Booster explosives are those components of the explosive train that function to transmit and augment the force and flame from the initiating explosive. They ensure the reliable detonation or burning of the main burster charge or propellant charge. Propelling charges use a black powder booster, while high-explosive boosters use one of the following: Tetryl, CH-6, or Composition A-5.
Tetryl is a fine yellow crystalline material. When tetryl is heated, it first melts, then decomposes and explodes. It burns readily and is more easily detonated than explosive D.
CH-6 is a mixture of 97.5% RDX (described in the next section), 1.5% calcium stearate, 0.5% polyisobutylene, and 0.5% graphite. It is a finely divided gray powder that is less toxic and more available than tetryl.
Composition A-5 is a mixture of 98.5% RDX and 1.5% stearic acid.
MAIN-CHARGE (BURSTER) EXPLOSIVES
There are several high explosives currently used by the Navy as fillers for gun projectiles. The principal explosives are Composition A-3, RDX, and explosive D. These explosives, when combined in various percentages and combinations, produce numerous high explosives with varying degrees of sensitivity, brisance, rate of detonation, and other pertinent characteristics. These principal explosives, and some of their more common derivative explosives, are discussed in the following paragraphs, as well as some explosives that are no longer being used but may still be in some ammunition stocks.
TNT is a crystalline substance. The importance of TNT as a military explosive is based upon its relative safety in manufacture, loading, transportation, and stowage, and upon its explosive properties. Manufacturing yields are high and production relatively economical. The chemical names for TNT are trinitrotoluene and trinitrotol. Other (commercial) names are Trilite, Tolite, Trinol, Trotyl, Tritolol, Tritone, Trotol, and Triton.
TNT is toxic, odorless, comparatively stable, nonhygroscopic, and relatively insensitive. When TNT is pure, it is known as grade A TNT and varies from white to pale yellow. When the proportion of impurities is much greater, the color is darker, often brown, and the chemical is known as grade B TNT. It maybe ignited by impact, friction, spark, shock, or heat. TNT does not form sensitive compounds with most metals. The melting point varies between 80.6°C for grade A (refined TNT) and 76°C for grade B (crude TNT). TNT does not appear to be affected by acids but is affected by alkalies (lye, washing soda, and so on), becoming pink, red, or brown, and more sensitive. It is practically insoluble in water, but soluble in alcohol, ether, benzene, carbon disulfide, acetone, and certain other solvents. The velocity of detonation is approximately 22,300 fps.
Exudate has been known to separate from cast TNT. It may appear pale yellow to brown and may vary in consistency from an oily liquid to a sticky substance. The amount and rate of separation depend primarily upon the purity of the TNT and, secondarily, upon the temperature of the stowage place. Grade B (low-melting point) TNT may exude considerable liquid and generate some gas. This exudation is accelerated with an increase in temperature.
Pure TNT will not exude since exudate consists of impurities that have not been extracted in the refining process. Exudate is a mixture of lower melting isomers of TNT, nitrocompounds of toluene of lower nitration, and possible nitrocompounds of other aromatic hydrocarbons and alcohols. It is flammable and has high sensitivity to percussion when mixed with absorbents. Its presence does no appreciable harm to the stability but somewhat reduces the explosive force of the main charge. In some ammunition, an inert wax pad is used in the loading operation, and, in some cases, waxy material may ooze from the case. It should not be confused with the TNT exudate previously described. This material should, however, be tested for TNT to confirm its actual composition,
TNT exudate, when mixed with a combustible material, such as wood chips, sawdust, or cotton waste, will form a low explosive that is highly flammable and ignites easily from a small flame. It can be exploded in a reamer similar to a low grade of dynamite, but the main danger is its fire hazard. Accumulation of exudate is considered a great risk of explosion and fire. Its accumulation should always be avoided by continual removal and disposal as it occurs. While TNT is no
longer used in Navy gun ammunition, some 3"/50, 40-mm, and 20-mm stocks loaded with TNT may still be in the inventory. These stocks should be identified and checked periodically for the presence of exudate.
The exudate is soluble in acetone or alcohol. One of these solvents (requiring adequate ventilation) or clean, hot water should be used to facilitate removal and disposal of the exudate.
Under no circumstances should soap or other alkaline preparations be used to remove this exudate. The addition of a small amount of hydroxide, caustic soda, or potash will sensitize TNT and cause it to explode if heated to 160°F.