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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 505 records · Page 28
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NASA NTRS1985

Response of earth and Venus ionospheres to corotating solar wind stream of 3 July 1979

Corotating solar wind stream interactions are examined for the earth and Venus in light of data from the plasma detectors aboard ISEE-3, the Pioneer Venus Orbiter (PVO), and Helios-A, as well as in situ ion composition measurements taken by the mass spectrometers aboard the PVO and Atmosphere Explorer-E spacecraft. During May-July 1979, a sequence of distinct, recurrent coronal regions developed at the sun; their analysis indicates a corresponding sequence of corotating streams. Although the planetary environments are distinctly different, it is noted that pronounced and analogous ionospheric responses to the stream passage were observed at both the earth and Venus. The response to the intercepted stream is consistent with independent investigations showing the importance of the variability of the solar wind momentum flux in the solar wind-ionosphere interaction at both planets.

Taylor, H. A., Jr.↗
NASA NTRS1985

Analysis of Terrestrial Conditions and Dynamics

An ecological model is developed to estimate annual net primary productivity of vegetation in twelve major North American biomes. Three models are adapted and combined, each addressing a different factor known to govern primary productivity, i.e., photosynthesis, respiration, and moisture availability. Measures of intercepted photosynthetically active radiation (1PAR) for input to the photosynthesis model are derived from spectral vegetation index data. Normalized Difference Vegetation Index (NDVI) data are produced from NOAA-7 Advanced Very High Resolution Radiometer (AVHRR) observations for April 1982 through March 1983. NDVI values are sampled from within the biomes at locations for which climatological data are available. Monthly estimates of Net Primary Productivity (NPP) for each sample location are generated and summed over the twelve month period. These monthly estimates are averaged to produce a single annual estimated NPP value for each biomes. Comparison of estimated NPP values with figures reported in the literature produces a correlation coefficient of 85.

Goward, S. N.↗
NASA NTRS1985

An update of the total-strain version of SRP

An updated procedure for characterizing an alloy and predicting cyclic life by using the total strain range version of strainrange partitioning (TS-SRP) has been developed. The principal feature of this update is a new procedure for determining the intercept of time dependent elastic strain range versus cyclic life lines. The procedure is based on an established relation between failure and the cyclic stress-strain response of an alloy. The stress-strain response is characterized by empirical equations presented in this report. These equations were determined with the aid of a cyclic constitutive model. The procedures presented herein reduce the testing required to characterize an alloy. Failure testing is done only in the high strain, low life regime; cyclic stress-strain response is determined from tests conducted in both the high and low strain regimes. These tests are carried out to stability of the stress-strain hysteresis loop but not to failure. Thus both the time and costs required to characterize an alloy are greatly reduced. This approach was evaluated and verified for two nickel base superalloys, AF2-1DA and Inconel 718.

Saltsman, J. F.↗
NASA NTRS1986

Simulation model for plant growth in controlled environment systems

The role of the mathematical model is to relate the individual processes to environmental conditions and the behavior of the whole plant. Using the controlled-environment facilities of the phytotron at North Carolina State University for experimentation at the whole-plant level and methods for handling complex models, researchers developed a plant growth model to describe the relationships between hierarchial levels of the crop production system. The fundamental processes that are considered are: (1) interception of photosynthetically active radiation by leaves, (2) absorption of photosynthetically active radiation, (3) photosynthetic transformation of absorbed radiation into chemical energy of carbon bonding in solube carbohydrates in the leaves, (4) translocation between carbohydrate pools in leaves, stems, and roots, (5) flow of energy from carbohydrate pools for respiration, (6) flow from carbohydrate pools for growth, and (7) aging of tissues. These processes are described at the level of organ structure and of elementary function processes. The driving variables of incident photosynthetically active radiation and ambient temperature as inputs pertain to characterization at the whole-plant level. The output of the model is accumulated dry matter partitioned among leaves, stems, and roots; thus, the elementary processes clearly operate under the constraints of the plant structure which is itself the output of the model.

Raper, C. D., Jr.↗
NASA NTRS1986

A planetary ultra hypervelocity impact mechanics and shock wave science facility

Using the concept of intercepting orbits from a pair of Space Station serviced free flyers, a class of impact and shock wave experiments pertinent to planetary science can be performed. One proposed free flying vehicle is an impactor dispensor, and the second is the impact laboratory. How collision is achieved by utilizing essentially twice orbital velocity is demonstrated. The impactor dispensor contains a series of small flyer plates or other projectiles which are launched into the trajectory of the impactor laboratory at appropriate positions. The impactor laboratory is a large impact tank similar to those in terrestrial gun laboratories, except that it contains a supply of targets and instrumentation such as high speed cameras, flash X-ray apparatus and digital recorders. Shock and isentropic pressures of up to 20 Mbar are achievable with such a system which provides 15 km/sec impact velocities for precisely oriented projectiles.

