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NASA NTRS1976

Interplanetary shocks seen by Ames plasma probe on Pioneer 6 and 7

Interplanetary shocks and discontinuities observed by the Ames Research Center plasma probe on Pioneer 6 and 7 are analyzed with Goddard Space Flight Center magnetometer data. Several shock normals are used for the MHD model of a shock where the mixed data shock normals, which use plasma and magnetic-field data, give the best agreement with the theoretical requirements. The requirements are the satisfaction of the Rankine-Hugoniot conservation equations across the shock where angles (predicted theoretically from the conservation equations) between certain combinations of plasma and magnetic-field data vectors in the shock normals are explicitly checked. The results for the August 29, 1966, shock are compared with previous results.

Abraham-Shrauner, B.↗

NASA NTRS1976

A finite difference method of solving anisotropic scattering problems

A new method of solving radiative transfer problems is described including a comparison of its speed with that of the doubling method, and a discussion of its accuracy and suitability for computations involving variable optical properties. The method uses a discretization in angle to produce a coupled set of first-order differential equations which are integrated between discrete depth points to produce a set of recursion relations for symmetric and anti-symmetric angular sums of the radiation field at alternate depth points. The formulation given here includes depth-dependent anisotropic scattering, absorption, and internal sources, and allows arbitrary combinations of specular and non-Lambertian diffuse reflection at either or both boundaries. Numerical tests of the method show that it can return accurate emergent intensities even for large optical depths. The method is also shown to conserve flux to machine accuracy in conservative atmospheres

Barkstrom, B. R.↗

NASA NTRS1976

Optimum load device for DMOS integrated circuits

Depletion-mode load devices can be integrated with DMOS transistors without any extra diffusions or ion implantation processing steps by judicious choice of the substrate crystal orientation and resistivity. For low voltage operation line-type 1, 1, 1 crystal orientation should be used. The line-type 1, 1, 1 crystal orientation also yields a higher transconductance for the DMOS transistor than the line-type 1, 0, 0 orientation. The geometry of the load device and the DMOS transistor can be made ratioless to conserve area. Self-aligned gates, hitherto considered incompatible with DMOS transistors, have been incorporated in the structure. The experimental DMOS inverters, using a conservative design, have achieved 4-ns propagation delay, 1.3-V operation, and 2-pJ propagation delay-power dissipation product.

Lin, H. C.↗

NASA NTRS1976

A three-dimensional, time-dependent model of Mobile Bay

A three-dimensional, time-variant mathematical model for momentum and mass transport in estuaries was developed and its solution implemented on a digital computer. The mathematical model is based on state and conservation equations applied to turbulent flow of a two-component, incompressible fluid having a free surface. Thus, bouyancy effects caused by density differences between the fresh and salt water, inertia from thare river and tidal currents, and differences in hydrostatic head are taken into account. The conservation equations, which are partial differential equations, are solved numerically by an explicit, one-step finite difference scheme and the solutions displayed numerically and graphically. To test the validity of the model, a specific estuary for which scaled model and experimental field data are available, Mobile Bay, was simulated. Comparisons of velocity, salinity and water level data show that the model is valid and a viable means of simulating the hydrodynamics and mass transport in non-idealized estuaries.

Pitts, F. H.↗

NASA NTRS1977

Computational tests of angular momentum decoupling approximations for pressure broadening cross sections

The utility of several approximate scattering methods for predicting collision induced spectral pressure broadening has been tested by comparison with accurate close coupling results. In particular, broadening of the pure rotational spectra of HD, HCl, CO, and HCN - all perturbed by low energy collisions with He atoms - has been computed using the effective potential formalism of Rabitz, the decoupled l-dominant approximation of DePristo and Alexander, and the j(2)-conserving coupled states method of McGuire and Kouri. For this last method, pressure broadening cross sections have been obtained with the new, correct expression recently derived by Goldflam and Kouri as well as with an earlier formalism based on an incorrect labeling of the scattering matrices. These methods were found to be generally diasppointing for predicting pressure broadening with the exception of the new, correctly formulated j(2)-conserving coupled states method which was found to agree quantitatively (better than 5%) with close coupling values for all cases studied.

Green, S.↗

NASA NTRS1976

Effects of selected R&D options on fuel usage in the commercial air system

The study on which this paper is based, known as RECAT (Study of Cost Benefit Tradeoffs for Reducing the Energy Consumption of the Commercial Air Transportation System), was sponsored by NASA to establish a basis for assigning priorities in its aircraft fuel-conservation R&D program. The study involved coordinated efforts by four independent contractors to conceive and quantify fuel-conserving technology alternatives, transform these alternatives into viable R&D options, and simulate each option in a general model of the U.S. domestic air transportation system. This paper deals primarily with the latter phase and concentrates on the results of the study, as revealed not only by estimated fuel usage but also by other impacts of the technology options, such as demand growth, operator economics, and fleet composition. However, while the paper focuses on results, the basic assumptions and technology inputs are documented, and a general description of the modeling approach is provided to demonstrate the level of detail considered in the analysis.

