SEARCH · Engineering Papers

Results for “lack”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40

All sources NASA NTRS DOE OSTI

NASA NTRS1976

Irradiate-anneal screening of total dose effects in semiconductor devices

An extensive investigation of irradiate-anneal (IRAN) screening against total dose radiation effects was carried out as part of a program to harden the Mariner Jupiter/Saturn 1977 (MJS'77) spacecraft to survive the Jupiter radiation belts. The method consists of irradiating semiconductor devices with Cobalt-60 to a suitable total dose under representative bias conditions and of separating the parts in the undesired tail of the distribution from the bulk of the parts by means of a predetermined acceptance limit. The acceptable devices are then restored close to their preirradiation condition by annealing them at an elevated temperature. IRAN was used when lot screen methods were impracticable due to lack of time, and when members of a lot showed a diversity of radiation response. The feasibility of the technique was determined by testing of a number of types of linear bipolar integrated circuits, analog switches, n-channel JFETS and bipolar transistors. Based on the results of these experiments a number of device types were selected for IRAN of flight parts in the MJS'77 spacecraft systems. The part types, screening doses, acceptance criteria, number of parts tested and rejected as well as the program steps are detailed.

Stanley, A. G.↗

NASA NTRS1976

Assurance of lubricant supply in wet-lubricated space bearings

Conventional lubrication techniques appear to be satisfactory, but rigorous proof of meeting a ten-year life requirement is lacking. One approach provides additional lubricant only when commanded from ground control, while the other passively augments lubrication at all times. Each technique has specific advantages, and selection should be related to the application to obtain optimum performance.

Glassow, F. A.↗

NASA NTRS1975

Summary of space imagery studies in Utah and Nevada

The author has identified the following significant results. An enhanced enlargement of a S190B color image at a scale of 1/19,200 of the Bingham porphyry copper deposit has compared a geological map of the area with the space imagery map as fair for the intrusion boundaries and total lack of quality for mapping the sediments. Hydrothermal alteration is only slightly evident on space imagery at Bingham, but in the Tintic mining district and the volcanic piles of the Keg and Thomas ranges, Utah, hydrothermal alteration is readily mapped on color enlargements of S190B. Several sites of calderas were recognized and new ones located on space imagery. One of the tools developed is a mercury soil-gas analyzer that is becoming significant as an aid in locating hidden mineralized zones which were suggested from space imagery. In addition, this tool is a prime aid in locating and better delineating geothermal sites.

Jensen, M. L.↗

NASA NTRS1976

Heat shield characterization: Outer planet atmospheric entry probe

A full scale carbon phenolic heat shield was fabricated for the Outer Planet Probe in order to demonstrate the feasibility of molding large carbon phenolic parts with a new fabrication processing method (multistep). The sphere-cone heat shield was molded as an integral unit with the nose cap plies configured into a double inverse chevron shape to achieve the desired ply orientation. The fabrication activity was successful and the feasibility of the multistep processing technology was established. Delaminations or unbonded plies were visible on the heat shield and resulted from excessive loss of resin and lack of sufficient pressure applied on the part during the curing cycle. A comprehensive heat shield characterization test program was conducted, including: nondestructive tests with the full scale heat shield and thermal and mechanical property tests with small test specimen.

Mezines, S. A.↗

NASA NTRS1976

Remote probing of atmospheric particulates from radiation extinction experiments: A review of methods

The existing methodology for reconstructing the particle size distribution and inferring the refractive index of absorbing and scattering atmospheric particulates is critically reviewed. Emphasis is placed on method capabilities and shortcomings and, wherever possible, on achievable accuracy. The nature of the associated remote probing problem is analyzed with regard to the effects of the particulates on EM wave propagation in the atmosphere. The parameterization of size distribution is studied within the unifying framework of Pearson's distribution curves. The inversions of extinction measurements and their ratios are considered separately, and the potentialities of each type of measurement are identified. Work lacking in each of the methods reviewed is indicated. A method of determining both the effective complex refractive index and size distribution model parameters from the same data is also presented. Lastly, determination from extinction ratio data of the complex refractive index independent of size distribution is discussed and error analyzed.

