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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Development of thermal energy storage units for spacecraft cryogenic coolers

Thermal Energy Storage Units were developed for storing thermal energy required for operating Vuilleumier cryogenic space coolers. In the course of the development work the thermal characteristics of thermal energy storage material was investigated. By three distinctly different methods it was established that ternary salts did not release fusion energy as determined by ideality at the melting point of the eutectic salt. Phase change energy was released over a relatively wide range of temperature with a large change in volume. This strongly affects the amount of thermal energy that is available to the Vuilleumier cryogenic cooler at its operating temperature range and the amount of thermal energy that can be stored and released during a single storage cycle.

Richter, R.↗
NASA NTRS1983

Spectral study of wintertime kinetic energy of the Northern Hemisphere in the troposphere

Characteristics of the kinetic energy of wind fields at various pressure levels were analyzed, and significant wavenumbers in the wavenumber-frequency domain were identified. The nonlinear interaction terms of the kinetic energy equation were examined, and the distribution of the kinetic energy at the 850 mb, 500 mb, and 200 mb levels was calculated. A 5 deg latitude-longitude square grid was used, with NMC data for the 1975-1976 winter in the 20-60 deg N at 500 mb and 20-85 deg N for the 200 mb and 850 mb levels. The kinetic energy distribution was determined to be geography-dependent, with wavenumbers 6-9 westerly waves in the midfrequency range contributing significantly to kinetic energy maxima over the North Pacific and the east coast of North America. The contribution of the nonlinear interactions of these waves, which correspond to the longitudinal convergence of the kinetic energy flux, was found to be larger than the meridional convergence of the kinetic energy flux, and to occur mainly between 30-50 deg N. The nonlinear interactions were a negative contribution over the North Pacific at the 200 mb level.

Lee, H. N.↗
NASA NTRS1983

Roles of divergent and rotational winds in the kinetic energy balance during intense convective activity

Contributions of divergent and rotational wind components to the synoptic-scale kinetic energy balance are described using rawinsonde data at 3 and 6 h intervals from NASA's fourth Atmospheric Variability experiment. Two intense thunderstorm complexes occurred during the period. Energy budgets are described for the entire computational region and for limited volumes that enclosed storm-induced, upper level wind maxima located poleward of convection. Although small in magnitude, the divergent wind component played an important role in the cross-contour generation and horizontal flux divergence of kinetic energy. The importance of V(D) appears directly related to the presence and intensity of convection. Although K(D) usually comprised less than 10 percent of the total kinetic energy content, generation of kinetic energy by V(D) was a major factor in the creation of upper-level wind maxima to the north of the storm complexes. Omission of the divergent wind apparently would lead to serious misrepresentations of the energy balance. A random error analysis is presented to assess confidence limits in the various energy parameters.

Fuelberg, H. E.↗
NASA NTRS1983

Nonthermal components of low energy electrons in the ionospheric E and F region

Rocket-borne instrument observations of very low energy electrons' energy distribution in the ionospheric E and F regions showed the regions to exist where an enhanced, high energy tail of thermal electrons appeared. One such appearance was amid a region of high electron temperature, T(e),associated with the Sq anomaly, where there were large T(e) deviations from the neutral temperature. The associated electron heating was most intense at 107 km, gradually decreasing toward 130 km, where both the T(e) and the excess high energy tail became small. In the second region, excess electrons appeared in the high energy tail at 135 km, reached an intensity peak at 150 km, and gradually decreased toward 210 km. It is suggested that the anomalously elevated T(e) and the enhanced energy tail in the first region were locally generated by some dynamo current-related mechanism distinct from Joule heating. The second region's high energy tail is also related to ionospheric currents.

Oyama, K. I.↗
NASA NTRS1983

The high energy X-ray spectra of supernova remnants

The results of fitting an ionization-nonequilibrium (INE) model to the high-energy (above 5-keV) X-ray spectra of the young supernova remnants Cas A and Tycho are presented. As an additional constraint, the models must simultaneously fit lower-energy, higher-resolution data. For Cas A, a single INE component cannot adequately reproduce the features for the entire X-ray spectrum because the ionization structure of iron ions responsible for the K emission is inconsistent with that of the ions responsible for the lower-energy lines, and the flux of the highest-energy X-rays is underestimated. The iron K line and the high-energy continuum could arise from the same INE component, but the identification of this component with either the blast wave or the ejecta in the standard model is difficult. In Tycho, the high-energy data rule out a class of models for the lower-energy data which have too large a continuum contribution.

