American Projectiles and Explosives - Pistol and Hand-Size (Part 2)

American Projectiles and Explosives

Aircraft Pyrotechnics







Tracer With Two Stars Mk 4 Series

Length: 3.85 inches
Diameter: 1.52 inches

Burning time: 5 seconds
Burning time of tracer: 3-4 seconds
Height: 250 feet


Use:  Double-star signals are used as a method of emergency identification of aircraft.


Projection:  The Pyrotechnic Piston AN-M8 is used for fire the signal.


Description:  The outer case is similar to that of the Mk 3.  The star charges are contained in an inner case which also houses an ejector charge and tracer element.  Star color bands are the same as the bands on the Mk 3 and, in addition, a narrower band, before the star identification bands, indicates the color of the tracer.

Color combinations are:

-Red-red with Red tracer
-Green-green with Red tracer
-Red-red with Green tracer
-Red-yellow with yellow tracer
-Red-green with Red tracer
-Red-green with Green tracer


Operation:  The firing pin strikes the primer, igniting the propelling charge, which, in turn, ignites the tracer in the inner case and expels the inner case from the barrel.  The tracer becomes visible after traveling about 20 feet.  At approximately 250 feet altitude, the tracer ignites the ejection charge through the quick match, the stars being ignited by the ejection charge through the quick match as they are expelled from the inner case.











Aircraft Signal AN-M53 to AN-M58 Series

No picture available

Description:  Signals of this series are similar to the Mk 4 series.

Star Signal Mk 6

Length: 6 inches
Diameter: 2.5 inches
Weight: 1.4 pounds

Burning time: 25 seconds
Interval between launching and suspension: 2.75 seconds


Use:  Signals of this series are used primarily for emergency identification purposes at night.


Description:  The body of the signal is an aluminum cylinder with a bouchon type of grenade-firing mechanism on one end and a metal cap on the other.  Contained in the body are the ejection charge, the pyrotechnic candle, and a silk, rayon, or paper parachute.  The type and color of the signal star are printed on the side of the cylinder.  The closing cap on the lower end of the signal is embossed for night identification as fllows: red star, one dot; white star, straight line; and green star a wide "V".

All three signals have an arc of a circle, one inch in length, embossed near the edge of the cap.


Operation:  The signal is initiated in the manner prescribed for all bouchon-fuzed grenades.  The 2.75 second delay, having been ignited by the primer, ignites the ejection charge.  The ejection charge pushes off the closing cap, expelling the pyrotechnic candle and the parachute, at the same time igniting the starting mixture through a quick match.  The parachute opens and suspends the candle, which burns for 25 seconds.










Smoke Signal Mk 7

No picture available

Length: 10 inches
Diameter: 2.5 inches
Weight: 2.5 pounds
Color: Red, Yellow, Green, or Black

Burning time: 25 seconds


Use:  This smoke signal is used for emergency identification in daylight.


Projection:  The Pyrotechnic Piston AN-M8 is used for fire the signal.


Description:  The Smoke Signal Mk 7 is the same as the Star Signal Mk 6, except for its length and the composition of the pyrotechnic candle.  Also, the closing cap of the smoke signal is not embossed, but is painted the approximate color of the smoke produced.

Two-Star, Red, AN-M75

Length: 5 inches

Diameter: 1.125 inches

Burning time: 6-8 seconds

Color: Red

Height: 100-200 feet

Use:  This distress signal is used as an emergency rescue signal.

Description:  The signal is contained in a cylinder which houses the stars and the firing mechanism.  This mechanism consists of a pull release fork and a spring-loaded firing pin.

Operation:  The tape is removed from the top cover and the cover is removed.  The release fork is pulled; the firing pin is released and hits the primer, initiating the delay.  After two to four seconds, the first red star is ejected, and after three to five seconds the second red star is ejected.

Remarks:  This signal is not procured by the Navy.

Smoke Grenades AN-M8, M16, M18, and AN-M4

Length: 5.7 inches
Diameter: 2.57 inches
Weight: 1.68 pounds

Burning time: 3.5 seconds
Delay time: 3 seconds


Use:  These smoke grenades are used to attract attention to aviation personnel who have made a forced landing.


Description:  The cylindrical sheet-metal case is nearly full of a solid smoke mixture.  A circular zinc cup containing a starting mixture is located in a depression left in the top of the smoke mixture, and is designed to be initiated by a bouchon type of grenade-firing mechanism.  Adhesive tape covers four quarter-inch holes in the top of the case until the signal is ready for firing.  The grenade is painted gray and marked in yellow with one band, the symbol of the filler, "H.C.", and the word "smoke".


Operation:  The release lever cotter pin having been removed, the release lever is freed by the operator as the grenade is thrown, and is forced off by the striker, which is at all times under tension of its spring.  The striker moves on its hinge and fires the primer, which ignites a delay element that in turn ignites the starting mixture.  The starting mixture burns through the zinc cup and starts a chemical reaction in the smoke mixture, generating considerable heat with the formation of zinc chloride.  The zinc chloride escapes into the air as a gray-white smoke composed of finely divided solid particles.  These particles are highly hygroscopic and become very obscuring liquid particles.  The grenade burns for about three and a half minutes at full volume.


