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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Fundamental plasma emission involving ion sound waves

The theory for fundamental plasma emission by the three-wave processes L + or - S to T (where L, S and T denote Langmuir, ion sound and transverse waves, respectively) is developed. Kinematic constraints on the characteristics and growth lengths of waves participating in the wave processes are identified. In addition the rates, path-integrated wave temperatures, and limits on the brightness temperature of the radiation are derived.

Cairns, Iver H.↗
NASA NTRS1988

Temperature dependence of the hydrogen-broadening coefficient for the nu 9 fundamental of ethane

Experimental results for the temperature dependence of the H2-broadening coefficient for the nu 9 fundamental of ethane are reported. Measurements were made over the temperature range 95-300 K using a novel low-temperature absorption cell. These spectra were recorded with the Doppler-limited diode laser spectrometer at NASA Goddard. The results are compared with recent measurements and model predictions.

Halsey, G. W.↗
NASA NTRS1988

Autonomous control systems - Architecture and fundamental issues

A hierarchical functional autonomous controller architecture is introduced. In particular, the architecture for the control of future space vehicles is described in detail; it is designed to ensure the autonomous operation of the control system and it allows interaction with the pilot and crew/ground station, and the systems on board the autonomous vehicle. The fundamental issues in autonomous control system modeling and analysis are discussed. It is proposed to utilize a hybrid approach to modeling and analysis of autonomous systems. This will incorporate conventional control methods based on differential equations and techniques for the analysis of systems described with a symbolic formalism. In this way, the theory of conventional control can be fully utilized. It is stressed that autonomy is the design requirement and intelligent control methods appear at present, to offer some of the necessary tools to achieve autonomy. A conventional approach may evolve and replace some or all of the `intelligent' functions. It is shown that in addition to conventional controllers, the autonomous control system incorporates planning, learning, and FDI (fault detection and identification).

Antsaklis, P. J.↗
NASA NTRS1988

Fundamental kinetics and mechanistic pathways for oxidation reactions in supercritical water

Oxidation of the products of human metabolism in supercritical water has been shown to be an efficient way to accomplish the on-board water/waste recycling in future long-term space flights. Studies of the oxidation kinetics of methane to carbon dioxide in supercritical water are presented in this paper in order to enhance the fundamental understanding of the oxidation of human waste compounds in supercritical water. It is concluded that, although the elementary reaction models remain the best hope for simulating oxidation in supercritical water, several modifications to existing mechanisms need to be made to account for the role of water in the reaction mechanism.

Webley, Paul A.↗
NASA NTRS1989

Measurements of collision-broadened line widths in the nu4-fundamental band of (C-12)H4 at low temperatures

Collision-broadened half-widths of several lines in the nu4 fundamental band of (C-12)H4 have been measured at low temperatures between 130 and 295 K using a tunable diode laser and the sweep integration technique. The broadening gases are H2, N2, He, and Ar. The temperature dependence of the measured line widths is described in terms of an exponent n, which is shown not only to be different for each broadening gas but also to depend upon the tetrahedral symmetry identification of the lines of CH4.

Varanasi, P.↗
NASA NTRS1989

Tunable diode laser measurements of line widths in the nu1-fundamental band of (N-14)2(O-16) at atmospheric temperatures

A tunable diode-laser spectrometer and a low-temperature absorption cell have been employed to measure the N2-broadened and O2-broadened half-widths of rotational lines in the nu1 fundamental band of (N-14)2(O-16) at 185, 235, 263, and 295 K. The temperature dependence of the line widths has been observed to be practically identical, thereby leading to the suggestion that air-broadening would exhibit the same dependence.

Varanasi, P.↗
NASA NTRS1988

Fundamental principles of hollow-cathode-discharge operations in space and the design of a rocket-borne demonstration

The issue of hollow-cathode operations in space is treated from the point of view of fundamental principles of plasma interactions and their control over currents involving the device, the spaceborne vehicle, and the ambient space plasma. Particular attention is given to collective plasma processes, the effects of the ambient magnetic field, and the high probability of plasma turbulence triggered by hallow cathode operations. The paper presents a rocket payload and experiment scenario designed for accommodation on a Black Brant booster, launched from a midlatitude site to an apogee in excess of 400 km.

Szuszczewicz, Edward P.↗
NASA NTRS1989

Intensity and line width measurements in the nu(u) fundamental band of (C-13)H4

Intensities and collision-broadened line widths have been measured in the nu(u) fundamental band of (C-13)H4 at 295 K, employing the Doppler-limited spectral resolution of a tunable diode laser spectrometer and a (C-13)-enriched sample of CH4, H2, He, Ar, N2, O2, and air were chosen as the broadening gases in order to provide the data needed in atamospheric and planetary atamospheric applications.

Varanasi, Prasad↗
NASA NTRS1990

Compact scheme for systems of equations applied to fundamental problems of mechanics of continua

Compact scheme formulation was used in the treatment of boundary conditions for a system of coupled diffusion and Poisson equations. Models and practical solutions of specific engineering problems arising in solid mechanics, chemical engineering, heat transfer and fuid mechanics are described and analyzed for efficiency and accuracy. Only 2-D cases are discussed and a new method of numerical treatment of boundary conditions common in the fundamental problems of mechanics of continua is presented.

