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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Analysis and test of bonded single lap joints with preformed adherends

A theoretical and experimental study has been conducted to investigate the load transfer of a single lap joint where the adherends have been preformed so that the angle between the line of action of the applied in-plane force and the bond line is reduced. The preforming of the adherend reduces the moment resultant in the adherend at the edge of the overlap region which reduces both the maximum peel and shear stresses in the adhesive, and gives a more uniform shear distribution in the adhesive. An increase in static load transfer of up to 120 percent has been shown, and several orders of magnitude increase in fatigue life have been achieved with modest preform angles. Thus, sizeable benefits can be obtained in the fatigue life or additional load capacity of bonded single lap joints by preforming the adherends.

Sawyer, J. W.↗
NASA NTRS1982

Mapping of deciduous forest cover using simulated Landsat-D TM data

An evaluation is presented of the supervised vegetation classification images of heavily forested terrain in the eastern US produced from simulated Landsat-D Thematic Mapper data as part of the Joint NASA/Geosat Test Case study of the Lost River, West Virginia, gas field. This investigation utilized data supplied by the NS-001 aircraft multispectral scanner (15 m IFOV) of NASA. The instruments recognized a total of 9 vegetation classes and one soil class. A hybrid parallelepiped-Bayesian maximum likelihood classifier was employed to produce the supervised vegetation classifications. The data were obtained at the height of the fall foliage display for this portion of West Virginia. Results show that both classifications are highly accurate, based on a comparison of assignment of vegetation classes on each of the images with actual ground conditions. It is noted that the anomalous distribution of certain woody species found in the resulting supervised classifications may be related to the microseepage of methane from the gas reservoir.

Rock, B. N.↗
NASA NTRS1984

Results of the joint NASA/NOAA AMTS/HIRS2 sounding simulation test

The relative accuracies of atmospheric temperature profiles retrieved from HIRS2, the current operational infra-red temperature sounder, and AMTS, a proposed advanced high-spectral resolution infra-red sounder were compared. The sounding simulation test compared retrievals generated by GLAS, using their physical retrieval algorithm, and NESDIS, using their operational statistical regression algorithm, for both instruments under clear and cloudy conditions. Test results for both conditions are summarized in tables showing RMS temperature errors for 18 tropospheric layers, 4 stratospheric layers, and surface skin temperature. The improvement of the AMTS instrument over HIRS2, particularly for cloudy conditions is demonstrated. The GLAS retrievals are more accurate than the operational NESDIS retrieval, especially with increasing cloud cover.

Susskind, J.↗
NASA NTRS1984

Fracture of composite-adhesive-composite systems

This program was undertaken to initiate the development of a test method for testing adhesive joints in metal-adhesive-composite systems. The uniform double cantilever beam (UDCB) and the width tapered beam (WTB) specimen geometries were evaluated for measuring Mode I fracture toughness in these systems. The WTB specimen is the preferred geometry in spite of the fact that it is more costly to machine than the UDCB specimen. The use of loading tabs attached to thin sheets of composites proved to be experimentally unsatisfactory. Consequently, a new system was developed to load thin sheets of adherends. This system allows for the direct measurement of displacement along the load line. In well made joints separation occurred between the plies rather than in the adhesive.

Ripling, E. J.↗
NASA NTRS1987

Modeling of joints for the dynamic analysis of truss structures

An experimentally-based method for determining the stiffness and damping of truss joints is described. The analytical models use springs and both viscous and friction dampers to simulate joint load-deflection behavior. A least-squares algorithm is developed to identify the stiffness and damping coefficients of the analytical joint models from test data. The effects of nonlinear joint stiffness such as joint dead band are also studied. Equations for predicting the sensitivity of beam deformations to changes in joint stiffness are derived and used to show the level of joint stiffness required for nearly rigid joint behavior. Finally, the global frequency sensitivity of a truss structure to random perturbations in joint stiffness is discussed.