M-16 (Obsolescent):  Same as AN-M8.  May have red, yellow, green, orange, violet, or black smoke.


M18: Same as M-16, with burning reduced to one minute for a more dense smoke.  Available colors are red, green, yellow, or violet.


AN-M4:  Has a shorter fuze lever and is issued in a metal container with three flaps designed to be bent outward to provide additional bearing surface for use in mud of snow.  The AN-M4 is not procured by the Navy.

Next Time: Aircraft Pyrotechnics - Drift Signals and Navy Flares (Part 1)

American Projectiles and Explosives - Pistol and Hand-Size (Part 1)

American Projectiles and Explosives

Aircraft Pyrotechnics





Parachute Star M11, also M10, M14, M15, and M16

Length: 7.69 inches
Diameter: 1.58 inches

Burning time: 30 seconds
Intensity: 20,000 candlepower

Color: Red
Height: 200-250 feet


Use:  This is a distress signal from grounded planes.


Projection:  The Pyrotechnic Piston AN-M8 or Hand Projector M9 is used for firing the flare.


Description:  The cylindrical, aluminum outer case has an extraction groove at the end containing the primer.  A press-fit identification top is cemented to the end opposite the primer and has the embossed letters "R.P." for night identification.  This cartridge is classified by the Army as the rimless type.


Operation:  The firing pin of the pistol sets off the primer, igniting the propelling charge.  The propelling charge ignites the delay fuze and propels the inner case outward.  The delay fuze burns for 2.5 seconds and ignites the expelling charge, which in turn ignites the candle and expels the candle and parachute from the inner case.


Remarks:  The Army has other parachute signals which are similar to the M11.  These are obsolete or limited standard items.

Double Star AN-M28 to AN-M33 Series (Obsolete)

Length: 3.02 inches
Diameter: 1.58 inches

Burning time: 7 seconds

Height: 250 feet

Use:  Double star aircraft signals are used as emergency identification by aircraft.


Projection:  The Pyrotechnic Piston AN-M8 or Projector M9 is used for firing the signal.


Description:  The signal cartridge has an aluminum, plastic, or steel barrel with an extraction groove at the closed end which houses the primer.  A press-fit identification top is cemented into the opposite end, finished with embossed letters to identify the colors of the stars.  Appropriately colored bands around the outer case also identify the colors of the stars, in addition, the identification top is appropriately colored.  These signals are also classified by the Army as the "Rimless Type."


Operation:  The firing pin of the pistol strikes the primer, igniting the propelling charge.  As the stars are expelled from the pistol, they are ignited by the propelling charge through the quickmatch.  The stars reach full brilliance after travelling 40 or 50 feet, and rise to a height of approximately 250 feet.

Single Star AN-M34 to AN-M36 Series (Obsolete)

Description:  This series has the single star instead of the double star of the AN-M28 to AN-M33 series, but the dimensions are the same.


Remarks:  This series is not procured by the Navy






Aircraft Signals AN-M37 to AN-M42 and AN-M37A1 to AN-M42A1 Series

Length: 3.85 inches
Diameter: 1.54 inches

Burning time: 7 seconds

Height: 250 feet

Use:  These signals are used for emergency identification of aircraft.


Projection:  The Pyrotechnic Piston AN-M8  is used to fire this signal.


Description:  A metal or plastic head contianing the primer is crimped to the paper board or metal case, the opposite end of which is closed with a cardboard wad.  The colors of the stars are printed and painted on this wad, there being no means of night identification.  Colors of stars are also indicated by the appropriately colored bands on the case near the forward end.  These signals are classified by the Army as the Cartridge Type.


Operation:  These signals are similar to the AN-M28 to AN-M33 series in operation.


Remarks:  The A1 series has an aluminum case.

Single Star AN-M43 to AN-M45 and AN-M43A1 to AN-M45A1 Series

Description:  This series has a single star instead of the double star of the AN-M37 to AN-M42 series; dimensions are the same.





Two Star Cartridge Mk 3 Mod 3



Description:  These are interchangeable with the AN-M37 to AN-M42 series.  There is no means of night identification.  Color combinations available are: red-red, yellow-yellow, green-green, red-yellow, red-green, or green-yellow.

Next Time: Aircraft Pyrotechnics - Pistol and Hand-Size (Part 2)

American Projectiles and Explosives - Aircraft Pyrotechnics Introduction

American Projectiles and Explosives

Aircraft Pyrotechnics

General


These chapters on pyrotechnics deal with items whose principal function is either signalling or illuminating.  For instance, signalling smokes are treated as pyrotechnics, but screening smokes are discussed elsewhere, under the ordnance items which carry them.

