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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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General computer algorithm developed for construction of contour plots. algorithm accepts as input data values at set of points irregularly distributed over plane. Algorithm based on interpolation scheme: points in plane connected by straight-line segments to form set of triangles. Program written in FORTRAN IV.
The term reentry vehicle is used in the broad sense. The vehicles addressed include not only those that return from orbit to the Earth's surface, but also aeroassisted orbit transfer vehicles that use aerodynamic forces generated during atmospheric passes to achieve orbital changes with a smaller expenditure of energy than is required for an all-propulsion vehicle. Advanced reusable launch vehicles with special emphasis on system concepts and the influence of advanced technology on entry vehicle configuration are considered. Three categories of orbital transfer vehicles discussed: synergetic plane-change vehicles, planetary aerocapture vehicles, and LEO to GEO orbital transfer vehicles. While the orbital transfer and planetary vehicles are quite different from conventional winged Earth entry vehicles, synergetic plane change and high cross-range Earth entry vehicles have many similarities. Finally, a possible scenario for the development of the next generation of reentry vehicles is presented.
The roles of advection and turbulent diffusion in controlling tracer transport in the meridional plane of the mesosphere are compared using a version of the global primitive equation model for the middle atmosphere developed by Holton and Wehrbein (1980). The results of model sensitivity tests demonstrated that transport in the mesosphere for long-lived species with large-scale heights, such as H2O, CO, and NO(x), is primarily an advective process; on a global scale, small-scale turbulent diffusion produced by gravity wave breaking plays a secondary role. It is concluded that, for such tracers, the eddy diffusion coefficient used in one-dimensional chemical models of the mesosphere should be regarded as a parameterization of the transport by the meridional circulation, not as a parameterization of mixing by small-scale diffusion.
The development of the RPLUS2D/3D codes is summarized. These codes utilize LU algorithms to solve chemical non-equilibrium flows in a body-fitted coordinate system. The motivation behind the development of these codes is the need to numerically predict chemical non-equilibrium flows for the National AeroSpace Plane Program. Recent improvements include vectorization method, blocking algorithms for geometric flexibility, out-of-core storage for large-size problems, and an LU-SW/UP combination for CPU-time efficiency and solution quality.
Data fron the high-resolution gamma-ray spectroscopy experiment on HEAO 3 have been searched for line emission from the decay of Ti-44 created in recent, as yet unobserved, Galactic supernova explosions, where the ages and locations are unknown. Because the 78 yr mean life of Ti-44 is comparable to the average time between Galactic supernovae, the gamma-ray line emission from its decay should appear as Galactic point sources. No evidence was found for such emission from a point source anywhere in the Galactic plane, with a 1-sigma limit of 8.3 x 10 exp -5 photons/sq cm per sec. Detailed models were developed to simulate the Galactic gamma-ray emission from the decay of Ti-44 produced in both type I and type II supernovae. These models were used with the measured gamma-ray line limits to constrain the supernova yields and recurrence periods.
The development of an Autonomous Space Processor for Orbital Debris (ASPOD) is the ultimate goal. The craft will process, in situ, orbital debris using resources available in low Earth orbit (LEO). The serious problem of orbital debris is briefly described and the nature of the large debris population is outlined. This year, focus was on development of a versatile robotic manipulator to augment an existing robotic arm; incorporation of remote operation of robotic arms; and formulation of optimal (time and energy) trajectory planning algorithms for coordinating robotic arms. The mechanical design of the new arm is described in detail. The versatile work envelope is explained showing the flexibility of the new design. Several telemetry communication systems are described which will enable the remote operation of the robotic arms. The trajectory planning algorithms are fully developed for both the time-optimal and energy-optimal problem. The optimal problem is solved using phase plane techniques while the energy optimal problem is solved using dynamics programming.
It is pointed out that real parametric modal frequency and damping variation for lightly damped systems does not resemble disks on the complex plane. Using complex uncertainty (and therefore disklike) models can introduce conservativeness in the design method. An alternative means of developing suitable complex uncertainty models is presented. It involves treating the uncertainty as perturbations to the system eigenvalues and using a particular linear fractional transformation to cover this uncertainty. This approach is applicable to modes within the bandwidth of control. It can be used in conjunction with the standard perturbation modeling approaches. A simple SISO (single-input single-output) example, motivated by a flexible truss experiment at the Jet Propulsion Laboratory, is discussed in order to illustrate the proposed approach.
