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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 109 records · Page 6
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NASA NTRS2008

NASA's THEMIS Mission: Multipoint Observations of Substorms, the Foreshock, and the Magnetopause

From launch on February 17 through the repositioning to final orbits that began in September 2007, the five-spacecraft of the THEMIS mission operated nominally in nearly identical 14.6 RE apogee near-equatorial orbits. On March 23, while aligned from east to west in the duskside magnetotail, the spacecraft observed two substorm sequences in fast survey mode. Timing the motion of these signatures served as an early proof of concept for the main phase of the mission: particle injection and dipolarization signatures propagated duskward from one probe to another, as did auroral intensifications seen by the dedicated array of ground-based observatories. During the summer of 2007, the spacecraft were on the dayside, where the three inner spacecraft (C, D, E) were separated by 100-500 km and the two outer probes (B, -4) by 5,000 - 10,000 km. Here the THEMIS probes repeatedly encountered the magnetopause and bow shock, dissecting flux transfer events (FTEs), determining the instantaneous width of the low-latitude boundary layer, and simultaneously observing hot flow anomalies upstream and downstream from the bow shock at the moment of their inception. From January to March 2008, the spacecraft were in the Earths magnetotail with apogees of 31.0, 19.5, 11.8 (2) and 10.0 RE corresponding to periods of 4, 2, and 1 days. Radial alignments once each four days offered an opportunity to pinpoint when and where substorms begin. This talk reviews THEMIS discoveries to date, with an emphasis on model-data comparisons of FTE characteristics

Sibeck, D. G.↗
NASA NTRS1976

Considerations to achieve directionality for gamma ray lasers

A method of alignment of nuclei for a gamma ray laser and a means of achieving preferential emission of radiation along the crystal axis are discussed. The proposed method of preferential emission of radiation along the aligned needles is to have a symmetric field gradient at the nucleus and a sequence of excited levels of spin and parity 2(+) and C(+). The proposed scheme reduces the density of excited states required for lasing and reduces the linewidth due to inhomogeneous broadening. Mossbauer absorption experiments intended to test these ideas are outlined.

Jha, S.↗
NASA NTRS1976

Considerations to achieve directionality for gamma ray lasers

A method of alignment of nuclei for a gamma ray laser and a means of achieving preferential emission of radiation along the crystal axis are studied. Atomic alignment was achieved by materials researchers who made composite structures composed of needle-like single crystals all with the same orientation and all pointing in the same direction contained in a matrix of cobalt or nickel. The proposed method of preferential emission of radiation along the aligned needles is to have a symmetric field gradient at the nucleus and a sequence of excited levels of spin and parity 2(+) and 0(+). The proposed scheme reduces the density of excited states required for lasing and reduces the linewidth due to inhomogenous broadening. Mossbauer absorption experiments intended to test these ideas are outlined.

Jha, S.↗
NASA NTRS1974

Second heated jettison test on the Centaur standard shroud

The second in a planned series of heated jettison tests on the Centaur Standard Shroud was conducted on January 16, 1974. The first 250-second portion of the test sequence involved heating the shroud with a specially-built fixture designed to provide a simulation of the heating environment encountered by the shroud during its ascent through the earth's atmosphere. The two heater halves, which were mounted on a rail system, were then retracted. This was followed by the jettison of the two shroud halves into catch nets positioned at 90 deg to the heater rails. The condition which made this test unique compared to the others in the test series was the alignment of the maximum thermal line with the shroud separation plane. Information on the test hardware, configuration, and sequence is presented. Shroud thermal and deflection data encountered during the heating portion of the test sequence are compared with free-skin design temperatures in various graphical formats.

Source record↗
NASA NTRS2018

Image Station Matching, Preprocessing, Spatial Registration and Change Detection with Multi-Temporal Remotely-Sensed Imagery

A method for collecting and processing remotely sensed imagery in order to achieve precise spatial co-registration (e.g., matched alignment) between multi-temporal image sets is presented. Such precise alignment or spatial co-registration of imagery can be used for change detection, image fusion, and temporal analysis/modeling. Further, images collected in this manner may be further processed in such a way that image frames or line arrays from corresponding photo stations are matched, co-aligned and if desired merged into a single image and/or subjected to the same processing sequence. A second methodology for automated detection of moving objects within a scene using a time series of remotely sensed imagery is also presented. Specialized image collection and preprocessing procedures are utilized to obtain precise spatial co-registration (image registration) between multitemporal image frame sets. In addition, specialized change detection techniques are employed in order to automate the detection of moving objects.

