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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Method of Calibration for a Large Cathetometer System

A method of calibration has been devised for a pair of mutually orthogonal two-axis cathetometers that, when used together, yield measurements of three-dimensional positions of objects mounted on an optical bench. Each cathetometer has a horizontal travel of 1.8 m and a vertical travel of 1.2 m. The cathetometers are required to measure X, Y, and Z coordinates (see figure) to within plus or minus 0.005 in. (plus or minus 0.127 mm). Each cathetometer consists of an alignment telescope on a platform mounted on a two-dimensional translation stage. The knowledge required for calibration of each cathetometer is (1) the two-dimensional position of the cathetometer platform as a function of the electronic readouts of position encoders on the translation stage and (2) the amount of any angular misalignment (roll, pitch, and/or yaw) of the cathetometer platform as a function of the two-dimensional coordinates or the position-encoder readouts. By use of three equations derived from the applicable trigonometric relationships, the calibrated X, Y, and Z coordinates can be computed from the raw encoder readouts.

Toland, Ronald↗
NASA NTRS2012

Rotordynamic Feasibility of a Conceptual Variable-Speed Power Turbine Propulsion System for Large Civil Tilt-Rotor Applications

A variable-speed power turbine concept is analyzed for rotordynamic feasibility in a Large Civil Tilt-Rotor (LCTR) class engine. Implementation of a variable-speed power turbine in a rotorcraft engine would enable high efficiency propulsion at the high forward velocities anticipated of large tilt-rotor vehicles. Therefore, rotordynamics is a critical issue for this engine concept. A preliminary feasibility study is presented herein to address this concern and identify if variable-speed is possible in a conceptual engine sized for the LCTR. The analysis considers critical speed placement in the operating speed envelope, stability analysis up to the maximum anticipated operating speed, and potential unbalance response amplitudes to determine that a variable-speed power turbine is likely to be challenging, but not impossible to achieve in a tilt-rotor propulsion engine.

Howard, Samuel↗
NASA NTRS2012

Computationally efficient modeling and simulation of large scale systems

A method of simulating operation of a VLSI interconnect structure having capacitive and inductive coupling between nodes thereof. A matrix X and a matrix Y containing different combinations of passive circuit element values for the interconnect structure are obtained where the element values for each matrix include inductance L and inverse capacitance P. An adjacency matrix A associated with the interconnect structure is obtained. Numerical integration is used to solve first and second equations, each including as a factor the product of the inverse matrix X.sup.-1 and at least one other matrix, with first equation including X.sup.-1Y, X.sup.-1A, and X.sup.-1P, and the second equation including X.sup.-1A and X.sup.-1P.

Jain, Jitesh↗
NASA NTRS2014

Computationally Efficient Modeling and Simulation of Large Scale Systems

A system for simulating operation of a VLSI interconnect structure having capacitive and inductive coupling between nodes thereof, including a processor, and a memory, the processor configured to perform obtaining a matrix X and a matrix Y containing different combinations of passive circuit element values for the interconnect structure, the element values for each matrix including inductance L and inverse capacitance P, obtaining an adjacency matrix A associated with the interconnect structure, storing the matrices X, Y, and A in the memory, and performing numerical integration to solve first and second equations.

Jain, Jitesh↗
NASA NTRS1985

Large Space Antenna Systems Technology, 1984

Papers are presented which provide a comprehensive review of space missions requiring large antenna systems and of the status of key technologies required to enable these missions. Topic areas include mission applications for large space antenna systems, large space antenna structural systems, materials and structures technology, structural dynamics and control technology, electromagnetics technology, large space antenna systems and the space station, and flight test and evaluation.

Boyer, W. J.↗
NASA NTRS1988

Controls and guidance: Space

The Space Controls and Guidance Research and Technology Program is directed toward enabling the next generation of space transportation systems, large future spacecraft, and space systems such as the Space Station to have large communication antennas and high precision segmented reflector astrophysical telescopes. The new generation of transportation vehicles has demanding requirements to provide for an order of magnitude reduction in cost as well as an increase in capability. The future orbital facilities have demanding control requirements for pointing and stabilization, momentum management, build-up and growth accomodation, and disturbance management. To address these advanced requirements, the research and development program is designed to provide the generic technology base to support the implementation of advanced guidance, navigation, and control. The area of computational controls will be stressed in order to develop cost effective, high speed, high fidelity control system simulation and analysis and synthesis tools. The trust of this work will be to develop methods and software to enable analysis and real-time hardware-in-the-loop simulation of complex spacecraft for control design certification. To address future orbital facilities requirements, an advanced technology program is underway in system identification, distributed control, integrated controls/structures design methods, and advanced sensors and actuators. Because the behavior of large, light weight per unit area deployable/assembled spacecraft is greatly influenced by the ground environment, the testing and verification activity is both ground- and space-based.

Dibattista, John D.↗
NASA NTRS2014

OCSEGen: Open Components and Systems Environment Generator

To analyze a large system, one often needs to break it into smaller components.To analyze a component or unit under analysis, one needs to model its context of execution, called environment, which represents the components with which the unit interacts. Environment generation is a challenging problem, because the environment needs to be general enough to uncover unit errors, yet precise enough to make the analysis tractable. In this paper, we present a tool for automated environment generation for open components and systems. The tool, called OCSEGen, is implemented on top of the Soot framework. We present the tool's current support and discuss its possible future extensions.

