Remote control seafloor coring in the west Mariana basin

In July 1998, the BMS, a remotely operated seafloor coring system was successfully operated at 3 sites in a volcanic area near the western margin of the Pacific Ocean about 700 miles SE of Okinawa. These sites were located on the crest of a ridge, on a flat area near the base of the ridge and on a small knoll on the slope of the ridge and ranged in water depth from 1180 to 1950 meters. Coring depths from 4.2 to 8 meters were achieved. The core samples contained volcanic sediments (fine grained sand), sandstone, basaltic lava and hydrogenous ferromanganese oxide crust. Two of the sites had unconsolidated sediment cover and required the use of bore hole casing. The BMS uses rotary rod coring tools to collect core samples with a diameter of 44 mm to a depth of 20 meters. A rotary magazine holds up to 24 coring tools, consisting of core barrels, drill rod and casing. A variety of diamond and carbide bits can be used to allow coring in a variety of materials. Bore hole casing can be set to prevent hole collapse when coring through soft or unstable formations. The BMS is equipped with a wide variety of sensors, 5 video cameras and has 60 hydraulic functions, including joystick controlled thrusters for positioning prior to landing and telescoping legs for leveling on slopes. Data displayed to the operator from the onboard sensors provides real-time feed back from the coring process and coring function controls are provided that include proportional control of bit weight, bit speed, bit rotation speed and flushing water flow. Several coring operations that involve a number of repetitive steps, such as making up, breaking down and storing the drill tools are automated and controlled by the vehicle computer