Ahrens, T. J.↗
NASA NTRS1986

Mass loading of the Earth's magnetosphere by micron size lunar ejecta. 2: Ejecta dynamics and enhanced lifetimes in the Earth's magnetosphere

Extensive studies were conducted concerning the indivdual mass, temporal and positional distribution of micron and submicron lunar ejecta existing in the Earth-Moon gravitational sphere of influence. Initial results show a direct correlation between the position of the Moon, relative to the Earth, and the percentage of lunar ejecta leaving the Moon and intercepting the magnetosphere of the Earth at the magnetopause surface. It is seen that the Lorentz Force dominates all other forces, thus suggesting that submicron dust particles might possibly be magnetically trapped in the well known radiation zones.

Alexander, W. M.↗
NASA NTRS1986

Effect of emerging technology on a convertible, business/interceptor, supersonic-cruise jet

This study was initiated to assess the feasibility of an eight-passenger, supersonic-cruise long range business jet aircraft that could be converted into a military missile carrying interceptor. The baseline passenger version has a flight crew of two with cabin space for four rows of two passenger seats plus baggage and lavatory room in the aft cabin. The ramp weight is 61,600 pounds with an internal fuel capacity of 30,904 pounds. Utilizing an improved version of a current technology low-bypass ratio turbofan engine, range is 3,622 nautical miles at Mach 2.0 cruise and standard day operating conditions. Balanced field takeoff distance is 6,600 feet and landing distance is 5,170 feet at 44,737 pounds. The passenger section from aft of the flight crew station to the aft pressure bulkhead in the cabin was modified for the interceptor version. Bomb bay type doors were added and volume is sufficient for four advanced air-to-air missiles mounted on a rotary launcher. Missile volume was based on a Phoenix type missile with a weight of 910 pounds per missile for a total payload weight of 3,640 pounds. Structural and equipment weights were adjusted and result in a ramp weight of 63,246 pounds with a fuel load of 30,938 pounds. Based on a typical intercept mission flight profile, the resulting radius is 1,609 nautical miles at a cruise Mach number of 2.0.

Beissner, F. L., Jr.↗
NASA NTRS1986

Implementation and flight tests for the Digital Integrated Automatic Landing System (DIALS). Part 1: Flight software equations, flight test description and selected flight test data

Five flight tests of the Digital Automated Landing System (DIALS) were conducted on the Advanced Transport Operating Systems (ATOPS) Transportation Research Vehicle (TSRV) -- a modified Boeing 737 aircraft for advanced controls and displays research. These flight tests were conducted at NASA's Wallops Flight Center using the microwave landing system (MLS) installation on runway 22. This report describes the flight software equations of the DIALS which was designed using modern control theory direct-digital design methods and employed a constant gain Kalman filter. Selected flight test performance data is presented for localizer (runway centerline) capture and track at various intercept angles, for glideslope capture and track of 3, 4.5, and 5 degree glideslopes, for the decrab maneuver, and for the flare maneuver. Data is also presented to illustrate the system performance in the presence of cross, gust, and shear winds. The mean and standard deviation of the peak position errors for localizer capture were, respectively, 24 feet and 26 feet. For mild wind conditions, glideslope and localizer tracking position errors did not exceed, respectively, 5 and 20 feet. For gusty wind conditions (8 to 10 knots), these errors were, respectively, 10 and 30 feet. Ten hands off automatic lands were performed. The standard deviation of the touchdown position and velocity errors from the mean values were, respectively, 244 feet and 0.7 feet/sec.

