of the hydrocopter. A power failure most certainly means an emergency 

 ascent of the entire vehicle, while cable entanglement could result in 

 jettisoning the personnel capsule and possible loss of the remainder of the 

 lift vehicle. 



A heavy-lift submersible using a hydrazine gas generator for displacing 

 water ballast was considered to be the most likely candidate of the three 

 possible submersible vehicles. Although capable of lifting 20-ton loads from 

 the sea floor and transporting them to new bottom sites, the heavy-lift NBTS 

 has only slight lateral thrust capability. Its propulsion system, unlike the one 

 aboard the hydrocopter, is dependent on an internal power source. However, 

 its internal power source means that the heavy-lift submersible is free from 

 the hazards created by long surface-to-vehicle conductors. Stirring-up of 

 bottom sediments, a problem endemic to the hydrocopter, is less likely to 

 be as serious with the submersible. Both vehicles would require a surface 

 support craft. Because of its greater weight and bulk, the hydrocopter's 

 support craft would be somewhat larger than that required for the 

 submersible. 



Further and far more detailed studies of both the hydrocopter and 

 submersible are necessary before deciding on the proper approach to a 

 workable NBTS. An important consideration, and one not discussed in 

 great detail here, is definition of the NBTS work mission. Proper mission 

 description must await further refinement and definition of DOT goals. As 

 discussed earlier, the NBTS is conceived as a work system for transporting 

 other, nonmobile work systems, portable nuclear power sources, and 

 anchorage systems, perhaps all of which are components of second or third 

 generation construction missions. The 20- or 30-ton lift requirement, 

 assumed here, is based on pure speculation as to the upper weight limit of 

 portable bottom loads. Lighter or heavier loads (also their bulk and sensitivity 

 to shock loading) will certainly be determining factors in the future selection 

 of near bottom transport vehicles. 



For the present, nothing more will be concluded except that either 

 a submersible or hydrocopter with a 20-ton lift capability is probably 

 possible within the present state-of-the-art. Such systems will be costly 

 initially (several millions of dollars), costly to operate (probably two or three 

 times as much as conventional deep-diving submersibles), and fraught with 

 certain operational hazards for both crew and vehicle. 



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