Monday, 15 January 2018

American Projectiles and Explosives - Navy Rockets (Part 2)

American Projectiles and Explosives

Navy Rockets

3.5-inch Window

Overall length: 45.1 inches (approx.)
Weight: 32 pounds

Head length: 23.2 inches
Head weight: 14.25 pounds (loaded)
Motor length: 23 inches
Motor diameter: 3.25 inches
Width of tail fins: 9.2 inches
Length of tail fins: 8 inches

Fuze: Base Fuze Mk 134

General: The window rocket is designed to be fire from Naval vessels equipped with a modification of the present shipboard launcher.  The round carries a payload of paper-coated metal foil strips which are scattered in the air by a delayed-action charge.  The payload is ejected at an altitude of 1,200 feet and range of 2,000 yards at 40 degrees of elevation.

Description: The window rocket consists of a 3.5-inch Rocket Head Mk 10, Mk 14 Mod 0, or Mk 15 Mod 0 and a 3.25-inch Rocket Motor Mk 12 Mod 0, Mk 14 Mod 0, or Mk 14 Mod 1.  The motor uses the propellent grain Mk 7 Mod 1, weighing 2.8 pounds.

The rocket head contains a 3.5-inch rocket-head load - Mk 2, Mk 3, Mk 4, Mk 5, or Mk 8 - which is housed in a split steel ejection liner.  It has a closure adapter on the after end, an obturator cup for sealing the front end, and a solid wood ogive cap retained by three aluminum rivets in the Mk 10, hollow-steel friction fit in the Mk 14 and Mk 15.  The closure adapter, which is welded to the after end, carries a copper diaphragm plate with a firing pin, and also serves as a chamber for the Cal. 32 blank cartridge which ignites the fuze.  The Fuze Mk 134 consists of a plastic case containing a length of Ensign Bickford fuze and a 20-gram ejector charge of black powder.

All strips are 3/16 inches wide and 0.008 inches thick except the Mk 9, which are 1/2 inch wide.

Operation: When the rocket is fired, gas pressure blows out the forward closure disc of the motor and exerts force on the diaphragm plate in the base of the motor adapter.  The diaphragm collapses, and the firing pin is forced into the primer, firing the blank cartridge. The flash from the cartridge ignites the fuze, which burns for 15 seconds and then ignites the black powder ejection charge.  The firing of the ejector charge forces off the ogive cap and pushes the load forward out of the head.  The strips are then dispersed.

Remarks: The Motors Mk 12 Mod 0 and Mk 14 Mod 0 carry adjustable lug bands; the lugs are welded to the Motor Mk 14 Mod 1.  The Mk 14 Mod 0 and Mk 14 Mod 1 have a metal base cap during shipping, to protect the electrical connector.

The head Mk 15 Mod 0 is one inch longer than the Head Mk 14 Mod 0

3.5-inch Flare

Overall length: 47 inches (approx.)
Weight: 33.5 pounds

Head length: 23 inches
Head weight: 16.5 pound
Motor length: 24.5 inches
Motor diameter: 3.25 inches

Fuze (Head Mk 14): Base Fuze Mk 134
Fuze (Head Mk 15): Base Fuze Mk 128

General: The 3.5-inch rocket flare was developed for use from surface ships, particularly motor torpedo boats.  The illuminant candle produces an average of 800,000 candle power for approximately twenty-nine seconds.  The rocket motor carries the flare out 1,800 yards before ignition.

The flare consists of the following major components: 3.25-inch Motor Mk 12 Mod 0, Mk 14 Mod 0, or Mk 14 Mod 1; 3.5-inch Head Mk 10 Mod 0, Mk 14 Mod 0, or Mk 15 Mod 0; and Body Load (Flare) Mk 7 Mod 0.

Head: All the heads are interchangeable and differ only in minor details.  The 3.5-inch Head Mk 10 Mod 0 has a wooden nose piece held in place by three shear pins, while the Mk 14 Mod 0 and Mk 15 Mod 0 have a sheet-metal nose piece press-fitted in place.  The Mk 15 Mod 0 is one inch longer than the other two.

The head consists of a 3.25-inch seamless steel tube which incorporates a 3.5-inch diameter closure adapter welded to the after end.  This closure adapter carries a copper diaphragm plate with a firing pin, and serves as a chamber for the caliber .32 blank cartridge which ignites the fuze.  The balance of the head is taken up by the candle and parachute from the 4-inch illuminating projectile, the composition of the candle slightly changed to increase the candle power in the shorter burning time.

Motors: The three motors are similar and interchangeable.  The principal distinguishing feature of the 3.25-inch Motor Mk 14 Mod 1 is the use of welded-on launcher lugs replacing the lug bands employed on the earlier models.  The motor housing is a 3.25-inch seamless steel tube containing a forward closure disc, Igniter Mk 11 Mod 0, Tubular Ballistite Grain Mk 7 Mod 1 (2.8 pounds), steel grid, welded nozzle, and pigtail.  Four tail fins, three inches by eight inches, are mounted on a sleeve fixed to the after end.  A thread projector on the forward end and shipping cover taped on the after end protect the motor in shipment.  The 3.25-inch Motor Mk 12 Mod 0 does not have a shipping cover on the after end.

3.5-inch and 5-inch A.R. with 3.25-inch Motors

General: The 3.5-inch rockets were designed to be used against smaller targets, such as submarines and tanks.  For larger targets, the 5-inch rocket was developed from the 5-inch anti-aircraft shell.  The 3.5-inch Solid Head Mk 8 and the 3.5-inch F.S. and P.W.P. Smoke-filled Heads Mk 6 are the only ones now being issued.  The 3.5-inch H.E. heads were replaced by the 5-inch heads.  The former were never issued, because of the small load of TNT carried, as compared to the 5-inch heads.


