Naval Surface Warfare Center , Dahlgren Division Research Articles

Optimizating the Energy Storage Configuration of a Single Stage Coilgun to Maximize Efficiency

Naval Surface Warfare Center Dahlgren Division (NSWCDD) has been exploring methods of maximizing coilgun electrical-to-kinetic energy transfer efficiency by optimizing the geometries of wire-wound drive coils and armatures. Such optimization permits a reduction in the number of stages for a multistage coilgun, thus decreasing its design complexity and power requirements. NSWCDD applied optimal design trends to the coilgun geometry and its energy storage configuration to build a single stage coilgun capable of launching a 447-g projectile to 144 mph, resulting in an efficiency of 14.47%. To date, this is the highest experimentally achieved efficiency of a single stage coilgun without the use of cooling or initial armature velocity. The efficiency may be determined by the drive coil current measurements with and without the armature, as an alternative to knowing the speed and mass of the armature.

Optimizing Coilgun Geometry to Maximize Efficiency

Naval Surface Warfare Center Dahlgren Division (NSWCDD) has been exploring methods of maximizing coilgun electrical-to-kinetic energy transfer efficiency by optimizing the geometries of wire-wound drive coils and armatures. The optimum geometry of a coilgun is heavily dependent on the application, which may include unalterable variables, such as projectile design and weight, exit velocity, source power (voltage, capacitance, and so on), and physical size requirements. However, during the course of this effort, NSWCDD has theoretically observed and applied common design trends to all geometries, resulting in increased efficiencies. To date, NSWCDD has used the optimization design trends to design, build, and test a single-stage coilgun achieving an efficiency up to 12.18% with a stored energy of 5 kJ. This achieved efficiency is 150% greater than efficiencies presented in the literature at the respective stored energy.

Overcoming Cost-Estimating Challenges for Navy Combat Systems

The Department of Defense has established guidelines and processes that have evolved over several decades for its acquisition community to ensure affordability of Navy ship and combat systems. A common challenge within the Navy combat systems cost-estimating community is the ability to utilize many of the guidelines and processes put in place by experienced entities such as the Government Accountability Office and the Naval Center for Cost Analysis because of the evolving environment associated with past, present, and future Navy combat systems. The purpose of this paper is to give a detailed insight on the challenges Naval Surface Warfare Center, Dahlgren Division (NSWCDD) cost estimators encounter when building cost models and estimates for the Navy. Many challenges include limited program definition because of emerging threats, new technologies, and collection and utilization of data to produce valid and credible estimates. Through combined knowledge, expertise, and evolving practice of incorporating lessons learned, the NSWCDD Cost Group has overcome many cost-estimating challenges. This paper will share the NSWCDD Cost Group's insights with the larger Navy community. Owing to the sensitive nature of cost, no specific estimates or project names are referenced. This paper is philosophical in nature and does not discuss mechanics of cost estimation in detail.

Effect of Display Design and Situation Complexity on Operator Performance

The U.S. Navy is currently developing its next-generation cruise missile, the Tactical Tomahawk, which improves upon current versions by its ability to be retargeted in flight against emergent time-critical targets. In this study, we developed an advanced operator interface prototype for monitoring, controlling and retargeting the Tactical Tomahawk missile and empirically tested the effect of mission complexity on the ability of shipboard operators to maintain situational awareness in various operational scenarios. The first phase of research involved a domain analysis of three primary domains: the weapon system; time-critical decisionmaking; and principles of interface design. The second phase was a concurrent Cognitive Work/Task Analysis (CW/TA) and scenario development effort. The third phase was interface component design followed by complete prototype implementation. In the final phase, we trained and tested twenty graduate students on the dynamic and interactive prototype, based on hypotheses pertaining to both monitoring and retargeting tasks. Statistical results support two primary conclusions. First, operators can maintain adequate situational awareness when monitoring eight missiles and twelve targets simultaneously. Second, results support the use of the missile timebar feature in the interface to compare events. Subjective results indicate the requirement for a robust decision support tool to facilitate rapid retargeting decisions. These and other results form the basis for recommendations to the Naval Surface Warfare Center, Dahlgren Division (NSWCDD) about how to most effectively allocate personnel resources in the design of a command and control watchstation for the Tactical Tomahawk cruise missile system.

Design of a Real‐Time Multisensor Search and Track System

ABSTRACTLow flying missiles present severe difficulties to shipboard radar systems, which must detect and track them in order to support defensive weapons systems. Propagation conditions at these altitudes create an impossible task for a radar only search and track system. To this end, the Naval Surface Warfare Center, Dahlgren Division (NSWCDD) has been investigating the use of a horizon search infrared (IR) sensor for assisting the radar in the target detection and tracking task. Ongoing scientific experiments have determined the characteristics of both the radar and IR sensor systems necessary to support this task. The definition of these sensors, along with knowledge of the propagation conditions have been drivers for the design of the algorithms and techniques for effectively integrating multisensor data. In the system described in this paper, active and passive sensor data is integrated to achieve improved firm track range. Detections from a horizon search infrared (IR) sensor and a horizon search radar are provided to a central sensor integration processor where both track initiation and radar dwell scheduling are performed. Significant increases in the detection range of the radar are achieved by using a high energy waveform along cued bearings generated by high confidence detections from the IR sensor. Previous results and recent real‐time field test data are presented which support the system concept.

Experiences with CMS2-to-Ada translation tools

This paper describes experiences with three CMS-2 to Ada language translators. It describes the evolution of an effort whose initial goal was trial usage of a single translator, into an effort which ultimately used three translators and made some comparisons of their outputs. The following points represent key findings and conclusions from these experiences. All three of the translator tools successfully generated Ada source code. However, further evaluations would be beneficial. Translation will be useful to systems and software engineers as a part of an overall transition scheme. This paper describes experiences by personnel from the Naval Surface Warfare Center, Dahlgren Division (NSWCDD) and their support contractor CSC. The work was supported by the organizations that developed the translators: Computer Command and Control Company (CCCC), Johns Hopkins University/Applied Physics Laboratory (JHU/APL), and the Navy Command, Control, and Ocean Surveillance Center (NCCOSC) Research and Development Division (NRaD). Translator operation data were collected and reviewed to develop conclusions and recommendations for further development of CMS-2-to-Ada translation technology. Two of the translators (those from CCCC and NRaD) were installed at NSWCDD and operated by NSWCDD and CSC. The third translator was operated in its native environment at JHU/APL. All three of the translators were used to translate the same segment of operational CMS-2 code—a weapons selection function.