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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 1,171 records · Page 65

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NASA NTRS1973

Relaxation solutions for inviscid axisymmetric transonic flow over blunt or pointed bodies.

A finite-difference relaxation method is presented for numerical solution of the full potential equation and exact boundary conditions for general axisymmetric bodies is inviscid, steady transonic flow. Body-normal coordinates are used in the nose region and sheared cylindrical coordinates are used on the afterbody to accommodate corners such as boattails and flares. An improved difference scheme is used which does not require that the flow be nearly alined with a coordinate direction in supersonic regions, and which treats either subsonic or supersonic free streams. Numerical results are illustrated for some simple classical shapes such as spheres and ellipsoids, and for more practical shapes like tangent-ogives with boattails. Special attention is given to bodies which have been studied for area-rule applications. Agreement with available experimental results is good in cases where viscous effects and wind-tunnel wall interference are not important.

South, J. C., Jr.↗

NASA NTRS1973

Imaging techniques in X-ray astronomy.

Some of the imaging problems encountered in space-borne X-ray astronomy are reviewed, along with the techniques considered for their solution. Following a discussion of X-ray focussing and X-ray image processing, the development of X-ray imaging devices is surveyed. It is shown that the imaging devices that will be used in X-ray astronomy will take advantage of developments intended for infrared and optical astronomy. The special requirements of X-ray observation - especially, single photon detection and high time resolution - rule out the use of existing devices, particularly because of readout problems.

Gursky, H.↗

NASA NTRS1973

Robot vision.

The work reported had been undertaken to develop hardware that would guide an automatic vehicle in the exploration of the surface of Mars, recognize objects, and report the findings to earth. Approaches for automatically determining the range and shape of objects are discussed, giving attention to the automatic comparison of one scan line of the left with one scan line of the right TV image. Methods of mapping binocular space into match space are considered together with the use of a model in match space, rules for processing random-dot stereograms, the elimination of spurious matches, random-square stereograms, questions of the processing of a real scene, and aspects of range accuracy. Methods of computation for extracting other features are also discussed along with stereo TV cameras and approaches for reconstructing the appearance of a scene.

Sutro, L. L.↗

NASA NTRS1973

Recursive formulas for the partial fraction expansion of a rational function with multiple poles.

The coefficients in the partial fraction expansion considered are given by Heaviside's formula. The evaluation of the coefficients involves the differential of a quotient of two polynomials. A simplified approach for the evaluation of the coefficients is discussed. Leibniz rule is applied and a recurrence formula is derived. A coefficient can also be determined from a system of simultaneous equations. Practical methods for the performance of the computational operations involved in both approaches are considered.

Chang, F.-C.↗

NASA NTRS1973

Estimation of dipole-quadrupole dispersion energies.

The calculation of the dipole-quadrupole dispersion coefficient is discussed through a perturbation and a variation method. Accurate combination rules are obtained from both methods, one new and one already known. Further approximations permit computations in terms of accessible parameters. Values are calculated for the interactions of atomic pairs formed from hydrogen, alkali, and rare-gas atoms. A new relation giving the dipole-quadrupole coefficient in terms of the dipole-dipole coefficient and the dipole and quadrupole polarizabilities seems accurate, but needs further testing.

Alvarez-Rizzatti, M.↗

NASA NTRS1973

The Apollo spacecraft: A chronology. Volume 2: 8 November 1962 - 30 September 1964

A chronology of the Apollo spacecraft development and production program is presented. The subjects discussed are: (1) defining contractural relations, (2) developing hardware distinctions, and (3) developing software ground rules. Illustrations, drawings, and photographs are used extensively to supplement the technical writing. Descriptions of life support systems, communication equipment, propulsion systems, control devices, and spacecraft components are provided.

Morse, M. L.↗

NASA NTRS1974

Notes for the improvement of the spatial and spectral data classification method

This report examines the spatial and spectral clustering technique for the unsupervised automatic classification and mapping of earth resources satellite data, and makes theoretical analysis of the decision rules and tests in order to suggest how the method might best be applied to other flight data such as Skylab and Spacelab.

