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NASA NTRS1981

Simulation of atmospheric turbulent gusts and gust gradients

An improved three-dimensional, nonrecursive model for atmospheric turbulence has been developed which provides for simulation of both instantaneous gusts and gust gradients along the flight path of the Space Shuttle. The one-dimensional gust and gust gradient spectral models, which form the basis for the simulation scheme, are developed from three-dimensional, von Karman spectra, integrated over finite limits based on the characteristic dimensions (length, width, and thickness) of the flight vehicle. By means of the simulation process nondimensional time series for both gusts and gust gradients have been generated and stored on a series of magnetic tapes for four altitude bands ranging from 0 to 10,000 meters. These Shuttle Simulated Turbulence Tapes (SSTT) have been validated by means of spectral and statistical analyses with satisfactory results. The dimensionless form of the time series coupled with the use of a von Karman spectral model (as opposed to a Dryden model) distinguish the SSTT from earlier turbulence simulation concepts.

Tatom, F. B.↗

NASA NTRS2005

Beyond Einstein: From the Big Bang to Black Holes

How did the Universe begin? Does time have a beginning and an end? Does space have edges? The questions are clear and simple. They are as old as human curiosity. But the answers have always seemed beyond the reach of science. Until now. In their attempts to understand how space, time, and matter are connected, Einstein and his successors made three predictions. First, space is expanding from a Big Bang; second, space and time can tie themselves into contorted knots called black holes where time actually comes to a halt; third, space itself contains some kind of energy that is pull- ing the Universe apart. Each of these three predictions seemed so fantastic when it was made that everyone, including Einstein himself, regarded them as unlikely. Incredibly, all three have turned out to be true. Yet Einstein's legacy is one of deep mystery, because his theories are silent on three questions raised by his fantastic predictions: (1) What powered the Big Bang? (2) What happens to space, time, and matter at the edge of a black hole? (3) What is the mysterious dark energy pulling the Universe apart? The answers to these questions-which lie at the crux of where our current theories fail us-will lead to a profound, new understanding of the nature of time and space. To find answers, however, we must venture beyond Einstein. The answers require new theories, such as the inflationary Universe and new insights in high-energy particle theory. Like Einstein s theories, these make fantastic predictions that seem hard to believe: unseen dimensions and entire universes beyond our own. We must find facts to confront and guide these new theories. Powerful new technologies now make this possible. And NASA and its partners are developing an armada of space-based observatories to chart the path to discovery. Here is where the Beyond Einstein story begins. By exploring the three questions that are Einstein s legacy, we begin the next revolution in understanding our Universe. We plot our way forward using clues from observations and from new ideas connecting the worlds of the very small and the very large, from the atom out through the deepest reaches of the cosmos.

Source record↗

NASA NTRS2002

Training, transfer, and retention of three-dimensional spatial memory in virtual environments

Human orientation requires one to remember and visualize spatial arrangements of landmarks from different perspectives. Astronauts have reported difficulties remembering relationships between environmental landmarks when imagined in arbitrary 3D orientations. The present study investigated the effects of strategy training on humans' 1) ability to infer their orientation from landmarks presented ahead and below, 2) performance when subsequently learning a different array, and 3) retention of configurational knowledge over time. On the first experiment day, 24 subjects were tested in a virtual cubic chamber in which a picture of an animal was drawn on each wall. Through trial-by-trial exposures, they had to memorize the spatial relationships among the six pictures around them and learn to predict the direction to a specific picture when facing any view direction, and in any roll orientation. Half of the subjects ("strategy group") were taught methods for remembering picture groupings, while the remainder received no such training ("control group"). After learning one picture array, the procedure was repeated in a second. Accuracy (% correct) and response time learning curves were measured. Performance for the second array and configurational memory of both arrays were also retested 1, 7, and 30 days later. Results showed that subjects "learned how to learn" this generic 3D spatial memory task regardless of their relative orientation to the environment, that ability and configurational knowledge was retained for at least a month, that figure rotation ability and field independence correlate with performance, and that teaching subjects specific strategies in advance significantly improves performance. Training astronauts to perform a similar generic 3D spatial memory task, and suggesting strategies in advance, may help them orient in three dimensions.