3.5-inch Mks 1 and 2: The head is of solid steel and contains no high explosive or fuze.  The shape of the round gives a relatively long underwater travel at shallow depth-of-entry angles (about 20 degrees), and it is used as a semi-armor-piercing projectile against submarines or tanks.  The Mk 1 was the California Institute of Technology production which was adopted by Bureau of Ordnance and designated the Mk 2.

3.5-inch Mks 3 and 5: The head is filled with TNT and fitted with an adapter in the nose to take the Fuze Mk 149.  With a second adapter, the diameter is reduced to 1.5 inches to take the Fuze Mk 148.  These rounds were not issued and were replaced by the 5-inch heads, which contain a greater load of high explosive.

3.5-inch Mk 4: The head has a semi-armor-piercing nose and is filled with TNT.  This round was not issued, because of the small load of high explosive, and was replaced by the 5-inch heads.


3.5-inch Mks 6 and 9: The head is filled with F.S. or P.W.P. smoke.  The Mk 9, the initial California Institute of Technology production, was not issued.  The Bureau of Ordnance, in adopting this head, increased the length 1-1/2 inches and issued the round as the Mk 6.

3.5-inch Mk 8: The head is of solid steel and contains no high explosive or fuze.  The round was developed to give better underwater travel and replaces the 3.5-inch Head Mk 2.

5-inch Mk 1 Mod 0: The head is filled with TNT and weighs 46.5 pounds when fitted with a Fuze Mk 143.  The same adapter rings are used as on the 3.5-inch Head Mk 5.  The head is issued with a nose plug.  The nose fuze must always be assembled in the head before firing.  Fire with the fuze on "safe" if delay is desired.  The head is shipped with the base fuze sealed in place.  This base fuze must not be removed.

5-inch Mk 1 Mod 1: This head differs from the 5-inch Head Mk 1 Mod 0 only in that the nose is especially cavitated to take the Fuze Mk 172 Mod 0, which is larger than the Mk 149 or other nose fuzes and therefore is not interchangeable with them.


The 3.25-inch Motor Mk 7 is used with the 3.5- and 5-inch heads described above.  At the forward end of the motor are a black-powder igniter and an electric squib.  Two electric leads extend through the motor and out the after end to a cable and plug connection.  At the after end of the motor, there are a nozzle and a bag of silica gel which acts as a dehydrating agent in keeping moisture from the ballistite grain.  The grain used in the cruciform type with inhibitors, 33 inches long, 2.75 inches in diameter, and weighing 8.5 pounds.

The tail consists of four sheet-metal fins set 90 degrees apart and welded to a central cylinder.  The tail is slipped over the after end of the motor and is secured by a tail locking ring, which screws on.

Remarks: The 3.5-inch (H.E. and F.S.) have a maximum velocity of 1,200 feet/sec exclusive of plane speed, as compared to 800 feet/sec for the 5-inch H.E.

The 3.5-inch Heads Mk 11, incendiary, and Mk 12, gas, were never loaded.

Next Time: Navy Rockets (Part 3)

Monday, 8 January 2018

American Projectiles and Explosives - Rocket Bodies, and Navy Rockets (Part 1)

American Projectiles and Explosives

Rocket Bodies Introduction


 The propelling unit of the rocket is called the motor and contains the propelling charge.  The motor is attached to the head, which contains the payload and the initiating device.  The motor is closed on the forward end and partially opened at the after end.  The propellant is a relatively slow-burning double-base smokeless powder called ballistite.

As the ballistite is burned, hot gases are generated which expand and exert pressure against the confines of the motor tube.  Since the hot gases exert an equal pressure in all directions, the pressures against the side walls counter-balance each other; however, the pressure against the forward closed end of the tube is not counteracted by pressure against the after end since that end is partially open.  The resultant force, then, is a thrust against the closed forward end of the motor, and the rocket is propelled in that direction.  In order that the pressure of the gases will not be expended too rapidly, and that the propellant can be retained in flight, the after end of the motor tube is partially closed by the nozzle attachment, which is built into the inside of the tube.  This nozzle restricts the ejection of the hot gases and also, by means of its rear taper, furnishes a canted surface against which the rapidly expanding emitted gases may act to increase the forward thrust of the rocket.

The ballistite propellant is ignited by a black-powder charge, the initiating device for which is an electric squib with a small bridge wire of high resistance which, when heated by an electrical current, ignites a violent match composition.  The black powder charge sends a flash over the entire surface of the ballistite to the ignition point.  Upon ignition, the ballistite burns evenly and relatively slowly; this type of burning is necessary to prevent sudden and excessive pressures being exerted against the thin walls of the motor tube.  Rocket motors operate at much lower pressures than guns, and correspondingly longer times are required for the complete combustion of the rocket propellant.  Burning times of American rockets range from about 0.15 seconds to as much as 1.5 seconds, depending on the web thickness of the grain and the temperature of the propellant; and burning distances range from a few feet to several hundred feet at high velocities; hence, most of the burning of the rocket propellant occurs after the projectile has left the launcher.

The early productions of rockets were of the fin-stabilized type because of their use by the British and because of the inherent simplicity associated with fin stabilization.  Rockets cannot be launched with that degree of accuracy characteristic of gun projectiles.  This is a result of many factors, such as the effect of temperature on the burning rate of the propellant, difficulties in controlling to a fine degree the pressures exerted by the expanding gases inside the motor tube, the effect of the expansion of emitted gases against the rear taper of the nozzle, etc.  The mean deviation in deflection for most standard land- or shipboard-launched fin-stabilized rockets is 20 to 40 mils, while fin-stabilized rockets launched from aircraft have a mean deviation of about 5 to 10 mils.  The increased accuracy of aircraft-launched rockets is attributed to the immediate stabilizing effects given to the fins during the initial stages of flight by the rapid travel of the plane through the air.  Fins on rockets exert an appreciable restoring force in flight only at a high velocity, and thus a greater degree of accuracy is achieved if rockets are launched from aircraft or if the acceleration occurs to a large extent on the launcher.

