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At least 559 records · Page 31

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NASA NTRS1978

Derivation of the equations of motion for complex structures by symbolic manipulation

This paper outlines a computer program especially tailored to the task of deriving explicit equations of motion for structures with point-connected substructures. The special purpose program is written in FORTRAN and is designed for performing the specific algebraic operations encountered in the derivation of explicit equations of motion. The derivation is by the Lagrangian approach. Using an orderly kinematical procedure and a discretization and/or truncation scheme, it is possible to write the kinetic and potential energy of each substructure in a compact vector-matrix form. Then, if each element of the matrices and vectors encountered in the kinetic and potential energy is a known algebraic expression, the computer program performs the necessary operations to evaluate the kinetic and potential energy of the system explicitly. Lagrange's equations for small motions about equilibrium can be deduced directly from the explicit form of the system kinetic and potential energy.

Hale, A. L.↗

NASA NTRS1979

Flight controls/avionics research - Impact on future civil helicopter operating efficiency and mission reliability

Operational efficiency and mission reliability are key capabilities which will impact the future use of helicopters in the civil segment and areas where flight control/avionics research can play a major role. The present paper reviews flight control/avionics system needs for each major area of civil helicopter use. Technology requirements to meet civil needs are discussed. The review points up the need for the development of all-weather flight control concepts and the validation of cost effective active control/fly-by-wire/fly-by-light system concepts with modular architecture which can be tailored to specific mission requirements.

Snyder, W. J.↗

NASA NTRS1981

Versatile modular scaffolds

Movable and fixed modular scaffolds can be tailored to most scaffolding needs by interconnecting only 4 basic structural elements: platforms, rails, vertical-support angles, and stiffener. Standard nuts and bolts are used to join elements, simplifying construction, and reducing costs. Scaffolds are rigid and can be made any length. They are stable on unlevel ground and can extend to well over 50 feet in height. Scaffolds allow for internal elevators and for wheels and air mounts so that same elements can be used for standing or movable scaffold.

Kerley, J.↗

NASA NTRS1979

Effects of fuselage forebody geometry on low-speed lateral-directional characteristics of twin-tail fighter model at high angles of attack

Low-speed, static wind-tunnel tests were conducted to explore the effects of fighter fuselage forebody geometry on lateral-directional characteristics at high angles of attack and to provide data for general design procedures. Effects of eight different forebody configurations and several add-on devices (e.g., nose strakes, boundary-layer trip wires, and nose booms) were investigated. Tests showed that forebody design features such as fineness ratio, cross-sectional shape, and add-on devices can have a significant influence on both lateral-directional and longitudinal aerodynamic stability. Several of the forebodies produced both lateral-directional symmetry and strong favorable changes in lateral-directional stability. However, the same results also indicated that such forebody designs can produce significant reductions in longitudinal stability near maximum lift and can significantly change the influence of other configuration variables. The addition of devices to highly tailored forebody designs also can significantly degrade the stability improvements provided by the clean forebody.

Carr, P. C.↗

NASA NTRS1979

Data reduction software for LORAN-C flight test evaluation

A set of programs designed to be run on an IBM 370/158 computer to read the recorded time differences from the tape produced by the LORAN data collection system, convert them to latitude/longitude and produce various plotting input files are described. The programs were written so they may be tailored easily to meet the demands of a particular data reduction job. The tape reader program is written in 370 assembler language and the remaining programs are written in standard IBM FORTRAN-IV language. The tape reader program is dependent upon the recording format used by the data collection system and on the I/O macros used at the computing facility. The other programs are generally device-independent, although the plotting routines are dependent upon the plotting method used. The data reduction programs convert the recorded data to a more readily usable form; convert the time difference (TD) numbers to latitude/longitude (lat/long), to format a printed listing of the TDs, lat/long, reference times, and other information derived from the data, and produce data files which may be used for subsequent plotting.

