667 HYDROGRAPHIC MANUAL PaGE 624 



Handling of explosives shall be kept at a minimum. The handling of large 

 quantities of explosives and their stowage in the magazine shall be carefully supervised 

 by an officer who shall permit no relaxation of any safety measures. 



667. Detonators 



High explosives are fired by means of intermediate agents known as detonators. 

 These are small copper tubes, partly filled with a small charge of a powerfid explosive 

 which serves as a primer to detonate the principal explosive by a combination of shock 

 and intense heat. There are two general types of detonators; one that is set off by an 

 electric current, and another that is made for use with a fuse. The fuse detonators 

 are more commonly used in R.A.R. because they are more convenient, and with them 

 bombs may be fired from a moving vessel without an elaborate towing apparatus. 

 Electric detonators are sometimes used for experimental purposes (see 664). 



Fuse detonators are small copper cylinders, closed at one end, partly filled with a 

 charge of fulminate of mercury that is exploded by the train of sparks spit from a 

 burning fuse inserted into the open end. Detonators are manufactured in two 

 strengths, No. 6 and No. 8, the latter being the stronger. The No. 6 detonator is 

 1% inches long and contains 1 gram of explosive; the No. 8 is 1% inches long and con- 

 tains 2 grams of explosive; both have the same diameter, approximately % inch. 



Fulminate of mercuiy is a very sensitive and violent explosive; it is readily deto- 

 nated by friction, shock, sparks, or sulphuric or nitric acid. In its pure state it is only 

 slightly soluble in water, but in a mixture, as used in detonators, moisture is absorbed 

 readily and the sensitivity is decreased when it becomes damp. 



Electric detonators are exploded by the passage of an electric current that heats 

 and ruptures a wire bridge, which is inserted into the explosive charge, joining the two 

 conductor wires. They, also, are made of fulminate of mercury, and in the same 

 strengths as fuse detonators, i. e., No. 6 and No. 8. A number of different types of 

 electric detonators are manufactured, but only a special waterproof type is suitable for 

 use in water. The latter differs from other electric detonators in that it is made longer 

 to allow more space for waterproofing compound, and the wires are copper and are 

 coated with enamel so that if water penetrates the cotton insulation it cannot reach 

 the copper. Electric connections should be made at the tinned ends, but if the wires 

 have to be cut to shorten them, the enameled insulation as well as the cotton insula- 

 tion must be scraped off. Electric detonators may be obtained with wire leads of vari- 

 ous lengths from 4 to 20 feet, and longer lengths of wire may be obtained if ordered 

 specially. 



"When ordinary electric detonators are fired by a current of about 1.5 amperes, 

 there is a lag of 0.0073 second in the elapsed time from the application of the current 

 to the rupture of the wire bridge and an induction period (the elapsed time from the 

 rupture of the wire bridge to the explosion of the detonator) of 0.0069 second. The 

 sum of these is a lag of 0.0142 second between closing the circuit and detonation, which 

 is appreciable in experimental investigations. A special electric detonator (Du Pont 

 "SSS"), developed for seismic use, should be used for experimental purposes. In this 

 type of detonator the induction period is eliminated and the delay in rupture of the 

 bridge is reduced to 0.0035 second when a current of 1.5 amperes is used. Increased 

 amperage reduces the time delay considerably. 



All detonators must be stowed in a safe place, as far removed from the magazine 

 or the bomb locker on deck as convenient. They may be stowed in a watertight metal 