Coulter, Lloyd Lawrence Arthur↗
NASA NTRS2018

New Science in Plain Sight: Citizen Scientists Lead to the Discovery of Optical Structure in the Upper Atmosphere

A glowing ribbon of purple light running east-west in the night sky has recently been observed by citizen scientists. This narrow, subauroral, visible structure, distinct from the traditional auroral oval, was largely undocumented in the scientific literature and little was known about its formation. Amateur photo sequences showed colors distinctly different from common types of aurora and occasionally indicated magnetic field aligned substructures. Observations from the Swarm satellite as it crossed the arc have revealed an unusual level of electron temperature enhancement and density depletion, along with a strong westward ion flow, indicating that a pronounced subauroral ion drift (SAID) is associated with this structure. These early results suggest the arc is an optical manifestation of SAID, presenting new opportunities for investigation of the dynamic SAID signatures from the ground. On the basis of the measured ion properties and original citizen science name, we propose to identify this arc as a Strong Thermal Emission Velocity Enhancement (STEVE).

MacDonald, Elizabeth A.↗
NASA NTRS2013

Development of the Orion Crew-Service Module Umbilical Retention and Release Mechanism

The Orion CSM umbilical retention and release mechanism supports and protects all of the cross-module commodities between the spacecrafts crew and service modules. These commodities include explosive transfer lines, wiring for power and data, and flexible hoses for ground purge and life support systems. The mechanism employs a single separation interface which is retained with pyrotechnically actuated separation bolts and supports roughly two dozen electrical and fluid connectors. When module separation is commanded, either for nominal on-orbit CONOPS or in the event of an abort, the mechanism must release the separation interface and sever all commodity connections within milliseconds of command receipt. There are a number of unique and novel aspects of the design solution developed by the Orion mechanisms team. The design is highly modular and can easily be adapted to other vehiclesmodules and alternate commodity sets. It will be flight tested during Orions Exploration Flight Test 1 (EFT-1) in 2014, and the Orion team anticipates reuse of the design for all future missions. The design packages fluid, electrical, and ordnance disconnects in a single separation interface. It supports abort separations even in cases where aerodynamic loading prevents the deployment of the umbilical arm. Unlike the Apollo CSM umbilical which was a destructive separation device, the Orion design is resettable and flight units can be tested for separation performance prior to flight.Initial development testing of the mechanisms separation interface resulted in binding failures due to connector misalignments. The separation interface was redesigned with a robust linear guide system, and the connector separation and boom deployment were separated into two discretely sequenced events. These changes addressed the root cause of the binding failure by providing better control of connector alignment. The new design was tuned and validated analytically via Monte Carlo simulation. The analytical validation was followed by a repeat of the initial test suite plus test cases at thermal extremes and test cases with imposed mechanical failures demonstrating fault tolerance. The mechanism was then exposed to the qualification vibration environment. Finally, separation testing was performed at full speed with live ordnance.All tests of the redesigned mechanism resulted in successful separation of the umbilical interface with adequate force margins and timing. The test data showed good agreement with the predictions of the Monte Carlo simulation. The simulation proved invaluable due to the number of variables affecting the separation and the uncertainty associated with each. The simulation allowed for rapid assessment of numerous trades and contingency scenarios, and can be easily reconfigured for varying commodity sets and connector layouts.

Separation↗
NASA NTRS2007

TRL-6 for JWST Wavefront Sensing and Control

NASA's Technology Readiness Level (TRL)-6 is documented for the James Webb Space Telescope (JWST) Wavefront Sensing and Control (WFSC) subsystem. The WFSC subsystem is needed to align the Optical Telescope Element (OTE) after all deployments have occurred, and achieves that requirement through a robust commissioning sequence consisting of unique commissioning algorithms, all of which are part of the WFSC algorithm suite. This paper identifies the technology need, algorithm heritage, describes the finished TRL-6 design platform, and summarizes the TRL-6 test results and compliance. Additionally, the performance requirements needed to satisfy JWST science goals as well as the criterion that relate to the TRL-6 Testbed Telescope (TBT) performance requirements are discussed

Feinberg, Lee↗
NASA NTRSDate not supplied

Benchmarking Computational Tools for Calling SNPs and Indels in Complex Microbial Populations

