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Title: Considerations in Development of Naval Ship Design Criteria for Launch and Recovery

Author(s): Kevin McTaggart, Sietske Hendricks, Ian Nimmo-Smith, Arild Oydegard, and Norbert Stuntz

Abstract: The NATO Seaway Mobility Specialist Team is developing new ship design criteria to ensure that ships are capable of supporting launch and recovery operations over their life span. This paper describes factors that must be considered in the development of these new design criteria, with an emphasis on frigates and destroyers with associated displacements of 3000 to 10000 tonnes. In previous decades, launch and recovery from naval ships has primarily encompassed helicopter operations and deployment of rescue craft. During the past decade, two trends have emerged which have major implications for ship design in support of launch and recovery. First, unmanned vehicles are becoming increasingly important in naval operations. Second, there is a requirement to deploy larger manned surface vehicles than previously, such as rigid-hull inflatable boats (RHIBs) with 10 to 15 personnel aboard. Furthermore, increased societal expectations for safety of personnel influence design and operation for both unmanned and manned vehicles. It is anticipated that launch and recovery operations will evolve rapidly as small vehicle operations evolve, especially for unmanned vehicles. This rapid evolvement presents challenges when designing naval ships, which typically have life spans of several decades. Consequently, naval ship design criteria for launch and recovery must ensure that a ship can support evolving launch and recovery needs during its life. Although the development of new ship design criteria for launch and recovery presents a formidable challenge, high interest from navies has led to much activity and resulting resources that can be used when developing new criteria. The NATO Industrial Advisory Group (NIAG) sponsored two recent studies on launch and recovery from naval vessels. JIP LAURA is an ongoing joint industry project on launch and recovery of small navy water craft, and is coordinated by Maritime Research Institute Netherlands (MARIN). For launch and recovery of air vehicles, NATO Advanced Vehicle Technology Task Group AVT-217 on Ship Design Guidance for Aircraft Operations is providing valuable input. Several areas for ship design guidance have emerged so far. Ship motions at launch and recovery locations are of concern for both air and water vehicles. Air vehicles require an acceptable air wake environment and sufficient deck space for launch and recovery operations. Launch and recovery of water vehicles is most commonly done using stern ramps or lifting appliances. The water wake of the ship can significantly influence launch and recovery of water vehicles at the stern. For stern ramps, relative vertical motion between the stern ramp and the ocean surface is of great importance, and can form a foundation for new design criteria. For launch and recovery of water vehicles using lifting appliances (cranes/davits), relative vertical motion is important and associated deck wetness must be considered. Launch and recovery systems are now often placed in sheltered alcoves along the side of the ship. Sheltered alcoves must be situated carefully to avoid problems such as wetness, slamming loads on the alcove ceiling, and flooding affecting ship stability. It is envisioned that increased naval interoperability of deployed vehicles will evolve, such as one navy launching a vehicle which is subsequently recovered by another navy. Such operations will require that ships have sufficient equipment and space to handle and store a variety of small vehicles. Modelling and simulation will play important roles in the development of new design criteria. Motion predictions for navy ships in waves are now mature and robust for environmental conditions under which launch and recovery operations typically occur. Similarly, air wake analyses are routinely conducted to ensure safe operation of air vehicles. More complex simulations are still maturing, such as nonlinear motions of small water craft near ships and multibody dynamics of launch and recovery using cranes.