1 of 1

Acoustic Modem Integration onto Wave Glider USV

Adem Evecek, Bryan Garcia, Kai Saucedo, Omar Salas, Thomas Dolby

Department of Mechanical and Aerospace Engineering

University of California San Diego

Sponsored by Naval Information Warfare Center (NIWC) Pacific

Overview: The Naval Information Warfare Center (NIWC) Pacific is currently utilizing Liquid Robotics Inc.’s (LRI) Wave Glider platform to implement its Persistent Unmanned Multistatic Sonar (PUMS) system for maritime surveillance operations. NIWC Pacific would like to integrate its new multi-modal RF, Optical, and Acoustic Modem (ROAM) system onto the existing LRI Wave Glider platform to expand undersea communications capabilities.

Challenge: Design, manufacture, and test a pressure vessel (PV) for ROAM electronics and transducers that achieves the following requirements:

functional at 350m while achieving a factor of safety (FS) of 3
Ergonomic removal, servicing, and replacement of internal ROAM electronics
Integrate mounting ports on the top and bottom of the PV for ease of modularity with existing hardware
Maintain acoustic signal quality for the ROAM modem through the positioning of the transducers

Moving forwards:

M27 Mount:

Design Optimization: Splitting the M27 mount into clamp and platform sections reduces material waste and machining time.
Welding: Provides a strong, permanent bond but may require post-weld machining.
Fasteners: Offer flexibility and easier maintenance, depending on structural and environmental needs.

M21 Mount:

CAD models and manufacturing process for production provided to sponsors for machining

External Connections on End Caps:

Shop drawings and manufacturing process provided to sponsors for machining the external connections onto the end caps
These connections will secure the pressure vessel to the wave glider.

Component Solutions

Analysis:

Sealing Test: Confirmed O-ring and end cap seal by applying a partial vacuum (0.050 MPa) for 15 min, with the gauge confirming no pressure drop^[1]

Hydrostatic Test: Per ISO 21173^[2] & ASME BPVC V^[3]

Drag Reductions: At 0.8 & 2.0 knots, 81.8% reduction.

Impact on society:

Economic Efficiency:

Reduced number of Wave Gliders for reconnaissance operations by improving acoustic messaging range
Reduces number of manned missions required to collect data

Environmental Sustainability:

Made of completely environmentally sustainable materials externally

Acknowledgement:

Our team would like to thank the following individuals for their support and guidance which allowed for this project to be possible:

Jerry Tustaniwskyj, Jackie Chen, Jackelin Amorin, Tom Chalfant, Stephen Mercsak, and Chris Cassidy for your technical design and manufacturing guidance.

Randall Plate, David Traganza, Jason Richter, and Kyle Swanson for their sponsorship along with their mechanical and electrical expertise.

Pressure Vessel:

Protects internal components
Provides a secure mounting interface
Made from anodized aluminum for durability and corrosion resistance

Hydrodynamic Dome:

Reduces drag
FDM 3D printed

in two halves

Mounted to end cap

around the S-Tow Cable

Internal Mounts:

FDM 3D printed assembly of

strong-backs & bulkheads

5 onboard ROAM electrics
Assembly fastened to Blue

Robotics PV Flange

Transducer Mounts:

M27 mid-frequency transducer has stainless steel clamp and custom protective cage
M21 low-frequency transducer has stainless mount and clamps

External Connections:

Custom top and bottom mounts to support forward tow-cable and rear tow-array
Rear waterproof connection piece between PV and tow-array
Helmer rod + O-ring to serve as waterproofing

References:

[1] “Using the Vacuum Plug and Hand Pump.” Blue Robotics, 28 July 2023, bluerobotics.com/learn/using-the-vacuum-test-plug/#testing-the-enclosure.

[2] International Standard ISO 21173, cdn.standards.iteh.ai/samples/70020/a017e02672584ebcb4ad3c3f94e89bc1/ISO-21173-2019.pdf.Accessed 10 Mar. 2025.

[3] American Society of Mechanical Engineers (ASME). BPVC Section V - Nondestructive Examination. ASME, www.asme.org/codes-standards/find-codes-standards/bpvc-v-bpvc-section-v-nondestructive-examination.

Figure 8: Internal Mounting Assembly

FEA at 350m:

Fluid Density: 1023.6 kg/m³
Gravity: -9.81 m/s²
Z-Displacement: 5m

Stress Results:

Max stress: 88.92 MPa

Safety Factor:

FOS: 2.81

Figure 1: Pressure Vessel Assembly

Figure 7: Dome Assembly

Test	Pressure (%)	Pressure (MPa)	Duration (min)
Test 1	50%	1.75	10
Test 2	100%	3.51	10
Test 3	125%	4.39	10

Figure 2, 3, & 4: Front Mount and Rear Male Connection

Figure 5 & 6: M21 & M27 Transducer Mounts

Pressure Vessel

Hydrodynamic Dome

Tow Array

M21 Transducer

Tow Array

M21 Transducer

M27 Transducer

Bottom Mount

Top Mount

Male Connector