Simulation of DC spacecraft power systems

A modular state-variable approach is presented for DC spacecraft power system modeling and simulation. Each modular component is treated as a multiport network, and a state model is written with the port voltages as the inputs. The state model of a component is solved independently of the other components, using its state transition matrix. The state variables of each component are updated, assuming that the inputs are constant. Network analysis principles are then utilized to calculate the component inputs     

LIPS III-a solar cell test bed in space

The LIPS III satellite, which was launched into a 1100-km circular orbit of 60° inclination in the spring of 1987, is discussed. LIPS III is a member of the living-plume-shield class of spacecraft, all of which were built around a simple sheet metal plume deflector. The purpose of LIPS III was to provide a testbed for space power sources. An overview of the LIPS III system is given, and the experiments submitted for it, all but one of which were photovoltaic in nature, are described     

PAVE PACE: system avionics for the 21st century

The PAVE PACE Initiative has been established to validate system avionics concepts for advanced military aircraft. The author presents the rationale of why the advanced architecture established by the PAVE PILLAR program should be continued under PAVE PACE to achieve: practical and affordable airborne versions of modular parallel processing network architectures for many applications currently beyond real-time implementation, readily available avionics for use in all avionics and, greatly improved techniques to reduce the cost of software development and support. An approach to the overall design structure for future avionics is also presented that entails: the use of CAD (computer-aided design) tools to assist in the development of system, hardware and software requirements, the use of replicated hardware modules (some at the wafer level), the use of reuseable software modules and the use of CAD tools to tailor hardware/software modules for specific application requirements. Continued use of the PAVE PILLAR high-speed data bus and operating system is recommended as the means to integrate and control the data input and output of physically and functionally separate parallel networks     

US government policies and hypersonic flight in the 21st century

The author examines the potentially negative impact of the US regulations on the development of advanced materials, components, and systems. He gives high priority to modification of US antitrust laws if the US is to have the best possible opportunity to compete with more aggressive economies abroad. He identifies export controls as limiting the availability of data to US firms engaged in developing commercial applications. He asserts that policies must also be enacted to better protect intellectual property rights     

Incremental planning to control time-constrained blackboard-basedproblem solver [vehicle monitoring]

A planner that improves the control decisions made by a blackboard-based problem solver is described. This planner interleaves planning and execution. It sketches out major plan steps but incrementally details actions for only the next step since earlier actions influence how (and whether) to pursue a plan. The planner also reasons about time constraints, revising plans to meet problem-solving deadlines and deciding when it has done enough work on a problem. Implementation of these mechanisms is outlined, and experiments are discussed showing how they reduce overall computation and improve problem solving     

Heading and Speed Errors for x, y Tracking Filters

Heading and speed errors are analytically determined for noneumavering targets at the output of an x, y tracking filter which processes range and bearing measurements from a radar sensor in a track-while-scan (TWS) operation. These errors are shown to depend upon target range and speed, the angle between the radius and velocity vectors, sensor accuracies, and tracking filter parameters. eters. Depending upon the tracking filter implementation, these errors may also be a function of target bearing.     

Improved Feedback Loop for Adaptive Arrays

This paper is concerned with the problem of time constants in adaptive arrays. The paper presents a improved form of an adaptive array feedback loop, which has the property that its time constants are fixed. This property is an advantage over the well-known least mean square (LMS) loop, for which time constants depend on received signal power. Fixed time constants are of interest because they simplify dynamic range problems for adaptive arrays in communication and radar systems.     

Limiting Performance of Generalized Sign Test Detector

The limiting performance of the generalized sign test detector as the number M of target returns becomes infinite has been derived by Hansen and Olsen [1]. Simple expressions are derived herein for the limiting performance for finite M as K, the number of noise samples in the reference set, becomes infinite. Curves are presented which indicate how this limiting performance is approached as K is increased for both constant target returns and fluctuating target returns.