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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Analysis and test of a 16-foot radial rib reflector developmental model

Analytical and experimental modal tests were performed to determine the vibrational characteristics of a 16-foot diameter radial rib reflector model. Single rib analyses and experimental tests provided preliminary information relating to the reflector. A finite element model predicted mode shapes and frequencies of the reflector. The analyses correlated well with the experimental tests, verifying the modeling method used. The results indicate that five related, characteristic mode shapes form a group. The frequencies of the modes are determined by the relative phase of the radial ribs.

Birchenough, Shawn A.↗
NASA NTRS1989

Lightweight composite mirror analysis and testing

The Jet Propulsion Laboratory InterDisciplinary Model for precision composite structures is described along with the HAVOC composite computer code used to study laminate mirror facesheets. The composite mirror panel thermal behavior is described in addition to structural and optical characteristics. Environmental mirror performance testing and performance test/prediction correlation are covered.

Helms, R. G.↗
NASA NTRS1986

Multiperspective analysis and testing of expert systems

The paper describes a technique which the author developed for testing expert systems. The technique, which he calls multiperspective testing, can be applied during both the knowledge engineering phase and the acceptance testing phase of developing an exppert system. The first step in multiperspective testing is to define a group of performance measures ('perspectives') that focus on the behavior of the knowledge base. For each such measure, the results of testing are summarized in four scores, which the author calls 'expansion,' 'detection,' 'discrimination,' and 'comprehension.' These scores have the advantage of providing more specific information about how the knowledge base should be updated or corrected.

Bollinger, Terry B.↗
NASA NTRS1991

Laboratory test and acoustic analysis of cabin treatment for propfan test assessment aircraft

An aircraft cabin acoustic enclosure, built in support of the Propfan Test Assessment (PTA) program, is described. Helmholtz resonators were attached to the cabin trim panels to increase the sidewall transmission loss (TL). Resonators (448) were located between the trim panels and fuselage shell. In addition, 152 resonators were placed between the enclosure and aircraft floors. The 600 resonators were each tuned to a 235 Hz resonance frequency. After flight testing on the PTA aircraft, the enclosure was tested in the Kelly Johnson R and D Center Acoustics Lab. Laboratory noise reduction (NR) test results are discussed. The enclosure was placed in a Gulfstream 2 fuselage section. Broadband (138 dB overall SPL) and tonal (149 dB overall SPL) excitations were used in the lab. Tonal excitation simulated the propfan flight test excitation. The fundamental tone was stepped in 2 Hz intervals from 225 through 245 Hz. The resonators increase the NR of the cabin walls around the resonance frequency of the resonator array. The effects of flanking, sidewall absorption, cabin adsorption, resonator loading of trim panels, and panel vibrations are presented. Increases in NR of up to 11 dB were measured.

Kuntz, H. L.↗
NASA NTRS1991

Analysis and testing of a space crane articulating joint testbed

The topics are presented in viewgraph form and include: space crane concept with mobile base; mechanical versus structural articulating joint; articulating joint test bed and reference truss; static and dynamic characterization completed for space crane reference truss configuration; improved linear actuators reduce articulating joint test bed backlash; 1-DOF space crane slew maneuver; boom 2 tip transient response finite element dynamic model; boom 2 tip transient response shear-corrected component modes torque driver profile; peak root member force vs. slew time torque driver profile; and open loop control of space crane motion.

Thomas R Sutter↗
NASA NTRS1990

Design, analysis, and testing of a reusable wingbox for ballistic evaluation of composite structures

Future fighter aircraft will continue to be subjected to severe mechanical loading and ballistic impact. In the past aircraft primary wing structure was constructed predominantly with aluminum, but with increasing aircraft performance the need for more structurally efficient materials is necessary. In an attempt to achieve structural efficiency requirements, aircraft designers have begun using an increasing amount of composite materials. Composite materials were indicated to have a low level of ballistic tolerance in some applications. Composite materials possess the characteristic of structural tailoring, which was utilized to demonstrate that survivability can be designed into a structure. The combat flight environment subjects fighter aircraft wing structures to the effects of combined loading during ballistic impact. These loads were previously demonstrated independently, i.e., the application of structural load, hydrodynamic ram damage, and the effects of airflow. The objective was to design a reusable test fixture for the ballistic evaluation of advanced composite structures under all the effects of combined loading. The fixture that was developed provides a test bed that can completely simulate the flight environment of a generic fighter aircraft wing, but can be used for an indefinite number and variety of tests. It is intended that this fixture will provide a standardized method of ballistically evaluating an advanced composite primary wing structure. This fixture will be used to accomplish the development of designs and/or advanced concepts that lead to a survivable composite wing structure.

