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Undersea Warfare


Programs in APL’s Undersea Warfare (USW) Mission Area support U.S. Navy and Joint missions, with the focus on the systems and technologies to defeat undersea threats and to project military power through effective undersea warfare operations. Our staff represents a broad set of skills and capabilities, from science and engineering to operations analysis. APL is nationally recognized for its expertise in submarine detection systems based on first principles of physics, as well as for our ability to build and test undersea prototype systems. We are a major test organization, conducting extensive, complex research and development operations at sea. As missions have changed over time, APL has continued to be a dependable partner with extensive knowledge of sponsor requirements and the experience to meet the challenges of today’s undersea warfare environment.

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APL has a significant record of contributions to critical undersea warfare challenges. Our submarine technology work spans more than four decades, from the emergence of the dangerously quiet Soviet SSN threat through today’s multiple challenges in the oceans of the world and the littoral operating areas. APL has been a lead organization for the Navy’s SSBN Security Program since its inception. From that core program, our work has expanded to a broader range of key roles and contributions in anti-submarine warfare and maritime technology; submarine technology; ocean engineering; maritime intelligence, surveillance, and reconnaissance (ISR); and sensor/system rapid prototyping.

The goal of the USW Mission Area is to strengthen our nation’s capabilities to defeat undersea threats and to conduct effective undersea warfare operations to project military power. We will achieve this goal by applying scientific, engineering, and operations analysis skills and experience, coupled with our knowledge of naval operations.

The USW Mission Area strategy is woven from three strong threads:

  • Submarine Warfare to enable and enhance submarine operations through security, stealth, mission payloads, operations, nuclear weapons security, and advanced technologies
  • Anti-Submarine Warfare (ASW) to detect and engage the undersea threats through advanced ASW systems development, related science and technology (S&T) advancements, and torpedo defense
  • Unconventional Littoral Warfare to extend the reach through unmanned systems, tailored ISR, rapid fielding, special operations undersea mobility, and mine warfare
As is the case for all of the military services, undersea warfare and the submarines that constitute the backbone of this military mission face increasing levels of complexity of environment, new mission requirements, and transformational technologies. Today’s focus includes not only operations in the littoral—the relatively shallow waters near coastlines—but also the large-area open-ocean threat. National strategic deterrence policy that relies on ballistic missile submarines requires continued attention to ensure their security and survivability. This remains a critical challenge to which APL is making significant contributions. In addition, improving sensor and processing technologies pose challenges for protecting the security and survivability of U.S. submarines and offer opportunities for exploiting threat submarine vulnerabilities.

Current technology research areas for the USW Mission Area include advanced algorithms, modeling and simulation, advanced sensors and materials, efficient energy sources and management for unmanned systems and sensors, cybersecurity of undersea warfare systems, communications and command and control (C2), unmanned systems, rapid prototyping, and electronic warfare and non-kinetic effects enabled from undersea platforms.


A strong S&T foundation remains a key enabler of APL’s undersea warfare contributions. The Laboratory is nationally recognized for expertise in acoustic and non-acoustic phenomenology of submarine signatures and detection mechanisms. APL’s expertise includes systems engineering, signal processing, automated target recognition, sensor design and development, tactical system performance evaluation, and large-scale, oceanographic scientific and tactical system testing and analyses.

Essential to our ability to provide cutting-edge solutions to the undersea environment’s most challenging problems, the USW Mission Area draws on technical staff with experience in ocean physics, submarine operations, and a wide variety of engineering and analytical technologies. Our work scope spans from early concept development and trade studies, through prototype development, to full system testing and evaluation. Conduct of comprehensive scientific experiments and accompanying algorithm and model development based on the first principles of physics remains the cornerstone for these programs. We develop, test, and evaluate prototype systems and technology for enhancing undersea warfare capabilities.

Major contributions include technical studies and assessments, testing and evaluation, prototype development, and development of special deployed systems. We provide basic scientific research in undersea detection physics, development of accurate systems models validated through conduct of rigorous at-sea testing, technology and systems assessments to assist the acquisition community in making smart “buy” decisions, systems engineering, and development of sensors and signal processing. Our programs include technical contributions and leadership in areas such as:

  • Detection physics, including acoustics, non-acoustics, hydrodynamics, physical modeling, and model validation
  • Algorithms for detection and classification and contact tracking
  • Towed array and autonomous acoustic sensors
  • End-to-end systems engineering
  • Beamforming/front-end signal processing
  • Anti-jamming and anti-spoofing
  • Radar systems
  • Communications for distributed systems
  • Fusion for maritime scene management
  • Human systems integration
  • Software engineering
  • First-principles model development and validation
  • Prototype system development
  • Operational analyses, research, and support
  • Development of platform roles, missions, and countermeasures
  • Rigorous sea-test planning, conduct, and analysis
  • Oceanographic database development and maintenance
  • Rapid prototyping
  • Autonomous systems

Facility Highlights

The USW programs benefit from state-of-the-art facilities throughout the APL campus. The following are highlights of three facilities of significant note in support of the USW programs.

Array Fabrication and Test Facility (AFTF)

Array Fabrication and test Facility
The AFTF provides the capability for modifying existing and fabricating new acoustic array instrumentation, including both mechanical and electronic fabrication and testing. This facility can be used for modification or fabrication of mechanical array elements and electronic instrumentation, including various types of array sensors. Pressure and temperature testing of both mechanical and electronic units for water integrity is also available. The facility is equipped with an array test stand that can test full-length modules (170 feet) in water. Module tension testing can also be performed to a 15,000-pound maximum. The AFTF is also equipped with a 10-inch-diameter × 200-foot-long vacuum chamber for module housing.

Engineering and Sea Test/Ocean Instrumentation Facilities

Engineering and Sea Test/Ocean Instrumentation Facilities
A High Bay Facility is equipped to handle the largest components of systems required for field-test preparation. Within this facility are a System Integration and Testing Laboratory, Computer Systems Laboratory, Navigation/Communication Laboratory, Sensor Systems Integration Laboratory, Sensor Calibration Facility, Encapsulation Laboratory, and several other areas. A Test Planning and Track Reconstruction Facility; autonomous sensor fabrication and testing; towed-array fabrication, assembly, and testing facility; Electronic Assembly Laboratory; and Total Ship Monitoring Laboratory are also available.

Hydrodynamics Research Laboratory

Hydrodynamics Research Lab
APL’s Hydrodynamics Research Laboratory is dedicated to simulation of oceanographic processes related to naval applications. The primary focus of the research in the laboratory has been on stratified flow phenomena (e.g., studies of internal waves, turbulent wakes, and double-diffusive processes). In addition, studies have also been performed on a variety of flow processes (e.g., surface bubble wakes and turbulent mixing processes that model flows in estuarine environments). The primary experimental tanks include a 7.6-m × 1.8-m × 0.8-m-deep stratified tow tank and a 9.1-m × 0.9-m × 0.6-m-deep low-turbulence level water channel. Stratification is achieved by using a variable brine concentration. Additional smaller experimental tanks have been configured for specific experiments (and can be reconfigured if needed), including a temperature/salinity-controlled tank for double-diffusive wave interaction studies and a two-layer stratified shear tunnel used for studies of solitary wave propagation. A self-propelled slender model has been used extensively for submarine wake studies. Instrumentation available includes a high-speed instrument carriage, a high-speed tow system, an array of conductivity probes, surface gauges, flowfield imaging systems, and a recently acquired particle imaging velocimetry system.