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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Investigation of Multi-Input, Multi-Output (MIMO) Random Control Applied to Direct Field Acoustic Testing

Direct Field Acoustic Testing (DFAT) offers potential cost and time savings over reverberant chamber acoustic testing of spacecraft. The NASA Multi-Purpose Crew Vehicle (MPCV) Program recently directed a series of acoustic tests on Orion structural test articles comparing DFAT and reverberant testing of the same test article with a view to qualifying DFAT for manned space flight vehicles. The verification process compared four parameters noise level compliance with the one third octave test specification, spatial uniformity of the acoustic field, spatial correlation of the acoustic field and vibration response of vehicle structure, including representative solar array panels. While the results of the verification were encouraging, MPCV Loads and Dynamics engaged Quartus Engineering to investigate whether alternative MIMO random control strategies might improve the spatial uniformity and/or the spatial correlation of the DFAT acoustic field. This paper presents the results of acoustic field simulations of the DFAT test and provides a better understanding of how MIMO random control systems originally developed for vibration and structural durability testing can be expected to perform in DFAT testing.

Direct Field↗
NASA NTRS2001

In-Space Structural Validation Plan for a Stretched-Lens Solar Array Flight Experiment

This paper summarizes in-space structural validation plans for a proposed Space Shuttle-based flight experiment. The test article is an innovative, lightweight solar array concept that uses pop-up, refractive stretched-lens concentrators to achieve a power/mass density of at least 175 W/kg, which is more than three times greater than current capabilities. The flight experiment will validate this new technology to retire the risk associated with its first use in space. The experiment includes structural diagnostic instrumentation to measure the deployment dynamics, static shape, and modes of vibration of the 8-meter-long solar array and several of its lenses. These data will be obtained by photogrammetry using the Shuttle payload-bay video cameras and miniature video cameras on the array. Six accelerometers are also included in the experiment to measure base excitations and small-amplitude tip motions.

Pappa, Richard S.↗
NASA NTRS1981

Franck-Condon factor formulae for astrophysical and other molecules

Simple closed-form, approximate, analytic expressions for Franck-Condon factors are given. They provide reliable estimates for Franck-Condon factor arrays for molecular band systems for which only vibrational-frequency, equilibrium internuclear separation and reduced mass values are known, as is often the case for astrophysically interesting molecules such as CeO, CoH, CrH, CrO, CuH, GeH, LaO, NiH, SnH, and ZnH for band systems of which Franck-Condon arrays have been calculated.

Nicholls, R. W.↗
NASA NTRS1993

Optical information processing at NASA Ames Research Center

The combination of analog optical processors with digital electronic systems offers the potential of tera-OPS computational performance, while often requiring less power and weight relative to all-digital systems. NASA is working to develop and demonstrate optical processing techniques for on-board, real time science and mission applications. Current research areas and applications under investigation include optical matrix processing for space structure vibration control and the analysis of Space Shuttle Main Engine plume spectra, optical correlation-based autonomous vision for robotic vehicles, analog computation for robotic path planning, free-space optical interconnections for information transfer within digital electronic computers, and multiplexed arrays of fiber optic interferometric sensors for acoustic and vibration measurements.

Reid, Max B.↗
NASA NTRS1995

The solar array-induced disturbance of the Hubble Space Telescope pointing system

The investigation of the vibrational disturbances of the Hubble Space Telescope that were discovered soon after deployment in orbit is described in detail. It was found that the disturbances were particularly evident during orbital day-night crossings, and that the magnitudes of the disturbances were considerably larger than the design jitter requirements. This paper describes the process by which the vibrations were characterized and isolated to a particular mechanism. The analysis of the flight data and comparisons with computer simulation results showed that the source of the disturbances was the thermally driven deformation of the solar arrays in conjunction with frictional effects in the array mechanisms. The control system was successfully modified to attenuate the disturbances to tolerable levels pending mechanical and thermal redesign of the solar arrays. The new arrays were installed during the first space telescope servicing mission and, in combination with the enhanced control system algorithm, reduced the disturbances to satisfactory levels.

Foster, C. L.↗
NASA NTRS1995

Solar-Array-Induced Disturbance of the Hubble Space Telescope Pointing System

The investigation of the vibrational disturbances of the Hubble Space Telescope that were discovered soon after deployment in orbit is described in detail. It was found that the disturbances were particularly evident during orbital day-night crossings, and that the magnitude of the disturbances was considerably larger than the design jitter requirement. This paper describes the process by which the vibrations were characterized and isolated to a particular mechanism. The analysis of the flight data and comparisons with computer simulation results showed that the source of the disturbances was the thermally driven deformation of the solar arrays in conjunction with frictional effects in the array mechanisms. The control system was successfully modified to attenuate the disturbances to tolerable levels pending mechanical and thermal redesign of the solar arrays. The new arrays were installed during the first Space Telescope servicing mission, and in combination with the enhanced control system algorithm reduced the disturbances to satisfactory levels.

