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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 1,153 records · Page 64

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NASA NTRS1981

Flight test results of an active flutter suppression system installed on a remotely piloted research vehicle

Flight flutter test results of the first aeroelastic research wing of NASA's Drones for Aerodynamic and Structural Testing (DAST) program are presented. The implementation of the flutter suppression system and the flight test operation are described. The conduct of the flutter testing and the near-real time damping estimation algorithm are also described in detail. Flight data was obtained at Mach numbers up to 0.91 and was of high quality. Response to fast frequency sweep excitation provided reliable damping estimates and the open-loop flutter boundary was well defined. Evidence of angle-of-attack effects upon damping at high transonic Mach numbers is also presented. While the flutter suppression system provided augmented damping at speeds below the flutter boundary, an error in the implementation of the system gain caused the system to be less stable than predicted and the vehicle encountered system-on flutter on the third flight.

Edwards, J. W.↗

NASA NTRS1981

The potential evolution of the space transportation system

An evolutionary plan satisfying the requirements of permanent manned space stations in low orbit by 1990 along with geostationary orbit sortie capabilities by 2000 is proposed. The program, to be gradually implemented with near-term technology, comprises: (1) unmanned platforms in low and geostationary orbits; (2) growth and development of these platforms into manned systems; (3) satellite checkout, handling, repair and maneuvering by means of special techniques, such as teleoperated docking, berthing and component exchange; and (4) transportation, by means of unmanned, cargo-carrying derivatives of the Space Shuttle and reuseable, space-based orbit transfer vehicles. Attention is given the envisioned configurations of both manned and unmanned orbital platforms, through a series of progress diagrams.

Bekey, I.↗

NASA NTRS1981

As-Built design specification for PARPLT

The design and implementation of the PARPLT program are described. The program produces scatter plots of the greenness profile derived parameters alpha, beta, and t sub o computed by the CLASFYG program (alpha being the approximate greenness rise time; beta, the greenness decay time; and t sub o, the spectral crop emergence date). Statistical information concerning the parameters is also computed.

Tompkins, M. A.↗

NASA NTRS1982

Beyond the supercomputer

A NASA-directed development of massively parallel processor (MPP) computers is outlined, noting intended applications for data processing for near term earth resource and environment mapping, radar, and television transmissions. The MPP is designed to perform 100 billion operations/sec to obtain satisfactory image processing, while separate processing units correct distortions, register images, calculate correlation functions, and classify multispectral characteristics. Arrays of 1s and 0s will be manipulated in analog-to-digital conversions generating separate planes corresponding to powers of binaries. Data wires are replaced by fiber-optic tubes or thousands of wires, and single logic gates are replaced by thousands of logic gates and every memory element by thousands of memory elements. Features of the interconnections and the images control processor units are detailed, along with implementation of sliders for program flexibility.

Schaefer, D. H.↗

NASA NTRS1983

Phase Calibration for the Block 1 VLBI System

Very Long Baseline Interferometry (VLBI) in the DSN provides support for spacecraft navigation, Earth orientation measurements, and synchronization of network time and frequency standards. An improved method for calibrating instrumental phase shifts has recently been implemented as a computer program in the Block 1 system. The new calibration program, called PRECAL, performs calibrations over intervals as small as 0.4 seconds and greatly reduces the amount of computer processing required to perform phase calibration.

Roth, M. G.↗

NASA NTRS1983

Design issues in the GCF Mark 4 development

Some of the major design problems facing the computer based Ground Communications Facility (GCF) Digital Communication System for the Mark 4 Network Consolidation Program are discussed. The solutions to each as implemented in the software of the GCF Operation Programs are proposed.

Crowe, R. A.↗

NASA NTRS1984

Space Station Technology, 1983

This publication is a compilation of the panel summaries presented in the following areas: systems/operations technology; crew and life support; EVA; crew and life support: ECLSS; attitude, control, and stabilization; human capabilities; auxillary propulsion; fluid management; communications; structures and mechanisms; data management; power; and thermal control. The objective of the workshop was to aid the Space Station Technology Steering Committee in defining and implementing a technology development program to support the establishment of a permanent human presence in space. This compilation will provide the participants and their organizations with the information presented at this workshop in a referenceable format. This information will establish a stepping stone for users of space station technology to develop new technology and plan future tasks.