Non-NASA Center↗

NASA NTRS1989

Triaxial ellipsoid dimensions and rotational pole of 2 Pallas from two stellar occultations

The ability to derive unique triaxial ellipsoid dimensions and a rotational pole for an asteroid is demonstrated on the basis of three stellar occultations. Two such occultations for Pallas are used to examine the locus of solutions falling along a curve in seven-dimensional parameter space. While the first occultation slightly overestimated the true size of the asteroid's outline, more plausible solutions are allowed within its errors. The occultation model is combined with speckle interferometric results. Pallas is more flattened, with a greater b/c ratio, and smaller c, than found in previous estimates.

Drummond, Jack D.↗

NASA NTRS1989

Acoustic controlled rotation and orientation

Acoustic energy is applied to a pair of locations spaced about a chamber, to control rotation of an object levitated in the chamber. Two acoustic transducers applying energy of a single acoustic mode, one at each location, can (one or both) serve to levitate the object in three dimensions as well as control its rotation. Slow rotation is achieved by initially establishing a large phase difference and/or pressure ratio of the acoustic waves, which is sufficient to turn the object by more than 45 deg, which is immediately followed by reducing the phase difference and/or pressure ratio to maintain slow rotation. A small phase difference and/or pressure ratio enables control of the angular orientation of the object without rotating it. The sphericity of an object can be measured by its response to the acoustic energy.

Barmatz, Martin B.↗

NASA NTRS1995

Automated Laser Cutting In Three Dimensions

Computer-controlled machine-tool system uses laser beam assisted by directed flow of air to cut refractory materials into complex three-dimensional shapes. Velocity, position, and angle of cut varied. In original application, materials in question were thermally insulating thick blankets and tiles used on space shuttle. System shapes tile to concave or convex contours and cuts beveled edges on blanket, without cutting through outer layer of quartz fabric part of blanket. For safety, system entirely enclosed to prevent escape of laser energy. No dust generated during cutting operation - all material vaporized; larger solid chips dislodged from workpiece easily removed later.

Bird, Lisa T.↗

NASA NTRS1999

Initial Study of Friction Pull Plug Welding

Pull plug friction welding is a new process being developed to conveniently eliminate defects from welded plate tank structures. The general idea is to drill a hole of precise, optimized dimensions and weld a plug into it, filling the hole perfectly. A conically-shaped plug is rotated at high angular velocity as it is brought into contact with the plate material in the hole. As the plug is pulled into the hole, friction rapidly raises the temperature to the point at which the plate material flows plastically. After a brief heating phase, the plug rotation is terminated. The plug is then pulled upon with a forging force, solidly welding the plug into the hole in the plate. Three aspects of this process were addressed in this study. The transient temperature distribution was analyzed based on slightly idealized boundary conditions for different plug geometries. Variations in hole geometry and ram speed were considered, and a program was created to calculate volumes of displaced material and empty space, as well as many other relevant dimensions. The relation between the axially applied forging force and the actual forging pressure between the plate and plug surfaces was determined for various configurations.

Rich, Brian S.↗

NASA NTRS1983

Grid generation in three dimensions by Poisson equations with control of cell size and skewness at boundary surfaces

An algorithm for generating computational grids about arbitrary three-dimensional bodies is developed. The elliptic partial differential equation (PDE) approach developed by Steger and Sorenson and used in the NASA computer program GRAPE is extended from two to three dimensions. Forcing functions which are found automatically by the algorithm give the user the ability to control mesh cell size and skewness at boundary surfaces. This algorithm, as is typical of PDE grid generators, gives smooth grid lines and spacing in the interior of the grid. The method is applied to a rectilinear wind-tunnel case and to two body shapes in spherical coordinates.

Sorenson, R. L.↗

NASA NTRS1985

Static solutions in D = 3 Einstein-Maxwell theory

The spacetime generated by a massive point charge in Einstein-Maxwell theory at three spacetime dimensions is obtained. Some of its properties include infinite total energy due to the slow fall off of the electric field, and necessary vanishing of the particle's charge if its mechanical mass is sufficient to close up space. Although g sub 00 vanishes on a coordinate circle, there is no event (but only a Killing) horizon and the curvature invariants are finite except at the source and at infinity. There are no static multi-charge solutions.

Deser, S.↗

NASA NTRS2000

The Tropical Rainfall Measuring (TRMM) - What Have We Learned and What Does the Future Hold?

