17 
oped and successfully tested this system on the Blake Plateau in 750 
meters of water in 1970.° 
The system used by the Arbeitsgemeinschaft Meerestechnischge- 
winnbare Rohstoffe (AMR) group is also of the air-lift type. In the 
Deepsea Ventures and AMR systems the dredge head is towed across 
the bottom by the mining ship. Modifications of this method may in- 
volve a self-propelled bottom device such as a tracked crawler or a 
stationary unit with a rotating arm.® * 
| 
dl Mall JS.) UA lable Whe patiac me 
iene elt, eI, eros gat fn NEE 
Ficure. 9.—Research Vessel Deepsea Miner. A converted general cargo ship 
displacing 7,500 tons full load with an overall length of 320 feet. The major 
hull modification was the installation of a 20 foot by 30 foot long well (Moon 
Pool) slightly aft of midship. A 75 foot high derrick was installed to handle 
several thousand feet of 9¥%’’ drill casing. 
Courtesy : Deepsea Ventures, Inc. 
The efficiency of the air-lift system is not known. Since nodules 
larger than the system can support must be rejected, the efficiency on 
that basis alone would be lower than total size range recovery systems. 
The large factors of uncertainty, however, are how efficiently the 
dredge head can interact with the bottom and how tight a pattern of 
5 Covey, C. W. Ocean mining system completes tests. Under Sea Technology, October 
1970, p. 22-23, 28. 
®Sheary, G. W., and J. HB. Steele. Mechanical deep sea nodule harvester. United States 
Patent 3,480,326, November 1969. 
7 Smith, W. J. An assessment of deep-sea manganese nodule exploitation technology. 
Unpublished manuscript, Woods Hole Oceanographic Inst., 1972. 
52-273 O - 75 - 3 
