can be by direct mechanical linkage (limited 

 to shallow depths owing to compression on 

 the hull with consequent size reduction of 

 thru-hull penetrations) or by hydraulics. 



Maneuverability 



The requirements for maneuverability 

 vary considerably in speed and degree, but 

 generally the vehicle is expected to be capa- 

 ble of controlled movement in the vertical 

 and horizontal. For many if not all missions, 

 the vehicle must be able to "hover" (dynami- 

 cally or statically) at a given depth or dis- 

 tance above the bottom. 



External Attachments 



For maximum mission adaptability, the ve- 

 hicle should have external attachment 

 points for installation of various instruments 

 or devices to conduct undersea tasks. Since 

 few, if any, of these instruments are stand- 

 ard in weight, size, shape, or mode of opera- 

 tion, a degree of flexibility in such attach- 

 ment points is desirable. In the probable 

 event that such devices will require electri- 

 cal power and/or control, provisions must be 

 made to furnish spare electrical connectors 

 and thru-hull penetrators. 



Lock-out/Lock-in 



If the submersible is designed for trans- 

 porting and supporting divers, provisions 

 must be made for ballasting the vehicle 

 when they leave (to restrain it from ascend- 

 ing) and deballasting when they return. 

 Hatches and viewports in the diver's com- 

 partment must be double-acting to resist not 

 only external pressures, but internal pres- 

 sures as well. Communications must be ar- 

 ranged between the diving compartment and 

 the unpressurized part of the pressure hull; 

 and, when surfaced, a means of providing 

 food or medical aid must be incorporated in 

 the design if decompression is required. 

 Whereas the egress/ingress hatch will be on 

 the keel of the submersible, and the vehicle 

 might be bottomed during diver operations, 

 space between the hatch and bottom must be 

 sufficient to allow easy access to the hatch. 

 Consideration must likewise be given to per- 

 sonnel transfer to a decompression chamber. 



Weight and Size 



The submersible's dry-weight (in air) and 



physical dimensions will govern the methods 

 of launch and retrieval as well as the size of 

 its support ship and the methods available to 

 it for land and air transport. 



Payload 



There are no minimum or maximum pay- 

 load standards, and they range from less 

 than 100 pounds to several tons. The larger 

 the payload requirements, the larger the ve- 

 hicle size and, correspondingly, the greater 

 the necessary support efforts become, with 

 resultant lowered mobility. Trade-offs are 

 possible whereby a non-essential manipula- 

 tor, for example, might be replaced with an- 

 other instrument or a lock-out chamber re- 

 placed with a different module for a particu- 

 lar dive. Distribution of payload weight and 

 balance must be considered to assure that 

 vehicle trim and control are not jeopardized. 



HUMAN CONSIDERATIONS 



Respiration 



Oxygen must be supplied, and carbon diox- 

 ide must be removed for the duration (6-12 

 hr) of a normal dive and for an extended 

 period in the event of an emergency. Moni- 

 toring devices must be included to maintain 

 proper levels and to check for the presence of 

 contaminants. In the event of diver support, 

 storage and supply of air or mixed gas {e.g., 

 helium/oxygen) must be accommodated. 



Temperature/Humidity 



In shallow tropical dives, temperatures 

 (°F) and relative humidity (%) reach into the 

 90's; with depth, or in the high latitudes, the 

 temperature can fall into the 40's with a 

 corresponding humidity decrease. Both these 

 extremes bear heavily on human perfor- 

 mance and must be dealt with successfully. 

 Deep diving in the tropics can combine both 

 extremes and includes condensation on the 

 interior walls of the hull with consequent 

 drippage; this can be detrimental to equip- 

 ment as well as to human occupants. 



Food/Water 



Normal and emergency food and water ra- 

 tions must be carried; limited power or the 

 possibility of its entire loss restricts the type 

 of food and preparation possible. 



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