LEARNING OBJECTIVE Discuss the composition and characteristics of service explosives and their use.

Service explosives as used in the Navy are varied and subject to periodic change. However, there are certain basic explosives that have become fairly standard throughout the Navy. A few of the more pertinent explosives and their uses are discussed in the following paragraphs.

BLACK POWDER

Black powder is the oldest explosive known. The ingredients in black powder include saltpeter (potassium nitrate or sodium nitrate), charcoal, and sulfur. It ignites spontaneously at about 300C (540F) and develops a fairly high temperature of combustion: 2300C to 3800C (4172F to 6782F).

The chemical stability of black power impractically unlimited when stored in airtight containers, but it deteriorates irregularly when exposed to moisture, which it absorbs readily. The term hygroscopic applies to explosives that easily absorb moisture.

Black powder is not affected by moderately high temperatures, and it is not subject to spontaneous combustion at ordinary stowage temperatures. It is highly flammable and very sensitive to friction, shock, sparks, and flame. When black powder is ignited, it is extremely quick and violent in its action.

The Navy classifies black powder into two types (potassium nitrate and sodium nitrate), depending on the chemical compound used in the base material. These two types are further divided into classes identified by numbers 1 through 9 for potassium nitrate-based black powder and by letters A through C for sodium nitrate-based black powder.

Uses of Black Powder

The range of use of black powder has decreased with the development of new chemical compounds but, where smoke is no objection, black powder is considered by many to be the best substance available for transmitting flame and producing a quick, hot flame.

Currently, black powder is used by the Navy for the following purposes:

Classes 1 through 9: JATO, rocket igniters, igniter pads, ignition ends for bag charges, primers, propelling charges for line-throwing guns, expelling charges for base-ejection shells, pyrotechnic items, relay pellets, igniting charges for illuminating candles, charges in target practice shells, igniter charges in primer detonators, fuze-delay elements, tracer igniters, delay and igniter charges in primer detonators, practice hand grenade fuzes, and Navy squibs.

Classes A through C: Saluting charges, practice bombs, and torpedo impulse charges.

Black Powder as a Propellant

Black powder as a gun propellant has several disadvantages: (1) it leaves a large amount of residue, (2) it produces large quantities of smoke, (3) it causes rapid erosion of the gun bore, and (4) its velocity of reaction is too rapid. For these reasons and the fact that black powder charges do not provide the reproducible results required of modern guns, it was abandoned as a propellant around 1888. This abandonment was hastened by the development of NC.

NITROCELLULOSE (NC)

NC was first prepared in 1838. However, two main problems had to be solved before it could be used as a gun propellant. First, the velocity of the explosion had to be reduced so that the charge weight required to propel the projectile would not shatter the gun tube. second, the density had to be increased so that a given charge weight would pack into a reasonable space. The first problem was solved in part by igniting NC instead of firing it with a detonator. The solution to the second problem actually solved both. In 1886, Vielle first colloided or gelatinized NC with alcohol and ether and, thus reduced the burning rate to acceptable levels. The procedure significantly increased the loading density of NC, establishing it as the foundational element in gun propellants used through the present day. Further developments resulted in materials that could be added to improve stowage qualities, reduce or eliminate flash, reduce hygroscopicity, reduce flame temperature, and even increase the propellant force or impetus.