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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Reward and uncertainty in exploration programs

A set of variables which are crucial to the economic outcome of petroleum exploration are discussed. These are treated as random variables; the values they assume indicate the number of successes that occur in a drilling program and determine, for a particular discovery, the unit production cost and net economic return if that reservoir is developed. In specifying the joint probability law for those variables, extreme and probably unrealistic assumptions are made. In particular, the different random variables are assumed to be independently distributed. Using postulated probability functions and specified parameters, values are generated for selected random variables, such as reservoir size. From this set of values the economic magnitudes of interest, net return and unit production cost are computed. This constitutes a single trial, and the procedure is repeated many times. The resulting histograms approximate the probability density functions of the variables which describe the economic outcomes of an exploratory drilling program.

Kaufman, G. M.↗
NASA NTRS1972

Measurements of the energy exchange between earth and space from satellites during the 1960's

The net radiation budget of the earth-atmosphere system can be obtained from satellite measurements of the infrared radiant emittance and reflected and scattered solar radiation along with a knowledge of the solar constant. During the 1960's experimental and operational meteorological satellites carrying thermistor bolometer sensors were in orbit for about 60 months. Results from these measurements are given including: a global planetary albedo of 30%, long-term global radiation balance within measurement accuracy (2-3%), the net equator-to-pole radiation gradients that drive our atmospheric and oceanic circulations, as well as selected measurements of radiation budget terms over particular geographical areas.

Vonderhaar, T. H.↗
NASA NTRS1972

Nacelle-airframe interference at low supersonic Mach numbers.

The aerodynamic interference between the propulsion system and airframe for a low supersonic transport with wing-mounted nacelles is examined. Both a flowfield analysis and the equivalent body approach were used to predict the interference lift, drag, and pitching moment as functions of nacelle size, shape, and position. The results indicate that the interference lift and pitching moment, as well as drag, must be included in the analysis to properly assess the interference effects. In addition, the performance of the basic wing was found to play an important role in determining the effectiveness of the interference lift in reducing the net installation drag. Based on a conservative prediction, the interference effects can reduce the installed propulsion system drag to 40% of the isolated drag of the nacelles. Furthermore, including the interference effects in the optimization of the engine cycle from a thermodynamic and weight standpoint can result in a considerable reduction in the net propulsion system weight fraction (fuel plus engines) while increasing the optimum engine bypass ratio of a typical transport vehicle.

Bencze, D. P.↗
NASA NTRS1974

The use of COD and plastic instability in crack propagation and arrest in shells

The initiation, growth, and possible arrest of fracture in cylindrical shells containing initial defects are dealt with. For those defects which may be approximated by a part-through semi-elliptic surface crack which is sufficiently shallow so that part of the net ligament in the plane of the crack is still elastic, the existing flat plate solution is modified to take into account the shell curvature effect as well as the effect of the thickness and the small scale plastic deformations. The problem of large defects is then considered under the assumptions that the defect may be approximated by a relatively deep meridional part-through surface crack and the net ligament through the shell wall is fully yielded. The results given are based on an 8th order bending theory of shallow shells using a conventional plastic strip model to account for the plastic deformations around the crack border.

Erdogan, F.↗
NASA NTRS1973

Cyclotron resonance wave amplification in the magnetosphere and energetic particle stability

Detailed electron distribution measurements in the outer magnetosphere now available indicate that the energetic electron anisotropy may be very energy dependent, there being positive anisotropies near the magnetic equator for low-energy particles and negative anisotropies in this region for high-energy particles. Previous wave growth calculations assuming the energetic particle anisotropy to be independent of energy are inaccurate at high energies. The net one-hop whistler mode wave amplification is calculated as a function of frequency for a measured electron distribution at L = 7 for a number of assumed equatorial plasma densities. It is found that an increase in cold plasma density results in a change from a net wave damping to significant wave amplification.

Lucas, C.↗
NASA NTRS1974

Lineaments in basement terrane of the Peninsular Ranges, Southern California

The author has identified the following significant results. ERTS and Skylab images reveal a number of prominent lineaments in the basement terrane of the Peninsular Ranges, Southern California. The major, well-known, active, northwest trending, right-slip faults are well displayed; northeast and west to west-northwest trending lineaments are also present. Study of large-scale airphotos followed by field investigations have shown that several of these lineaments represent previously unmapped faults. Pitches of striations on shear surfaces of the northeast and west trending faults indicate oblique slip movement; data are insufficient to determine the net-slip. These faults are restricted to the pre-tertiary basement terrane and are truncated by the major northwest trending faults. They may have been formed in response to an earlier stress system. All lineaments observed in the space photography are not due to faulting, and additional detailed geologic investigations are required to determine the nature of the unstudied lineaments, and the history and net-slip of fault-controlled lineaments.