Belvin, W. Keith↗
NASA NTRS1986

Exploratory wind-tunnel investigation of the stability and control characteristics of advanced general aviation configurations

Results of low-speed wind-tunnel investigations are presented for two general aviation configurations: the AVTEK canard configuration and the DeVore conventional configuration. Cooperative research programs were undertaken by industry and NASA to jointly conduct tests in the NASA Langley 12-Foot Low-Speed Wind Tunnel to explore stability and control characteristics of each configuration. A 1/5-scale AVTEK model and a 1/6-scale DeVore model were tested over an angle-of-attack range of up to 45 deg and an angle-of-sideslip range of up to 20 deg. Results from the AVTEK test are presented with an emphasis on the effects of configuration on the stall and poststall characteristics. Results from the DeVore test are presented with emphasis on the effects of wing leading-edge droop design on spin resistance characteristics.

Yip, L. P.↗
NASA NTRS1989

Fabrication and evaluation of enhanced diffusion bonded titanium honeycomb core sandwich panels with titanium aluminide face sheets

A joining process was developed for fabricating lightweight, high temperature sandwich panels for aerospace applications using Ti-14Al-21Nb face sheets and Ti-3Al-2.5V honeycomb core. The process, termed Enhanced Diffusion Bonding (EDB), relies on the formation of a eutectic liquid through solid-state diffusion at elevated temperatures and isothermal solidification to produce joints in thin-gage titanium and titanium aluminide structural components. A technique employing a maskant on the honeycomb core was developed which permitted electroplating a controlled amount of EDB material only on the edges of the honeycomb core in order to minimize the structural weight and metallurgical interaction effects. Metallurgical analyses were conducted to determine the interaction effects between the EDB materials and the constituents of the sandwich structure following EDB processing. The initial mechanical evaluation was conducted with butt joint specimens tested at temperatures from 1400 - 1700 F. Further mechanical evaluation was conducted with EDB sandwich specimens using flatwise tension tests at temperatures from 70 - 1100 F and edgewise compression tests at ambient temperature.

Hoffmann, E. K.↗
NASA NTRS1990

Vibrational testing of optical fiber connector joints

An experimental study was performed to determine the effects of vibration on the propagation of light through SMA- and ST-type fiber-optic connectors. A multimode, fiber-optic link was vibrated from 0 to 10,000 Hz at a constant peak acceleration along the connector transverse and longitudinal axes. All other environmental parameters were ambient. Transfer characteristics through the connection were examined as a function of vibrational frequency using both laser and light-emitting diode (LED) light to illuminate the system. Slight differences in operation between the SMA and ST connectors were observed with no appreciative attenuation as a result of vibration. Vibration did cause the constant-amplitude input light to be modulated in the connector; however, the amplitude of vibration-induced noise was less than 3 standard deviations from the mean.

Sovie, Amy L.↗
NASA NTRS1990

Vibrational testing of optical fiber connector joints

An experimental study was performed to determine the effects of vibration on the propagation of light through SMA- and ST-type fiber-optic connectors. A multimode, fiber-optic link was vibrated from 0 to 10,000 Hz at a constant peak acceleration along the connector transverse and longitudinal axes. All other environmental parameters were ambient. Transfer characteristics through the connection were examined as a function of vibrational frequency using both laser and light-emitting diode (LED) light to illuminate the system. Slight differences in operation between the SMA and ST connectors were observed with no appreciative attenuation as a result of vibration. Vibration did cause constant-amplitude input light to be modulated in the connector; however; the amplitude of vibration-induced noise was less than 3 standard deviations from the mean.

Sovie, Amy L.↗
NASA NTRS1993

Differential GPS for air transport: Status

The presentation presents background on what the Global Navigation Satellite System (GNSS) is, desired target dates for initial GNSS capabilities for aircraft operations, and a description of differential GPS (Global Positioning System). The presentation also presents an overview of joint flight tests conducted by LaRC and Honeywell on an integrated differential GPS/inertial reference unit (IRU) navigation system. The overview describes the system tested and the results of the flight tests. The last item presented is an overview of a current grant with Ohio University from LaRC which has the goal of developing a precision DGPS navigation system based on interferometry techniques. The fundamentals of GPS interferometry are presented and its application to determine attitude and heading and precision positioning are shown. The presentation concludes with the current status of the grant.

