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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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NASA NTRS1975

An approach to high speed ship ride quality simulation

The high speeds attained by certain advanced surface ships result in a spectrum of motion which is higher in frequency than that of conventional ships. This fact along with the inclusion of advanced ride control features in the design of these ships resulted in an increased awareness of the need for ride criteria. Such criteria can be developed using data from actual ship operations in varied sea states or from clinical laboratory experiments. A third approach is to simulate ship conditions using measured or calculated ship motion data. Recent simulations have used data derived from a math model of Surface Effect Ship (SES) motion. The model in turn is based on equations of motion which have been refined with data from scale models and SES of up to 101 600-kg (100-ton) displacement. Employment of broad band motion emphasizes the use of the simulators as a design tool to evaluate a given ship configuration in several operational situations and also serves to provide data as to the overall effect of a given motion on crew performance and physiological status.

Malone, W. L.↗
NASA NTRS1976

Assessment of analytical and experimental techniques utilized in conducting plume technology tests 575 and 593

Since exhaust plumes affect vehicle base environment (pressure and heat loads) and the orbiter vehicle aerodynamic control surface effectiveness, an intensive program involving detailed analytical and experimental investigations of the exhaust plume/vehicle interaction was undertaken as a pertinent part of the overall space shuttle development program. The program, called the Plume Technology program, has as its objective the determination of the criteria for simulating rocket engine (in particular, space shuttle propulsion system) plume-induced aerodynamic effects in a wind tunnel environment. The comprehensive experimental program was conducted using test facilities at NASA's Marshall Space Flight Center and Ames Research Center. A post-test examination of some of the experimental results obtained from NASA-MSFC's 14 x 14-inch trisonic wind tunnel is presented. A description is given of the test facility, simulant gas supply system, nozzle hardware, test procedure and test matrix. Analysis of exhaust plume flow fields and comparison of analytical and experimental exhaust plume data are presented.

Baker, L. R.↗
NASA NTRS1976

Solid rocket booster thermal radiation model, volume 1

A solid rocket booster (SRB) thermal radiation model, capable of defining the influence of the plume flowfield structure on the magnitude and distribution of thermal radiation leaving the plume, was prepared and documented. Radiant heating rates may be calculated for a single SRB plume or for the dual SRB plumes astride the space shuttle. The plumes may be gimbaled in the yaw and pitch planes. Space shuttle surface geometries are simulated with combinations of quadric surfaces. The effect of surface shading is included. The computer program also has the capability to calculate view factors between the SRB plumes and space shuttle surfaces as well as surface-to-surface view factors.

Watson, G. H.↗
NASA NTRS1976

Comparisons of flight measurements with predictions from aeroelastic models in the NASA Langley Transonic Dynamics Tunnel

The NASA Langley Transonic Dynamics Tunnel, which has a variable density Freon-12 (or air) test medium, was designed for the study of dynamics and aeroelastic problems of aerospace vehicles. During the 15 years of operation of this facility there have been various opportunities to compare wind tunnel and flight test results. Some of these opportunities arise from routine flight checks of the prototype, others from carefully designed comparative wind tunnel and flight experiments. Data obtained from various sources is presented. The topics covered are: gust and buffet response, control surface effectiveness, flutter, and active control of aeroelastic effects. Some benefits and shortcomings of Freon-12 as a test medium are also discussed. Although areas of uncertainly are evident and there is a continuing need for improvements in model simulation and testing techniques, the results indicate that predictions from aeroelastic model tests are, in general, substantiated by full scale flight tests.

Reed, W. H., III↗
NASA NTRS1976

Digital adaptive control laws for the F-8

NASA is conducting a flight control research program in digital fly-by-wire technology using a modified F-8C aircraft. The first phase of this program used Apollo hardware to demonstrate the practicality of digital fly-by-wire in an actual test vehicle. For the second phase, conventional aircraft sensors and a large floating point digital computer are being utilized to test advanced control laws and redundancy concepts. As part of NASA's research in digital fly-by-wire technology, Honeywell developed digital adaptive flight control laws for flight test in the F-8C. Adaptation of the control laws was to be based on information sensed from conventional aircraft sensors excluding air data. The control laws were constrained to use only existing elevator, rudder, and ailerons as control effectors, each powered by existing actuators. Three adaptive control laws were successfully designed using maximum likelihood estimation, a Liapunov stable model tracker and a self-excited limit cycle concept. The maximum likelihood estimation design was selected as the most promising because of its capability to identify more than surface effectiveness parameters. The adaptive concepts, the control laws and comparisons of predicted performance are described.

