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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 127 records · Page 7

All sources NASA NTRS DOE OSTI

NASA NTRS1989

A fuel cell energy storage system concept for the Space Station Freedom Extravehicular Mobility Unit

An update is given on work to design and build a Fuel Cell Energy Storage System (FCESS) bench-tested unit for the Space Station Freedom Extravehicular Mobility Unit (EMU). Fueled by oxygen and hydride-stored hydrogen, the FCESS is being considered as an alternative to the EMU zinc-silver oxide battery. Superior cycle life and quick recharge are the main attributes of FCESS. The design and performance of a nonventing, 28 V, 34 Ahr system with 7 amp rating are discussed.

Adlhart, Otto J.↗

NASA NTRS1991

The PM-200 lubrication system

Plasma sprayed composite coating of metal-bonded chromium carbide with additions of silver and thermochemically stable fluorides were previously reported to be lubricative in pin on desk bench tests from room temperature to 900 C. An early coating formulation of this type, designated as PS-200, was successfully tested as a cylinder coating in a Stirling engine at a TRRT of 760 C in a hydrogen atmosphere, and as a backup lubricant for gas bearings to 650 C. A subsequent optimization program has shown that tribological properties are further improved by increasing the solid lubricant content. The improved coating is designated as PS-212. The same powder formulation was used to make free-standing powder metallurgy (PM-212) parts by sintering or hot isostatic pressing. The process is very attractive for making parts that cannot be readily plasma sprayed such as bushings and cylinders that have small bore diameters and/or high length to diameter ratios. The properties of coatings and free-standing parts fabricated from these powders are reviewed.

Sliney, Harold E.↗

NASA NTRS1989

Diffraction of impulsive sounds by a curved obstruction - A time-domain study

The diffraction of spark-discharge-produced sound waves produced by a half circular cylinder covered with absorbing material is investigated theoretically and experimentally. The test bench setup and the measurement instrumentation and procedure are described; the derivation of an analytical model on the basis of the matched asymptotic expansion theory of Pierce (1981) is outlined; and the results are compared in graphs. Good general agreement is obtained, except in the deep shadow of the obstacle, where the theory underpredicts the magnitude of the received pulse. This discrepancy is tentatively attributed to the creeping-wave mechanism described by Pierce.

Berthelot, Yves H.↗

NASA NTRS1992

Development of a machine vision guidance system for automated assembly of space structures

The topics are presented in viewgraph form and include: automated structural assembly robot vision; machine vision requirements; vision targets and hardware; reflective efficiency; target identification; pose estimation algorithms; triangle constraints; truss node with joint receptacle targets; end-effector mounted camera and light assembly; vision system results from optical bench tests; and future work.

Eric G Cooper↗

NASA NTRS1992

Steady and transient performance calculation method for prediction, analysis, and identification

The detailed design and development of turbofans Involves the prediction and identification, by means of test analysis, of the performance of the engine and its components. The thermodynamic simulation and analysis codes integrate existing knowledge and Interpretations of the detailed operating procedure of the components of the engine being developed. The relevance of the predicted performance depends on the quality of the representation of the various physical phenomena affecting the characteristics of the components and, consequently, on the incorporation of experimental correlation in the modelling. In this context, the representation of compressor and turbine characteristics is particularly important. Firstly, we will analyze the ability of corrected parameters to represent MACH similitude at the component inlet under various conditions. The various measurements achieved on the engine during development are used to enhance the modelling. The methods of identifying the thermodynamic calculation code with the various measurements, considered here with their uncertainties, are then presented and described. The analysis of the tests performed on the powerplant, designed to Identify the real characteristics of the engine components, can be undertaken, considering one or more engine test points and incorporating knowledge acquired through experimentation or on the component test bench. There are many possible fields of use for these identification methods ranging from the rematching of components to the optimization of the control system.

