Page 619 radio acoustic ranging 662 



ship. The types of bombs differ only in the type of containers and in the method of 

 detonation. 



In the early development of R.A.K,., bombs were exploded electrically by closing 

 two switches, an ordinary electric switch located in the radio room and a safety switch 

 near the bombing station (see 6841). The bombs were towed about 200 feet astern of 

 the ship by a rope to which was attached a twin-conductor cable which carried the 

 current to explode the electric detonator. The bomb was suspended from a 5-gallon 

 can buoy and weighted with a 15-pound lead sinker. Although electric detonation is 

 a positive means of exploding bombs at any desired depth, it is no longer used in R.A.R., 

 except for experimental purposes when the exact time of the explosion must be recorded 

 (see 664). Electric bombs require excessive time to prepare, the survey vessel must 

 stop or slow down while they are fired, and it is difficult to keep track of whether the 

 two electric switches are open or closed. 



The types of bombs in general use are exploded by a fuse and a fuse detonator that 

 is inserted into the TNT through a suitable hole in the container. This type of bomb is 

 simple to construct and requires no preliminary preparations, and as soon as the fuse 

 is ignited the bomb is thrown overboard. 



662, Bomb Containers 



For best results a bomb container should be made of a rigid material so that the 

 detonation of the explosive will be complete before the container bursts. If the ex*- 

 plosive gases are thus restrained until the detonation is complete, the resulting explosion 

 produces a highly compressed sound wave that has a gi'eater range than one from an 

 explosion in a container that is easily shattered. Ordinary glass bottles, tin cans, and 

 special cast-iron spheres are used for bomb containers. 



Commercial glass bottles are satisfactory, except that in the required sizes they are 

 generally not well shaped for the purpose, and it is often difficult to insert the detonator 

 secm'ely. The cast-iron spheres are used on special occasions, but they are heavy 

 and expensive, for they must be specially cast in rather small quantities at foundries 

 which are often inconveniently located. Tin cans of various sizes are in general use 

 because they are inexpensive and they may be readily obtained. A better container is 

 desirable, however, and it is possible that a heavy glass sphere may be specially designed 

 for use as a bomb container. 



The iron spheres are usually cast with walls ji inch thick, with an outside diameter 

 of 7}2 inches, and with one flat surface about 2)4 inches in diameter on which they will 

 sit upright. They are provided with a hole suitably arranged so that a stopper with a 

 fuse hole may be inserted therein. A bomb of this design and size will contain about 

 4 pounds of explosive. A smaller cast-iron bomb of identical design is sometimes used. 

 It is only 4% inches in diameter and contains about 1 pound of explosive. 



The cans used for bomb containers are the ordinary commercial type with a friction 

 top; they need not be tinned if an untinned metal can is available and less expensive. 

 Various sizes are used depending on the characteristics of the area and the distance 

 from the receiving units. Three sizes are commonly used, of ji-, /2-, and 1-pint capaci- 

 ties, which will contain about %-, %-, and 1 -pound of explosive, respectively. A ^s-piut 

 size is occasionally used for very short distances but it is only a little more effective 

 than a detonator used alone. A quart size is also occasionally used for very long 

 distances but it is generally little more effective than the pint size. 



