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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Techniques for aerothermal tests of large, flightweight thermal protection panels in a Mach 7 wind tunnel

Recently developed experimental techniques permit evaluating thermal performance and structural integrity of full-scale panel concepts applicable to reentry and hypersonic vehicles in the Langley 8-foot high-performance structures tunnel. Rate and magnitude of surface heating and differential-pressure loading are independently controlled. Realistic temperature distributions are radiantly preheated into the panel prior to aerodynamic heating, and stream conditions are preselected to sustain the preheat surface heating input during aerodynamic exposure. During tunnel start and shutdown, panels are shielded outside the stream from potentially damaging transient acoustics and buffeting and are then rapidly inserted into the hypersonic flow. Infrared radiometry provides detailed surveys of surface temperatures.

Deveikis, W. D.↗
NASA NTRS1977

Sublimator/evaporator heat sink

Economical self-regulating device cools liquids by evaporating portion of liquid through porous tubes. Technique is characterized by high heat transfer rate and structural simplicity.

Webbon, B. W.↗
NASA NTRS1980

The photometric properties of brightest cluster galaxies. II - SIT and CCD surface photometry

Surface photometry of the first-ranked galaxy in 108 Abell clusters is presented. Galaxy structure, as parameterized by simple Hubble law models, is found to correlate with galaxy absolute magnitude and cluster structure. All the structure data support the dynamical friction evolution model. Twenty-eight percent of the galaxies have multiple component nuclei; the short lifetimes of such systems provide the best available evidence that ongoing evolution actually occurs. Average magnitude and structure evolution rates are derived from the data.

Hoessel, J. G.↗
NASA NTRS1982

Exploration of the asteroids

A mission to an earth-crossing asteroid would be useful to avert a threatened collision, to utilize its resources, or for scientific investigations. Realizable launch opportunities to 1943 Anteros occur about every two years, and the 1987 and 1990 opportunities are being extensively studied. The mission craft would carry remote sensing instruments and obtain the shape, size, surface structure, rotation rate, axis of rotation and color differences of the asteroid. The chemical composition of the surface and the gravitational field would be studied. Although a free fall landing on the surface is feasible, a soft landing that takes account of the asteroid's gravity and rotation is desirable. In situ experiments would be accomplished with the aid of a penetrator fired from a tube on the mother spacecraft with the penetrator carrying an accelerometer, alpha-scattering device, water detector, magnetometer and seismometer.

French, J. R., Jr.↗
NASA NTRS1983

Structures and subsystems

New and improved materials combined with efficient structural design concepts have made an essential contribution towards the shaping of the present transportation system (STS), and now, for the replacement of the STS in the year 2005, new materials and novel designs are being studied to identify the technologies which should be developed for a low-cost future space transportation system (FSTS). Three basic structural arrangements were considered for the FSTS orbiter. They include a nonintegral tank arrangement, an integral-tank arrangement, and a hybrid of the first two. Three representative arrangements regarding wall constructions are considered. Each employs a blade-stiffened aluminum tank with reinforced closed-cell-foam cryogenic insulation. Attention is given to an aluminum-alloy structure, a graphite-epoxy structure, a graphite-polyimide structure, a carbon-carbon surface panel structure, a graphite-composite fuselage structure, serviceability and all-weather considerations, and structural concept ratings.

Taylor, A. H.↗
NASA NTRS1985

Fatigue criterion to system design, life and reliability

A generalized methodology to structural life prediction, design, and reliability based upon a fatigue criterion is advanced. The life prediction methodology is based in part on work of W. Weibull and G. Lundberg and A. Palmgren. The approach incorporates the computed life of elemental stress volumes of a complex machine element to predict system life. The results of coupon fatigue testing can be incorporated into the analysis allowing for life prediction and component or structural renewal rates with reasonable statistical certainty.

Zaretsky, E. V.↗
NASA NTRS1985

Fatigue criterion to system design, life and reliability

A generalized methodology to structural life prediction, design, and reliability based upon a fatigue criterion is advanced. The life prediction methodology is based in part on work of Weibull and Lundberg and Palmgren. The approach incorporates the computed life of elemental stress volumes of a complex machine element to predict system life. The results of coupon fatigue testing can be incorporated into the analysis allowing for life prediction and component or structural renewal rates with reasonable statistical certainty.

Zaretsky, E. V.↗
NASA NTRS1986

Fatigue Criterion for System Design

Report discusses principles of structural-life prediction. Generalized methodology developed for structural life prediction, design, and reliability, based upon fatigue criterion. Approach incorporates computed life of elemental stress volumes of complex machine elements to predict system life. Results of coupon fatigue testing incorporated into analysis, allowing for life prediction and component or structural renewal rates, with reasonable statistical certainty.