A later development, the spin-stabilized rocket, is now in service use.  Stabilization of this rocket depends on the rotation of the round.  Although the accuracy of spin-stabilized rockets is not comparable to that of gun projectiles, they are generally more accurate than fin-stabilized rockets at short ranges.  The use of spin-stabilized rockets will be particularly advantageous to ground and amphibious forces, inasmuch as the rocket is shorter and the launching gear is more compact, facts which facilitate the loading and stowage problems.

As against their disadvantages, rockets have many advantages over gun-propelled projectiles.  The most important is the absence of recoil against the launcher.  Since there is no recoil action on the launcher, rockets may be launched from small trucks, amphibious ships, and aircraft which could not withstand the recoil forces exerted by equivalent projectiles fired from guns.  Other advantages of rockets are cheapness, simplicity, and portability of the launchers as compared to guns.


Head: This is the part which is functionally similar to a projectile and which contains the payload and the initiating device.  This payload may be solid shot, high explosive, chemical, incendiary, window, flare, or a special load.

Motor Tube: This contains the propelling charge and the igniter.  It is a combustion chamber in which the propellant is burned to provide the motive power for the rocket.  It generally threads to the rocket head and is usually shipped separate from the head and fuze.  The diameter of the motor is generally less than the diameter of the body with which it is used.

Grid or Trap assembly: The Navy refers to the assembly which supports the powder grain as the grid.  This grid supports the grain in such a position that sufficient clearance is allowed between the grain and the motor tube to allow the gas to flow from the propellant to the nozzle.  The Army uses a trap assembly, which is somewhat more complicated than the Navy grid.  The trap assembly consists of spacing discs and wires running between them, on which the sticks of ballistite are supported.  Such an assembly is necessary where numerous small grains are used.

Nozzle: The number of nozzles varies with the type of motor and method of stabilization.  The nozzle has several functions.  It directs the gas jet in the desired direction and provides for expansion of the hot gas in the exit cone, thus giving additional thrust (about 33%) over the obtainable from a simple orifice.  In spin-stabilized rockets, it imparts a clockwise rotation tot he rocket when launched.

Fins: During burning, the action of the air against the fins gives a restoring moment against side forces at the nozzle, thus improving the accuracy of fire.  When there is a tail shroud, it supports the rear end of the rocket in the launcher and may also provide electrical contacts for firing.

Propellant and igniter: The igniter contains loosely packed black powder and an electric squib with a high-resistance bridge running through a match composition.  The propellant is a double-base smokeless powder called ballistite, which burns slowly and uniformly.  Production of ballistite differs somewhat for the Army and the Navy, the Army preferring the solvent extrusion process and the Navy specifying the solventless extrusion process.  The solvent extrusion process is impractical for grains having a web of more than 1-1/4 inches.

Grain shapes also vary.  Army rockets generally have several small cylindrical grains of ballistite, with an axial hole to increase the burning surface and uniformity of burning.  The Navy rockets use either a single solid cruciform grain without perforation or a single cylindrical grain with an axial hole and radial perforations.  The latter, used in Navy ground- or shipboard-mounted rockets, is characterized by three ridges 120 degrees removed and running longitudinally along the grain.  Inhibitors are not used on this type.  The cruciform grain, in Navy aircraft rockets, is a symmetrical cross with rounded ends.  If all the exterior surface of this grain were permitted to burn, there would be a gradual decrease of area, and a regressive rate in burning.  Hence, a number of slower burning cellulose acetate strips are bonded to parts of the area exposed on the outer curved ends of the arms, to give desired burning characteristics.

Storage:  To decrease hazards in handling, rocket bodies and motors are generally shipped and stored separately.  Motors with large grains are kept in a non-propulsive state until final assembly is necessary.  The seals at both ends of the motors are light and easily displaced by pressure developed inside the tube.  Should the igniter and grain igniter, the closures would fail quickly, relieving the pressure without more than a slight movement of the motor.

It is necessary that loaded motors be kept at moderate temperatures as much as possible.  Event hough spontaneous ignition should not take place, the powder should not be stored where temperatures exceed 100 degrees Fahrenheit, because such conditions tend markedly to decrease the stable life of the propellant.  Because of the electric squib, rocket motors should not be stored near radio apparatus or antenna leads.

Although there is very little possibility of a motor firing as a result of falling or rough handling, such treatment is likely to cause malfunctioning of the rounds.  Ammunition should be kept in packing containers or ready boxes and should not be handled in a loose condition unless necessary.

Practice Rockets

Practice rockets are loaded with plaster of paris or other inert substances to simulate the explosive loads in service rounds.  These rockets also have dummy fuzes.

Safe Temperatures

The burning rate of propellent powders changes with temperature and pressure - the higher temperatures and pressures causing more rapid burning.  If rockets are fired at temperatures higher than those for which they are designed, the pressure may build up faster than the nozzle can release it, perhaps bursting the round.  At temperatures below the safety limit, there will be back blasts of flame with burning fragments of powder.

Retro Rocket

These were rockets designed to be fired aft from a fast moving ship or plane - the movement aft to compensate exactly for the movement forward of the launching vehicle, thus leaving gravity as the only effective force on the rocket.

2.25-inch A.R. Practice

General: The 2.25-inch sub-caliber rocket rocket for aircraft was developed for training purposes.  Initially, two types were designed to approximate the trajectory of the 3.5-inch and 5-inch rockets; however, only the Motor Mk 11 and the Head Mk 3 Mod 2 will be used in future training.

