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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Large Angle Transient Dynamics (LATDYN) demonstration problem manual

LATDYN is a computer code for modeling the Large Angle Transient Dynamics of structures. The objective in developing the code was to investigate new techniques for analyzing flexible deformation and control/structure interaction problems associated with large angular motions of spacecraft. Such motions may consist of pointing the entire spacecraft or articulation of individual components, events which occur frequently during construction, operation, and maintenance of large spacecraft. This type of analysis is beyond the routine capability of conventional analytical tools without simplifying assumptions. In some instances, the motion may be sufficiently slow and the spacecraft (or component) sufficiently rigid to simplify the analysis of dynamics and controls by making pseudo-static and/or rigid body assumptions. LATDYN introduces a new approach to the problem by combining finite element structural analysis, multi-body dynamics, and control system analysis in a single tool. It includes a new type of finite element that can deform and rotate through large angles at the same time, and which can be connected to other finite elements either rigidly or through mechanical joints. LATDYN also provides symbolic capabilities for modeling control systems which are interfaced directly with the finite element structural model. Thus, the nonlinear equations representing the structural model are integrated along with the equations representing sensors, processing, and controls as a coupled system.

Wu, Shih-Chin↗
NASA NTRS2004

Bubble Eliminator Based on Centrifugal Flow

The fluid bubble eliminator (FBE) is a device that removes gas bubbles from a flowing liquid. The FBE contains no moving parts and does not require any power input beyond that needed to pump the liquid. In the FBE, the buoyant force for separating the gas from the liquid is provided by a radial pressure gradient associated with a centrifugal flow of the liquid and any entrained bubbles. A device based on a similar principle is described in Centrifugal Adsorption Cartridge System (MSC- 22863), which appears on page 48 of this issue. The FBE was originally intended for use in filtering bubbles out of a liquid flowing relatively slowly in a bioreactor system in microgravity. Versions that operate in normal Earth gravitation at greater flow speeds may also be feasible. The FBE (see figure) is constructed as a cartridge that includes two concentric cylinders with flanges at the ends. The outer cylinder is an impermeable housing; the inner cylinder comprises a gas-permeable, liquid-impermeable membrane covering a perforated inner tube. Multiple spiral disks that collectively constitute a spiral ramp are mounted in the space between the inner and outer cylinders. The liquid enters the FBE through an end flange, flows in the annular space between the cylinders, and leaves through the opposite end flange. The spiral disks channel the liquid into a spiral flow, the circumferential component of which gives rise to the desired centrifugal effect. The resulting radial pressure gradient forces the bubbles radially inward; that is, toward the inner cylinder. At the inner cylinder, the gas-permeable, liquid-impermeable membrane allows the bubbles to enter the perforated inner tube while keeping the liquid in the space between the inner and outer cylinders. The gas thus collected can be vented via an endflange connection to the inner tube. The centripetal acceleration (and thus the radial pressure gradient) is approximately proportional to the square of the flow speed and approximately inversely proportional to an effective radius of the annular space. For a given FBE geometry, one could increase the maximum rate at which gas could be removed by increasing the rate of flow to obtain more centripetal acceleration. In experiments and calculations oriented toward the original microgravitational application, centripetal accelerations between 0.001 and 0.012 g [where g normal Earth gravitation (.9.8 m/s2)] were considered. For operation in normal Earth gravitation, it would likely be necessary to choose the FBE geometry and the rate of flow to obtain centripetal acceleration comparable to or greater than g.

Gonda, Steve R.↗
NASA NTRS1989

Dynamics of articulated structures

An articulated structure is defined as an assembly of flexible bodies that may be coupled by kinematic connections and force elements that permit large relative displacement and rotation. Kinematics of such systems is defined using one reference frame for each body in the system and deformation modal coordinates that define displacement fields within flexible bodies. Deformation kinematics are defined by both elastic vibration and static correction deformation modes. Linear elastic deformation is presumed; i.e., a linear stress-strain relation is valid and relative displacements within each elastic component are small enough so that the theory of linear elasticity applies. Coupling of reference and modal coordinates leads to a system of nonlinear equations of motion. Methods of automatically generating and solving these equations of motion are outlined.