Hueschen, R. M.↗
NASA NTRS1986

Interplanetary dust: The interstellar connection

Although not proven, there is the widespread belief that comets consist, at least in part, of interstellar material that was originally present in the solar nebula. Furthermore, there are strong arguments in favor of the view that much of the interplanetary dust complex is derived from comets. The main arguments supporting this view are based on mass balance, analysis of the orbital parameters of meteors, and the long known association between meteor showers and specific comets. Laboratory measurements on interplanetary dust particles (IDPs) collected in the stratosphere have confirmed the view that many of the dust particles are primitive in the sense that they show striking enrichments of D/H relative to average solar system materials. It has also been demonstrated that the mid-infrared absorption spectra of one infrared red class of particles show strong similarities to IR sources such as the protostar W-33A. However, the laboratory studies of IDPs have shown that they represent a diverse set of objects and the measurement of the orbital parameters of specific dust particles is essential to answering the question of sources. The observation of the IRAS dust bands reopens the question of the role of asteroids in supplying a significant fraction of the dust and part of the diversity observed may be due to the fact that some of the dust is asteroidal and some cometary. In addition, some fraction of interplanetary dust must consist of an interstellar component intercepted by the solar system in its motion through the local interstellar medium. It has been shown that dust derived from nearby stars will have 75% of their orbits with eccentricities or equal to 1.1 and might be difficult to distinguish from interplanetary dust based on orbital measurements alone.

Carey, W. C.↗
NASA NTRS1986

The Astro-1 mission

The Astro-1 mission was to be launched in March 1986 for an effective duration of 7 days, chosen to overlap spacecraft encounters with Halley's Comet, i.e., Vega-2 (on 9 March) and Giotto (on 13/14 March). The ultraviolet instrument complement while not designed with cometary research as the prime objective, was well suited to the study of comets. The opportunity of an extended mission during the time of the spacecraft encounters of Halley's Comet offered an extraordinary opportunity for a synergistic interaction between the intercept spacecraft, the Earth-orbital Astro-1 mission, and ground-based observations. The addition of visual-wavelength, wide-field cameras would enhance the scientific return of the mission. Loss of Challenger cancelled the mission.

Brandt, J. C.↗
NASA NTRS1984

Space Shuttle night landing

The tracking and guidance requirements of the Indian National Satellite during its transition from the low-earth orbit to geosynchronous orbit dictated a night launch and subsequent night landing. The development of an Orbiter-independent external lighting system (ELS) that would work in conjunction with the Orbiter navigation, guidance, and control systems used for day approach and landing is described. The ELS includes the night landing visual aids; the heading alignment circle precision approach path indicator lights, as an aid for the outer glide slope; the runway floodlight, to accommodate for the transition area between preflare and intercepting inner glide slope (IGS) system; the ball/bar reference IGS system; and heads-up displays. The aspects of the lakebed dust problems are discussed. Diagrams illustrating the approach trajectory, final night-lighting configurations, and the approach and land symbology are included.

Brandenstein, D. C.↗
NASA NTRS1986

On the design of classifiers for crop inventories

Crop proportion estimators that use classifications of satellite data to correct, in an additive way, a given estimate acquired from ground observations are discussed. A linear version of these estimators is optimal, in terms of minimum variance, when the regression of the ground observations onto the satellite observations in linear. When this regression is not linear, but the reverse regression (satellite observations onto ground observations) is linear, the estimator is suboptimal but still has certain appealing variance properties. In this paper expressions are derived for those regressions which relate the intercepts and slopes to conditional classification probabilities. These expressions are then used to discuss the question of classifier designs that can lead to low-variance crop proportion estimates. Variance expressions for these estimates in terms of classifier omission and commission errors are also derived.

Heydorn, R. P.↗
NASA NTRS1986

Contact angle and surface tension measurements of a five-ring polyphenyl ether

Contact angle measurements were performed for a five-ring polyphenyl ether isomeric mixture on M-50 steel in a dry nitrogen atmosphere. Two different techniques were used: (1) a tilting plate apparatus, and (2) a sessile drop apparatus. Measurements were made for the temperature range 25 to 190 C. Surface tension was measured by a differential maximum bubble pressure technique over the range 23 to 220 C in room air. The critical surface energy of spreading (gamma /sub c/) was determined for the polyphenyl ether by plotting the cosine of the contact angle (theta) versus the surface tension (gamma /sub LV/). The straight line intercept at cosine theta = 1 is defined as gamma (sub c). Gamma (sub c) was found to be 30.1 dyn/cm for the tilting plate technique and 31.3 dyn/cm for the sessile drop technique. These results indicate that the polyphenyl ether is inherently autophobic (i.e., it will not spread on its own surface film until its surface tension is less than gamma /sub c/). This phenomenon is discussed in light of the wettability and wear problems encountered with this fluid.