The Mk 1, a California Institute of Technology production, was issued until adopted and issued by Bureau of Ordnance as the Mk 3 Mod 2.  The Mk 2, a California Institute of Technology production, was designed as a slow sub-caliber rocket.  The complete assembly for the latter is no longer available.

The 2.25-inch Motors Mk 10 and Mk 11 are similar to each other, as are the 2.25-inch Motors Mk 12 and Mk 13.  The Motors Mk 10 and Mk 11 differ from the Mk 12 and Mk 13 in that the diameter of the nozzle on the latter is smaller and the weight of the propellant of the Mk 10 and the Mk 11 is 1.75 pounds, as compared to the weight of 1.12 pounds in the Mk 12 and Mk 13.

The external dimensions of the rockets are the same.  For recognition purposes, the 2.25-inch motors Mk 10 and Mk 11 are painted white with black fins, while the Motors Mk 12 and Mk 13 are grey with black fins.

Motor Mk 11 and Head Mk 3 Mod 2: Overall length of the rocket is 29 inches.  Two button-type lugs are provided ont he motor tube, spaced approximately 19 inches apart.  Four fins are welded to the after end of the motor tube.  The propellant is a cylindrical grain of ballistite weighing approximately 1-3/4 pounds.

3.25-inch Targets

General: As a target for anti-aircraft gunners, the rocket is projected with speeds approximating those of an aircraft.  It consists of a rocket propulsive unit to which are attached large stabilizing fins, for maximum visibility.  They all consist of a simple rocket motor with three large fins prepared from wooden frames and light-weight fiber board.  The fins are 120 degrees apart, each attached by two lugs.

The 3.25-inch Rocket Targets Mk 1 and Mk 2 consist of a motor 36 inches long, to which fins 18 inches by 34 inches are attached.  An electrical connection is made by a standard 110-volt plug.  The 3.25-inch Target Rocket Mk 1 is standardized at 425 mph and the Mk 2 at 300 mph.  On some models, a screamer is put over the nose end.

The Mks 3 and 4 differ from the Mks 1 and 2 in that the motor is heavier and the fins are held on by threaded studs instead of lugs.  The ballistics are similar; Mk 3 is like Mk 1, and Mk 4 is like Mk 2.

Next Time: Navy Rockets (Part 2)

Sunday, 31 December 2017

American Projectiles and Explosives - Army Developmental Types

American Projectiles and Explosives

Army Developmental Rockets

2.36-inch Smoke T-27E1

No picture available

Overall length: 16.1 inches
Total weight: 3.4 pounds
Head length: 4.5 inches
H.C. smoke charge: 1 pound

General: This rocket is generally similar to the other smoke rockets in this series, differing mainly in its payload.  It also differs in that it has a circle of smoke ports in the base of the head, which allows the H.C. smoke to be blown out of the head on impact.  Pressure of the H.C. smoke blows out the port covers after the base fuze sets off the H.C. gas.  The H.C. smoke will issue for one minute after impact.

2.36-inch Incendiary T3

No picture available

Overall length: 17.7 inches
Total weight: 3.4 pounds
Head length: 4.1 inches
Thermite filler: 1.1 pounds

General: The T31 is like the other 2.36-inch chemical load rockets, using the same motor and fuzing as the M10.  It has, however, a mmuch shorter head.  On impact, it ignites and burns, producing extreme heat.  It is currently issued for practice only.

4.5-inch H.E. S.S. T22 and Practice T46

No picture available

General: These rockets have the heavier shell of the M8A2 and M9A2.  Also, the motor tube is further strengthened and the assembly of the fins slightly changed.  The igniter is loaded in a tube attached to the trap, extending the length of the propellant charge.  Its safe temperature range: -20 to +120 degrees Fahrenheit.

3.5-inch A/T T80 and Practice T85

Overall length: 26.3 inches
Weight of head: 5.11 pounds
65/35 Cyclotal charge: 1.82 pounds
Length of motor: 15.6 inches

Fuzing: T160E1

General: This design is mainly a larger type of the 2.36-inch A/T model, with improvements.  It has the shaped-charge explosive for penetration.  It also has a more efficient propellant and an all-ways-action fuze.  Performance tests are still being conducted.  It is the largest of the shoulder-fired rockets.

Propellant: There are 12 sticks of powder five inches long and 0.375 inches in diameter; total weight, 160 grams.  The igniter is conventional.

4.5-inch H.E. A.R. T83 and Practice T87

Overall length: 75.88 inches
Total weight: 98 pounds
Head length: 16.68 inches
Weight of charge: 8.8 pounds
Range: 1,500 yards

Fuzing: Mk 149

General: This is one of the "fixed-fin" type of 4.5-inch rockets, the other being the S.A.P. round.  It is a high-velocity rocket, fired from the zero-length launchers.

Head: The high-explosive head T2002 is thin-walled and has an adapter and fuze-seat liner for the Nose Fuze Mk 149.  An Auxiliary Booster Mk 3 Mod 1 is shipped in the fuze seat, protected by a chipboard disc and a shipping plug.

Motor: The T2000 motor is connected to the head by a steel coupling, threaded internally.  The motor tube is constricted at the rear to form the nozzle.  Lug bands are one button-type band and one zero-length band, 45.53 inches and 10.25 inches respectively, from the base of the rocket.

Tail: The T2000 tail assembly, four flat fins mounted radially on a metal sleeve, is secured to the nozzle by a threaded retainer coupling.

Propellant: Twelve single-perforated sticks of powder having 7/16-inches inside diameter and 1.22 inches outside diameter, 20.6 inches long, are mounted in two banks of six each on the bars of a cage-like support.

