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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 1,063 records · Page 59

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NASA NTRS1992

Is the earth's magnetotail balloon unstable?

In the past, the onset of magnetospheric substorms has been attributed to the plasma tearing mode instabilities. This paper investigates the ideal MHD ballooning instability of the near-and middle-tail magnetosphere region, as a first step toward determining whether it could trigger the tearing mode, by using the energy principle to investigate whether standard 2D tail models with the 'hard' ionospheric boundary condition are unstable to ballooning instability. Numerical results are presented for compressible ballooning modes that are symmetric about the center of the current sheet. It is shown that, for such a hard boundary condition, no reasonable magnetotail configuration exists that would be unstable to compressible symmetric ballooning but stable against interchange.

Lee, D.-Y.↗

NASA NTRS1993

Experiments on the stability of a liquid bridge in an axial electric field

The behavior of a neutrally buoyant liquid bridge was studied in the presence of axial electric fields. Silicone oil and a castor-oil-eugenol mixture were used to form cylinders with slenderness ratios larger than pi with strong, axial, dc electric fields. Below a certain field strength, a smooth transition to an axisymmetric, vaselike shape occurred. Circulation patterns were observed in these bridges. At lower field strengths, the bridge shape was more deformed and, at a well-defined field, pinch-off occurred. With ac fields, the field strength required to stabilize the bridge was higher and the collapse of the cylinder was much sharper. Upon interchanging the fluids, a steady axial field was found to destabilize cylinders with slenderness ratios less than 3. This behavior is consistent with that anticipated if the fluids behave as leaky dielectrics but not if they act as perfect dielectrics.

Sankaran, Subramanian↗

NASA NTRS1991

ControlShell - A real-time software framework

ControlShell is designed to enable modular design and impplementation of real-time software. It is an object-oriented tool-set for real-time software system programming. It provides a series of execution and data interchange mechansims that form a framework for building real-time applications. These mechanisms allow a component-based approach to real-time software generation and mangement. By defining a set of interface specifications for intermodule interaction, ControlShell provides a common platform that is the basis for real-time code development and exchange.

Schneider, Stanley A.↗

NASA NTRS1991

Tropospheric Emission Spectrometer for the Earth Observing System

A Tropospheric Emission Spectrometer (TES) for the Earth Observing System (EOS) series of polar-orbiting platforms is described. TES is aimed at studying tropospheric chemistry, in particular, the exchange of gases between the surface and the atmosphere, urban and regional pollution, acid rain precursors, sources and sinks of greenhouse gases, and the interchange of gases between the troposphere and the stratosphere. TES is a high-resolution (0.025/cm) infrared Fourier transform spectrometer operating in the passive thermal-emission mode in a very wide spectral range (600 to 4350/cm; 2.3 to 16.7 microns). TES has 32 spatial pixels in each of four optically conjugated linear detector arrays, each optimized for a different spectral region.

Glavich, Thomas A.↗

NASA NTRS1993

Development of an iron nitrate resistant injector valve for the Space Shuttle orbiter primary thruster

Design of a direct-acting valve (DAV) for a primary thruster which is fully interchangeable with a thruster equipped with pilot-operated valves is described. The DAV is based on a bellows to isolate propellants form the actuator for maximum resistance to iron nitrate and other contamination and to select optimum materials for the actuator. It provides improved seal performance under all operating conditions and insensitivity to pressure transients. As compared with the existing pilot-operated valve, the DAV design is much simpler, consists of fewer parts, and will be lower in cost.

Wichmann, Horst↗

NASA NTRS1993

Demonstration of Fabry-Perot interferometric spectrometry technology

As rocket engine components experience wear or failure, anomalous materials may be entrained in the plume. Historically, visible plume anomalies have preceded many rocket engine failures, some of which have been catastrophic. Development of a small, rugged, high-speed, high resolution Fabry-Perot interferometer (FPI) based spectrometer capable of detecting the spectral signatures of eroding engine components during rocket engine test and/or flight operations is described. An operational plume spectrometer fabricated with miniaturized optics has been successfully tested. An extensive test series was conducted to define the limits of the spectrometer with respect to time-response and resolution. The data collected during testing were correlated with measurements obtained using sensitive ground equipment in order to benchmark the spectrometer's performance against a known device. The FPI demonstrated the reliability required for a flight instrument by functioning satisfactorily at or near the rocket engine test stand environment. Several of the optical components are interchangeable, allowing collection of a greater variety of plume signals. Also, the FPI's high resolution capabilities suggest it is suitable for application to both absorption and emission spectroscopy.

Petersen, T. V.↗

NASA NTRS1993

Thermal emissivity analysis of a GEMINI 8-meter telescopes design

The GEMINI 8-meter Telescopes Project is designing twin 8-meter telescopes to be located in Hawaii and Chile. The GEMINI telescopes will have interchangeable secondary mirrors for use in the visible and IR. The APART/PADE program is being used to evaluate the effective IR emissivity of the IR configuration plus enclosure as a function of mirror contamination at three IR wavelengths. The goal is to design a telescope whose effective IR emissivity is no more than 2 percent when the mirrors are clean.

