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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 631 records · Page 35

Second Symposium on Protection Against Radiations in Space

All space vehicles will be exposed to natural charged particle radiation fields. The effects and possible problems imposed by such radiations are of great concern to those actively engaged in the exploration of space. Materials and components, which may be damaged by the radiation, frequently can be replaced by more radiation resistant items; however, replacement systems are not always possible or practical and, hence, protective measures in the form of shielding must be employed. (One of the more radiation-sensitive systems to be flown in space is man himself.) Many groups are engaged in research on the attenuation and penetration of high-energy space radiation and on the development of methods for the design of shielding which affords protection against the radiation. The purpose of the Second Symposium on Protection Against Radiations in Space, like that of the First, was to bring these groups together to exchange information and share ideas. These proceedings are the written record of the Second Symposium. Invited papers covering the space radiation environment, radiobiological effects, and radiation effects on materials and components comprised the first three sessions. By defining the radiation problems in space and providing for the proper assessment of the radiation effects and shielding requirements, these papers helped to establish the necessary background for the shielding papers which followed in the fourth session.

radiation protection↗

A second-generation /high-speed/ maximum power tracker for space applications.

During the past few years, considerable effort has been exerted by both industry and government to improve the performance of space power systems. One of the significant advances has been the development of practical Maximum Power-Point Tracking (MPPT) systems. This paper presents the background and evolution of a second-generation (high-speed) MPPT system capable of operation with solar arrays with rapidly fluctuating parameters due to mission operation (e.g., spin-stabilized spacecraft). An experimental model of the high-speed MPPT system has been constructed and tested. Results from these tests are presented herein. The second-generation MPPT system provides a means of efficient power conditioning that can result in significant increases over conventional systems in space-power system capability. Of additional importance is the applicability of the basic technology to all types of spacecraft, and the wide variety of power-system configurations with which the high-speed MPPT system concept may be used.

Clement A. Berard, Jr.↗

Study of second breakdown in power transistors using infrared techniques

Infrared thermal maps pinpoint exact location where second breakdown will occur before phenomenon happens and before physical damage develops at hot spot. Crystal structure analysis at that point determines cause of fault. Absolute power of radiation emitted from hot spot is direct indication of voltage level at which second breakdown occurs

Source record↗

A statistical mechanical calculation of the thermodynamic properties of interstitial solid solutions involving second nearest neighbor interactions.

A previous calculation of the thermodynamic properties of interstitial solid solutions based on the technique of Kirkwood expansions has been extended to include the effects of second nearest neighbor solute atom mutual interactions. The error inherent in the first order (or quasi-chemical) counting of the degeneracy of the solution crystal is avoided. It is shown that, at high temperatures, even strong second nearest neighbor solute mutual interactions have a negligible effect on the entropy of the solution and a small, temperature-dependent effect on the solute partial enthalpy.

Alex, K.↗

Expendable second stage reusable space shuttle booster. Volume 4: Detail mass properties data

Mass properties data are presented to describe the characteristics of an expendable second stage with a reusable space shuttle booster. The final mass characteristics of the vehicle configurations for three specified payloads are presented in terms of weight, center of gravity, and mass moments of inertia. Three basic subjects are the integrated vehicle system, the expendable second stage, and the booster modifications.

Source record↗

Expendable Second Stage Reusable Space Shuttle Booster: Preliminary System Specification - Volume 9

The specification for establishing the requirements for the system performance, design, development, and ground and flight operations of the expendable second stage on a reusable space shuttle booster system is presented. The basic specification is that the system shall be capable of placing payloads in excess of 100,000 pounds into earth orbit. In addition, the expendable second stage provides a multimission, economical, large capability system suitable for a variety of space missions in the 1980 time period.

Source record↗

Effect of diffusional creep on particle morphology of polycrystalline alloys strengthened by second phase particles

Diffusional creep in a polycrystalline alloy containing second-phase particles can disrupt the particle morphology. For alloys which depend on the particle distribution for strength, changes in the particle morphology can affect the mechanical properties. Recent observations of diffusional creep in alloys containing soluble particles (gamma-prime strengthened Ni base alloys) and inert particles have been reexamined in light of the basic mechanisms of diffusional creep, and a generalized model of this effect is proposed. The model indicates that diffusional creep will generally result in particle-free regions in the vicinity of grain boundaries serving as net vacancy sources. The factors which control the changes in second-phase morphology have been identified, and methods of reducing the effects of diffusional creep are suggested.

Wittenberger, J. D.↗

Overall and blade-element performance of a transonic compressor stage with multiple-circular-arc blades at tip speed of 419 meters per second

A 50-centimeter-diameter axial-flow transonic compressor stage with multiple-circular-arc blades was designed and tested to study the effects of blade shape on efficiency and stall margin. At design speed, peak efficiency of 0.80 occurred at an equivalent weight flow of 29.0 kilograms per second. Measured total pressure ratio and total temperature ratio at peak efficiency were 1.69 and 1.20, respectively. The stall margin at design speed and an equivalent weight flow of 29.0 kilograms per second was 9 percent. The measured stall margin at design weight flow and speed was 15 percent. A comparison of rotor performance made with and without the stator showed a decrease in pressure ratio, peak efficiency, and maximum weight flow with the addition of the stator.

Kovich, G.↗

Research on the sonic boom problem. Part 1: Second-order solutions for the flow field around slender bodies in supersonic flow for sonic boom analysis

A second-order theory for supersonic flow past slender bodies is presented. Through the introduction of characteristic coordinates as independent variables and the expansion procedure proposed by Lin and Oswatitsch, a uniformly valid solution is obtained for the whole flow field in the axisymmetric case and for far field in the general three-dimensional case. For distances far from the body the theory is an extension of Whitham's first-order solution and for the domain close to the body it is a modification of Van Dyke's second-order solution in the axisymmetric case. From the theory useful formulas relating flow deflections to the Whitham F-function are derived, which permits one to determine the sonic boom strength from wind tunnel measurements fairly close to the body.

Landahl, M.↗

Phase matching in second-harmonic generation using artificial periodic structures.

The use of artificial periodic structures, consisting of spatial modulations of the linear and nonlinear susceptibilities of a nonlinear optical medium, to achieve phase matching in second-harmonic generation is analyzed. Dispersion relations and approximate formulas for the second-harmonic fields generated under various conditions are obtained and used to evaluate the experimental situation.

Tang, C. L.↗

Second derivatives of the flutter velocity and the optimization of aircraft structures.

Equations for the second partial derivatives of the eigenvalues of the flutter equation along with the equations for finding the second partial derivatives of the flutter velocity of an aircraft structure with respect to the structural parameters are derived. These partial derivatives are used to develop expressions for the step size in a projected gradient search along a constant mass hyperlane. A projected gradient search along with a gradient mass and a gradient velocity search is used to minimize the mass of a box beam which supports a lifting surface.

Rudisill, C. S.↗

The prevalence of second harmonic radiation in type III bursts observed at kilometric wavelengths.

We present the analysis of 64 type III solar bursts that drifted from 3.5 MHz down to the range 350-50 kHz between March 1968 and February 1970. Bursts arrival times were predicted by a simple model and then compared with observations. The results show that, as the bursts drift, the fundamental often disappears below a certain frequency range while the second harmonic remains. Below about 1 MHz, the second harmonic occurrence predominates. Recognizing this fact we deduce a mean velocity of 0.32c plus or minus 0.02c for the exciter particles, where the uncertainty is the standard error and c the velocity of light in vacuum; the electron density model used is comparable to a solar wind model.

Haddock, F. T.↗