User Specifications↗
NASA NTRS1998

Characterization of an Ozone DIAL Receiver for Operation on an Unpiloted Atmospheric Vehicle

Laser remote sensing from aircraft has become a very important technique for observing ozone in the environment. NASA Langley has an active aircraft based research program which presently uses Nd:YAG-pumped dye lasers that are then doubled into the UV to probe both the stratosphere and troposphere for ozone using the differential absorption lidar (DIAL) technique. This large system can only fly on large (NASA DC-8, Electra) aircraft and has been deployed on many missions throughout the world. In the future it will be desirable to fly autonomous, lightweight, compact ozone DIAL instruments on unpiloted atmospheric vehicles (UAV) aircraft. Such aircraft could fly at high altitudes for extended times collecting science data without risk to the operator. Cost for such missions may be substantially reduced over present large aircraft based missions. Presently there are no ozone DIAL systems capable of flying on an UAV aircraft. In order to facilitate UAV missions, small more efficient laser transmitters need to be developed that emit approximately 25mJ near 300nm for each of the DIAL 'on' and 'off' line pulses. Also lightweight, compact DIAL receiver systems need to be built and demonstrated. Such receiver systems may incorporate fiber optic coupled telescopes for maximum light gathering capability per unit area, high quantum efficiency gated photomultiplier tubes with reasonable gain and very narrow-band filters for background light rejection with high light throughput. A compact high-performance 16-bit digitizer and a data storage system are also required. A conceptional design of such a UAV DIAL instrument is presented. Here a pulsed UV laser emits pulses into the atmosphere where elastic scattering occurs which results in light being scattered into the receiver telescope. The subject of this paper is the design, construction and testing of a robust, compact ozone DIAL receiver system that would be a prototype for eventual use in a UAV aircraft.

Goldschmidt, Soenke↗
NASA NTRS1978

Interaction of large, high power systems with operational orbit charged particle environments

Concepts are presently being advanced for space systems to be used for such activities as manufacturing, earth observations, scientific exploration, power generation and human habitation, in locations ranging from low earth orbit (300-500 km) to geosynchronous orbit and beyond. Many of these systems concepts envision large structures and high power levels, and consequently higher operating voltages than have been used in space to date. The potential impact of interactions of space systems with their operational orbit charged particle environments on the systems' performance must be accounted for in the design process. A potentially hazardous spacecraft-environment interaction is discussed, namely the interaction of large high voltage systems with low energy (less than 50 eV) plasmas which can result in loss of power, and/or arcing. The impact of this class of interactions on system operation is most severe at low orbits where the ambient plasmas are densest. Results of experimental work and predictions of simple analytical models are presented and their implications for design of space systems are discussed.

Purvis, C. K.↗
NASA NTRS1976

Investigation of selected disk systems

The large disk systems offered by IBM, UNIVAC, Digital Equipment Corporation, and Data General were examined. In particular, these disk systems were analyzed in terms of how well available operating systems take advantage of the respective disk controller's transfer rates, and to what degree all available data for optimizing disk usage is effectively employed. In the course of this analysis, generic functions and components of disk systems were defined and the capabilities of the surveyed disk system were investigated.

Source record↗
NASA NTRS2017

Spaceport Command and Control System Software Development

The Spaceport Command and Control System (SCCS) is the National Aeronautics and Space Administration's (NASA) launch control system for the Orion capsule and Space Launch System, the next generation manned rocket currently in development. This large system requires a large amount of intensive testing that will properly measure the capabilities of the system. Automating the test procedures would save the project money from human labor costs, as well as making the testing process more efficient. Therefore, the Exploration Systems Division (formerly the Electrical Engineering Division) at Kennedy Space Center (KSC) has recruited interns for the past two years to work alongside full-time engineers to develop these automated tests, as well as innovate upon the current automation process.

Glasser, Abraham↗
NASA NTRS1976

Decentralization, stabilization, and estimation of large-scale linear systems

In this short paper we consider three closely related aspects of large-scale systems: decentralization, stabilization, and estimation. A method is proposed to decompose a large linear system into a number of interconnected subsystems with decentralized (scalar) inputs or outputs. The procedure is preliminary to the hierarchic stabilization and estimation of linear systems and is performed on the subsystem level. A multilevel control scheme based upon the decomposition-aggregation method is developed for stabilization of input-decentralized linear systems Local linear feedback controllers are used to stabilize each decoupled subsystem, while global linear feedback controllers are utilized to minimize the coupling effect among the subsystems. Systems stabilized by the method have a tolerance to a wide class of nonlinearities in subsystem coupling and high reliability with respect to structural perturbations. The proposed output-decentralization and stabilization schemes can be used directly to construct asymptotic state estimators for large linear systems on the subsystem level. The problem of dimensionality is resolved by constructing a number of low-order estimators, thus avoiding a design of a single estimator for the overall system.

Siljak, D. D.↗