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At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Accelerometer method and apparatus for integral display and control functions

Vibration analysis has been used for years to provide a determination of the proper functioning of different types of machinery, including rotating machinery and rocket engines. A determination of a malfunction, if detected at a relatively early stage in its development, will allow changes in operating mode or a sequenced shutdown of the machinery prior to a total failure. Such preventative measures result in less extensive and/or less expensive repairs, and can also prevent a sometimes catastrophic failure of equipment. Standard vibration analyzers are generally rather complex, expensive, and of limited portability. They also usually result in displays and controls being located remotely from the machinery being monitored. Consequently, a need exists for improvements in accelerometer electronic display and control functions which are more suitable for operation directly on machines and which are not so expensive and complex. The invention includes methods and apparatus for detecting mechanical vibrations and outputting a signal in response thereto. The apparatus includes an accelerometer package having integral display and control functions. The accelerometer package is suitable for mounting upon the machinery to be monitored. Display circuitry provides signals to a bar graph display which may be used to monitor machine condition over a period of time. Control switches may be set which correspond to elements in the bar graph to provide an alert if vibration signals increase over the selected trip point. The circuitry is shock mounted within the accelerometer housing. The method provides for outputting a broadband analog accelerometer signal, integrating this signal to produce a velocity signal, integrating and calibrating the velocity signal before application to a display driver, and selecting a trip point at which a digitally compatible output signal is generated. The benefits of a vibration recording and monitoring system with controls and displays readily mountable on the machinery being monitored and having capabilities described will be appreciated by those working in the art.

Bozeman, Richard J., Jr.↗
NASA NTRS2009

Apollo Mission Techniques Lunar Orbit Activities - Part 1a

This slide presentation reviews the planned sequence of events and the rationale for all lunar missions, and the flight experiences and lessons learned for the lunar orbit activities from a trajectory perspective. Shown are trajectories which include the moon's position at the various stages in the complete trip from launch, to the return and reentry. Included in the presentation are objectives and the sequence of events,for the Apollo 8, and Apollo 10. This is followed by a discussion of Apollo 11, including: the primary mission objective, the sequence of events, and the flight experience. The next mission discussed was Apollo 12. It reviews the objectives, the ground tracking, procedure changes, and the sequence of events. The aborted Apollo 13 mission is reviewed, including the objectives, and the sequence of events. Brief summaries of the flight experiences for Apollo 14-16 are reviewed. The flight sequence of events of Apollo 17 are discussed. In summary each mission consistently performing precision landings required that Apollo lunar orbit activities devote considerable attention to: (1) Improving fidelity of lunar gravity models, (2) Maximizing availability of ground tracking, (3) Minimizing perturbations on the trajectory, (4) Maximizing LM propellant reserves for hover time. Also the use of radial separation maneuvers (1) allows passive re-rendezvous after each rev, but ... (2) sensitive to small dispersions in initial sep direction

Interbartolo, Michael A.↗
NASA NTRSDate not supplied

Mineralogy of the Greenheugh Pediment and Underlying Murray Formation from the Mars Science Laboratory CheMin Instrument

The Mars Science Laboratory Curiosity rover has been investigating a sequence of ancient fluvio-lacustrine and eolian units in Gale crater. For much of the mission, Curiosity has studied the fluvio-lacustrine deposits of the Murray formation. Curiosity has also studied the ancient eolian Stimson formation in a few locations, which unconformably overlies the Murray fm. The Stimson formation was previously studied at the Naukluft and Emerson Plateaus and recently studied at the Greenheugh pediment capping unit. The Curiosity science team also investigated the Murray formation directly underlying the pediment. Curiosity drilled the “Edinburgh” target within the pediment capping unit and the “Hutton” target in the Murray formation near the contact with the pediment and delivered these materials to the CheMin X-ray diffractometer to characterize bulk mineralogy. Edinburgh contains abundant plagioclase, pyroxene, magnetite, olivine, and X-ray amorphous materials, with 10 wt.% smectite and minor sanidine. The mineralogy of the Stimson at Greenheugh is distinct from the mineralogy of the Stimson at Naukluft and Emerson because previous Stimson targets did not contain olivine or clay minerals. This suggests sediments in the pediment may have a different source and/or different aqueous alteration history than those from Naukluft and Emerson. Hutton contains abundant plagioclase, pyroxene, magnetite, and X-ray amorphous materials, 6 wt.% smectite, and minor cristobalite, opal-CT, sanidine, hematite, fluorapatite, and anhydrite. Other Murray targets in the surrounding Glen Torridon region that are farther from the pediment contact contain ~30 wt.% smectite and lack cristobalite and opal-CT. Cristobalite and/or opal-CT are present in a few other targets elsewhere along the traverse, including the top of the nearby Vera Rubin ridge and the top of the Pahrump Hills outcrop. Stimson overlies the Pahrump Hills, and, based on projections of the pediment slope, the Stimson may have overlain Vera Rubin ridge. The proximity of the low-smectite and cristobalite- and/or opal-CT-bearing outcrops to the contact between the Murray and Stimson suggests the contact provided a conduit for diagenetic fluids that altered clay minerals and formed crystalline and paracrystalline silica.

