General:

Two scales are employed to compare sensitivity of explosives. The first of these is the 'Laboratory Impact Sensitivity' in which the ratio of the drop of a given weight ne-cessary to detonate the explosive under discussion to the drop necessary to detonate TNT, is expressed on a percentage basis. TNT will be given as 100. The second is a scale of 'Bul-let Impact Sensitivity' with RDX rated at 0 and TNT at 100. The other explosives are ex-pressed in relation to these two. Velocity of detonation varies directly with the density to which the explosive is cast or pressed, (all other factors being constant). The velocity of detonation will, therefore, be given for a definite density of loading.

TNT: (Trinitrotoluol)

TNT is powerful, brisant, easy to load by casting since its melting point (Grade A) is 80.2 degrees C, stable under all stowage conditions, insensitive enough to stand all nor-mal handling, and should stand even bullet impact when cast. The Navy use it as booster in a pressed granular form in which it is more sensitive to detonator action.

The velocity of detonation is 22,300 ft/sec at a density of 1.55. Its Laboratory Im-pact Value is 100. Its Bullet Impact Value is 100. Color is Yellow to buff.

TETRYL: (Trinitrophenylmethylnitramine)

Tetryl, because of its combination of high power, brisance, and sensitivty, is the standard U.S. booster charge although the Navy still uses an apprecibale amount of gra-nular TNT. It has been tried for main charge loads in small caliber projectiles but has pro-ven too sensitive to withstand the set-back in all but 20 mm. It is used as a base charge in compound detonators which in effect makes it a small booster in intimate contact with the initiating explosive. The melting point of Tetryl (130 degrees C) is too high to allow it to be melted and cast. It is loaded by being mixed with small quanities of graphite or ste-aric acid which serve to lubricate it while it is being pressed into pellets. Tetryl is quite safe to handle and is extremely stable in stowage. Exposed or loose tetryl should not be handled as it may cause dermatitis.

The velocity of detonation is 24,400 ft/sec at a density of 1.55. Its color is light yel-low but it is usually gray because of the graphite. It is more powerful than TNT. Laborat-ory Impact Value is 45. Its Bullet Impact Value is 61.

EXPLOSIVE D: (Ammonium Picrate)

Explosive D is the standard main charge for armor piercing bombs and projectiles and all other Navy projectiles over 3". While its power and brisance ar slightly inferior to TNT it is much more insensitive to shock and will stand impact on armor plate without being de-flagrated. It has two other disadvantages: (1) Its melting point is too high for it ro be melted and cast and it is therefore loaded by being pressed into cases by a hydraulic ram; (2) It reacts with metal to form extremely sensitive copmpunds. This is counterac-ted by overing the interior of bombs or projectiles with acid proof lacquer.

Its rate of detonation is 21,300 ft/sec at a density of 1.48. Its power and brisance are about 95% that of TNT. Its Laboratroy Impact Value is 99. Its Bullet Impact Value is over 100. Its color is yellow or yellow-orange.

RDX: (Cyclonite Cyclotrimethylenetrinitramine)

RDX is the most powerful and brisant of the military high explosives, and it is consider-ed much too sensitive to use alone. It seems to be about half way between Tetryl and PETN in sensitivity. RDX is being used extensively in mixtures of other explosives and in-erts which reduce the sensitivity to a safe range, while the mixtures have a very high brisance and power due to the RDX. It has excellent stowage qualities but because of its sensitivity, it is shipped immersed in water like an initiating explosive. The velocity of de-tonation is 28,000 ft/sec at a density of 1.70. Its Laboratory Item Value is 34. Its Bullet Impact Value is 0. Its color is white.

PETN: (Pentaerythritetranitrate)

PETN resambles RDX in its characteristics. It is somewhat more sensitive but almost equal in power and brisance. It is appreciably more sensitive to percussion and impact than Tetryl and is, therefore, not used alone as a booster, though it is being used as a base charge in some compound detonators in the way Tetryl is. The tendency of PETN burn is much less than that of similar explosives. Its main use alone in the service is in primacord. When used alone, PETN is combined with a small quantity of wax to desensi-tize and lubricate it and is loaded by pressing. It is important to know that PETN in pri-macord is very insensitive to flame, shock, and friction, and therefore must be detonated by a cap.

The velocity of detonation of PETN is 26,000 ft/sec. The Velocity of detonation of pri-macord is 20,500 ft/sec. Its Laboratory Impact Value is 22. Its Bullet Impact Value, though not given, would be about equal to RDX (0). Its color is white.

HALEITE: (EDNA, Ethylenedinitramine)

Haleite is a new explosive that probably will not be used alone, but will be used in combination with other explosives. It is somewhat more powerful than TNT. Its sensitiv-ity is about the same as Tetryl. It melts at 180 degrees C but one report states that it may detonate in the same manner of an initiating explosive at that temperature or a little lower. If loaded alone it would be pressed. Its rate of detonation is 25,000 ft/sec at a density of 1.5. Its Laboratory Impact Value is 46. Its Bullet Impact Value is not available.