Fymat, A. L.↗

NASA NTRS1976

Mini-O, simple Omega receiver hardware for user education

A problem with the Omega system is a lack of suitable low cost hardware for the small user community. A collection of do it yourself circuit modules are under development intended for use by educational institutions, small boat owners, aviation enthusiasts, and others who have some skills in fabricating their own electronic equipment. Applications of the hardware to time frequency standards measurements, signal propagation monitoring, and navigation experiments are presented. A family of Mini-O systems have been constructed varying from the simplest RF preamplifiers and narrowband filters front-ends, to sophisticated microcomputer interface adapters.

Burhans, R. W.↗

NASA NTRS1976

Permittivity of water at millimeter wave-lengths

Work performed on the permittivity of seawater and ice at 100 GHz was described. Measurements on water covered the temperature range from 0 to 50 C, while the measurements on ice were taken near - 10 C. In addition, a small number of measurements were made on the reflectivity of absorber materials used in a previous program on research in millimeter wave techniques. Normal incidence reflectivity was measured, and the result was used to obtain the index of refraction. For the case of normal incidence, reflectivity at a fixed temperature was reproducible to 1% for values near 40%. For reflectivity measurements on ice, the lack of attenuation leads to reflection from the back surface of the sample; this complication was circumvented by using a wedge shaped sample and freezing the water in a container lined with absorber material.

Blue, M. D.↗

NASA NTRS1976

Active control technology and the use of multiple control surfaces

Needed criteria for active control technology applications in commercial transports are lacking. Criteria for redundancy requirements, believed to be consistent with certification philosophy, are postulated to afford a discussion of the relative value of multiple control surfaces. The control power and frequency bandpass requirements of various active control technology applications are shown to be such that multiple control surfaces offer advantages in minimizing the hydraulic or auxiliary power for the control surface actuators.

Hart, J. E.↗

NASA NTRS1976

A low-frequency radio survey of the planets with RAE-2

Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer-2 (RAE-2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025 to 13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE-2.

Kaiser, M. L.↗

NASA NTRS1975

The theory of Enceladus and Dione - An application of computerized algebra in dynamical astronomy

The orbits of the satellites of the outer planets are poorly known, due to lack of attention over the past half century. We have been developing a new theory of Saturn's satellites Enceladus and Dione which is literal (all constants of integration appear explicitly), canonically invariant (the Hori-Lie method is used), and which correctly handles the eccentricity-type resonance between the two satellites. The algebraic manipulations are being performed using the TRIGMAN formula manipulation language, and the programs have been developed so that with minor modifications they can be used on the Mimas-Tethys and Titan-Hyperion systems.

Jefferys, W. H.↗

NASA NTRS1976

Coordinated ATS 5 electron flux and simultaneous auroral observations

An attempt is made to correlate ATS 5 plasma data with all-sky photographic data taken at Thompson and Gillam, Manitoba. The fields of view of the Canadian stations cover the projected field line position of the satellite. Trapped electron fluxes at the satellite and the simultaneously measured auroral activity near the projected foot of the satellite field line were compared for several days of varying substorm activity with all-sky camera data, which was in the form of time-varying luminosity plots. The observed auroral intensification coincident with plasma injection shows that on a broad scale the auroras are correlated well with the magnetospheric trapped plasma; however, there is a lack of detailed correlation between the fine structure of the trapped plasma fluxes and the small scale auroral features.

Mende, S. B.↗

NASA NTRS1976

An ultrasoft X-ray source in Coma Berenices

An intense soft X-ray source with an extraordinary spectrum has been observed in Coma Berenices, 4 deg northeast of and not associated with the Coma cluster of galaxies. Two spectra, obtained at different times in a sounding-rocket flight, indicate that the source temperature in thermal models is less than 1 million K; a power-law model requires photon power-law indices steeper than n = -3. The intensity in the 44-165 A band is of the order of 5 by 10 to the -10th power erg/sq cm/sec, but no flux is present at energies 0.3-2.1 keV to a limit of 1 by 10 to the -10th power erg/sq cm/sec. The lack of bright stars or a supernova remnant in the error box implies that this may be a new class of soft X-ray sources.

