162 • Marine Minerals: Exploring Our New Ocean Frontier 



Figure 4-15.— Conceptual Design for Deep Ocean 

 Rock Coring Drill 



An alternative and less expensive approach to using a large 

 and expensive drill ship for hard rock sampling is to use a 

 rennotely operated submersible drill which is lowered by ca- 

 ble from a surface vessel to the seafloor. (Not to scale). 



SOURCES:Williamson & Associates. Inc., and Sound Ocean Systems, Inc. 



rock corer was recently started by Sound Ocean 

 Systems & Williamson and Associates (figure 4- 

 15).'°^ This corer has not been built, but in con- 

 cept it is similar to the Bedford drill. A major differ- 

 ence is that it is designed to core continuously to 

 a depth of 53 meters (175 feet) (by adding core bar- 

 rels from a storage magazine). Alternatively, it can 

 be configured to recover 40 1.5-meter cores in a 

 single deployment. A workable system for obtain- 

 ing cores longer than 1 meter would be a signifi- 

 cant advancement. Both ODP and Bedford drillers 

 have experienced jamming beyond the first few 

 meters and have not been able to obtain longer 

 cores. 



Very little sampling of sediment-hosted sulfides 

 (e.g., in the Escanaba Trough off the coast of north- 

 ern California) has been attempted yet. Today's 

 percussion and vibratory devices rated for deep 

 water use probably will be suitable for shallow sam- 

 pling of sediment hosted sulfides but not for deeper 

 drilling. Additional problems may occur if the water 

 temperature is above 250 °C. Hot water could 

 cause a good core to turn to homogenized muck 

 as a sample is retrieved. Current technology also 

 is not capable of doing downhole sampling (e.g., 

 using a temperature probe) if the temperature is 

 above 250 °C. If the water temperature is above 

 350 °C, embrittlement of the drill string could 

 occur. 



^Fetters and Williamson, "Design for Deep-Ocean Rock Core 



Drill. 



NAVIGATION CONCERNS 



Technology for navigation and positioning is es- 

 sential in all marine charting and exploration work. 

 The accuracy required varies somewhat depend- 

 ing on the purpose, but, for most purposes, present 

 technology for navigating and for positioning a ship 

 on the surface is considered adequate. Most seafloor 

 exploration can be done quite well with local sys- 

 tems with internal uncertainties on the order of 10 



meters and uncertainties relative to global coordi- 

 nates of a kilometer or so. Use of a navigation sys- 

 tem that can position a ship within 1 kilometer of 

 a target would enable a ship to return to the im- 

 mediate vicinity of a survey area or mine site, for 

 example. Use of a system that could reliably posi- 

 tion one within 10 meters relative to local coordi- 

 nates (established, for example, by transponders 