E. B. Rampe↗
NASA NTRS1977

Accretion of rotating fluids by barytropes - Numerical results for white-dwarf models

Numerical sequences of rotating axisymmetric nonmagnetic equilibrium models are constructed which represent the evolution of a barytropic star as it accretes material from a rotating medium. Two accretion geometries are considered - one approximating accretion from a rotating cloud and the other, accretion from a Keplerian disk. It is assumed that some process, such as Ekman spin-up or nonequilibrium oscillations, maintains nearly constant angular velocity along cylinders about the rotation axis. Transport of angular momentum in the cylindrically radial direction by viscosity is included. Fluid instabilities and other physical processes leading to enhancement of this transport are discussed. Particular application is made to zero-temperature white-dwarf models, using the degenerate electron equation of state. An initially nonrotating 0.566-solar-mass white dwarf is followed during the accretion of more than one solar mass of material. Applications to degenerate stellar cores, to mass-transfer binary systems containing white dwarfs, such as novae and dwarf novae, to Type I supernovae, and to galactic X-ray sources are considered.

Durisen, R. H.↗
NASA NTRS1984

Quantification of waste morphology in Martian fretted terrain

Qualitative and quantitative analyses are performed on the northern fretted terrain of the Martian Isnenius Lacus quadrangle to determine the formation processes. The fretted terrain lies between 35-50 deg N latitude and 305-350 deg W longitude and was mapped with Viking orbiter instrumentation. The dominant landforms are a sequence of heavily cratered terrain, scattered flat-floored, fretted valleys, linear waste-covered valleys between flat-topped mesas, circum-mesa debris areas, a transition from mesas to knobby terrain, fewer upland forms, and low-relief, mantled, polar plains. The features spread out from a cratered terrain boundary in a succession of shapes. A principal components analysis characterizes definable spatial variations in the surface morphology and suggests that the features are youngest in the southwest direction. Relationships are also found between neighboring features. The principal components analysis technique is concluded to be a valuable tool for explaining the geomorphic evolution of the Martian surface.

Kochel, R. C.↗
NASA NTRS1994

Analysis of coseismic surface displacement gradients using radar interferometry: New insights into the Landers earthquake