Gobetz, F. W.↗

NASA NTRS1977

A factory concept for processing and manufacturing with lunar material

A conceptual design for an orbital factory sized to process 1.5 million metric tons per year of raw lunar fines into 0.3 million metric tons of manufacturing materials is presented. A conservative approach involving application of present earth-based technology leads to a design devoid of new inventions. Earth based counterparts to the factory machinery were used to generate subsystem masses and lumped parameters for volume and mass estimates. The results are considered to be conservative since technologies more advanced than those assumed are presently available in many areas. Some attributes of potential space processing technologies applied to material refinement and component manufacture are discussed.

Driggers, G. W.↗

NASA NTRS1976

Impact ejecta on the moon

The response of a lunar-sized object to the impact of meteoroids no more than about 100 km in radius is studied by means of a numerical model. The partitioning of impact energy into the kinetic and internal energy of the ejecta is obtained by using the conservation of mass, momentum, and energy conservation equations in finite-difference form within an Eulerian framework with approximate equations of state. The calculations are performed for a 15 km/sec impact of an iron object 5 cm in radius on a gabbroic anorthosite surface. Ejecta ballistic analysis is then performed. Most of the material lost escaping the moon is lunar crust material. Only 0.2% of the meteoroid escapes, all in the vapor phase.

Okeefe, J. D.↗

NASA NTRS1977

An implicit factored scheme for the compressible Navier-Stokes equations

An implicit finite difference scheme is developed for the numerical solution of the compressible Navier-Stokes equations in conservation-law form. The algorithm is second-order-time accurate, noniterative, and spatially factored. In order to obtain an efficient factored algorithm, the spatial cross-derivatives are evaluated explicitly. However, the algorithm is unconditionally stable and, although a three-time-level scheme, requires only two-time-levels of data storage. The algorithm is constructed in a 'delta' form (i.e., increments of the conserved variables and fluxes) that provides a direct derivation of the scheme and leads to an efficient computational algorithm. In addition, the delta form has the advantageous property of a steady-state (if one exists) independent of the size of the time step. Numerical results are presented for a two-dimensional shock boundary-layer interaction problem.

Beam, R. M.↗

NASA NTRS1977

Gravitational scattering of zero-rest-mass plane waves

The Feyman-diagram technique is used to calculate the differential cross sections for the scattering of zero-rest-mass plane waves of spin 0, 1, and 2 by linearized Schwarzschild and Kerr geometries in the long-wavelength weak-field limit. It is found that the polarization of right (or left) circularly polarized electromagnetic waves is unaffected by the scattering process (i.e., helicity is conserved) and that the two helicity (polarization) states of the photon are scattered differently by the Kerr geometry. This coupling between the photon helicity and the angular momentum of the scatterer also leads to a partial polarization of unpolarized incident light. For gravitational waves, on the other hand, there is neither helicity conservation nor helicity-dependent scattering; the angular momentum of the scatterer has no polarizing effect on incident unpolarized gravitational waves.

De Logi, W. K.↗

NASA NTRS1977

The 4th order GISS model of the global atmosphere

The new GISS 4th order model of the global atmosphere is described. It is based on 4th order quadratically conservative differences with the periodic application of a 16th order filter on the sea level pressure and potential temperature equations, a combination which is approximately enstrophy conserving. Several short range forecasts indicate a significant improvement over 2nd order forecasts with the same resolution (approximately 400 km). However the 4th order forecasts are somewhat inferior to 2nd order forecasts with double resolution. This is probably due to the presence of short waves in the range between 1000 km and 2000 km, which are computed more accurately by the 2nd order high resolution model. An operation count of the schemes indicates that with similar code optimization, the 4th order model will require approximately the same amount of computer time as the 2nd order model with the same resolution. It is estimated that the 4th order model with a grid size of 200 km provides enough accuracy to make horizontal truncation errors negligible over a period of a week for all synoptic scales (waves longer than 1000 km).

Kalnay-Rivas, E.↗

NASA NTRS1976

Cost/benefit tradeoffs for reducing the energy consumption of the commercial air transportation system

The fuel saving potential and cost effectiveness of numerous operational and technical options proposed for reducing the fuel consumption of the U.S. commercial airline fleet was examined and compared. The impact of the most promising fuel conserving options on fuel consumption, passenger demand, operating costs and airline profits when implemented in the U.S. domestic and international airline fleets was determined. A forecast estimate was made of the potential fuel savings achievable in the U.S. scheduled air transportation system. Specifically, the means for reducing the jet fuel consumption of the U.S. scheduled airlines in domestic and international passenger operations were investigated. A design analysis was made of two turboprop aircraft as possible fuel conserving derivatives of the DC-9-30.

