148 • Marine Minerals: Exploring Our New Ocean Frontier 



ate within stronger currents and at greater depths 

 than most ROVs can presently operate. 



Nonetheless, manned submersibles have several 

 drawbacks. Most industrial applications require 

 working around and within a structure where the 

 possibility of entanglement/entrapment is often 

 present and, consequently, human safety is poten- 

 tially in jeopardy. Manned vehicles that operate in- 

 dependendy of a surface-connecting umbilical cord 

 can operate for a duration of 6 to 8 hours before 

 exhausting batteries. Even with more electrical 

 power, there is a limit to how long human oc- 

 cupants can work effectively within the confines of 

 a small diameter sphere — 6 to 8 hours is about the 

 limit of effectiveness. Relative to ROVs, a manned 

 submersible operation will always be more com- 

 plex, since there is the added factor of providing 

 for the human crew inside. 



The two major advantages of ROVs are that they 

 will operate for longer durations than manned ve- 

 hicles (limited only by the electrical producing ca- 

 pability of the support ship) and that there is a lower 

 safety risk for humans. Towed ROVs, for exam- 

 ple, can and do operate for days and even weeks 

 before they need to be retrieved and serviced. The 

 many varieties of ROVs (at least 99 different 

 models produced by about 40 different manufac- 

 turers) permit greater latitude in selecting a sup- 

 port craft than do manned submersibles (which usu- 

 ally have dedicated support vessels). Many ROVs, 

 because of their small size, can access areas that 

 manned vehicles cannot. Because ROV data and 

 television signals can be relayed continuously to the 

 surface in real-time, the number of topside ob- 

 servers participating in a dive is limited only by the 

 number of individuals or specialists that can crowd 

 around one or several television monitors. Depend- 

 ing on the depth of deployment and the type of work 

 conducted, an ROV may incur only a fraction of 

 the cost of operating a manned submersible. 



Probably the most debated aspect of manned v. 

 unmanned vehicles is the quality of viewing the sub- 

 sea target. There is no question that a television 

 camera cannot convey the information that a hu- 

 man can see directly. Even with the high quality 

 and resolution of present underwater color tele- 

 vision cameras and the potential for three-dimen- 

 sional television viewing, the image will probably 



never equal human observation and the compre- 

 hension it provides. To the scientific observer, di- 

 rect viewing is often mandatory. For the industrial 

 user, this is not necessarily the case. Some segments 

 of industry may be satisfied with what can be seen 

 by television, and, while they would probably like 

 to see more, they can see well enough with tele- 

 vision to get the job done. The distinction between 

 scientific and industrial needs is important because 

 in large part, it allowed the wide-scale application 

 of the ROV, which contributed to the slump in 

 manned vehicle use. 



Costs 



The cost of undersea vehicles varies as widely 

 as their designs and capabilities. One of the few 

 generalizations that can be made regarding costs 

 is that they increase in direct proportion to the ve- 

 hicle's maximum operating depth. 



Manned submersibles can cost from as little as 

 $15,000 for a one-person vehicle capable of diving 

 to 45 meters (150 feet) to as much as $5 million 

 for an Alvin replacement. A replacement for the 

 Johnson-Sea-Link , which is capable of diving to 

 over 900 meters (3,000 feet), would cost from $1.5 

 million to $2 million. These figures do not include 

 the support ships necessary to transport and deploy 

 the deeper diving vehicles. Such vessels, if bought 

 used, would range from $2 million to $3 million; 

 if bought new, they could cost from $8 million to 

 $10 million. 



ROVs also range widely in costs. There are 

 tethered, free-swimming models currently available 

 that cost from $12,000 to $15,000 per system, reach 

 depths of 150 and more meters, and provide video 

 only. At the other end are vehicles that reach depths 

 in excess of 2,400 meters, are equipped with a wide 

 array of tools and instrumentation, and cost from 

 $1.5 million to $2 million per system. Intermedi- 

 ate depth (900 meters/3,000 feet) systems equipped 

 with manipulators, sonars and sensors range from 

 $400,000 to $500,000. Most of the towed vehicles 

 presendy available are deep diving (20,000 feet) sys- 

 tems requiring a dedicated support ship and exten- 

 sive surface support equipment. Such systems start 

 at about '$2 million and can, in the case of the towed 

 hybrid systems, reach over $5 million. 



