OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Trusted AI & Autonomy OBJECTIVE: This topic seeks to develop an underwater sensor optimized for size, weight, power, and cost (SWAP-C) that can be mounted on a small uncrewed boat to detect bathymetry and underwater hazards in shallow, bubbly environments. DESCRIPTION: There is an increasing need to enable U.S. Army sustainment and maneuver support operations through littoral environments, including shallow-water and surfzone based landings, in potentially contested regions. In particular, enabling maritime operations and autonomous distribution to support logistics over the shore for the Joint Forces was recently identified as an S&T priority. In these over-the-shore operations, mapping bathymetry and shallow water hazards (e.g., unexploded ordinance) are of primary importance to ensure safe, efficient, and effective force projection. On exposed coasts, bubbles from breaking waves are a typical environmental impediment that attenuate acoustic signals denying adequate sensing, which leaves crewed or uncrewed systems with limited situational awareness in a particularly challenging environment, arguably the most critical portion of any transit. Surfzone bubbles range in sizes, depending on whether they are part of the alpha plume (initial injection) with sizes ranging from cm to tens of micros or the gamma plume (resident plume of smaller bubbles), the both of which creates attenuation of acoustic signals (Deane G. B., 1997, 1999). Leighton (2010) highlighted methods to classify bubbles and reduce their clutter using a Twin Inverted Pair Sonar (TWIPS) signal, motivated by signals used by dolphins. This was examined in boat wakes by Leighton (2011). Lee (2016) highlights bubble's non-linear response as a potential method for discerning bubbles from hard targets. Yang (2012) explored bubble removal through doppler shifting signals, similarly, explored in a boat wake. The goal of this topic is to develop a system capable of sensing the seafloor (or hazards proud to the seafloor) through bubbly environments like the surfzone in real-time as part of the onboard signal processing so it can potentially be used for real-time navigation. The final product should be a portable underwater sensor (e.g., acoustic sounder or other sensing device that meets the objectives described here) that can be mounted on vessels (large and small) and ruggedized to withstand the high hydrodynamic loading that commonly occurs in the surfzone. The proposed system should have similar form-factors and power requirements with typical state-of-the-art sonars used on uncrewed surface vehicles. Since the surf zone environment is inherently shallow, the minimum range of reliable detection must be as close as 10 cm from the sensor head. Both acoustic and non-acoustic sensing methods will be considered. Acoustic sensing methods need not use methods mentioned in cited literature, though proposers are encouraged to be familiar with the work cited in this document. The minimum viable product demonstrates a producible single beam sonar or equivalent non-acoustic solution that can be used on a vessel as small as a single person portable Uncrewed Surface Vehicle (USV). Ideally, the capability/technology should be transferable to multi-dimensional sensing, such as multi-beam and/or side scan to be used on USVs. PHASE I: This topic is accepting Phase I proposals for a cost up to $250,000 for a 6-month period of performance. Demonstrate the feasibility of sensing with a single beam sonar through bubble media in a laboratory (or isolated/simplified field) environment. Develop a test case that vary bubble sizes and concentrations and highlight the capability of the developed technology's ability to enhance perception through these different conditions. In this stage, it is preferred if the performer can identify environmental features that have the highest impact on performance (e.g. range, bubble size, bubble/sediment concentrations, etc.) identifying seafloor. The most effective methods will be determined and proposed for Phase II. PHASE II: Manufacture field prototype single beam (preferred multi-beam or Side-scan) and demonstrate in field relevant environment. Phase II will focus on manufacturing a field ready prototype and test in a field relevant environment for single beam and extension to side-scan or multi-beam sonar. Develop a field test to demonstrate the developed sensor. This could be done on a small (un/crewed) craft. The Government may be able to support experimentation and validation if the vendor is unable to develop a safe surf-zone testing/experimentation operation. Technology should be demonstratable in a range of breaking wave conditions against a known truth. Not only should the bottom be clear in the backscatter signal, but performer should develop a bottom tracking algorithm that can be used to track the bottom in a wide range of conditions. Reporting tracked bottom should follow applicable conventions. Accurate timing of ping should be available. Data should be available via relevant serial protocols and ethernet (at least). Geometries should consider usage mounting on small uncrewed surface vehicles. Deliver a reporting document: (1) a computer-aided design (CAD) model of developed technology(s) (2) the experimental procedures and results that demonstrate the process meets the performance requirements; (3) the developed system. A favorable performance evaluation will lead into Phase III applications. All research, development, and prototype designs shall be documented with detailed descriptions and specifications of the composition, fabrication, microstructure, and mechanical performance of the prototype repair materials. PHASE III DUAL USE APPLICATIONS: There is a strong commercial hydrographic survey industry that could benefit from this technology. Hydrographic surveys are required as part of every USACE Civil Works beach and navigation project nationally, and are used widely within the commercial dredging industry and maritime safety industries. Presently, operation in the surf-zone is constrained to low or non-breaking wave conditions, meaning the ability to collect these data are significantly weather-constrained. REFERENCES: https://pubs.aip.org/asa/jasa/article-abstract/102/5/2671/558076/Sound-generation-and-air-entrainment-by-breaking https://journals.ametsoc.org/view/journals/phoc/29/7/1520-0485_1999_029_1393_aepabs_2.0.co_2.xml?tab_body=fulltext-display https://pubs.aip.org/as KEYWORDS: Surf Zone; Autonomy; Landing; Acoustics; Bubbles; Sensing; Underwater Sensing; Acoustic Sensors
