Stealth and Detection Avoidance Strategies

For Underwater Unmanned Vehicles (UUVs):

A Technical Analysis

Ian Y.H. Chua

1, 2, 3, 4

27 February 2025

Abstract

Underwater Unmanned Vehicles (UUVs) and submarines are pivotal in modern naval

warfare, primarily relying on stealth to perform reconnaissance or oensive operations.

This paper explores advanced technologies and strategies used by underwater assets to

remain undetected by surface vessels. It details the methods used for acoustic and non-

acoustic stealth, calculates the maximum undetectable size of a UUV at various

detection ranges, and estimates the typical maximum speed of these vehicles based on

their size. Comprehensive tables, calculations, and real-world acoustic models are

provided for practical understanding.

1. Introduction

Naval warfare increasingly depends on stealthy underwater platforms like UUVs and

submarines. These assets must avoid detection by advanced Anti-Submarine Warfare

(ASW) systems employed by surface vessels, which use a combination of acoustic,

magnetic, and optical sensors. This paper delves into strategies employed to evade

detection and quanties the maximum UUV size that remains undetectable at specic

ranges while estimating corresponding maximum speeds.

2. Detection Methods Used by Surface Vessels

Surface vessels employ various detection technologies:

• Acoustic Detection: Active and passive sonar systems detect underwater

targets by analyzing sound reections and emissions (Urick, 1983).

• Magnetic Anomaly Detection (MAD): Identies disruptions in Earth's magnetic

eld caused by metal hulls (Blasch et al., 2019).

• Infrared and Optical Sensors: Detect periscopes or heat signatures near the

surface (Lynch, 2004).

• Satellite and LIDAR Systems: Provide detection capabilities for near-surface

targets (Kerr, 2020).

3. Stealth Strategies for Underwater Assets

3.1 Acoustic Signature Reduction

• Anechoic Coatings: Rubber tiles absorb incoming sonar pulses (Everley, 2017).

• Quiet Propulsion Systems: Pump-jet propulsors and electric drives reduce

noise (Ouyang & Chen, 2016).

• Machinery Isolation: Limits vibrations transferred to the hull (Horne, 2000).

3.2 Environmental Exploitation

• Thermoclines and Haloclines: Layers of diering temperatures and salinity

refract sonar waves, creating shadow zones (Williams, 2001).

• Seabed Topography: Navigating near ocean trenches or ridges can obstruct

sonar detection (Makris & Dushaw, 1998).

3.3 Electronic and Acoustic Countermeasures

• Acoustic Decoys: Emit sounds mimicking submarine signatures to confuse

sonar (Johnson & Smith, 2014).

• Towed Countermeasures: Devices deployed to deect or absorb sonar pulses

(Zhao & Hu, 2018).

3.4 Non-Acoustic Signature Management

• Magnetic Signature Reduction: Degaussing coils minimize magnetic detection

(Patel & Ghosh, 2015).

• Wake and Bioluminescence Reduction: Controlled slow movements prevent

visible water disturbances (Reuter & Fischer, 2021).

4. Calculations of Maximum UUV Length and Speed at Various Detection Ranges

4.1 Sonar Equation and Acoustic Modeling

The active sonar equation is used to estimate the maximum UUV size that remains

undetectable:

Units and Denitions:

• SL (Source Level): Measured in decibels (dB) relative to 1 μPa at 1 meter.

Represents the sound intensity emitted by the sonar source. Chosen value: 210

dB, typical for mid-frequency active sonars used in naval applications (Urick,

1983).

• TL (Transmission Loss): Measured in decibels (dB). Describes the reduction in

acoustic signal strength as it propagates through water.

• TS (Target Strength): Measured in decibels (dB) relative to 1 m². Quanties how

much sound a target reects back toward the source.

• NL (Noise Level): Measured in decibels (dB) relative to 1 μPa. Represents the

ambient ocean noise level. Chosen value: 85 dB, a common estimate for

moderate sea states (Lynch, 2004).

• DT (Detection Threshold): Measured in decibels (dB). Denes the minimum

signal-to-noise ratio required for reliable detection. Chosen value: 10 dB,

representing standard sonar operator thresholds.

• SNR (Signal-to-Noise Ratio): Measured in decibels (dB). Chosen value: 0 dB,

used to model marginal detection conditions.

Result: A UUV with a maximum length of 0.25 m remains undetectable at 200 m,

traveling at approximately 0.34 m/s.

Following the example calculations above, the Maximum UUV Length and Maximum

Speed can be obtained for various Detection Ranges, as shown in Section 5.

6. Conclusion

This paper analyzed methods used by underwater assets to avoid detection by surface

vessels, emphasizing acoustic stealth and environmental exploitation. Calculations

revealed that smaller UUVs, such as those under 0.25 meters in length, can remain

undetectable at close ranges (200 m), with corresponding low maximum speeds.

Conversely, as the detection range increases, the permissible UUV size grows, allowing

for higher operational speeds.

Acknowledgments

This paper was developed with the assistance of ChatGPT 4.0, which provided insights and renements in the

articulation of philosophical and scientic concepts.

Founder/CEO, ACE-Learning Systems Pte Ltd.

M.Eng. Candidate, Texas Tech University, Lubbock, TX.

M.S. (Anatomical Sciences Education) Candidate, University of Florida College of Medicine, Gainesville, FL.

M.S. (Medical Physiology) Candidate, Case Western Reserve University School of Medicine, Cleveland, OH.

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