Igniter: An electric squib and 2 and 3/4 ounces of black powder are assembled in a plastic tube 6 and 3/4 inches long and one inch in diameter.   This tube is suspended from the end of the propellant in the center of the tube.  The ignition wires pass to the rear through a plastic closing cap cemented in the throat of the nozzle.  They terminate in a phone-type plug.  About two feet of igniter cable are held in the flare of the nozzle by a fiber cap cemented in place.

Practice Round: The T87 - T2003 head and T2000 motor - is like the T83 except for the live fuze and explosives, for which inert substitutes are provided.

4.5-inch S.A.P. A.R. T78 and Practice T86

No picture available

Overall length: 70.89 inches
Total weight: 98 pounds
Head length: 15 inches
Weight of charge: 2.8 pounds
Range: 1,500 yards

Fuzing: T156

General: This is another "fixed-fin" 4.5-inch rocket.  A high-velocity aircraft rocket, it is fired from the zero-length launchers.

Head: This S.A.P. Head T2000 is of heavy-walled construction and threaded at the base to receive the motor tube.

Motor: This round uses the same motor and fin assembly as are found on the T83 round.  It also uses the same propellant and igniter.  The Practice Round T86, T2001 Head, is inert fuzed and loaded.

4.5-inch H.E. S.S. T160 and Practice T161

Overall length (w/o fuze): 30.07 inches
TNT charge: 6 pounds

Fuzing: M81 or M402 (V.T.)

General: Because of its more efficient propellant, this round is expected to be a more powerful, longer-range rocket.  Except for the propellant, it is of conventional Army design.

Propellant: Seven cylindrical powder sticks, 13.5 inches long and 1.35 inches in diameter, furnish the power.  The grid type of support is used instead of the conventional trap, and the igniter is housed against the motor wall, instead of being placed in the center.  Safe temperature limits for this round are from -20 to +120 degrees Fahrenheit.

7.2-inch H.E. T24

See Navy 7.2-inch chemical warfare rocket

7.2-inch D.R. T37 and T88

See Navy 7.2-inch demolition rocket

8-inch D.R. T25

No picture available

Overall length: 60.25 inches
Total weight: 137 pounds
Head length: 27.5 inches

Filler: TNT or 50/50 Amatol
Weight of filler: 58 pounds
Range: 550 yards

Fuzing: T20

General: This round is a modified 100-pound G.P. bomb fastened to a 4.5-inch rocket motor.

Construction: Suspension lugs and base plug are removed from the standard 100-pound bomb, and a motor adapter substituted for the base plug.  The motor is the standard type for the 4.5-inch Army folding-fin type of rocket, modified to take the special box-type fin.  The fuze seat in the bomb is modified to receive the Point Detonating Fuze T20.

Launcher: The metal crate in which the round is shipped serves as an expendable launcher.

H.E. S.S. 21-cm T36 and Practice T45

Overall length: 48.86 inches
Total weight: 91.75 pounds

Fuzing: M51 (M81)

General: This round is a copy of the German rocket of the same type.  At present, performance tests are being conducted by the Army Ordnance Department.  It is of conventional structure, with the artillery-type fuze.

Next Time: Rocket Bodies, and Navy Rockets (Part 1)

Monday, 18 December 2017

American Projectiles and Explosives - Rocket Projectiles

American Projectiles and Explosives

Army Rockets

2.36-inch A/T

Service: M6A1, M6A3, M6A4, M6A5
Practice: M7A1, M7A3, M7A4, M7A6
M6A1 and M6A3 Data

Overall length: 21.6 inches
Total weight: M6A1 - 3.4 pounds; M6A3 - 19.4 pounds
Head length: 8.6 inches
Body length: 4.11 inches
Body diameter: 2.23 inches
Body wall thickness: 0.087 inches

Ogive length:
-M6A3 (Cone-Shaped): 4.5 inches
-M6A3 (Hemispherical): 4.56 inches

Ogive diameter (at flange): 2.245 inches
Motor tube length: 6.32 inches
Motor tube (inner diameter): 1.06 inches
Motor tube wall thickness: 0.095 inches

Maximum range: 700 yards
Effective range: 300 yards
Muzzle velocity: 265 feet/sec

Color: Olive drab

Explosive: Pentolite

General: Pill boxes, tanks, and armored vehicles are prime targets.  The rocket can also be used in a stationary emplacement for demolition or as an anti-tank mine or a booby trap.  The rocket can penetrate three inches of homogeneous steel armor plate at all ranges and at angles of impact as low as 30 degrees, employing the shaped-charge explosive.

Launcher: The Rocket Launcher M1A1, commonly called the "bazooka", is an electrically operated weapon of the open-tube type, fired from the shoulder, and weighing 13.26 pounds.  Rocket Launcher M9A1 is similar but breaks down into two sections, each 31 inches long, for ease in transporting.

Construction: The 2.36-inch A/T Rockets M6A1 and M6A3 are identical except for difference in the ogive and the tail assembly.  In other respects the two rockets are similar, consisting of a hollow ogive crimped onto the body, a body union fitting into the base of the body with internal threads to receive the motor, and a fuze which is located in the forward end of the motor tube.  The M6A1 has a conical ogive, whereas the M6A3 has a hemispherical ogive which gives better penetration by forming a stronger stand-off piece for the shaped-charged effect of the explosive.  M6A4 is like the M6A3, except that it is lighter, being made of high-strength alloys, and also uses the Bore-Safe Fuze M400.  The M6A5 uses the Bore-Safe Fuze M401 and has a larger propellant grain, which eliminates the safety disk.

