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At least 361 records · Page 20

All sources NASA NTRS DOE OSTI

NASA NTRS1991

Toughening of PMR composites by semi-interpenetrating networks

Polymerization of monomer reactants (PMR-15) type polyimide and RP46 prepregs were drum wound using IM-7 fibers. Prepregging and processing conditions were optimized to yield good quality laminates with fiber volume fractions of 60 percent (+/- 2 percent). Samples were fabricated and tested to determine comprehensive engineering properties of both systems. These included 0 deg flexure, short beam shear, transverse flexure and tension, 0 deg tension and compression, intralaminar shear, short block compression, mode 1 and 2 fracture toughness, and compression after impact properties. Semi-2-IPN (interpenetrating polymer networks) toughened PMR-15 and RP46 laminates were also fabricated and tested for the same properties.

Tiwari, S. N.↗

NASA NTRS1991

Arcsecond grating drive mechanism for operation at 4 K

A grating drive mechanism that achieves arcsecond positional control at both room temperature and 4 K is described. The mechanism accommodates eight equally spaced facets on a 360-deg drum, with each facet having arcsecond control over an angular range of +/-3 deg. The cryogenic portion consists of dry lubricated angular contact bearings, a dc brushless torque motor, and a compact magnetic position sensor capable of less than 1 arcsec rms resolution. Test results demonstrate angular repeatability of less than 2 arcsec rms at 4 K and static power dissipation to the helium bath of less than 100 microW.

Downey, C. H.↗

NASA NTRS1991

Reduced energy intake and moderate exercise reduce mammary tumor incidence in virgin female BALB/c mice treated with 7,12-dimethylbenz(a)anthracene

The concurrent effects of diet (standard AIN-76A, restricted AIN-76A and high-fat diet) and moderate rotating-drum treadmill exercise on the incidence of 7,12-dimethylbenz(a)anthracene-induced mammary carcinomas in virgin female BALB/cMed mice free of murine mammary tumor virus are evaluated. Analyses show that, although energy intake was related to mammary tumor incidence, neither body weight nor dietary fat predicted tumor incidence.

Lane, Helen W.↗

NASA NTRS1992

A baseline lunar mine

A models lunar mining method is proposed that illustrates the problems to be expected in lunar mining and how they might be solved. While the method is quite feasible, it is, more importantly, a useful baseline system against which to test other, possible better, methods. Our study group proposed the slusher to stimulate discussion of how a lunar mining operation might be successfully accomplished. Critics of the slusher system were invited to propose better methods. The group noted that while nonterrestrial mining has been a vital part of past space manufacturing proposals, no one has proposed a lunar mining system in any real detail. The group considered it essential that the design of actual, workable, and specific lunar mining methods begin immediately. Based on an earlier proposal, the method is a three-drum slusher, also known as a cable-operated drag scraper. Its terrestrial application is quite limited, as it is relatively inefficient and inflexible. The method usually finds use in underwater mining from the shore and in moving small amounts of ore underground. When lunar mining scales up, the lunarized slusher will be replaced by more efficient, high-volume methods. Other aspects of lunar mining are discussed.

Gertsch, Richard E.↗

NASA NTRS1992

Environmental projects. Volume 14: Removal of contaminated soil and debris

Numerous diverse activities at the Goldstone Deep Space Communications Complex (GDSCC) are carried out in support of six parabolic dish antennas. Some of these activities can result in possible spills or leakages of hazardous materials and wastes stored both above ground in steel drums and below ground in underground storage tanks (UST's). These possible leaks or spills, along with the past practice of burial of solid debris and waste in trenches and pits, could cause local subsurface contamination of the soil. In 1987, the Jet Propulsion Laboratory (JPL), retained Engineering-Science, Inc. (E-S), Pasadena, California, to identify the specific local areas within the GDSCC with subsurface soil contamination. The E-S study determined that some of the soils at the Apollo Site and the Mars Site were contaminated with hydrocarbons, while soil at a nonhazardous waste dumpsite at the Mojave Base site was contaminated with copper. This volume is a JPL-expanded version of the PE209 E-S report, and it also reports that all subsurface contaminated soils at the GDSCC were excavated, removed, and disposed of in an environmentally acceptable way, and the excavations were backfilled and covered in accordance with accepted Federal, State, and local environmental rules and regulations.

