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At least 1,081 records · Page 60

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NASA NTRS1984

Space Station reference configuration description

The data generated by the Space Station Program Skunk Works over a period of 4 months which supports the definition of a Space Station reference configuration is documented. The data were generated to meet these objectives: (1) provide a focal point for the definition and assessment of program requirements; (2) establish a basis for estimating program cost; and (3) define a reference configuration in sufficient detail to allow its inclusion in the definition phase Request for Proposal (RFP).

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NASA NTRS1985

Space station configuration and flight dynamics identification

The Space Station will be assembled in low earth orbit by a combination of deployable and space erectable modules that are progressively integrated during successive flights of the Shuttle. The crew assisted space construction will result in a configuration which is a large scale composite of structural elements having connectivity with a wide range of possible end conditions and imprecisely known dynamic characteristics. The generic applications of Flight Dynamics Identification to the candidate Space Station configurations currently under consideration are described. Identification functions are categorized, and the various methods for extracting parameter estimates are correlated with the sensing of parameter estimates are correlated with the sensing of specific characteristics of interest to both engineering subsystems and users of the Station's commercial and scientific facilities. Onboard implementation architecture and constraints are discussed from the viewpoint of maximizing integration of the Identification process with the flight subsystem's data and signal flow.

Metter, E.↗

NASA NTRS1985

Nickel-hydrogen spacecraft module configurations study

The incorporation of nickel-hydrogen technology into spacecraft power system designs for low Earth orbit vehicles offers significant power system weight reductions by increasing the power storage watt-hour efficiency. Several possible module configurations exist for the power system. The module configurations were compared utilizing reliability, weight, volume and load capability as evaluation parameters.

Collins, W. B.↗

NASA NTRS1985

Spacecraft (Mobile Satellite) configuration design study

The relative costs to procure and operate a two-satellite mobile satellite system designed to operate either in the UHF band of the L Band, and with several antenna diameter options in each frequency band was investigated. As configured, the size of the spacecraft is limited to the current RCA Series 4000 Geosynchronous Communications Spacecraft bus, which spans the range from 4000 to 5800 pounds in the transfer orbit. The Series 4000 bus forms the basis around which the Mobile Satellite transponder and associated antennas were appended. Although the resultant configuration has little outward resemblance to the present Series 4000 microwave communications spacecraft, the structure, attitude control, thermal, power, and command and control subsystems of the Series 4000 spacecraft are all adapted to support the Mobile Satellite mission.

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NASA NTRS1984

Numerical simulation of the transonic flowfield for wing/nacelle configurations

An efficient grid-interfacing zonal algorithm has been developed for computing the three-dimensional transonic flow field about wing/nacelle multicomponent configurations. The algorithm uses the full-potential formulation and the AF2 fully-implicit approximate factorization scheme. The flow field position is computed using a component-adaptive grid approach in which separate grids are employed for the individual components in the multicomponent configuration, where each component grid is optimized for a particular geometry such as the wing or nacelle. The wing and nacelle component grids are allowed to overlap, and flow field information is transmitted from one grid to another through the overlap region using trivariate interpolation. This paper presents a discussion of the computational methods used to generate both the wing and nacelle component grids, the technique used to interface the component grids, and the method used to obtain the inviscid multicomponent flow field solution. Computed results and correlations with experiment are presented to illustrate application of the analysis.

Atta, E. H.↗

NASA NTRS1985

Estimating the weight of generally configured dual wing systems

Formulas available for the weight estimation of monoplane wings cannot be said to be appropriate for the estimation of generally configured dual wing systems. In the present paper a method is described which simultaneously generates a structural weight estimate and a fully stressed, quasi-optimal structure for a model of a dual wing system. The method is fast and inexpensive. It is ideally suited to preliminary design. To illustrate the method, a dual wing system and a conventional wing system are sized. Numerical computation is shown to be suitably fast for both cases and, for both cases, convergence to a final configuration is shown to be quite rapid. To illustrate the validity of the method, a conventional wing is sized and its weight obtained by the present method is compared to its weight determined by a reputable weight estimation formula. The results are shown to be very close.