The map of the coseismic displacement field generated by interferometric processing of synthetic aperture radar (SAR) images taken before and after the June 28, 1992, Landers earthquake sequence brings new insights into the nature of deformation caused by these earthquakes. We use the interferometric map generated by Massonnet et al. (1993) to analyze the surface displacement field in the vicinity of the fault trace. Complexities in the fringe pattern near the fault reflect short-wavelength variations of the surface rupture and slip distribution, and attest to large displacement gradients. Along two sections of the fault, characteristic fringe patterns can be recognized, contrasting in density and direction with patterns observed away from the rupture. In order to understand the observed fringe patterns, we compute synthetic interferograms in three simple cases: (1) rigid-body rotations about a vertical axis, (2) about a horizontal axis (tilt), and (3) distributed, simple shear. The orientation and spatial separation of interferometric fringes predicted by these models help constrain near-field deformation and rupture parameters. Where the Kickapoo fault connects with the Homestead Valley fault, the interferogram shows a clear pattern of parallel N20 deg W fringes separated by about 160 m. This pattern and vertical offsets measured along the Kickapoo fault suggest that the block between this fault and the Johnson Valley fault may have been tilted, down to the west. A 5-km block lifted by 1 m on one side would be tilted by an angle of 0.01 deg (190 microrad), producing fringes separated by about 160 m, parallel to the tilt axis. Such a tilt, parallel to a N20 deg W direction, would account for the gradual, northward increase of the vertical slip component observed along the Kickapoo fault. This tilt may also explain the 1 m of reverse slip observed along the 'slip gap' section of the Homestead Valley break. Between the southern end of the Johnson Valley fault and the Eureka Peak fault, where no surface rupture has been mapped, the dense pattern of fringes implies distributed shear, probably resulting from fault slip at depth. The density and direction of the fringes in the gap are consistent with a right-lateral slip of 1.2-3.8 m on a blind fault locked above the depth of 1.5-2 km. Such observations of small wavelength features in the SAR interferogram bring new insights into the near-field displacement gradient and thus on response of the uppermost crust to seismic rupture.

Peltzer, Gilles↗
NASA NTRS2004

Progress towards a space-borne quantum gravity gradiometer

Quantum interferometer gravity gradiometer for 3D mapping is a project for developing the technology of atom interferometer-based gravity sensor in space. The atom interferometer utilizes atomic particles as free fall test masses to measure inertial forces with unprecedented sensitivity and precision. It also allows measurements of the gravity gradient tensor components for 3D mapping of subsurface mass distribution. The overall approach is based on recent advances of laser cooling and manipulation of atoms in atomic and optical physics. Atom interferometers have been demonstrated in research laboratories for gravity and gravity gradient measurements. In this approach, atoms are first laser cooled to micro-kelvin temperatures. Then they are allowed to freefall in vacuum as true drag-free test masses. During the free fall, a sequence of laser pulses is used to split and recombine the atom waves to realize the interferometric measurements. We have demonstrated atom interferometer operation in the Phase I period, and we are implementing the second generation for a complete gradiometer demonstration unit in the laboratory. Along with this development, we are developing technologies at component levels that will be more suited for realization of a space instrument. We will present an update of these developments and discuss the future directions of the quantum gravity gradiometer project.

laser cooling↗
NASA NTRS2006

Flight Test of an Adaptive Controller and Simulated Failure/Damage on the NASA NF-15B

The method of flight-testing the Intelligent Flight Control System (IFCS) Second Generation (Gen-2) project on the NASA NF-15B is herein described. The Gen-2 project objective includes flight-testing a dynamic inversion controller augmented by a direct adaptive neural network to demonstrate performance improvements in the presence of simulated failure/damage. The Gen-2 objectives as implemented on the NASA NF-15B created challenges for software design, structural loading limitations, and flight test operations. Simulated failure/damage is introduced by modifying control surface commands, therefore requiring structural loads measurements. Flight-testing began with the validation of a structural loads model. Flight-testing of the Gen-2 controller continued, using test maneuvers designed in a sequenced approach. Success would clear the new controller with respect to dynamic response, simulated failure/damage, and with adaptation on and off. A handling qualities evaluation was conducted on the capability of the Gen-2 controller to restore aircraft response in the presence of a simulated failure/damage. Control room monitoring of loads sensors, flight dynamics, and controller adaptation, in addition to postflight data comparison to the simulation, ensured a safe methodology of buildup testing. Flight-testing continued without major incident to accomplish the project objectives, successfully uncovering strengths and weaknesses of the Gen-2 control approach in flight.

Buschbacher, Mark↗
NASA NTRS2005

Best-Fit Conic Approximation of Spacecraft Trajectory

A computer program calculates a best conic fit of a given spacecraft trajectory. Spacecraft trajectories are often propagated as conics onboard. The conic-section parameters as a result of the best-conic-fit are uplinked to computers aboard the spacecraft for use in updating predictions of the spacecraft trajectory for operational purposes. In the initial application for which this program was written, there is a requirement to fit a single conic section (necessitated by onboard memory constraints) accurate within 200 microradians to a sequence of positions measured over a 4.7-hour interval. The present program supplants a prior one that could not cover the interval with fewer than four successive conic sections. The present program is based on formulating the best-fit conic problem as a parameter-optimization problem and solving the problem numerically, on the ground, by use of a modified steepest-descent algorithm. For the purpose of this algorithm, optimization is defined as minimization of the maximum directional propagation error across the fit interval. In the specific initial application, the program generates a single 4.7-hour conic, the directional propagation of which is accurate to within 34 microradians easily exceeding the mission constraints by a wide margin.