Foster, Carlton L.↗
NASA NTRS1975

Dynamic substructure analysis of the International Ultraviolet Explorer (IUE) spacecraft

The results are presented of a steady state vibration analysis of the IUE spacecraft simulating its sinusoidal vibration test. The model of the spacecraft, including solar arrays and the scientific instrument, consisted of three separate substructure models one of which was used to represent the two identical solar arrays. Substructuring techniques were used since the large overall size of the problem precluded solving it utilizing a single model. The models used for each substructure are discussed, including reduction to an acceptable size for the combined dynamic analysis. The DMAP alters needed for performing the modal analysis and the subsequent modal frequency response and substructure data recovery are included. Comparison of the results with data obtained during vibration tests of the spacecraft are also included.

Case, W. R.↗
NASA NTRS1986

Noise-Path Measurements in Aircraft Structures

System determines amount of radiated sound power separately attributed to airborne and structure-borne paths in aircraft. Also used to evaluate vibrating plates and thin shells. Sound transducers include array of lightweight, miniature piezoelectric accelerometers and two-microphone probe. Multichannel Fast Fourier Transform (FFT) analyzer/computer used for analog-to-digital conversion and to analyze spectrum of each of input signals. Noise-path identification in aircraft performed in flight by this system.

Mcgary, M. C.↗
NASA NTRS1989

Environmental testing of a diode-laser-pumped Nd:YAG laser and a set of diode-laser-arrays

Results of the environmental test of a compact, rigid and lightweight diode-laser-pumped Nd:YAG laser module are discussed. All optical elements are bonded onto the module using space applicable epoxy, and two 200 mW diode laser arrays for pump sources are used to achieve 126 mW of CW output with about 7 percent electrical-to-optical conversion efficiency. This laser assembly and a set of 20 semiconductor diode laser arrays were environmentally tested by being subjected to vibrational and thermal conditions similar to those experienced during launch of the Space Shuttle, and both performed well. Nevertheless, some damage to the laser front facet in diode lasers was observed. Significant degradation was observed only on lasers which performed poorly in the life test. Improvements in the reliability of the Nd:YAG laser are suggested.

Hemmati, H.↗
NASA NTRS1984

The use of an optical data acquisition system for bladed disk vibration analysis

A new concept in instrumentation was developed by engineers at NASA Lewis Research Center to collect vibration data from multi-bladed rotors. This new concept, known as the optical data acquisition system, uses optical transducers to measure bladed tip delections by reflection light beams off the tips of the blades as they pass in front of the optical transducer. By using an array of transducers around the perimeter of the rotor, detailed vibration signals can be obtained. In this study, resonant frequencies and mode shapes were determined for a 56 bladed rotor using the optical system. Frequency data from the optical system was also compared to data obtained from strain gauge measurements and finite element analysis and was found to be in good agreement.

Lawrence, C.↗
NASA NTRS1985

The use of an optical data acquisition system for bladed disk vibration analysis

A new concept in instrumentation was developed by engineers at NASA Lewis Research Center to collect vibration data from multi-bladed rotors. This new concept, known as the optical data acquisition system, uses optical transducers to measure bladed tip deflections by reflection of light beams off the tips of the blades as they pass in front of the optical transducer. By using an array of transducers around the perimeter of the rotor, detailed vibration signals can be obtained. In this study, resonant frequencies and mode shapes were determined for a 56 bladed rotor using the optical system. Frequency data from the optical system was also compared to data obtained from strain gauge measurements and finite element analysis and was found to be in good agreement.

Lawrence, C.↗
NASA NTRS2021

Relocatable 10 kW Solar Array for Lunar South Pole Missions

Deployable, relocatable, free-standing solar arrays are being developed to provide modular power for future lunar South Pole missions. Major design requirements for these arrays will be low mass, compact launch stowage, and highly reliable deployment and retraction. This paper presents a novel conceptual design for a10 kW solar array to address these requirements referred to as the Relocatable Solar Array (RSA).Simply stated, the concept is a pair of solar cell blankets freely hanging from a horizontal cross arm supported by a vertical, slender, telescoping mast resting on a deployable tripod base. A major factor in simplifying the design is that the force exerted by lunar gravity is used to deploy and maintain extension of the hanging array blankets. A second major factor in achieving the desired low mass and high volumetric efficiency is that the array operates in the vacuum, low-gravity, lunar environment with no deployed vibration frequency requirement. Such a low-load environment enables use of extraordinarily slender and low mass structural members to support the hanging array blankets. This concept was developed, in part, to serve as a NASA reference solar array concept against which other proposed arrays can be compared.

Lunar Surface Power↗
NASA NTRS1995

Simulation of the photogrammetric appendage structural dynamics experiment

The Photogrammetric Appendage Structural Dynamics Experiment (PASDE) uses six video cameras in the Space Shuttle cargo bay to measure vibration of the Russian Mir space station Kvant-ll solar array. It occurs on Shuttle/Mir docking mission STS-74 scheduled for launch in November 1995. The objective of PASDE is to demonstrate photogrammetric technology for measuring 'untargeted' spacecraft appendage structural dynamics. This paper discusses a pre-flight simulation test conducted in July 1995, focusing on the image processing aspects. The flight camera system recorded vibrations of a full-scale structural test article having grids of white lines on black background, similar in appearance to the Mir solar array. Using image correlation analysis, line intersections on the structure are tracked in the video recordings to resolutions of less than 0.1 pixel. Calibration and merging of multiple camera views generated 3-dimensional displacements from which structural modal parameters are then obtained.

