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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

The Space Station program

Likely configurations and goals of the Space Station are delineated. The Station will be a permanent facility designed to be amenable to evolutionary changes. It will be highly automated and user friendly, will be used to perform basic scientific research and observations and to study technologies and processes that may lead to products manufactured in space, and will allow the repair, refurbishment and launch of satellites. The configuration of the Station is being guided by input from future users, which have already helped identify a need to place the laboratory modules at the center of the station to minimize accelerations imparted by other Station activities. Materials which have commercial potential and can only be produced in space after process definition on the Station are discussed, along with NASA efforts to inform industries of the benefits of participation in the program.

Raney, William P.↗
NASA NTRS1987

LFC: A maturing concept

The existence of both turbulent and laminar flow was known for a long time, but it was not until the middle of the last century that the first systematic tests with fluids were conducted to establish the physical relationships and governing laws. The importance of turbulent and laminar airflows in aeronautics was recognized as early as the 1930's, but actual laminar flow control (LFC) investigations were not undertaken until the 1940's. This overview briefly touches on some of the historical development of LFC leading up to current activities. It then examines the technical problems being addressed and potential long-term LFC applications. Past and current Douglas activities are examined and the required future testing involving hybrid laminar flow control (HLFC) is discussed.

Morris, John↗
NASA NTRS1990

Computer simulation in template-directed oligonucleotide synthesis

It is commonly assumed that template-directed polymerizations have played a key role in prebiotic evolution. A computer simulation that models up to 33 competing reactions was used to investigate the product distribution in a template-directed oligonucleotide synthesis as a function of time and concentration of the reactants. The study focuses on the poly(C)-directed elongation reaction of oligoguanylates, and how it is affected by the competing processes of hydrolysis and dimerization of the activated monomer, which have the potential of severely curtailing the elongation and reducing the size and yield of the synthesized polymers. The simulations show that realistic and probably prebiotically plausible conditions can be found where hydrolysis and dimerization are either negligible or where a high degree of polymerization can be attained even in the face of substantial hydrolysis and/or dimerization.

Kanavarioti, Anastassia↗
NASA NTRS1992

Measurement of surface physical properties and radiation balance for KUREX-91 study

Biophysical properties and radiation balance components were measured at the Streletskaya Steppe Reserve of the Russian Republic in July 1991. Steppe vegetation parameters characterized include leaf area index (LAI), leaf angle distribution, mean tilt angle, canopy height, leaf spectral properties, leaf water potential, fraction of absorbed photosynthetically active radiation (APAR), and incoming and outgoing shortwave and longwave radiation. Research results, biophysical parameters, radiation balance estimates, and sun-view geometry effects on estimating APAR are discussed. Incoming and outgoing radiation streams are estimated using bidirectional spectral reflectances and bidirectional thermal emittances. Good agreement between measured and modeled estimates of the radiation balance were obtained.

Walter-Shea, Elizabeth A.↗
NASA NTRS1991

Reinterpretation of reduction potential measurements done by linear sweep voltammetry in silicate melts

The equilibrium concentrations of Ni between silicate melt and Pt were determined experimentally as a function of oxygen fugacity. The results demonstrate that metallic species derived in linear sweep voltammetry experiments in silicate melts are diffusing into Pt electrodes and not into the melt, as was concluded by previoius studies. This requires reinterpretation of previous linear sweep voltammetry results and recalculation and correction of reported reduction potentials. This paper reports these corrected reduction potentials. Also reported are the activity coefficients for Ni in synthetic basalt and diopsidic melts and for Co in diopsidic melt.

Colson, R. O.↗
NASA NTRS1992

A regularization method for extrapolation of solar potential magnetic fields

The mathematical basis of a Tikhonov regularization method for extrapolating the chromospheric-coronal magnetic field using photospheric vector magnetograms is discussed. The basic techniques show that the Cauchy initial value problem can be formulated for potential magnetic fields. The potential field analysis considers a set of linear, elliptic partial differential equations. It is found that, by introducing an appropriate smoothing of the initial data of the Cauchy potential problem, an approximate Fourier integral solution is found, and an upper bound to the error in the solution is derived. This specific regularization technique, which is a function of magnetograph measurement sensitivities, provides a method to extrapolate the potential magnetic field above an active region into the chromosphere and low corona.

Gary, G. A.↗
NASA NTRS1993

Magnetic bearings for a high-performance optical disk buffer

An optical disk buffer concept can provide gigabit-per-second data rates and terabit capacity through the use of arrays of solid state lasers applied to a stack of erasable/reusable optical disks. The RCA optical disk buffer has evoked interest by NASA for space applications. The porous graphite air bearings in the rotary spindle as well as those used in the linear translation of the read/write head would be replaced by magnetic bearings or mechanical (ball or roller) bearings. Based upon past experience, roller or ball bearings for the translation stages are not feasible. Unsatisfactory, although limited experience exists with ball bearing spindles also. Magnetic bearings, however, appear ideally suited for both applications. The use of magnetic bearings is advantageous in the optical disk buffer because of the absence of physical contact between the rotating and stationary members. This frictionless operation leads to extended life and reduced drag. The manufacturing tolerances that are required to fabricate magnetic bearings would also be relaxed from those required for precision ball and gas bearings. Since magnetic bearings require no lubricant, they are inherently compatible with a space (vacuum) environment. Magnetic bearings also allow the dynamics of the rotor/bearing system to be altered through the use of active control. This provides the potential for reduced vibration, extended regions of stable operation, and more precise control of position.

