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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 235 records · Page 13

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NASA NTRS1982

Organic Rankine power conversion subsystem development for the small community solar thermal power system

The development and preliminary test results for an air-cooled, hermetically sealed 20 kW sub E organic Rankine cycle engine/alternator unit for use with point focussing distributed receiver solar thermal power system. A 750 F toluene is the working fluid and the system features a high speed, single-stage axial flow turbine direct-coupled to a permanent magnet alternator. Good performance was achieved with the unit in preliminary tests.

Barber, R. E.↗

NASA NTRS1995

Simultaneous ultraviolet and X-ray observations of solar microflares

We present a comparison of observations of a solar active region obtained with the Ultraviolet Spectrometer and Polarimeter (UVSP) and the Hard X-ray Imaging Spectrometer (HXIS) on board the Solar Maximum Mission (SMM). The data show many subflares and smaller events during a 9 hr period in which there were no major flares. This activity is associated with areas of complex, evolving magnetic fields. Events substantially smaller than subflares, identified in C IV 1548 A emission (T = 10(exp 5) K), are found to have impulsive counterparts in 3.5-5.5 keV X-ray emission characteristic of T approximately 10(exp 7) K. These 'microflares' are therefore true members of the flare family, reaching temperatures greater than that of the ambient solar corona. Plots of X-ray versus UV emission show that the emission from the smaller microflares is softer than that from the larger microflares and subflares. Distributions of solar flares with energy that are based on hard X-ray fluxes can be corrected using this X-ray/UV relationship. The corrected distributions suggest that microflares play a larger role in coronal heating than was indicated by analysis of the original distributions.

Porter, J. G.↗

NASA NTRS1987

Distributed parameter modeling of the structural dynamics of the Solar Array Flight Experiment

A distributed-parameter model of the structural dynamics of the space-shuttle-deployed Solar Array Flight Experiment is developed and used to produce estimates of the modal frequencies and mode shapes. A lumped parameter version of the distributed model is used to estimate model characteristics by analyzing the measured responses of 32 targets. To make the modeling more tenable, a distributed parameter system is used to reduce the number of unknown parameters, a modified Newton-Raphson technique is used for rapid convergence, and a parallel processing supercomputer is used for more efficient computation. The performances of computers with a high-speed serial processor and with a high-speed parallel processor are compared. The best results are obtained with the modeling approach in which maximum likelihood estimation is applied to distributed parameter models.

Taylor, L. W., Jr.↗

NASA NTRS1977

Distribution of the pre-solar component in Allende and other carbonaceous chondrites

Detailed analyses of separated phases of several Allende Ca-Al-rich inclusions are reported which reveal a consistent pattern of large O-16 enrichments in spinel, pyroxene, and sometimes olivine, and small O-16 enrichments in melilite, feldspathoids, and grossular. The heterogeneous distribution of the O-16 excesses, together with their enhancement in minerals believed to be early solar nebular condensates, suggests the existence of pre-solar carriers of the isotopic anomaly, probably grains or molecules with oxygen which was nearly pure O-16. Pre-solar grains of corundum or spinel, and pre-solar molecules of SiO are considered possibilities. Excess O-16, relative to terrestrial abundances, has been found in all samples of C2, C3 (the Allende is this kind), and C4 carbonaceous chondrites which have been analyzed. No direct correlation has yet been observed between the oxygen anomalies and isotope anomalies in neon, magnesium, or xenon.

Clayton, R. N.↗

NASA NTRS2014

Implementing Badhwar-O'Neill Galactic Cosmic Ray Model for the Analysis of Space Radiation Exposure

