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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Lunar and Planetary Science XXXVI, Part 18

Topics discussed include: PoDS: A Powder Delivery System for Mars In-Situ Organic, Mineralogic and Isotopic Analysis Instruments Planetary Differentiation of Accreting Planetesimals with 26Al and 60Fe as the Heat Sources Ground-based Observation of Lunar Surface by Lunar VIS/NIR Spectral Imager Mt. Oikeyama Structure: First Impact Structure in Japan? Central Mounds in Martian Impact Craters: Assessment as Possible Perennial Permafrost Mounds (Pingos) A Further Analysis of Potential Photosynthetic Life on Mars New Insight into Valleys-Ocean Boundary on Mars Using 128 Pixels per Degree MOLA Data: Implication for Martian Ocean and Global Climate Change; Recursive Topography Based Surface Age Computations for Mars: New Insight into Surficial Processes That Influenced Craters Distribution as a Step Toward the Formal Proof of Martian Ocean Recession, Timing and Probability; Laser-induced Breakdown Spectroscopy: A New Method for Stand-Off Quantitative Analysis of Samples on Mars; Milk Spring Channels Provide Further Evidence of Oceanic, >1.7-km-Deep Late Devonian Alamo Crater, Southern Nevada; Exploration of Martian Polar Residual Caps from HEND/ODYSSEY Data; Outflow Channels Influencing Martian Climate: Global Circulation Model Simulations with Emplaced Water; Presence of Nonmethane Hydrocarbons on Pluto; Difference in Degree of Space Weathering on the Newborn Asteroid Karin; Circular Collapsed Features Related to the Chaotic Terrain Formation on Mars; A Search for Live (sup 244)Pu in Deep-Sea Sediments: Preliminary Results of Method Development; Some Peculiarities of Quartz, Biotite and Garnet Transformation in Conditions of Step-like Shock Compression of Crystal Slate; Error Analysis of Remotely-Acquired Mossbauer Spectra; Cloud Activity on Titan During the Cassini Mission; Solar Radiation Pressure and Transient Flows on Asteroid Surfaces; Landing Site Characteristics for Europa 1: Topography; and The Crop Circles of Europa.

Source record↗
NASA NTRS1991

Differential collision cross-sections for atomic oxygen: Analysis of space flight instruments for solar terrestrial physics

A summary of the status of the Cross-section Facility at MSFC is presented. A facility was designed, fabricated, assembled, tested, and operated for measurement of differential scattering cross sections important to understand the induced environment for a vehicle (e.g., Space Station) in low earth orbit. A user's manual for the facility is also presented. The performance of the facility was evaluated and found to be satisfactory in all the essential areas. Differential scattering cross sections were measured and results for the scattering measurements are included. Input to the development of the Ultraviolet Imager Optical System is also discussed. Design, fabrication, and evaluation of UV filters using a four-layer aluminum base are reported.

Torr, Douglas G.↗
NASA NTRS2006

Thermal Analysis of Post-eruption Loops from 80,000 to 1.6 million K

We analyze the thermal properties of a set of post eruptive loops which appeared after a prominence eruption on April 30, 2004. The event was observed by TRACE and SOHO/SUMER. The SUMER data was taken from a single slit location with a 90 second cadence and included a number of lines spanning the temperature range 80,000 to 1.6 million K. We perform a differential emission measure analysis of the loops in order to study their thermal evolution.

Kucera, T.↗
NASA NTRS1994

ASTM E 1559 method for measuring material outgassing/deposition kinetics has applications to aerospace, electronics, and semiconductor industries