Fischer, J. P.↗

NASA NTRS1980

Cold-air investigation of a 4 1/2 stage turbine with stage-loading factor of 4.66 and high specific work output. 2: Stage group performance

The stage group performance of a 4 1/2 stage turbine with an average stage loading factor of 4.66 and high specific work output was determined in cold air at design equivalent speed. The four stage turbine configuration produced design equivalent work output with an efficiency of 0.856; a barely discernible difference from the 0.855 obtained for the complete 4 1/2 stage turbine in a previous investigation. The turbine was designed and the procedure embodied the following design features: (1) controlled vortex flow, (2) tailored radial work distribution, and (3) control of the location of the boundary-layer transition point on the airfoil suction surface. The efficiency forecast for the 4 1/2 stage turbine was 0.886, and the value predicted using a reference method was 0.862. The stage group performance results were used to determine the individual stage efficiencies for the condition at which design 4 1/2 stage work output was obtained. The efficiencies of stages one and four were about 0.020 lower than the predicted value, that of stage two was 0.014 lower, and that of stage three was about equal to the predicted value. Thus all the stages operated reasonably close to their expected performance levels, and the overall (4 1/2 stage) performance was not degraded by any particularly inefficient component.

Whitney, W. J.↗

NASA NTRS1980

User's guide for Skylab dynamics program, SKYDYN

This user's manual describes the capabilities, required input data, and resulting output of SKYDYN, version of the 6 degree-of-freedom digital program REENTR which was extensively modified for the Honeywell CP-V system and was tailored to the specfic requirements for SKYLAB.

Hopkins, M. S.↗

NASA NTRS1979

ICEX: Ice and Climate Experiment. Report of science and applications working group

The Ice and Climate Experiment (ICEX), a proposed program of coordinated investigations of the ice and snow masses of the Earth (the "cryosphere") is described. These investigations are to be carried out with the help of satellite, aircraft, and surface based observations. Measurements derived from the investigations will be applied to an understanding of the role of the cryosphere in the system that determines the Earth's climate, to a better prediction of the responses of the ice and snow to climatic change, to studies of the basic nature of ice forms and ice dynamics, and to the development of operational techniques for assisting such activities in the polar regions as transportation, exploitation of natural resources, and petroleum exploration and production. A high-inclination satellite system with a set of remote-sensing instruments specially tailored to the task of observing the important features of snow, sea ice, and the ice sheets of Greenland and the Antarctic is to be used to record the near-simultaneous observations of multiple geophysical parameters by complementary sensors.

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NASA NTRS1980

Exploratory piloted simulator study of the effects of winglets on handling qualities of a representative agricultural airplane

The effects on handling qualities of adding winglets to a representative agricultural aircraft configuration during swath-run maneuvering were evaluated. Aerodynamic data used in the simulation were based on low-speed wind tunnel tests of a full scale airplane and a subscale model. The Cooper-Harper handling qualities rating scale, supplementary pilot comments, and pilot vehicle performance data were used to describe the handling qualities of the airplane with the different wing-tip configurations. Results showed that the lateral-directional handling qualities of the airplane were greatly affected by the application of winglets and winglet cant angle. The airplane with winglets canted out 20 deg exhibited severely degraded lateral directional handling qualities in comparison to the basic airplane. When the winglets were canted inward 10 deg, the flying qualities of the configuration were markedly improved over those of the winglet-canted-out configuration or the basic configuration without winglets, indicating that proper tailoring of the winglet design may afford a potential benefit in the area of handling qualities.

Ogburn, M. E.↗

NASA NTRS1979

Layered synthetic microstructures - Properties and applications in X-ray astronomy

Refinements in vacuum deposition technology have made it possible to produce structures in which two materials are arranged in alternating layers of uniform thickness and as thin as 5 A. Such structures act as Bragg diffractors or 'artificial crystals' for X-rays, as well as they may be regarded as multilayer interference coatings. A dynamical theory is used to show how the properties of layered synthetic microstructures are dependent on the layer materials and thicknesses and how these properties can be tailored to specific applications. Laboratory results at various X-ray wavelengths are presented. In particular, specific X-ray astronomy applications in spectroscopy, imaging, polarimetry and laboratory calibration are discussed.

Underwood, J. H.↗

NASA NTRS1980

Sound transmission into a laminated composite cylindrical shell

In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of an oblique plane sound wave into a laminated composite circular cylindrical shell. Numerical results are obtained for geometry typical of a narrow-bodied jet transport. Results indicate that from the viewpoint of noise attenuation on laminated composite shell does not appear to offer any significant advantage over an aluminum shell. However, the transmission loss of a laminated composite shell is sensitive to the orientation of the fibers and this suggests the possibility of using a laminated composite shell to tailor the noise attenuation characteristics to meet a specific need.

