Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Sonar & Radar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Nitrogen Heat Pipe for Cryocooler Thermal Shunt

Abstract: A nitrogen heat pipe was designed, built and tested for the purpose of providing a thermal shunt between the two stages of a Gifford-McMahan (GM) cryocooler during cooldown The nitrogen heat pipe has an operating temperature range between 63 and 123 K While the heat pipe is in this temperature range during the system cooldown, it acts as a thermal shunt between the first and second stage of the cryocooler The heat pipe increases the heat transfer to the first stage of the cryocooler, thereby reducing the cooldown time of the system When the heat pipe temperature drops below the triple point, the nitrogen working fluid freezes, effectively stopping the heat pipe operation A small heat leak between cryocooler stages remains because of axial conduction along the heat pipe wall As long as the heat pipe remains below 63 K, the heat pipe remains inactive Heat pipe performance limits were measured and the optimum fluid charge was determined

Resistance of Demountable Mechanical Lap Joints for a High Temperature Superconducting Cable Connector

Abstract: Experiments conducted to determine the resistance of demountable HTS lap joints with variations in compressive stress are reported here. A joint fixture was constructed that enabled the simultaneous testing of multiple joints of different configurations. The joint fixture was installed in a loading facility, comprising a pneumatic press mounted in a vacuum bell jar and connected to a GM cryocooler. The resistance across each joint was measured by means of voltage taps over a range of compressive joint forces. The test results demonstrated that joint resistances less than 2 muOmega were possible with only light joint loading.

An ultrasonic guided wave technique for damage testing in a ship hull

Abstract: Ultrasonic guided waves have been widely utilized in the testing of large structures due to such characteristics as high penetration power and long propagation distances. In this paper, development and application of guided wave techniques for damage testing in a ship hull is presented. Selecting proper modes and frequency ranges is based on the wave structures. Lamb and shear horizontal waves are generated in model steel plates and an actual ship hull with simulated damage. An approximate image of damage, utilizing a discontinuity locus map, is constructed using the reflected guided waves from the damage. A discontinuity locus map provides information on location and size of damage. Experimental results with lamb and shear horizontal waves are demonstrated and compared. The potential of the discontinuity locus map technique for detecting and quantifying damage in a ship hull is discussed.

Magnetic anomaly guidance system for mine countermeasures using autonomous underwater vehicles

Abstract: This paper describes a magnetic anomaly guidance system that, with support from the Office of Naval Research, is being developed for fully autonomous detection, localization and classification of ferrous mines in Very Shallow Water/Surf Zone (VSW/SZ) environments. The magnetic guidance system's hardware configurations and magnetic target signature processing methods specifically have been developed for autonomous guidance of small, maneuverable sensing platforms, such as Underwater Bottom Vehicles, (UBVs), to magnetic targets. The prototype magnetic anomaly guidance is a three-axis magnetometer-gradiometer comprised by an array of triaxial fluxgate magnetometers and triaxial accelerometers. This design allows development of magnetic gradient tensor contraction scalars that provide the basis for a unique method for magnetic guidance of UBVs to underwater and buried mines. The triaxial accelerometer array can be used for mitigation of the target-detection-range-reducing effects of large changes in sensor platform orientation. Field test results indicate that a simple magnetic guidance algorithm based on comparison of the magnitudes of contractions of gradient tensor subsets measured by "primary guidance axes" of the sensor array will provide a robust and practical method for fully autonomous guidance of highmobility UBVs to magnetic targets. Target detection range can be enhanced by using rotationally invariant tensor contractions for robust proximity sensing and "pseudo-robust" scalar total field quantities for "homing in on" magnetic targets. Sensor system stability and DLC performance also would be improved by the use of better, temperature-compensated magnetometers. The results indicate that the magnetic anomaly guidance system and its method for target localization are particularly appropriate for homing in on magnetic targets from high-mobility sensing platforms such as small UBVs or Navy Divers.

Design and Development of the WR-21 Intercooled Recuperated (ICR) Marine Gas Turbine

Abstract: The U.S. Navy is developing an Intercooled Recuperated (ICR) marine gas turbine, designated the WR-21, for propulsion of future surface ships. The objectives of this development program and the key technical requirements are summarized. The design of the WR-21 is described in considerable detail. Meeting all the design requirements for performance, space, weight, reliability, maintainability, and life has been challenging. Numerous design tradeoffs and iterations have been performed to optimize the design within the constraints imposed in the ICR technical specification. Integration of the WR-21 engine into the DDG51 Flight IIA ship, which is the U.S. Navy’s first application, has influenced the WR-21 design. This paper discusses the aspects of the DDG-51 application that were factored into the design of the ICR engine in order to reduce installation costs.