For the analysis of radiation risks to astronauts and planning exploratory space missions, accurate energy spectrum of galactic cosmic radiation (GCR) is necessary. Characterization of the ionizing radiation environment is challenging because the interplanetary plasma and radiation fields are modulated by solar disturbances and the radiation doses received by astronauts in interplanetary space are likewise influenced. A model of the Badhwar‐O'Neill 2011 (BO11) GCR environment, which is represented by GCR deceleration potential theta, has been derived by utilizing all of the GCR measurements from balloons, satellites, and the newer NASA Advanced Composition Explorer (ACE). In the BO11 model, the solar modulation level is derived from the mean international sunspot numbers with time‐delay, which has been calibrated with actual flight instrument measurements to produce better GCR flux data fit during solar minima. GCR fluxes provided by the BO11 model were compared with various spacecraft measurements at 1 AU, and further comparisons were made for the tissue equivalent proportional counters measurements at low Earth orbits using the high‐charge and energy transport (HZETRN) code and various GCR models. For the comparison of the absorbed dose and dose equivalent calculations with the measurements by Radiation Assessment Detector (RAD) at Gale crater on Mars, the intensities and energies of GCR entering the heliosphere were calculated by using the BO11 model, which accounts for time‐dependent attenuation of the local interstellar spectrum of each element. The BO11 model, which has emphasized for the last 24 solar minima, showed in relatively good agreement with the RAD data for the first 200 sols, but it was resulted in to be less well during near the solar maximum of solar cycle 24 due to subtleties in the changing heliospheric conditions. By performing the error analysis of the BO11 model and the optimization in reducing overall uncertainty, the resultant BO13 model corrects the fit at solar maxima as well as being accurate at solar minima. The BO13 model is implemented to the NASA Space Cancer Risk model for the assessment of radiation risks. Overall cumulative probability distribution of solar modulation parameters represents the percentile rank of the average interplanetary GCR environment, and the probabilistic radiation risks can be assessed for various levels of GCR environment to support mission design and operational planning for future manned space exploration missions.

Kim, Myung-Hee Y.↗

NASA NTRS2006

Estimating Random Errors Due to Shot Noise in Backscatter Lidar Observations

In this paper, we discuss the estimation of random errors due to shot noise in backscatter lidar observations that use either photomultiplier tube (PMT) or avalanche photodiode (APD) detectors. The statistical characteristics of photodetection are reviewed, and photon count distributions of solar background signals and laser backscatter signals are examined using airborne lidar observations at 532 nm using a photon-counting mode APD. Both distributions appear to be Poisson, indicating that the arrival at the photodetector of photons for these signals is a Poisson stochastic process. For Poisson-distributed signals, a proportional, one-to-one relationship is known to exist between the mean of a distribution and its variance. Although the multiplied photocurrent no longer follows a strict Poisson distribution in analog-mode APD and PMT detectors, the proportionality still exists between the mean and the variance of the multiplied photocurrent. We make use of this relationship by introducing the noise scale factor (NSF), which quantifies the constant of proportionality that exists between the root-mean-square of the random noise in a measurement and the square root of the mean signal. Using the NSF to estimate random errors in lidar measurements due to shot noise provides a significant advantage over the conventional error estimation techniques, in that with the NSF uncertainties can be reliably calculated from/for a single data sample. Methods for evaluating the NSF are presented. Algorithms to compute the NSF are developed for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar and tested using data from the Lidar In-space Technology Experiment (LITE). OCIS Codes:

Liu, Zhaoyan↗

NASA NTRS1979

A 15kWe (nominal) solar thermal electric power conversion concept definition study: Steam Rankine reheat reciprocator system

An evaluation was made of the potential of a steam Rankine reheat reciprocator engine to operate at high efficiency in a point-focusing distributed receiver solar thermal-electric power system. The scope of the study included the engine system and electric generator; not included was the solar collector/mirror or the steam generator/receiver. A parametric analysis of steam conditions was completed leading to the selection of 973 K 12.1 MPa as the steam temperature/pressure for a conceptual design. A conceptual design was completed for a two cylinder/ opposed engine operating at 1800 rpm directly coupled to a commercially available induction generator. A unique part of the expander design is the use of carbon/graphite piston rings to eliminate the need for using oil as an upper cylinder lubricant. The evaluation included a system weight estimate of 230 kg at the mirror focal point with the condenser mounted separately on the ground. The estimated cost of the overall system is $1932 or $90/kW for the maximum 26 kW output.

Fuller, H.↗

NASA NTRS1991

Pitch angle scattering of cometary ions into monospherical and bispherical distributions

Low frequency magnetic fluctuations generated by solar wind/cometary ion distributions cause pitch-angle scattering of cometary ions. The nature of this pitch angle scattering is examined by means of one-dimensional hybrid simulations, in which newborn ions are created at a constant rate, and for various injection angles, alpha, relative to the magnetic field. Pitch angle scattering in the quasi-perpendicular regime (alpha above 60 deg) results in a bispherical velocity distribution while in the quasi-parallel regime (alpha between 0 and 60 deg), pitch angle scattering can result in either a monospherical or bispherical distribution, depending on the injection angle and initial beam velocity.