The NASA BioNutrients missions seek to understand the suitability of microorganisms for bioproduction during space flight. One topic of interest is the stability of microbial genomes during long-term ambient storage and subsequent rehydration and growth. To address these questions, samples from 8 species were flown to ISS for 5 years of desiccated storage at ambient temperature (Stasis Packs) and 2 species were packaged along with powdered media inside a bioreactor system to allow hydration and growth in microgravity (Production Packs). For both systems, Whole Genome Sequencing (WGS) of the DNA extracted from the returned samples and paired ground controls will be conducted to identify changes in genome stability due to time, storage conditions and growth in space. Across the technical replicates, ground controls, 10 timepoints, and multiple experimental conditions, ~300 samples have been selected for initial analysis with WGS sequencing to 100x coverage. A flexible and resource efficient mutation calling pipeline is needed to process this large dataset and allow for comparisons between species. Many bioinformatics tools for calling Indels and Single Nucleotide Variants (SNVs) are designed for use with pure isolates, where true variations from the reference genome are expected to dominate the reads aligning to the location of mutation. In contrast, DNA from the Stasis Pack (SP) samples was collected directly after recovery from desiccated storage and the Production Pack (PP) samples were collected after fermentation. In this context, reads with mutations are expected to be less frequent than reads that align with the reference genome, as each sample will include multiple lines of cells. Thus, BioNutrients samples are expected to be similar to samples from cancer cell or “pooled” sequencing approaches. In preparation for the analysis of the BioNutrients samples, we have tested three mutation calling tools (GATK for Microbes, BreSeq and DiscoSNP) designed for complex samples. A challenge of validating mutation identification pipelines is a lack of “Ground Truth” datasets, especially for complex samples. To compare these three tools, we sought to identify mutations in pre-existing WGS data collected from populations of Chlamydomonas reinhardtii that were exposed to UV mutagenesis and growth in LEO as part of the Space Algae-1 mission. Here we present a summary of these tools against the analysis originally conducted using the CRISP tool. Critical metrics are compared such as runtime, the number of SNPs, the number and size of Indels, and patterns of transversion and transitions identified by each tool are reported. By sharing these benchmarking results collected in support of the BioNutrients mission, we aim to guide others seeking to identify SNVs in similarly complex microbial samples.

Biology↗
NASA NTRS2000

Processing Motion Signals in Complex Environments

Motion information is critical for human locomotion and scene segmentation. Currently we have excellent neurophysiological models that are able to predict human detection and discrimination of local signals. Local motion signals are insufficient by themselves to guide human locomotion and to provide information about depth, object boundaries and surface structure. My research is aimed at understanding the mechanisms underlying the combination of motion signals across space and time. A target moving on an extended trajectory amidst noise dots in Brownian motion is much more detectable than the sum of signals generated by independent motion energy units responding to the trajectory segments. This result suggests that facilitation occurs between motion units tuned to similar directions, lying along the trajectory path. We investigated whether the interaction between local motion units along the motion direction is mediated by contrast. One possibility is that contrast-driven signals from motion units early in the trajectory sequence are added to signals in subsequent units. If this were the case, then units later in the sequence would have a larger signal than those earlier in the sequence. To test this possibility, we compared contrast discrimination thresholds for the first and third patches of a triplet of sequentially presented Gabor patches, aligned along the motion direction. According to this simple additive model, contrast increment thresholds for the third patch should be higher than thresholds for the first patch.The lack of a measurable effect on contrast thresholds for these various manipulations suggests that the pooling of signals along a trajectory is not mediated by contrast-driven signals. Instead, these results are consistent with models that propose that the facilitation of trajectory signals is achieved by a second-level network that chooses the strongest local motion signals and combines them if they occur in a spatio-temporal sequence consistent with a trajectory. These results parallel the lack of increased apparent contrast along a static contour made up of similarly oriented elements.

Verghese, Preeti↗
NASA NTRS1982

Interplanetary magnetic field control of high-latitude activity on July 29, 1977

Multisatellite particle and magnetic field data for the substorms of July 29, 1977, show auroral-like activity above 80 deg invariant latitude during the recovery period. The movement of auroral zone activity to high latitudes followed the substorm sequence, at which time the inferred interplanetary magnetic field (IMF) was strongly northward. Electron energy spectra indicative of a field-aligned potential drop, and the absence of supporting precipitating ions, are found at latitudes greater than 80 deg. The north-south symmetry of these observations suggests that the events are on closed field lines. It is noted the very strong northward IMF connected to the sunward tilted geomagnetic dipole field plays a role in the driving of strong Birkeland and ionospheric current systems in the northern polar regions, while eliminating them from the southern polar regions.

