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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

AX-5 space suit reliability model

The AX-5 is an all metal Extra-vehicular (EVA) space suit currently under consideration for use on Space Station Freedom. A reliability model was developed based on the suit's unique design and on projected joint cycle requirements. Three AX-5 space suit component joints were cycled under simulated load conditions in accordance with NASA's advanced space suit evaluation plan. This paper will describe the reliability model developed, the results of the cycle testing, and an interpretation of the model and test results in terms of projected Mean Time Between Failure for the AX-5. A discussion of the maintenance implications and life cycle for the AX-5 based on this projection is also included.

Reinhardt, AL↗
NASA NTRS1991

Integrated flow and structural modeling for rocket engine component test facility propellant systems

A set of PC-based computational Dynamic Fluid Flow Simulation models is presented for modeling facility gas and cryogenic systems. Data obtained provide important information regarding performance envelope parameters for the facility using different engine components; time-dependent valve setting for controlling steady-state, quasi-steady state, and transient profiles; optimum facility pipe and pipe component sizes and parameters; momentum transfer loads; and fluid conditions at critical points. A set of COSMIC NASTRAN-based finite element models is also presented to evaluate the loads and stresses on test facility piping systems from fluid and gaseous effects, thermal chill down, and occasional wind loads. The models are based on Apple Macintosh software which makes it possible to change numerous parameters.

Dequay, L.↗
NASA NTRS1992

Improved Superconducting Magnetic Rotary Bearings

Improved magnetic rotary bearings designed by exploiting properties of type-II superconducting materials. Depending on design and application, bearing provides fixed or adjustable compensation for lateral vector component of weight or other lateral load on rotor. Allows applied magnetic field to penetrate partially in clusters of field lines, with concomitant establishment of undamped circulating electrical currents within material. Type-II superconductors have critical magnetic fields and critical temperatures greater than type-I superconductors.

Flom, Yury↗
NASA NTRS1992

Atmospheric entry of nuclear-powered vehicles due to accidental/inadvertent termination of operations

The entries of the radioactive components into earth's atmosphere resulting from an accident or inadvertent abort of a space vehicle powered by nuclear-thermal-rockets are investigated. The study is made for a typical piloted Mars mission vehicle incapacitated by an accident or malfunction during the trans-Mars-injection maneuver due to simultaneous multiple failures of its component systems. The three different accident/abort modes considered are the following: (1) a constant-rate angular pitching motion of the vehicle, (2) a constant-acceleration angular pitching motion of the vehicle, and (3) the rocket engine breaks away from the rest of the vehicle with a finite relative (dispersion) velocity. The speeds and angles of the atmospheric entries are calculated for each mode for different values of the time of the accident, pitching rate, acceleration, and dispersion velocity. For the most severe entry speeds and flight-path angles, the stagnation-point pressures, heat transfer rates, thickness, and mass per unit area of the heat shields necessary to protect the radioactive components from disintegrating, deceleration g-loads, and high ground-impact velocities are calculated. The study points out that the high g-loads and high ground-impact velocities are the most serious problems that must be addressed.

Menees, Gene P.↗
NASA NTRS1991

Effects of scale in predicting global structural response

Analytical techniques for scale-up effects were reviewed. The advantages and limitations of applying the principles of similitude to composite structures is summarized and illustrated by simple examples. An analytical procedure was formulated to design scale models of an axially compressed composite cylinder. A building-block approach was outlined where each structural detail is analyzed independently and the probable failure sequence of a selected component is predicted, taking into account load redistribution subsequent to first element failure. Details of this building-block approach are under development.

Deo, R. B.↗
NASA NTRS1956

Calculation of the forces and moments on a slender fuselage and vertical fin penetrating lateral gusts

A theory is presented for calculating the variation with frequency of the lateral-force and yawing-moment coefficients due to sinusoidal side gusts passing over the profile of a simple fuselage-vertical-fin combination. The analysis is based on slender-body theory. The method considers the penetration effect of both fuselage and vertical tail in calculating side force and yawing moment due to side gusts, as opposed to a simple lag concept which considers the flow angle to be uniform over the configuration.

STABILITY, LATERAL AND DIRECTIONAL - DYNAMIC↗
NASA NTRS1994

Spur, helical, and spiral bevel transmission life modeling

A computer program, TLIFE, which estimates the life, dynamic capacity, and reliability of aircraft transmissions, is presented. The program enables comparisons of transmission service life at the design stage for optimization. A variety of transmissions may be analyzed including: spur, helical, and spiral bevel reductions as well as series combinations of these reductions. The basic spur and helical reductions include: single mesh, compound, and parallel path plus revert star and planetary gear trains. A variety of straddle and overhung bearing configurations on the gear shafts are possible as is the use of a ring gear for the output. The spiral bevel reductions include single and dual input drives with arbitrary shaft angles. The program is written in FORTRAN 77 and has been executed both in the personal computer DOS environment and on UNIX workstations. The analysis may be performed in either the SI metric or the English inch system of units. The reliability and life analysis is based on the two-parameter Weibull distribution lives of the component gears and bearings. The program output file describes the overall transmission and each constituent transmission, its components, and their locations, capacities, and loads. Primary output is the dynamic capacity and 90-percent reliability and mean lives of the unit transmissions and the overall system which can be used to estimate service overhaul frequency requirements. Two examples are presented to illustrate the information available for single element and series transmissions.