Tail Assembly:  The M6A1 has six fins (5 and 1/2 inches long) spot-welded to the nozzle, a steel cup internally threaded at the forward end to screw onto the motor tube.  The M6A3 has a different type of tail assembly to obtain fin area and counteract the change of the center of gravity effected by the hemispherical nose.  This tail assembly consists of four sheet-steel fins 2 and 5/16 inches long, each of which is curved over an arc of 90 degrees on its outboard edge to form a blade.  Each fin is joined to the other by welding, with an overlap of approximately a 1/2 inch to form a circular drum which is actually nothing more than a continuation of the four fins.  The bases of the fins are spot-welded to the nozzle.  In the M6A5 and M7A6 the free end of the ignition wire is attached to the shroud tail by a chip-board disk, instead of the tape on earlier models.

Propellant: The propellant consists of five sticks of ballistite.  On an average, the propellant weighs approximately 61 and 1/2 grams, though it is loaded not by weight but rather by length of powder stick, to keep the pressure for various rounds at a relatively constant value.  The M6A4 and M6A5 use the Powder M7, which burns at a lower temperature, +120 to -40 degrees Fahrenheit.

Fuze: The fuze for the M6A1 and M6A3 consists of a steel firing pin which slips into the central cavity of the fuze body, where it is held in a rearward position by the firing pin spring.  A circumferential groove midway down the length of the firing pin receives the safety pin, which extends through the motor tube.  When the safety pin is removed, the firing pin is free to move forward, restrained only by the action of the firing pin spring.  After the safety pin has been removed, the firing pin will overcome the spring and detonate the rocket if it is dropped over four feet.  The fuze body contains the Detonator M18 of lead azide and tetryl, and the booster charge of tetryl.

Remarks: The practice rounds are similar to their accompanying service rounds, except that they are inert-loaded and have a dummy fuze or steel weight to fill the empty fuze space.

The M6A5 and M7A6 have plastic closing plugs, making them waterproof rounds.  They also use the Powder M7, which burns at a lower temperature, +120 to -40 degrees Faherenheit.

The M6A1 and M7A1 are now considered obsolete.

2.36-inch Smoke (W.P.) M10, M10A1, M10A2, M10A3

M10 Data

Overall length: 17.1 inches
Total weight: 3.4 pounds
Head length: 5 and 1/2 inches
Head diameter: 2.3 inches
Maximum diameter: 2.36 inches

W.P. charge: 405 grams
Burster charge: 4 grams
Effective range: 300 yards

-Motor: Olive drab
-Head: Blue grey

General: This rocket is designed not only as a screening agent, but also to cause casualties.  White phosphorus in smoke form has little effect upon the human body, but particles cause small burns.  This rocket makes an effective weapon for dislodging enemy troops from dug-outs and foxholes.

Launcher: The 2.36-inch Smoke Rocket M10 is fired from the Launcher M1A1 or M9, the "bazooka".

Construction: The components of this rocket are the motor and the head assembly.  The motor presently used is the M6A1, which is being replaced by the M6A3.  As new motors are developed, it is contemplated that this rocket will be modified.

The head assembly consists of a container for the smoke charge with a long burster well containing PETN inserted from its after end.  A collar is soldered to the base of the container.  The spacer slips over the threads of the collar and is held against the flat surfaces of the collar by the fuze body, forming a joint between the two.  The primer holder is threaded into the fuze body.

Tail Assembly:  The 2.36-inch Smoke Rocket M10 has the standard tail assembly for this M6A1 or M6A3 motors.

Fuze: The fuze is similar to that used in the A/T Rocket M6A3.

Remarks: The M10A1 and M10A2 differ from the M10 in the type of propellant used.  The M10A1 used the T1E1 Salted Powder, with a temperature range of 120 to -20 degrees Fahrenheit.  The M10A2 uses the Powder M7, 120 to -40 degrees Fahrenheit.  The M10A3 differs from the M10A2 in that it uses the Fuze M401.

3.25-inch Target M2, M2A1, M2A2

Overall length: 59 inches
Width across fins: 24 inches
Weight: 37.5 pounds
Propellant weight: 3.2 inches

Range: 1,700 yards
Maximum velocity: 530 feet/sec
Burning time of flare: 30 seconds

General: This is a high-speed target for firing practice with automatic A.A. weapons.

Propellant: The propellant has grains five inches long and 7/8-inch in diameter, with a 5/16-inch axial hole.  It is ignited by an electric squib.

M2A1: When a flare is added to the 3.25-inch Target Rocket M2 for anti-aircraft target practice at night, the resulting projectile is designated as the M2A1.  The flare burns for 30 seconds from the beginning of flight.

M2A2: This design has a flat nose, to which is threaded a yellow flare for both day and night tracking.  It also has a different system for igniter contact: the lead wires pass in turn through the nozzle and an inner fiber closing cup and connect to a household-type service plug, which is held by an outer fiber-board closing cup.  There are 18 inches of igniter cable coiled between the closing cups, to allow ample lead for connecting to the launcher.

4.5-inch H.E. M8, M8A1, M8A2, and M8A3; also Practice M9, M9A1, M9A2, and M9A3

Overall length: 33 inches
Total weight: 38 pounds
Head length: 7.5 inches
Wall thickness: 0.2 inches

Burster tube length: 15.5 inches
Fin length: 4 and 1/3 inches
Bursting charge weight (TNT): 4.3 pounds
Maximum range: 4,500 yards
Muzzle velocity: 840 feet/sec

Fuzing: M4, M4A1, M4A2

General: The initial issue of the rocket went to the Army Air Forces for projection from aircraft launchers against ground targets; but, in-asmuch as the rocket was originally designed for use from ground launchers, its use in aircraft has been discontinued.

