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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Comparison of very-low-frequency auroral hiss with precipitating low-energy electrons by the use of simultaneous data from two Ogo 4 experiments.

Determination of the origin of auroral hiss by comparing the records of a vlf experiment (0.3 to 18 kHz) with simultaneous data obtained by an auroral-particle experiment having detectors for precipitating electrons at 0.7, 2.3, and 7.3 keV. It is found that, on the dayside of the earth, the occurrence of vlf hiss correlates well with precipitation events at 0.7 keV, but in general very poorly with activity in the higher-energy channels. Exact correlation between variations in vlf hiss intensity and in electron fluxes is rare even at 0.7 keV. In addition, vlf hiss tends to be observed over a somewhat larger spatial region than precipitating 0.7-keV electrons. It is concluded that, on the dayside, auroral hiss is generated by soft (E less than 1 keV) 'cusp region' electrons and that the lack of detailed correlation between the two phenomena is caused by propagation effects as the hiss travels downward and spreads from the generation region.

Hoffman, R. A.↗
NASA NTRS1994

Discovery of intense gamma-ray flashes of atmospheric origin

Observations have been made of a new terrestrial phenomenon: brief (approx. millisecond), intense flashes of gamma rays, observed with space-borne detectors. These flashes must originate at altitudes in the atmosphere above at least 30 km in order to be observable by orbiting detectors aboard the Compton Gamma-Ray Observatory (CGRO). At least a dozen events have been detected over the past 2 years. The photon spectra from the events are very hard and are consistent with bremsstrahlung emission from energetic (MeV) electrons. The most likely origin of these high energy electrons, while speculative at this time, is a rare type of high altitude electrical discharge above thunderstorm regions.

Fishman, G. J.↗
NASA NTRS2022

The Dynamic Atmospheric and Aeolian Environment of Jezero Crater, Mars

Despite the importance of sand and dust to Mars geomorphology, weather, and exploration, the processes that move sand and that raise dust to maintain Mars’s ubiquitous dust haze have not been well quantified in situ, with missions lacking either thenecessary sensors and/or a sufficiently active aeolian environment. Perseverance rover’s novel environmental sensors and Jezero crater’s dusty environment remedy this. In Perseverance’s first 216 sols, four convective vortices raised dust locally, while on average four passed the rover daily, over 25% of which were significantly dusty (‘dust devils’). More rarely, dust lifting by non-vortex wind gusts was produced by daytime convection cells advected over the crater by strong upslope winds, which also control aeolian surface features. One such event covered ten times more area than the largest dust devil, suggesting dust devils and wind gusts could raise equal dust.

Claire E Newman↗
NASA NTRS2024

The Potassium Isotope Composition of Aggregate Material From Asteroid Bennu

NASA’s OSIRIS-REx mission re-turned material from asteroid Bennu on September 24, 2023, marking the first time a U.S. mission has delivered asteroid samples to Earth, and the largest asteroid sample return to date. Due to the pristine nature of these primitive carbonaceous-rich samples, they allow us a rare opportunity to study our solar system’s formation to a degree not previously possible. Isotopes of moderately volatile elements (MVEs) have been recently developed as robust tracers for tracking different volatilization events within our Solar System. Of the MVEs, K has gained significant interest in recent years due to its ideal chemical and physical properties combined with technique improvements. Due to this, several recent studies have investigated the K isotope systematics within bulk chondrites and found an isotopic dichotomy be-tween the carbonaceous and non-carbonaceous chondrites (Figure 1), likely reflecting their different reservoirs which formed in the inner and outer protoplanetary disk respectively. Furthermore, systematic K isotope variations across the different carbonaceous chondrite groups and correlations with mass independent isotope systems such as Cr, Ti, and Ni, have also been observed. As a result, establishing the K isotope composition of bulk Bennu can be used to test the mission hypothesis that “Bennu’s parent asteroid accreted in the outer protoplanetary disk, beyond Jupiter, as recorded by distinct isotopic anomalies in a variety of elements” . In addition to early solar system processes, K isotopes can also be fractionated by space weathering as shown by comparisons between mature and immature lunar regolith. The degree of K isotope fractionation caused by space weathering correlates with the regolith maturity index and is an order of magnitude larger than what is observed in bulk meteorite samples which have not undergone strong space weathering processes. As such, the K isotope systematics of Bennu samples could provide an independent assessment of regolith maturity of the asteroid surface, helping to directly test the mission hypothesis that “Space weathering changed the chemistry and mineralogy of optically active surfaces” . In order to test both this hypothesis, and the hypothesis relating to Bennu’s accretion location, we aim to conduct high-precision K isotope analysis on bulk Bennu aggregates.