Baron, W. G.↗
NASA NTRS1992

Analysis and testing of propellant feed system priming process

This paper presents the analytical and the experimental results pertaining to the priming process of the propellant feed system with initial line pressures starting from 0 psia and greater. The analytical methods employ the method of characteristics to solve for the one-dimensional liquid transients in the liquid-full segments and the lumped inertia technique to model the dynamics of the partially filled segments or the two-phase segments. The advantages of these methods are (1) fluid compressibility and piping flexibility are accounted for in the solution; and (2) the characteristics method can be used in the solution of a complex system. The analytical results were compared with test results. Excellent correlation was obtained between predictions and test results verifying the essential aspects of the analytical modeling techniques and providing the foundation for analyzing a complicated network system.

Lin, T. Y.↗
NASA NTRS1992

Results from the testing and analysis of LDEF batteries

Batteries were used on the Long Duration Exposure Facility (LDEF) to provide power to both the active experiments and the experiment support equipment such as the Experiment Initiative System, Experiment Power and Data System (data acquisition system), and the Environment Exposure Control Canisters. Three different types of batteries were used: lithium sulfur dioxide (LiSO2), lithium carbon monofluoride (LiCF), and nickel cadmium (NiCd). A total of 92 LiSO2, 10 LiCF, and 1 NiCd batteries were flown on the LDEF. In addition, approximately 20 LiSO2 batteries were kept in cold storage at NASA LaRC. The various investigations and post-flight analyses of the flight and control batteries are reviewed. The primary objectives of these studies was to identify degradation modes (if any) of the batteries and to provide information useful to future spacecraft missions. Systems SIG involvement in the post-flight evaluation of LDEF batteries was two-fold: (1) to fund SAFT (original manufacturer of the LiSO2 batteries) to perform characterization of 13 LiSO2 batteries (10 flight and 3 control batteries); and (2) to integrate investigator results.

Spear, Steve↗
NASA NTRS1992

Results from testing and analysis of solar cells flown on LDEF

A brief discussion of the solar cell experiments flown on the Long Duration Exposure Facility (LDEF) is provided. The information presented is a collation of results published by the various experimenters. This process of collation and documentation is an ongoing Systems Special Investigation Group (SIG) effort. There are four LEO environments, operating individually and/or synergistically, that cause performance loss in solar cells: meteoroid and space debris, atomic oxygen, ultraviolet radiation, and charged particle radiation. In addition, the effects of contamination caused by outgassing of materials used on the specific spacecraft play a role in decreasing the light being transmitted through the coverglass and adhesive to the solar cell. From the results presented on the solar cells aboard LDEF, the most extensive degradation of the solar cells came from impacts and the resulting cratering. The extent of the damage to the solar cells was largely dependent upon the size and energy of the meteoroids or space debris. The other cause of degradation was reduced light reaching the solar cell. This was caused by contamination, UV degradation of coverglass adhesive, and/or atomic oxygen/UV degradation of antireflection coatings.

Dursch, Harry↗
NASA NTRS1992

System related testing and analysis of FRECOPA

Results from the French Cooperative Payload (FRECOPA) system analysis are presented. It was one of the numerous experiments which were flown on the Long Duration Exposure Facility (LDEF) satellite. In our flight configuration (LEO orbit, trailing edge), the environment was a better vacuum than the leading edge, with many thermal cycles (32000) and a large amount of UV radiation (11100 equivalent sun hours). Also, the satellite was mainly bombarded by micro-particles. It saw a low atomic flux and minor doses of protons and electrons.

Durin, Christian↗
NASA NTRS1993

Testing and analysis of curved frame specimens made from a Long Discontinuous Fiber (LDF) material

A long discontinuous fiber (LDF) material may be useful for constructing composite parts with complex curvature. Graphite-thermoplastic LDF curved frame specimens were studied to investigate the behavior of curved frame structures made from this material form. Experimental results for three curved frame specimens loaded in a four-point-bending configuration and finite-element predictions of strains and displacements are presented.

