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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Long term effects of low doses of Fe-56 ions on the brain and retina of the mouse - Ultrastructural and behavioral studies

Eight-month-old male C57BL6 mice were exposed without anesthesia to whole-body irradiation in circular holders. The mice were tested for behavioral decrements after 0.5 and 50 rads of Fe particle irradiation at 6 and 12 months postirradiation to obtain long-term results. A standard maze was used, and the animals were timed for completion thereof. A string test also was administered to the mice, testing their ability to grasp and move along a string to safety. The results from animals exposed to 50 rads were significantly different from control results to p = less than 0.001 in both systems of testing. The hippocampus (believed to be the location of environmental interaction in the brain) and the retina were examined for ultrastructural changes. The ultrastructural changes were similar to those found in the Cosmos 782, 936, and Argon experiments. The mouse data indicate that iron particles were able to induce long-term changes in the central nervous system which led to behavioral impairment.

Philpott, Delbert E.↗
NASA NTRS1986

Long term effects of low doses of 56Fe ions on the brain and retina of the mouse: ultrastructural and behavioral studies

Eight month old male C57BL6 mice were exposed without anesthesia to whole-body irradiation in circular holders. The mice were tested for behavioral decrements after 0.5 and 50 rads of Fe particle irradiation at 6 and 12 months post irradiation to obtain long term results. A standard maze was used and the animals were timed for completion thereof. A string test also was administered to the mice, testing their ability to grasp and move along a string to safety. The results from animals exposed to 50 rads were significantly different from [correction of fron] control results to p = < .001 in both systems of testing. The hippocampus (believed to be the location of environmental interaction in the brain) and the retina were examined for ultrastructural changes. The ultrastructural changes were similar to those we found in our Cosmos 782, 936 and in our Argon experiments. The mouse data indicate that iron particles were able to induce long term changes in the central nervous system which lead to behavioral impairment.

NASA Program Space Medicine↗
DOE OSTI2022

Order fractionalization in a Kitaev-Kondo model

We describe a mechanism for order fractionalization in a two-dimensional Kondo lattice model, in which electrons interact with a gapless spin liquid of Majorana fermions described by the Yao-Lee (YL) model. When the Kondo coupling to the conduction electrons exceeds a critical value, the model develops a superconducting instability into a state with a a spinor order parameter with charge 4 and spin ( = 1 2. The broken symmetry state develops a gapless Majorana Dirac cone in the bulk. By including an appropriate gauge string, we can show that the charge 4, spinorial order develops off-diagonal long range order that allows electrons to coherently tunnel arbitrarily long distances through the spin liquid.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Spinning no-scale $${\mathcal {F}}$$-SU(5) in the right direction

Abstract The Fermi National Accelerator Laboratory (FNAL) recently announced confirmation of the Brookhaven National Lab (BNL) measurements of the $$g-2$$ g - 2 of the muon that uncovered a discrepancy with the theoretically calculated Standard Model value. We suggest an explanation for the combined BNL+FNAL 4.2 $$\sigma $$ σ deviation within the supersymmetric grand unification theory (GUT) model No-Scale $${\mathcal {F}}$$ F - $$SU(5)$$ S U ( 5 ) supplemented with a string derived TeV-scale extra $$10+\overline{10}$$ 10 + 10 ¯ vector-like multiplet and charged vector-like singlet $$(XE,XE^c)$$ ( X E , X E c ) , dubbed flippons. We introduced these vector-like particles into No-Scale Flipped SU (5) many years ago, and as a result, the renormalization group equation (RGE) running was immediately shaped to produce a distinctive and rather beneficial two-stage gauge coupling unification process to avoid the Landau pole and lift unification to the string scale, in addition to contributing through 1-loop to the light Higgs boson mass. The flippons have long stood ready to tackle another challenge, and now do so yet again, where the charged vector-like “lepton”/singlet couples with the muon, the supersymmetric down-type Higgs $$H_d$$ H d , and a singlet S , using a chirality flip to easily accommodate the muonic $$g-2$$ g - 2 discrepancy in No-Scale $${\mathcal {F}}$$ F - $$SU(5)$$ S U ( 5 ) . Considering the phenomenological success of this string derived model over the prior 11 years that remains accommodative of all presently available LHC limits plus all other experimental constraints, including no fine-tuning, and the fact that for the first time a Starobinsky-like inflationary model consistent with all cosmological data was derived from superstring theory in No-Scale Flipped SU (5), we believe it is imperative to reconcile the BNL+FNAL developments within the model space.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1999

Performance Characteristics of Lithium-Ion Cells for Mars Sample Return Athena Rover