Singh, Gurkipal↗
NASA NTRS1993

Gas and dust in the pre-main-sequence multiple system GG Tauri

We present 1.4 and 2.7 mm aperture synthesis maps of the gas and dust continuum emission around GG Tauri, a very young component of a premain-sequence multiple star system; both GG Tau and its apparent companion, GG Tau/c, at 1500 AU separation, are themselves binaries. At 1.4 mm, dust continuum emission of about 750 AU in extent is associated with GG Tau, and a secondary peak is near GG Tau/c. Spectral line images reveal gaseous structure around GG Tau, elongated along the GG Tau-GG Tau/c axis. There is some suggestion that the gas associated with GG Tau/c alone is extended in a different direction. Marked changes in the morphology and velocity structure of the molecular emission near GG Tau/c also indicate that this system is differently oriented. Clumps between the two systems may be vestiges of a connecting bar. GG Tau and GG Tau/c appear to have originated in a common cloud; their different systemic orientations suggest that they formed from an initially prolate cloud rather than from an extensive and highly flattened disk.

Koerner, D. W.↗
NASA NTRS1989

ECUT (Energy Conversion and Utilization Technologies) program: Biocatalysis project

The Annual Report presents the fiscal year (FY) 1988 research activities and accomplishments, for the Biocatalysis Project of the U.S. Department of Energy, Energy Conversion and Utilization Technologies (ECUT) Division. The ECUT Biocatalysis Project is managed by the Jet Propulsion Laboratory, California Institute of Technology. The Biocatalysis Project is a mission-oriented, applied research and exploratory development activity directed toward resolution of the major generic technical barriers that impede the development of biologically catalyzed commercial chemical production. The approach toward achieving project objectives involves an integrated participation of universities, industrial companies and government research laboratories. The Project's technical activities were organized into three work elements: (1) The Molecular Modeling and Applied Genetics work element includes research on modeling of biological systems, developing rigorous methods for the prediction of three-dimensional (tertiary) protein structure from the amino acid sequence (primary structure) for designing new biocatalysis, defining kinetic models of biocatalyst reactivity, and developing genetically engineered solutions to the generic technical barriers that preclude widespread application of biocatalysis. (2) The Bioprocess Engineering work element supports efforts in novel bioreactor concepts that are likely to lead to substantially higher levels of reactor productivity, product yields and lower separation energetics. Results of work within this work element will be used to establish the technical feasibility of critical bioprocess monitoring and control subsystems. (3) The Bioprocess Design and Assessment work element attempts to develop procedures (via user-friendly computer software) for assessing the energy-economics of biocatalyzed chemical production processes, and initiation of technology transfer for advanced bioprocesses.

Baresi, Larry↗
NASA NTRS1988

Design of a Ram Accelerator mass launch system

The Ram Accelerator, a chemically propelled, impulsive mass launch system, is presented as a viable concept for directly launching acceleration-insensitive payloads into low Earth orbit. The principles of propulsion are based on those of an airbreathing supersonic ramjet. The payload vehicle acts as the ramjet centerbody and travels through a fixed launch tube that acts as the ramjet outer cowling. The launch tube is filled with premixed gaseous fuel and oxidizer mixtures that combust at the base of the vehicle and produce thrust. Two modes of in-tube propulsion involving ramjet cycles are used in sequence to accelerate the vehicle from 0.7 km/sec to 9 km/sec. Requirements for placing a 2000 kg vehicle into a 500-km circular orbit, with a minimum amount of onboard rocket propellant for orbital maneuvers, are examined. It is shown that in-tube propulsion requirements dictate a launch tube length of 5.1 km to achieve an exit velocity of 9 km/sec, with peak accelerations not to exceed 1000 g's. Aerodynamic heating due to atmospheric transit requires minimal ablative protection and the vehicle retains a large percentage of its exit velocity. An indirect orbital insertion maneuver with aerobraking and two apogee burns is examined to minimize the required onboard propellant mass. An appropriate onboard propulsion system design to perform the required orbital maneuvers with minimum mass requirements is also determined. The structural designs of both the launch tube and the payload vehicle are examined using simple structural and finite element analysis for various materials.

