Final Design

The Acoustic Modem Integration onto Wave Glider USV project successfully developed a robust, modular, and hydrodynamically optimized pressure vessel (PV) to enhance underwater communication. The PV is constructed from anodized aluminum for strength and corrosion resistance, with Aluminum 7075-T6 endcaps for additional durability. A 3D-printed ASA plastic hydrodynamic dome reduces drag, improving energy efficiency at speeds of 1.4 - 3.7 km/h. Internally, a strong-back and bulkhead system organizes the ROAM electronics, which include the modem PCB stack-up, relay controller, power distribution blocks, and a high-capacity LiPo battery. The PV also features custom transducer mounts and waterproof external connections, ensuring seamless integration with the Wave Glider's tow cable and acoustic array.

To confirm the PV’s reliability, extensive hydrostatic pressure testing was conducted per ISO 21173 & ASME BPVC V, verifying its waterproofing and structural integrity at depths beyond the required 350 meters. FEA analysis demonstrated a maximum stress of 54.4 MPa at 1000m depth, achieving a factor of safety (FS) of 3. Sealing tests validated the O-ring and machined endcap integrity, while CFD simulations confirmed the drag-reducing effects of the hydrodynamic dome. These enhancements improve the Wave Glider’s signal transmission, reduce operational costs, and minimize environmental impact, making this integration a cost-effective, sustainable, and scalable solution for autonomous naval operations.

Analysis:
Sealing Test: Verified O-ring and machined end cap integrity by reducing pressure to 0.050MPa and holding for 15 min.

Hydrostatic Test: Per ISO 21173 & ASME BPVC V.

• 1.75MPa (50%) - 10 min

• 3.51 MPa (100%) – 10 min

• 4.39 MPa (125%) – 10 min

Hydrodynamic Analysis: Adding a hemispherical dome significantly reduces drag in underwater conditions at depths of 350m. The analysis was conducted using theoretical calculations based on empirical drag coefficient data and the drag force equation, comparing the vessel’s performance with and without the dome. At flow speeds between 0.8 - 2.0 knots (0.41 - 1.03 m/s), the dome achieves an estimated 81.7% reduction in drag, lowering the force from 2.59 N to 0.47 N at lower speeds and from 16.32 N to 2.98 N at higher speeds. This improvement enhances energy efficiency, reduces operational resistance, and optimizes the vessel's performance for autonomous underwater applications.