An analysis of steady descending motion of a launcher of a compact deep-sea monitoring robot system

Analysis of steady descending motion of a launcher of a compact deep-sea monitoring robot system is presented. The system consists of a launcher and a vehicle that is stored in the launcher when it descends. Nonlinear equilibrium equations for steady descending motion from surface to seabed by gravity are presented. Model experiment for measuring hydrodynamic characteristics of a launcher model was carried out at a towing tank. Tank test data is analyzed based on the equilibrium equations. Descending posture, horizontal velocity and duration for reaching a target point are calculated based on the tank test data. Calculation reveals that horizontal velocity can take either positive or negative value depending on length between center of buoyancy and center of gravity. It is also found that maximum rudder angle does not always produce maximum horizontal velocity. Effect of fins and rudders area and interaction effect of two pairs of rudders are also clarified. Such kind of stuck of information obtained by calculation for steady descending motion is beneficial for the best configuration for fins and rudders from a hydrodynamic point of view.