Haug, Edward J.↗
NASA NTRS1989

Two stage gear tooth dynamics program

The epicyclic gear dynamics program was expanded to add the option of evaluating the tooth pair dynamics for two epicyclic gear stages with peripheral components. This was a practical extension to the program as multiple gear stages are often used for speed reduction, space, weight, and/or auxiliary units. The option was developed for either stage to be a basic planetary, star, single external-external mesh, or single external-internal mesh. The two stage system allows for modeling of the peripherals with an input mass and shaft, an output mass and shaft, and a connecting shaft. Execution of the initial test case indicated an instability in the solution with the tooth paid loads growing to excessive magnitudes. A procedure to trace the instability is recommended as well as a method of reducing the program's computation time by reducing the number of boundary condition iterations.

Boyd, Linda S.↗
NASA NTRS1992

Changes in monkey horizontal semicircular canal afferent responses after spaceflight

Extracellular responses from single horizontal semicircular canal afferents in two rhesus monkeys were studied after recovery from a 14-day biosatellite (Cosmos 2044) orbital spaceflight. On the 1st postflight day, the mean gain for 9 different horizontal canal afferents, tested using one or several different passive yaw rotation waveforms, was nearly twice that for 20 horizontal canal afferents similarly tested during preflight and postflight control studies. Adaptation of the afferent response to passive yaw rotation on the 1st postflight day was also greater. These results suggest that at least one component of the vestibular end organ (the semicircular canals) is transiently modified after exposure to 14 days of microgravity. It is unclear whether the changes are secondary to other effects of microgravity, such as calcium loss, or an adaptive response. If the response is adaptive, then this report is the first evidence that the response of the vestibular end organ may be modified (presumably by the central nervous system via efferent connections) after prolonged unusual vestibular stimulation. If this is the case, the sites of plasticity of vestibular responses may not be exclusively within central nervous system vestibular structures, as previously believed.

Correia, M. J.↗
NASA NTRS1995

Particle fallout/activity sensor

A particle fallout/activity sensor measures relative amounts of dust or other particles which collect on a mirror in an area to be monitored. The sensor includes a sensor module and a data acquisition module, both of which can be operated independently of one another or in combination with one another. The sensor module includes a housing containing the mirror, an LED assembly for illuminating the mirror and an optical detector assembly for detecting light scattered off of the mirror by dust or other particles collected thereon. A microprocessor controls operation of the sensor module's components and displays results of a measurement on an LCD display mounted on the housing. A push button switch is also mounted on the housing which permits manual initiation of a measurement. The housing is constructed of light absorbing material, such as black delrin, which minimizes detection of light by the optical detector assembly other than that scattered by dust or particles on the mirror. The data acquisition module can be connected to the sensor module and includes its own microprocessor, a timekeeper and other digital circuitry for causing the sensor module to make a measurement periodically and send the measurement data to the data acquisition module for display and storage in memory for later retrieval and transfer to a separate computer. The time tagged measurement data can also be used to determine the relative level of activity in the monitored area since this level is directly related to the amount of dust or particle fallout in the area.

Curtis, Ihlefeld M.↗
NASA NTRS2009

Modern Era Retrospective-analysis for Research and Applications (MERRA) Global Water and Energy Budgets

In the Summer of 2009, NASA's Modern Era Retrospective-analysis for Research and Applications (MERRA) will have completed 28 years of global satellite data analyses. Here, we characterize the global water and energy budgets of MERRA, compared with available observations and the latest reanalyses. In this analysis, the climatology of the global average components are studied as well as the separate land and ocean averages. In addition, the time series of the global averages are evaluated. For example, the global difference of precipitation and evaporation generally shows the influence of water vapor observations on the system. Since the observing systems change in time, especially remotely sensed observations of water, significant temporal variations can occur across the 28 year record. These then are also closely connected to changes in the atmospheric energy and water budgets. The net imbalance of the energy budget at the surface can be large and different signs for different reanalyses. In MERRA, the imbalance of energy at the surface tends to improve with time being the smallest during the most recent and abundant satellite observations.