Source record↗
NASA NTRSDate not supplied

The Additive Manufacturing Moment Measure - A Parallel Computation Technique for Determining Build Variance in the Laser Powder Bed Fusion Process

Additive manufacturing (AM) has unique process attributes that facilitate the creation of optimized, complex, and unique parts for aerospace applications. However, the multi-scale and complicated building process for AM parts can cause unexpected build conditions that result in microstructural variability within the deposited material. The need for richer datasets and computational modeling capabilities to improve AM process reliability is a consequence of this microstructural variability. A computational approach, referred to as the Additive Manufacturing Moment Measure (AM3), addresses this need by leveraging the way AM processes fuse material in precise, incremental steps. During the layering sequence, each previous step contributes to the condition of the current step at the center of the heat source. The precise steps can be selected to systematically create a time-space point field with co-located machine input and in-situ sensor data. The sequential nature of the AM process, coupled with nearest neighbor calculations, allows for a fully parallel computation for part-scale build profile analysis. The AM3 concept introduced here enables part-scale assessment directly from build files and in-situ process monitoring sensors alike. The AM moment measures were calculated for build point fields and compared with co-located in-situ and ex-situ nondestructive evaluation and optical microscopy observations. These comparisons permit a better understanding of how the sequential process actions can affect the quality of a laser powder bed fusion (LPBF) build. Details of the AM3technique will be discussed and compared to measured LPBF part characteristics. The AM3 results indicate a strong potential to advance the qualification process for aerospace applications.

Additive Manufacturing↗
NASA NTRS1985

Dynamics of Long-period Comets

Dynamical studies of the origin and evolution of long period comets in the Oort cloud during the past year have concentrated on four areas: (1) interpretation of IRAS observations of dust shells around Vega and some 40 other main sequence stars as evidence for cometary clouds around each of these stars; (2) the dynamical plausibility of an unseen solar companion star orbiting in the Oort cloud and causing periodic cometary showers which result in biological extinction events on the earth; (3) a review of the current hypotheses for cometary formation with particular attention to how each mechanism supplies the required mass of comets to the Oort cloud; and (4) development of new dynamics software to simulate the passage of individual stars directly through the Oort cloud. Each of these efforts is described in detail.

Weissman, P. R.↗
NASA NTRS2000

Ceratopteris richardii: a productive model for revealing secrets of signaling and development

Ceratopteris richardii is an aquatic fern grown in tropical and subtropical regions of the world. It is proven to be a productive model system for studies in the genetics, biochemistry, and cell biology of basic biologic processes that occur in early gametophytic development. It provides several advantages to biologists, especially those interested in gravitational biology, polarity development, and in the genetics of sexual development. It is easy to culture, has a relatively short life cycle, and offers an array of attractive features that facilitate genetic studies. The germination and early development of large populations of genetically identical spores are easy to synchronize, and both the direction of polarity development and cell-level gravity responses can be measured and readily manipulated within the first 24 h of spore development. Although there is no reliable transformation system available yet in Ceratopteris, recent studies suggest that the technique of RNA interference can be used to block translation of specific genes in a related fern, Marsilea, and current studies will soon reveal the applicability of this approach, as well as of other transformation approaches, in Ceratopteris. A recently completed expressed sequence tag (EST) sequencing project makes available the partial sequence of more than 2000 cDNAs, representing a significant percentage of the genes being expressed during the first 24 h of spore germination, when many developmentally interesting processes are occurring. A microarray of these ESTs is being constructed, so especially for those scientists interested in basic cellular phenomena that occur early in spore germination, the availability of the ESTs and of the microarray will make Ceratopteris an even more attractive model system.

