The purpose of this Ordnance publication is to acquaint personnel with the rocket and projector charge fuzes now in use and those rocket fuzes which may not have been pro-duced for the purpose of issue but which may be released for production should circum-stances warrant.

Illustration are included for each type of fuze. In general, the explantory matter is ar-ranged to cover General Data, Description, Functioing, Safety Features, Disposal and Servicing, Installation in Rocket, and Packing and Marking for each fuze described. In ad-dition the introduction lists and briefly describs the various forces which determine rocket fuze design, explosive components utilized, safety features and methods of test. Radio proximity fuzes are not included in this pamphlet but are described in OP 1470 and OP 1480.

There are three general classes of fuzes used in rockets which are as follows:

Nose Fuzes

Base Fuzes

Auxiliary Detonating Fuzes

Rocket fuzes may be classified according to the type of rocket in which they are em-ployed:

1. Fuzes for fin-stabilized (non-rotating) rockets which include both nose and base fuzes. This includes rockets launched from aircraft and those launched from ground or shipboard.

2. Fuzes for spin-stabilized (rotating rockets) which may be either nose or base and also include the auxiliary detonating fuzes when nose fuzes are employed.

3. Fuzes for anti-submarine rockets or projector charges which generally depend on passage through water to complete arming.

The forces which are utilized in rocket fuzes depend upon the characteristics of the rocket for which the fuze is designed. The principal forces used in arming gun ammunition fuzes are those due to setback in the bore of the gun, and centrifugal force due to spin. The principal force utilized in bomb fuzes is that exerted by the wind stream as the bomb falls through the air. These forces are also present in rockets fuzes is controlled to a great extent by what forces are available that can be untilized.

1. Acceleration (setback). Long burning times and low accelerations, as compard to gun ammunition, are characteristic of rockets. Acceleration attained is greatly dependent upon the initial temperature of the propellant of the rocket motor and is quite low for lower temperatures. Because of this condition, fuzes actuated by setback forces must be designed to operate at the minimum acceleration. Setback is often untilized to delay the arming of rocket fuzes. Small setback forces are made effective where applicable by making the parts operated by setback relatively massive and springs relatively weak as compared to gun ammunition fuzes.

2. Wind forces. The force exerted by the wind stream past the rocket in flight is uili-zed to arm many rocket nose fuzes for fin-stabilized rockets.

3. Gas pressure of burning propellant. During the burning of the rocket motor pro-pellant, pressure of the resulting gases is exerted on the base of the rocket head and base fuze, if present. This pressure is fairly constant during burning and is in the magni-tude of serveral hundred pounds. Because the pressure lasts for a considerable time, its entrace into the fuze can be controlled and utilized to start as well as delay the arming of the fuze.

4. Centrifugal force. This force is available in spin-stabilized rockets, due to the ro-tation of the rocket and attains its maximum at the end of burning after the rocket is launched. The spin is of the same order as that of projectiles, and has permitted the adaption of some gun ammunition fuzes for rockets where forces other than centrifugal forces are not required to arm the fuze.

5. Creep (deceleration). This is a continuous inertia force caused by drag which tends to move internal fuze parts toward the nose of the round. In some cases these force are controlled in rocket fuzes by anti-creep springs to prevent fuze initiation until the fuze strikes a target with sufficient impact to overcome the springs.

6. Friction. Frictional forces due to setback and creep are not high in rockets. How-ever. they must be considered in their effect on moving parts. Friction due to centrifugal force may be quite high in rockets.

The explosive materials used in rocket fuzes are the same as those used in bomb and projectile fuzes and are subject to the same requirements and composed of the same materials.

The explosive train in a rocket fuze usually consists of the follwing components:

1. The primer, which is initiated mechanically by the firing pin. There are two types used, namely, the stab type, and the percussion type. The stab type is initiated by pe-netration of a sharp-pointed firing pin through the metal case into the primer mixture and the percussion type is initiated by crushing the primer mixture between an anvil and the indentation of the primer cup caused by a round-pointed firing pin. Stab type primers are general used when instantaneous fuze action and increased sensitivity are desired and the percussion type when the fuze contains a delay element. Primer mixtures are inten-ded to produce flame and hot gases and particles as a result of mechanical disturbance, and are generally composed of an initiating substance (lead azide or mercury fulminate), an oxidizing agent (potassium chlorate) and a reducible substance (antimony sulfide) and may also contain a friction-creating material (fine carborundum crystals). Lead azide pri-mer mixture is usually used for stab-type primers because of its slower rate of decom-position. Mercury fulminate primer mixture is often used in percussion primers for fuzes because of its greater sensitivity.

