1. The Sequence of Events in an 

 Underwater Explosion 



The purpose of this introductory chapter is to sketch briefly the 

 primary phenomena in an underwater explosion, in order to indicate 

 their order of occurrence and suggest the physical laws and properties 

 governing them. The discussion will appear superficial to those well 

 acquainted with the subject, but it is hoped that the description will 

 serve as an adequate outline and introduction^ for readers less familiar 

 with the field. 



1.1. The Initial Conditions 



An explosion is a chemical reaction in a substance which converts 

 the original material into a gas at very high temperature and pressure, 

 the process occurring with extreme rapidity and evolving a great deal 

 of heat. The temperature in the product gases is of the order 3,000° C. 

 and the pressure 50,000 atm. Any explosive material, whether solid, 

 liquid, or gas, is thus an inherently unstable compound which, once 

 started, undergoes chemical changes which convert it into a more stable 

 product. A reaction of this kind can be initiated if sufficient energy is 

 provided at some point in the explosive. This is done usually by means 

 of a heated wire or by frictional heat from impact by a firing pin, either 

 of which, in most cases, acts directly upon a small amount of especially 

 sensitive material. The reaction of this material then in turn initiates 

 the reaction in the main body of the explosive. 



Once initiated, the intense heat and pressure developed are suffi- 

 cient to set up the explosive reaction in adjacent material, and the reac- 

 tion is propagated through the material. The way in which the dis- 

 turbance proceeds depends upon the physical and chemical properties 

 of the material, and upon external physical factors such as the container 

 or surrounding medium, but two general types of behavior can be dis- 

 tinguished. The more important of these from the point of view of 

 destructiveness is the process of detonation, in which the chemical 

 transformation occurs so rapidly that it can keep up with the physical 

 disturbance resulting from the reaction. A reaction occurring in this 

 way develops a very narrow boundary between material in its initial 



1 An excellent introductory account of underwater explosions has been given by 

 Kennard (54), although much of the data on which the discussion is based has been 

 superseded by more recent results. Numbers in parentheses refer to the bibliography 

 on page 427. 