Dalton, C. C.↗

NASA NTRS1972

Information extraction techniques for multispectral scanner data

The applicability of recognition-processing procedures for multispectral scanner data from areas and conditions used for programming the recognition computers to other data from different areas viewed under different measurement conditions was studied. The reflective spectral region approximately 0.3 to 3.0 micrometers is considered. A potential application of such techniques is in conducting area surveys. Work in three general areas is reported: (1) Nature of sources of systematic variation in multispectral scanner radiation signals, (2) An investigation of various techniques for overcoming systematic variations in scanner data; (3) The use of decision rules based upon empirical distributions of scanner signals rather than upon the usually assumed multivariate normal (Gaussian) signal distributions.

Malila, W. A.↗

NASA NTRS1973

Wind machines

The basic elements of the air/water momentum exchange are described by the environment, the potential, the air and water subsystems, the total system, and the rule. Many of these topics have direct analogues in aerogenerator design. Aspects of optimal sail design and of waveless hulls are briefly outlined. A wind driven vehicle capable of moving directly downwind faster than the wind, is reported. The lecture is illustrated with slides and movie clips showing surfing catamarans, land and water versions of the Bauer vehicle, hang gliding, land sailing, and wind surfing.

Lissaman, P. B. S.↗

NASA NTRS1973

Development of improved electroforming technique

Techniques were studied to reinforce or strengthen electroformed nickel to allow a fuller utilization of electroforming as a reliable and low cost fabrication technique for regenerately cooled thrust chambers. Techniques for wire wrapping while electrodepositing were developed that can result in a structurally strong wall with less weight than a conventional electroformed wall. Also a technique of codepositing submicron sized THO2 particles with the nickel to form a dispersion strengthened structure was evaluated. The standard nickel cylinders exhibited an average hoop strength of 80,000 psi with a yield strength of 65,000 psi and a modulus of 25.6 x 10 to the 6th power psi. The as produced dispersion strengthened nickel showed a hoop strength of 97,000 psi with a yield strength of 67,000 psi. This is an increase of 17,000 psi or 21% over the standard nickel hoop strength. The wire wrapping cylinders showed an increased strength over the standard nickel test samples of 26,000 to 66,800 psi which is in the range of 26 to 104% increase in strength over the base standard nickel. These latter test results are indicative of a volume percent wire reinforcement from 15 to 31. The measured hoop strengths agree with calculated composite strengths based upon rule of mixtures.

Mccandles, L. C.↗

NASA NTRS1974

The effect of wind tunnel wall interference on the performance of a fan-in-wing VTOL model

A fan-in-wing model with a 1.07-meter span was tested in seven different test sections with cross-sectional areas ranging from 2.2 sq meters to 265 sq meters. The data from the different test sections are compared both with and without correction for wall interference. The results demonstrate that extreme care must be used in interpreting uncorrected VTOL data since the wall interference may be so large as to invalidate even trends in the data. The wall interference is particularly large at the tail, a result which is in agreement with recently published comparisons of flight and large scale wind tunnel data for a propeller-driven deflected-slipstream configuration. The data verify the wall-interference theory even under conditions of extreme interference. A method yields reasonable estimates for the onset of Rae's minimum-speed limit. The rules for choosing model sizes to produce negligible wall effects are considerably in error and permit the use of excessively large models.

Heyson, H. H.↗

NASA NTRS1974

Use of ERTS data for a multidisciplinary analysis of Michigan resources

The author has identified the following significant results. The results of this investigation of ratioing simulated ERTS spectral bands and several non-ERTS bands (all collected by an airborne multispectral scanner) indicate that significant terrain information is available from band-ratio images. Ratio images, which are based on the relative spectral changes which occur from one band to another, are useful for enhancing differences and aiding the image interpreter in identifying and mapping the distribution of such terrain elements as seedling crops, all bare soil, organic soil, mineral soil, forest and woodlots, and marsh areas. In addition, the ratio technique may be useful for computer processing to obtain recognition images of large areas at lower costs than with statistical decision rules. The results of this study of ratio processing of aircraft MSS data will be useful for future processing and evaluation of ERTS-1 data for soil and landform studies. Additionally, the results of ratioing spectral bands other than those currently collected by ERTS-1 suggests that some other bands (particularly a thermal band) would be useful in future satellites.