Jegley, Dawn C.↗
NASA NTRS1994

Laser/lidar analysis and testing

Section 1 of this report details development of a model of the output pulse frequency spectrum of a pulsed transversely excited (TE) CO2 laser. In order to limit the computation time required, the model was designed around a generic laser pulse shape model. The use of such a procedure allows many possible laser configurations to be examined. The output pulse shape is combined with the calculated frequency chirp to produce the electric field of the output pulse which is then computationally mixed with a local oscillator field to produce the heterodyne beat signal that would fall on a detector. The power spectral density of this heterodyne signal is then calculated. Section 2 reports on a visit to the LAWS laser contractors to measure the performance of the laser breadboards. The intention was to acquire data using a digital oscilloscope so that it could be analyzed. Section 3 reports on a model developed to assess the power requirements of a 5J LAWS instrument on a Spot MKII platform in a polar orbit. The performance was assessed for three different latitude dependent sampling strategies.

Spiers, Gary D.↗
NASA NTRS1992

Design, analysis, and testing of a metal matrix composite web/flange intersection

An experimental and analytical program to study the local design details of a typical T-shaped web/flange intersection made from a metal matrix composite is described. Loads creating flange bending were applied to specimens having different designs and boundary conditions. Finite element analyses were conducted on models of the test specimens to predict the structural response. The analyses correctly predict failure load, mode, and location in the fillet material in the intersection region of the web and the flange when specimen quality is good. The test program shows the importance of fabrication quality in the intersection region. The full-scale test program that led to the investigation of this local detail is also described.

Biggers, S. B.↗
NASA NTRS1996

Correlation of Structural Analysis and Test Results for the McDonnell Douglas Stitched/RFI All-Composite Wing Stub Box

The analytical and experimental results of an all-composite wing stub box are presented in this report. The wing stub box, which is representative of an inboard portion of a commercial transport high-aspect-ratio wing, was fabricated from stitched graphite-epoxy material with a Resin Film Infusion manufacturing process. The wing stub box was designed and constructed by the McDonnell Douglas Aerospace Company as part of the NASA Advanced Composites Technology program. The test article contained metallic load-introduction structures on the inboard and outboard ends of the graphite-epoxy wing stub box. The root end of the inboard load introduction structure was attached to a vertical reaction structure, and an upward load was applied to the outermost tip of the outboard load introduction structure to induce bending of the wing stub box. A finite element model was created in which the center portion of the wing-stub-box upper cover panel was modeled with a refined mesh. The refined mesh was required to represent properly the geometrically nonlinear structural behavior of the upper cover panel and to predict accurately the strains in the stringer webs of the stiffened upper cover panel. The analytical and experimental results for deflections and strains are in good agreement.

Wang, John T.↗
NASA NTRS1998

An Assessment of Molten Metal Detachment Hazards for Electron Beam Welding in the Space Environment: Analysis and Test Results

Conditions under which molten metal detachments might occur in a space welding environment are analyzed. A weld pool detachment parameter specifying conditions for pool detachment by impact is derived and corroborated by experimental evidence. Impact detachment for the pool is unlikely. Impact detachment for a drop of metal on the end of the weld wire may be possible under extreme conditions. Other potential causes of molten metal detachment considered, vaporization pressure forces and wire flickout from the pool, did not appear to present significant detachment threats.

Nunes, A. C., Jr.↗
NASA NTRS2000

Dynamic Investigation of Static Divergence: Analysis and Testing

The phenomenon known as aeroelastic divergence is the focus of this work. The analyses and experiment presented here show that divergence can occur without a structural dynamic mode losing its oscillatory nature. Aeroelastic divergence occurs when the structural restorative capability or stiffness of a structure is overwhelmed by the static aerodynamic moment. This static aeroelastic coupling does not require the structural dynamic system behavior to cease, however. Aeroelastic changes in the dynamic mode behavior are governed not only by the stiffness, but by damping and inertial properties. The work presented here supports these fundamental assertions by examining a simple system: a typical section airfoil with only a rotational structural degree of freedom. Analytical results identified configurations that exhibit different types of dynamic mode behavior as the system encounters divergence. A wind tunnel model was designed and tested to examine divergence experimentally. The experimental results validate the analytical calculations and explicitly examine the divergence phenomenon where the dynamic mode persists. Three configurations of the wind tunnel model were tested. The experimental results agree very well with the analytical predictions of subcritical characteristics, divergence velocity, and behavior of the noncritical dynamic mode at divergence.

Heeg, Jennifer↗