Kushner, Len↗

NASA NTRS1920

The Photographic Recording of Small Motions

Methods and equipment for recording small and sometimes rapid motions by photographic means are described, and the efficacy of photographic recording in such instances is evaluated. The optical system consisting of the light source, the mirror or prism for transmitting motion to the emergent beam, and a means of bringing the rays into focus on the film are discussed. Attention is given to the critical issue of mirror mounting. The film holder and the driving motor for the recording drum are described in detail. The authors conclude that the optical methods they describe are far more satisfactory than the recording pen, in compactness, in high natural period, and in elimination of friction. Costs are similar to mechanical methods. The development and reproduction of the record is an added complication, but the ease of duplicating the records is a decided advantage.

Norton, F H↗

NASA NTRS1922

N.A.C.A. Control Position Recorder

A new instrument is described which is capable of simultaneously recording the position of the three controls of an airplane. The records are taken photographically on a standard N.A.C.A. film drum and the instrument can be quickly installed in any airplane.

Norton, F H↗

NASA NTRS1923

An Impulse Electric Motor for Driving Recording Instruments

The chief purpose in undertaking the development of this synchronous motor was the creation of a very small, compact power source, capable of driving the film drums of the recording aircraft instruments designed by the staff of the National Advisory Committee for Aeronautics.

Joachim, W F↗

NASA NTRS1919

Airplane dopes and doping

Cellulose acetate and cellulose nitrate are the important constituents of airplane dopes in use at the present time, but planes were treated with other materials in the experimental stages of flying. The above compounds belong to the class of colloids and are of value because they produce a shrinking action on the fabric when drying out of solution, rendering it drum tight. Other colloids possessing the same property have been proposed and tried. In the first stages of the development of dope, however, shrinkage was not considered. The fabric was treated merely to render it waterproof. The first airplanes constructed were covered with cotton fabric stretched as tightly as possible over the winds, fuselage, etc., and flying was possible only in fine weather. The necessity of an airplane which would fly under all weather conditions at once became apparent. Then followed experiments with rubberized fabrics, fabrics treated with glue rendered insoluble by formaldehyde or bichromate, fabrics treated with drying and nondrying oils, shellac, casein, etc. It was found that fabrics treated as above lost their tension in damp weather, and the oil from the motor penetrated the proofing material and weakened the fabric. For the most part the film of material lacked durability. Cellulose nitrate lacquers, however were found to be more satisfactory under varying weather conditions, added less weight to the planes, and were easily applied. On the other hand, they were highly inflammable, and oil from the motor penetrated the film of cellulose nitrate, causing the tension of the fabric to be relaxed.

PROTECTIVE COATINGS AND COVERINGS↗

NASA NTRS1932

Dynamic testing of airplane shock-absorbing struts

Measurement of perpendicular impacts of a landing gear with different shock-absorbing struts against the drum testing stand. Tests were made with pneumatic shock absorbers having various degrees of damping, liquid shock absorbers, steel-spring shock absorbers and rigid struts. Falling tests and rolling tests. Maximum impact and gradual reduction of the impacts in number and time in the falling tests. Maximum impact and number of weaker impacts in rolling tests.

Langer, P↗

NASA NTRS1994

The effect of inlet swirl on the dynamics of long annular seals in centrifugal pumps

This paper describes additional results from a continuing research program which aims to identify the dynamics of long annular seals in centrifugal pumps. A seal test rig designed at Heriot-Watt University and commissioned at Weir Pumps Research Laboratory in Alloa permits the identification of mass, stiffness, and damping coefficients using a least-squares technique based on the singular value decomposition method. The analysis is carried out in the time domain using a multi-fiequency forcing function. The experimental method relies on the forced excitation of a flexibly supported stator by two hydraulic shakers. Running through the stator embodying two symmetrical balance drum seals is a rigid rotor supported in rolling element bearings. The only physical connection between shaft and stator is the pair of annular gaps filled with pressurized water discharged axially. The experimental coefficients obtained from the tests are compared with theoretical values.