Hueschen, Richard M.↗
NASA NTRS1994

Test Plan. GCPS Task 4, subtask 4.2 thrust structure development

The Single Stage To Orbit (SSTO) vehicle is designed to lift off from a vertical position, go into orbit, return to earth for a horizontal landing, and be reusable for the next mission. (NASA baseline only) In order to meet its performance goals, the SSTO relies on light weight structure and the use of 8 tri-propellant engines. These engines are mounted to the thrust structure. This test plan addresses selection of the material for this structure, and the integrity of the design through testing of elements and a full-scale subcomponent. This test plan supports the development of the design for an advanced composite thrust structure for a Single Stage to Orbit manned, heavy launch vehicle. The thrust structure is designed to transmit very high thrust loads from the engines to the rest of the vehicle (see Figure 1 ). The thrust structure will also be used for primary attachment of the twin vertical tails and possibly act as the aft attach point for the wing. The combination of high loading, high vibration, long service life and high acoustic environments will need to be evaluated by tests. To minimize design risk, a building block approach will be used. We will first screen materials to determine which materials show the most promise for this application. Factors in this screening will be the suitability of these materials for chosen design concepts, particularly concerning specific strength, environmental compatibility and applicability to fabrication processes. Next we will characterize two material systems that will be used in the design; the characterization will allow us to generate preliminary design data that will be used for the analysis. Element testing will be performed to evaluate critical structural locations under load. Final testing on the full scale test article will be performed to verify the design and to demonstrate predictability of the analysis. Additionally, risks associated with fabricating full scale thrust structures will be reduced through testing activities. One of the major concerns that stems from full scale fabrication is the realities of size and the associated complexities of handling, manufacturing, and assembly. The need exists to fabricate, assemble and test_representative joint specimens to achieve_confidence in the design and manufacturing technologies being proposed.

Greenberg, H. S.↗
NASA NTRS1997

The Effects of Linear Microphone Array Changes on Computed Sound Exposure Level Footprints

Airport land planning commissions often are faced with determining how much area around an airport is affected by the sound exposure levels (SELS) associated with helicopter operations. This paper presents a study of the effects changing the size and composition of a microphone array has on the computed SEL contour (ground footprint) areas used by such commissions. Descent flight acoustic data measured by a fifteen microphone array were reprocessed for five different combinations of microphones within this array. This resulted in data for six different arrays for which SEL contours were computed. The fifteen microphone array was defined as the 'baseline' array since it contained the greatest amount of data. The computations used a newly developed technique, the Acoustic Re-propagation Technique (ART), which uses parts of the NASA noise prediction program ROTONET. After the areas of the SEL contours were calculated the differences between the areas were determined. The area differences for the six arrays are presented that show a five and a three microphone array (with spacing typical of that required by the FAA FAR Part 36 noise certification procedure) compare well with the fifteen microphone array. All data were obtained from a database resulting from a joint project conducted by NASA and U.S. Army researchers at Langley and Ames Research Centers. A brief description of the joint project test design, microphone array set-up, and data reduction methodology associated with the database are discussed.

Mueller, Arnold W.↗
NASA NTRS1998

XV-15 Tiltrotor Low Noise Terminal Area Operations

Acoustic data have been acquired for the XV-15 tiltrotor aircraft performing a variety of terminal area operating procedures. This joint NASA/Bell/Army test program was conducted in two phases. During Phase 1 the XV-15 was flown over a linear array of microphones, deployed perpendicular to the flight path, at a number of fixed operating conditions. This documented the relative noise differences between the various conditions. During Phase 2 the microphone array was deployed over a large area to directly measure the noise footprint produced during realistic approach and departure procedures. The XV-15 flew approach profiles that culminated in IGE hover over a landing pad, then takeoffs from the hover condition back out over the microphone array. Results from Phase 1 identify noise differences between selected operating conditions, while those from Phase 2 identify differences in noise footprints between takeoff and approach conditions and changes in noise footprint due to variation in approach procedures.