The effectiveness of pyrotechnics is dependent on three major factors: design, position, and the atmospheric conditions prevailing at the time of use.  Variations of design govern the candlepower of the flare or signal, the color produced by the charge, and the continuity of the burning candle.  The color and reflective characteristics of the objective often affect the visibility of pyrotechnics.  Open ground, such as an airfield, will reflect three to four times as much light as will woods or deep water.  Position, distance, relative position, background, or angle of observation also alter visibility, while the degree of light or darkness, fog, haze, or other atmospheric conditions have obvious effects.

Composition

Pyrotechnic compositions are complex chemical mixtures.  On burning, they produce illuminations ranging in intensity from the "dark fire" used as an element of blinker signals to the brilliant flash produced by the photoflash bombs.  Standard pyrotechnics, in general, consist of compounds to provide oxygen for burning, such as chlorates and nitrates; aluminum or magnesium for fuel; salts of barium, copper, or strontium for color; and agents such as asphalt and paraffin for binding and waterproofing.

Pyrotechnics usually function by means of an igniter train similar to an explosive train.  In general, ignition is initiated by a primer mixture and intensified by a "first-fire" composition which ignites the luminous candle.

Handling and Stowage

All pyrotechnics should be handled with care.  Rough handling may cause immediate functioning of the item, or it may damage the item so that it will not function properly at the desired time.  Much of the pyrotechnic material is more sensitive than other types of ammunition.

Pyrotechnics should be stowed in the boxes or watertight containers in which they are shipped, whenever possible.  They must not be stowed with other types of ammunition.

Pyrotechnics should never be stowed where the direct rays of the sun can strike them.  They should be protected against excessive and variable temperatures.  If possible, the stowage space should be kept at a temperature below 100 degrees Fahrenheit, and must be kept dry and ventilated.




Disposition

 When directed by the Bureau of Ordnance, pyrotechnics may be disposed of by dumping overboard or burning.  Dumping is preferred, and must be done ten miles off shore and in water at least 100 fathoms deep.  Certain items must always be dumped, while other items may be either dumped or burned.

Methods of projection

Aircraft pyrotechnics

1. Pyrotechnic Pistol AN-M8:  This pistol is used on aircraft with the Mount M1 and fires through an opening, in the fuselage.  It can also be detached from its mount and fired by hand.  It is generally used for signalling from aircraft in flight, to troops on the ground or to other aircraft.

2. Hand Projectors Mk 3 and Mk 4:  These projectors are fired by holding the barrel in one hand and pulling back on the firing pin handle with the other.  They are used to fire Very's Signal Light Mk 2.

3. Signal Pistol M5:  This is a single-action, single-loading pistol that fires the Very's Signal Light Mk 2.

4. Very Pistol M5:  This is a single-action, single-loading pistol that fires the Very's Signal Light Mk 2.  It is not procured by the Navy.

5. Pyrotechnic Discharger AN-M5:  This is a double-action, multi-barrel (6) discharger used on aircraft when installation of pistols is not practicable.  It is used for the same purpose as the Pyrotechnic Pistol AN-M8.  It is not procured by the Navy.

6. Hand Pyrotechnic Projector M9:  This is a single-action, single-loaded projector which is fired by striking the firing pin with the hand or by striking the firing pin on the ground.  It is used for projecting signals from the ground to aircraft in flight.  It is not procured by the Navy.

7. Pyrotechnic Discharger M10:  This is a metal cylinder with a mushroom firing mechanism and a hinged locking stem.  It is used to fire the Red Star Signal M73.

Ground pyrotechnics

1. Ground Signal Projector M1A1:  This is a single-loaded manually operated projector used to fire the High-Bursting-Range Ground Signal M27

2. Ground Signal Projector M3:  This is a single-loaded, manually operated projector that is fired by holding the projector in the hand and striking the base on the ground.  It is used to fire Signals M17 through M22.

3. Ground Signal Projector M4:  This projector is similar to the M3 and is replacing it.

4. Grenade Launchers M1, M2, M7, and M8:  This type of launcher is an extension to the barrel of a rifle or carbine.  It is used to fire ground signal M17A1 through M22A1, M51A1, and M52A1.

  

5. Tree Suspension Device T1, For Smoke Grenade:  This is a cardboard attachment containing about ten feet of suspension cord.  It is attached to a standard smoke grenade that is launched from a carbine or rifle.  The device is used to cause grenades to become entangled in trees or foliage, to permit emission of smoke above dense forests and foliage where it is readily visible to air observers.

Ship and submarine pyrotechnics

1. Signal Projector Mk 1 and Mk 1 Mod 1:  This is a barrel, about 30 inches in length which fits into a tube mounted on a three-legged stand.  The firing pin is part of a metal disc which acts as a valve.  It is used to fire Ship's Emergency Identification Signals Mks 1, 2, 3, and 4.

