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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Milstar's flexible-substrate solar array: Lessons learned

The Flexible Substrate Solar Array (FSSA) is an evolutionary development of the lightweight, flexible substrate design pioneered during the seventies. Many of the features of the design are related to the Solar Array Flight Experiment (SAFE), flown on STS-41D in 1984. FSSA development has created a substantial technology base for future flexible substrate solar arrays such as the array for the Space Station Freedom. Lessons learned during the development of the FSSA can and should be applied to the Freedom array and other future flexible substrate designs.

Gibb, John↗
NASA NTRS1990

MILSTAR's flexible substrate solar array: Lessons learned, addendum

MILSTAR's Flexible Substrate Solar Array (FSSA) is an evolutionary development of the lightweight, flexible substrate design pioneered at Lockheed during the seventies. Many of the features of the design are related to the Solar Array Flight Experiment (SAFE), flown on STS-41D in 1984. FSSA development has created a substantial technology base for future flexible substrate solar arrays such as the array for the Space Station Freedom. Lessons learned during the development of the FSSA can and should be applied to the Freedom array and other future flexible substrate designs.

Gibb, John↗
NASA NTRS1992

Application of Computational Fluid Dynamics to the Study of Vortex Flow Control for the Management of Inlet Distortion

The present study demonstrates that the Reduced Navier-Stokes code RNS3D can be used very effectively to develop a vortex generator installation for the purpose of minimizing the engine face circumferential distortion by controlling the development of secondary flow. The computing times required are small enough that studies such as this are feasible within an analysis-design environment with all its constraints of time and costs. This research study also established the nature of the performance improvements that can be realized with vortex flow control, and suggests a set of aerodynamic properties (called observations) that can be used to arrive at a successful vortex generator installation design. The ultimate aim of this research is to manage inlet distortion by controlling secondary flow through an arrangements of vortex generators configurations tailored to the specific aerodynamic characteristics of the inlet duct. This study also indicated that scaling between flight and typical wind tunnel test conditions is possible only within a very narrow range of generator configurations close to an optimum installation. This paper also suggests a possible law that can be used to scale generator blade height for experimental testing, but further research in this area is needed before it can be effectively applied to practical problems. Lastly, this study indicated that vortex generator installation design for inlet ducts is more complex than simply satisfying the requirement of attached flow, it must satisfy the requirement of minimum engine face distortion.

Anderson, Bernhard H.↗
NASA NTRS1992

Application of computational fluid dynamics to the study of vortex flow control for the management of inlet distortion

A study is presented to demonstrate that the Reduced Navier-Stokes code RNS3D can be employed effectively to develop a vortex generator installation that minimizes engine face circumferential distortion by controlling the development of secondary flow. The necessary computing times are small enough to show that similar studies are feasible within an analysis-design environment with all its constraints of costs and time. This study establishes the nature of the performance enhancements that can be realized with vortex flow control, and indicates a set of aerodynamic properties that can be utilized to arrive at a successful vortex generator installation design.

Anderson, Bernhard H.↗
NASA NTRS1993

Active Suppression Of Vibrations On Elastic Beams

Pairs of colocated piezoelectric transducers, independently controlled by multichannel adaptive controller, employed as actuators and sensors to achieve simultaneous attenuation of both extensional and flexural motion. Single pair used to provide simultaneous control of flexural and extensional waves, or two pairs used to control torsional motion also. Capability due to nature of piezoelectric transducers, when bonded to surfaces of structures and activated by oscillating voltages, generate corresponding oscillating distributions of stresses in structures. Phases and amplitudes of actuator voltages adjusted by controller to impede flow of vibrational energy simultaneously, in waves of various forms, beyond locations of actuators. Concept applies equally to harmonic or random response of structure and to multiple responses of structure to transverse bending, torsion, and compression within structural element. System has potential for many situations in which predominant vibration transmission path through framelike structure.

Silcox, Richard J.↗
NASA NTRS1992

Method and apparatus for minimizing multiple degree of freedom vibration transmission between two regions of a structure

Arrays of actuators are affixed to structural elements to impede the transmission of vibrational energy. A single pair is used to provide control of bending and extensional waves and two pairs are used to control torsional motion. The arrays are applied to a wide variety of structural elements such as a beam structure that is part of a larger framework that may or may not support a rigid or non-rigid skin. Electrical excitation is applied to the actuators that generate forces on the structure. These electrical inputs may be adjusted in their amplitude and phase by a controller in communication with appropriate vibrational wave sensors to impede the flow of vibrational power in all of the above mentioned wave forms beyond the actuator location. Additional sensor elements can be used to monitor the performance and adjust the electrical inputs to maximize the attenuation of vibrational energy.