Pravdo, S. H.↗
NASA NTRS1985

The Energy Spectrum of Jovian Electrons in Interplanetary Space

The energy spectrum of electrons with energies approx 10 to approx 180 MeV measured with the electron telescope on the Voyager 1 and 2 spacecraft in interplanetary space from 1978 to 1983 is studied. The kinetic energy of electrons is determined by double dE/dx measurements from the first two detectors (D sub 1, D sub 2) of a stack of eight solid state detectors and by the range of particle penetration into the remaining six detectors (D sub 3 to D sub 8) which are interleaved with tungsten absorbers. From 1978 to 1983 (radial range approximately 2 to a pproximately 12 AU) electrons of Jovian origin were clearly observable for electrons stopping in D(sub 3(E approximately greater than 4 MeV)) and in D(sub 4 (E approximately greater than 8 MeV)). For electrons stopping in D(sub 5(E approximately greather than 12 MeV)), the jovian flux dominated the galactic electron flux for a period of approximately one year near the encounter with Jupiter. Jovian electrons were also observed in D(sub 6(E approximately greater than 21 MeV)) but not in D(sub 7(E approximately greater than 28 MeV)). A detailed interpretation of the electron variations in all energy channels depends on an accurate subtraction of background induced by energetic protons of a few 100 MeV. This substraction is facilitated by laboratory calibration results at several energies. Further results on the differential energy spectrum of Jovian electrons and limits on the maximum detected energies will be reported.

Christon, S. P.↗
NASA NTRS1985

Ion and electron energy dispersion features detected by ISEE 1

An energy dispersion feature observed by the ISEE 1 medium energy particle instrument is reported. This feature is characterized by enhancements in both electron and ion fluxes which occur in the 20-200 keV energy range and at radial distances from 5 to 13.5 earth radii. There is a strong energy dependence in the onset times of the enhancements. The time period between the first appearance of an enhancement at high energy to its eventual disappearance in the 20 keV channel can be as much as an hour. The duration of the enhancement in a given energy channel decreases with increasing energy. The species and pitch angle of particles in which the feature is most marked depend on local time. It is shown that the feature is a new manifestation of an old phenomenon, the drift dispersion that frequently produces signatures in particle data from geosynchronous satellites.

Greenspan, M. E.↗
NASA NTRS1989

Cosmic strings and ultra-high energy cosmic rays

The flux is calculated of ultrahigh energy protons due to the process of cusp evaporation from cosmic string loops. For the standard value of the dimensionless cosmic string parameter epsilon is identical to G(sub mu) approx. = 10(exp -6), the flux is several orders of magnitude below the observed cosmic ray flux of ultrahigh energy protons. However, the flux at any energy initially increases as the value of epsilon is decreased. This at first suggests that there may be a lower limit on the value of epsilon, which would imply a lower limit on the temperature of a cosmic string forming phase transition in the early universe. However, the calculation shows that this is not the case -- the particle flux at any energy reaches its highest value at epsilon approx. = 10(exp -15) and it then decreases for further decrease of the value of epsilon. This is due to the fact that for too small values of epsilon (less than 10(exp -15)), the energy loss of the loops through the cusp evaporation process itself (rather than gravitational energy loss of the loops) becomes the dominant factor that controls the behavior of the number density of the loops at the relevant times of emission of the particles. The highest flux at any energy remains at least four orders of magnitude below the observed flux. There is thus no lower limit on epsilon.

Bhattacharjee, Pijushpani↗
NASA NTRS1990

Auroral modeling of the 3371 A emission rate - Dependence on characteristic electron energy

An efficient two-stream auroral electron model is used to study the deposition of auroral energy and the dependence of auroral emission rates on characteristic energy. This model incorporates the concept of average energy loss to reduce the computation time. This simple two-stream model produces integrated emission rates that are in excellent agreement with the much more complex multistream model of Strickland et al. (1983) but disagrees with a recent study by Rees and Lummerzheim (1989) that indicates that the N2 second positive emission rate is a strongly decreasing function of the characteristic energy of the precipitating flux. These calculations reveal that a 10 keV electron will undergo approximately 160 ionizing collisions, with an average energy loss per collision of 62 eV before thermalizing. The secondary electrons are created with an average energy of 42 eV. When all processes including the backscattered escape fluxes are taken into account, the average energy loss per electron-ion pair is 35 eV in good agreement with laboratory results.

Richards, P. G.↗
NASA NTRS1991

Fusion energy for space missions in the 21st Century

Future space missions were hypothesized and analyzed and the energy source for their accomplishment investigated. The mission included manned Mars, scientific outposts to and robotic sample return missions from the outer planets and asteroids, as well as fly-by and rendezvous mission with the Oort Cloud and the nearest star, Alpha Centauri. Space system parametric requirements and operational features were established. The energy means for accomplishing the High Energy Space Mission were investigated. Potential energy options which could provide the propulsion and electric power system and operational requirements were reviewed and evaluated. Fusion energy was considered to be the preferred option and was analyzed in depth. Candidate fusion fuels were evaluated based upon the energy output and neutron flux. Reactors exhibiting a highly efficient use of magnetic fields for space use while at the same time offering efficient coupling to an exhaust propellant or to a direct energy convertor for efficient electrical production were examined. Near term approaches were identified.