2. Submarine Rocket Pistol:  This is a single-loaded, breech-loaded pistol used to fire pistol rocket signals.

3. Submarine Emergency Identification Signal Ejector:  This ejector is similar to a miniature torpedo-tube arrangement.  It is used to fire Submarine Emergency Identification Signals, Submarine Float Signal Mk 1, Mk 1 Mod 1, or Mk 2 Mod 0, and False Target Shell, Mk 1.

4. Other Projectors:  These include Hand Projectors Mk 2 and Mk 4, and pyrotechnic Pistol An-M8, which are described above under Aircraft Pyrotechnics.  There is also a High-Altitude Mortar Mk 20 being developed, to which official nomenclature is being assigned.

Next Time: Aircraft Pyrotechnics - Pistol and Hand-Size (Part 1)

American Projectiles and Explosives - Navy Rockets (Part 4)

American Projectiles and Explosives

Navy Rockets






7.2-inch H.E. "Mouse Trap" and 2.5-inch Practice

No picture available

Overall length: 38.6 inches

Head length: 19 inches

Head weight: 17.9 pounds

Wall thickness: 0.2 inches

Motor length: 15.9 inches

Motor diameter: 2.25 inches

Motor weight: 8.1 pounds

Tail width: 7 inches

Filler Weight (TNT): 31 pounds

Total weight: 65 pounds

General: This rocket was designed for use by patrol vessels against submarines.  The most common installation consists of two four-rail Launchers Mk 20, with a fixed elevation of 48 degrees, mounted on the fore deck with firing controlled from the bridge.


Head: The projectile consists of a flat-nosed head with a conical tail fairing and parallel sides.  The adapter and fuze thread into the nose, and the motor unit threads into the base.


Motor: The Motor Unit Mk 3 contains a long single pellet of smokeless powder which, when ignited by a black-powder primer fired by an electric squib, burns at a pressure of 1,000 to 2,500 pounds per square inch.  The gases are forced out aft through the nozzle in the rear end of the motor tube.  The burning continues for 0.2 to 0.7 seconds, during which time the missile travels about 30 feet.  At this point, propulsion ceases and the projectile is free in flight.  This projector charge is intended for use on the 7.2-inch Rocket Launchers Mk 20, Mk 21, or Mk 22.

Tail: A steel tube attached to the head by a threaded joint has fins with two circular drums attached to the after end.  The vanes have a 10-degree twist to give a slow rotation and prevent ruddering.  The two vane-support drums also act as contact rings, the wiring from the electric squib passing from the primer after to the two rings which serve as firing contacts.


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

The 2.5-inch sub-caliber rocket, consisting of the 1.25-inch Motor Mk 1 and 2.5-inch Head Mk 1, is a miniature of the regular rocket and is used in practice.  The motor contains a single tubular powder grain, an igniter, and lead wires.  The tail fins, supported by a shroud, are offset five degrees to impart some rotation to the round, to improve underwater travel.  The Head Mk 1 has a cavity for a shotgun shell; the Head Mod 2 Mk 1 is solid.

The Fuzes Mk 131 and Mk 140 are replaced by the Mk 156 in service rounds.

7.2-inch D.R., also T37 and T38

(Head Mk 10)

Overall length: 35 inches

Motor diameter: 2.25 inches

C-2 Explosive: 33 pounds

Loaded weight: 60 pounds

Maximum range: 275 yards

Motor: 2.25-inch Mk 3

Fuzes:

-Head Mk 5: Nose Fuze Mk 152 or Mk 141

-Head Mk 10: Base Fuze Mk 146

-Head Mk 10-1: Base Fuze Mk 161 Mod 0

General: The 7.2-inch D.R., a modification of the 7.2-inch H.E., was used for demolition of anti-tank obstacles.  The 7.2-inch D.R. was projected from a multiple-rail armored launcher mounted on the turret of the Tank M4.  It was fired at point-blank range and proved effective against concrete obstacles at ranges of 100 to 150 feet.

 

Description: The rocket has a thin steel head to give the maximum blast effect.  The propellant is the single unperforated cruciform Grain Mk 10.  The body can be fitted with any one of a number of rocket motors to give velocities from 175 to 400 feet per second.  The mean lateral deviation is 10 mils from a 90-inch launcher.

The Base Fuzes Mk 146 and Mk 161 Mod 0 are armed during flight by the pressure of the gas evolved from the burning propellant acting on the diaphragm.  The Head Mk 10 Mod 1 is the Head Mk 10, slightly altered to accommodate the new motor adapter of the Base Fuze Mk 161 Mod 0.


Remarks: The Army designates the Head Mk 10 or Mk 10 Mod 1 as the T37.

A smoke-filled round used by the Army is the same size, and has the designation of T38.  It is nose-fuzed with either the Fuze Mk 152 or the Fuze Mk 141.

The Head Mk 5 may take either the Booster Mk 1 or the Booster Mk 2; the Head Mk 10, only the Booster Mk 1.

The Heads Mk 5 are loaded with TNT; the Heads Mk 10 may also take a TNT load.

