In-situ Seabed Physical Properties Probe (ISPPP)

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Sustainment OBJECTIVE: Develop a probe to rapidly gather in-situ data on physical properties of seabed and shallow sub-subsurface sediments in either a tethered (reusable) or expendable form factor. DESCRIPTION: Characterization of sediments on the seabed and in the shallow-subsurface is a vital requirement for research, offshore infrastructure development, acoustic propagation measurements, and target detection. Traditional methods of characterizing these sediments usually require shipboard sample collection and laboratory testing or specialized in-situ testing equipment requiring complex handling and data processing steps. Free-fall penetrometers, acoustic probes, and environmental sampling sensors are routinely deployed individually to estimate the physical properties of seabed sediments for use in geologic and geophysical assessment of seabed character, geoacoustic inversions, and transmission/bottom loss calculation; however, the time required for sample collection or in-situ measurement to data availability prohibits the utilization of these data in dynamic seabed environments. These instruments are also rarely used together, from autonomous platforms, or in expendable form factors. This STTR topic seeks development of an in-situ seabed physical properties probe to provide rapid seabed and shallow sub-surface sediment characterization in a tethered or expendable form factor. PHASE I: Develop a concept for a seabed sediment physical properties probe capable of measuring/estimating environmental parameters (e.g., temperature, salinity) in the water column and seabed/sub-seabed (pore water), sediment sound speed, and sediment strength properties (e.g., undrained shear strength, friction angle and cohesion), with reporting of estimated seabed/shallow sub-surface character (e.g., sound speed ratio, grain size, porosity). Describe the mechanistic underpinnings of the probe and support it with models and simulations. Simulations should demonstrate the measurement resolution and uncertainty in sediment classification as a function of penetrated sediment depth in a representative ocean environment. The conceptual design should operate at ocean depths up to or greater than 4000m. PHASE II: Develop, build, and demonstrate a hardware version of the probe based on the Phase I concept. The demonstration probe does not have to be expendable but should demonstrate the capabilities for acquisition and transmission of the sediment characteristics/physical properties stated in the requirements. Demonstrate that the probe is capable of penetrating the seabed and providing measurements at accurate sub-surface depths. Develop a capability for operation across a range of ocean depths and seabed types, with accurate measurement geo-positioning. Develop a plan in consultation with the Navy for demonstrating the probe to include compliance with environmental regulations. After demonstrations, develop a design for a tethered (reusable) version deployable from autonomous platforms or an expendable version of the probe with compact form factors that can communicate with remote receivers. PHASE III DUAL USE APPLICATIONS: The expected transition will be a tethered or expendable acoustic in-situ measurement probe that can be used for seabed characterization and geotechnical surveys for naval or civil applications (e.g., reconnaissance geotechnical surveys, post-disaster seabed stability assessment, seabed AUV survey groundtruth measurements). The tethered version can be deployed from autonomous vehicles. The expendable version can be deployed by hand or with use of a launcher from the deck of a ship for operational surveys or in support of basic and applied research. REFERENCES: 1. Ballard, M.S.; Lee, K.M.; McNeese, A.R.; Wilson, P.S. and Goff, J.A. Development of a system for in situ measurements of geoacoustic properties during sediment coring. Proceedings of Meetings on Acoustics, Vol. 26, No. 1, May 2026. AIP Publishing. 2. Jaber, R. and Stark, N. Geotechnical Properties from Portable Free Fall Penetrometer Measurements in Coastal Environments. Journal of Geotechnical and Geoenvironmental Engineering, 149(12), 2023, p.04023120. KEYWORDS: Underwater Acoustics; seabed characterization; physical properties; Geoacoustic Inversion; geotechnical survey; sediment