Miller, Ronald H.↗

NASA NTRS1994

The effect of sea ice on the solar energy budget in the astmosphere-sea ice-ocean system: A model study

A coupled one-dimensional multilayer and multistream radiative transfer model has been developed and applied to the study of radiative interactions in the atmosphere, sea ice, and ocean system. The consistent solution of the radiative transfer equation in this coupled system automatically takes into account the refraction and reflection at the air-ice interface and allows flexibility in choice of stream numbers. The solar radiation spectrum (0.25 micron-4.0 micron) is divided into 24 spectral bands to account adequately for gaseous absorption in the atmosphere. The effects of ice property changes, including salinity and density variations, as well as of melt ponds and snow cover variations over the ice on the solar energy distribution in the entire system have been studied quantitatively. The results show that for bare ice it is the scattering, determined by air bubbles and brine pockets, in just a few centimeters of the top layer of ice that plays the most important role in the solar energy absorption and partitioning in the entire system. Ice thickness is important to the energy distribution only when the ice is thin, while the absorption in the atmosphere is not sensitive to ice thickness exceeds about 70 cm. The presence of clouds moderates all the sensitivities of the absorptive amounts in each layer to the variations in the ice properties and ice thickness. Comparisons with observational spectral albedo values for two simple ice types are also presented.

Jin, Z.↗

NASA NTRS1974

Ground truth data for test sites (SL-3)

Field measurements performed simultaneously with Skylab overpasses in order to provide comparative calibration and performance evaluation measurements for the EREP sensors are presented. The solar radiation region from 400 to 1300 nanometers and the thermal radiation region from 8 to 14 micrometer region were investigated. The measurements of direct solar radiation were analyzed for atmospheric optical depth; the total and reflected solar radiation were analyzed for target reflectivity. These analyses were used in conjunction with a radiative transfer computer program in order to calculate the amount and spectral distribution of solar radiation at the apertures of the EREP sensors. The instrumentation and techniques employed, calibrations and analyses performed, and results obtained are discussed.

Source record↗

NASA NTRS1985

Penetration of solar protons into the Earth's magnetosphere on November 22, 1977

The low polar-orbiting Cosmos-900 satellite carried a large geometric factor Cerenkov counter to study the particle anisotropy and spectrum near the proton increase peak in solar cosmic rays. The data help understand different temporal behavior of the increases detected at the stations because the whole set of data showed that the angular distribution of solar cosmic ray particles in interplanetary space was narrow throughout the observation time, resulting in a rapid variation of particle intensity near the poles. The power-law index of the solar cosmic ray integral spectrum varied from -2.4 to -5.2 in the 1 to 4 GV rigidity range from 10.31 to 11.25 UT on November 22, 1977. The flare-time data from all orbits indicate an increased radiation intensity on L=3.5 to 4.0.

Gorchakov, E. V.↗

NASA NTRS1972

Measurement of the degree of anisotropy of the cosmic radiation using the IMP space vehicle

The detector and data reduction techniques used in connection with the cosmic ray experiments designed for and flown on Explorer 34 and 41 satellites are described. A history of the program development and the present status of data processing are briefly summarized. The instrument to measure the anisotropy and energy spectra of cosmic ray electrons and protons, and X-rays of solar and galactic origin is discussed. The main characteristics of the detectors and the stability during 23 months of operation are described. The method of analysis of the angular distribution of solar cosmic ray particles in the ecliptic plane is given. It is shown that the anisotropy of low energy particles of solar origin decreases sharply to a very small value when the satellite penetrates the magnetosphere.

Palmeira, R. A. R.↗

NASA NTRS1977

Atmospheric transformation of solar radiation reflected from the ocean

Airborne measurements of the brightness spectrum of the Atlantic Ocean in the wavelength region from 0.4 to 0.7 micron are analyzed. These measurements were made over a tropical region of the Atlantic from an aircraft at heights of 0.3 and 10.5 km during the TROPEX-72 experiment. The results are used to estimate the contribution of the atmosphere to the overall brightness of the ocean-atmosphere system. It is concluded that: (1) the atmosphere decreases the absolute brightness of the ocean by a factor of 5 to 10 and also strongly affects the spectral behavior of solar radiation reflected from the ocean surface; (2) the atmospheric contribution to overall brightness may vary considerably under real conditions; (3) finely dispersed particles and Rayleigh scattering affect the spectral distribution of solar radiation; and (4) the spectral composition of ocean-atmosphere brightness may be completely governed by the atmosphere.