7.2-inch C.W.R.N. and M25, M27, and T24

(Motor Mk 5 and Head Mk 7)

Overall length: 48.1 inches

Head width: 7.2 inches

Head length: 18.75 inches

Motor length: 29 inches

Propellant (ballistite): Grain Mk 11

Filler: Any chemical filler with specific gravity over 1.2

Filler (F.S.): 19.7 pounds

Total weight: 53.2 pounds

Range: 3,500 yards

Fuzes: Nose Mk 147 or Mk 147 Mod 1

General: This rocket is fired from a 24-rail demountable, variable-elevation launcher carried in a 2 and 1/2 ton truck.  The salvo is fired in 2.5 seconds, and the launcher can be reloaded in 1.5 minutes.

These rockets of Navy design are under production by the Army.  The only essential difference between the rockets as used by the Army and the Navy is in the propellant.


Head: The container is a bulb-shaped steel tube open at both end.  The adapter fits inside the flange on the forward end of the container and is brazed thereto.  The wide forward end of the adapter is internally threaded to seat the fuze.  The burster tube, made of steel, fits inside the adapter and extends downward into the container.  The tube and adapter are held together by a press fit and sealed with white-lead paste.  The rear end of the tube is closed.


Motor: The motor is a steel tube, with the forward end externally threaded to screw-into the connector of the head.  The nozzle is slipped down through the open end of the motor body, and the end is welded to the inner edge of the motor-body rim.

Tail: The tail assembly has four tail vanes spot-welded in pairs to the motor tube and spot-welded to the rear shroud.  The forward shroud is riveted to the vanes but insulated from them.  Four large fins are welded to the motor tube, pass over the forward shroud, and are welded to the rear shroud.  The lead wires are connected to the two shrouds which serve as contacts.


Propellant: As produced for the Navy, the propellant consists of a single grain of solvent-less extruded ballistite with an outer diameter of 2.5 inches and an inner diameter of 1 inch.  This is the Grain Mk 11.

In the Army Chemical Rocket M25, the propellant consists of four sticks of ballistite, with a one-inch axial hole, placed end to end with separating washers between the sticks.  The sticks are three-ridged, and each has eight sets of holes radially through it.  The overall length of the sticks is 20.5 inches.


Remarks: The Army Rocket M27 is structurally the same as the Navy rocket, but is filled with C/K gas.  Its total weight is 51.8 pounds.

A head similar tot he Mk 7 but loaded with 22 pounds of TNT and equipped with a booster instead of a burster tube is known as the Mk 9.  It is a demolition head, using the Fuze Mk 137 and the 3.25-inch Motor Mk 5.  This combination may be used to lay down a barrage from the same launchers as the C.W.R.N.

When the Head Mk 9 is fuzed with the Fuze Mk 147, it is known as the Round T24.  Its total weight is 51.8 pounds.






11.75-inch A.R. "Tiny Tim"

Overall length: 123 inches

Total weight: 1,253 pounds

Head length: 47 inches

Head weight: 600 pounds

Motor length: 82.4 inches

TNT filling: 152.5 pounds

Fuzes:

-Mk 1 Mod 0: Mk 157 Mk 1

-Mk 1 Mod 1: Mk 157 Mod 2

-Mk 2 Mod 0: Mk 157 Mod 2, Mk 163 Mod 0, Mk 162 Mod 0

Heads: The Mk 1 Mod 0 consists of a standard 500 pound S.A.P. Bomb AN-M58A1 modified for this particular use.  The changes include the removal of the suspension lugs, an increase in the number of threads securing the base plate, the use of a new base plug to take the Fuze Mk 157 Mod 1, and the use of an adapter ring welded around the after end as a means for attaching the rocket motor.  The motor gases are sealed from the high explosive in the body by coating the threads of the base plate with a luting compound, and also by a gasket under the fuze body flange.

The Mk 1 Mod 1 is similar to the Mk 1 Mod 0, except that a projectile-type gas seal is added around the head of the Fuze Mk 157 Mod 2.

The Mk 2 Mod 0 was developed from the Mk 1 Mod 1.  This head differs in that it has a solid-nosed "Common" head and a base plate modified to take three Base Fuzes Mk 157 Mod 2.  The projectile-type gas seal is used around all fuzes and also between the base plate and the forged steel body.  The Fuze Mk 157 Mod 2 is used with one Auxiliary Booster Mk 1 Mod 09, or the Fuze Mk 163 Mod 0 with one Auxiliary Booster Mk 19 Mod 0.

The Head Mk 3 Mod 1 was issued for practice to simulate the Head Mk 2 Mod 0.

The Head Mk 4 Mod 0 is slightly lighter and shorter than previous heads.  The head weight is 578 pounds, including 152 pounds of TNT.  The head length is 46 inches.  Three Fuzes Mk 153 Mod 0 or Mk 162 Mod 0 are used in the base.  The penetrative characteristics of this head are the same as those of rpesent types, but slightly better overall performance may be expected, because of the small increase in velocity resulting from reduction in total weight.