Margon, B.↗

NASA NTRS1976

New results on the correlation between low-energy electrons and auroral hiss

The results of a VLF (0.3-18 kHz) experiment aboard OGO 4 are compared with simultaneous data obtained by the satellite on precipitating electrons at 0.7, 2.3, and 7.3 keV to determine the source of the auroral hiss band in the night side auroral zone. At these energies the correlation with VLF auroral hiss is best at 0.7 keV and worst at 7.3 keV. Auroral electrons in the keV range may enhance the intensity of VLF auroral hiss on the night side, but the predominant source of night side hiss appears to be electrons of energies below 0.7 keV. Auroral hiss tends to occur simultaneously over a broad range of frequencies. A study based on OGO 6 data has revealed a lack of correlation between keV electrons and LF auroral hiss. These observations suggest that hiss of all frequencies is generated by electrons with energies below about 1 keV. The excellent correlation between auroral hiss and 0.7 keV electrons in the day time cleft is apparently maintained when the region of very soft electron precipitation is in motion.

Laaspere, T.↗

NASA NTRS1976

The meteorology of Jupiter

From the point of view of meteorology the most important differences between Jupiter and the earth are related to the fact that Jupiter has an appreciable internal energy source and probably lacks a solid surface. The composition and vertical structure of the Jovian atmosphere is considered along with the composition of Jovian cloud particles, turbulence in Jupiter's atmosphere, data on the horizontal structure and motions of the atmosphere, and questions related to the longevity of Jupiter's clouds. Attention is given to the barotropic characteristics of Jupiter's atmosphere, the radiation balance in the atmosphere of the earth and of Jupiter, and studies of the Great Red Spot.

Ingersoll, A. P.↗

NASA NTRS1976

Advanced composites - An assessment of the future

An assessment concerning the possibilities of a use of advanced composites in aerospace and space technology identified a lack of confidence and high cost as the major factors inhibiting composite applications. Attention is given to the present employment of composites and plans for its future use in the Army, Navy, and Air Force. Various programs conducted by NASA are concerned with the development of a technological base for the extended use of advanced composites in aerospace and space applications. A future commercial transport is considered in which virtually the entire airframe could be of advanced composites. The attitude of aircraft manufacturers, engine manufacturers, airlines, spacecraft users, and material suppliers with regard to an employment of composites is also examined.

Harris, L. A.↗

NASA NTRS1976

Modulation of auroral electron fluxes in the frequency range 50 kHz to 10 MHz

A sounding rocket-borne electron detector of high time resolution is used to search for modulation of auroral electron fluxes in the frequency range 50 kHz to 10 MHz and energy range 5-7 keV. Data were telemetered to ground via a 93-kHz subcarrier. A cross-correlation analysis of the data collected indicates low-level modulation near the detection threshold of the instrument. Two U-1 events are observed which are interpreted as indications of modulation. The two modulation events occur during a period of increasing flux for a region marking the boundary between two current sheets detected by the payload magnetometer. The strongest argument against interference contamination is the lack of any observable modulation at times other than those mentioned in the study.

Spiger, R. J.↗

NASA NTRS1975

Geomorphic interpretation of Skylab photography collected over the Nevada portion of the Great Basin

Skylab S190B black and white photography has a useful reconnaissance capability in geomorphic mapping of landform features in the arid and semi-arid Great Basin. Enlargement of original photographic data products to a scale of 1:250,000 scale compatible with published topographic maps permits ready identification and classification of most landform elements. However, interpretation suffers through the lack of stereoscopic coverage and introduces problems relating to scale and loss of detail. When aircraft underflight photography for the same area is used as a data enhancement tool, problems of scale, detail, and interpretation are diminished. The combination of orbital and underflight photographic coverage provides a regional overview in which the interrelationships of both micro- and macro-scale landforms become apparent.

Frater, J. B.↗

NASA NTRS1975

The use of hand-held 35 mm color infrared imagery for estimates of suspended solids - A progress report

A cost-effective aerial surveillance technique is proposed for detection and identification of suspended solids which would be operational for both governmental monitoring organizations and private individuals operating catfish farms. Sixteen catfish ponds were flown daily for seven days using two hand-held 35 mm cameras with both Kodachrome X and Ektachrome infrared film. Hue, value, and chroma designations were recorded for each pond on each date by three interpreters, and the accepted color was that recorded by at least two of the interpreters, or if there was a three hue range, the median was accepted. Relations between suspended solids and color designations were analyzed graphically, and chroma was discarded due to an apparent lack of correlation. The data obtained were then analyzed by multiple regression. Significant correlations were revealed between hue and value and total and inorganic suspended solids. If perfected, this technique could be developed to sufficent accuracy for large-scale reconnaissance surveys to monitor the quality of rivers and streams.

Miller, W. F.↗