Cronin, D. L.↗

NASA NTRS1985

Unsteady transonic flow calculations for two-dimensional canard-wing configurations with aeroelastic applications

Unsteady transonic flow calculations for aerodynamically interfering airfoil configurations are performed as a first-step toward solving the three-dimensional canard-wing interaction problem. These calculations are performed by extending the XTRAN2L two-dimensional unsteady transonic small-disturbance code to include an additional airfoil. Unsteady transonic forces due to plunge and pitch motions of a two-dimensional canard and wing are presented. Results for a variety of canard-wing separation distances reveal the effects of aerodynamic interference on unsteady transonic airloads. Aeroelastic analyses employing these unsteady airloads demonstrate the effects of aerodynamic interference on aeroelastic stability and flutter. For the configurations studied, increases in wing flutter speed result with the inclusion of the aerodynamically interfering canard.

Batina, J. T.↗

NASA NTRS1985

On the configuration of the polar cusps in earth's magnetosphere

The interaction between the solar wind and the earth's vacuum dipole field leads to the formation of a discontinuity called the magnetopause. In the standard picture, the magnetopause confines the magnetic field in such a manner that the polar cusp field lines originate from high latitudes in the dayside ionosphere and end at the two magnetic neutral points. Wu (1983, 1984) has questioned this standard picture of the polar cusp. MHD simulations indicate the existence of a current sheet above the polar cusp region, called 'the cusp current sheet' by Wu. Wu (1983) concluded that the difference between his cusp configuration and the standard picture is due to the fact that his geometry results from a plasma model, whereas the standard picture is based on a vacuum concept. In the present investigation, Wu's conclusion is questioned, and it is demonstrated that the standard cusp configuration is not restricted to the vacuum magnetosphere.

Voigt, G.-H.↗

NASA NTRS1985

Model of oval and polar cap arc configurations

A model of oval and polar cap arc configurations has been formulated by combining the theory of antiparallel magnetic merging and theories of the evening discrete arc and of the morningside arc systems. Aside from incorporating the verified and yet-to-be-verified predictions of the individual component theories this unified model leads to definite predictions of not only arc configurations but also characteristics of the plasmas that produce the various types of arcs. The model predicts two types of polar cap arcs characterized by the plasma sources: the magnetosheath arc and the plasma sheet arc. Their occurrence should be governed by the By component of the interplanetary magnetic field, and the same type should not occur simultaneously in both hemispheres.

Chiu, Y. T.↗

NASA NTRS1984

Options for a new Arizona observatory - Configurations, costs and site

The process of creating a major observatory, with emphasis on the configurations, costs, and site involved, is examined. The premise that cost optimization starts with a modestly priced building block, such as a 7.5-m telescope, is considered. The telescope unit and the configurations in which it is used, ranging from a single telescope or a set of separate telescopes, to an MMT in which the light of all of the telescopes can be phased when desired, are described. It is shown that options exist for using elements in a nonredundant linear array or Michelson interferometer. A means of estimating costs of different facilities, all on the same basis, is provided. The importance of placing the observatory on a site, such as Mt. Graham in Arizona, which maximizes the output per unit cost of the facility is discussed.

Woolf, N. J.↗

NASA NTRS1985

Atmospheric electric field and current configurations in the vicinity of mountains

A number of investigations have been conducted regarding the electrical distortion produced by the earth's orography. Hays and Roble (1979) utilized their global model of atmospheric electricity to study the effect of large-scale orographic features on the currents and fields of the global circuit. The present paper is concerned with an extension of the previous work, taking into account an application of model calculations to orographic features with different configurations and an examination of the electric mapping of these features to ionospheric heights. A two-dimensional quasi-static numerical model of atmospheric electricity is employed. The model contains a detailed electrical conductivity profile. The model region extends from the surface to 100 km and includes the equalization layer located above approximately 70 km. The obtained results show that the electric field and current configurations above mountains depend upon the curvature of the mountain slopes, on the width of the mountain, and on the columnar resistance above the mountain (or mountain height).

Tzur, I.↗

NASA NTRS1985

Plasma-dominated magnetic field configurations for the magnetosphere of Uranus

There is significant indirect evidence that the planet Uranus possesses a magnetic field. This evidence is based on the observation of hydrogen Lyman alpha emission from Uranus with the aid of the International Ultraviolet Explorer (IUE) spacecraft. The detection of water ice on the Uranian moons led Cheng (1984) to suggest that charged particle sputtering of the icy satellites could provide a significant internal source of oxygen ions and protons to the Uranian magnetosphere. Cheng concluded that this mechanism would predict aurorae around both magnetic poles of Uranus. Cheng's idea of the presence of a continuous internal plasma supply to the Uranian magnetosphere is further pursued in the present investigation. Questions are considered regarding the evolution of Uranus' magnetosphere from a vacuum configuration toward a plasma pressure dominated equilibrium configuration, taking into account the amount of the thermal plasma pressure as a free parameter.