K Wang↗
NASA NTRS1980

Micropulsations in the electric field near the plasmapause, observed by Isee 1

The results of a survey of occurrence of micropulsations near and inside the plasmapause, made on the basis of 1 year of data from the double probe electric field instrument on Isee 1, are presented. It is reported that the observed pulsations are classified as Pc 3 and P 2, and that one single Pc 1 event is observed. It is found that Pc 3 events are common during the local day, with a maximum percentage of occurrence as high as 72 in the morning hours. Attention is given to Pi 2 events showing that they are concentrated on the local nightside. Finally, it is noted that pulsations in the Pc 1 range appear on only one inbound pass, which makes the Pc 1 a rare phenomenon at low and moderate latitudes in the plasmasphere.

Moe, T. E.↗
NASA NTRS2020

Keck Observations Confirm a Super-Jupiter Planet Orbiting M Dwarf OGLE-2005 BLG-071L

We present adaptive optics imaging from the NIRC2 instrument on the Keck II telescope that resolves the exoplanet host (and lens) star as it separates from the brighter source star. These observations yield the K-band brightness of the lens and planetary host star, as well as the lens-source relative proper motion, μ(rel,H), in the heliocentric reference frame. The μ(rel,H) measurement allows for the determination of the microlensing parallax vector, π(E), which had only a single component determined by the microlensing light curve. The combined measurements of μ(rel,H) and K(L) provide the masses of the host star, M(host) = 0.426 ± 0.037M(ʘ), and planet, m(p)=3.27±0.32M(Jupiter) with a projected separation of 3.4±0.5 au. This confirms the tentative conclusion of a previous paper that this super-Jupiter mass planet, OGLE-2005-BLG-071Lb, orbits an M dwarf. Such planets are predicted to be rare by the core accretion theory and have been difficult to find with other methods, but there are two such planets with firm mass measurements from microlensing, and an additional 11 planetary microlens events with host mass estimates <0.5M(ʘ) and planet mass estimates >2 Jupiter masses that could be confirmed by high angular follow-up observations. We also point out that OGLE-2005-BLG-071L has separated far enough from its host star that it should be possible to measure the host-star metallicity with spectra from a high angular resolution telescope such as Keck, the Very Large Telescope, the Hubble Space Telescope, or the James Webb Space Telescope.

David P Bennett↗
NASA NTRS2009

Power Sources for Micro-Autonomous Vehicles- Challenges and Prospects

Micro-autonomous vehicle systems are expected to have expanded role in military missions by providing full spectrum intelligence, surveillance and reconnaissance support on the battlefield, suppression of enemy defenses, and enabling co-operative (swarm-like) configurations. Of the numerous demanding requirements of autonomy, sensing, navigation, mobility, etc., meeting the requirement of mission duration or endurance is a very challenging one. This requirement is demanding because of the constraints of mass and volume that limit the quantity of energy that can be stored on-board. Energy is required for mobility, payload operation, information processing, and communication. Mobility requirements typically place an extraordinary demand on the specific energy (Wh/kg) and specific power (W/kg) of the power source; the actual distribution of the energy between mobility and other system functions could vary substantially with the mission type. The power requirements for continuous mobility can vary from 100-1000 W/kg depending on the terrain, ground speed and flight speed. Even with the power source accounting for 30% of the mass of the vehicle, the best of rechargeable batteries can provide only up to 1-2 hours of run-time for a continuous power demand at 100W/kg. In the case of micro-aerial vehicles with flight speed requirements in the range of 5-15 m s-1, the mission times rarely exceed 20 minutes [2]. Further, the power required during take-off and hover can be twice or thrice that needed for steady level flight, and thus the number and sequence of such events is also limited by the mass and size of the power source. For operations such as "perch and stare" or "silent watch" the power demand is often only a tenth of that required during continuous flight. Thus, variation in power demand during various phases of the mission importantly affects the power source selection.