Jones, W. R., Jr.↗
NASA NTRS1985

The International Cometary Explorer mission to comet Giacobini-Zinner

The International Cometary Explorer (ICE), scheduled to pass the tail of Comet Giacobini-Zinner on September 11, 1985, was expected to address first-order questions bout the interaction between solar wind and comets. Since ICE was not initially intended for comet studies, it did not have sun-sensitive imaging instruments designed to image the comet nucleus. In effect, ICE was free to pass through the tail of the comet. The ICE spacecraft, a 16-faceted cylindrical drum just over five ft high with a spin axis normal to the ecliptic plane, was designed to encounter the comet at a distance of 0.47 AU from the earth. Scientific instruments on board the spacecraft include: (1) the electron plasma experiment, (2) the vector helium magnetometer, (3) the plasma wave experiment, (4) the radio waves experiment, (5) the plasma ion experiment, (6) the low-energy cosmic ray experiment, and (7) the energetic protons experiment. Targeting error was expected as a result of solar-wind induced plasma tail wagging. Comet interception was planned to be at a distance of 10,000 km from the nucleus.

Von Rosenvinge, T. T.↗
NASA NTRS1985

The International Cometary Explorer (ICE) mission to comet Giacobini-Zinner (G/Z)

The primary objectives of the International Cometary Explorer (ICE) mission is to provide in situ data on the interaction between solar wind and the atmosphere of the P/Giacobini-Zinner comet (G/Z), making measurements of particles, fields, and waves while passing through the cometary tail of G/Z on September 11, 1985. Following the G/Z tail intercept, the ICE measurements will complement the later upstream measurements obtained by the Comet Halley probe. The major ICE payload includes a vector helium magnetometer, the plasma-wave experiment, the radio-wave experiment, the plasma-electron experiment, and the plasma ion experiment. Other experiments are intended to measure energetic protons, X-rays, low energy to high energy cosmic rays, cosmic ray electrons, and gamma-ray bursts. The ICE measurements of G/Z will be supplemented with ground-based measurements. Schematic diagrams are included.

Brandt, J. C.↗
NASA NTRS1986

A comparison of the fracture behavior of thick laminated composites utilizing compact tension, three-point bend, and center-cracked tension specimens

An experimental study of the effects of specimen configuration and laminate thickness on the fracture behavior of notched laminated composites is presented. The behavior of (0/+, 45/90)ns, (0/90)ns and (0/+, - 45)ns graphite/epoxy T300/5208 laminates was studied. When fracture toughness was computed at the failing load of the center-cracked tension specimen, laminate thickness significantly influenced fracture toughness. If fracture toughness was computed at the interception of the 5 percent secant line with the load-COD record, fracture toughness was found to be independent of both laminate thickness and specimen configuration. Defined in this manner, fracture toughness can be physically interpreted as an indicator of the onset of significant notch-tip damage.

Harris, C. E.↗
NASA NTRS1986

Multifrequency dial sensing of the atmospheric gaseous constituents using the first and second harmonics of a tunable CO2 laser radiation

The results of field measurements of concentration of some gaseous components of the atmosphere along the paths, in Sofia, Bulgaria, using a gas analyzer based on the use of a CO2 laser radiation frequency-doubled with ZnGeP2 monocrystals are presented. The gas analyzer is a traditional long path absorption meter. Radiation from the tunable CO2 laser of low pressure and from an additional He-Ne laser is directed to a colliminating hundredfold Gregori telescope with a 300 mm diameter of the principal mirror. The dimensions of the mirrors of a retroreflector 500 x 500 mm and a receiving telescope allow one to totally intercept the beam passed through the atmospheric layer under study and back.

Zuev, V. E.↗
NASA NTRS1986

Parameterization of albedo, thermal inertia, and surface roughness of desert scrub/sandy soil surface

Spectral albedo, A sub n, for the direct solar beam is defined as A sub n (r sub i,s, theta sub 0) = r sub i exp(-s tan theta sub 0)1-I(s) where I(s) is the integral over all reflection angles describing the interception by the absorbing plants of the flux reflected from the soil, r sub i soil reflectance, assumed Lambertian, S the projection on a vertical plane of plants per unit surface area, and theta sub 0 is the solar zenith angle. Hemispheric reflectance for the direct solar beam equals 1-I(s) times the reflectance to the zenith. The values of s of 0.1, 0.2, and 0.3 respectively quantify sparse, moderately dense, and very dense desert scrub. Thin plants are assumed to be of negligible thermal inertia, and thus directly yield the absorbed insolation to the atmosphere. Surface thermal inertia is therefore effectively reduced. The ratio of surface roughness height to plant height is parameterized for sparse, moderately dense, and very dense desert-scrub as a function of s based on data expressing the dependence of this ratio on plant silhouette.

Otterman, J.↗