Merifield, P. M.↗
NASA NTRS1975

Method of predicting radiation heat transfer in turbine cooling test facilities

A method is presented for calculating the average net radiation heat flux to turbine vanes and blades. The net radiation heat flux at a vane leading edge calculated by this method was compared with heat flux values independently determined from experimental tests on a vane in a cascade. The spectral emissivities of the turbine vane and the cascade wall were also measured.

Gladden, H. J.↗
NASA NTRS1975

Analytic and experimental evaluation of flowing air test conditions for selected metallics in a shuttle TPS application

A detailed experimental and analytical evaluation was performed to define the response of TD nickel chromium alloy (20 percent chromium) and coated columbium (R512E on CB-752 and VH-109 on WC129Y) to shuttle orbiter reentry heating. Flight conditions important to the response of these thermal protection system (TPS) materials were calculated, and test conditions appropriate to simulation of these flight conditions in flowing air ground test facilities were defined. The response characteristics of these metallics were then evaluated for the flight and representative ground test conditions by analytical techniques employing appropriate thermochemical and thermal response computer codes and by experimental techniques employing an arc heater flowing air test facility and flat face stagnation point and wedge test models. These results were analyzed to define the ground test requirements to obtain valid TPS response characteristics for application to flight. For both material types in the range of conditions appropriate to the shuttle application, the surface thermochemical response resulted in a small rate of change of mass and a negligible energy contribution. The thermal response in terms of surface temperature was controlled by the net heat flux to the surface; this net flux was influenced significantly by the surface catalycity and surface emissivity. The surface catalycity must be accounted for in defining simulation test conditions so that proper heat flux levels to, and therefore surface temperatures of, the test samples are achieved.

Schaefer, J. W.↗
NASA NTRS1974

Cosmic ray anisotropies observed late in the decay phase of solar flare events

Data was obtained from instrumentation on Explorers 34 and 41 on cosmic-ray anisotropy and magnetic field vectors during five solar flare events. The analysis was conducted in the energy range from 0.7 to 7.6 MeV, of the late decay phase, to evaluate the dependence of net cosmic-ray anisotropy vector amplitude and direction on the magnetic field azimuth. Results showed that in the late decay phase the direction of the net cosmic-ray anisotropy vector was invariant in relation to the direction of the magnetic field, particle energy, and species. Within the statistical error of the available data the invariant direction was perpendicular to the mean magnetic field direction.

Allum, F. R.↗
NASA NTRS1976

Improved insulation material

Multilayer material consisting of embossed, silver-coated Mylar, nylon net, and silk net is useful for thermal-protection systems and cryogenic containers. Embossing serves two purposes: helps separate radiation barriers and controls radiant energy diffusion. Insulation requires no maintenance after installation.

Source record↗
NASA NTRS1975

Field-aligned currents observed by the OGO 5 and Triad satellites

The existence of field-aligned currents in the polar cap boundary layer as a permanent feature of the magnetosphere is investigated. Magnetic field observations from Triad at 800 km altitude and from OGO 5 in the high-altitude magnetosphere are examined. Results indicate that in the morning half of the boundary layer, currents flow into the ionosphere, and that the current direction is reversed in the afternoon half of the layer. The Triad data further indicate that the net current is a maximum near 1500 MLT and that there may be a secondary maximum during early morning hours. According to the Isis 2 electron observations, the locations of these maximums of field-aligned net current roughly match those of two maximums in the isointensity contours for 150 ev electrons. It is proposed that the polar cap boundary current is driven by a current generator in the magnetotail, or ultimately in the solar wind. It is suggested that the large scale field-aligned currents in the polar cap boundary layer are associated with the dominance of protons on the morning side and of electrons on the afternoon side near the poleward edge of the precipitation zone along the auroral oval.

Sugiura, M.↗
NASA NTRS1975

AESC multinodal free molecular contamination transport model

The film formation effects are examined of self-induced clouds and condensed films of volatile condensible materials (VCMs) which outgas from such sources as paints, coatings, adhesives, and other nonmetallic surfaces of satellites. A semi-empirical theory for the multiple scattering of free neutral molecules from dielectric surfaces which includes the effects of condensation and evaporation is defined and a mathematical model of the process is developed. The formation rate of thin surface films is considered to be the net accumulation of two simultaneous molecular processes; emission (evaporation) and adsorption (condensation). The net formation rate is considered to be dependent upon the temperature of the surface nodes, the mass and temperatures of the gas molecules, and the total pressure of the incident molecular flux. Apparatus and procedures for measuring these parameters are presented.