An investigation has been made in the Langley 20-foot free-spinning tunnel to determine the erect and inverted spin and recovery characteristics of a 1/30-scale dynamic model of a twin-jet swept-wing fighter airplane. The model results indicate that the optimum erect spin recovery technique determined (simultaneous rudder reversal to full against the spin and aileron deflection to full with the spin) will provide satisfactory recovery from steep-type spins obtained on the airplane. It is considered that the air-plane will not readily enter flat-type spins, also indicated as possible by the model tests, but developed-spin conditions should be avoided in as much as the optimum recovery procedure may not provide satisfactory recovery if the airplane encounters a flat-type developed spin. Satisfactory recovery from inverted spins will be obtained on the airplane by neutralization of all controls. A 30-foot- diameter (laid-out-flat) stable tail parachute having a drag coefficient of 0.67 and a towline length of 27.5 feet will be satisfactory for emergency spin recovery.
A comparative study of different modeling approaches for predicting sandwich panel buckling response is described. The study considers sandwich panels with anisotropic face sheets and a very thick core. Results from conventional analytical solutions for sandwich panel overall buckling and face-sheet-wrinkling type modes are compared with solutions obtained using different finite element modeling approaches. Finite element solutions are obtained using layered shell element models, with and without transverse shear flexibility, layered shell/solid element models, with shell elements for the face sheets and solid elements for the core, and sandwich models using a recently developed specialty sandwich element. Convergence characteristics of the shell/solid and sandwich element modeling approaches with respect to in-plane and through-the-thickness discretization, are demonstrated. Results of the study indicate that the specialty sandwich element provides an accurate and effective modeling approach for predicting both overall and localized sandwich panel buckling response. Furthermore, results indicate that anisotropy of the face sheets, along with the ratio of principle elastic moduli, affect the buckling response and these effects may not be represented accurately by analytical solutions. Modeling recommendations are also provided.
Sensory-motor control of upright human posture may be organized in a top-down fashion such that certain head-trunk coordination strategies are employed to optimize visual and/or vestibular sensory inputs. Previous quantitative models of the biomechanics of human posture control have examined the simple case of ankle sway strategy, in which an inverted pendulum model is used, and the somewhat more complicated case of hip sway strategy, in which multisegment, articulated models are used. While these models can be used to quantify the gross dynamics of posture control, they are not sufficiently detailed to analyze head-trunk coordination strategies that may be crucial to understanding its underlying mechanisms. In this paper, we present a biomechanical model of upright human posture that extends an existing four mass, sagittal plane, link-segment model to a five mass model including an independent head link. The new model was developed to analyze segmental body movements during dynamic posturography experiments in order to study head-trunk coordination strategies and their influence on sensory inputs to balance control. It was designed specifically to analyze data collected on the EquiTest (NeuroCom International, Clackamas, OR) computerized dynamic posturography system, where the task of maintaining postural equilibrium may be challenged under conditions in which the visual surround, support surface, or both are in motion. The performance of the model was tested by comparing its estimated ground reaction forces to those measured directly by support surface force transducers. We conclude that this model will be a valuable analytical tool in the search for mechanisms of balance control.
To help satisfy a need for high-density logic circuits insensitive to radiation, it has been proposed to realize inverse majority gates as microscopic vacuum electronic devices. In comparison with solid-state electronic devices ordinarily used in logic circuits, vacuum electronic devices are inherently much less adversely affected by radiation and extreme temperatures. The proposed development would involve state-of-the-art micromachining and recent advances in the fabrication of carbon-nanotube-based field emitters. A representative three-input inverse majority gate would be a monolithic, integrated structure that would include three gate electrodes, six bundles of carbon nanotubes (serving as electron emitters) at suitable positions between the gate electrodes, and an overhanging anode. The bundles of carbon nanotubes would be grown on degenerately doped silicon substrates that would be parts of the monolithic structure. The gate electrodes would be fabricated as parts of the monolithic structure by means of a double-silicon-on-insulator process developed at NASA's Jet Propulsion Laboratory. The tops of the bundles of carbon nanotubes would lie below the plane of the tops of the gate electrodes. The particular choice of shapes, dimensions, and relative positions of the electrodes and bundles of carbon nanotubes would provide for both field emission of electrons from the bundles of carbon nanotubes and control of the electron current to obtain the inverse majority function, which is described in the paper.