Kraus, E. F.↗

NASA NTRS1977

Numerical calculation of transonic flow past a swept wing by a finite volume method

The utility of numerical methods for predicting transonic flows over wings and bodies is well established. The computer program FLO22, based on a method presented earlier, has actually been widely used to calculate the aerodynamic performance of wings of transport aircraft. Provided that a correction is made for the displacement effect of the viscous boundary layer, this code has been found to give predictions which are accurate enough to serve as a useful design guide. The main disadvantages of the scheme used in FLO22 are the use of nonconservative difference formulas, which result in a failure to satisfy conservation of mass across shock waves, and the difficulty of finding suitable transformations of coordinates to permit the treatment of more complex geometric configurations. The method described here is an attempt to overcome these shortcomings, while retaining the successful features of the previous method. The basic idea is to use a discrete approximation which directly represents a balance of the mass flow through small volume elements. This leads to a relatively simple treatment of the potential flow equation in conservation form.

Jameson, A.↗

NASA NTRS1977

Atmospheric model development in support of SEASAT. Volume 3: Prediction models

As part of the SEASAT program of NASA, a set of four hemispheric, atmospheric models are developed. The four models use a polar stereographic grid in the horizontal and a sigma coordinate in the vertical. Conservation forms of the difference equations are integrated using either a fifteen or four minute time step on a 381 km or 127 km grid (at 60 deg N) for the 63 x 63 or 187 x 187 models respectively. A nonlinear pressure smoother is used along with momentum and temperature diffusion to help control computational noise. The horizontal boundary conditions are insulated slippery walls. Centered time differencing with time averaging of the pressure gradient force term in the momentum equations is used. Robert time filtering on of the temperature and moisture solutions is used for computational stability. The moisture and heat source/sink terms are modeled. Terms representing evaporation and large scale condensation, sensible heat exchange, parameterized cumulus convection and precipitation, and solar and terrestrial radiation are included. Initialization of the models is based on a pattern conservation technique to obtain objective analysis of the state parameter structure from the surface to 50 mb.

Wellck, R. E.↗

NASA NTRS1978

An overview of the energy situation

Beginning with a historical review of the domestic pattern of energy usage, the current dependence of the United States upon dwindling petroleum resources is examined. The possible limit of petroleum usage is discussed, and recent oil production trends are presented. Coupling these with projected analyses of OPEC oil productive capability in the early 1980's indicates a serious worldwide as well as American energy problem in the next decade. The need for conservation and rapid development of application of alternative energy resources is discussed including quantitative projections of significant conservation efforts as well as estimates of domestic alternative energy resource capabilities.

Pitts, D. R.↗

NASA NTRS1978

Applications of thermal energy storage in the cement industry

In the manufacture of cement, literally trillions of Btu's are rejected to the environment each year. The purpose of this feasibility study program was to determine whether thermal energy storage could be used to conserve or allow alternative uses of this rejected energy. This study identifies and quantifies the sources of rejected energy in the cement manufacturing process, established use of this energy, investigates various storage system concepts, and selects energy conservation systems for further study. Thermal performance and economic analyses are performed on candidate storage systems for four typical cement plants representing various methods of manufacturing cement. Through the use of thermal energy storage in conjunction with waste heat electric power generation units, an estimated 2.4 x 10 to the 13th power Btu/year, or an equivalent on investment of the proposed systems are an incentive for further development.

Jaeger, F. A.↗

NASA NTRS1977

The response of a constant-volume balloon to periodic three-dimensional flow

A theoretical treatment is presented of the motion of a constant-volume balloon immersed in a three-dimensional spatially nonhomogeneous periodic flow field with a mean translational flow velocity. The governing equations are the equations of conservation of momentum of the balloon, coupled with the equations of conservation of momentum of the fluid. In the mathematical model employed, the flow field is represented by a periodic function. The numerical results are in general agreement with observations. Noteworthy is that the balloon does not move with the same mean velocity as the wind and, thus, when Taylor's hypothesis for the fluid is satisfied, the balloon does not 'lock in' with the wind velocity. When Taylor's hypothesis for the parcel is satisfied, however, the balloon does match the mean wind direction (but not its speed).

Tatom, F. B.↗

NASA NTRS1978

Extensions of guiding center motion to higher order

In a static magnetic field, some well-known guiding-center equations maintain their form when extended to next order in gyroradius. In these cases, it is only necessary to include the next order term in the magnetic moment series. The differential equation for guiding-center motion which describes both the parallel and perpendicular velocities correctly through first order in gyroradius is given. The question of how to define the guiding center position through second order arises and is discussed, and second order drifts are derived for one usual definition. The toroidal canonical angular momentum, P-phi, of the guiding center in an axisymmetric field is shown to be conserved using the guiding center velocity correct through first order. When second-order motion is included, P-phi is no longer a constant. The above extensions of guiding-center theory help to resolve the different tokamak orbits obtained either by using the guiding-center equations of motion or by using conservation of P-phi.

Northrop, T. G.↗