Pappa, Richard S.↗
NASA NTRS2001

Status of the Direct Data Distribution (D(exp 3)) Experiment

NASA Glenn Research Center's Direct Data Distribution (D3) project will demonstrate an advanced, high-performance communications system that transmits information from an advanced technology payload carried by a NASA spacecraft in low Earth orbit (LEO) to a small receiving terminal on Earth. The space-based communications package will utilize a solid-state, K-band phased-array antenna that electronically steers the radiated energy beam toward a low-cost, tracking ground terminal, thereby providing agile, vibration-free, electronic steering at reduced size and weight with increased reliability. The array-based link will also demonstrate new digital processing technology that will allow the transmission of substantially increased amounts of latency-tolerant data collected from the LEO spacecraft directly to NASA field centers, principal investigators, or into the commercial terrestrial communications network. The technologies demonstrated by D3 will facilitate NASA's transition from using Government-owned communication assets to using commercial communication services. The hardware for D3 will incorporate advanced technology components developed under the High Rate Data Delivery (HRDD) Thrust Area of NASA's Office of Aerospace Technology Space Base Program at Glenn's Communications Technology Division. The flight segment components will include the electrically steerable phased-array antenna, which is being built by the Raytheon System Corporation and utilizes monolithic microwave integrated circuit (MMIC) technology operating at 19.05 GHz; and the digital encoder/modulator chipset, which uses four-channel orthogonal frequency division multiplexing (OFDM). The encoder/modulator will use a chipset developed by SICOM, Inc., which is both bandwidth and power efficient. The ground segment components will include a low-cost, open-loop tracking ground terminal incorporating a cryoreceiver to minimize terminal size without compromising receiver capability. The project is planning to hold a critical design review in the second quarter of fiscal year 2002.

Wald, Lawrence↗
NASA NTRSDate not supplied

Government Reference Concept for a 10 kW Lunar South Pole Solar Array

Deployable and relocatable free-standing, solar arrays will be required for future lunar South Pole missions. Major design requirements for these arrays will be low mass, compact launch stowage, and highly reliable deployment and retraction performance. A novel conceptual design referred to as the Relocatable Solar Array (RSA) is presented fora 10 kW solar array to address these requirements. Simply stated, the concept is a pair of solar cell blankets freely hanging from a horizontal cross arm that is supported by a vertical slender telescoping mast, all of which, rests on a deployable tripod base. A major factor in simplifying this array is that the force exerted by lunar gravity is used to deploy and maintain the extension of the hanging array blankets. The other major factor in achieving the desired low mass and high volumetric efficiency is that the resulting array system operates in the vacuum, low-gravity, lunar environment with no deployed vibration frequency requirement. Such an environment enables the use of extraordinarily slender and low mass structural members to support the hanging array blankets. This concept was developed, in part, to serve as a NASA reference solar array concept against which other proposed arrays can be compared.

Space solar arrays, solar array structures, lunar ↗
NASA NTRS2004

Solar Array Panels With Dust-Removal Capability

It has been proposed to incorporate piezoelectric vibrational actuators into the structural supports of solar photovoltaic panels, for the purpose of occasionally inducing vibrations in the panels in order to loosen accumulated dust. Provided that the panels were tilted, the loosened dust would slide off under its own weight. Originally aimed at preventing obscuration of photovoltaic cells by dust accumulating in the Martian environment, the proposal may also offer an option for the design of solar photovoltaic panels for unattended operation at remote locations on Earth. The figure depicts a typical lightweight solar photovoltaic panel comprising a backside grid of structural spars that support a thin face sheet that, in turn, supports an array of photovoltaic cells on the front side. The backside structure includes node points where several spars intersect. According to the proposal, piezoelectric buzzers would be attached to the node points. The process of designing the panel would be an iterative one that would include computational simulation of the vibrations by use of finite- element analysis to guide the selection of the vibrational frequency of the actuators and the cross sections of the spars to maximize the agitation of dust.

Dawson, Stephen↗
NASA NTRS2003

Laser-Ablated Ba(0.50)Sr(0.50)TiO3/LaAlO3 Films Analyzed Statistically for Microwave Applications

Scanning phased-array antennas represent a highly desirable solution for futuristic near-Earth and deep space communication scenarios requiring vibration-free, rapid beam steering and enhanced reliability. The current state-of-practice in scanning phased arrays is represented by gallium arsenide (GaAs) monolithic microwave integrated circuit (MMIC) technology or ferrite phase shifters. Cost and weight are significant impediments to space applications. Moreover, conventional manifold-fed arrays suffer from beam-forming loss that places considerable burden on MMIC amplifiers. The inefficiency can result in severe thermal management problems.

Romanofsky, Robert R.↗