Ismail, M.↗

NASA NTRS1994

Whirl measurements on leakage flows in turbomachine models

The beneficial effects claimed for whirl control devices demonstrate that the dynamic behavior of rotors is influenced by the fluid whirl in shaft and balance drum seals. The present paper reports results from two series of experiments, the first on the factors affecting the whirl at the seal inlet, and the second on the variation of whirl velocity along the seal. In both cases the LDA measurement technique required the clearance between the fixed and rotating parts of the models to be substantially greater than occurs in real machines, but the results are indicative nevertheless. Experimental and theoretical results are given for the radial distribution of whirl velocity in the gap between impeller shroud and pump casing. Results of tests with modified stator surfaces are also shown. This work leads naturally into the second series of experiments where some preliminary measurements of velocity distribution in the clearance between a fixed stator and a rotating shaft are reported for a range of inlet whirl conditions.

Addlesee, A. J.↗

NASA NTRS1993

Chinese hyper-susceptibility to vection-induced motion sickness

Little is known about the factors that control individual differences in susceptible to motion sickness. A serendipitous observation in our laboratory that most Chinese subjects become motion sick prompted this study. We used a rotating optokinetic drum to provoke motion sickness and compared gastric responses and symptom reports of Chinese, European-American, and African-American subjects. There was no difference in the responses of European-American and African-American subjects; however, Chinese subjects showed significantly greater disturbances in gastric activity and reported significantly more severe symptoms. We suggest that this hypersusceptibility presents a natural model for the study of physiological mechanisms of nausea and other symptoms of motion sickness.

Stern, Robert M.↗

NASA NTRS1993

AVIRIS and TIMS data processing and distribution at the land processes distributed active archive center

The U.S. Government has initiated the Global Change Research program, a systematic study of the Earth as a complete system. NASA's contribution of the Global Change Research Program is the Earth Observing System (EOS), a series of orbital sensor platforms and an associated data processing and distribution system. The EOS Data and Information System (EOSDIS) is the archiving, production, and distribution system for data collected by the EOS space segment and uses a multilayer architecture for processing, archiving, and distributing EOS data. The first layer consists of the spacecraft ground stations and processing facilities that receive the raw data from the orbiting platforms and then separate the data by individual sensors. The second layer consists of Distributed Active Archive Centers (DAAC) that process, distribute, and archive the sensor data. The third layer consists of a user science processing network. The EOSDIS is being developed in a phased implementation. The initial phase, Version 0, is a prototype of the operational system. Version 0 activities are based upon existing systems and are designed to provide an EOSDIS-like capability for information management and distribution. An important science support task is the creation of simulated data sets for EOS instruments from precursor aircraft or satellite data. The Land Processes DAAC, at the EROS Data Center (EDC), is responsible for archiving and processing EOS precursor data from airborne instruments such as the Thermal Infrared Multispectral Scanner (TIMS), the Thematic Mapper Simulator (TMS), and Airborne Visible and Infrared Imaging Spectrometer (AVIRIS). AVIRIS, TIMS, and TMS are flown by the NASA-Ames Research Center ARC) on an ER-2. The ER-2 flies at 65000 feet and can carry up to three sensors simultaneously. Most jointly collected data sets are somewhat boresighted and roughly registered. The instrument data are being used to construct data sets that simulate the spectral and spatial characteristics of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument scheduled to be flown on the first EOS-AM spacecraft. The ASTER is designed to acquire 14 channels of land science data in the visible and near-IR (VNIR), shortwave-IR (SWIR), and thermal-IR (TIR) regions from 0.52 micron to 11.65 micron at high spatial resolutions of 15 m to 90 m. Stereo data will also be acquired in the VNIR region in a single band. The AVIRIS and TMS cover the ASTER VNIR and SWIR bands, and the TIMS covers the TIR bands. Simulated ASTER data sets have been generated over Death Valley, California, Cuprite, Nevada, and the Drum Mountains, Utah using a combination of AVIRIS, TIMS, amd TMS data, and existing digital elevation models (DEM) for the topographic information.