Wright, R. L.↗

NASA NTRS1985

Research in computer science

Synopses are given for NASA supported work in computer science at the University of Virginia. Some areas of research include: error seeding as a testing method; knowledge representation for engineering design; analysis of faults in a multi-version software experiment; implementation of a parallel programming environment; two computer graphics systems for visualization of pressure distribution and convective density particles; task decomposition for multiple robot arms; vectorized incomplete conjugate gradient; and iterative methods for solving linear equations on the Flex/32.

Ortega, J. M.↗

NASA NTRS1986

A survey of functional programming language principles

Research in the area of functional programming languages has intensified in the 8 years since John Backus' Turing Award Lecture on the topic was published. The purpose of this paper is to present a survey of the ideas of functional programming languages. The paper assumes the reader is comfortable with mathematics and has knowledge of the basic principles of traditional programming languages, but does not assume any prior knowledge of the ideas of functional languages. A simple functional language is defined and used to illustrate the basic ideas. Topics discussed include the reasons for developing functional languages, methods of expressing concurrency, the algebra of functional programming languages, program transformation techniques, and implementations of functional languages. Existing functional languages are also mentioned. The paper concludes with the author's opinions as to the future of functional languages. An annotated bibliography on the subject is also included.

Holloway, C. M.↗

NASA NTRS1987

Development of an LED display system for cross-track distance and velocity for Loran-C flight

The methodology for estimating cross-track velocity by combining rate-gyro and Loran-C data is illustrated in block diagrams. At present, preliminary analysis has established values for K sub 1, K sub 2, the parameters of the digital control loops. A computer program was written to implement a digital simulation of the system as illustrated. Given a model for the noise in the rate-gyro and Loran-C receiver, and their dynamic response, the simulation provides a working model to establish good control loop parameters. The layout of the LED display for flight testing of Loran-C approach flying, which was constructed during a visit to Langley Research Center, is shown. Four bar-graph LED displays are paired to provide cross-track distance and velocity from a Loran-C defined runway centerline. Two seven-segment LED displays are used to provide alphanumeric readout of range to touchdown and desired height. A metal case was built, a circuit board designed, and manufactured with the assistance of NASA Langley personnel.

Dogan, Norry↗

NASA NTRS1987

Effect of shaft frequency on cavitation in a journal bearing for noncentered circular whirl

The effect of shaft frequency on the performance of a submerged journal undergoing noncentered circular whirl is examined. The main emphasis of the paper is on the behavior of the vapor cavitation bubble and its effect on the bearing performance as a function of frequency. A cavitation algorithm due to Elrod was implemented in a computer program which solves a time-dependent Reynolds equation. This algorithm automatically handles the boundary conditions by using a switch function and a control volume approach which conserves mass throughout the entire flow. The shaft frequencies in this investigation ranged from 0 rad/s (squeeze-film damper) to -104 rad/s (a case in which oil-whip condition was produced momentarily). For the particular vibration amplitude chosen in this investigation it was observed that vapor cavitation had an effect on the load components for the full range of shaft frequencies investigated.

Brewe, David E.↗

NASA NTRS1987

The development and implementation of cockpit resource management in UAL recurrent training

Line Oriented Flight Training (LOFT) for United Airlines started in 1976. At that time it was basically no more than a line-simulated training function conducted in a full-mission simulator with no attention or stress on its human factor content. Very soon after the implementation of the LOFT program concerns were voiced about certain crew behavioral situations they were observing in the flight crew's execution of cockpit duties. These duties involved emergency procedures as well as irregular and normal procedures and situations. It was evident that new information was surfacing concerning crew interaction, or its lack thereof, in the cockpit and its effect on satisfactory performance. These observations naturally raised the question of how this information translated into the safety of aircraft operations. A training system had to be repetitive, the crew interactive, and the training had to be conducted under the crew concept. The foundation had to have two other factors: (1) it was necessary to have adequate human factor content, and (2) an advanced state-of-the-art simulator and appropriate electronic devices were required. These concepts are further discussed.