Construction: The head is a thin-walled high-capacity type, rounded at the nose to form the ogive, threaded at the nose to take the fuze adapter, and threaded externally aft to fit into the motor.  A burster tube is fitted to the head and extends down into the motor, a design which utilizes the motor tube for additional fragments, since the burster tube as well as the head itself is loaded with TNT.

The motor is a steel tube of uniform diameter except at the after end, where it constricts and then flares to form the nozzle.  The motor houses the trap assembly, which consists of ten wires running from the trap plate on the forward end to the trap ring on the after end.  The trap assembly holds the thirty sticks of propellant and fits around the burster tube.  The motor tube is threaded internally forward to take the head, and just abaft this thread is a groove which weakens the tube to provide a safety shear point, should the motor pressure become too great.

The fin assembly for the rocket opens and guides the rocket in flight only after the rocket has cleared the launcher.  The fins of the assembly are held in place by the fin retainer, which is expelled by the blast of the escaping gas.  After clearing the launcher, the fins snap to their outstretched position.  There are six fins.

The M8A1 involved a change in the design of the motor tube to strengthen it on the threaded end.  The head of the M8 was used by machining new base threads.  Tests on the M8A1 indicated that the base of the modified head was weak, and a new head was designed for use with the motor of the M8A1.  This rocket, the M8A2, will suspersede the M8 and M8A1.  The M8A3 is a modification of the M8A2 made by the addition of a locking burr to each fin blade to assist in rigidly maintaining the fin in full open position during flight.

Propellant: The propellant consists of 30 sticks of ballistite.  Each stick is five inches long and 7/8-inch in diameter with a 1/4-inch axial hole.  Three sticks are placed on each trap wire, and there is sufficient clearance between the sticks and the wire to allow burning of the inner stick wall simultaneously with the burning of the outer wall.  Two igniter-bag assemblies are bound on two opposite columns of the propellant.  The bags assist the ignition of the propellant by catching the flame of the igniter and, in turn, igniting the upper propellant sticks.

Practice Rockets M9, M9A1, M9A2, M9A3: These rockets are similar in design and construction to the M8 series, lacking only the explosive charge and live fuze.  The Fuze M4 and booster may be assembled and used in the M9 as a spotting charge.

4.5-inch H.E. S.S. M16, M16E1, and M16E2; Practice M17, M17E1, and M17E2; M20 and M21

M16 Data

Overall length: 31 inches
Total weight: 42.5 pounds
Head length (w/ burster tube): 23.29 inches

TNT charge: 4.3 pounds
Maximum range: 5,250 yards
Muzzle velocity: 830 feet/sec

Fuzing: M81

Description: The head, loaded with high explosive, contains a fuze-well cup and a burster tube.  The burster tube projects about 15 inches into the center of the rocket motor to secure additional fragmentation.  The motor body is a steel tube threaded at each end to receive the head and the nozzle plate, which contains eight nozzles equally spaced in a circle and one nozzle in the center.  The eight nozzles are set at an angle in order to impart rotation to the round when fired.  The center nozzle is normally closed by a blowout disc which is designed to fail when the internal pressure in the body surpasses a predetermined limit.  The nozzle openings are protected by a plastic sealing disc which remains in place during firing and is blown out by the rocket blast.

Propellant: The propelling charge consists of 30 grains of ballistite strung on wires of a cage-like trap.  The igniter consists of a charge of black powder enclosed in a plastic tube attached to the trap and running the length of the charge.  The tube also contains an electric squib.  The leads of the squib pass through one of the nozzles, one lead being ground to the motor body and the other connected to a contact ring.

M20: The M20 is similar in design and construction to the M16, differing only in that the ignition wires are attached to spools rather than contact rings.

Practice Rockets M17 and M21: These are similar in design and construction to the H.E. rounds, but lack the explosive charge and the live fuze.

The M16E1 has a deeper fuze cavity for the V.T. Fuze M402 (Mk 173).  Shipped with these rockets is a supplementary charge to fill part of this cavity in case the Fuzes M81 or M48A2 are used.

The M16E2 is like the M16E1, except that purge pellets of 411E composition have been added to eliminate chunks in burning.

5-inch A.R.

No picture available

The Army is currently using the Navy-designed 5-inch aircraft rockets.

7.2-inch Chemical M25 and M27

No picture available

In the 7.2-inch size, the Army has standardized the chemical round designed by the Navy.

Next Time: Army Developmental Types

Monday, 11 December 2017

American Projectiles and Explosives - 1.1-inch, 7.2-inch, and "Pounder" Projectiles

American Projectiles and Explosives

1.1-Inch Projectiles

1.1-inch A.A.(a) Mk 1 Mods 0-28, (b) Mk S.D. 1

Overall length w/ nose fuze: 5.8 inches
Overall length w/o nose fuze: 4.1 inches
Diameter of base: 1.085 inches
Distance base to band: 0.87 inches
Width of band: 1 inch
Diameter at bourrelet: 1.095 inches

Filling: Explosive D

Weight of filling:
-(a) 0.037 pounds
-(b) 0.034 pounds

Weight of loaded projectile: 0.917 pounds
Charge/Weight ratio: 4%

Cartridge case: Mk 1

Primer: Mk 19 and Mods 1, 2, and 3

Tracer: Divided into two increments and pressed into the recess by hydraulic pressure, the tracer is ignited by the propellant charge from the cartridge case.

-Nose: Modified Mk 12 Mods 2 and 3 (P.D.F.)
-Mk 34 and all Mods (P.D.F.)

The 1.1-inch A.A. gun is not being further developed in the Navy.

The 1.1-inch Mk 1 is not self-destroying; the primary difference between the two projectiles.

The Mk S.D. 1 consists of a Mk 1 projectile body modified for self-destruction by drilling through the wall between the tracer and H.E. cavities.

The Mk 1 projectile may also be issued B.L. & T. for target practice or de-icing.