The Practice Head Mk 5 dummies the Mk 4.  It is 44.75 inches long and weighs 569 pounds.  It has a cavity for a smoke puff.

The heads are shipped loaded and fuzed.  A cuff protects the threads on the adapter ring and the fuze during shipment.


Motors: The Mk 1 Mod 0 consists of a steel tube, the after end of which is threaded to receive a plate having twenty-five nozzles.  The motor tube contains four propellant grains of solvent-less extruded ballistite of cruciform cross-section, weighing 147 pounds.  The grains are shielded from each other by an X-shaped partition which extends longitudinally for almost the full length of the motor tube.  The grains and the partition are supported by the grid and are strapped together by aluminum bands.

In normal operation, the gases from the burning powder do not pass through the central nozzle, which is closed by a copper blowout disc.  Only when the pressure in the motor exceeds approximately 22,500 pounds per square inch is this disc expelled, bringing the central nozzle into operation.  The use of a blowout disc allows the rocket motor to perform satisfactorily over a greater temperature range.  It has one disadvantage, however, in that at motor temperatures of about 100 degrees Fahrenheit, where the normal operating pressure is just enough to shear the disc, it is impossible to predict whether it will blow out or not.  If it does, the burning time is lengthened and the gravity drop is increased, so that the rocket may miss the target.

Four black-powder charges of about 0.5 pounds each, contained in plastic cases at the front ends of the grains, provide the ignition for the propellant.  They are set off by two small electric squibs in each case, which are connected to receptacles in the nozzle plate.  The burning of the propellant is markedly affected by its moisture content.   Consequently, the motors are sealed at both ends.  Each of the 24 peripheral nozzles is sealed with a thing steel cup.  The front end is sealed with a thin steel disc having in its center a small blowout window.  This window is blown out by the motor pressure, allowing the propellant gases free access to the base fuze.  These closures should not be removed.

The Igniter Mk 19 Mod 0 has recently been developed for use in 11.75-inch A.R. motors.  Known as a tin-plate case igniter, it consists of a single metal case 3.38 inches in diameter and 1.8 inches deep, with a wall thickness of 0.01 inches.  Four clips are soldered to the base of the case, for attachment to the motor charge support.  The case contains 230 grams of F.F.F.G. black powder.  Contained in the case are two electric squibs connected in parallel to the igniter lead wires.

Motors must never be fired above the rated temperature stenciled on the motor, because they are likely to burst.   Below the lower rated temperature, occasional ignition failures and interrupted burning may be experienced.

The Motor Mk 1 Mod 1 is identical to the Mk 1 Mod 0, except that the motor tube is of higher tensile strength and the pigtail connection has been replaced by two receptacles built into the base plate.

The Mk 1 Mod 2 is a design in which the dead space between the forward motor closure and the base of the rocket head has been eliminated.  This motor is similar in other respects to the Mk 1 Mod 0, except that the overall length has been reduced to 75.75 inches by two receptacles built into the base plate.

The Motor Mk 1 Mod 3 is the Bureau of Ordnance production of the Mk 1 Mod 2.

The Motor Mk 2 Mod 0 weighs 600 pounds and is 72.04 inches in length.  Length and weight reduction have been accomplished by improvements in design detail. so that the total amount of propellant in the motor has not been changed.  Because of design and construction changes, the Motor Mk 2 Mod 0 may be used only with the Head Mk 4 Mod 0.

Next Time: Aircraft Pyrotechnics (Part 1)

American Projectiles and Explosives - Navy Rockets (Part 3)

American Projectiles and Explosives

Navy Rockets






4.5-inch B.R.

(With Head Mk 3)

Overall length: 30 inches

Weight: 28.7 pounds

Head length: 18 inches

Head weight: 19.9 pounds

Wall thickness: 0.25 inches

Motor length: 15.5 inches

Motor diameter: 2.25 inches

Range: 1,000-1,100 yards

Weight of TNT charge: 6.5 pounds

Fuze: Mk 137 or Mk 145

General: The 4.5-inch Barrage Rocket is a light demolition rocket intended for launching from landing boats, from amphibious trucks, or from portable launchers of one or more rails.


Head: The head and motor are coupled by means of a threaded adapter, and the fuze screws into the nose of the head.  The head is cylindrical, the forward and hemispherical and the read end reduced.  About 6.5 pounds of high explosive can be loaded through a 2 and 3/4 inch hole in the rear, which is sealed later with a motor adapter.  The fuze liner, in the nose of the head, contains a booster charge of granular TNT.

Tail Assembly: Two circular shrouds, the same diameter as the body, are attached to supporting fins at the rear of the motor.  Two wires brought out through the powder grain and the nozzle connect to the two shrouds.  The forward shroud is insulated from the rest of the rocket to prevent a short-circuit to the after grounded shroud.

Propellant: The propellant consists of a single cylindrical grain of ballistite 11 inches long, with a 1.7 inch outer diameter.