Zeiner, E. A.↗
NASA NTRS1975

ECASTAR methodology

The methodology used for the ECASTAR study was described. A systems approach was utilized, in conjunction with the following tools: input/output economic analysis, net economics, and net energetics. Some of the considerations between the objective of ECASTAR, which is to assess the potential for and impacts of various energy conservation actions, were listed. These include: data base, constraints and criteria, identification and classification of energy conservation actions, relationship between actions of the conservation sector and requirements of other sectors, evaluation of actions with respect to constraints and criteria, evaluation of impacts of energy conservation actions, and presentation of the results. Each one of these topics was discussed.

Source record↗
NASA NTRS1975

A study of sound generation in subsonic rotors, volume 1

A model for the prediction of wake related sound generation by a single airfoil is presented. It is assumed that the net force fluctuation on an airfoil may be expressed in terms of the net momentum fluctuation in the near wake of the airfoil. The forcing function for sound generation depends on the spectra of the two point velocity correlations in the turbulent region near the airfoil trailing edge. The spectra of the two point velocity correlations were measured for the longitudinal and transverse components of turbulence in the wake of a 91.4 cm chord airfoil. A scaling procedure was developed using the turbulent boundary layer thickness. The model was then used to predict the radiated sound from a 5.1 cm chord airfoil. Agreement between the predicted and measured sound radiation spectra was good. The single airfoil results were extended to a rotor geometry, and various aerodynamic parameters were studied.

Chalupnik, J. D.↗
NASA NTRS1975

Study to evaluate the effect of EVA on payload systems. Volume 1: Executive summary

Programmatic benefits to payloads are examined which can result from the routine use of extravehicular activity (EVA) during space missions. Design and operations costs were compared for 13 representative baseline payloads to the costs of those payloads adapted for EVA operations. The EVA-oriented concepts developed in the study were derived from these baseline concepts and maintained mission and program objectives as well as basic configurations. This permitted isolation of cost saving factors associated specifically with incorporation of EVA in a variety of payload designs and operations. The study results were extrapolated to a total of 74 payload programs. Using appropriate complexity and learning factors, net EVA savings were extrapolated to over $551M for NASA and U.S. civil payloads for routine operations. Adding DOD and ESRO payloads increases the net estimated savings of $776M. Planned maintenance by EVA indicated an estimated $168M savings due to elimination of automated service equipment. Contingency problems of payloads were also analyzed to establish expected failure rates for shuttle payloads. The failure information resulted in an estimated potential for EVA savings of $1.9 B.

Patrick, J. W.↗
NASA NTRS1976

Crack propagation and arrest in pressurized containers

The problem of crack propagation and arrest in a finite volume cylindrical container filled with pressurized gas is considered. It is assumed that the cylinder contains a symmetrically located longitudinal part-through crack with a relatively small net ligament. The net ligament suddenly ruptures initiating the process of fracture propagation and depressurization in the cylinder. Thus the problem is a coupled gas dynamics and solid mechanics problem the exact formulation of which does not seem to be possible. The problem is reduced to a proper initial value problem by introducing a dynamic fracture criterion which relates the crack acceleration to the difference between a load factor and the corresponding strength parameter. The results indicate that generally in gas filled cylinders fracture arrest is not possible unless the material behaves in a ductile manner and the container is relatively long.

Erdogan, F.↗
NASA NTRS1976

Cost benefit analysis of space communications technology: Volume 1: Executive summary

The questions of (1) whether or not NASA should support the further development of space communications technology, and, if so, (2) which technology's support should be given the highest priority are addressed. Insofar as the issues deal principally with resource allocation, an economics perspective is adopted. The resultant cost benefit methodology utilizes the net present value concept in three distinct analysis stages to evaluate and rank those technologies which pass a qualification test based upon probable (private sector) market failure. User-preference and technology state-of-the-art surveys were conducted (in 1975) to form a data base for the technology evaluation. The program encompassed near-future technologies in space communications earth stations and satellites, including the noncommunication subsystems of the satellite (station keeping, electrical power system, etc.). Results of the research program include confirmation of the applicability of the methodology as well as a list of space communications technologies ranked according to the estimated net present value of their support (development) by NASA.

Holland, L. D.↗
NASA NTRS1975

Drift-free magnetic geometries in adiabatic motion

There exist magnetic fields in which particles bouncing between mirror points experience no net first-order guiding center drift. In such fields, even though the instantaneous gradient and curvature drifts are not zero, their total effect integrated over any bounce period vanishes, so that particles merely wobble back and forth around fixed field lines. A class of two-dimensional drift-free fields, somewhat resembling the configuration found in the geomagnetic tail, is described; several proofs of the drift-free property are given, including some that suggest that the property of vanishing net drift might extend to nonadiabatic orbits. A general criterion for identifying drift-free fields is developed, and a case of motion in a nearly drift-free field is also investigated. The theory is applied to the plasma sheet in the earth's magnetotail, and observational evidence is presented suggesting that the magnetic field there indeed approaches a drift-free configuration.

Stern, D. P.↗