An articulated pipe‐miner system with thrust control for deep‐ocean crust mining

An articulated deep‐ocean pipe system with its bottom end free is described. The articulation reduces the stringent requirements on the buffer‐miner slant range, providing more freedom to the miner maneuvering on the seafloor. 2‐D deflection and 3‐D motions of a 5,486‐m‐long (18,000‐ft) articulated pipe system and buffer can be controlled with elastic joints, axial dampers, and the buffer at the bottom end of the pipe, and with thrusters installed along the pipe, controlling the lateral deflection and reducing the axial motion and stress of the pipe. Using the 3‐D nonlinear pipe code, 3DNLPIPE, previous analysis (Cheng & Chung, 1996, 1997) showed design and operation principles as follows. Arrangements of the axial vibration dampers at proper positions along the pipe, even without the joints, can effectively reduce the axial stress. Joints with proper stiffness can be arranged along the pipe to be effective in reducing the axial stress as well as bending moments. The best combination of the multiple elastic joints and the axial dampers along the pipe can control static, as well as mean dynamic, deflections, and reduce the axial stress, bending moments, and torsional deformation. Further, Chung et al. (1997) modeled the external thrust vectors along the pipe for additional control of the lateral pipe and buffer motion to keep them within the buffer‐miner slant range. The 5‐s axial resonance period of the present 18,000‐ft pipe is a very commonly encountered wave period in the ocean, and it can excite the axial pipe vibration.