of approximately 40 feet and 55 feet. These wavelengths are very close to 

 the maximum that can be generated in the facility. The results of these 

 tests are tabulated in Table 1. 



Free oscillation of the model in pitch indicated that the resonant 

 period of the model (4.45 seconds at 5 feet depth and 4.3 seconds at 10 

 feet depth) was much larger than the wave periods that could be generated 

 in the facility. Consequently, to explore model behavior at a resonant 

 condition, the dynamic characteristics of the model were altered as 

 indicated previously. Tests were conducted on the altered model at 5 feet 

 below the undisturbed free surface in a variance of wavelengths spanning 

 the new resonant period in pitch (2.26 seconds). The results of these 

 tests are presented in Table 2. 



FULL SCALE PREDICTIONS OF MARK 56 AND 5 7 MINES 



We shall now present a theoretical comparison of the pitch response 

 of the MARK 56 and 57 mines. Pertinent data are as follows: 







MARK 56 



MARK 5 7 



Length 



inches 





89.8 



101.8 



Diameter 



inches 





23.4 



20.8 



Weight 



pounds 





975 



1,040 



^CG 



inches 





55.2 



68.0 



I 



inches 





27.6 



24.1 



g I 



pounds square 



inches 



**3,550,000 



**5,607,000 



if 



cubic inches 





* 33,900 



32,600 



Displacement, sea water 



pounds 





* 1,250 



* 1,210 



T, sea water 



pounds 





275 



170 



?CB 



inches 





* 44.0 



* 56.9 



g I ^ sea water 



pounds square 



inches 



3,030,000 



4,860,000 



Bare hulls, without appendages. 



Based upon assumed radius of gyration about the center of gravity 

 of 0.272 L, measured on the MARK 56 aluminum model. 



10 