Zanetti, L. J.↗
NASA NTRS1986

Mesoscale waves as a probe of Jupiter's deep atmosphere

Images from the Voyager north/south mapping sequences were searched for waves. A remarkable class of mesoscale waves was identified, with the following features: (1) the wavetrains are usually aligned zonally, i.e., wavecrests are north-south; (2) the average wavelength is 300 km with a standard deviation of only 20%; (3) the wavetrains are long; (4) the waves occur within 25 degrees of the equator, the bulk being at the equator itself; (5) the waves are centered at the extrema (in latitude) of the zonal flow; and (6) the meridional extent of the waves is typically 1 degree of latitude. These observations are interpreted as evidence of gravity waves propagating vertically within a leaky duct. A three-level model is assumed composed of a stable duct which extends up to the base of the NH3 cloud deck near 600 mb. Above this is a thin wave-trapping region characterized by a Richardson number Ri less than 1/4 and containing a critical level, where the local value of the zonal flow velocity equals the phase speed of the wave. This in turn is overlain by a stable region, representing the tropopause region and stratosphere.

Flaser, F. M.↗
NASA NTRS2003

Effects of Two-Pulse Sequencing on Characteristics of Elementary Propellants for Ablative Laser Propulsion

This work continues on previous investigations of elementary propellants for Ablative Laser Propulsion (ALP). This paper details the experimental methods used for alignment of a non-colinear temporal pulse splitting apparatus. Spatial coincidence of the separate pulses is established, the pulses are delayed, and first data is reported on this pulse spacing effect on time-of-fight (TOF) measurements. This includes ion velocity and number density measurements, and this data is compared to results from a previous work. Also, first data on the experimental determination of the time required for the laser-induced plasma to become purely reflective to incident pulses is presented.

Thompson, M. Shane↗
NASA NTRS2000

A Tool for Automatic Data Distribution for CFD Applications on Structured Grids

Development of HPF versions of NPB and ARC3D has shown that HPF provides an efficient, concise way to express parallelism and to organize data traffic. The use of HPF, as noted in the papers, requires an intimate knowledge of the applications and a detailed analysis of data affinity, data movement, and data granularity. To simplify and accelerate the task of developing HPF versions of existing CFD applications we have designed and implemented ADAPT (Automatic Data Alignment and Placement Tool). ADAPT analyzes a CFD application working on a single structured grid and generates HPF TEMPLATE, (RE)DISTRIBUTION, ALIGNMENT, and INDEPENDENT directives. The directives can be generated on the nest level, subroutine level, application level, or on the application interface level. ADAPT annotates an existing CFD FORTRAN application, performing computations on single or multiple grids. On each grid the application is considered as a sequence of operators, each applied to a set of variables defined in a particular grid domain. ADAPT automatically detects implicit operators (i.e., having data dependences) and explicit operators (without data dependences). For parallelization of an explicit operator ADAPT creates a template for the operator domain, aligns arrays used in the operator with the template, distributes the template, and declares the loops over the distributed dimensions as INDEPENDENT. For parallelization of an implicit operator, the distribution of the operator's domain should be consistent with the operator's dependences. Any dependence between sections distributed on different processors would preclude parallelization if the compiler does not have an ability to pipeline computations. If a data distribution is "orthogonal" to the dependences of an implicit operator, then the loop which implements the operator can be declared as INDEPENDENT. ADAPT starts with an analysis of array index expressions of the loop nests. For each pair of arrays referenced in an assignment statement, it generates an arc in the alignment graph and annotates it with an affinity relation. The template, alignment, and distribution directives for a particular loop nest are then derived from a transitive closure of the affinity relation. A compromise of data distributions in different nests and subroutines is achieved by merging annotated alignment graphs for adjacent nests/stibroutine calls in the nest/call graph of the application in the process called distribution lifting. ADAPT has been implemented as a C++ program running in conjunction with a parallelization tool called CAPTools. ADAPT uses the parse tree, interprocedural analysis and application database generated by CAPTools. It also uses the Directed Graph class, initially implemented in p2d2 (parallel debugger oi distributed programs), and some other classes supporting symbolic computations. ADAPT uses data distribution techniques described. ADAPT was tested with ARC3D and the FT benchmark and has demonstrated a code performance within a factor of 1.5 of handwritten versions.