Rainfall is important in the hydrological cycle and to the lives and welfare of humans. In addition to being a life-giving resource, rainfall processes also plays a crucial role in the dynamics of the global atmospheric circulation. Three-fourths of the energy that drives the atmospheric wind circulation comes from the latent heat released by tropical precipitation. It varies greatly in space and time. The rain-producing cloud systems may last several hours or days. Their dimensions range from 10 km to several hundred km. This makes it difficult to incorporate rainfall directly large-scale weather and climate models. Until the end of 1997, precipitation in the global tropics was not known to within a factor of two. Regarding "global warming", the various large-scale models differed among themselves in the predicted magnitude of the warming and in the expected regional effects of these temperature and moisture changes. The Tropical Rainfall Measuring Mission (TRMM) satellite has yielded important interim results related to rainfall observations, data assimilation and model forecast skills when rainfall data is assimilated. This talk will summarize where the TRMM science team is with regards to answering some of these important scientific challenges, as well as discuss the future Global Precipitation Mission which will provide 3 hourly rainfall coverage and offers some unique collaborative potential for NOAA and NASA.

Kummerow, C.↗

NASA NTRS2011

Metrology Arrangement for Measuring the Positions of Mirrors of a Submillimeter Telescope

The position of the secondary mirror of a submillimeter telescope with respect to the primary mirror needs to be known .0.03 mm in three dimensions. At the time of this reporting, no convenient, reasonably priced arrangement that offers this capability exists. The solution proposed here relies on measurement devices developed and deployed for the GeoSAR mission, and later adapted for the ISAT (Innovative Space Based Radar Antenna Technology) demonstration. The measurement arrangement consists of four metrology heads, located on an optical bench, attached to the secondary mirror. Each metrology head has a dedicated target located at the edge of the primary mirror. One laser beam, launched from the head and returned by the target, is used to measure distance. Another beam, launched from a beacon on the target, is monitored by the metrology head and generates a measurement of the target position in the plane perpendicular to the laser beam. A 100-MHz modulation is carried by a collimated laser beam. The relevant wavelength is the RF one, 3 m, divided by two, because the light carries it to the target and back. The phase change due to travel to the target and back is measured by timing the zero-crossing of the RF modulation, using a 100-MHz clock. In order to obtain good resolution, the 100-MHz modulation signal is down-converted to 1 kHz. Then, the phase change corresponding to the round-trip to the target is carried by a 1-kHz signal. Since the 100-MHz clock beats 100,000 times during one period of the 1-kHz signal, the least-significant-bit (LSB) resolution is LSB = 0.015 mm.

Abramovici, Alex↗

NASA NTRS2015

Exercise Equipment Usability Assessment for a Deep Space Concept Vehicle

With international aspirations to send astronauts to deep space, the world is now faced with the complex problem of keeping astronauts healthy in unexplored hostile environments for durations of time never before attempted by humans. The great physical demands imparted by space exploration compound the problem of astronaut health, as the astronauts must not only be healthy, but physically fit upon destination arrival in order to perform the scientific tasks required of them. Additionally, future deep space exploration necessitates the development of environments conducive to long-duration habitation that would supplement propulsive vehicles. Space Launch System (SLS) core stage barrel sections present large volumes of robust structure that can be recycled and used for long duration habitation. This assessment will focus on one such conceptual craft, referred to as the SLS Derived Habitat (SLS-DH). Marshall Space Flight Center's (MSFC) Advanced Concepts Office (ACO) has formulated a high-level layout of this SLS-DH with parameters such as floor number and orientation, floor designations, grid dimensions, wall placement, etc. Yet to be determined, however, is the layout of the exercise area. Currently the SLS-DH features three floors laid out longitudinally, leaving 2m of height between the floor and ceilings. This short distance between levels introduces challenges for proper placement of exercise equipment such as treadmills and stationary bicycles, as the dynamic envelope for the 95th percentile male astronauts is greater than 2m. This study aims to assess the optimal equipment layout and sizing for the exercise area of this habitat. Figure 1 illustrates the layout of the DSH concept demonstrator located at MSFC. The exercise area is located on the lower level, seen here as the front half of the level occupied by a crew member. This small volume does not allow for numerous or bulky exercise machines, so the conceptual equipment has been limited to a treadmill and stationary bicycle. With the most current treadmill aboard the International Space Station (ISS), the Combined Operational Load-Bearing External Resistance Treadmill (COLBERT), being located in an International Standard Payload Rack (ISPR), the bottom of the conceptual treadmill features a height of 38in. Making the treadmill flush with the floor would be impossible in this rack configuration, as the distance from the outer wall of the spacecraft to the bottom floor would be too shallow. From preliminary sizing, the 38in required for the bottom of the treadmill combined with a 78in operational envelope for a 95th percentile may not be accommodated in the exercise area in a vertical orientation. Figure 2 demonstrates the volume required (in maroon) for an ISPR-bound treadmill in the concept demonstrator. Early indications as seen in this figure indicate that the crew members would contact the ceiling in such an arrangement. An assessment will be conducted to evaluate various orientations of exercise equipment in the concept demonstrator. Orientations to be tested include putting the bottom of the treadmill on the wall, having the treadmill at an angle in the floor both horizontally and vertically, and having a shorter (non-rack bound) treadmill in a vertical orientation on the floor. This assessment will yield findings regarding sizing of the area and how well participants feel they could exercise in such an environment. Due to the restrictions of assessing a microgravity vehicle in a normal-gravity environment, simulations in MSFC's Virtual Environments Lab (VEL) may be necessary. Final deliverables will include recommendations regarding the location and size of possible exercise equipment aboard the SLS-Derived DSH.