Koval, L. R.↗

NASA NTRS1980

A Fourier transform with speed improvements for microprocessor applications

A fast Fourier transform algorithm for the RCA 1802microprocessor was developed for spacecraft instrument applications. The computations were tailored for the restrictions an eight bit machine imposes. The algorithm incorporates some aspects of Walsh function sequency to improve operational speed. This method uses a register to add a value proportional to the period of the band being processed before each computation is to be considered. If the result overflows into the DF register, the data sample is used in computation; otherwise computation is skipped. This operation is repeated for each of the 64 data samples. This technique is used for both sine and cosine portions of the computation. The processing uses eight bit data, but because of the many computations that can increase the size of the coefficient, floating point form is used. A method to reduce the alias problem in the lower bands is also described.

Lokerson, D. C.↗

NASA NTRS1980

Fabrication of AlGaAs/GaAs cascade solar cell by LPE

Stacking two or more photovoltaic junctions in electrical and optical series results in higher conversion efficiency since each junction can be tailored to respond more efficiently to a smaller range of photon energies. An efficiency of about 30 percent was predicted for a two junction cascade cell having the optimum bandgap values. A number of III-V materials systems were considered for use in fabricating cascade solar cells. The Al-Ga-As system is attractive from a developmental standpoint since it employs a proven materials system that is closely lattice matched throughout its compositional range. This system employs a GaAs low bandgap cell and 1.9 eV AlGaAs high bandgap cell connected by an AlGaAs tunnel junction. Although this cell does not possess the optimum bandgap values, an efficiency of 25 percent was predicted at 300 K under AMO, 1 sun illumination.

Bedair, S. M.↗

NASA NTRS1978

Hybrid receiver conceptual design and test report

The Hybrid Receiver described uses an acquisition and demodulation scheme tailored to the Jovian environment. The large Doppler offsets expected during initial acquisition led to development of the Hilbert Acquisition Aid, which provides for rapid acquisition for low signal to noise densities.

Klare, S. W.↗

NASA NTRS1981

A procedure for designing forebodies with constraints on cross-section shape and axial area distribution

A method is described for designing a forebody with cross sections which vary smoothly from an initial prescribed nose shape to a different prescribed base shape in such a way that the cross-section areas conform to a preassigned axial area distribution. It is shown that these conditions can be satisfied with a remaining degree of freedon, which can be used to accomplish a modest amount of geometric or pressure tailoring of the forebody. An example is provided which involves modifying the pressure distribution along a given meridian line of the forebody.

Barger, R. L.↗

NASA NTRS1979

Design and wind tunnel tests of winglets on a DC-10 wing

Results are presented of a wind tunnel test utilizing a 4.7 percent scale semi-span model in the Langley Research Center 8-foot transonic pressure wind tunnel to establish the cruise drag improvement potential of winglets as applied to the DC-10 wide body transport aircraft. Winglets were investigated on both the DC-10 Series 10 (domestic) and 30/40 (intercontinental) configurations and compared with the Series 30/40 configuration. The results of the investigation confirm that for the DC-10 winglets provide approximately twice the cruise drag reduction of wing-tip extensions for about the same increase in bending moment at the wing fuselage juncture. Furthermore, the winglet configurations achieved drag improvements which were in close agreement to analytical estimates. It was observed that relatively small changes in wing-winglet tailoring effected large improvements in drag and visual flow characteristics. All final winglet configurations exhibited visual flow characteristics on the wing and winglets

Gilkey, R. D.↗

NASA NTRS1981

An evaluation of the Intel 2920 digital signal processing integrated circuit

The circuit consists of a digital to analog converter, accumulator, read write memory and UV erasable read only memory. The circuit can convert an analog signal to a digital representation, perform mathematical operations on the digital signal and subsequently convert the digital signal to an analog output. Development software tailored for programming the 2920 is presented.

Heller, J.↗

NASA NTRS1981

Publications of the Jet Propulsion Laboratory, 1980

This bibliography cites by primary author the externally distributed technical reporting, released during calendar year 1980, that resulted from scientific and engineering work performed, or managed, by the Jet Propulsion Laboratory. Three classes of publications are included: (1) JPL Publications (77-, 78-, 79-series, etc.), in which the information is complete for a specific accomplishment and can e tailored to wide or limited audiences and be presented in an established standard format or special format to meet unique requirements; (2) articles published in the open literature; and (3) articles from the bimonthly Deep Space Network (DSN) Progress Repot (42-series) and its successor, the Telecommunications and Data Acquisition (TDA) Progress Report (also 42-series).

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