132 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



rupture of the obstacle. This can not be accomplished except by the 

 passage of the projectile itself through the armor plate. If it is 

 sought to sweep away obstructions, the potential energy of the ex- 

 plosive charge carried by the projectile should be exercised at this 

 point. 



Inasmuch as a charge of explosive can not be projected to a great 

 distance without its being inclosed in a highly resistant metallic en- 

 velope, 1 it follows that in practice they will always produce simultane- 

 ously the destructive effects of the characters considered above. 

 Finally, one may consider the destruction of the personnel as a prin- 

 cipal purpose in the employment of shells charged with an explosive. 

 In this case one will seek to effect the rupture of the body of the shell 

 into a large number of fragments animated with the highest possiU e 

 initial velocity. In addition are the notable destructive effects pro- 

 duced by the shock of the explosion wave on the persons who are in 

 close proximity to the center of explosion. It is evident that endeavors 

 will be made to produce the one or the other of these effects. 



1. CHARACTERISTICS OF EXPLOSIVES. 



In order to secure the results of the study we propose it is expedient 

 to study these in detail. We recall at the outset certain elementa re- 

 views concerning the characteristics essential to explosives. 



In this regard an explosive is theoretically defined by certain data 

 the chief of which are its force, F, its potential, Q, and its rate of 

 detonation. The force is represented by the following expression. 



273 



in which p represents the atmospheric pressure (which is 1.033 kilos 

 per sq. cm.), V the volume, in liters at 0° C. and 760 millimeters of 

 pressure, of the gaseous products resulting from the explosion of 1 

 kilogram of the explosive, and T the absolute temperature of the 

 explosion. 



The potential, Q, represents the work corresponding to the in- 

 definite expansion of the above mass of gas. If E designates the 

 mechanical equivalent of heat and q the heat liberated by the ex- 

 plosion then 



Q=Eq Q . 



The rate of detonation is that of the propagation of the phenome- 

 non of explosion in traveling through a lead or tin tube filled with 

 the explosive under consideration. 



1 It will be otherwise if it be attempted to project the explosive charge by means of 

 rockets analogous to the old-fashioned war rocket. 