Bosilovich, Michael G.↗
NASA NTRS2020

Fitting Leak Test Report

Many Human Landing System flight elements are anticipated to implement mechanically connected joints in cryogenic fluid lines to simplify system assembly. These joints will need to survive launch vibration, while cold, and remain as leak‐free as possible to minimize commodity loss. Threaded fluid fittings should be qualified for use in their expected environments to reduce risk and ensure mission success. A new ground‐based test apparatus was developed and validated to obtain quantifiable low leak rate test data for a small component, such as a pressurized threaded fluid fitting, while in the temperature range of liquid hydrogen. A cryocooler is used to attain the cold test temperature and helium leakage from a pressurized fitting mounted within a vacuum test chamber is measured using a mass spectrometer leak detector. Two different sizes of Swagelok VCR fittings with three different types of seal rings were selected as the test articles for the initial proof of concept testing. Each fitting configuration was subjected to two consecutive cryogenic thermal cycles and cold leak measurement tests, followed by exposure to a high vibration test profile at ambient temperature on a shaker table, and then two additional cold leak measurement tests. Very low leak rates, below the acceptable leak rate threshold, were measured at the pressures tested. Several enhancements to the test hardware are discussed that would facilitate a comprehensive fitting qualification test campaign by enabling a higher test throughput rate and ensuring a repeatable test profile.

Cryogenic Fluid Management↗
NASA NTRSDate not supplied

The Gandalf Staff: A Mobile Tool for Lunar Exploration (2nd year of development)

The Gandalf Staff is a mobile tool designed to be a flexible device supporting crewed and uncrewed operations on the lunar surface. The core of the device is a 24v battery with communications and data storage systems. Initial optional components supporting crewed Extra-Vehicular Activity (EVA) include a LiDAR and 360˚ camera. These provide 3D mapping of the traverse for documentation, and to aid future planning. The mapping also creates outreach opportunities for the public to “stand beside” the astronaut in Virtual Reality (VR). The staff provides external lighting for field site illumination in the south polar region low sun angle environment. Navigation instruments for crew position determination with Lunar Search and Rescue (LunaSAR) are also included. The staff itself can be used as a walking aid or as a splint for Incapacitated Crew Rescue (ICR). As a stand-alone device, the staff operates as a long duration untended science platform collecting environmental data and sending it to a lunar base station. The stand-alone mode requires connection to an auxiliary power source (e.g. solar array) and energy storage system (e.g. battery), so it could become an electrical recharging station. To make rapid progress in the 1st year, and also to demonstrate innovative project management techniques, NASA guided a private industry partner, T STAR, in leading Capstone Engineering student teams at Texas A&M University (TAMU) for proof-of-concept development and testing. These teams developed the power system and demonstrated successful integration of LiDAR, WiFi communications, and external lighting subsystems. Another industry team at Jacobs Technology prototyped a tripod to hold the staff upright. For the 2nd year (FY’22), NASA will again collaborate with partners to prototype enhanced power and lighting concepts. Year 2 will also add new capability for LunaSAR and geophysical science instrumentation using a heat probe. The heat probe is based upon Apollo heritage but modified to measure subsurface volatile ice regimes at the Artemis landing site. Components of the Gandalf Staff can be developed, tested, and deployed independently, or on the integrated staff, rovers, or utility trailers. The project supports crew safety, lunar sample curation, mission science, and public outreach goals of NASA. PLAIN TEST SUMMARY: Gandalf Staff is a 24v battery powered mobile tool for the lunar surface supporting crewed geologic field site exploration, or as a stand-alone science platform. As a tool assisting astronauts conducting field geology, the Gandalf Staff provides external lighting to illuminate shadowed regions on the surface. It also documents the process of collecting rocks and dust samples using a LiDAR (laser range instrument) and cameras. The staff provides a beacon for emergency location of astronauts and augments communications when the astronauts are blocked by large boulders. As a standalone science platform, the Gandalf Staff provides a power system for instruments and sensors to measure the lunar environment over long periods of time. The staff gathers data and sends the results to a lunar base station for analysis.

