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.


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.




Motors


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)