Support structure for manufacturing a pressure vessel

A method of manufacturing a pressure vessel comprising a section having a longitudinal axis, the section comprising a wall which extends around the longitudinal axis to define the boundary of a first sub-chamber, the section having a first end spaced apart from a second end along the longitudinal axis, the section being open at the first end to define a first opening to the first sub-chamber;

• the section being open at the second end to define a second opening to the first sub-chamber, wherein the pressure vessel is a submarine, the method comprising:
• supporting the wall with a support structure, the support structure comprising a first segment support structure and a second segment support structure, the first segment support structure nestable within, and moveable relative to, the second segment support structure, wherein the first segment support structure is configured to be raised and lowered relative to the second segment support structure to raise and lower the first segment support structure relative to a supporting substrate, the first segment support structure configured to move in a direction parallel to a longitudinal axis of the pressure vessel between a nested position within side walls of the second segment support structure to a position spaced apart from the second segment support structure across a surface of the substrate,
• wherein the first segment support structure is supported by the second segment support structure while the first segment support structure is in the nested position within the side walls of the second segment support structure.