A single-aperture, low-profile antenna design has been developed that supports dual-polarization and simultaneous operation at two wavelengths. It realizes multiple beams in the elevation plane, and supports radiometric, radar, and conical scanning applications. This antenna consists of multiple azimuth sticks, with each stick being a multilayer, hybrid design. Each stick forms the h-plane pattern of the C and Ku-band vertically and horizontally polarized antenna beams. By combining several azimuth sticks together, the elevation beam is formed. With a separate transceiver for each stick, the transmit phase and amplitude of each stick can be controlled to synthesize a beam at a specific incidence angle and to realize a particular side-lobe pattern. By changing the transmit phase distribution through the transceivers, the transmit antenna beam can be steered to different incidence angles. By controlling the amplitude distribution, different side lobe patterns and efficiencies can be realized. The receive beams are formed using digital beam synthesis techniques, resulting in very little loss in the receive path, thus enabling a very-low loss receive antenna to support passive measurements.
Metal oxide semiconductor (MOS) circuits for measuring spatially varying intensities of beams of low-energy charged particles have been developed. These circuits are intended especially for use in measuring fluxes of ions with spatial resolution along the focal planes of mass spectrometers. Unlike prior mass spectrometer focal-plane detectors, these MOS circuits would not be based on ion-induced generation of electrons, and photons; instead, they would be based on direct detection of the electric charges of the ions. Hence, there would be no need for microchannel plates (for ion-to-electron conversion), phosphors (for electron-to-photon conversion), and photodetectors (for final detection) -- components that degrade spatial resolution and contribute to complexity and size. The developmental circuits are based on linear arrays of charge-coupled devices (CCDs) with associated readout circuitry (see figure). They resemble linear CCD photodetector arrays, except that instead of a photodetector, each pixel contains a capacitive charge sensor. The capacitor in each sensor comprises two electrodes (typically made of aluminum) separated by a layer of insulating material. The exposed electrode captures ions and accumulates their electric charges during signal-integration periods.
Over 1,000 experiments have been completed, and others are being conducted and planed on the International Space Station (ISS). In order to make the information on these experiments accessible, the IGOAL develops mobile applications to easily access this content and video products to convey high level concepts. This presentation will feature the Space Station Research Explorer as well as several publicly available video examples.
A 2K x 2K 10 µm cutoff HgCdTe array for background-limited space astronomy has been developed by Teledyne Imaging Sensors to specifications set by JPL, and demonstrated by University of Rochester at a focal plane temperature of 40K for the proposed JPL Near-Earth Object Camera (NEOCam) survey mission under the NASA Planetary Defense Coordination Office. We describe the detector performance for the first large format monolithic HgCdTe detector array tested, including the dark current, well depth, dark current vs. temperature, quantum efficiency, latent image performance, and read noise.
A 2K x 2K 10 µm cutoff HgCdTe array for background-limited space astronomy has been developed by Teledyne Imaging Sensors to specifications set by JPL, and demonstrated by University of Rochester at a focal plane temperature of 40K for the proposed JPL Near-Earth Object Camera (NEOCam) survey mission under the NASA Planetary Defense Coordination Office. We describe the detector performance for the first large format monolithic HgCdTe detector array tested, including the dark current, well depth, dark current vs. temperature, quantum efficiency, latent image performance, and read noise.
In an on-going project for NASA, we are developing a modeling approach to analyze the relationship between the noise level of sonic booms from an experimental supersonic plane and the level of annoyance measured through community response surveys. The goal of the project is to obtain a quantitative relationship between noise level and annoyance that is representative for the affected population. Particular modeling challenges include multiple annoyance measurements per survey respondent and very few occurrences of annoyance overall. To address these challenges, we propose a two-stage model for the presence of high annoyance, with the first stage modeling the probability that a respondent is ever highly annoyed and the second stage a multilevel logistic regression model for high annoyance based on noise level and demographic characteristics. We use a variation of Multilevel Regression and Poststratification (Gelman and Little, 1997) to obtain an overall representative noise-annoyance curve for the population. The approach is applied to data from a NASA pilot study.
In an on-going project for NASA, we are developing a modeling approach to analyze the relationship between the noise level of sonic booms from an experimental supersonic plane and the level of annoyance measured through community response surveys. The goal of the project is to obtain a quantitative relationship between noise level and annoyance that is representative for the affected population. Particular modeling challenges include multiple annoyance measurements per survey respondent and very few occurrences of annoyance overall. To address these challenges, we propose a two-stage model for the presence of high annoyance, with the first stage modeling the probability that a respondent is ever highly annoyed and the second stage a multilevel logistic regression model for high annoyance based on noise level and demographic characteristics. We use a variation of Multilevel Regression and Poststratification (Gelman and Little, 1997) to obtain an overall representative noise-annoyance curve for the population. The approach is applied to data from a NASA pilot study.