Objective This study investigates the motion characteristics of deep-sea vehicles during deep vertical transit under vectored propulsion.

Method First, the motion equations were established to obtain preliminary solutions for the parameters of helical diving. Subsequently, a series of lake trials were conducted using a vectored-propulsion deep-sea vehicle prototype, including steady-state turning diameter tests, heeling angle measurements, and powered helical diving experiments under multiple control parameters, in order to analyze the diving motion characteristics. Finally, a 3650 m powered diving test was performed under real operating conditions at a depth of 3700 m in the South China Sea.

Results The lake trial results show that the steady turning diameter of the vector-propelled deep-sea vehicle is only 4 times the overall length of the platform, while the turning heel angle remains within 2.5°. The sea trial results indicate that, under the selected control parameters, the average deep-sea diving speed reaches 0.6 m/s, the standard deviation of the pitch angle is only 0.42°, and the horizontal offset during the 3650 m diving process is 442 m. These results demonstrate stable and controllable motion characteristics, verifying the feasibility of the powered diving technology for deep-sea vehicles based on vectored propulsion.

Conclusion  The results provide a reference for the research on diving technologies for deep-sea vehicles.