Schulze, Norman R.↗
NASA NTRS1992

Development of a differentially balanced magnetic bearing and control system for use with a flywheel energy storage system

The purpose of a magnetically suspended flywheel energy storage system for electric utility load leveling is to provide a means to store energy during times when energy is inexpensive to produce and then return it to the customer during times of peak power demand when generated energy is most expensive. The design of a 20 kWh flywheel energy storage system for electric utility load leveling applications involves the successful integration of a number of advanced technologies so as to minimize the size and cost of the system without affecting its efficiency and reliability. The flywheel energy storage system uses a carbon epoxy flywheel, two specially designed low loss magnetic bearings, a high efficiency motor generator, and a 60 cycle AC power converter all integrated through a microprocessor controller. The basic design is discussed of each of the components that is used in the energy storage design.

Higgins, Mark A.↗
NASA NTRS1991

Biological effectiveness of high-energy protons - Target fragmentation

High-energy protons traversing tissue produce local sources of high-linear-energy-transfer ions through nuclear fragmentation. The contribution of these target fragments to the biological effectiveness of high-energy protons using the cellular track model is examined. The effects of secondary ions are treated in terms of the production collision density using energy-dependent parameters from a high-energy fragmentation model. Calculations for mammalian cell cultures show that at high dose, at which intertrack effects become important, protons deliver damage similar to that produced by gamma rays, and with fragmentation the relative biological effectiveness (RBE) of protons increases moderately from unity. At low dose, where sublethal damage is unimportant, the contribution from target fragments dominates, causing the proton effectiveness to be very different from that of gamma rays with a strongly fluence-dependent RBE. At high energies, the nuclear fragmentation cross sections become independent of energy. This leads to a plateau in the proton single-particle-action cross section, below 1 keV/micron, since the target fragments dominate.

Cucinotta, Francis A.↗
NASA NTRS1992

Fusion energy for space: Feasibility demonstration. A proposal to NASA

This proposed program is to initiate a space flight research and development program to develop fusion energy for the space applications of direct space propulsion and direct space power, that is, a Space Fusion Energy (SFE) program. 'Direct propulsion' refers to the use of plasma energy directly for thrust without requiring other energy conversion systems. Further, to provide space missions with large electrical power, 'direct space power' is proposed whereby the direct conversion of charged particles into electricity is used, thereby avoiding thermal conversion system losses. The energy release from nuclear fusion reactions makes these highly efficient, high power space systems possible. The program as presented conducts in an orderly, hierarchical manner the necessary planning, analyses, and testing to demonstrate the practical use of fusion energy for space. There is nothing discussed that is known to be theoretically impossible. Validation of the engineering principles is sought in this program which uses a cost-benefit approach. Upon successful program completion, space will become more accessible and space missions more safely conducted. The country will have taken a giant step toward the commercialization of space. The mission enabling capability provided by fusion energy is well beyond mission planners' current dreams.

Schulze, Norman R.↗
NASA NTRS1992

High-flux source of low-energy neutral beams using reflection of ions from metals

Reflection of low-energy ions from surfaces can be applied as a method of producing high-flux beams of low-energy neutral particles, and is an important effect in several areas of plasma technology, such as in the edge region of fusion devices. We have developed a beam source based on acceleration and reflection of ions from a magnetically confined coaxial RF plasma source. The beam provides a large enough flux to allow the energy distribution of the reflected neutrals to be measured despite the inefficiency of detection, by means of an electrostatic cylindrical mirror analyzer coupled with a quadrupole mass spectrometer. Energy distributions have been measured for oxygen, nitrogen, and inert gas ions incident with from 15 to 70 eV reflected from amorphous metal surfaces of several compositions. For ions of lighter atomic mass than the reflecting metal, reflected beams have peaked energy distributions; beams with the peak at 4-32 eV have been measured. The energy and mass dependences of the energy distributions as well as measurements of absolute flux, and angular distribution and divergence are reported. Applications of the neutral beams produced are described.

Cuthbertson, John W.↗
NASA NTRS1993

Energy considerations in computational aeroacoustics

A finite-volume multistage time-stepping Euler code is used to investigate the use of CFD algorithms for the direct calculation of acoustics. The 2D compressible inviscid flow about an accelerating or decelerating circular cylinder is used as a model problem. The time evolution of the energy transfer from the cylinder to the fluid, as the cylinder is moved from rest to some nonnegligible velocity, is clearly seen. By examining the temporal and spatial characteristics of the numerical solution, a distinction can be made between the propagating acoustic energy, the convecting energy associated with the entropy change in the fluid, and the energy contained in the local aerodynamic field. Systematic variation of the cylinder acceleration shows that the radiated acoustic energy depends strongly upon the rate of acceleration or deceleration. The computational grid has a large effect on the ratio of acoustic energy to nonphysical entropy associated energy, while the role of the explicit artificial viscosity seems to be of second order. The entropy term was nearly negligible in all cases the cylinder was started slowly.