fuel cells↗
NASA NTRS2003

Prospecting for Martian Ice from Orbit

Recent data from the Gamma-Ray Spectrometer (GRS) on Mars Odyssey indicate the presence of a hydrogen-rich layer tens of centimeters thick in high latitudes on Mars. This hydrogen-rich layer correlates to previously determined regions of ice stability. It has been suggested that the subsurface hydrogen is ice and constitutes 35 plus or minus 15% by weight near the north and south polar regions. This study constrains the location of subsurface ice deposits on the scale of kilometers or smaller by combining GRS data with surface features indicative of subsurface ice. The most recognizable terrestrial geomorphic indicators of subsurface ice, formed in permafrost and periglacial environments, include thermokarst pits, pingos, pseudocraters and patterned ground. Patterned ground features have geometric forms such as circles, polygons, stripes and nets. This study focuses on the polygonal form of patterned ground, selected for its discernable shape and subsurface implications. Polygonal features are typically demarcated by troughs, beneath which grow vertical ice-wedges. Ice-wedges form in thermal contraction cracks in ice-rich soil and grow with annual freezing and thawing events repeated over tens of years. Ice wedges exist below the depth of seasonal freeze-thaw. Terrestrial ice wedges can be several meters deep and polygons can be tens of meters apart, and, on rare occasions, up to 1 km. The crack spacing of terrestrial polygons is typically 3 to 10 times the crack depth.

Kanner, L. C.↗
NASA NTRS1977

A new 1.3 Aeon-Young achondrite

The Ar-40/Ar-39 age of Governador Valadares, a Nakhlite achondrite, has been determined to be 1.32 plus or minus 0.04 billion yrs. The K-Ar age and cosmic-ray exposure age of Governador Valadares are essentially identical to analogous ages for the two other known Nakhlite achondrites and to Rb-Sr ages determined for Nakhla. These data suggest that all three known meteorites of this class were derived from the same parent body by a common event, and confirm that Governador Valadares is a member of this class. The most probable heat source for producing such meteorites may be collisional melting of a portion of the parent body. Nakhlites may represent a rare phenomenon and may not be at all representative of the surface of their parent body.

Bogard, D. D.↗
NASA NTRS2012

Mineralogical Studies of a Highly O-17-Depleted and an O-17-Rich Presolar Grain from the Acfer 094 Meteorite

Silicate grains are the most abundant condensate around O-rich evolved stars, including red giants, supernovae (SNe) and binary systems. These grains have been identified in abundance in primitive meteorites and interplanetary dust particles [1,2]. Astronomical observations of the silicate spectroscopic features around circumstellar disks indicate that most silicates are amorphous olivine-like grains, though some sources show a large crystalline portion [3]. Fewer astronomical observations of SN and nova silicates exist, but amorphous Mg-rich grains predominate [4,5]. The laboratory analysis of presolar silicates by transmission electron microscopy (TEM) offers more details on the structure and chemistry of individual grains. These studies provide information on the physical and chemical conditions of the parent stellar atmosphere during grain condensation. Moreover, be-cause silicates are susceptible to secondary alteration, processing events succeeding condensation can be traced. Thus far, similar microstructures have been observed for silicates that condensed in SN outflows and in the envelopes of asymptotic giant branch (AGB) stars, but not as many of the comparatively rare SN grains have been analyzed. Here we examine the mineralogies of two presolar silicate grains having different origins.

Nguyen, A. N.↗
NASA NTRS2014

STEREO as a "Planetary Hazards" Mission

NASA's twin STEREO probes, launched in 2006, have advanced the art and science of space weather forecasting more than any other spacecraft or solar observatory. By surrounding the Sun, they provide previously-impossible early warnings of threats approaching Earth as they develop on the solar far side. They have also revealed the 3D shape and inner structure of CMEs-massive solar storms that can trigger geomagnetic storms when they collide with Earth. This improves the ability of forecasters to anticipate the timing and severity of such events. Moreover, the unique capability of STEREO to track CMEs in three dimensions allows forecasters to make predictions for other planets, giving rise to the possibility of interplanetary space weather forecasting too. STEREO is one of those rare missions for which "planetary hazards" refers to more than one world. The STEREO probes also hold promise for the study of comets and potentially hazardous asteroids.

Heliosphere↗
NASA NTRS1987

Was the eclipse comet of 1893 a disconnected coronal transient?