St. Clair Dinger, Ann↗

NASA NTRS1993

Three-dimensional magnetohydrodynamics of the emerging magnetic flux in the solar atmosphere

The nonlinear evolution of an emerging magnetic flux tube or sheet in the solar atmosphere is studied through 3D MHD simulations. In the initial state, a horizontal magnetic flux sheet or tube is assumed to be embedded at the bottom of MHD two isothermal gas layers, which approximate the solar photosphere/chromosphere and the corona. The magnetic flux sheet or tube is unstable against the undular mode of the magnetic buoyancy instability. The magnetic loop rises due to the linear and then later nonlinear instabilities caused by the buoyancy enhanced by precipitating the gas along magnetic field lines. We find by 3D simulation that during the ascendance of loops the bundle of flux tubes or even the flux sheet develops into dense gas filaments pinched between magnetic loops. The interchange modes help produce a fine fiber flux structure perpendicular to the magnetic field direction in the linear stage, while the undular modes determine the overall buoyant loop structure. The expansion of such a bundle of magnetic loops follows the self-similar behavior observed in 2D cases studied earlier. Our study finds the threshold flux for arch filament system (AFS) formation to be about 0.3 x 10 exp 20 Mx.

Matsumoto, R.↗

NASA NTRS1985

Biologically produced volatile compounds: N2O emissions from the soil and the N2O global budget

N2O dynamics were studied at the soil-atmosphere interface and their effects on the global N2O budget. Troposphere nitrous oxide (N2O) concentration has increased by 0.2 to 0.4 pct. per year over the period 1975 to 1982, amounting to a net addition to the atmosphere of 2.8 to 5.6 Tg N2O-N per year. This perturbation, if continued into the future, will affect stratospheric chemical cycles, and the thermal balance of the Earth. In turn it will have direct and indirect global effects on the biosphere. The only well documented heat sinks identified to date are the stratospheric photolytic decomposition processes. However, quantitatively, they do not account for all the known sources. Emission from soils is the least understood and most variable component in the N2O budget. An automated field station that will measure N2O fluxes and interchanges over long periods of time is being developed. At each station, the source/sink relations of N2O at the soil-atmosphere interface will be measured and their relations to environmental conditions are documented and quantified. The results from the perennial measurements will generate the data base on which global budgets for N2O will be constructed and related to ecosystem parameters.

Banin, A.↗

NASA NTRS1988

Three-legged mobile platform: SKITTER

Described herein is a system of equipment intended for site preparation and construction of a lunar base. The proximate era of lunar exploration and the initial phase of outpost habitation are addressed. Drilling, mining, and benefication of lunar soil prior to pilot-plant oxygen extraction and other soil processing techniques are included within the scope of this system's capabilities. The centerpiece of the design is the SKITTER mobile walking, site preparation, and construction planform. The SKITTER system is modular in nature and includes a series of interchangeable implements whose individual use tends to be seasonal or intermittent. The concept is analogous to the farmer's tractor and implement set. The proposed system is mechanically simple and weight efficient and the individual implements are designed to take advantage of the lunar environment while operating within the constraints imposed by that environment. The system's implement interfaces can also be used for transporting containerized cargo on the lunar surface. A proposed lunar orbit to lunar surface landing pod might also be used to deliver the walker and crane boom combination in a ready-to-work configuration.

Source record↗

NASA NTRS1937

Free-spinning Wind-tunnel Tests of a Low-wing Monoplane with Systemic Changes in Wings and Tails

A series of tests was made at the National Advisory Committee for Aeronautics (NACA) free-spinning tunnel to determine the effect of systematic changes in wing and tail arrangement upon steady-spinning and recovery characteristics of a conventional low-wing monoplane model for a basic loading condition. Eight wings and three tails, covering a wide range of aerodynamic characteristics, were independently ballasted so as to be interchangeable with no change in mass distribution. For each of the 24 wing-tail combinations, observations were made of steady spins for four control settings and of recoveries for five control manipulators. The results are presented in the form of charts comparing the spin characteristics. The results showed that, with a poor tail arrangement, wing plan form and tip shape had a considerable effect on the spinning characteristics.

Seidman, Oscar↗

NASA NTRS1922

Commercial aircraft in war

The difference between aircraft for commercial and wartime uses is delineated, but the interchangability between the two is also discussed. Airships in both roles is also presented.

AIRPLANES - DESIGN↗

NASA NTRS1923

The variation of aerofoil lift and drag coefficients with changes in size and speed

This report contains the results of an investigation into the effect of changes in size and speed upon aerofoil lift and drag coefficients. Certain empirical limitations to the interchangeability of v and l in the general equation of fluid resistance are pointed out and the existing methods of correcting for scale are criticized. New methods of correcting for scale by means of simple formulae are derived and checked by comparison with test results.