Shroyer, David H.↗

NASA NTRS1987

Spacecraft 2000: The challenge of the future

Considerable opportunity exists to improve the systems, subsystems, components, etc., included in the space station bus, the non-payload portion of the spacecraft. The steps followed to date, the challenges being faced by industry, and the progress toward establishing a new NASA initiative which will identify the technologies required to build spacecraft of the 21st century and which will implement the technology development/validation programs necessary are described.

Brandhorst, Henry W., Jr.↗

NASA NTRS1986

Optimum structural sizing of conventional cantilever and joined wing configurations using equivalent beam models

The present paper describes an approach for the optimum sizing of single and joined wing structures that is based on representing the built-up finite element model of the structure by an equivalent beam model. The low order beam model is computationally more efficient in an environment that requires repetitive analysis of several trial designs. The design procedure is implemented in a computer program that requires geometry and loading data typically available from an aerodynamic synthesis program, to create the finite element model of the lifting surface and an equivalent beam model. A fully stressed design procedure is used to obtain rapid estimates of the optimum structural weight for the beam model for a given geometry, and a qualitative description of the material distribution over the wing structure. The synthesis procedure is demonstrated for representative single wing and joined wing structures.

Hajela, P.↗

NASA NTRS1987

Reduced complexity structural modeling for automated airframe synthesis

A procedure is developed for the optimum sizing of wing structures based on representing the built-up finite element assembly of the structure by equivalent beam models. The reduced-order beam models are computationally less demanding in an optimum design environment which dictates repetitive analysis of several trial designs. The design procedure is implemented in a computer program requiring geometry and loading information to create the wing finite element model and its equivalent beam model, and providing a rapid estimate of the optimum weight obtained from a fully stressed design approach applied to the beam. The synthesis procedure is demonstrated for representative conventional-cantilever and joined wing configurations.

Hajela, Prabhat↗

NASA NTRS1987

Experimental aerothermodynamic research of hypersonic aircraft

The 2-D and 3-D advance computer codes being developed for use in the design of such hypersonic aircraft as the National Aero-Space Plane require comparison of the computational results with a broad spectrum of experimental data to fully assess the validity of the codes. This is particularly true for complex flow fields with control surfaces present and for flows with separation, such as leeside flow. Therefore, the objective is to provide a hypersonic experimental data base required for validation of advanced computational fluid dynamics (CFD) computer codes and for development of more thorough understanding of the flow physics necessary for these codes. This is being done by implementing a comprehensive test program for a generic all-body hypersonic aircraft model in the NASA/Ames 3.5 foot Hypersonic Wind Tunnel over a broad range of test conditions to obtain pertinent surface and flowfield data. Results from the flow visualization portion of the investigation are presented.

Cleary, Joseph W.↗

NASA NTRS1987

Mathematical model for the dc-ac inverter for the Space Shuttle

The reader is informed of what was done for the mathematical modeling of the dc-ac inverter for the Space Shuttle. The mathematical modeling of the dc-ac inverter is an essential element in the modeling of the electrical power distribution system of the Space Shuttle. The electrical power distribution system which is present on the Space Shuttle is made up to 3 strings each having a fuel cell which provides dc to those systems which require dc, and the inverters which convert the dc to ac for those elements which require ac. The inverters are units which are 2 wire structures for the main dc inputs and 2 wire structures for the ac output. When 3 are connected together a 4 wire wye connection results on the ac side. The method of modeling is performed by using a Least Squares curve fitting method. A computer program is presented for implementation of the model along with graphs and tables to demonstrate the accuracy of the model.

Berry, Frederick C.↗

NASA NTRS1988

Faultfinder: A diagnostic expert system with graceful degradation for onboard aircraft applications

A research effort was conducted to explore the application of artificial intelligence technology to automation of fault monitoring and diagnosis as an aid to the flight crew. Human diagnostic reasoning was analyzed and actual accident and incident cases were reconstructed. Based on this analysis and reconstruction, diagnostic concepts were conceived and implemented for an aircraft's engine and hydraulic subsystems. These concepts are embedded within a multistage approach to diagnosis that reasons about time-based, causal, and qualitative information, and enables a certain amount of graceful degradation. The diagnostic concepts are implemented in a computer program called Faultfinder that serves as a research prototype.

Abbott, Kathy H.↗