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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Analysis of preflutter and postflutter characteristics with motion-matched aerodynamic forces

The development of the equations of dynamic equilibrium for a lifting surface from Lagrange's equation is reviewed and restated for general exponential growing and decaying oscillatory motion. Aerodynamic forces for this motion are obtained from the three-dimensional supersonic kernel function that is newly generalized to complex reduced frequencies. Illustrative calculations were made for two flutter models at supersonic Mach numbers. Preflutter and postflutter motion isodecrement curves were obtained. This type of analysis can be used to predict preflutter behavior during flutter testing and to predict postflutter behavior for use in the design of flutter suppression systems.

Cunningham, H. J.↗
NASA NTRS1977

Scaling a discrete structural model to match measured modal frequencies

The structure modification problem, where the computer model of a structure is to be upgraded on the basis of experimental measurements of normal mode frequencies, is approached by the modal energy concept. The modes for correlation with test data are selected on the basis of relative strain energy participation. The resulting procedure can be viewed as an extension of White's (1972) method. Its advantage lies in that both the number and choice of structural parameters to be varied in the modification are arbitrary.

Taylor, J. E.↗
NASA NTRS1978

Inlet-engine matching for SCAR including application of a bicone variable geometry inlet

Airflow characteristics of variable cycle engines (VCE) designed for Mach 2.32 can have transonic airflow requirements as high as 1.6 times the cruise airflow. This is a formidable requirement for conventional, high performance, axisymmetric, translating centerbody mixed compression inlets. An alternate inlet is defined where the second cone of a two cone centerbody collapses to the initial cone angle to provide a large off-design airflow capability, and incorporates modest centerbody translation to minimize spillage drag. Estimates of transonic spillage drag are competitive with those of conventional translating centerbody inlets. The inlet's cruise performance exhibits very low bleed requirements with good recovery and high angle of attack capability.

Wasserbauer, J. F.↗
NASA NTRS1979

On matching the spectrum of Io - Variations in the photometric properties of sulfur-containing mixtures

The problem of comparing laboratory spectra of sulfur-containing binary mixtures with the spectrum of Io is discussed. For the satellite, the observable is the geometric albedo as a function of wavelength, whereas in the laboratory one often measures some other type of albedo. A previous paper demonstrated that for pure sulfur the multiplicative factor which converts the laboratory albedos to geometric albedos can be strongly wavelength dependent. The present paper demonstrates that this is also true for binary sulfur-containing mixtures. Furthermore, there is no universal conversion factor applicable to all binary mixtures, nor can the factor be interpolated for a particular mixture from the conversion factors of the two end members. The conversion factor is a function not only of the specific composition of a binary mixture but also of the relative particle size distributions of the two components, and must be measured specifically for each individual sample if a quantitative comparison between a laboratory sample and Io's surface is desired.

Veverka, J.↗
NASA NTRS1980

Subsonic aircraft: Evolution and the matching of size to performance

Methods for estimating the approximate size, weight, and power of aircraft intended to meet specified performance requirements are presented for both jet-powered and propeller-driven aircraft. The methods are simple and require only the use of a pocket computer for rapid application to specific sizing problems. Application of the methods is illustrated by means of sizing studies of a series of jet-powered and propeller-driven aircraft with varying design constraints. Some aspects of the technical evolution of the airplane from 1918 to the present are also briefly discussed.

Loftin, L. K., Jr.↗
NASA NTRS1979

74001 drive tube - Siderophile elements match II B iron meteorite pattern

Eight siderophile elements, seven volatile elements, and U were determined in three samples from 74001 by radiochemical neutron activation analysis. The siderophile pattern closely corresponds to the addition of approximately 0.1% of II B iron meteorites, and the enrichment of nonsiderophile volatile elements seems to be derived from lunar sources with variation generally following Se content. In addition, in 74001 (predominantly black glass), moderately volatile elements (Ag, Zn) are more abundant than In, Cd, and particularly Bi, while in 74220 (mainly orange glass), Ag, Zn, In, and Cd are almost equally abundant, but Bi is as low as in 74001.

Morgan, J. W.↗
NASA NTRS1980

Some effects of cruise speed and engine matching of supersonic inlet design

An analytical study was conducted to determine the impact of flight Mach number on inlet type selection for a supersonic cruise aircraft. External and mixed-compression axisymmetric and two-dimensional inlets were considered. The internal contraction of the mixed-compression inlets was limited to achieve self-starting. At Mach 2.0, the axisymmetric mixed-compression inlet provided the best aircraft range. At Mach 2.3, the two-dimensional mixed-compression inlet was the most attractive if enough variable geometry were incorporated to minimize spillage during subsonic cruise. Increases in takeoff-to-cruise air flow ratio gave lower aircraft range.

Bangert, L. H.↗
NASA NTRS1980

Mixed mode missions - Designing payloads to match flight opportunities

Shuttle missions have usually been viewed as being devoted to a single mission mode. But full utilization of the STS capabilities as a platform for space research dictates a flexible strategy toward payload integration and mission design. Simple interfaces, single disciplines, and large design and resource margins point the way toward larger payload integration and operation costs. Payloads for early missions (i.e., OSTA-1, OSS-1, and MEA) are used as illustrations to support this argument. The implications of this approach for future NASA plans as well as for new STS operational concepts are considered.