5-inch A.R. with 5-inch motor

Overall length: 69 inches

Weight: 140 pounds

Head length: 20.3 inches

Head diameter: 5 inches

Head weight: 52 pounds

Motor length: 51.4 inches

Motor diameter: 5 inches

Velocity: 1,350 feet/sec

Fuzes: Mk 5 Mod 0 and Mk 6 Mod 0

-Nose Fuze Mk 148

-Nose Fuze Mk 149

-Base Fuze Mk 157 Mod 0

-Base Fuze Mk 159 Mod 0

Mk 6 Mod 1

-Base Fuze Mk 159 Mod 1

-Base Fuze Mk 164 Mod 0

Head: The Head Mk 6 Mod 0 is filled with TNT and is equipped with a base fuze and a nose plug.  When thus used, the head will have the penetration and fragmentation characteristics at comparable velocities of the 5"/38 AA Common projectile, of which it is a modified design.  All 5-inch Rocket Heads Mk 6 Mods 0 and 1 are shipped with a base fuze installed and staked in place.  No attempt shall be made to remove the base fuze from the head prior to the firing.  A metal cup-shaped thread protector covers the external threads on the base of the head and on the base fuze.

The Mk 6 Mod 1 is similar to the Mk 6 Mod 0, with a gas seal added to the bomb-fuze seat.  The 5-inch Body Mk 5 Mod 0 is the initial California Institute of Technology production, which was adopted by Bureau of Ordnance as the Mk 6 Mod 0.  The two bodies are identical.

The 5-inch Aircraft Common Mk 2 Mod 1 is a new head designed to achieve greater penetration.  This penetration is expected to be two to three inches of homogeneous armor plate at launching speeds of 1,500 feet per second.  The head has a total weight of 48.1 pounds, is 14 inches long, and contains a filler of 2.66 pounds of Explosive "D".  The nose is heavy and solid.  A base fuze (the Mk 166 Mod 0) will be shipped installed.  This head will fit any of the 5-inch motors.

The Head Mk 2 Mod 2 has no adapter and has Acme thread; otherwise it is the same.

Motor: The 5-inch Motor Mk 2 Mod 0 consists of a seamless steel tube with internal threads on both ends.  Into the rear end is screwed the nozzle plate having eight nozzles arranged in a circle, and a central blow-out nozzle.  The central nozzle is closed by a disc of 0.024-inch thick copper, insulated against the heat of the motor by asbestos and hard fiber plugs.  The thickness of the disc is such that it shears and blows out at a pressure of approximately 2,400 pounds per square inch, which is the normal maximum motor pressure when the propellant grain is at a temperature of 100 degrees Fahrenheit.  If the pressure rises above this, the disc and plug are ejected; this increases the usable temperature range of the rocket by about 40 degrees Fahrenheit.

Seven of the eight nozzles are sealed individually by a light steel cup and sealing compound.  The eight nozzle accommodates the electric connector cable, which is crimped into the steel nozzle closure.  In shipment, a dome-shaped steel shipping cap fits into the sleeve of the fin assembly, acting as an auxiliary seal and at the same time serving to enclose and protect the electrical pigtail in shipment.

Lugs for attaching the fins are mounted on the nozzle end of the motor.  The fins are shipped with the motor and are attached when the round is assembled.  The fins are held in place by spring-loaded latches within the fin itself.  The fin lugs and rear suspension lugs are welded to the bands of the fin assembly, which is slipped on over the nozzle end of the motor.  The front lug band is strapped to the motor.  The motor is shipped with lug attachments on the motor tube for use with Aircraft Launcher Mk 5 Mod 1.  An extra rail-type lug is provided in the shipping box to adapt the rocket for use on the Aircraft Launcher Mk 4.

The front end of the motor is sealed by a steel diaphragm equipped with a blow-out disc in the center to allow easy passage of the motor gases to the pressure-arming fuze in the base of the body.  In shipment, a cylindrical metal thread protector extends into the motor the same depth as the body and seats on a felt rim glued to the diaphragm seal.

The propellant is a grain of cruciform ballistite weighing 24 pounds.  The grain is inhibited on the outer web surface and is supported by a spacer and a steel grid at the nozzle end.  The propellant is ignited by a metal case igniter containing 35 grams of black powder.

The 5-inch Motor Mk 2 Mod 1 was never produced.  The Mk 2 Mod 2 differs in that the tail fins are welded to a sleeve which slips over the base of the tube and is clamped in place.  The fin assembly is complete and separate from the motor.  The rear suspension lug for use with the Launcher Mk 5 Mod 1 is on an independent band.  The Mk2  Mod 3, which will supersede the Mods 0 and 2, is similar to the Mod 2, except that the nozzle ring is of slightly different construction.

The 5-inch Rocket Motor Mk 1 Mod, California Institute of Technology production, is the prototype of the Mk 2 Mod 0, Bureau of Ordnance issue.  The two motors vary only in that the suspension lugs on the former are welded directly to the rocket motor.