In contrast to the primary batteries (lithium thionyl chloride) on the Sojourner Mars Rover and the upcoming 2001 Mars Rover, the Mars Sample Return (MSR) Athena Rover will utilize rechargeable lithium ion batteries, following the footsteps of MSP 2001 Lander. The MSR Athena Rover will contain a rechargeable lithium ion battery of 16 V and a total energy of 150 Wh. The mass and volume of the projected power system will be a maximum of 3 kg and 2 liters, respectively. Each battery consists of twelve cells (6-7 Ah), combined in three parallel strings of four cells (16 V) each, such that the capability of the Rover shall be maintained even in the event of one string failure. In addition to the usual requirements of high specific energy and energy density and long cycle life (100 cycles), the battery is required to operate at wide range of temperatures, especially at sub-zero temperatures down to -20 C. In this paper, we report various performance characterization tests carried out on lithium ion cells, fabricated by different manufacturers under a NASA/DoD lithium ion battery consortium.

Ratnakumar, B. V.↗
DOE OSTI2022

Mapping out the internal space in AdS/BCFT with Wilson loops

We study Wilson loops in string theory realizations of AdS/BCFT and wedge holography. The field theories are based on 3d N = 4 long quiver gauge theories engineered by D3, D5 and NS5 branes, and on BCFTs involving 4d N = 4 SYM coupled to such 3d theories. The holographic duals have geometry AdS 4 × S 2 × S 2 warped over a strip. We identify the holographic representation of antisymmetric Wilson loops associated with individual 3d gauge nodes in terms of probe D5-branes. The expectation values obtained holographically are matched to supersymmetric localization computations. Our results yield an identification of regions in the internal space with individual 3d gauge nodes. Connecting to bottom-up braneworld models, this gives a concrete notion of which parts of the 10d solutions correspond to the end-of-the-world brane and which to the remaining bulk. We also construct supersymmetric Janus on the brane embeddings in AdS 5 ×S 5 , which describe surface defects with boundaries and interfaces in N = 4 SYM.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1993

LDEF Space Plasma-High Voltage Drainage Experiment post-flight results

The Space Plasma-High Voltage Drainage Experiment (SP-HVDE) was comprised of two identical experimental trays. With one tray located on the leading (ram facing, B10) edge and the other located on the trailing (wake facing, D4) edge of the Long Duration Exposure Facility (LDEF), it was possible to directly compare the effects of ram and wake spacecraft environments on charged dielectric materials. Six arrays of Kapton dielectric samples of 2 mil, 3 mil, and 5 mil thicknesses maintained at +/- 300, +/- 500, and +/- 1000 voltage bias formed the experimental matrix of each tray. In addition, each tray carried two solar cell strings, one biased at +300 volts and the other at -300 volts, to study current leakage from High Voltage Solar Arrays (HVSA). The SP-HVDE provides the first direct, long-term, in-flight measurements of average leakage current through dielectric materials under electric stress. The experiment also yields information on the long term stability of the bulk dielectric properties of such materials. Data and findings of the SP-HVDE are an extension of those from shorter term flight experiments such as the PIX-1 (Plasma Interaction Experiment) and PIX-2 and are therefore valuable in the design and evaluation of long-lived space systems with high voltage systems exposed to the low earth orbital environment. A summary of the SP-HVDE post flight analysis final report delivered to the LDEF Project Office under contract to the National Aeronautics and Space Administration is presented.

Yaung, J. Y.↗
NASA NTRS1990

An investigation of messy genetic algorithms

Genetic algorithms (GAs) are search procedures based on the mechanics of natural selection and natural genetics. They combine the use of string codings or artificial chromosomes and populations with the selective and juxtapositional power of reproduction and recombination to motivate a surprisingly powerful search heuristic in many problems. Despite their empirical success, there has been a long standing objection to the use of GAs in arbitrarily difficult problems. A new approach was launched. Results to a 30-bit, order-three-deception problem were obtained using a new type of genetic algorithm called a messy genetic algorithm (mGAs). Messy genetic algorithms combine the use of variable-length strings, a two-phase selection scheme, and messy genetic operators to effect a solution to the fixed-coding problem of standard simple GAs. The results of the study of mGAs in problems with nonuniform subfunction scale and size are presented. The mGA approach is summarized, both its operation and the theory of its use. Experiments on problems of varying scale, varying building-block size, and combined varying scale and size are presented.

