N221-070 TITLE: Acoustic Vector Sensors that Achieve Affordable Array Directivity

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR);Networked C3

TECHNOLOGY AREA(S): Electronics;Information Systems;Sensors

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Achieve substantially more affordable application of acoustic vector sensors, particularly under less extreme contexts (e.g., ocean shelf vs. deep ocean applications, fat-line vs. thin-line towed array form factors, deployment packages larger than A-sized) through concurrent application of recent acoustic vector sensor design and manufacturing advancements.

DESCRIPTION: Acoustic vector sensors deliver directionality by virtue of sampling the kinetic energy portion of the propagating acoustic field rather than simply the potential energy portion of that field using a hydrophone. Such directionality can be achieved via a direct measurement of acoustic particle velocity; by temporal integration of measurements of acoustic particle acceleration; by temporal differentiation of measurements of acoustic particle displacement; or by spatial differentiation of the acoustic pressure field using an adjacent pair of hydrophones. Much progress has been made in the design and employment of highly compact, low power, and low noise-floor acoustic vector sensors in applications at lower frequencies, particularly within arrays that are relatively stationary in relation to the surrounding sea water or, if moving, include a substantial decoupler. For applications under circumstances of low environmental noise and/or harsh volume constraints, high strain sensitivity materials in combination with sophisticated signal conditioning electronics have been required to deliver the requisite sensor self-noise performance. Particularly in deep ocean applications and for thin-line towed array applications, the material and manufacturing requirements for the sensor housings have been extremely challenging. Sensor and array costs and their in-situ performance have also been substantially complicated by, and in some cases compromised by, the adoption of proprietary telemetry schemes that promised low technical risk and/or avoidance of non-recurring costs. SONAR array employment at shallower ocean depths and across a larger frequency band leads to arrays with more sensor elements which simultaneously and harshly drive up array costs and telemetry bandwidths.

This SBIR topic specifically addresses cost-effective manufacturing approaches that will enable wider adoption of acoustic vector sensor technologies by making directional sensors and arrays simultaneously more effective, more reliable, and more affordable. By employing the lessons learned in design, manufacturing, and employment of acoustic vector sensors for use in the most extreme operating conditions of depth and low background environmental noise, sensible options emerge for substantially reducing the cost of manufacturing sensors good enough for more less demanding operational circumstances. A combination of these steps should reduce the total cost of a joint pressure velocity sensor by more than 50%. Specific examples might include the use of lead zirconate titanate (PZT) or textured ceramics in lieu of more expensive PMN-PT materials, or concurrent additive manufacturing of sensor housings and vector sensor accelerometer beam mechanical components, or incorporation of a government-owned (e.g., non-proprietary) signal conditioning and digital telemetry architecture to reliably enable dramatic flexibility in array bandwidth, or some combination. Hybrid arrays that simultaneously sample the acoustic and kinetic energy field using either joint pressure-velocity sensors or co-located hydrophone/particle velocity sensors are also of interest.

PHASE I: Identify the tradeoffs between transduction materials, acoustic particle velocity sensor channel fabrication methods, telemetry alternatives, and environmental noise vs. array employment strategy to offer more cost-effective passive acoustic SONAR sensors and arrays.

The proposed approach should directly identify and address:

1. Identify and address Navy end user(s) requirements/constraints (e.g., the noise floor, size array packing volume/cost, size, weight, power requirements) that can be improved/relaxed.
2. Define clear objectives and measurable results for the proposed solution(s) � specifically how the combination of improvements will impact the end user application context.
3. Describe the cost variance and design feasibility when integrated vs a legacy capability.
4. Describe material science and manufacturing technology developments that would be required to successfully field the proposed solution(s).

Develop a Phase II plan.

PHASE II: Develop, integrate, and demonstrate a prototype acoustic vector sensor determined to be the most feasible solution during the Phase I period. The demonstration should focus on:

1. Evaluate the proposed solution vs performance requirements and cost and reliability objectives defined in Phase I.
2. Describe in detail how the resulting sensor design and production innovations can be adopted widely.
3. Identify a clear transition path by which a solution appropriate to a specific transition context can be advanced in collaboration with transition stakeholders.
4. Incorporate specific feedback from transition customer(s) regarding how the proposed solution can be integrated, supported, sustained, and relied upon to reduce acoustic vector sensors costs and to support the unique priorities of other applications/customers.

PHASE III DUAL USE APPLICATIONS: Expand mission capability vs. affordability options to include a broad range of government and civilian users and applications. Coordinate with the government for additional research and development, or direct procurement of products and/or services developed in coordination with the Navy.

REFERENCES:

1. Butler, Stephen. "Properties of Transducers: Underwater Sound Sources and Receivers." Naval Undersea Warfare Center Division Newport, Rhode Island (NUWC) Technical Document 12,289, 19 Dec 2018. https://apps.dtic.mil/sti/pdfs/AD1068326.pdf.
2. Caldwell, S.A. and Faella, J.A. "Open Architecture Telemetry Specification for Single Three Axis Vector Sensor Nodes in Thin Line Towed Arrays." Naval Undersea Warfare Center, Division Newport, Rhode Island (NUWC-NPT) Technical Document 12,345, 11 July 2019.
3. Faella, J.A. "Interface Control Document for Sensor Nodes using Open Architecture Telemetry (OAT) in Towed Arrays." Naval Undersea Warfare Center, Division Newport, Rhode Island (NUWC-NPT) Technical Document 12,341, 20 August 2019.

KEYWORDS: acoustic vector sensor; acoustic particle velocity; PMN-PT single crystal material; lead zirconate titanate; PZT ceramic material; Open Architecture Telemetry; textured ceramics