The 28 Mods are to distinguish among contractors.

1.1-inch A.A. Mk 2 Mods 0 and 1

Overall length w/ nose fuze: 5.7 inches
Overall length w/o nose fuze: 4.1 inches
Diameter of base: 1.085 inches
Distance base to band: 0.87 inches
Width of band: 1 inch
Diameter at bourrelet: 1.095 inches

Filling: Explosive D

Weight of filling: 0.034 pounds
Weight of loaded projectile: 0.917 pounds
Charge/Weight ratio: 3.7%

Cartridge case: Mk 1

Primer: Mk 19 and Mods 1, 2, and 3

Tracer: Divided into two increments and pressed into the recess by hydraulic pressure, the tracer is ignited by the propellant charge from the cartridge case.

-Nose: Modified Mk 12 Mods 2 and 3 (P.D.F.)
-Mk 34 and all Mods (P.D.F.)

The Mk 2 has a self-destroying tracer.

"Pounder" Projectiles

1-pounder Common Mk 2 Mods 0 and 1

Guns used in: 1-pdr/40
Overall length: 3.56 inches
Diameter of base: 1.441 inches
Distance base to band: 0.829 inches
Width of band: 0.731 inches
Diameter at bourrelet: 1.445 inches

Filling: Black Powder

Weight of filling: 0.026 pounds
Weight of loaded projectile: 1.088 pounds
Charge/Weight ratio: 2.07%

Cartridge case: Mk 2
Primer: Mk 10 Mod 9
 Tracer: Integral
Fuzes: Base: Mk 8 Mod 4 (B.I.F.)

This ammunition is used in coast guard guns.  Their bursting charge is black powder and TNT, or black powder alone.  This should be kept in mind when unscrewing the fuze, as some of the powder may have fallen down into the threads and the friction would cause detonation.

The Primer Mk 10 Mod 8 may be used for saluting charges only.

Base Fuzes Mk 2 Mod 9 and Mk 8 Mod 5, without tracers, may be used, but the Mk 8 Mod 4 is the preferred assembly.

This round may be issued B.L. & P. for target practice.

3-pounder Common Mk 4 Mod 1

Guns used in: 3-pdr/50
Overall length: 6.681 inches
Diameter of base: 1.75 inches
Distance base to band: 1.185 inches
Width of band: 0.787 inches
Diameter at bourrelet: 1.845 inches

Filling: Black Powder and TNT

Weight of filling: 0.13 pounds
Weight of loaded projectile: 3.3 pounds
Charge/Weight ratio: 3.93%

Cartridge case: Mk 1
Primer: Mk 10 Mod 9
 Tracer: Integral
Fuzes: Base: Mk 8 Mod 4 (B.I.F.)

Fuzes Mk 8 Mod 5 and Mk 2 Mod 9, without tracers, may be used; but the Fuze Mk 8 Mod 4 is the preferred assembly.  See other notes on 1-pounder Common.

6-pounder Common Mk 3 Mods 3 and 4

Guns used in: 6-pdr/40, /42, /45, /50
Overall length: 8.45 inches
Diameter of base: 2.224 inches
Distance base to band: 1.493 inches
Width of band: 0.787 inches
Diameter at bourrelet: 2.239 inches

Filling: Black Powder and TNT

Weight of filling: 0.24 pounds
Weight of loaded projectile: N/A
Charge/Weight ratio: 4%

Cartridge case: Mk 1
Primer: Mk 10 Mod 9
 Tracer: Integral
Fuzes: Base: Mk 8 Mod 4 (B.I.F.)

This round may be issued B.L. & P. or B.L. & T. with the Tracer Mk 7 for target practice.  See other notes on 1-pounder Common.

6-pounder Common Mk 5 Mods 0 and 3

Guns used in: 6-pdr/40, /42, /45, /50
Overall length: 8.26 inches
Diameter of base: 2.22 inches
Distance base to band: 1.493 inches
Width of band: 0.787 inches
Diameter at bourrelet: 2.237 inches

Filling: Black Powder and TNT

Weight of filling: 0.23 pounds
Weight of loaded projectile: 6 pounds
Charge/Weight ratio: 4%

Cartridge case: Mk 1
Primer: Mk 10 Mod 9
 Tracer: Integral
Fuzes: Base: Mk 8 Mod 4 (B.I.F.)

See notes on 6-pounder Common Projectile Mk 3.

7.2-inch Projectile

7.2-inch Projector Charge "Hedgehog"

Overall length: 38.6 inches
Head length: 19 inches
Head diameter: 7.2 inches
Head weight: 17.9 pounds

TNT filler: 31.1 pounds
Wall thickness: 0.2 inches
Tail tube diameter: 1.75 inches
Tail width: 7 inches

General: The projectile consists of a flat-nosed head with a conical tail fairing and parallel sides.  The adapter and fuze thread into the nose.  The motor unit consists of a smokeless powder cartridge with primer, which is lodged forward in the tail tube, the tube fitting over a firing post.  The primer is detonated by electric contacts in the post.  This charge is for use on Projectors Mk 10 and Mk 11.

The tail is a steel tube attached to the head by a threaded joint.  Tail fins have a 10-degree twist and are attached with a drum support to give a slow rotation and stabilized trajectory.

Remarks: When Torpex is used, the weight is increased by approximately 2.5 pounds.

The above data are based on the 7.2-inch Head Mk 4A and the 1.75-inch P.C. Tail Mk 4A.  These are being replaced by the 7.2-inch Head Mk 4 Mod 0 and the 1.75-inch P.C. Tail Mk 6 Mod 0

Nose Fuzes Mk 136 and Mk 140 are replaced by the Nose Fuze Mk 158

Next Time: Rocket Projectiles