Goldberg, David E.↗
DOE OSTI2023

Bootstrapping boundaries and branes

The study of conformal boundary conditions for two-dimensional conformal field theories (CFTs) has a long history, ranging from the description of impurities in one-dimensional quantum chains to the formulation of D-branes in string theory. Nevertheless, the landscape of conformal boundaries is largely unknown, including in rational CFTs, where the local operator data is completely determined. We initiate a systematic bootstrap study of conformal boundaries in 2d CFTs by investigating the bootstrap equation that arises from the open-closed consistency condition of the annulus partition function with identical boundaries. We find that this deceivingly simple bootstrap equation, when combined with unitarity, leads to surprisingly strong constraints on admissible boundary states. In particular, we derive universal bounds on the tension (boundary entropy) of stable boundary conditions, which provide a rigorous diagnostic for potential D-brane decays. We also find unique solutions to the bootstrap problem of stable branes in a number of rational CFTs. Along the way, we observe a curious connection between the annulus bootstrap and the sphere packing problem, which is a natural extension of previous work on the modular bootstrap. We also derive bounds on the boundary entropy at large central charge. These potentially have implications for end-of-the-world branes in pure gravity on AdS 3 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1989

The area of isodensity contours in cosmological models and galaxy surveys

The contour crossing statistic, defined as the mean number of times per unit length that a straight line drawn through the field crosses a given contour, is applied to model density fields and to smoothed samples of galaxies. Models in which the matter is in a bubble structure, in a filamentary net, or in clusters can be distinguished from Gaussian density distributions. The shape of the contour crossing curve in the initially Gaussian fields considered remains Gaussian after gravitational evolution and biasing, as long as the smoothing length is longer than the mass correlation length. With a smoothing length of 5/h Mpc, models containing cosmic strings are indistinguishable from Gaussian distributions. Cosmic explosion models are significantly non-Gaussian, having a bubbly structure. Samples from the CfA survey and the Haynes and Giovanelli (1986) survey are more strongly non-Gaussian at a smoothing length of 6/h Mpc than any of the models examined. At a smoothing length of 12/h Mpc, the Haynes and Giovanelli sample appears Gaussian.

Ryden, Barbara S.↗
NASA NTRS1995

Theoretical properties of Omega-loops in the convective zone of the Sun. 3: Extended updrafts

It was pointed out in an earlier paper that the continuing emergence of Omega-loops at localized sites on the surface of the Sun indicates a continuing updraft at those sites. The updraft evidently extends all the way from the base of the convective zone to somewhat near (approximately 10(exp 9)cm) the surface. We pointed out that such updrafts enhance the convective heat transport to the surface, accounting for a major part of the increased solar brightness or irradiance during times of solar activity. The problem is to work out, as much as possible, the dynamical nature of the extended updrafts, initiated as the wakes of successive rising Omega-loops and driven therafter by the convective forces. The question is, does the updraft take on a long-lived columnar form of its own, or does it never devlop beyond a sequence of rising wakes, resembling beads on a string? The dynamics of a columnar updraft is complicated by both the large Reynolds number and the strong stratication of the atmosphere, and by a total lack of direct observational information. Extended slender updrafts are not a spontaneous occurrence in numerical simulations of thermal convection in a stratified atmosphere, although slender concentrated downdrafts commonly occur. This paper examines several aspects of a columnar updrft in a convective atmosphere under various idealized circumstances to investigate to what extent that state can be maintained against the diminishing vorticity and expansion in the updraft. It appears that the successive passage of Omega-loops from the bottom to the top of the convective zone is an essential feature of the continuing existence of the updraft.

Parker, E. N.↗
NASA NTRSDate not supplied

PPE Electric Propulsion Advancing to CDR: 12kW String

String level testing is a vital part of electric propulsion development. With the Power and Propulsion Element (PPE) spacecraft flying two new models of Hall Thrusters, this work is even more critical. PPE will have both 6kW and 12kW thruster strings onboard, all powered by Maxar power processing units (PPU). Both strings have recently undergone end-to-end string level hot fire testing to verify the ability of all components to work together. This entails operating the thruster with the Xenon Flow Controller (XFC) and PPUs under both nominal and off-nominal conditions to stress the system and determine weak points. Such testing has long been a standard Maxar practice since our first 1.5kW electric propulsion system in 2004. This paper will focus on Phase 1 of the 12kW testing recently completed at NASA Glenn. The primary conclusion of the test effort was that the 12kW string operated nominally and that the PPU and XFC could operate the thruster within specifications.

Electric propulsion↗
NASA NTRS1979

Grooves on Phobos - Their distribution, morphology and possible origin

The global distribution, morphology, age, possible origin and significance of the long, linear depressions termed grooves on the surface of Phobos are discussed, based on Viking Orbiter data. The grooves, which consist of linear strings of coalesced and separate depressions in a loose regolith up to 100-200 m in depth, are observed to define the intersection of several sets of parallel planes with the surface of Phobos, with the widest and deepest grooves occurring just outside the rim of the 10-km crater, Stickney. The superposition of the grooves on older craters, crater density within the grooves and the intersections of groove sets suggest that the grooves are all of the same age, with their formation closely following that of Stickney. The evidence of groove morphology and distribution is used to attribute their formation to the enlargement of preexisting fractures or the formation of new fractures by the Stickney impact, causing the mobilization of the regolith along the fractures. The lack of observable grooves on Deimos is explained by the absence of a crater large enough to have severly fractured its surface.