Zeretsky, E. V.↗
NASA NTRS1985

Skylab observations of the solar O I resonance triplet

Profile variations from center to limb, as well as at different heights above the quiet solar limb, are illustrated by profile observations of the solar O I resonant triplet at 1302, 1304, and 1306 A that were obtained with the Skylab S082-B spectrograph. Since these lines share a common upper energy level, source function equality should exist for them when the lower states are populated according to their statistical weights. Profile congruency and profile inversion calculations comparisons show, however, that this is not the case, suggesting either errors in the fine structure collision rates, or the H I Ly-beta flux preferentially depopulating the 1302 A lower level, or two-dimensional transfer effects.

Roussel-Dupre, D.↗
NASA NTRS1987

A combined stochastic feedforward and feedback control design methodology with application to autoland design

A combined stochastic feedforward and feedback control design methodology was developed. The objective of the feedforward control law is to track the commanded trajectory, whereas the feedback control law tries to maintain the plant state near the desired trajectory in the presence of disturbances and uncertainties about the plant. The feedforward control law design is formulated as a stochastic optimization problem and is embedded into the stochastic output feedback problem where the plant contains unstable and uncontrollable modes. An algorithm to compute the optimal feedforward is developed. In this approach, the use of error integral feedback, dynamic compensation, control rate command structures are an integral part of the methodology. An incremental implementation is recommended. Results on the eigenvalues of the implemented versus designed control laws are presented. The stochastic feedforward/feedback control methodology is used to design a digital automatic landing system for the ATOPS Research Vehicle, a Boeing 737-100 aircraft. The system control modes include localizer and glideslope capture and track, and flare to touchdown. Results of a detailed nonlinear simulation of the digital control laws, actuator systems, and aircraft aerodynamics are presented.

Halyo, Nesim↗
NASA NTRS1987

The rotation rate of Uranus, its internal structure, and the process of planetary accretion

It is investigated whether Uranus models with higher values of the total planetary ice to rock ratio (I/R) can be made consistent with the rotation period of 17.24 hr. measured by Voyager 2, and with the 16-pole moment of the gravitational field (J4) derived from the observations of French et al. (1986). An atmospheric enhancement of H2O, NH3, and CH4 of not more than about 30 times the solar value, and an I/R value of greater than 16, are implied by these models. A planetary accretion scenario whereby such I/R values are possible for a large range of planetesimal radii and initial velocities is discussed.

Podolak, M.↗
NASA NTRS1987

Ozone measurements of the NASA-JSC U.V. photometer during the MAP/GLOBUS campaign of 1983

Results of the NASA-JSC UV photometer from flights on large balloons during the MAP/GLOBUS campaing of September 1983 are reported. Profiles obtained on September 14 and 24 agree within uncertainties above a height of 36 mb (about 22.5 km) indicating a degree of stability in the upper stratosphere. Measurements were made during ascent and descent of the first flight, and ascent of the second flight. Because the vertical descent rate of the first flight was five times lower than the ascent rate, more structure was obtained. Float altitudes of 32 km (8.1 mb) for the first flight and 39 km (3.1 mb) for the second flight were attained. Results from the photometer are compared with Nimbus 7 SBUV observations made at the same time. The profiles agree within 10 percent above the partial pressure peak. Above the ozone mixing ratio peak, the UV photometry values are about 1 ppmV lower for the second flight. The SBUV profile peak is 1-2 km higher in altitude than that of the UV photometer. Peak values agree within about 4 percent.

Robbins, Donald E.↗
NASA NTRS1987

Pioneer Venus measurements of H, O, and C production in comet P/Halley near perihelion

The Pioneer Venus Orbiter Ultraviolet Spectrometer measured the production of H, O, and C in comet Halley from late December 1985 to early March 1986. Water production rates obtained from the H data rose from 3.3 x 10 to the 29th/s at 1 AU inbound to 1.2 x 10 to the 30th/s at perihelion; there was a further increase to 1.6 x 10 to the 30th/s followed by a slow decline to 1.4 x 10 to the 30th/s at the time of the Vega-1 encounter. The H measurements show a periodic behavior that imply variations in the water production rate having structure within a 7.4-day sidereal period, in phase with similar variations seen in radical and dust production in March and April. Average H:O:C ratios of 1.0:0.7:0.07 were measured from 10 to 26 days after perihelion.

Stewart, A. I. F.↗
NASA NTRS1987

DACS II - A distributed thermal/mechanical loads data acquisition and control system

A distributed data acquisition and control system has been developed for the NASA Flight Loads Research Facility. The DACS II system is composed of seven computer systems and four array processors configured as a main computer system, three satellite computer systems, and 13 analog input/output systems interconnected through three independent data networks. Up to three independent heating and loading tests can be run concurrently on different test articles or the entire system can be used on a single large test such as a full scale hypersonic aircraft. Thermal tests can include up to 512 independent adaptive closed loop control channels. The control system can apply up to 20 MW of heating to a test specimen while simultaneously applying independent mechanical loads. Each thermal control loop is capable of heating a structure at rates of up to 150 F per second over a temperature range of -300 to +2500 F. Up to 64 independent mechanical load profiles can be commanded along with thermal control. Up to 1280 analog inputs monitor temperature, load, displacement and strain on the test specimens with real time data displayed on up to 15 terminals as color plots and tabular data displays. System setup and operation is accomplished with interactive menu-driver displays with extensive facilities to assist the users in all phases of system operation.