Savage, Michael↗
NASA NTRS1994

Modeling and life prediction methodology for Titanium Matrix Composites subjected to mission profiles

Titanium matrix composites (TMC) are being evaluated as structural materials for elevated temperature applications in future generation hypersonic vehicles. In such applications, TMC components are subjected to complex thermomechanical loading profiles at various elevated temperatures. Therefore, thermomechanical fatigue (TMF) testing, using a simulated mission profile, is essential for evaluation and development of life prediction methodologies. The objective of the research presented in this paper was to evaluate the TMF response of the (0/90)2s SCS-6/Timetal-21S subjected to a generic hypersonic flight profile and its portions with a temperature ranging from -130 C to 816 C. It was found that the composite modulus, prior to rapid degradation, had consistent values for all the profiles tested. A micromechanics based analysis was used to predict the stress-strain response of the laminate and of the constituents in each ply during thermomechanical loading conditions by using only constituent properties as input. The fiber was modeled as elastic with transverse orthotropic and temperature dependent properties. The matrix was modeled using a thermoviscoplastic constitutive relation. In the analysis, the composite modulus degradation was assumed to result from matrix cracking and was modeled by reducing the matrix modulus. Fatigue lives of the composite subjected to the complex generic hypersonic flight profile were well correlated using the predicted stress in 0 degree fibers.

Mirdamadi, M.↗
NASA NTRS1994

Measurements of the Low Frequency Gain Fluctuations of a 30 GHz High-Electron-Mobility-Transistor Cryogenic Amplifier

Low frequency gain fluctuations of a 30 GHz cryogenic HEMT amplifier have been measured with the input of the amplifier connected to a 15 K load. Effects of fluctuations of other components of the test set-up were eliminated by use of a power-power correlation technique. Strong correlation between output power fluctuations of the amplifier and drain current fluctuations of the transistors comprising the amplifier are observed. The existence of these correlations introduces the possibility of regressing some of the excess noise from the HEMT amplifier's output using the measured drain currents.

Jarosik, Norman↗
NASA NTRS1997

Parameter Estimation for Viscoplastic Material Modeling

A key ingredient in the design of engineering components and structures under general thermomechanical loading is the use of mathematical constitutive models (e.g. in finite element analysis) capable of accurate representation of short and long term stress/deformation responses. In addition to the ever-increasing complexity of recent viscoplastic models of this type, they often also require a large number of material constants to describe a host of (anticipated) physical phenomena and complicated deformation mechanisms. In turn, the experimental characterization of these material parameters constitutes the major factor in the successful and effective utilization of any given constitutive model; i.e., the problem of constitutive parameter estimation from experimental measurements.

Saleeb, Atef F.↗
NASA NTRS2000

X-33 LH2 Tank Failure Investigation Findings

This presentation focuses on the tank history, test objectives, failure description, investigation and conclusions. The test objectives include verify structural integrity at 105% expected flight load limit varying the following parameters: cryogenic temperature; internal pressure; and mechanical loading. The Failure description includes structural component of the aft body, quad-lobe design, and sandwich - honeycomb graphite epoxy construction.

Niedermeyer, Mindy↗
NASA NTRS2004

Performance and Flowfield Measurements on a 10-inch Ducted Rotor VTOL UAV

A ducted fan VTOL UAV with a 10-inch diameter rotor was tested in the US Army 7-by 10-Foot Wind Tunnel. The test conditions covered a range of angle of attack from 0 to 110 degrees to the freestream. The tunnel velocity was varied from 0 (simulating a hover condition) to 128 ft/sec in propeller mode. A six-component internal balance measured the aerodynamic loads for a range of model configurations. including the isolated rotor, the isolated duct, and the full configuration of the duct and rotor. For some conditions, hotwire velocity surveys were conducted along the inner and outer surface of the duct and across the downstream wake. In addition, fluorescent oil flow visualization allowed the flow separation patterns inside and outside of the duct to be mapped for a few test conditions. Two different duct shapes were tested to determine the performance effects of leading edge radius. For each duct, a range of rotor tip gap from 1%R to 4.5%R was tested to determine the performance penalty in hover and axial flight. Measured results are presented in terms of hover performance, hover performance in a crosswind, and high angle of attack performance in propeller mode. In each case, the effects of both tip gap and duct leading edge radius are illustrated using measurements. Some of the hover performance issues were also studied using a simple analytical method, and the results agreed with the measurements.