Diehl, Walter S↗

NASA NTRS1939

Free-Spinning Wind-Tunnel Tests of a Low-Wing Monoplane with Systematic Changes in Wings and Tails IV : Effect of Center-of-Gravity Location

Eight wings and three tails, covering a wide range of aerodynamic characteristics, were independently ballasted so as to be interchangeable with no change in mass distribution. For each of the 24 resulting wing-tail combinations, observations were made of the steady spin for four control settings and of recoveries for five control manipulations. The results are presented in the form of charts comparing the spin characteristics. The tests are part of a general investigation being made in the NACA free-spinning tunnel to determine the effects of systematic changes in wing and tail arrangement upon the steady-spin and the recovery characteristics of a conventional low-wing monoplane for various load distributions.

Seidman, Oscar↗

NASA NTRS1953

Diffusion of Heat from a Line Source in Isotropic Turbulence

An experimental and analytical study has been made of some features of the turbulent heat diffusion behind a line heated wire stretched perpendicular to a flowing isotropic turbulence. The mean temperature distributions have been measured with systematic variations in wind speed, size of turbulence-producing grid, and downstream location of heat source. The nature of the temperature fluctuation field has been studied. A comparison of Lagrangian and Eulerian analyses for diffusion in a nondecaying turbulence yields an expression for turbulent-heat-transfer coefficient in terms of turbulence velocity and a Lagrangian "scale." the ratio of Eulerian to Lagrangian microscale has been determined theoretically by generalization of a result of Heisenberg and with arbitrary constants taken from independent sources, shows rough agreement with experimental results. A convenient form has been deduced for the criterion of interchangeability of instantaneous space and time derivatives in a flowing turbulence.

Uberoi, Mahinder S↗

NASA NTRS1994

Normalization Of Thermal-Radiation Form-Factor Matrix

Report describes algorithm that adjusts form-factor matrix in TRASYS computer program, which calculates intraspacecraft radiative interchange among various surfaces and environmental heat loading from sources such as sun.

Tsuyuki, Glenn T.↗

NASA NTRS1990

High performance VLSI telemetry data systems

NASA's deployment of major space complexes such as Space Station Freedom (SSF) and the Earth Observing System (EOS) will demand increased functionality and performance from ground based telemetry acquisition systems well above current system capabilities. Adaptation of space telemetry data transport and processing standards such as those specified by the Consultative Committee for Space Data Systems (CCSDS) standards and those required for commercial ground distribution of telemetry data, will drive these functional and performance requirements. In addition, budget limitations will force the requirement for higher modularity, flexibility, and interchangeability at lower cost in new ground telemetry data system elements. At NASA's Goddard Space Flight Center (GSFC), the design and development of generic ground telemetry data system elements, over the last five years, has resulted in significant solutions to these problems. This solution, referred to as the functional components approach includes both hardware and software components ready for end user application. The hardware functional components consist of modern data flow architectures utilizing Application Specific Integrated Circuits (ASIC's) developed specifically to support NASA's telemetry data systems needs and designed to meet a range of data rate requirements up to 300 Mbps. Real-time operating system software components support both embedded local software intelligence, and overall system control, status, processing, and interface requirements. These components, hardware and software, form the superstructure upon which project specific elements are added to complete a telemetry ground data system installation. This paper describes the functional components approach, some specific component examples, and a project example of the evolution from VLSI component, to basic board level functional component, to integrated telemetry data system.

Chesney, J.↗

NASA NTRS1989

Cislunar space infrastructure: Lunar technologies

Continuing its emphasis on the creation of a cisluar infrastructure as an appropriate and cost-effective method of space exploration and development, the University of Colorado explores the technologies necessary for the creation of such an infrastructure, namely (1) automation and robotics; (2) life support systems; (3) fluid management; (4) propulsion; and (5) rotating technologes. The technological focal point is on the development of automated and robotic systems for the implementation of a Lunar Oasis produced by automation and robotics (LOARS). Under direction from the NASA Office of Exploration, automation and robotics have been extensively utilized as an initiating stage in the return to the Moon. A pair of autonomous rovers, modular in design and built from interchangeable and specialized components, is proposed. Utilizing a 'buddy system', these rovers will be able to support each other and to enhance their individual capabilities. One rover primarily explores and maps while the second rover tests the feasibility of various materials-processing techniques. The automated missions emphasize availability and potential uses of lunar resources and the deployment and operations of the LOAR program. An experimental bio-volume is put into place as the precursor to a Lunar Environmentally Controlled Life Support System. The bio-volume will determine the reproduction, growth and production characteristics of various life forms housed on the lunar surface. Physiochemical regenerative technologies and stored resources will be used to buffer biological disturbances of the bio-volume environment. The in situ lunar resources will be both tested and used within this bio-volume. Second phase development on the lunar surface calls for manned operations. Repairs and reconfiguration of the initial framework will ensue. An autonomously initiated, manned Lunar Oasis can become an essential component of the United States space program. The Lunar Oasis will provide support to science, technology, and commerce. It will enable more cost-effective space exploration to the planets and beyond.

W. Faller↗