The American Society for Testing and Materials has published a new standard test method for characterizing time and temperature-dependence of material outgassing kinetics and the deposition kinetics of outgassed species on surfaces at various temperatures. This new ASTM standard, E 1559(1), uses the quartz crystal microbalance (QCM) collection measurement approach. The test method was originally developed under a program sponsored by the United States Air Force Materials Laboratory (AFML) to create a standard test method for obtaining outgassing and deposition kinetics data for spacecraft materials. Standardization by ASTM recognizes that the method has applications beyond aerospace. In particular, the method will provide data of use to the electronics, semiconductor, and high vacuum industries. In ASTM E 1559 the material sample is held in vacuum in a temperature-controlled effusion cell, while its outgassing flux impinges on several QCM's which view the orifice of the effusion cell. Sample isothermal total mass loss (TML) is measured as a function of time from the mass collected on one of the QCM's which is cooled by liquid nitrogen, and the view factor from this QCM to the cell. The amount of outgassed volatile condensable material (VCM) on surfaces at higher temperatures is measured as a function of time during the isothermal outgassing test by controlling the temperatures of the remaining QCM's to selected values. The VCM on surfaces at temperatures in between those of the collector QCM's is determined at the end of the isothermal test by heating the QCM's at a controlled rate and measuring the mass loss from the end of the QCM's as a function of time and temperature. This reevaporation of the deposit collected on the QCM's is referred to as QCM thermogravimetric analysis. Isothermal outgassing and deposition rates can be determined by differentiating the isothermal TML and VCM data, respectively, while the evaporation rates of the species can be obtained as a function of temperature by differentiating the QCM thermogravimetric analysis data.

Garrett, J. W.↗
NASA NTRS1987

Factorization and the synthesis of optimal feedback kernels for differential-delay systems

A combination of ideas from the theories of operator Riccati equations and Volterra factorizations leads to the derivation of a novel, relatively simple set of hyperbolic equations which characterize the optimal feedback kernel for the finite-time regulator problem for autonomous differential-delay systems. Analysis of these equations elucidates the underlying structure of the feedback kernel and leads to the development of fast and accurate numerical methods for its computation. Unlike traditional formulations based on the operator Riccati equation, the gain is characterized by means of classical solutions of the derived set of equations. This leads to the development of approximation schemes which are analogous to what has been accomplished for systems of ordinary differential equations with given initial conditions.

Milman, Mark M.↗
NASA NTRS1984

Communications-imposed pilot workload - A comparison of sixteen estimation techniques

Sixteen potential metrics of mental workload were investigated in regard to their relative sensitivity to communications load and their differential intrusion on primary task performance. A moving-base flight simulator was used to present three cross-country flights to each of 30 subject pilots, each flight varying only in the difficulty of the inherent communications requirements. With the exception of the rating scale measures, which were obtained immediately post-flight, all measures were taken over a seven minute segment of the flight task. The results indicated that both the Modified Cooper-Harper and the workload Multi-descriptor rating scales were reliably sensitive to changes in communications load. Also, the secondary task measure of time estimation and the physiological measure of pupil diameter yielded sensitivity. As expected, those primary task measures which were direct measures of communicative performance were also sensitive to load, while aircraft control primary task measures were not, attesting to the task-specificity of such measures. Finally, the intrusion analysis revealed no differential interference between workload measures.

Casali, J. G.↗
NASA NTRS1969

Rapid and precise analysis for calcium in blood serum

Differential absorption spectrophotometric technique, using murexide, gives a highly precise analysis of calcium in volumes of blood serum as small as 0.01 ml. The method of additions and proper timing allows compensation to be made for fading, variation in type of serum or plasma, and aging of the specimen.

Holtzman, R. B.↗
NASA NTRS1979

Stability of sequences generated by nonlinear differential systems

A local stability analysis is presented for both the analytic and numerical solutions of the initial value problem for a system of ordinary differential equations. It is shown that, using a proper choice of Liapunov function, a connected region of stable initial values of both the analytic solution and the one-leg k-step numerical solution can be approximated. Attention is given to the example of the two-dimensional problem involving the stability of the longitudinal equations of motion of a gliding jet aircraft.

Brown, R. L.↗
NASA NTRS1972

Interstellar propagation of galactic cosmic-ray nuclei 2 less than or equal to Z less than or equal to 8 in the energy range 10 to 1000 MeV per nucleon.