Hartmann, G. L.↗
NASA NTRS1976

Correlation with flight of some aeroelastic model studies in the NASA Langley transonic dynamics tunnel

The NASA Langley transonic dynamics tunnel, which has a variable density Freon-12 (or air) test medium, was designed specifically for the study of dynamics and aeroelastic problems of aerospace vehicles. During the 15 years of operation of this facility, there have been various opportunities to compare wind tunnel and flight test results. Some of these opportunities arise from routine flight checks of the prototypes; others, from carefully designed comparative wind-tunnel and flight experiments. Such data obtained from various published and unpublished sources are presented. The topics covered are: gust and buffet response, control surface effectiveness, flutter, and active control of aeroelastic effects. Some benefits and shortcomings of Freon-12 as a test medium are also discussed. Although areas of uncertainty are evident and there is a continuing need for improvements in model simulation and testing techniques, the results presented indicate that predictions from aeroelastic model tests are, in general, substantiated by full scale flight tests.

Reed, W. H., III↗
NASA NTRS1977

Analytical study of viscous effects on transonic flow over boattail nozzles

An analytical study has been made of the effects of viscous/inviscid interactions on the transonic flow over boattail nozzles. The theoretical method couples a relaxation solution of the full potential transonic flow equations with a conventional boundary-layer solution to account for displacement-thickness effects. Surface pressures calculated on circular-arc boattails with solid jet-plume simulators show good agreement with experiment for free-stream Mach numbers less than 0.90. For separated flows, an empirical discriminating streamline model of the separation bubble gives good results until the onset of shock-induced separation, which occurs typically at a Mach number of about 0.90.

Wilmoth, R. G.↗
NASA NTRS1979

Coating for hot sliding seals

Heat resistant paint is effective surface coating for sliding seals that must operate at elevated temperatures. Economical paint is easy to apply, offers minimal friction, and improves reliability of seals.

Stock, J.↗
NASA NTRS1977

Investigation of conductive thermal control coatings by a contactless method in vacuo

A technique for determining the conductance per unit area of thermal control coatings for electrostatically clean spacecraft is described. In order to simulate orbital conditions more closely, current-density-voltage (j-V) curves are obtained by a contactless method in which the paint on an aluminum substrate is the anode of a vacuum diode configuration with a tungsten filament cathode. Conductances per unit area which satisfy the International Sun Earth Explorer (ISEE) requirement were observed on black paints containing carbon and in white and green paints filled with zinc oxide which were fired in order to induce defect conductivity. Because of surface effects and the nonhomogeneous nature of paints, large discrepancies were found between measurements with the contactless method and measurements employing metallic contacts, particularly at low current densities. Therefore, measurements with metallic contacts are considered to be of questionable value in deciding the suitability of coatings for electrostatic charge control.

Viehmann, W.↗
NASA NTRS1978

Mars - Regolith adsorption and the relative concentrations of atmospheric rare gases

Laboratory measurements of Kr and Xe adsorption on samples of ground montmorillonite, limonite and basalt at -77 C have been performed. Results suggest that (1) most degassed martian Xe could be adsorbed on a regolith with a large effective surface area, and (2) if this is the case the elemental composition of martian nonradiogenic rare gas (counting that in the regolith) may be virtually identical to that of ordinary chondrites.

Fanale, F. P.↗
NASA NTRS1975

Surface exposure history of individual crystals in the lunar regolith

The paper reports measurements of solar-flare tracks, microcraters, and glass accretionary particles in crystals from several mature soil samples and from different levels of the Apollo 15 and 16 deep drill stems. Although almost every crystal appears to have been at (or very near) the surface of the moon, the crater data indicate that typical grains are exposed to free space for only 1000-10,000 years. Neither total track densities nor track gradients are correlated with the presence of or absence of crater surfaces. Also considered is the use of cratered crystals in assessing the nature of surface changes produced by various treatments employed to study 'surface' effects.

Poupeau, G.↗
NASA NTRS1979

Flight test experience with an adaptive control system using a maximum likelihood parameter estimation technique

The flight test performance of an adaptive control system for the F-8 DFBW aircraft is summarized. The adaptive system is based on explicit identification of surface effectiveness parameters which are used for gain scheduling in a command augmentation system. Performance of this control law under various design parameter variations is presented. These include variations in test signal level, sample rate, and identification channel structure. Flight performance closely matches analysis and simulation predictions from previous references.