Thomas, P.↗
DOE OSTI2023

Potential induced degradation in c-Si glass-glass modules after extended damp heat stress

Traditional Glass-Backsheet (GB) photovoltaic (PV) modules have been the industry standard for a long time, but the Glass-Glass (GG) modules are quickly rising in popularity. PV modules installed in hot-humid climates with high string voltages can undergo potential induced degradation (PID). So far, to the best of our knowledge, only fresh modules with strong interfacial adhesion have been investigated for PID. However, in reality, the PV modules have weak interfacial adhesion after a few years of field exposure. Therefore, it is essential to evaluate PV modules with weakened interfaces. In this study, we investigated the PID susceptibility of PV modules with weakened interfaces after subjecting them to 2000 hours of damp heat (DH2000) at 85°C/85% relative humidity (RH) in an accelerated environmental chamber. Fresh GG modules were also stressed for PID to compare with PID degradation of DH-stressed modules. Pre- and post-characterization tests were done before, between, and after each stress method to determine the changes in electrical performance, cell metallization properties, and hotspot properties. It is observed that fresh GG modules showed little/no degradation (less than 1%) in maximum power (Pmax), whereas the GG modules that underwent sequential DH and PID degraded by 11% to 12%. Potential mechanisms for these degradations are also presented. Furthermore, the results presented in this study are critical for the industry, considering that the bifacial modules with GG construction will be dominant in the next 10 years.

14 SOLAR ENERGY↗
NASA NTRS1984

Investigation of test methods, material properties, and processes for solar cell encapsulants

Photovoltaic (PV) modules consist of a string of electrically interconnected silicon solar cells capable of producing practical quantities of electrical power when exposed to sunlight. To insure high reliability and long term performance, the functional components of the solar cell module must be adequately protected from the environment by some encapsulation technique. The encapsulation system must provide mechanical support for the cells and corrosion protection for the electrical components. The goal of the program is to identify and develop encapsulation systems consistent with the PV module operating requirements of 30 year life and a target cost of $0.70 per peak watt ($70 per square meter) (1980 dollars). Assuming a module efficiency of ten percent, which is equivalent to a power output of 100 watts per square meter in midday sunlight, the capital cost of the modules may be calculated to be $70.00 per square meter. Out of this cost goal, only 20 percent is available for encapsulation due to the high cost of the cells, interconnects, and other related components. The encapsulation cost allocation may then be stated as $14.00 per square meter, included all coatings, pottant and mechanical supports for the cells.

Source record↗
NASA NTRS2013

Moduli Dark Matter and the Search for Its Decay Line using Suzaku X-Ray Telescope

Light scalar fields called moduli arise from a variety of different models involving supersymmetry and/or string theory; thus their existence is a generic prediction of leading theories for physics beyond the standard model. They also present a formidable, long-standing problem for cosmology. We argue that an anthropic solution to the moduli problem exists in the case of small moduli masses and that it automatically leads to dark matter in the form of moduli. The recent discovery of the 125 GeV Higgs boson implies a lower bound on the moduli mass of about a keV. This form of dark matter is consistent with the observed properties of structure formation, and it is amenable to detection with the help of x-ray telescopes. We present the results of a search for such dark matter particles using spectra extracted from the first deep x-ray observations of the Draco and Ursa Minor dwarf spheroidal galaxies, which are darkmatter- dominated systems with extreme mass-to-light ratios and low intrinsic backgrounds. No emission line is positively detected, and we set new constraints on the relevant new physics.

Kusenko, Alexander↗
NASA NTRS1989

Lunar drill footplate and casing

To prevent hole collapse during lunar drilling operations, a casing has been devised of a graphite reinforced polyimide composite which will be able to withstand the lunar environment. Additionally, this casing will be inserted into the ground in segments two meters long which will penetrate the regolith simultaneously with the auger. The vertical action of the mobile platform will provide a downward force to the casing string through a special adaptor, giving the casing the needed impetus to sink the anticipated depth of ten meters. Casing segments will be connected with a simple snap arrangement. Excess casing will be cut off by a cylindrical cutting tool which will also transport the excess casing away from the hole. A footplate will be incorporated to grasp the auger rod string during rod segment additions or removals. The footplate grasping mechanism will consist of a set of vice-like arms, one end of each bearing threaded to a common power screw. The power screw will be threaded such that one end's thread pitch opposes that of the other end. The weight of the auger and rod string will be transmitted through the arms to the power screw and absorbed by a set of three ball bearing assemblies. The power screw will be driven by a one-half horsepower brushless motor actuated by radio control. The footplate will rest on four short legs and be anchored with pins that are an integral part of each leg.

Maassen, Erik C.↗