TECHNOLOGY AREA(S): Ground Sea
OBJECTIVE: Develop a low-cost advanced material system for combatant craft to reduce the energy transferred to seated occupants during severe wave-slam events in craft operating at high speeds in rough seas.
DESCRIPTION: The Navy needs an advanced material system for combatant craft with breakthrough technology to lower acquisition costs of current shock mitigation systems by a minimum of sixty percent while also reducing the energy transferred to seated occupants by a minimum of fifty percent during severe wave-slam events in high performance craft operating at maximum speed n rough seas. Todays forces employ combatant patrol and assault craft that rely on speed, acceleration, and maneuverability for survivability and multi-mission success. These capabilities are at risk because of the impact energy associated with severe wave slams experienced in rough seas. High-speed craft missions in rough seas subject personnel to punishing impact environments that require protection and can expose naval personnel to repeated and severe shock loads caused by wave impacts in moderate to heavy sea conditions. The shock loads can produce discomfort, loss in occupant performance due to fatigue, and both chronic and acute injuries. Passive shock isolation seats originally developed for blast loads provide little or no protection from wave slam impacts, and can actually amplify peak accelerations created by wave-slams. Wave slam acceleration pulses can have duration times three to five times longer than blast loads, thus classical spring-damper systems may provide little or no protection. Semi-active or active spring-damper systems can provide protection, but the increased system complexity adds significant cost. An alternative approach is sought that would provide lower cost protection options that do not employ passive, semi-active, or active spring-damper systems. Current design practice is to install passive seats that employ springs and dampers (shock absorbers) or leaf-spring assemblies as protection mechanisms. They are passive seats because the spring-damper assemblies respond to individual wave impacts and have no active elements that change real-time to adapt to the environment. Numerous manufacturers offer different shock isolation seat designs with unique ergonomic features, but they are all expensive ($8,000.00 or more), and some are not effective shock mitigation systems. Another mitigation option is to pursue active seats with control sensors and actuators that anticipate wave impacts, but this is also an expensive option. The Navy needs a more affordable new technology seat solution that is capable of mitigating the unique wave impact loads experienced in high-speed craft. This topic seeks to identify and apply innovative material solutions, including engineered energy absorbing buffers, for future and current combatant craft seats. Seating solutions must be able to provide 50% energy reduction in a cyclic environment characterized by single severe impacts and lower amplitude impacts with encounter frequencies less than two hertz. Achieving this goal could increase mission capability while reducing acquisition and life cycle costs. Desired features include low cost rigid seat foundations with ergonomic cushions and a novel buffer that redistributes impact energy (for example multi-density, viscos-elastic, or other energy-absorbing material solutions, other novel energy reduction materials, or material systems). The solutions should have a minimum seven-year life span, require little or no significant routine maintenance or unique repair parts, and be configured for rapid removal for mission flexibility, repair, or expeditionary land-based applications. The Navy seeks to lower acquisition costs of current shock mitigation by sixty percent at a minimum while reducing the energy transferred to seated occupants by fifty percent at a minimum during severe wave-slam events in craft operating at high speeds in rough seas. Material technologies without the use of active or semi-active isolation systems must be able to withstand severe marine operational duty cycles, endure harsh maritime environments with saltwater and oil resistance, embody ruggedness to withstand repeated wave impacts, and demonstrate extended life performance. Novel approaches that lead to reduced personnel fatigue and improved protection will enhance affordability and enable increases in mission system capability without sacrificing speed or personnel transport capability.
PHASE I: The small business will develop a concept for an Advanced Material System for Reduced Wave Slam Energy in Combatant Craft for Naval Applications that meets the requirements described above. The small business will demonstrate the feasibility of the concept in meeting Navy needs and will establish that the concept can be feasibly developed into a useful product for the Navy. Feasibility will be established by material testing and analytical modeling. The Phase I Option, if awarded, will address technical risk reduction and provide performance goals and key technical milestones.
PHASE II: Based on the results of Phase I and the Phase II Statement of Work (SOW), the small business will develop a prototype for evaluation and delivery. The prototype will be evaluated to determine its capability in meeting the performance goals defined in Phase II SOW and the Navy requirements for Advanced Seating System for Reduced Wave Slam Energy in Combatant Craft. System performance will be demonstrated through prototype evaluation and modeling or analytical methods over the required range of parameters and an assessment of integration and risk. Evaluation results will be used to refine the prototype into an initial design that will meet Navy requirements. The company will prepare a Phase III development plan to transition the technology to Navy and potential commercial use.
PHASE III: The company will be expected to support the Navy in transitioning the technology for Navy use. The company will further refine an Advanced Seating System for Reduced Wave Slam Energy in Combatant Craft according to the Phase II SOW for evaluation to determine its effectiveness in an operationally relevant environment. The company will support the Navy for test and validation to certify and qualify the system for Navy use on current Combatant Craft ranging in length from 36 “ 88 feet. Private Sector Commercial Potential: The vendor will be able to market the new capabilities to over twenty boat builders who serve the U.S. military and commercial markets, as well as the international small boat commercial industry.
1. Riley, Michael R., Haupt, Kelly D., Ganey Dr. H. Neil, Ride Severity Profile for Evaluating Craft Motions Naval Surface Warfare Center Report NSWCCD-80-TR-2015/002 May 2015; http://www.dtic.mil/get-tr-doc/pdf?AD=ADA624077
2. Riley, Michael, R., Coats, Timothy, W., Acceleration Response Mode Decomposition for Quantifying Wave Impact Load in High-Speed Planing Craft, Naval Surface Warfare Center Report NSWCCD-80-TR-2014/007, April 2014. http://www.dtic.mil/get-tr-doc/pdf?AD=ADA621230
3. Riley, Michael R.; Coats, Timothy W., Quantifying Mitigation Characteristics of Shock Isolation Seats in a Wave Impact Environment, Naval Surface Warfare Center Report NSWCCD-80-TR-2015/001, January 2015, http://www.dtic.mil/get-tr-doc/pdf?AD=ADA622526
4. Riley Michael R., Haupt, Kelly D., Murphy, Heidi P., An Investigation of Wave Impact Duration in High-Speed Planing Craft in Rough Water, Naval Surface Warfare Center Report NSWCCD-80-TR-2014/026 April 2014, www.dtic.mil/dtic/tr/fulltext/u2/a616198.pdf -
KEYWORDS: Energy Absorption From Wave Slams; Energy Redistribution In Seating Systems; Wave Slam Impact; Small Boats At High Speeds; Combatant Craft; Shock In Seating Systems