Rhodes, Brooke M.↗

NASA NTRS1984

Thematic Mapper Spectral Dimensionality and Data Structure

Thematic Mapper data, simulated from field and laboratory spectrometer measurements of a variety of agricultural crops and a wide range of soils, are analyzed to determine their dispersion in the six space defined by the reflective TM bands (i.e., excluding the thermal band). While similar analyses of MSS data from agricultural scenes show that the vast majority of the MSS data occupy a single plane, the simulated TM data primarily occupy three dimensions, defining two intersecting planes and a zone of transition between the two. Viewing the plane of Vegetation head on provides a projection comparable to the single plane of MSS data. The Plane of Soils and transition zone represent new information made available largely as a result of the longer infrared bands included in the Thematic Mapper. A transformation, named the Thematic Mapper Tasseled Cap, is presented which rotates the TM data such that the described data structure is most readily accessible to view.

Crist, E. P.↗

NASA NTRS1986

The LATDYN user's manual

The LATDYN User's Manual presents the capabilities and instructions for the LATDYN (Large Angle Transient DYNamics) computer program. The LATDYN program is a tool for analyzing the controlled or uncontrolled dynamic transient behavior of interconnected deformable multi-body systems which can undergo large angular motions of each body relative other bodies. The program accommodates large structural deformation as well as large rigid body rotations and is applicable, but not limited to, the following areas: (1) development of large flexible space structures; (2) slewing of large space structure components; (3) mechanisms with rigid or elastic components; and (4) robotic manipulations of beam members. Presently the program is limited to two dimensional problems, but in many cases, three dimensional problems can be exactly or approximately reduced to two dimensions. The program uses convected finite elements to affect the large angular motions involved in the analysis. General geometry is permitted. Detailed user input and output specifications are provided and discussed with example runstreams. To date, LATDYN has been configured for CDC/NOS and DEC VAX/VMS machines. All coding is in ANSII-77 FORTRAN. Detailed instructions regarding interfaces with particular computer operating systems and file structures are provided.

Housner, J. M.↗

NASA NTRS2001

Hippocampal place-cell firing during movement in three-dimensional space

"Place" cells of the rat hippocampus are coupled to "head direction" cells of the thalamus and limbic cortex. Head direction cells are sensitive to head direction in the horizontal plane only, which leads to the question of whether place cells similarly encode locations in the horizontal plane only, ignoring the z axis, or whether they encode locations in three dimensions. This question was addressed by recording from ensembles of CA1 pyramidal cells while rats traversed a rectangular track that could be tilted and rotated to different three-dimensional orientations. Cells were analyzed to determine whether their firing was bound to the external, three-dimensional cues of the environment, to the two-dimensional rectangular surface, or to some combination of these cues. Tilting the track 45 degrees generally provoked a partial remapping of the rectangular surface in that some cells maintained their place fields, whereas other cells either gained new place fields, lost existing fields, or changed their firing locations arbitrarily. When the tilted track was rotated relative to the distal landmarks, most place fields remapped, but a number of cells maintained the same place field relative to the x-y coordinate frame of the laboratory, ignoring the z axis. No more cells were bound to the local reference frame of the recording apparatus than would be predicted by chance. The partial remapping demonstrated that the place cell system was sensitive to the three-dimensional manipulations of the recording apparatus. Nonetheless the results were not consistent with an explicit three-dimensional tuning of individual hippocampal neurons nor were they consistent with a model in which different sets of cells are tightly coupled to different sets of environmental cues. The results are most consistent with the statement that hippocampal neurons can change their "tuning functions" in arbitrary ways when features of the sensory input or behavioral context are altered. Understanding the rules that govern the remapping phenomenon holds promise for deciphering the neural circuitry underlying hippocampal function.