Zamanzadeh, Behzad↗
NASA NTRS1989

Structural comparison of nickel electrodes and precursor phases

A summary of previous Raman spectroscopic results and a discussion of important structural differences in the various phases of active mass and active mass precurors are presented. Raman spectra provide unique signatures for these phases, and allow one to distinguish each phase, even when the compound is amorphous to X-rays (i.e., does not scatter X-rays because of a lack of order and/or small particle size). The structural changes incurred during formation, charge and discharge, cobalt addition, and aging will be discussed and related to electrode properties. Important structural differences include NiO2 layer stacking, nonstoichiometry (especially cation-deficit nonstoichiometry), disorder, dopant content, and water content. The results indicate that optimal nickel active mass is non-close packed and nonstoichiometric. The formation process transforms precursor phases into this structure. Therefore, the precursor disorder, or lack thereof, influences this final active mass structure and the rate of formation. Aging processes induce structural change which is believed to be detrimental. The role of cobalt addition can be appreciated in terms of structures favored or stabilized by the dopant. In recent work, the in situ Raman technique to characterize the critical structural parameters was developed. An in situ method relates structure, electrochemistry, and preparation. In situ Raman spectra of cells during charge and discharge, either during cyclic voltammetry or under constant current conditions were collected. With the structure-preparation knowledge and the in situ Raman tool, it will be possible to define the structure-property-preparation relations in more detail. This instrumentation has application to a variety of electrode systems.

Cornilsen, Bahne C.↗
NASA NTRS1989

Feasibility of reduced gravity experiments involving quiescent, uniform particle cloud combustion

The study of combustible particle clouds is of fundamental scientific interest as well as a practical concern. The principal scientific interests are the characteristic combustion properties, especially flame structure, propagation rates, stability limits, and the effects of stoichiometry, particle type, transport phenomena, and nonadiabatic processes on these properties. The feasibility tests for the particle cloud combustion experiment (PCCE) were performed in reduced gravity in the following stages: (1) fuel particles were mixed into cloud form inside a flammability tube; (2) when the concentration of particles in the cloud was sufficiently uniform, the particle motion was allowed to decay toward quiescence; (3) an igniter was energized which both opened one end of the tube and ignited the suspended particle cloud; and (4) the flame proceeded down the tube length, with its position and characteristic features being photographed by high-speed cameras. Gravitational settling and buoyancy effects were minimized because of the reduced gravity enviroment in the NASA Lewis drop towers and aircraft. Feasibility was shown as quasi-steady flame propagation which was observed for fuel-rich mixtures. Of greatest scientific interest is the finding that for near-stoichiometric mixtures, a new mode of flame propagation was observed, now called a chattering flame. These flames did not propagate steadily through the tube. Chattering modes of flame propagation are not expected to display extinction limits that are the same as those for acoustically undisturbed, uniform, quiescent clouds. A low concentration of fuel particles, uniformly distributed in a volume, may not be flammable but may be made flammable, as was observed, through induced segregation processes. A theory was developed which showed that chattering flame propagation was controlled by radiation from combustion products which heated the successive discrete laminae sufficiently to cause autoignition.

Ross, Howard D.↗
NASA NTRS1992

A model of the ionosphere of Titan

A 1D model is developed to study both the composition and density of Titan's structure. Ionization rates due both to photoionization by solar EUV flux and to electron impact ionization by photoelectrons and Saturnian magnetospheric electrons are included. The major neutral species (nitrogen and methane) are ionized to produce N2(+), N(+), CH4(+), CH3(+), CH2(+), and CH(+) ions. The total external pressure upstream of Titan at the time of the Voyager encounter is of the order of the maximum ionospheric thermal pressure. It is argued that the solar wind interaction with Venus during periods of high solar wind dynamic pressure might provide a good analogy for the interaction of Titan with the Saturnian magnetospheric plasma.

Keller, C. N.↗
NASA NTRS1992

The structure of mid-ocean ridges

Recent research results on the structure of midocean ridges are reviewed. The new view of ridge-axis crustal structure obtained from high-resolution seismology is reviewed, emphasizing the variation of that structure with spreading rate and along-axis at a given spreading rate. Recent results on upper mantle structure beneath ridges are examined, including variations with seafloor age, indications from anisotropy for directions of mantle flow, and long-wavelength along-axis variations in structure and their implications for lateral heterogeneity in mantle temperature and composition.

Solomon, Sean C.↗