Ip, A. K.↗

NASA NTRS1985

Unsteady transonic flow calculations for interfering lifting surface configurations

Unsteady transonic flow calculations are presented for aerodynamically interfering lifting surface configurations. Calculations are performed by extending the XTRAN3S (Version 1.5) unsteady transonic small-disturbance code to allow the treatment of an additional lifting surface. The research was conducted as a first-step toward developing the capability to treat a complete flight vehicle. Grid generation procedures for swept tapered interfering lifting surface applications of XTRAN3S are described. Transonic calculations are presented for wing-tail and canard-wing configurations for several values of mean angle of attack. The effects of aerodynamic interference on transonic steady pressure distributions and steady and oscillatory spanwise lift distributions are demonstrated. Results due to wing, tail, or canard pitching motions are presented and discussed in detail.

Batina, J. T.↗

NASA NTRS1985

A numerical investigation of the aerodynamics of biconic and non-circular flared configurations

Two families of biconic flares and three noncircular flares were studied at Mach numbers from 2 to 4 using a parabolized Navier-Stokes code. All configurations had cone-cyclinder forebodies. The biconic flares were examined to determine if drag could be reduced without significant loss of stability. Only slight drag reduction was found; however, meaningful volume increases were possible with negligible drag penalty. Significant decreases in drag were obtained with the noncircular flares. These configurations maintain considerable pitch stability but sacrifice nearly all yaw stability. The latter can be corrected with fold-out fins that could be readily accommodated on the noncircular flares.

Cottrell, C. J.↗

NASA NTRS1986

A Combined Scanning Configuration for Near-Field Antenna Measurements

Scanning configuration for near-field antenna measurements uses cylindrical and plane-polar coordinate surfaces to guide motions of electromagnetic-field probes. Near-field measurements needed especially to enable determination of far fields of large, low-sidelobe, multiplebeam antennas, for which application of far-field measurements often not suitable. New cylindrical/plane-polar scanning configuration requires less space, yet expected to give complete measurements with fewer mechanical complications.

Rahmat-Samii, Y.↗

NASA NTRS1985

Evaluation of an aerodynamic-load prediction method on a STOL fighter configuration

A three-dimensional panel method was used to compute the aerodynamic loads on a large-scale, powered wind tunnel model. The size of the computation grid was selected such that turnaround times, on present computers remained satisfactory. With this constraint, the STOL aircraft configuration was modeled and the capabilities and limitations of the prediction method were investigated. After this study, a similar numerical model was established for a forward-swept-wing aircraft configuration which is planned for large-scale, low-speed testing. The resulting aerodynamic-load predictions are discussed and will be utilized, together with the future experimental results, to obtain a broader validation of this method as well as to reduce the necessary size of the matrix of the test parameters.

Katz, J.↗

NASA NTRS1985

Improved stud configurations for attaching laminated wood wind turbine blades

A series of bonded stud design configurations was screened on the basis of tension-tension cyclic tests to determine the structural capability of each configuration for joining a laminated wood structure (wind turbine blade) to a steel flange (wind turbine hub). Design parameters which affected the joint strength (ultimate and fatigue) were systematically varied and evaluated through appropriate testing. Two designs showing the most promise were used to fabricate addiate testing. Two designs showing the most promise were used to fabricate additional test specimens to determine ultimate strength and fatigue curves. Test results for the bonded stud designs demonstrated that joint strengths approaching the 10,000 to 12,000 psi ultimate strength and 5000 psi high cycle fatigue strength of the wood epoxy composite could be achieved.

Fadoul, J. R.↗

NASA NTRS1985

Aerodynamic characteristics of a high-wing transport configuration with a over-the-wing nacelle-pylon arrangement

An investigation has been conducted in the Langley 16-Foot Transonic Tunnel to determine the effects on the aerodynamic characteristics of a high-wing transport configuration of installing an over-the-wing nacelle-pylon arrangement. The tests are conducted at Mach numbers from 0.70 to 0.82 and at angles of attack from -2 deg to 4 deg. The configurational variables under study include symmetrical and contoured nacelles and pylons, pylon size, and wing leading-edge extensions. The symmetrical nacelles and pylons reduce the lift coefficient, increase the drag coefficient, and cause a nose-up pitching-moment coefficient. The contoured nacelles significantly reduce the interference drag, though it is still excessive. Increasing the pylon size reduces the drag, whereas adding wing leading-edge extension does not affect the aerodynamic characteristics significantly.

Henderson, W. P.↗