Frumkin, Michael↗
NASA NTRS2007

CEV Trajectory Design Considerations for Lunar Missions

The Crew Exploration Vehicle (CEV) translational maneuver Delta-V budget must support both the successful completion of a nominal lunar mission and an "anytime" emergency crew return with the potential for much more demanding orbital maneuvers. This translational Delta-V budget accounts for Earth-based LEO rendezvous with the lunar surface access module (LSAM)/Earth departure stage (EDS) stack, orbit maintenance during the lunar surface stay, an on-orbit plane change to align the CEV orbit for an in-plane LSAM ascent, and the Moon-to-Earth trans-Earth injection (TEI) maneuver sequence as well as post-TEI TCMs. Additionally, the CEV will have to execute TEI maneuver sequences while observing Earth atmospheric entry interface objectives for lunar high-latitude to equatorial sortie missions as well as near-polar sortie and long duration missions. The combination of these objectives places a premium on appropriately designed trajectories both to and from the Moon to accurately size the translational V and associated propellant mass in the CEV reference configuration and to demonstrate the feasibility of anytime Earth return for all lunar missions. This report examines the design of the primary CEV translational maneuvers (or maneuver sequences) including associated mission design philosophy, associated assumptions, and methodology for lunar sortie missions with up to a 7-day surface stay and with global lunar landing site access as well as for long duration (outpost) missions with up to a 210-day surface stay at or near the polar regions. The analyses presented in this report supports the Constellation Program and CEV project requirement for nominal and anytime abort (early return) by providing for minimum wedge angles, lunar orbit maintenance maneuvers, phasing orbit inclination changes, and lunar departure maneuvers for a CEV supporting an LSAM launch and subsequent CEV TEI to Earth return, anytime during the lunar surface stay.

Condon, Gerald L.↗
NASA NTRS1988

Geology and geochemistry of the Middle Proterozoic Eastern Ghat mobile belt and its comparison with the lower crust of the Southern Peninsular shield

Two prominent rock suites constitute the lithology of the Eastern Ghat mobile belt: (1) the khondalite suite - the metapelites, and (2) the charnockite suite. Later intrusives include ultramafic sequences, anorthosites and granitic gneisses. The chief structural element in the rocks of the Eastern Ghats is a planar fabric (gneissosity), defined by the alignment of platy minerals like flattened quartz, garnet, sillimanite, graphite, etc. The parallelism between the foliation and the lithological layering is related to isoclinal folding. The major structural trend (axial plane foliation trend) observed in the belt is NE-SW. Five major tectonic events have been delineated in the belt. A boundary fault along the western margin of the Eastern Ghats, bordering the low grade terrain has been substantiated by recent gravity and the deep seismic sounding studies. Field evidence shows that the pyroxene granulites (basic granulites) post-date the khondalite suite, but are older than the charnockites as well as the granitic gneisses. Polyphase metamorphism, probably correlatable with different periods of deformation is recorded. The field relations in the Eastern Ghats point to the intense deformation of the terrain, apparently both before, during and after metamorphism.

Rao, M. V. Subba↗
NASA NTRS1999

Automatic Data Distribution for CFD Applications on Structured Grids

Development of HPF versions of NPB and ARC3D showed that HPF has potential to be a high level language for parallelization of CFD applications. The use of HPF requires an intimate knowledge of the applications and a detailed analysis of data affinity, data movement and data granularity. Since HPF hides data movement from the user even with this knowledge it is easy to overlook pieces of the code causing low performance of the application. In order to simplify and accelerate the task of developing HPF versions of existing CFD applications we have designed and partially implemented ADAPT (Automatic Data Distribution and Placement Tool). The ADAPT analyzes a CFD application working on a single structured grid and generates HPF TEMPLATE, (RE)DISTRIBUTION, ALIGNMENT and INDEPENDENT directives. The directives can be generated on the nest level, subroutine level, application level or inter application level. ADAPT is designed to annotate existing CFD FORTRAN application performing computations on single or multiple grids. On each grid the application can considered as a sequence of operators each applied to a set of variables defined in a particular grid domain. The operators can be classified as implicit, having data dependences, and explicit, without data dependences. In order to parallelize an explicit operator it is sufficient to create a template for the domain of the operator, align arrays used in the operator with the template, distribute the template, and declare the loops over the distributed dimensions as INDEPENDENT. In order to parallelize an implicit operator, the distribution of the operator's domain should be consistent with the operator's dependences. Any dependence between sections distributed on different processors would preclude parallelization if compiler does not have an ability to pipeline computations. If a data distribution is "orthogonal" to the dependences of an implicit operator then the loop which implements the operator can be declared as INDEPENDENT.

Frumkin, Michael↗
NASA NTRS1989

Chip Advancer For GPS Receiver

Instrument errors made negligible. For each integration interval, both delay and rate of change of delay initialized to small fraction of chip - for example, to order of 10 to the negative 7th power - thereby making feedback control and extraction of delay highly accurate and flexible. With appropriate selection of sampling rate relative to chip rate, commensurability errors reduced to extremely small levels. In Global Positioning System (GPS) receiver, pseudorandom code sequence generated by simple digital logic incorporating effects of time, delay, and rate of change of delay. Flexibility in starting time and sum interval very useful in aligning correlation interval with beginnings and endings of data bits.

Meehan, Thomas K.↗