Malkevich, M. S.↗

NASA NTRS1991

Sand and dust issues for the MESUR mission

The presence of particles in the Martian atmosphere increases the rate of erosion of the heat shield during the entry phase of the MESUR mission. Preliminary analysis has shown that under certain conditions particles will penetrate the bow shock of the entry vehicle, impact and erode the heat shield, above the anticipated rate from the ablation process. Knowledge of the distribution, sizes, and composition of particles suspended in the atmosphere will permit the estimation of the heat shield recession both for a nominal Mars atmosphere and in dust storm conditions. On the surface of Mars, sand and dust can effect the operations and design of the science instruments (i.e., imaging) and lander subsystems (i.e., solar arrays). Distribution and deposition of sand and dust on the planet's surface will dictate the feasibility of using solar arrays as a power source for the lander. Furthermore, the potential abrasive nature of blowing particles must be understood in order to properly select suitable materials for lander structure and any components exposed to the environment. The selection of lander material may also be dictated by corrosive and chemically active properties of particles at a potential landing site. Some key interests concerning sand and dust on the surface and in the atmosphere are summarized in a number of questions that are included.

Wercinski, P. F.↗

NASA NTRS1987

Precise timing of the last interglacial period from mass spectrometric determination of thorium-230 in corals

The development of mass spectrometric techniques for determination of Th-230 abundance has made it possible to reduce analytical errors in (U-238)-(U-234)-(Th-230) dating of corals even with very small samples. Samples of 6 x 10 to the 8th atoms of Th-230 can be measured to an accuracy of + or - 3 percent (2sigma), and 3 x 10 to the 10th atoms of Th-230 can be measured to an accuracy of + or - 0.2 percent. The time range over which useful age data on corals can be obtained now ranges from about 50 to about 500,000 years. For young corals, this approach may be preferable to C-14 dating. The precision with which the age of a coral can now be determined should make it possible to critically test the Milankovitch hypothesis concerning Pleistocene climate fluctuations. Analyses of a number of corals that grew during the last interglacial period yield ages of 122,000 to 130,000 years. The ages coincide with, or slightly post-date, the summer solar insolation high at 65 deg N latitude which occurred 128,000 years ago. This supports the idea that changes in Pleistocene climate can be the result of variations in the distribution of solar insolation caused by changes in the geometry of the earth's orbit and rotation axis.

Chen, J. H.↗

NASA NTRS2002

Compositional Remote Sensing of Icy Planets and Satellites Beyond Jupiter

The peak of the solar energy distribution occurs at visual wavelengths and falls off rapidly in the infrared. This fact, improvements in infrared detector technology, and the low surface temperatures for most icy objects in the outer solar system have resulted in the bulk of telescopic and spacecraft observations being performed at visual and near-infrared wavelengths. Such observations, begun in the early 1970's and continuing to present, have provided compositional information regarding the surfaces of the satellites of Saturn and Uranus, Neptune's moon Triton, Pluto, Pluto's moon Charon, Centaur objects, and Kuiper belt objects. Because the incident sunlight penetrates the surface and interacts with the materials present there, the measured reflected sunlight contains information regarding the surface materials, and the ratio of the reflected to incident sunlight provides a mechanism of identifying the materials that are present.

Roush, T. L.↗

NASA NTRS2002

Compositional Remote Sensing of Icy Planets and Satellites Beyond Jupiter

Roush, Ted L.↗

NASA NTRS1987

Solar irradiance change and special longitudes due to r-modes

Sluggish global oscillations, having a periodicity of months and trapped in the sun's convection zone, modulate the amount of energy reaching earth and seem to impose some large-scale order on the distribution of solar surface features. These recently recognized oscillations (r-modes) increase the predictability of solar changes and may improve understanding of rotation and variability in other stars. Most of the 13 periodicities ranging from 13 to 85 days that are caused by r-modes can be detected in Nimbus 7 observations of solar irradiance during 3 years at solar maximum. These modes may also bear on the classical question of persistent longitudes of high solar activity.

Wolff, Charles L.↗