The Sperry Marine MK 49 Ship’s Inertial Navigation System (SINS) is now in production for marine surface and subsurface applications. This system has been selected as the standard NATO SINS equipment and is the only marine inertial navigator which utilizes ring laser gyros. In order to serve the NATO community, the system must withstand a variety of shock stimuli (STANAG 4141, STANAG 4142, BR3021, etc.). Sperry Marine has shock hardened the system enclosures and developed a shock isolation system for the Inertial Measurement Unit (IMU) using tension compression liquid spring/dampers in a hexapod configuration. This isolator assembly provides the shock attenuation and precision angular alignment return ability that is needed to meet the above specifications. This paper addresses the design process to shock harden the IMU and presents experimental results.
84. MITIGATION OF MILITARY HIGH SHOCK TRANSIENTS FOR SHIPBOARD GYROCOMPASS WITH FIBER OPTIC GYROS (FOG)
The Taylor Devices self-centering hexapod mount provides MIL-S-901D shock protection for the Litton Marine Systems MK27F Attitude and Heading Reference System (AHRS). This new Reference System satisfies stringent military shock and vibration requirements. Unlike Ring Laser Gyro (RLG) which have low fragility levels (Max 50 g), the LN200 Fiber Optic Gyro Assembly can be exposed to levels as high as 90 g. This paper addresses the shock transient mitigation for shock requirements specified by MIL-S-901D. Comparisons between predicted and measured response are provided for a single strut as well as the fully shock isolated platform. Analytical and experimental results are presented to demonstrate the effectiveness of the MK27F Shock Absorber basic design for MIL-S-901D LWSM and predicted response is also presented for the floating platform Heavy Weight Shock Machine (HWSM).
This article appeared in Special Operations Technology magazine. It provides a very complete explanation of the Taylor Devices isolated seat for the Navy, complete with many photos. The article also includes the experiences of the seat occupants under high speed ocean travel.
69. ANALYSIS, OPTIMIZATION, AND DEVELOPMENT OF A SPECIALIZED PASSIVE SHOCK ISOLATION SYSTEM FOR HIGH SPEED PLANING BOAT SEATS
The Mk V Special Operations Craft (SOC) is used to carry Special Operations Forces (SOF) into and out of combat operations. During operation, particularly during extended training missions, the passengers and crew have reported numerous cases of musculoskeletal injuries from operation in high sea states. This paper describes the analysis, development and operational testing of a highly specialized, non-linear, passive shock isolated seat for this craft. Initial sea trial testing of the isolation system resulted in positive operator feedback that correlated well with earlier field measurements and also validated the analytical predictions.
The addition of passive damping to a structure greatly increases its earthquake resistance. It is possible to get further increase through an active or semi-active control system for the dampers. Semi-active damping is preferred due to low external power requirements and fail-safe operation. This paper describes the history of the successful use of semi-active fluidic control devices in military applications and how this technology has been adapted to earthquake hazard mitigation. Testing of a semi-active continuously adjustable damping device through fluid orificing is described. Mathematical models of the behavior of the device are also presented.