Conner, David A.↗
NASA NTRS2002

Operation of a Thin-Film Inflatable Concentrator System Demonstrated in a Solar Thermal Vacuum Environment

Thin-film inflatable solar concentrators offer significant advantages in comparison to stateof- the-art rigid panel concentrators, including low weight, low stowage volume, and simple gas deployment. From June 10 to 22, 2001, the ElectroMagnetic Radiation Control Experiment (EMRCE) Team used simulated solar energy to demonstrate the operation of an inflatable concentrator system at NASA Glenn Research Center's Tank 6 thermal vacuum facility. The joint Government/industry test team was composed of engineers and technicians from Glenn, the Air Force Research Laboratory, SRS Technologies, and ATK Thiokol Propulsion. The research hardware consisted of the following: 1) A thin-film inflatable concentrator; 2) The hexapod pointing and focus control system; 3) Two rigidized support struts using two candidate technologies - ultraviolet-rigidized glass and radiation-cured isographite.

Wong, Wayne A.↗
NASA NTRS2005

Fabrication of Titanium Bonded Joint Specimens for High Temperature Testing

Four sets of adhesively bonded, titanium lap-shear coupon specimens were fabricated for ultimate strength testing according to the ASTM D1002 and D3165 standards. Important features of the fabrication methods, processing details, and lap-shear test results are presented for specimens fabricated using a modified bismaleimide adhesive, EA 9673, on titanium. Surface treatment of the titanium was performed using surface abrasion followed by one of two separate chemical etching processes. Although cure cycle requirements are different among most adhesives, a single surface preparation method was sought as the preferred method for conditioning the titanium specimens prior to bonding and curing. A fabrication process using a combination of low-pressure grit-blasting of the titanium surface followed by anodization with a sodium hydroxide solution applied to the D1002 specimen geometry provided the highest lapshear strengths in the study. Additionally, difficulties documented during the fabrication process of the D3165 specimens along with features of the D3165 geometry were identified as factors that contributed to lower lap-shear strength results for the D3165 specimens as compared to the results for the D1002 specimens.

Smeltzer, Stanley S., III↗
NASA NTRS1977

Sports and Recreation

Among a number of solar energy tests being jointly conducted by NASA's Lewis Research Center and the Energy Research and Development Administration are a sun-powered refrigerator and a back-pack mounted power supply for radios. Both use solar cells, spacecraft power sources which convert sun energy into electricity. The refrigerator, which has potential utility for outdoor campers, is in operation at a trail construction camp in Isle Royale National Park, a remote wilderness in Michigan's Lake Superior where electricity is available only at park headquarters. Trail maintenance crews working in the back country get food supplies only once weekly; with refrigeration they can enjoy a more varied and nutritious diet. Solar cells provide power to run the refrigerator and to charge its batteries for an alternate power supply when sun is not available. At the request of Znyo National Forest personnel NASA-Lewis also developed a back-pack system. The lightweight solar cell pack (on the pack strap in photo) charges batteries for portable two-way radios used by trailguards, who are on patrol for as much as two weeks at a time. Guards want continuous communication with the District Station, but battery capacity precludes such operation. With the solar cell power supply, guards can use their radios 24 hours a day.A lightweight, higher-capacity oxygen bottle-derived from rocket propellant tank technology-proved an important aid in the 1976 ascent to the summit of Mt. Everest by members of the. American Bicentennial Everest Expedition.

Source record↗
NASA NTRS2008

The Mars Climate Sounder In-Flight Positioning Anomaly

The paper discusses the Mars Climate Sounder (MCS) instrument s in-flight positioning errors and presents background material about it. A short overview of the instrument s science objectives and data acquisition techniques is provided. The brief mechanical description familiarizes the reader with the MCS instrument. Several key items of the flight qualification program, which had a rigorous joint drive test program but some limitations in overall system testing, are discussed. Implications this might have had for the flight anomaly, which began after several months of flawless space operation, are mentioned. The detection, interpretation, and instrument response to the errors is discussed. The anomaly prompted engineering reviews, renewed ground, and some in-flight testing. A summary of these events, including a timeline, is included. Several items of concern were uncovered during the anomaly investigation, the root cause, however, was never found. The instrument is now used with two operational constraints that work around the anomaly. It continues science gathering at an only slightly diminished pace that will yield approximately 90% of the originally intended science.

Jau, Bruno M.↗