The comet-like feature obsereved in the solar corona by the Lick Observatory eclipse expedition to Chile in 1893 bears an interesting resemblance to the disconnection coronal transient reported by Illing and Hundhausen. Reports of possibly-related limb activity are reviewed to see whether a pre-discovery observation of a relatively rare type of coronal mass ejection was mis-interpreted. The goal of this study is to learn more about the morphology of mass ejections by examining observations that extend down to the low corona of a disconnection event.

Cliver, E. W.↗
NASA NTRS2019

Unravelling Complex Geologic Histories Using U–Pb and Trace Element Systematics of Titanite

Unravelling the spatio-temporal evolution of orogenic terranes requires a comprehensive understanding of the duration and extent of metamorphic events and hydrothermal alteration. Commonly used minerals such as zircon and monazite may not fully record geological histories in complex tectonic settings because their elemental constituents do not react under many metamorphic and metasomatic conditions. Here, we complement the current geochronological record of the Capricorn Orogen, Western Australia, with titanite U–Pb geochronology and geochemistry of felsic intrusive rocks to draw conclusions about the use of titanite in understanding the evolution of orogenic terranes. Because titanite usually incorporates common-Pb and may be variably reset by multiple metamorphic and hydrothermal events, a workflow is provided here for the systematic and robust interpretation of titanite U-Pb data. The addition of trace element data in titanite is particularly effective for differentiating whether a grain is igneous, recrystallized or metamorphic. We have developed several petrogenetic indices to differentiate these three types of titanite using Zr-in-titanite temperature, Th/U, Th/Pb, Al/(Al + Fe), light to heavy rare earth element ratio, and Eu anomalies. The addition of trace element geochemistry can also highlight anomalously radiogenic (sup 207)Pb/(sup 206)Pb reservoirs. Utilization of our workflow in the Capricorn Orogen reveals that titanite ages from the same samples as published zircon U–Pb data range from coeval to several hundreds of Myr of age difference between the two minerals. Titanite geochronology and trace element geochemistry indicates ~20 Myr of previously unrecognized prolonged cooling for the Capricorn Orogeny to ca. 1750 Ma. The spatial extent of the ca. 1210–1170 Ma part of the Mutherbukin Tectonic Event is also broadened significantly farther north and south than previously recognized. Incorporating titanite geochronology and trace geochemistry with more commonly used techniques (e.g., zircon and monazite petrochronology) extends our ability to resolve the complete history of large-scale orogenic terranes.

Hugo K. H. Olierook↗
NASA NTRS1985

New aspects in nucleon-nucleus collisions and EAS properties around 10(6) GeV

At energies higher than 2 x 10 to the 5 GeV, very little information exists on detailed properties of nucleon-nucleon collision; the rare elements are coming from jets, and, as nondirect improvements from gamma-ray families. The results exhibit some conflicting features, or, at least, very large fluctuations like copious production of gamma-rays in opposition to Centauro-like events, sometimes suggest that phase transition to quark gluon plasma occurs in nucleus-nucleus collisions and even in nucleon-nucleus collision. The multicluster phenomenological model (MPM) extrapolated for extensive air showers EAS simulation up to 5 x 10 to the 6 GeV to put in evidence some significant deviation between experimental data and prediction.

Capdevielle, J. N.↗
NASA NTRS1992

On the relative importance of magnetospheric and ionospheric processes during substorm onset and expansion: A case study

The question of whether substorm onset is triggered in the magnetotail or the ionosphere is presented. The possible influence of the ionosphere in the subsequent development of a substorm is discussed. Theoretical considerations involved are reviewed and a case study to address this question is examined. The evidence indicates that magnetotail processes initiate the sequence of events called a substorm, while the ionosphere appears to play a critical role in the subsequent evolution of the substorm expansion phase. However, the necessary observations, in particular high time resolution coordinated observations in the ionosphere and magnetotail are relatively rare. Continued examination of existing ground and space based data sets, in particular underutilized observations such as the Scatha data, may provide a more solid foundation for clarifying this issue and determining the relative importance of magnetospheric and ionospheric processes during substorms.