External Lighting↗
NASA NTRS1983

High stability amplifier

An electrical RF signal amplifier for providing high temperature stability and RF isolation and comprised of an integrated circuit voltage regulator, a single transistor, and an integrated circuit operational amplifier mounted on a circuit board such that passive circuit elements are located on side of the circuit board while the active circuit elements are located on the other side is described. The active circuit elements are embedded in a common heat sink so that a common temperature reference is provided for changes in ambient temperature. The single transistor and operational amplifier are connected together to form a feedback amplifier powered from the voltage regulator with transistor implementing primarily the desired signal gain while the operational amplifier implements signal isolation. Further RF isolation is provided by the voltage regulator which inhibits cross-talk from other like amplifiers powered from a common power supply. Input and output terminals consisting of coaxial connectors are located on the sides of a housing in which all the circuit components and heat sink are located.

Adams, W. A.↗
NASA NTRS1986

In situ magnetic field measurements during AMPTE solar wind Li(+) releases

The effects of lithium ion releases on solar wind flow are investigated. The background field conditions during the releases on September 11 and 20, 1984 are discussed. The magnetic field data recorded by the Ion Release Module and United Kingdom Satellite are described. It is observed that the first release occurred on the field lines connecting to the earth's bow shock causing difficulty in separating the effects of natural large scale perturbations from the ion effects. In the second release, which occurred in a stable, ambient environment, the characteristics of a Venus-like perturbation of the magnetic field are detected. It is concluded that in both releases a field cavity is formed, the field transverse to the solar wind flow is amplified, and the transverse component is compressed.

Luehr, H.↗
NASA NTRS1988

Auroral origin of a component of Jupiter's decametric radiation

Simultaneous observations at about 22 MHz of an Io-unrelated component of Jovian decametric radiation from Voyagers 1 and 2 and from a ground-based observatory are analyzed to investigate the beam structure of the radiation and to locate the radio-emitting region. It is concluded that the radiation of this component is emitted in quasi-continuous beams that corotate with the Jovian inner magnetosphere and that each beam can be approximated by a sector of a hollow cone. The source locations are geometrically determined by fitting a hollow-cone beam model, based on the O4 magnetic field model, to the observations. The result indicates that the radio sources lie above the northern hemisphere and on the field lines that are connected with the ultraviolet aurora of the so-called active sector.

Maeda, K.↗
NASA NTRS1991

On open and closed field line regions in Tsyganenko's field model and their possible associations with horse collar auroras

The boundary between open and closed field lines is investigated in the empirical Tsyganenko (1987) magnetic field model. All field lines extending to distances beyond -70 R(E), the tailward velocity limit of the Tsyganenko model are defined as open, while all other field lines, which cross the equatorial plane earthward of -70 R(E) and are connected with the earth at both ends, are assumed closed. It is found that this boundary at the surface of the earth, identified as the polar cap boundary, can exhibit the arrowhead shape, pointed toward the sun, which is found in horse collar auroras. For increasing activity levels, the polar cap increases in area and becomes rounder, so that the arrowhead shape is less pronounced. The presence of a net B(y) component can also lead to considerable rounding of the open flux region. The arrowhead shape is found to be closely associated with the increase of B(z) from the midnight region to the flanks of the tail, consistent with a similar increase of the plasma sheet thickness.

Birn, J.↗
NASA NTRS2001

Bitsy Thinks Big

AeroAstro, of Herndon, Virginia, developed a nanospacecraft core module capable of developing recyclable spacecraft designs using standard interfaces. From this core module, known as the Bitsy(TM) kernel, custom spacecraft are able to connect mission-specific instruments and subsystems for variation in mission usage. The nanospacecraft core module may be used in conjunction with an existing microsatellite bus or customized to meet specific requirements. Building on this premise, AeroAstro has developed a line of satellite communications equipment, sun sensors, and Lithium-Ion batteries which are all incorporated in its complete line of mission-specific nanospacecraft. The Bitsy technology is also a key component in AeroAstro#s satellite inspection products and orbital transfer services. In the future, AeroAstro plans to market an even less expensive version of the Bitsy technology. The plan, which is targeted to universities, markets a sort of "satellite in a kit," for less than $1 million. This technology would allow universities to build true space hardware for a fraction of the cost of launching a regular satellite.