Andersen, A. L.↗

NASA NTRS1973

Dust Storms in Space?

Primarily from the Pioneer 8 and 9 results, it is concluded that the flux of picogram sized dust particles near the earth's orbit has been constant to within the observational limits over three years of observation. In particular, since dust streams are not observed, they cannot explain microphone detected events. However, the possibility of rare events due to dust blown directly off a cometary nucleus (such as that reported for Comet Bennett) cannot be completely ruled out.

Roosen, R. G.↗

NASA NTRS1974

Technique for direct measurement of magnetic entropy of solids: Results for dysprosium titanium oxide

A measurement technique was devised which permits direct observation of the magnetic entropy of solids as a function of applied magnetic field. Measurements were made of the magnetic entropy, in the temperature range 2 to 20 K, of polycrystalline samples of dysprosium titanium oxide (Dy2Ti2O7) to determine its suitability for use as the working substance of a magnetic refrigerator. Magnetization measurements were also made at 4.2 K and below to provide additional information on the nature of the compound. The measurements indicated that crystalline electric fields perturbed the ground state of the dysprosium ions, removed the 16-fold degeneracy predicted by Hund's rules, and left only a twofold degeneracy in its place. A positive, temperature independent contribution to the magnetization was observed in the saturation region, which indicated that the doublet ground-state wave function was perturbed by a nearby unpopulated upper energy level.

Flood, D. J.↗

NASA NTRS1974

MSFC Skylab contamination control systems mission evaluation

Cluster external contamination control evaluation was made throughout the Skylab Mission. This evaluation indicated that contamination control measures instigated during the design, development, and operational phases of this program were adequate to reduce the general contamination environment external to the Cluster below the threshold senstivity levels for experiments and affected subsystems. Launch and orbit contamination control features included eliminating certain vents, rerouting vents for minimum contamination impact, establishing filters, incorporating materials with minimum outgassing characteristics and developing operational constraints and mission rules to minimize contamination effects. Prior to the launch of Skylab, contamination control math models were developed which were used to predict Cluster surface deposition and background brightness levels throughout the mission. The report summarizes the Skylab system and experiment contamination control evaluation. The Cluster systems and experiments evaluated include Induced Atmosphere, Corollary and ATM Experiments, Thermal Control Surfaces, Solar Array Systems, Windows and Star Tracker.

Source record↗

NASA NTRS1973

Survey of literature on convective heat transfer coefficients and recovery factors for high atmosphere thermometry

Heat transfer phenomena of rarefied gas flows is discussed based on a literature survey of analytical and experimental rarefied gas dynamics. Subsonic flows are emphasized for the purposes of meteorological thermometry in the high atmosphere. The heat transfer coefficients for three basic geometries are given in the regimes of free molecular flow, transition flow, slip flow, and continuum flow. Different types of heat phenomena, and the analysis of theoretical and experimental data are presented. The uncertainties calculated from the interpolation rule compared with the available experimental data are discussed. The recovery factor for each geometry in subsonic rarefied flows is also given.

Chung, S.↗

NASA NTRS1974

Review of hydrogen accidents and incidents in NASA operations

A number of the accidents/incidents with hydrogen in NASA operations are reviewed. The cause factors for the mishaps are reviewed and show that although few accidents occurred, the number could have been further reduced if the established NASA rules and regulations had been followed. Requirements for effective safety codes and areas of study for hydrogen safety information are included. The report concludes with a compilation of 96 hydrogen mishaps; a description of the accidents and their causes.

Ordin, P. M.↗

NASA NTRS1974

Investigation of the stall-induced shock wave (hammershock) at the inlet to the engine

The peak static pressures measured at the inlet to the engine during stall are presented for a turbojet and two turbofan engines. It is shown for one turbofan and the turbojet that the static pressure ratio across the hammershock does not exceed significantly the normal shock pressure ratio necessary to stop the flow. The second turbofan engine did not follow this rule. Possible reasons for the departure are discussed. For the two turbofan engines the influence of the stall method on the hammershock intensity was investigated. Data related to the spatial distribution of pressure in the hammershock are also presented.

Kurkov, A. P.↗