Lopez, Ramon E.↗
NASA NTRS2010

Full Mission Astronaut Radiation Exposure Assessments for Long Duration Lunar Surface Missions

Risk to astronauts due to ionizing radiation exposure is a primary concern for missions beyond Low Earth Orbit (LEO) and will drive mission architecture requirements, mission timelines, and operational practices. Both galactic cosmic ray (GCR) and solar particle event (SPE) environments pose a risk to astronauts for missions beyond LEO. The GCR environment, which is made up of protons and heavier ions covering a broad energy spectrum, is ever present but varies in intensity with the solar cycle, while SPEs are sporadic events, consisting primarily of protons moving outward through the solar system from the sun. The GCR environment is more penetrating and is more difficult to shield than SPE environments, but lacks the intensity to induce acute effects. Large SPEs are rare, but they could result in a lethal dose, if adequate shielding is not provided. For short missions, radiation risk is dominated by the possibility of a large SPE. Longer missions also require planning for large SPEs; adequate shielding must be provided and operational constraints must allow astronauts to move quickly to shielded locations. The dominant risk for longer missions, however, is GCR exposure, which accumulates over time and can lead to late effects such as cancer. SPE exposure, even low level SPE exposure received in heavily shielded locations, will increase this risk. In addition to GCR and SPE environments, the lunar neutron albedo resulting mainly from the interaction of GCRs with regolith will also contribute to astronaut risk. Full mission exposure assessments were performed for proposed long duration lunar surface mission scenarios. In order to accomplish these assessments, radiation shielding models were developed for a proposed lunar habitat and rover. End-to-End mission exposure assessments were performed by first calculating exposure rates for locations in the habitat, rover, and during extra-vehicular activities (EVA). Subsequently, total mission exposures were evaluated for proposed timelines. A number of computational tools and mathematical models, which have been incorporated into NASA's On-Line Tool for the Assessment of Radiation In Space (OLTARIS), were used for this study. These tools include GCR and SPE environment models, human body models, and the HZETRN space radiation transport code, which is used to calculate the transport of the charged particles and neutrons through shielding materials and human tissue. Mission exposure results, assessed in terms of effective dose, are presented for proposed timelines and recommendations are made for improved astronaut shielding and safer operational practice.

Adamczyk, Anne M.↗
NASA NTRS2013

Corundum-Hibonite Inclusions and the Environments of High Temperature Processing in the Early Solar System

Calcium, Aluminum-rich inclusions (CAIs) are composed of the suite of minerals predicted to be the first to condense from a cooling gas of solar composition [1]. Yet, the first phase to condense, corundum, is rare in CAIs, having mostly reacted to form hibonite followed by other phases at lower temperatures. Many CAIs show evidence of complex post-formational histories, including condensation, evaporation, and melting [e.g. 2, 3]. However, the nature of these thermal events and the nebular environments in which they took place are poorly constrained. Some corundum and corundum-hibonite grains appear to have survived or avoided these complex CAI reprocessing events. Such ultra-refractory CAIs may provide a clearer record of the O isotopic composition of the Sun and the evolution of the O isotopic composition of the planet-forming region [4-6]. Here we present in situ O and Mg isotopic analyses of two corundum/hibonite inclusions that record differing formation histories.

Needham, A. W.↗
NASA NTRS2016

On the Importance of High Frequency Gravity Waves for Ice Nucleation in the Tropical Tropopause Layer

Recent investigations of the influence of atmospheric waves on ice nucleation in cirrus have identified a number of key processes and sensitivities: (1) ice concentrations produced by homogeneous freezing are strongly dependent on cooling rates, with gravity waves dominating upper tropospheric cooling rates; (2) rapid cooling driven by high-frequency waves are likely responsible for the rare occurrences of very high ice concentrations in cirrus; (3) sedimentation and entrainment tend to decrease ice concentrations as cirrus age; and (4) in some situations, changes in temperature tendency driven by high-frequency waves can quench ice nucleation events and limit ice concentrations. Here we use parcel-model simulations of ice nucleation driven by long-duration, constant-pressure balloon temperature time series, along with an extensive dataset of cold cirrus microphysical properties from the recent ATTREX high-altitude aircraft campaign, to statistically examine the importance of high-frequency waves as well as the consistency between our theoretical understanding of ice nucleation and observed ice concentrations. The parcel-model simulations indicate common occurrence of peak ice concentrations exceeding several hundred per liter. Sedimentation and entrainment would reduce ice concentrations as clouds age, but 1-D simulations using a wave parameterization (which underestimates rapid cooling events) still produce ice concentrations higher than indicated by observations. We find that quenching of nucleation events by high-frequency waves occurs infrequently and does not prevent occurrences of large ice concentrations in parcel simulations of homogeneous freezing. In fact, the high-frequency variability in the balloon temperature data is entirely responsible for production of these high ice concentrations in the simulations.

simulation↗