Mah, G. R.↗

NASA NTRS1995

On the application of Chimera/unstructured hybrid grids for conjugate heat transfer

A hybrid grid system that combines the Chimera overset grid scheme and an unstructured grid method is developed to study fluid flow and heat transfer problems. With the proposed method, the solid structural region, in which only the heat conduction is considered, can be easily represented using an unstructured grid method. As for the fluid flow region external to the solid material, the Chimera overset grid scheme has been shown to be very flexible and efficient in resolving complex configurations. The numerical analyses require the flow field solution and material thermal response to be obtained simultaneously. A continuous transfer of temperature and heat flux is specified at the interface, which connects the solid structure and the fluid flow as an integral system. Numerical results are compared with analytical and experimental data for a flat plate and a C3X cooled turbine cascade. A simplified drum-disk system is also simulated to show the effectiveness of this hybrid grid system.

Kao, Kai-Hsiung↗

NASA NTRS1977

Research on Graphite Reinforced Glass Matrix Composites

This report contains the results obtained in the first twelve months of research under NASA Langley Contract NAS1-14346 for the origination of graphite-fiber reinforced glass matrix composites. Included in the report is a summary of the research by other investigators in this area. The method selected to form the composites consisted of pulling the graphite fiber through a slurry containing powdered glass, winding up the graphite fiber and the glass it picks up on a drum, drying, cutting into segments, loading the tape segment into a graphite die, and hot pressing. During the course of the work, composites were made with a variety of graphite fibers in a C.G.W. 7740 (Pyrex) glass matrix. The graphite fibers used included Hercules HMS, Hercules HTS, Thornel 300S, and Celanese DG-102 and, of these, the Hercules HMS and Celanese DG-102 graphite fibers in C.G.W. 7740 gave the most interesting but widely different results. Hercules HMS fiber in C.G.W. 7740 glass (Pyrex) showed an average four-point flexural strength of 848 MPa or 127,300 psi. As the test temperature was raised from room temperature to 560 C in argon or vacuum, the strength was higher by 50 percent. However, in air, similar tests at 560 C gave a severe loss in strength. These composites also have good thermal cycle properties in argon or vacuum, greatly increased toughness compared to glass, and no loss in strength in a 100 cycle fatigue test. Celanese DG-102 fiber in C.G.W. 7740 glass (Pyrex) had a much lower flexural strength but did not suffer any loss in this strength when samples were heated to 560 C in air for 4 hrs.

Bacon, J. F.↗

NASA NTRS1996

Advances in the analysis and design of constant-torque springs

In order to improve the design procedure of constant-torque springs used in aerospace applications, several new analysis techniques have been developed. These techniques make it possible to accurately construct a torque-rotation curve for any general constant-torque spring configuration. These new techniques allow for friction in the system to be included in the analysis, an area of analysis that has heretofore been unexplored. The new analysis techniques also include solutions for the deflected shape of the spring as well as solutions for drum and roller support reaction forces. A design procedure incorporating these new capabilities is presented.

McGuire, John R.↗

NASA NTRS1997

Strong and Tough Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites

Strong, tough and almost fully dense Hi-Nicalon/BN/SiC fiber reinforced celsian matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, stacking the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from a mixed oxide precursor. The unidirectional composites having approx. 42 volume percent of fibers exhibited graceful failure with extensive fiber pullout in three-point bend tests at room temperature. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01 %, respectively, and ultimate strengths of 900 +/- 60 MPa were observed. The Young's modulus of the composites was 165 +/- 5 GPa.

Bansal, Narottam P.↗