Hockney, Richard↗
NASA NTRS1993

Foreign object impact assessment of a high-Mach engine inlet

The paper presents a foreign-object damage (FOD) assessment of the engine inlet region of a high-velocity aircraft design. Of particular interest is the potential for damage to the active cooling system, which is an integral part of the external skin. A variety of impactors is considered, including hailstones, birds, and rocks of various sizes. An explicit finite element solution, which permits detailed modeling of inelastic material behavior and other nonlinearities, is used for the simulations. The paper also discusses some general aspects of foreign object impact modeling and explicit solution techniques.

Thomson, D. E.↗
NASA NTRS1994

Technical assessment of Mir-1 life support hardware for the international space station

NASA has been progressively learning the design and performance of the Russian life support systems utilized in their Mir space station. In 1992, a plan was implemented to assess the benefits of the Mir-1 life support systems to the Freedom program. Three primary tasks focused on: evaluating the operational Mir-1 support technologies and understanding if specific Russian systems could be directly utilized on the American space station and if Russian technology design information could prove useful in improving the current design of the planned American life support equipment; evaluating the ongoing Russian life support technology development activities to determine areas of potential long-term application to the U.S. space station; and utilizing the expertise of their space station life support systems to evaluate the benefits to the current U.S. space station program which included the integration of the Russian Mir-1 designs with the U.S. designs to support a crew of six.

Mitchell, K. L.↗
NASA NTRS1994

Selected topics on the active control of helicopter aeromechanical and vibration problems

This paper describes in a concise manner three selected topics on the active control of helicopter aeromechanical and vibration problems. The three topics are as follows: (1) the active control of helicopter air-resonance using an LQG/LTR approach; (2) simulation of higher harmonic control (HHC) applied to a four bladed hingeless helicopter rotor in forward flight; and (3) vibration suppression in forward flight on a hingeless helicopter rotor using an actively controlled, partial span, trailing edge flap, which is mounted on the blade. Only a few selected illustrative results are presented. The results obtained clearly indicate that the partial span, actively controlled flap has considerable potential for vibration reduction in helicopter rotors.

Friedmann, Peretz P.↗
NASA NTRS1993

Is the magnetosphere a lens for MHD waves?

A viewpoint of the magnetosphere as a lens for MHD waves is presented. Using a simple model of the variation of the Alfven speed as proportional to the local magnetic value given by the Earth's dipole field and that due to the magnetopause currents represented by a current loop, it is found that the near-Earth magnetotail, in the range 8-16 R(sub E), is the focus of the magnetospheric lens. This location is found to be quite insensitive to a wide variation of parameters. By using simple diffraction theory analysis it is found that the focal region extends about 1 R(sub E) about the neutral sheet in the north-south plane and 0.2 - 0.5 R(sub E) along the Sun-Earth line. Compressive MHD waves carried by the solar wind or created by the interaction of the wind with the magnetopause can be amplified by a factor of about 100 in the focal region and this has potentially important implications to substorm activity.

Papadopoulos, K.↗
NASA NTRS1995

The role of small missions in planetary and lunar exploration

The Space Studies Board of the National Research Council charged its Committee on Planetary and Lunar Exploration (COMPLEX) to (1) examine the degree to which small missions, such as those fitting within the constraints of the Discovery program, can achieve priority objectives in the lunar and planetary sciences; (2) determine those characteristics, such as level of risk, flight rate, target mix, university involvement, technology development, management structure and procedures, and so on, that could allow a successful program; (3) assess issues, such as instrument selection, mission operations, data analysis, and data archiving, to ensure the greatest scientific return from a particular mission, given a rapid deployment schedule and a tightly constrained budget; and (4) review past programmatic attempts to establish small planetary science mission lines, including the Planetary Observers and Planetary Explorers, and consider the impact management practices have had on such programs. A series of small missions presents the planetary science community with the opportunity to expand the scope of its activities and to develop the potential and inventiveness of its members in ways not possible within the confines of large, traditional programs. COMPLEX also realized that a program of small planetary missions was, in and of itself, incapable of meeting all of the prime objectives contained in its report 'An Integrated Strategy for the Planetary Sciences: 1995-2010.' Recommendations are provided for the small planetary missions to fulfill their promise.

Source record↗
NASA NTRS1995

Prospects for commercialization of SELV-based in-space operations

A workshop was hosted by the Langley Research Center as a part of an activity to assess the commercialization potential of Small Expendible Launch Vehicle-based in-space operations. Representatives of the space launch insurance industry, industrial consultants, producers of spacecraft, launch vehicle manufacturers, and government researchers constituted the participants. The workshop was broken into four sessions: Customers Small Expendible Launch Systems, Representative Missions, and Synthesis-Government role. This publication contains the presentation material, written synopses of the sessions, and conclusions developed at the workshop.

