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The underwater glider has difficulty accessing the complex and narrow hadal trench for observation, which is affected by its limited regulation capability of pitch angle (−45°~45°). In this study, a compact attitude regulating mechanism is proposed to extend the regulation range of pitch angle from −90°to 90° and to install it on the hadal-class underwater glider Petrel-XPLUS. Subsequently, the dynamics model of Petrel-XPLUS is established using dual quaternions to solve the “gimbal lock” problem caused by the increased pitch angle range. Within the extended pitch range, the motion modes of the glider are enriched into long-range, virtual mooring, and Lagrangian float modes for long-range, small-area, and current-following observation missions, respectively, and are analyzed using the established dynamics model. Moreover, a ballast method was used to modify the pitch angle range and initial equilibrium state of a constructed underwater glider. Finally, Petrel-XPLUS achieved a pitch angle regulation range of −90°~90° in a water pool experiment and completed three consecutive profiles in a sea trial in the Challenger Deep, Mariana Trench, with all depths over 10,000 m, of which the maximum depth was 10,619 m. The proposed mechanism and methods can also be applied to other submersibles to facilitate ocean observations.

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Engineering ceramics have extremely high values for both specific modulus and specific compressive strength, making them one of the most promising materials for enhancing the carrying capability of full ocean depth (FOD) submersibles. However, due to the low tensile strength of most ceramic materials, the tensile stress generated at the contact surface of ceramic pressure housings under hydrostatic pressure may exceed the material’s limits and thus lead to cracking failure. Currently, there are no valid calibration methods for the tensile stress caused by material discontinuities at the contact surface. In this paper, an approximate model is established based on contact mechanics. The absolute error of the approximate model, as verified by the simulation results for nine groups of ceramic pressure housings, does not exceed 14.2%. It is also concluded that the smaller the difference in Young’s modulus between the ceramics and metals, the higher the tensile strength safety factor. In addition, two hydrostatic pressure experiments were carried out to further verify the results of the approximate model and the numerical solutions. The approximate model is oriented to the reliable design of ceramic pressure housings. It will play an important role in improving the carrying capacity and observation capability of FOD submersibles.