Analysis of the differential kinetic energy per nucleon spectra of galactic cosmic-ray He, Li, Be, B, C, N, and O with the University of Chicago cosmic-ray telescope on board the IMP-5 satellite in 1969-1970. The ratios He/(C + N + O) and (Li + Be + B)/(C + N + O) obtained from these spectra are found, within errors of about 20%, to be energy-independent over the energy range 10-1000 MeV per nucleon, and equal to about 15 and about 0.25, respectively. These results are compared with discrepancies existing among other measurements of these ratios, and with predictions of a class of steady-state models of cosmic-ray propagation which assume that Li, Be, and B are absent in cosmic-ray sources. The best fits for the present measurements are obtained for models with a source spectrum in the form of a power law in total energy per nucleon, but even these fits are outside the error limits at energies below 100 MeV per nucleon. In the context of the propagation models examined, it is concluded that the observed behavior of these ratios requires an additional mechanism operative at low energies. This mechanism may be adiabatic deceleration of cosmic rays in the solar wind. In order for this mechanism to be adiabatic deceleration, the deceleration in 1969 must have been such that particles observed at 10 to 20 MeV per nucleon had energies greater than 100 to 150 MeV per nucleon in the local interstellar space.

Mason, G. M.↗
NASA NTRS1975

Nonlinear seismic analysis of a reactor structure impact between core components

The seismic analysis of the FFTF-PIOTA (Fast Flux Test Facility-Postirradiation Open Test Assembly), subjected to a horizontal DBE (Design Base Earthquake) is presented. The PIOTA is the first in a set of open test assemblies to be designed for the FFTF. Employing the direct method of transient analysis, the governing differential equations describing the motion of the system are set up directly and are implicitly integrated numerically in time. A simple lumped-nass beam model of the FFTF which includes small clearances between core components is used as a "driver" for a fine mesh model of the PIOTA. The nonlinear forces due to the impact of the core components and their effect on the PIOTA are computed.

Hill, R. G.↗
NASA NTRS1976

Historical evolution of vortex-lattice methods

A review of the beginning and some orientation of the vortex-lattice method were given. The historical course of this method was followed in conjunction with its field of computational fluid dynamics, spanning the period from L.F. Richardson's paper in 1910 to 1975. The following landmarks were pointed out: numerical analysis of partial differential equations, lifting-line theory, finite-difference method, 1/4-3/4 rule, block relaxation technique, application of electronic computers, and advanced panel methods.

Deyoung, J.↗
NASA NTRS1982

Survey of new vector computers: The CRAY 1S from CRAY research; the CYBER 205 from CDC and the parallel computer from ICL - architecture and programming

Problems which can arise with vector and parallel computers are discussed in a user oriented context. Emphasis is placed on the algorithms used and the programming techniques adopted. Three recently developed supercomputers are examined and typical application examples are given in CRAY FORTRAN, CYBER 205 FORTRAN and DAP (distributed array processor) FORTRAN. The systems performance is compared. The addition of parts of two N x N arrays is considered. The influence of the architecture on the algorithms and programming language is demonstrated. Numerical analysis of magnetohydrodynamic differential equations by an explicit difference method is illustrated, showing very good results for all three systems. The prognosis for supercomputer development is assessed.

Gentzsch, W.↗
NASA NTRS1983

The atmosphere of Titan - An analysis of the Voyager 1 radio occultation measurements

The equatorial atmosphere of Titan was probed by means of two coherently related radio signals transmitted from Voyager 1 at 13.0 and 3.6 cm wavelengths during the November 12, 1980 occultation of the spacecraft by the Saturn satellite. An analysis of the differential dispersive frequency measurements did not reveal any ionization layers in the upper atmosphere of Titan. The gas refractivity data, which extend from the surface to about 200 km altitude, were interpreted in two different ways. In the first, it is assumed that N2 makes up virtually all of the atmosphere, with small amounts of CH4 and other hydrocarbons present. In the second interpretation of the refractivity data, it is assumed that the 3.5 km altitude level corresponds to the bottom of a CH4 cloud layer and that N2 and CH4 were perfectly mixed below this level.

Lindal, G. F.↗