Noblitt, B. G.↗
NASA NTRS1981

Helicopter rotor loads using a matched asymptotic expansion technique

The theoretical basis and computational feasibility of the Van Holten method, and its performance and range of validity by comparison with experiment and other approximate methods was examined. It is found that within the restrictions of incompressible, potential flow and the assumption of small disturbances, the method does lead to a valid description of the flow. However, the method begins to break down under conditions favoring nonlinear effects such as wake distortion and blade/rotor interaction.

Pierce, G. A.↗
NASA NTRS1981

On matching the systems identification technique to the particular application

Several maximum likelihood and multiple regression parameter estimation programs are currently being used at the Langley Research Center of the NASA to analyze aircraft flight test data. Based on this wealth of experience, the pertinent features of these programs are investigated and some of the difficulties involved in their use are discussed. By comparing computational time, data requirements and accuracy needed, a strategy for determining which program can be used to the best advantage of the flight test engineer is discussed.

Suit, W. T.↗
NASA NTRS1983

Helicopter rotor loads using matched asymptotic expansions: User's manual

Computer programs were developed to implement the computational scheme arising from Van Holten's asymptotic method for calculating airloads on a helicopter rotor blade in forward flight, and a similar technique which is based on a discretized version of the method. The basic outlines of the two programs are presented, followed by separate descriptions of the input requirements and output format. Two examples illustrating job entry with appropriate input data and corresponding output are included. Appendices contain a sample table of lift coefficient data for the NACA 0012 air foil and listings of the two programs.

Pierce, G. A.↗
NASA NTRS1985

Matching Impedances and Modes in Acoustic Levitation

Temperature differences accommodated with tunable coupler. Report discusses schemes for coupling sound efficiently from cool outside atmosphere into hot acoustic-levitation chamber. Theoretical studies have practical implications for material-processing systems that employ acoustic levitation.

Barmatz, M. B.↗
NASA NTRS1982

Development of a HgCdTe photomixer and impedance matched GaAs FET amplifier

A research program for the development of a 10.6 micron HgCdTe photodiode/GaAs field effect transistor amplifier package for use at cryogenic temperatures (77k). The photodiode/amplifier module achieved a noise equivalent power per unit bandwidth of 5.7 times 10 to the 20th power W/Hz at 2.0 GHz. The heterodyne sensitivity of the HgCdTe photodiode was improved by designing and building a low noise GaAs field effect transistor amplifier operating at 77K. The Johnson noise of the amplifier was reduced at 77K, and thus resulted in an increased photodiode heterodyne sensitivity.

Shanley, J. F.↗
NASA NTRS1985

Making Stronger Twine With Matched Strands

Higher tensil strength achieved with same production equipment. Strong twine made by using spools in one of two-step manufacturing process. Three primary strands twisted together in opposite direction to form threeply twine. Technique used successfully in manufacture of safety netting with 600- to 700-lb (2,700-to 3,100-N) tensil strength and 60-ton (54 x 10 to third power kg) tuna seine with area of 86 acres (3.5 x 10 to fifth power m2). Increase in tensil strength of completed twine found experimentally 10 to 12 percent.

Kirkland, W. L.↗
NASA NTRS1984

Optical matching for fiber optic spectroscopy

Single silica fibers of the type developed for communications are useful in the design of astronomical spectrographs. They can be used to couple light from many objects over a wide field to a single spectrograph, or to eliminate wavelength errors from image motion and gravitational flexure. For many applications it will be advantageous to use small lenses to make the most efficient coupling into and out of a fiber. If the telescope pupil is imaged on the fiber core, an efficient coupling can be made that preserves image size over a certain range. This method is demonstrated by a laboratory test using sapphire spheres as coupling lenses.

Hill, J. M.↗
NASA NTRS1986

Matching Vibration Testing to "Real-World" Conditions

Vibration spectrum of test machine adjusted to that observed in operation. Test specimen placed in test fixture and attached to shaker. Shaker initially operated at one-quarter full level of input spectrum to prevent overloading. Short vibration test run, and specimen response compared to control spectrum. Imput spectrum then adjusted until response resembles control spectrum.

Olsen, Albert D., Jr.↗
NASA NTRS1986

Fuzzy automata and pattern matching

A wide-ranging search for articles and books concerned with fuzzy automata and syntactic pattern recognition is presented. A number of survey articles on image processing and feature detection were included. Hough's algorithm is presented to illustrate the way in which knowledge about an image can be used to interpret the details of the image. It was found that in hand generated pictures, the algorithm worked well on following the straight lines, but had great difficulty turning corners. An algorithm was developed which produces a minimal finite automaton recognizing a given finite set of strings. One difficulty of the construction is that, in some cases, this minimal automaton is not unique for a given set of strings and a given maximum length. This algorithm compares favorably with other inference algorithms. More importantly, the algorithm produces an automaton with a rigorously described relationship to the original set of strings that does not depend on the algorithm itself.

Setzer, C. B.↗
NASA NTRS1988

Representation and matching of knowledge to design digital systems

A knowledge-based expert system is described that provides an approach to solve a problem requiring an expert with considerable domain expertise and facts about available digital hardware building blocks. To design digital hardware systems from their high level VHDL (Very High Speed Integrated Circuit Hardware Description Language) representation to their finished form, a special data representation is required. This data representation as well as the functioning of the overall system is described.

Jones, J. U.↗