5-inch S.S.S.R.

General: The General Purpose and Common rounds are particularly adapted for repelling PT-boat attacks at ranges less than 11,000 yards.  The High-Capacity rockets are suitable for barrages at 1,250 to 5,000 yards.  These rockets must be used in the specially designed Launchers Mk 50 Mods 0 and 1 and Mk 51 Mods 0 and 1; and in Launcher Assemblies Mk 101 Mod 0 or Mk 102 Mod 0.



Heads

5-inch Head Mk 7 - General Purpose: This head is threaded externally at the after end to accommodate the motor.  It is threaded internally at the forward end to accommodate the fuze adapter for Rocket Fuze Mk 100 and Mods.  Two spanner holes are located in the after end of the head spaced 180 degrees apart to facilitate assembly.  The fuze adapter is internally threaded for Auxiliary Detonator Fuze Mk 44 Mod 2.  The Nose Fuze Mk 100, all Mods, is screwed in over the Auxiliary Detonating Fuzes.  (The fuze adapter and an Auxiliary Detonator Mk 44 Mod 2 are shipped installed in the head.)


5-inch Head Mk 8 and Mods - Common: The head is internally threaded at the after end to take Base Fuze Mk 31.  It has two spanner holes 180 degrees apart to facilitate assembly operations.


5-inch Head Mk 10 and Mods - High Capacity: The nose of this head is internally threaded to fit Nose Fuze Mk 30 Mod 3 and a fuze adapter.  It has two spanner holes 180 degrees apart near the base end to facilitate assembly operations.  The fuze adapter is internally threaded to hold Auxiliary Detonator Mk 44 Mod 1, and the Nose Fuze Mk 30 Mod 3 fits over the auxiliary detonator.


5-inch Head Mk 12 and Mods - High Capacity: The 5-inch Head Mk 12 and Mods is 3.125 inches longer than the 5" Mk 10 head used in the 5,000 yard round.  It carries 2/8 pounds more TNT than the Head Mk 10.


5-inch Head Mk 13 and Mods - High Capacity: The 5-inch Head Mk 13 and Mods is 4.78 inches longer than the 5" Head Mk 10.  It also carries about four pounds more TNT.




Motors

5-inch Motor Mk 3 and Mods: The motor tube is a seamless steel tube with internal threads at both ends.  It is machined with a bourrelet ring at each end.  The front closure is a steel disc pressed in position near the front end of the motor tube.  It seals the front end from moisture, dirt, etc., and retains the igniter and propellant grain in place.  A thin felt pad cushions any contact between the front closure and the igniter.  The Igniter Mk 17 Mod 0 consists of a flat tin case containing 35 grams of black powder and an electric squib.  A felt disc one inch thick protects the grain from accidental shock.  It has an eccentrically placed hole which houses and forms a snug fit for the igniter case.

The propellant is an inhibited, cruciform grain weighing approximately ten pounds.  The nozzle plate assembly consists of eight nozzles and a grid mounted on a nozzle plate.  The cylindrical T-shaped steel grid is pressed into place and peened in position in a center hole in the nozzle plate.  It acts as a spacer between the grain and the nozzle plate, creating a chamber which equalizes the pressure to all nozzles during burning.  The nozzles are press fitted into the plate and are canted 12 degrees to give a clockwise rotation.  The nozzle-plate ring assembly consists of a nozzle-plate ring and the insulated contact ring.  The contact ring is a steel band around the nozzle-plate ring and is insulated from it.  The plate ring and contact ring are the two terminals of the ignited electrical circuit.  The rings are short circuited by a band.  The short-circuiting band must be removed when preparing the rocket for firing.  The rear closure is a thin aluminum cup cemented in place in the after end of the motor, and blows out after the motor pressure builds up.


5-inch Motor Mk 4 and Mods: The 5-inch Rocket Motor Mk 4 is similar to the Mk 3 discussed above, except that the motor tube is seven inches shorter than the Motor Mk 3.  The Igniter Mk 18 with shorter leads is used.  Propellant Grain Mk 22 Mod 0, shorter and weighing approximately 5.5 pounds, is used.  The nozzle in the nozzle-plate assembly has a smaller throat diameter.


5-inch Motor Mk 5 Mod 1: The Mk 5 Mod 1 is similar to the Mk 4, except that it is 3.125 inches shorter and the nozzle plate has four instead of eight nozzles.  This shorter motor gives a range of 2,500 yards and a maximum velocity of 475 feet per second, which is suitable for barrage purposes.


5-inch Motor Mk 6 Mod 0: The Mk 6 Mod 0 is also similar to the Mk 4 and Mods, except that it is 4.78 inches shorter and the nozzle plate has only four nozzles.  The cant of these nozzles has been increased to insure stable flight of the round at slower velocities.  This shorter motor gives a range of 1,250 yards and a maximum velocity of 340 feet per second, which is suitable for barrage purposes.

Next Time: Navy Rockets (Part 4)