Martin, Preston↗
NASA NTRS2004

New Dynamic Spin Rig Capabilities Used to Determine Rotating Blade Dynamics

The Dynamic Spin Rig Facility at the NASA Glenn Research Center is used to determine the structural response of rotating engine components without the effects of aerodynamic loading. Recently, this rig's capabilities were enhanced through the replacement of grease-lubricated ball bearings with magnetic bearings. Magnetic bearings offer a number of advantages--the most important here being that they not only fully support the rotor system, but excite it as well. Three magnetic bearings support the rotor and provide five axes of controlled motion: an x- and y-axis translation at each of two radial bearings and a z-axis translation in the vertical or axial direction. Sinusoidal excitation (most commonly used) can be imparted on the rotor through the radial magnetic bearings in either a fixed or rotating frame of reference. This excitation is added directly to the magnetic bearing control output. Since the rotor is fully levitated, large translations and rotations of the rotor system can be achieved. Some of the capabilities of this excitation system were determined and reported. The accelerations obtained at the tip of a titanium flat plate test article versus the swept sine excitation sent to both radial bearings in phase and perpendicular to the plane containing the two blades are shown. Recent tests required the excitation of fundamental bending and torsional blade resonances at rotor speeds up to 10,000 rpm. Successful fixed synchronous rotation of the excitation signal provided the best detectable blade resonant vibrations at excitation frequencies up to 1100 Hz for the particular blades of interest. A noncontacting laser measurement system was used to collect blade-tip motions. From these data, the amplitude and frequency of the motion could be determined as well as the blade damping properties. Damping could be determined using two methods: (1) free decay and (2) curve fitting the vibration amplitude as a function of frequency in and around the resonance of interest and using the half-power method. The free decay of a composite blade vibrating at its first bending resonance while rotating at 3000 rp is shown. This new system is currently being used to support the Efficient Low-Noise Fan project at Glenn. The damping properties of prototype hollow composite blades specially designed to reduce fan noise are currently being determined.

Provenza, Andrew J.↗
NASA NTRS1995

An Overview of ANN Application in the Power Industry

The paper presents a survey on the development and experience with artificial neural net (ANN) applications for electric power systems, with emphasis on operational systems. The organization and constraints of electric utilities are reviewed, motivations for investigating ANN are identified, and a current assessment is given from the experience of 2400 projects using ANN for load forecasting, alarm processing, fault detection, component fault diagnosis, static and dynamic security analysis, system planning, and operation planning.

artificial neural networks ANN electric power syst↗
NASA NTRS2004

A comparative analysis of loop heat pipe based thermal architectures for spacecraft thermal control

Loop Heat Pipes (LHP) have gained acceptance as a viable means of heat transport in many spacecraft in recent years. However, applications using LHP technology tend to only remove waste heat from a single component to an external radiator. Removing heat from multiple components has been done by using multiple LHPs. This paper discusses the development and implementation of a Loop Heat Pipe based thermal architecture for spacecraft. In this architecture, a Loop Heat Pipe with multiple evaporators and condensers is described in which heat load sharing and thermal control of multiple components can be achieved. A key element in using a LHP thermal architecture is defining the need for such an architecture early in the spacecraft design process. This paper describes an example in which a LHP based thermal architecture can be used and how such a system can have advantages in weight, cost and reliability over other kinds of distributed thermal control systems. The example used in this paper focuses on a Mars Rover Thermal Architecture. However, the principles described here are applicable to Earth orbiting spacecraft as well.

loop heat pipes↗
NASA NTRS2007

Driver Code for Adaptive Optics

A special-purpose computer code for a deformable-mirror adaptive-optics control system transmits pixel-registered control from (1) a personal computer running software that generates the control data to (2) a circuit board with 128 digital-to-analog converters (DACs) that generate voltages to drive the deformable-mirror actuators. This program reads control-voltage codes from a text file, then sends them, via the computer s parallel port, to a circuit board with four AD5535 (or equivalent) chips. Whereas a similar prior computer program was capable of transmitting data to only one chip at a time, this program can send data to four chips simultaneously. This program is in the form of C-language code that can be compiled and linked into an adaptive-optics software system. The program as supplied includes source code for integration into the adaptive-optics software, documentation, and a component that provides a demonstration of loading DAC codes from a text file. On a standard Windows desktop computer, the software can update 128 channels in 10 ms. On Real-Time Linux with a digital I/O card, the software can update 1024 channels (8 boards in parallel) every 8 ms.

Rao, Shanti↗
NASA NTRS2010

Integration Methodology For Oil-Free Shaft Support Systems: Four Steps to Success

Commercial applications for Oil-Free turbomachinery are slowly becoming a reality. Micro-turbine generators, highspeed electric motors, and electrically driven centrifugal blowers are a few examples of products available in today's commercial marketplace. Gas foil bearing technology makes most of these applications possible. A significant volume of component level research has led to recent acceptance of gas foil bearings in several specialized applications, including those mentioned above. Component tests identifying such characteristics as load carrying capacity, power loss, thermal behavior, rotordynamic coefficients, etc. all help the engineer design foil bearing machines, but the development process can be just as important. As the technology gains momentum and acceptance in a wider array of machinery, the complexity and variety of applications will grow beyond the current class of machines. Following a robust integration methodology will help improve the probability of successful development of future Oil-Free turbomachinery. This paper describes a previously successful four-step integration methodology used in the development of several Oil-Free turbomachines. Proper application of the methods put forward here enable successful design of Oil-Free turbomachinery. In addition when significant design changes or unique machinery are developed, this four-step process must be considered.

Howard, Samuel A.↗