Sub-ocean Drilling For the past 20 years, the National ...

Sub-ocean Drilling

For the past 20 years, the National Science Foundation(NSF) has been conducting a highly successful programinvolving exploration of Earth's crust by drilling beneaththe ocean floor and bringing up core samples. Theprogram's aims include substantiation and refinement ofthe plate tectonic theory, which holds that Earth'scontinents and oceans continuously change; determining

the impact of such changes on climate and oceancirculation; and establishing the geological framework inwhich natural resources are formed and distributed.

Last year, NSF initiated a new phase of exploration, a10-year effortmjointly funded by NSF and several majoroil companies--known as the Ocean Margin DrillingProgram (OMDP). Described as one of Earth's lastscientifically unexplored frontiers, the ocean margin isthe region of Earth's crust between the continental shelf

and the deep ocean abyss. Exploring it demands a shipwith capabilities beyond those of existing drillships; itmust drill in 13,000 feet of water to a depth 20,000 feetbelow the ocean floor. To meet these requirements, NSFis considering the conversion of the government-ownedmining ship Glomar Explorer to a deep ocean drilling andcoting vessel. Glomar Explorer is shown at left in itsmining ship configuration. Below is the ship' s large

'"moonpool"throughwhichdrillingequipmentcanbelowered:themoonpoolcanbeopenedorclosedtotheseabygateswhichslideonrailsalongthehullbottom.Thephotoaboveshowsthecomputercontrolcenterwheretechniciansmonitorunderseaoperationsandthe"dynamicpositioning"systemwhichautomaticallyholdstheshipinprecisepositionovertheworksite.

Thedecisiontoconverttheshipwasprefacedbyafeasibilitystudy,performedforNSFbyDonhaiserMarine,Inc.(DMI),Houston,Texas,anavalarchitect/engineeringfirmspecializinginservicestotheoffshorepetroleumindustry.Inthestudy,which

analyzedtheship'scharacteristicsforOMDPsuitabilityandevaluatedconversionrequirements,DMIusedacomputerprogramsuppliedbyNASA'sComputerSoftwareManagementandInformationCenter(COSMIC).WiththeCOSMICShipMotionandSeaLoadComputerProgram,DMIwasabletoperformanalysiswhichcouldnototherwisehavebeenaccomplished.Theanalysis,correlatedwithfullscaleseatests,confirmedGlomar Explorer's suitability.Engineering design work is under way and GlomarExplorer, if approved for conversion, is expected tobegin operations as a drillship in 1984.

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