2. The delay element, a compressed pellet of black powder which is ignited by the primer. The delay time obtained with a given primer is varied by adjusting the compositi-on of black powder, the pellet pressure, and the thickness of the wall that must be burn-ed through.

3. The detonator, which is initiated by the primer of delay element. It is composed of a pure initiating explosive, usually lead azide, followed by a small amount of tetrly. The above materials may be sealed in small containers separately or they may be sealed to-gether in one container.

4. The lead-out and lead-in, which are small pellets of tetryl used to reinforced the small detonation of the detonator, and to transmit it to the booster. A lead-out is not necessarily used; if used, it usually moves with the detonator during arming.

5. The booster, a comparatively large tetryl pellet, loaded in a container as a part of the fuze, which is initiated by the lead-in and in turn initiates the main high explosive fil-ler of the head, either directly or through an auxiliary booster of granulated TNT.

The safety requirements for rocket fuzes are in general similar to those for gun ammu-nition and bomb fuzes. The fuze must contain adequate safety features to prevent de-tonation from any cause during normal transportation, handling, assembly, loading, and launching of the rocket. Design requirement stipulate that the fuze be detonator safe, that is, the explosive chain must be interrupted, so that if the detonator is prematurely initiated while the fuze is in the unarmed condition, the booster of the fuze and hence the explosive filler of the head will not be detonated. This is accomplished by interrupting the explosive train between the detonator and booster. The arming process in a fuze consists essentially in the alignment of these components. Ordinarily it is endeavored to have at least two independent safety features to prevent functioning before and during the initial stages of flight.

Reference to the applicable specification for each fuze will be required to ascertain the specific tests required for production lots of fuzes.

The first three tests listed below are tests which are considered to be more severe than conditions encountered during normal shipment and handling. After the tests the fuzes are disassembled and examined for evidence of functioning of explosive compo-nents, and any dangerous condition arising from dearangement of parts or missing parts.

1. A drop test, requiring that fuzes assembled in inert loaded heads be dropped (usu-ally 40 feet) on nose, side, and base onto armor plate.

2. A jolt test, requiring that fuzes be mounted in a fixture in a standardized test ma-chine and subjected to 1,750 drops in each of various positions from a height of 4 inches onto a leather-covered anvil.

3. A jumble test, requiring that fuzes be placed in a closed rectangular box mounted in a machine which revolves the box around one of its long diagonals at 30 rpm, for 3,600 revolutions.

4. A vibration test (simulation), requiring that fuzes be subjected to a simple harmo-nic vibratory motion parallel and perpendicular to the fuze axis when packed in the shipp-ing containers as well as when assembled in a rocket head or suitable test fixture. The duration of test covers a period of 24 hours at frequencies aranging from 700 to 3000 cycles per minute and amplitudes varying from  0.030 to 0.009 inch. The purpose of the test is to  determine whether or not the fuze is capable of withstanding transportation vibration without damage.

5. Various other tests may be specified at the manufacturing or loading plant to check arming spin, arming pressure etc.

Performance test are usually conducted on fuzes when assembled in loaded rounds to determine the overall functioning of the fuze. These tests present an opportunity to de-termine if the fuze functions as designed, and that it has been assembled and loaded in the proper manner. It also permits a check quality which may reveal any design and ma-nufacturing weaknesses. The details of acceptance tests of each fuze are stated in the individual fuze descriptions.

Installation and removal of rocket fuzes. In any operation involving fuzing, unfuz-ing, assembly, disassembly, cleaning, painting, etc., of all types of munitions, the work shall be accomplished in the most suitable location, taking into account safe removal from other explosives and possible damage to vital installation, and shall involve exposing the smallest number of rounds practicable. Only those persons actually essential for the work shall be in the vicinity. The ideal situation would be that where work would be per-formed on only one round at time, in a location on deck, remote from all magazines, from ready stowage, from other supplies of ammunition or explosives, and from vital installati-ons.

Use for lunbricants and preservaties. No lubricants or preservatives of any kind shall be used on any fuzes unless so indicated.

Reports of malfunctionings. Fuze malfunctions or any difficulties encountered with fuzes should be reported to the Bureau of Ordnance. The report should contain all perti-nent information concerning the fuze such as mark and mod number, lot number, manu-facturer, date of production, etc., together with the detals and description of the con-ditions.