Naval Postgraduate School

About: Naval Postgraduate School is a education organization based out in Monterey, California, United States. It is known for research contribution in the topics: Tropical cyclone & Boundary layer. The organization has 5246 authors who have published 11614 publications receiving 298300 citations. The organization is also known as: NPS & U.S. Naval Postgraduate School.

Rapid Verification Method for the Trajectory Optimization of Reentry Vehicles

Abstract: Introduction T HE trajectory optimization of path-constrained nonlinear dynamic systems such as those arising in the guidanceand design of reentry vehicles has long been considereda difŽ cult problem.1i3 Of themany methods to solve such problems, the direct collocation method with sparse nonlinear programming (NLP) has proved to be quite effective. Because direct methods do not tie the resulting solutions to the Pontryaginmaximum principle4 (PMP), a two-step direct–indirect approach has been used successfully for Ž nding extremal solutions.5 One major drawback of the direct–indirect approach is that a signiŽ cant amount of labor is necessary to derive all of the necessary conditions including complex switching and junction conditions for state-constrainedproblems.Even with estimates of the adjoint arcs, solving the multipoint boundary-valueproblem is an elaborate task. Over the past few years, a new approach to solving complex trajectory optimizationproblems has been proposed.6i9 The Legendre pseudospectralmethod is a particularlyeffectivemethod because it providesspectrallyaccuratesolutionsfor the costatesand other covectorswithout the use of any analyticaldifferentialequationsfor the

Channels that Cooperatively Service a Data Stream and Voice Messages

Abstract: This paper presents an analysis of the performance of a special type of voice data queueing system. The system consists of an integrated circuit-and packet-switched multiplexer resembling that found in the SENET network. A fluid-flow approximation for the data component is introduced to ease study of the voice loss rate and data packet waiting times. In this paper it is shown that very long data queues are possible, with the mean data queue length being proportional to the ratio of the holding time for voice to the holding time for data. The equilibrium distribution is determined, and aspects of the transient behavior are characterized. The question of how much bandwidth to reserve for exclusive use of data and how much to share between voice and data is addressed.

Mapping the U.S. West Coast surface circulation: A multiyear analysis of high‐frequency radar observations

Abstract: signals with phase speeds of O(10) and O(100 to 300) km day −1 and time scales of 2 to 3 weeks The signals with slow phase speed are only observed in southern California It is hypothesized that they are scattered and reflected by shoreline curvature and bathymetry change and do not penetrate north of Point Conception The seasonal transition of alongshore surfacecirculationforcedbyupwelling‐favorablewindsandtheirrelaxationiscapturedinfine detailSubmesoscaleeddies,identifiedusingflowgeometry,haveRossbynumbersof01to3, diameters in the range of 10 to 60 km, and persistence for 2 to 12 days The HFR surface currents resolve coastal surface ocean variability continuously across scales from

Hybrid Optimal Control Framework for Mission Planning

Abstract: With the progressive sophistication of future missions, it has become increasingly apparent that a new framework is necessary for efficient planning, analysis, and optimization of various concepts of operations (CONOPS). In recognizing that CONOPS involve categorical variables, we propose a hybrid optimal control framework that mathematically formalizes such problems. Hybrid optimal control theory extends ordinary optimal control theory by including categorical variables in the problem formulation. The proposed formalism frees mission planners to focus on high-level decision making by automating and optimizing the details of the inner loops. The eventual goal of this formalism is to develop efficient tools and techniques to support the objective of increasing autonomy for future systems. In using the pseudospectral knotting method to solve hybrid optimal control problems, we generate a mixed-variable programming (MVP) problem. A simple, feasible integer programming subproblem is identified that reduces the combinatorial complexity of solving the MVP. In addition to developing the framework using various examples from aerospace engineering, we provide details for a two-agent benchmark problem associated with a multiagent launch system. The entire process is illustrated with a numerical example.