inches
Width of fins: 1.75 inches (approx.)
Total weight: 18.25 pounds
Propellant: Cog-shaped cordite
Propellant weight: 4.25 pounds
Burning time at 60 degrees Fahrenheit: 0.5 seconds
General: This rocket is designed as a heavy offensive weapon for infantry use against lightly reinforced obstacles. Only small fins are provided on the rocket motor, so stabilization in flight has been achieved by incorporating spiral rails in the interior of the launcher body. The rocket is fired from a small portable launcher by means of a light dry-cell battery, a US Army 10 cap exploder, or a US Navy "Magnavox" firing key.
Description
Shell, H.E., 21-lb, No.5 Mk I: This shell of a steel cylinder closed at the forward end by a flat steel nose plug. The after end is externally threaded and reduced in diameter to screw into the shell ring of the rocket motor. A steel spigot is threaded into the after end of the shell body and contains the cordite filled auxiliary charge container. Separated from the auxiliary cordite charge by a thin steel plate are a small thermal unit and a gunpowder pellet. Beneath this pellet the base percussion Fuze No.297 Mk I is threaded directly into the shell body. A single CE exploder pellet is located beneath the fuze in a cardboard exploder container.
Shell, H.E., 60-lb, No.6 Mk I: The 60-lb shell contains a Fuze No.297 and an auxiliary charge container almost identical to that incorporated in the 21-lb shell. A slightly different spigot arrangement is employed, however, as the spigot itself is externally threaded for attachment to the shell ring of the rocket motor. The nose portion of the shell is ogival and threads into the cylindrical shell body portion.
Motor, Rocket, 3-inch, No.7 Mks I and II: The motor consists of a steel tube fitted with a shell ring at one end and at the other with a venturi tube. The threaded shell ring is held in position by eight locking pins engaged by a circular band spring.
The venturi is welded to the inside of the motor body. A steel grid, separated from the venturi tube by the tail obturator, supports the cog-shaped cordite propellant grain. A metal closing disc in the venturi tube supports the igniter leads, which terminate in a two-pronged plug. The after end of the venturi is sealed by a cardboard closing disc. The igniter leads extend from the plug through the central annulus of the propellant grain to the metal igniter housing, which contains a small electric squib surrounded by a charge of gunpowder. Behind the metal closing disc in the venturi is located a bag of silica gel as a moisture-proofing measure.
The four fins are assembled to the motor by engaging their hooks in the fin slots in the after end of the motor body and pressing home the locking catches on the fins. A 10-yard extension cable is provided with each motor for firing purposes, thus allowing personnel to take cover when firing occurs. The extension is plugged at one end and contains a two-hole socket at the other for attachment to the plug connected to the igniter leads of the motor.
The motor must not be fired outside the temperature range of -5 to 135 degrees Fahrenheit.
Remarks: The shells are painted buff overall, with a 1/2-inch red band around the nose and a 1-inch light green band around the body. On this latter band are stencilled in black the letters of the explosive filling. Two thin white bands are painted around the body on either side of the light green band.
Description
Shell, H.E., 21-lb, No.5 Mk I: This shell of a steel cylinder closed at the forward end by a flat steel nose plug. The after end is externally threaded and reduced in diameter to screw into the shell ring of the rocket motor. A steel spigot is threaded into the after end of the shell body and contains the cordite filled auxiliary charge container. Separated from the auxiliary cordite charge by a thin steel plate are a small thermal unit and a gunpowder pellet. Beneath this pellet the base percussion Fuze No.297 Mk I is threaded directly into the shell body. A single CE exploder pellet is located beneath the fuze in a cardboard exploder container.
Shell, H.E., 60-lb, No.6 Mk I: The 60-lb shell contains a Fuze No.297 and an auxiliary charge container almost identical to that incorporated in the 21-lb shell. A slightly different spigot arrangement is employed, however, as the spigot itself is externally threaded for attachment to the shell ring of the rocket motor. The nose portion of the shell is ogival and threads into the cylindrical shell body portion.
Motor, Rocket, 3-inch, No.7 Mks I and II: The motor consists of a steel tube fitted with a shell ring at one end and at the other with a venturi tube. The threaded shell ring is held in position by eight locking pins engaged by a circular band spring.
The venturi is welded to the inside of the motor body. A steel grid, separated from the venturi tube by the tail obturator, supports the cog-shaped cordite propellant grain. A metal closing disc in the venturi tube supports the igniter leads, which terminate in a two-pronged plug. The after end of the venturi is sealed by a cardboard closing disc. The igniter leads extend from the plug through the central annulus of the propellant grain to the metal igniter housing, which contains a small electric squib surrounded by a charge of gunpowder. Behind the metal closing disc in the venturi is located a bag of silica gel as a moisture-proofing measure.
The four fins are assembled to the motor by engaging their hooks in the fin slots in the after end of the motor body and pressing home the locking catches on the fins. A 10-yard extension cable is provided with each motor for firing purposes, thus allowing personnel to take cover when firing occurs. The extension is plugged at one end and contains a two-hole socket at the other for attachment to the plug connected to the igniter leads of the motor.
The motor must not be fired outside the temperature range of -5 to 135 degrees Fahrenheit.