Source record↗
NASA NTRS1993

The El Nino/Southern Oscillation and Future Soybean Prices

Recently, it was shown that the application of a method combining singular spectrum analysis (SSA) and the maximum entropy method to univariate indicators of the coupled ocean-atmosphere El Nino/Southern Oscillation (ENSO) phenomenon can be helpful in determining whether an El Nino (EN) or La Nina (LN) event will occur. SSA - a variant of principal component analysis applied in the time domain - filters out variability unrelated to ENSO and separates the quasi-biennial (QB), two-to-three year variability, from a lower-frequency (LF) four-to-six year EN-LN cycle; the total variance associated with ENSO combines the QB and LF modes. ENSO has been known to affect weather conditions over much of the globe. For example, EN events have been connected with unusually rainy weather over the Central and Western US, while the opposite phases of the oscillation (LN) have been plausibly associated with extreme dry conditions over much of the same geographical area...

Keppenne, C.↗
NASA NTRS2020

A Deformed Geometry Synthesis Technique for Determining Stacking and Cryogenically Induced Preloads for the Space Launch System

The Space Launch System (SLS) stacking and Core Stage (CS) fueling induce significant preloads that contribute to the liftoff pad separation “twang”. To accurately capture this, an approach is required that can replicate the physics of all SLS physical stacking steps, CS cryogenic shrinkage, associated geometric nonlinearities, and the transient behavior and decay of the preloads with changing boundary conditions as the vehicle separates from the pad. The Deformed Geometry Synthesis (DGS) approach presented here satisfies the above requirements. DGS determines induced preloads by modeling components in their deformed geometry states and then enforcing compatibility by closing the resulting “deadbands”. DGS seamlessly integrates into the multibody modal synthesis framework and does not require the use of artificial external loads to enforce preloads or post-processing steps to remove their influence. Since DGS iterates to solve for the deformed state inclusive of geometric nonlinearities, running linearized parametrics to exercise different potential orientations of ball jointed struts that connect the CS to Boosters for cryo-shrinkage analyses is entirely avoided. Relative to the transient behavior and decay of stacking and cryo-induced preloads with SLS liftoff pad separation, this is an area of considerable interest to the SLS program. To capture this in the most accurate way possible, DGS algorithms are designed to work with Henkel-Mar nonlinear pad separation algorithms which operate on the separating longitudinal and lateral degrees of freedom (DoFs) between the vehicle and the pad. As the separating DoFs release, in whatever manner as dictated by the interface geometries, interface loads and interface flexibilities as well as the external loading on the vehicle, the subject preloads generate a complex twang/decay time-trace as dictated by the physics of the problem. This paper presents DGS numerical verification against the closed-form solution for Timoshenko’s 3 ball-jointed strut preload problem. This problem is then extended by the authors to the geometric nonlinear case where DGS is compared to the Newton-Raphson solution of the nonlinear equations. Next, DGS is utilized to solve the SLS stacking and cryogenic shrinkage coupled loads analyses. Finally, Henkel-Mar pad separation simulations are executed that isolate the impact of the induced preloads’ twang and decay characteristics.

Space Launch System↗
NASA NTRS1996

A Well Connected Future: Networking Trends

It is clear networks of various types are beginning to have a substantial impact on every aspect of our lives, our jobs, society and the way we perceive and use information. Commerce is moving onto the Internet; doctors are performing surgery and diagnosis with the aid of high performance networks and satellites; and political revolutions and coups are reported through the use of networks. This is only the first glimpse of what is yet to come. This paper is a brief survey of technology research in networking, with emphasis on the use of satellites present and future as a component of a global information mesh.

St.Johns, Michael↗
NASA NTRS1983

Interpretation of aircraft multispectral scanner images for mapping of alteration with uranium mineralization, Copper Mountain, Wyoming

NS-001 multispectral scanner data (0.45-2.35 micron) combined as principal components were utilized to map distributions of surface oxidation/weathering in Precambrian granitic rocks at Copper Mountain, Wyoming. Intense oxidation is found over granitic outcrops in partly exhumed pediments along the southern margin of the Owl Creek uplift, and along paleodrainages higher in the range. Supergene(?) uranium mineralization in the granites is localized beneath remnant Tertiary sediments covering portions of the pediments. The patterns of mineralization and oxidation are in agreement, but the genetic connections between the two remain in doubt.

Conel, J. E.↗