Brentner, Kenneth S.↗
NASA NTRS1994

Axial focusing of impact energy in the Earth's interior: Proof-of-principle tests of a new hypothesis

A causal link between major impact events and global processes would probably require a significant change in the thermal state of the Earth's interior, presumably brought about by coupling of impact energy. One possible mechanism for such energy coupling from the surface to the deep interior would be through focusing due to axial symmetry. Antipodal focusing of surface and body waves from earthquakes is a well-known phenomenon which has previously been exploited by seismologists in studies of the Earth's deep interior. Antipodal focusing from impacts on the Moon, Mercury, and icy satellites has also been invoked by planetary scientists to explain unusual surface features opposite some of the large impact structures on these bodies. For example, 'disrupted' terrains have been observed antipodal to the Caloris impact basis on Mercury and Imbrium Basin on the Moon. Very recently there have been speculations that antipodal focusing of impact energy within the mantle may lead to flood basalt and hotspot activity, but there has not yet been an attempt at a rigorous model. A new hypothesis was proposed and preliminary proof-of-principle tests for the coupling of energy from major impacts to the mantle by axial focusing of seismic waves was performed. Because of the axial symmetry of the explosive source, the phases and amplitudes are dependent only on ray parameter (or takeoff angle) and are independent of azimuthal angle. For a symmetric and homogeneous Earth, all the seismic energy radiated by the impact at a given takeoff angle will be refocused (minus attenuation) on the axis of symmetry, regardless of the number of reflections and refractions it has experienced. Mantle material near the axis of symmetry will experience more strain cycles with much greater amplitude than elsewhere and will therefore experience more irreversible heating. The situation is very different than for a giant earthquake, which in addition to having less energy, has an asymmetric focal mechanism and a larger area. Two independent proof-of-principle approaches were used. The first makes use of seismic simulations, which are being performed with a realistic Earth model to determine the degree of focusing along the axis and to estimate the volume of material, if any, that experiences significant irreversible heating. The second involves two-dimensional hydrodynamic code simulations to determine the stress history, internal energy, and temperature rise as a function of radius along the axis.

Boslough, M. B.↗
NASA NTRS1992

Energy dissipation in substorms

The energy dissipated by substorms manifested in several ways is discussed: the Joule dissipation in the ionosphere; the energization of the ring current by the injection of plasma sheet particles; auroral election and ion acceleration; plasmoid ejection; and plasma sheet ion heating during the recovery phase. For each of these energy dissipation mechanisms, a 'rule of thumb' formula is given, and a typical dissipation rate and total energy expenditure is estimated. The total energy dissipated as Joule heat (approximately) 2 x 10(exp 15) is found about twice the ring current injection term, and may be even larger if small scale effects are included. The energy expended in auroral electron precipitation, on the other hand, is smaller than the Joule heating by a factor of five. The energy expended in refilling and heating the plasma sheets is estimated to be approximately 5 x 10(exp 14)J, while the energy lost due to plasmoid ejection is between (approximately) (10 exp 13)(exp 14)J.

Weiss, Loretta A.↗
NASA NTRS1995

Surface conversion techniques for low energy neutral atom imagers

This investigation has focused on development of key technology elements for low energy neutral atom imaging. More specifically, we have investigated the conversion of low energy neutral atoms to negatively charged ions upon reflection from specially prepared surfaces. This 'surface conversion' technique appears to offer a unique capability of detecting, and thus imaging, neutral atoms at energies of 0.01 - 1 keV with high enough efficiencies to make practical its application to low energy neutral atom imaging in space. Such imaging offers the opportunity to obtain the first instantaneous global maps of macroscopic plasma features and their temporal variation. Through previous in situ plasma measurements, we have a statistical picture of large scale morphology and local measurements of dynamic processes. However, with in situ techniques it is impossible to characterize or understand many of the global plasma transport and energization processes. A series of global plasma images would greatly advance our understanding of these processes and would provide the context for interpreting previous and future in situ measurements. Fast neutral atoms, created from ions that are neutralized in collisions with exospheric neutrals, offer the means for remotely imaging plasma populations. Energy and mass analysis of these neutrals provides critical information about the source plasma distribution. The flux of neutral atoms available for imaging depends upon a convolution of the ambient plasma distribution with the charge exchange cross section for the background neutral population. Some of the highest signals are at relatively low energies (well below 1 keV). This energy range also includes some of the most important plasma populations to be imaged, for example the base of the cleft ion fountain.

Quinn, J. M.↗