Silcox, Richard J.↗
NASA NTRS1993

Automated measurement of polarized bidirectional reflectance

An Automated Bidirectional Reflection Acquisition Measurement System (ABRAMS) has been constructed to facilitate measurement of bidirectional reflectance from soil and vegetative samples in the laboratory. The system illuminates a sample with linearly-polarized laser light, lambda = 632.8 nm, and measures the like- and cross-polarized scattered intensities over half a hemisphere. System design and polarized bidirectional reflectance measurements from a soil sample and SiO2 spherical particles are discussed in this work. It is shown that polarization information in the plane of incidence is useful for identifying certain scattering mechanisms associated with soil reflectance. This is because the like-polarized intensity, Ivv, is influenced by single-scattered light and the cross-polarized intensity, IHv, is strongly influenced by multiple-scattered light. For example, comparable levels of Ivv and IHv indicated that the reflectance of soils, is dominated by significant multiple scattering because single scattering causes minimal depolarization in the plane of incidence.

Gibbs, Daniel P.↗
NASA NTRS1956

Tensile properties of HK31XA-H24 magnesium-alloy sheet under rapid-heating conditions and constant elevated temperatures

Specimens of HK31XA-H24 magnesium-alloy sheet from an experimental batch were heated to failure at nominal temperature rates from 0.2 F to 100 F per second under constant-load conditions. Rapid-heating yield and rupture stresses are presented and compared with the yield and ultimate stresses from elevated-temperature tensile stress-strain tests for 1/2-hour exposure. Linear temperature-rate parameters were used to correlate rapid-heating results by constructing master curves which can be used for predicting yield stresses and temperatures and for estimating rupture stresses and temperatures.

MATERIALS, PROPERTIES - THERMAL↗
NASA NTRS1957

Preliminary investigation of the combustion of a 50 percent pentaborane - 50 percent JP-4 fuel blend in a turbojet combustor at simulated altitude conditions

A preliminary investigation was conducted to determine the combustion characteristics of a fuel composed of 50 percent pentaborane and 50 percent JP-4 (MIL-F-5624A) by weight in a turbojet combustor. A combustor designed to fit the housing of a J33-A-23 turbojet engine was selected for convenience. The fuel was evaluated at two engine conditions simulating altitudes of 40,000 and 57,000 feet, an engine speed of 85 percent of rated rpm, and a flight Mach number of 0.6. The pentaborane blend was initially evaluated in combustors developed for pure pentaborane and diborane reported in NACA RM E53B18 and RM E52L15. The performance of the blend was unsatisfactory in these combustors. A new combustor was then developed which provided combustor efficiencies measured from 91 to 101 percent as compared with efficiencies of 92 to 94 percent previously obtained for pentaborane at comparable conditions. Additional refinements of design details are needed to obtain lower oxide deposits and a more uniform outlet temperature profile; however, the combustor is believed to incorporate some of the design principles required to obtain satisfactory over-all performance with the fuel blend investigated.

FUELS - JP-4-*PENTABORANE↗
NASA NTRS1954

Starting characteristics and combustion performance of magnesium slurry in 6.5-inch-diameter ram-jet engine mounted in connected-pipe facility

The starting characteristics and combustion performance of slurry type fuels, consisting of 50 percent magnesium powder in a hydrocarbon carrier, have been investigated in a flight-type, 6.5-inch-diameter ram-jet engine in a connected-pipe facility. Quick, dependable starting of the engine was obtained by the use of a disk which blocked part of the combustor area downstream of the flame holder. Acceptable performance was achieved with a short fuel-air mixing length by the development of a fuel-distribution control sleeve.

COMBUSTION - RAM-JET ENGINES↗
NASA NTRS1957

Preliminary Investigation of Combustion of Diborane in a Turbojet Combustor

Boron and its hydrides offer increased flight range relative to conventional fuels for turbojet engines. Preliminary evaluation has been made of the combustion characteristics and deposition problems resulting from burning diborone in a single, modified J33 combustor. A combustor relatively free of deposits for the limited test conditions has been developed. Three possible methods of alleviating deposits on the turbine blades are reported.

Kaufman, Warner B↗
NASA NTRS1988

Software engineering as an engineering discipline

The goals of the Software Engineering Institute's Education Program are as follows: to increase the number of highly qualified software engineers--new software engineers and existing practitioners; and to be the leading center of expertise for software engineering education and training. A discussion of these goals is presented in vugraph form.

Gibbs, Norman↗