PHASE 1— DESIGN OF NEMO CAPSULE 



As mentioned previously, Piccard's concept 1 was selected for the 

 design of the capsule. However, since he described his concept only in very 

 general terms, considerable detailing of his concept was necessary during 

 the engineering design phase to insure the end product would be an opera- 

 tionally satisfactory capsule. Major omissions in the concept as stated by 

 Piccard were: ( 1 ) the method for attaching the capsule to the submersible, 

 (2) the method for incorporating electric and hydraulic feedthroughs in the 

 capsule, (3) the method for attaching equipment to the capsule's interior, 

 and (4) the method for fabricating the hull. In addition, some modifications 

 to his concept had to be undertaken to reflect current operational require- 

 ments for pressure- resistant capsules. 



General Design 



Four major specifications of Piccard's concept were not modified 

 and subsequently became the major constraints of the transparent capsule 

 design for NEMO. They called for use of (1 ) acrylic plastic, (2) a spherical 

 shape, (3) a monocoque stiffness system, and (4) structural modules in the 

 form of spherical pentagons which, when assembled, form a sphere. The 

 acceptance of these four general characteristics of the Piccard concept was 

 not due to a desire to adhere to the original concept, but because these four 

 characteristics reflect the results of an engineering optimization process in 

 the selection of material, shape, stiffeners, and fabrication process. 



For the continental shelf depth, acrylic plastic provided the most 

 economical transparent material for the development of a man-rated capsule 

 with satisfactory optical properties. Glass, although stronger in compression 

 than acrylic plastic, appeared to require at least five times as much funding 

 in order to obtain an operational man-rated capsule for continental shelf as 

 was required for acrylic plastic. 



Although there are many shapes for pressure-resistant hulls to choose 

 from and several methods of stiffening them against implosion, the sphere 

 remains the optimum shape. The monocoque hull design for stiffness is the 

 most economical one for construction of spheres. 11 



Many fabrication processes could be employed to fabricate a monocoque 

 acrylic plastic sphere, such as casting, drape forming, free forming, vacuum 

 forming, male and female die pressing, vacuum-assist female mold forming, and 

 others. The casting process could produce a hollow man-size,, monolithic, mono- 

 coque sphere if the required substantial investment in molds, casting equipment, 