Klimkowski, Jerzy Z.↗
NASA NTRS1989

Fundamentals of tribology at the atomic level

Tribology, the science and engineering of solid surfaces in moving contact, is a field that encompasses many disciplines: solid state physics, chemistry, materials science, and mechanical engineering. In spite of the practical importance and maturity of the field, the fundamental understanding of basic phenomena has only recently been attacked. An attempt to define some of these problems and indicate some profitable directions for future research is presented. There are three broad classifications: (1) fluid properties (compression, rheology, additives and particulates); (2) material properties of the solids (deformation, defect formation and energy loss mechanisms); and (3) interfacial properties (adhesion, friction chemical reactions, and boundary films). Research in the categories has traditionally been approached by considering macroscopic material properties. Recent activity has shown that some issues can be approached at the atomic level: the atoms in the materials can be manipulated both experimentally and theoretically, and can produce results related to macroscopic phenomena.

Ferrante, John↗
NASA NTRS1989

Numerical results on relations between fundamental constants using a new algorithm

An efficient algorithm is described for finding whether or not certain fundamental mathematical constants satisfy simple algebraic polynomials. The algorithm, which finds whether an integer relation exists for a vector of real numbers, or else establishes bounds within which no relation can exist. The algorithm is implemented on high-speed computers, using multiprecision arithmetic. Numerical results are summarized, and other possible applications for the algorithm are discussed.

Bailey, David H.↗
NASA NTRS1990

A new computation of the infrared absorption by H2 pairs in the fundamental band at temperatures from 600 to 5000 K

A new computation of the absorption spectrum of H2 pairs in the fundamental band is given for temperatures from 600 to 5000 K. It is based on advanced interaction potentials and recent induced dipole components which were shown to be consistent with the existing laboratory measurements of low-temperature absorption spectra. The absorption is greater by factors of 2-3 than previous estimates and show a different band profile at the higher temperatures.

Borysow, Aleksandra↗
NASA NTRS1990

N2-broadening in the HCl vibrational fundamental - Temperature dependence between 160 and 296 K

Measurements were conducted of the N2-broadening coefficients in the vibrational fundamental line of HCl at 160, 182, 216, 255, and 296 K. It is found that the N2 broadening of rovibrational lines in the -6 to +6 range is well described by a simple power-law dependence on temperature. The temperature-interpolation of these results is noted to be in good agreement with previous low-temperature studies.

Chackerian, C., Jr.↗
NASA NTRS1990

Cepheids in Magellanic Cloud star clusters - Fundamental and overtone pulsators in NGC 2157

CCD survey data are employed to examine Cepheids in young Magellanic Cloud star clusters. The properties of three Cepheids observed in NGC 2157 are described. It is detected that the two short-period (3 days) Cepheids have photometric properties that correspond to overtone pulsators and the long-period (7.7 days) Cepheid pulses in the fundamental mode. The pulsational masses for the three Cepheids are calculated to be about 5 solar masses. This mass value does not correlate with the average pulsational mass for Cepheids of 3.0 + or - 0.4 solar masses. The potential cause of this deviation in evolutionary/pulsational mass is investigated.

Mateo, Mario↗
NASA NTRS1990

Fundamentals of chemistry modeling applicable to a vectorized particle simulation

This paper describes the fundamentals of extending the vectorized particle simulation method derived by Baganoff and McDonald (1990), McDonald and Baganoff (1988), and McDonald (1989) for modeling chemically reacting flows. Details of reaction mechanics per reaction are presented, with particular attention given to the quantum nature of the vibrational mode. The models of reactive flows developed here were verified through a simulation of a superheated diatomic gas relaxing thermochemically to equilibrium in a reservoir.

Haas, Brian L.↗
NASA NTRS1991

Infrared laser absorption spectroscopy of the nu4 (sigma u) fundamental and associated nu11(pi u) hot band of C7 - Evidence for alternating rigidity in linear carbon clusters

The first characterization of the bending potential of the C7 cluster is reported via the observation of the v = 1(1) and v = 2 deg levels of the nu11 (pi u) bend as hot bands associated with the nu4 (sigma u) antisymmetric stretch fundamental. The lower state hot band rotational constants are measured to be 1004.4(1.3) and 1123.6(9.0) MHz, constituting a 9.3 and 22 percent increase over the ground state rotational constant, 918.89 (41) MHz. These large increases are strong quartic and sextic centrifugal distortion constants determined for the ground and nu 4 = 1 states are found to be anomalously large and negative, evidencing strong perturbations between stretching and bending modes.

Heath, J. R.↗
NASA NTRS1990

Fundamental considerations in adhesion, friction and wear for ceramic-metal contacts

Fundamental studies of friction, wear and adhesion of ceramics in contact with metals are evaluated. It is shown that friction and adhesion are strongly dependent on the ductility of the metals. The surface energy, friction, adhesion and hardness of a metal are related to its Young's modulus and shear modulus, which have a marked dependence on the electron configuration of the metal. Generally, the greater the sheer modulus, the less metal transfer there is to the ceramic.

Miyoshi, Kazuhisa↗