NASA Discipline Plant Biology↗
NASA NTRS2016

Initial Incidence of White Matter Hyperintensities on MRI in Astronauts

Introduction: Previous literature has described the increase in white matter hyperintensity (WMH) burden associated with hypobaric exposure in the U-2 and altitude chamber operating personnel. Although astronauts have similar hypobaric exposure pressures to the U2 pilot population, astronauts have far fewer exposures and each exposure would be associated with a much lower level of decompression stress due to rigorous countermeasures to prevent decompression sickness. Therefore, we postulated that the WMH burden in the astronaut population would be less than in U2 pilots. Methods: Twenty-one post-flight de-identified astronaut MRIs (5 mm slice thickness FLAIR sequences) were evaluated for WMH count and volume. The only additional data provided was an age range of the astronauts (43-57) and if they had ever performed an EVA (13 yes, 8 no). Results: WMH count in these 21 astronaut MRI was 21.0 +/- 24.8 (mean+/- SD) and volume was 0.382 +/- 0.602 ml, which was significantly higher than previously published results for the U2 pilots. No significant differences between EVA and no EVA groups existed. Age range of astronaut population is not directly comparable to the U2 population. Discussion: With significantly less frequent (sometimes none) and less stressful hypobaric exposures, yet a much higher incidence of increased WMH, this indicates the possibility of additional mechanisms beyond hypobaric exposure. This increase unlikely to be attributable just to the differences in age between astronauts and U2 pilots. Forward work includes continuing review of post-flight MRI and evaluation of pre to post flight MRI changes if available. Data mining for potential WMH risk factors includes collection of age, sex, spaceflight experience, EVA hours, other hypobaric exposures, hyperoxic exposures, radiation, high performance aircraft experience and past medical history. Finally, neurocognitive and vision/eye results will be evaluated for any evidence of impairment linked to increased WMH.

Norcross, Jason↗
NASA NTRS1993

Neural-network-directed alignment of optical systems using the laser-beam spatial filter as an example

This report describes an effort at NASA Lewis Research Center to use artificial neural networks to automate the alignment and control of optical measurement systems. Specifically, it addresses the use of commercially available neural network software and hardware to direct alignments of the common laser-beam-smoothing spatial filter. The report presents a general approach for designing alignment records and combining these into training sets to teach optical alignment functions to neural networks and discusses the use of these training sets to train several types of neural networks. Neural network configurations used include the adaptive resonance network, the back-propagation-trained network, and the counter-propagation network. This work shows that neural networks can be used to produce robust sequencers. These sequencers can learn by example to execute the step-by-step procedures of optical alignment and also can learn adaptively to correct for environmentally induced misalignment. The long-range objective is to use neural networks to automate the alignment and operation of optical measurement systems in remote, harsh, or dangerous aerospace environments. This work also shows that when neural networks are trained by a human operator, training sets should be recorded, training should be executed, and testing should be done in a manner that does not depend on intellectual judgments of the human operator.

Decker, Arthur J.↗
NASA NTRS2009

Developing a Standard Method for Link-Layer Security of CCSDS Space Communications

Communications security for space systems has been a specialized field generally far removed from considerations of mission interoperability and cross-support in fact, these considerations often have been viewed as intrinsically opposed to security objectives. The space communications protocols defined by the Consultative Committee for Space Data Systems (CCSDS) have a twenty-five year history of successful use in over 400 missions. While the CCSDS Telemetry, Telecommand, and Advancing Orbiting Systems protocols for use at OSI Layer 2 are operationally mature, there has been no direct support within these protocols for communications security techniques. Link-layer communications security has been successfully implemented in the past using mission-unique methods, but never before with an objective of facilitating cross-support and interoperability. This paper discusses the design of a standard method for cryptographic authentication, encryption, and replay protection at the data link layer that can be integrated into existing CCSDS protocols without disruption to legacy communications services. Integrating cryptographic operations into existing data structures and processing sequences requires a careful assessment of the potential impediments within spacecraft, ground stations, and operations centers. The objective of this work is to provide a sound method for cryptographic encapsulation of frame data that also facilitates Layer 2 virtual channel switching, such that a mission may procure data transport services as needed without involving third parties in the cryptographic processing, or split independent data streams for separate cryptographic processing.

Biggerstaff, Craig↗