Hartmann, G.↗
NASA NTRS1979

Theoretical modelling and experimental data matching for active and passive microwave remote sensing of Earth terrain

Two theoretical models were developed to characterize terrain media: a random medium with a variance, a horizontal correlation length; and a homogeneous dielectric containing discrete scatterers. The earth terrain is modelled as layers of such scattering media bounded by air above and half-space below. Matching the theoretical results with experimental data collected from vegetation and snow-ice fields shows that: (1) for observation angles near nadir, rough surface effects are important; (2) for snow-ice field the horizontal correlation length is greater than the vertical correlation length whereas for vegetation field their relative sizes depend on the types of vegetation; (3) the vertically polarized backscattering cross-section is always larger than the horizontally polarized backscattering cross-section for half-space scattering media; (4) for snow field displaying diurnal change, a three-layer model including a thin top layer caused by sunlight illumination must be used; and (5) for a random medium with equal horizontal and vertical correlation lengths, the measured data can also be matched with a corresponding discrete scatterer model.

Kong, J. A.↗
NASA NTRS1976

Introductory study of the chemical behavior of jet emissions in photochemical smog

Jet aircraft emissions data from the literature were used as initial conditions for a series of computer simulations of photochemical smog formation in static air. The chemical kinetics mechanism used in these simulations was an updated version which contains certain parameters designed to account for hydrocarbon reactivity. These parameters were varied to simulate the reaction rate constants and average carbon numbers associated with the jet emissions. The roles of surface effects, variable light sources, NO/NO2 ratio, continuous emissions, and untested mechanistic parameters were also assessed. The results of these calculations indicate that the present jet emissions are capable of producing oxidant by themselves. The hydrocarbon/nitrous oxides ratio of present jet aircraft emissions is much higher than that of automobiles. These two ratios appear to bracket the hydrocarbon/nitrous oxides ratio that maximizes ozone production. Hence an enhanced effect is seen in the simulation when jet exhaust emissions are mixed with automobile emissions.

Whitten, G. Z.↗
NASA NTRS1980

A discussion of Cepheid masses

Masses and compositions of Cepheids are essential to map the places in the Hertzsprung-Russell diagram where various radial pulsation modes occur. Luminosity observations and stellar evolution theory give masses for Cepheids which range from 10 percent to a factor of four more than those given by pulsation theory. Combining the evolution and pulsation theories, a theoretical mass was determined using only the period and an approximate surface effective temperature. The ratio of the theoretical to evolutionary masses averaged 0.99 + or - 0.07 for 16 Cepheids.

Cox, A. N.↗
NASA NTRS1979

Photoelectron charge density and transport near differentially charged spacecraft

The effects of photoelectron space charge and current density on differentially charged spacecraft are studied. The steady-state potentials of a sunlit cylinder are calculated using a two-dimensional computer code with a fully self-consistent treatment of space charge and an effective surface conductivity treatment of photoelectron currents. It is found that under conditions of strong differential charging the results do not differ greatly from NASCAP results, which neglect photosheath space charge and currents.

Mandell, M. J.↗
NASA NTRS1980

Kinetics of the reaction OH + H2O2 yields HO2 + H2O

The paper describes an experimental study of the title reaction that uses the discharge-flow technique, laser-induced-fluorescence detection of OH and simultaneous monitoring of O and H atoms in the 250-459 K range. The reaction is normal and free from surface effect interference in Teflon or halocarbon wax-coated tube, but not in clean Pyrex. OH radicals are generated in three ways and at low concentrations to eliminate side reactions. The rate constants were determined at 298 K and over the 250-459 K range, with a factor of two higher at 298 K and factors of 3 to 5 higher at 10 to 30 km altitude in the terrestrial atmosphere than previous studies have indicated. The effect of the higher rate constant on atmospheric processes and on recent laboratory measurements of other reactions is also discussed.

Sridharan, U. C.↗
NASA NTRS1982

Bearings: Technology and needs

A brief status report on bearing technology and present and near-term future problems that warrant research support is presented. For rolling element bearings a material with improved fracture toughness, life data in the low Lambda region, a comprehensive failure theory verified by life data and incorporated into dynamic analyses, and an improved corrosion resistant alloy are perceived as important needs. For hydrodynamic bearings better definition of cavitation boundaries and pressure distributions for squeeze film dampers, and geometry optimization for minimum power loss in turbulent film bearings are needed. For gas film bearings, foil bearing geometries that form more nearly optimum film shapes for maximum load capacity, and more effective surface protective coatings for high temperature operation are needed.

Anderson, W. J.↗