Naval Supply Systems Command

As the U.S Navy strives to strengthen its maritime dominance in the 21st century, the need for higher operational availability is integral to being able to perform its mission. Corrosion of structures and systems in corrosion prone areas drives reliability and is a significant contributor to depot maintenance availability schedules and costs. Ultimately, corrosion is a key risk item that impacts all seawater exposed systems, reduces or even defines system life/reliability, degrades operational availability, and demonstrably increases lifecycle costs. Design decisions made in acquisition will affect time in maintenance, cost, safety, and operational availability throughout the life cycle. The proper corrosion control methods in the form of material selection, paints and coatings and cathodic protection determine the extent of corrosion. It is critical that corrosion control requirements are codified early in the design process. Design trade-offs that prioritize initial cost over corrosion control can equate to serious life-cycle cost and maintenance impacts, as well as system downtime or inability to perform a mission. This topic will discuss Navy relevant coatings, cathodic protection, and material selection requirements and source documentation, with practical end-user applicability.

Global energy demand is growing faster than anticipated [McKinsey, 2024]. Excerpts from the McKinsey report include: Electrification is accelerating—our analysis suggests that, between 2023 and 2050, electricity consumption could more than double in slower energy transition scenarios, and nearly triple in faster scenarios. This is in comparison to total energy consumption growth of up to 21 percent over the same period. Electricity is projected to become the largest source of energy by 2050 across scenarios, with consumption coming from traditional sectors (for example, electrification of buildings) as well as newer sectors (such as data centers, EVs, and green hydrogen). Global electricity production in 2022 amounted to over 32,000 Terawatt Hours (TWh) [Ember, 2023], up from 12,000 TWh in 1990 and expected to double by 2050. Fossil fuels powered 61% of 2022 electricity.

Abstract. Science Monitoring And Reliable Telecommunications (SMART) subsea cables utilize sensors integrated within repeaters to record temperature, acceleration, and pressure on the seafloor. The planned Tamtam SMART cable will connect Vanuatu and New Caledonia across a major subduction zone. Modeling recent MW 7.7 to 8.0 earthquakes and maximum considered MW 8.33 to 8.8 scenarios provides a range of seismic waveforms with realistic relative timing and long-period ground displacements at the sensor locations as well as coseismic seafloor uplift and subsidence at the sources used for tsunami excitation. A nonhydrostatic model describes tsunami generation, propagation, and scattering in the southwest Pacific. Spectral analysis of the computed tsunami waves shows multi-scale oscillations along the Vanuatu trench with periods from a few minutes to over an hour. The cable sensor locations are outside energetic antinodes of oscillation modes and the modeled tsunami amplitude is representative of the seismic source with minor interference from land masses. The suite of synthetic seismic and tsunami waveforms informs implementation of the sensor system for regional hazard monitoring. The Tamtam SMART cable, deployed in a very active tectonic environment with limited on-land instrumentation, will augment rapid earthquake and tsunami warning as well as source quantification.

Adoption of laser powder bed fusion (L-PBF) as a trusted manufacturing process for conventional alloys like Ti-6Al-4V (Ti64) requires a mature industrial base, established material specifications and an understanding of causes of variation in material performance. Although historical studies have shown extreme variation in mechanical properties between multiple vendors and builds, recent improvements in L-PBF machine design and understanding of the printing process motivate reevaluation of the consistent build quality across vendors. With the ultimate goal of establishing mechanical property design allowables involving numerous L-PBF processes, seven vendors fabricated and stress-relieved samples of Ti-6Al-4V for tensile testing using six unique L-PBF systems. Ultimately, 198 samples were tested, which found that material produced by five vendors exhibited mechanical properties with low variation and fit a normal distribution, enabling calculation of A- and B-basis design allowables. Two vendors provided material with properties that were statistically out of family, which were easily identified through routine metallography. Electron microscopy indicated the presence of significant porosity and contamination in one vendor’s samples and an out-of-specification heat treatment in another. Given the consistency in properties, this study demonstrates great promise for L-PBF Ti-6Al-4V material maturity.

Well known to the high-speed naval community, Landing Craft Air Cushion (LCAC) is ubiquitous as the US Navy's amphibious ship to shore connector. Now, a new naval air cushion vehicle (ACV), LCAC 100, has arrived and is currently undergoing post-delivery test and trials in preparation for fleet operations. As the next generation LCAC, the design capitalizes on over 35 years of LCAC experience and technology development. Among its many impressive attributes, it introduces an integrated flight control system, high performance composite structures, and a simplified, but significantly more powerful propulsion and lift system. It employs electrically actuated effectors, advanced skirt materials, and technologies for vibration monitoring. This paper contributes to the historical record by describing many of the important development efforts over the past decade, including pre-award studies, contract design, detailed design, and post-delivery phases. It includes discussion on technological successes, remaining challenges facing the craft, and looks ahead to mission scenarios of the future.