114 MARINE SCIENCE 



Slide No. 36. Missile launching sub : The third major reason for 

 exploring this new frontier is a military one. Emphasizing the 

 urgency ui this area, a report of the National Academy of Sciences 

 states — 



from the point of view of military operations there is no comparison between 

 the urgencies of the problems of the oceans, and those of outer space. The 

 submarine, armed with long-range missiles is probably the most potent weapon 

 system threatening our security today. It seems clear that the pressures of 

 establishing effective bases and of protecting ourselves from attack are relent- 

 lessly driving us into the oceans. 



Slide No. 37. N&ivtilus: The submarine Nautilus marked the 

 beginning of a tactical revolution at sea. Because of the fantastic 

 ability of the modern, nuclear submarine, both submarine and anti- 

 submarine tactics are being completely rewritten. 



With these new capabilities, also come new problems, both in making 

 our own submarines completely effective, and in defending against 

 similar types which we may expect the enemy to possess in the near 

 future. 



Slide No. 38. Sub in sea depth : The world beneath the sea is the 

 operating area of the true submarine. Information about this en- 

 vironment, previously of little consequence to surface ships and air- 

 craft, assumes tremendous importance to the submariner. Although 

 the seas cover three-fourths of the surface of the earth, less than 1 

 percent of the deep sea floor has been mapped with any degree of relia- 

 bility. 



The tasks of navigating a submarine at high speed and deep sub- 

 mergence without accurate bottom information can be compared with 

 driving a 10-ton truck on the freeway blindfolded. 



Slide No. 39. U.S.S.R. sub : On the other side of the coin, we must 

 be able to defend our cities and our merchant convoys against the 

 threat of the world's largest submarine fleet. Current estimates of 

 Soviet submarine strength run from four to five hundred. They are 

 rapidly replacing the older units with modem ones. It is reasonable 

 to assume that a number of these new submarines will be equipped 

 with long-range ballistic missiles. 



Slide No. 40. Submerged submarine : The problem of locating and 

 identifying enemy submarines at distances beyond the effective range 

 of their weapons is a difficult one. To date the most effective means 

 of locating and identifying submerged targets is by use of sound 

 techniques, called sonar. These tecliniques involve echo ranging, that 

 is, bouncing a sound beam off' a submerged target, or, listening to the 

 noises made by the target. 



Slide No, 41. Thermal layer: But in water, sound transmission 

 varies with changes in the temperature, density and salt content of 

 the w^ater. Temperature differences between water layers present the 

 most critical problem, for the sound beam is reflected or refracted 

 to a varying degree. 



Slide No, 42. Steamship and whale : Once a submerged object has 

 been detected by the sonar beam, the problem becomes one of identi- 

 fication — is it a whale ? School of fish ? Friendly surface ship ? Or 

 enemy submarine ? All give sonar reflections. 



Slide No. 43. Sea noises: In addition, when we listen for target 

 noises we discover that the ocean which has been characterized as a 

 "silent world" is, in fact, anything but. Actually the ocean is a "liquid 