Remarks: The shells are painted buff overall, with a 1/2-inch red band around the nose and a 1-inch light green band around the body. On this latter band are stencilled in black the letters of the explosive filling. Two thin white bands are painted around the body on either side of the light green band.
3-in Barrage Rocket, "Land Mattress" (Service)
H.E. Shell
Overall length: 14.75 inches
Diameter: 5 inches
Total weight: 34.25 pounds
Filling: Amatol 60/40 or 50/50
Fuzing: No.721 Mks II* and III, and No.725 Mk I
Overall length: 14.75 inches
Diameter: 5 inches
Total weight: 34.25 pounds
Filling: Amatol 60/40 or 50/50
Fuzing: No.721 Mks II* and III, and No.725 Mk I
Rocket Motor
Overall length: 55.19 inches
Diameter: 3.25 inches
Width of fins: 0.75 inches (approx.)
Total weight: 30 pounds
Propellant: Cruciform cordite
Propellant weight: 11.5 pounds
Burning time at 60 degrees Fahrenheit: 1.5 seconds
Overall length: 55.19 inches
Diameter: 3.25 inches
Width of fins: 0.75 inches (approx.)
Total weight: 30 pounds
Propellant: Cruciform cordite
Propellant weight: 11.5 pounds
Burning time at 60 degrees Fahrenheit: 1.5 seconds
General: The Land Mattress rocket is designed as a barrage rocket for land service use. The motor employed is an adaptation of a 3-inch aircraft rocket motor, the modification consisting of cutting down the tail fins. Loss of stabilization due to the reduced tail surfaces is regained by imparting a spin to the rocket with spiral rails in the barrel of the launcher.
Description
Shell, H.E., 29-lb, 3-inch, Mk I: This shell is a modification of the 29-lb H.E. shell used with the 5-inch barrage rocket. The modifications consist of a threaded adapter screwed to the spigot on the base plate of the shell. The adapter is externally threaded to screw into the shell ring of the 3-inch rocket motor. Further modification of the shell includes alteration of the exploder pocket to receive the larger booster assemble of the Fuze No.721. The shell is painted buff overall, with a 1/2-inch red band painted around the nose portion of the shell and a 1-inch green band painted around the shell body. On this band the initials of the type of filling used are stencilled in black.
Motor, Rocket, A/C, 3-inch, No.1 Mk III: The motor is identical to the Motor No.1 Mk II, except that a single-pronged plug has been substituted for the two-pin plug on the end of the igniter leads. The motor, when used with the Land Mattress rocket, employs tail fins of a reduced width instead of the standard 5-inch fins.
Remarks: A novel method of varying range is incorporated in this rocket. Two spoiler plates, which consist of metal discs with three equi-spaced, cut-out segments, are placed face to face and are fitted to a spoiler bush. The spoiler bush is a collar which fits over the top of the Fuze No.721 and is recessed so as not to foul the protruding ends of the fuze shear wire. The bush engages with the top cannelure of the fuze and is held attached to the fuze by a locking wire around the fuze body. The spoiler plates are secured to the spoler by a spring steel circlip, which engages a groove in the bush just above the spoiler plates. Four small holes are drilled in one segment of each plate. Range variations are obtained by varying the relative positions of the spoiler plates to give different areas of wind resistance. The setting given to the spoiler plates is maintained by passing a special locking pin through the aligned holes in the plates.
Three different sizes of spoiler plates may be used, the smallest of which is painted red on one side, the medium size, blue, and the largest, white.
Description
Shell, H.E., 29-lb, 3-inch, Mk I: This shell is a modification of the 29-lb H.E. shell used with the 5-inch barrage rocket. The modifications consist of a threaded adapter screwed to the spigot on the base plate of the shell. The adapter is externally threaded to screw into the shell ring of the 3-inch rocket motor. Further modification of the shell includes alteration of the exploder pocket to receive the larger booster assemble of the Fuze No.721. The shell is painted buff overall, with a 1/2-inch red band painted around the nose portion of the shell and a 1-inch green band painted around the shell body. On this band the initials of the type of filling used are stencilled in black.
Motor, Rocket, A/C, 3-inch, No.1 Mk III: The motor is identical to the Motor No.1 Mk II, except that a single-pronged plug has been substituted for the two-pin plug on the end of the igniter leads. The motor, when used with the Land Mattress rocket, employs tail fins of a reduced width instead of the standard 5-inch fins.
Remarks: A novel method of varying range is incorporated in this rocket. Two spoiler plates, which consist of metal discs with three equi-spaced, cut-out segments, are placed face to face and are fitted to a spoiler bush. The spoiler bush is a collar which fits over the top of the Fuze No.721 and is recessed so as not to foul the protruding ends of the fuze shear wire. The bush engages with the top cannelure of the fuze and is held attached to the fuze by a locking wire around the fuze body. The spoiler plates are secured to the spoler by a spring steel circlip, which engages a groove in the bush just above the spoiler plates. Four small holes are drilled in one segment of each plate. Range variations are obtained by varying the relative positions of the spoiler plates to give different areas of wind resistance. The setting given to the spoiler plates is maintained by passing a special locking pin through the aligned holes in the plates.
Three different sizes of spoiler plates may be used, the smallest of which is painted red on one side, the medium size, blue, and the largest, white.
Next Time: High Explosive Rockets Part 2
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