Katzberg, Stephen J.↗
NASA NTRS1991

The Effects of Hypergravic Fields on Neural Signalling in the Hippocampus

The goal of this grant is to study the effect of hypergravic fields on the modulation of hippocampal electrical activity by serotonin (5-HT). The proposed study represents a shift from our previous NASA grants covering three diverse areas in neurobiology (thermoregulation, vestibular and auditory brainstem evoked responses, and the hippocampus) to consideration of only one of these areas, the hippocampus. To place our proposed hippocampal experiments in context with relevant Spacelab-3 experiments and hypergravic experiments, two experiments on receptor changes in animals exposed to altered gravitational fields are first described. Our experiments build on these structural/biochemical observations and extend investigations to related electrical activity at 1 G and in hypergravic fields. The background continues with a review of past studies at 1G related to effects of serotonin on hippocampal electrical activity (i.e., population spikes, intracellular potentials).

Horowitz, John↗
NASA NTRS1996

A New Method for the Adaptive Control of Vortex-Wall Interactions

The control of vortical flows is gaining significance in the design of aeronautical and marine structures. While passive devices have been used effectively in the past, active control strategies have the potential of allowing a leap in the performance of future configurations. The efficiency of control schemes is strongly dependent on the development of accurate flow models that can be devised using information that is available not only from numerical solutions of the governing Navier-Stokes equations but also can be measured experimentally. In that context it is desirable to construct adaptive control schemes using information that can be measured at the wall.

Koumoutsakos, P.↗
NASA NTRS1995

A New Potential Energy Surface for N+O2: Is There an NOO Minimum?

We report a new calculation of the N+02 potential energy surface using complete active space self-consistent field internally contracted configuration interaction with the Dunning correlation consistent basis sets. The peroxy isomer of N02 is found to be a very shallow minimum separated from NO+O by a barrier of only 0.3 kcal/mol (excluding zero-point effects). The entrance channel barrier height is estimated to be 8.6 kcal/mol for ICCI+Q calculations correlating all but the Ols and N1s electrons with a cc-p VQZ basis set.

Walch, Stephen P.↗
NASA NTRS2003

Parametric Transformation Analysis

Because twisted coronal features are important proxies for predicting solar eruptive events, and, yet not clearly understood, we present new results to resolve the complex, non-potential magnetic field configurations of active regions. This research uses free-form deformation mathematics to generate the associated coronal magnetic field. We use a parametric representation of the magnetic field lines such that the field lines can be manipulated to match the structure of EUV and SXR coronal loops. The objective is to derive sigmoidal magnetic field solutions which allows the beta greater than 1 regions to be included, aligned and non-aligned electric currents to be calculated, and the Lorentz force to be determined. The advantage of our technique is that the solution is independent of the unknown upper and side boundary conditions, allows non-vanishing magnetic forces, and provides a global magnetic field solution, which contains high- and low-beta regimes and is consistent with all the coronal images of the region. We show that the mathematical description is unique and physical.

Gary, G. Allan↗
NASA NTRS2001

Effect of acute exposure to hypergravity (GX vs. GZ) on dynamic cerebral autoregulation

We examined the effects of 30 min of exposure to either +3GX (front-to-back) or +GZ (head-to-foot) centrifugation on cerebrovascular responses to 80 degrees head-up tilt (HUT) in 14 healthy individuals. Both before and after +3 GX or +3 GZ centrifugation, eye-level blood pressure (BP(eye)), end tidal PCO2 (PET(CO2)), mean cerebral flow velocity (CFV) in the middle cerebral artery (transcranial Doppler ultrasound), cerebral vascular resistance (CVR), and dynamic cerebral autoregulatory gain (GAIN) were measured with subjects in the supine position and during subsequent 80 degrees HUT for 30 min. Mean BP(eye) decreased with HUT in both the GX (n = 7) and GZ (n = 7) groups (P < 0.001), with the decrease being greater after centrifugation only in the GZ group (P < 0.05). PET(CO2) also decreased with HUT in both groups (P < 0.01), but the absolute level of decrease was unaffected by centrifugation. CFV decreased during HUT more significantly after centrifugation than before centrifugation in both groups (P < 0.02). However, these greater decreases were not associated with greater increases in CVR. In the supine position after centrifugation compared with before centrifugation, GAIN increased in both groups (P < 0.05, suggesting an autoregulatory deficit), with the change being correlated to a measure of otolith function (the linear vestibulo-ocular reflex) in the GX group (r = 0.76, P < 0.05) but not in the GZ group (r = 0.24, P = 0.60). However, GAIN was subsequently restored to precentrifugation levels during postcentrifugation HUT (i.e., as BP(eye) decreased), suggesting that both types of centrifugation resulted in a leftward shift of the cerebral autoregulation curve. We speculate that this leftward shift may have been due to vestibular activation (especially during +GX) or potentially to an adaptation to reduced cerebral perfusion pressure during +GZ.

NASA Discipline Neuroscience↗