SPAR Based Maritime Access Vehicle

Abstract

The invention relates to a spar based vessel for accessing offshore installations and vessels, including wind farm turbines, in which the centre of gravity of the vessel is positioned below the centre of buoyancy, which is positioned below the operational waterline, the operational waterline occurs at low cross-sectional area vertical struts, and the vertical struts support a topside structure for passengers. Active ballast control system and location of the propulsive elements permits the vessel to travel in spar orientation by positioning the vector of propulsion to lie in the same horizontal plane as the transverse centre of drag of the vessel. A docking system permits safe connection of the vessel to offshore installations, including wind turbines of generic design.

1 . A vessel for transporting loads over water, comprising:
 a. One or more forward propulsive elements for propelling the vessel in a longitudinal direction;   b. A hull having an underwater buoyancy chamber, a keel connected below the buoyancy chamber, and one or more vertical struts extending above the buoyancy chamber to connect the hull to a topside structure;   c. The hull and the topside structure, together with a permitted range of loads on the topside structure and ballast in the buoyancy chamber, defining a range of centers of gravity for the vessel;   d. in which, for a range of operational waterline positions of the vessel along the one or more vertical struts, the range of centers of gravity is located below a range of centers of buoyancy for the vessel determined by the range of operational waterline positions.   
     
     
         2 . The vessel of  claim 1  in which the one or more vertical struts have a maximum water plane area which is less than the average cross sectional area of the buoyancy chamber. 
     
     
         3 . The vessel of  claim 1  in which the one or more vertical struts have a maximum water plane area which is less than 25% of the average cross sectional area of the buoyancy chamber. 
     
     
         4 . The vessel of  claim 1  in which each of the one or more vertical strut has a maximum water plane area less than 15% of the average cross sectional area of the buoyancy chamber. 
     
     
         5 . The vessel of  claim 1  in which the keel comprises a keel strut hydro-dynamically shaped as a foil for movement in the longitudinal direction and a keel bulb hydro-dynamically shaped as a tube for movement in the longitudinal direction. 
     
     
         6 . The vessel of  claim 1  in which the buoyancy chamber is hydro-dynamically shaped as a tube for movement in the longitudinal direction for movement in the longitudinal direction. 
     
     
         7 . The vessel of  claim 1  in which the vertical struts are hydro-dynamically shaped as foils for movement in the longitudinal direction. 
     
     
         8 . The vessel of  claim 1  in which the hull is hydro-dynamically shaped for movement in the longitudinal direction. 
     
     
         9 . The vessel of  claim 1  in which for a range of expected heights for drag force vectors on the vessel defined by the range of operational waterline positions, a net forward propulsive force generated by the one or more forward propulsive elements is applied at substantially such range of expected heights. 
     
     
         10 . The vessel of  claim 9  in which there is one forward propulsive element positioned at an expected value for the height of a net effective drag force vector on the vessel for a predetermined operational waterline. 
     
     
         11 . The vessel of  claim 9  in which there is at least one forward propulsive element positioned above the range of expected heights for drag force vectors and at least one propulsive element positioned below the range of expected heights for drag force vectors, and a computer implemented dynamic thrust controller causes the net forward propulsive force to be positioned at a height equal to an estimated value for a current drag force vector determined by the computer implemented dynamic thrust controller. 
     
     
         12 . The vessel of  claim 1  further comprising an active ballast control system for controlling the volume or location or both volume and location of water and air in the buoyancy chamber. 
     
     
         13 . A vessel for transporting loads over water, comprising:
 a. One or more forward propulsive elements for propelling the vessel in a longitudinal direction;   b. A hull, hydro-dynamically shaped for movement in the longitudinal direction, having an underwater buoyancy chamber, a keel connected below the buoyancy chamber, and vertical struts extending above the buoyancy chamber to connect the hull to a topside structure;   c. the vertical struts having a maximum water plane area which is less than 25% of the average cross sectional area of the buoyancy chamber;   d. The hull and the topside structure, together with a permitted range of loads on the topside structure and ballast in the buoyancy chamber, defining a range of centers of gravity for the vessel;   e. in which, for a range of operational waterline positions of the vessel along the one or more vertical struts, the range of centers of gravity is located below a range of centers of buoyancy for the vessel determined by the range of operational waterline positions; and a net forward propulsive force generated by the one or more forward propulsive elements is applied at substantially such range of expected heights; and   f. an active ballast control system for controlling the volume or location or both volume and location of water and air in the buoyancy chamber.   
     
     
         14 . The vessel of  claim 13  in which there is one forward propulsive element positioned at an expected value for the height of a net effective drag force vector on the vessel for a predetermined operational waterline. 
     
     
         15 . The vessel of  claim 13  in which there is at least one forward propulsive element positioned above the range of expected heights for drag force vectors and at least one propulsive element positioned below the range of expected heights for drag force vectors, and a computer implemented dynamic thrust controller causes the net forward propulsive force to be positioned at a height equal to an estimated value for a current drag force vector determined by the computer implemented dynamic thrust controller.