Non-NASA Center↗

NASA NTRS2001

Spectral Dimensionality and Scale of Urban Radiance

Characterization of urban radiance and reflectance is important for understanding the effects of solar energy flux on the urban environment as well as for satellite mapping of urban settlement patterns. Spectral mixture analyses of Landsat and Ikonos imagery suggest that the urban radiance field can very often be described with combinations of three or four spectral endmembers. Dimensionality estimates of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) radiance measurements of urban areas reveal the existence of 30 to 60 spectral dimensions. The extent to which broadband imagery collected by operational satellites can represent the higher dimensional mixing space is a function of both the spatial and spectral resolution of the sensor. AVIRIS imagery offers the spatial and spectral resolution necessary to investigate the scale dependence of the spectral dimensionality. Dimensionality estimates derived from Minimum Noise Fraction (MNF) eigenvalue distributions show a distinct scale dependence for AVIRIS radiance measurements of Milpitas, California. Apparent dimensionality diminishes from almost 40 to less than 10 spectral dimensions between scales of 8000 m and 300 m. The 10 to 30 m scale of most features in urban mosaics results in substantial spectral mixing at the 20 m scale of high altitude AVIRIS pixels. Much of the variance at pixel scales is therefore likely to result from actual differences in surface reflectance at pixel scales. Spatial smoothing and spectral subsampling of AVIRIS spectra both result in substantial loss of information and reduction of apparent dimensionality, but the primary spectral endmembers in all cases are analogous to those found in global analyses of Landsat and Ikonos imagery of other urban areas.

Small, Christopher↗

NASA NTRS2002

Bioinspired engineering of exploration systems for NASA and DoD

A new approach called bioinspired engineering of exploration systems (BEES) and its value for solving pressing NASA and DoD needs are described. Insects (for example honeybees and dragonflies) cope remarkably well with their world, despite possessing a brain containing less than 0.01% as many neurons as the human brain. Although most insects have immobile eyes with fixed focus optics and lack stereo vision, they use a number of ingenious, computationally simple strategies for perceiving their world in three dimensions and navigating successfully within it. We are distilling selected insect-inspired strategies to obtain novel solutions for navigation, hazard avoidance, altitude hold, stable flight, terrain following, and gentle deployment of payload. Such functionality provides potential solutions for future autonomous robotic space and planetary explorers. A BEES approach to developing lightweight low-power autonomous flight systems should be useful for flight control of such biomorphic flyers for both NASA and DoD needs. Recent biological studies of mammalian retinas confirm that representations of multiple features of the visual world are systematically parsed and processed in parallel. Features are mapped to a stack of cellular strata within the retina. Each of these representations can be efficiently modeled in semiconductor cellular nonlinear network (CNN) chips. We describe recent breakthroughs in exploring the feasibility of the unique blending of insect strategies of navigation with mammalian visual search, pattern recognition, and image understanding into hybrid biomorphic flyers for future planetary and terrestrial applications. We describe a few future mission scenarios for Mars exploration, uniquely enabled by these newly developed biomorphic flyers.

Space Flight↗

NASA NTRS2008

Sub-Surface Windscreen for the Measurement of Outdoor Infrasound

A windscreen has been developed that features two advantages favorable for the measurement of outdoor infrasound. First, the sub-surface location, with the top of the windscreen flush with the ground surface, minimizes the mean velocity of the impinging wind. Secondly, the windscreen material (closed cell polyurethane foam) has a sufficiently low acoustic impedance (222 times that of air) and wall thickness (0.0127 m) to provide a transmission coefficient of nearly unity over the infrasonic frequency range (0-20 Hz). The windscreen, a tightly-sealed box having internal dimensions of 0.3048 x 0.3048 x 0.3556 m, contains a microphone, preamplifier, and a cable feed thru to an external power supply. Provisions are made for rain drainage and seismic isolation. A three-element array, configured as an equilateral triangle with 30.48 m spacing and operating continuously in the field, periodically receives highly coherent signals attributed to emissions from atmospheric turbulence. The time delays between infrasonic signals received at the microphones permit determination of the bearing and elevation of the sources, which correlate well with locations of pilot reports (PIREPS) within a 320 km radius about the array. The test results are interpreted to yield spectral information on infrasonic emissions from clear air turbulence.

Shams, Qamar A.↗