Jean Pierre Duponchel↗

NASA NTRS1992

Control of unsteady separated flow associated with the dynamic stall of airfoils

The two principal objectives of this research were to achieve an improved understanding of the mechanisms involved in the onset and development of dynamic stall under compressible flow conditions, and to investigate the feasibility of employing adaptive airfoil geometry as an active flow control device in the dynamic stall engine. Presented here are the results of a quantitative (PDI) study of the compressibility effects on dynamic stall over the transiently pitching airfoil, as well as a discussion of a preliminary technique developed to measure the deformation produced by the adaptive geometry control device, and bench test results obtained using an airfoil equipped with the device.

Wilder, Michael C.↗

NASA NTRS1921

The Dynamometer Hub for the Testing Propellers and Engines During Flight

The need for a device to measure flight resistance, engine and propeller power, and efficiency during flight grew in proportion to the demand for increased flying capacity in military types of aircraft. Here, a dynamometer hub was inserted between the engine and the propeller. Taken as a whole, the tests that were conducted show that though the dynamometer is a sensitive instrument liable to numerous derangements, it is undeniably useful even in its present form, when handled with care and skill. Facilitating, as it does, the possibility of maintaining the fixed position of the engine, the blocking out of the weight effect when the plane is in the sloping position, and the possibility of taking direct measurements of force at the point of transmission, the dynamometer appears to be by far the best solution of the problem of a flying test bench, utilized as a hydraulic balance with the smallest possible measuring stroke and the least tendency to oscillation.

Enoch, O↗

NASA NTRS1993

Performance assessment of low pressure nuclear thermal propulsion

A low pressure nuclear thermal propulsion (LPNTP) system, which takes advantage of hydrogen dissociation/recombination, was proposed as a means of increasing engine specific impulse (Isp). The effect of hydrogen dissociation/recombination on LPNTP Isp is examined. A two-dimensional computer model was used to show that the optimum chamber pressure is approximately 100 psia (at a chamber temperature of 3,000 K), with an Isp approximately 15 s higher than at 1,000 psia. At high chamber temperatures and low chamber pressures, the increase in Isp is due to both lower average molecular weights caused by dissociation and added kinetic energy from monatomic hydrogen recombination. Monatomic hydrogen recombination increases the Isp more then hydrogen dissociation. Variations in the mole fraction of monatomic hydrogen are similar to variations in static pressure along the axial nozzle position. Most recombination occurs close to the nozzle throat. Practical variations in nozzle geometry have minimal impact on recombination. Other models which can simulate a wider range of nozzle designs should be used in the future. The uncertainty of the hydrogen kinetic reaction rates at high temperatures (approximately 3,000 K) affects the accuracy of the analysis and should be verified with simple bench tests.

Gerrish, H. P., Jr.↗

NASA NTRS1994

Seals Flow Code Development 1993

Seals Workshop of 1993 code releases include SPIRALI for spiral grooved cylindrical and face seal configurations; IFACE for face seals with pockets, steps, tapers, turbulence, and cavitation; GFACE for gas face seals with 'lift pad' configurations; and SCISEAL, a CFD code for research and design of seals of cylindrical configuration. GUI (graphical user interface) and code usage was discussed with hands on usage of the codes, discussions, comparisons, and industry feedback. Other highlights for the Seals Workshop-93 include environmental and customer driven seal requirements; 'what's coming'; and brush seal developments including flow visualization, numerical analysis, bench testing, T-700 engine testing, tribological pairing and ceramic configurations, and cryogenic and hot gas facility brush seal results. Also discussed are seals for hypersonic engines and dynamic results for spiral groove and smooth annular seals.

Liang, Anita D.↗

NASA NTRS1994

Pressure measurements of a three wave journal air bearing

In order to validate theoretical predictions of a wave journal bearing concept, a bench test rig was assembled at NASA Lewis Research Center to measure the steady-state performance of a journal air bearing. The tester can run up to 30,000 RPM and the spindle has a run out of less than 1 micron. A three wave journal bearing (50 mm diameter and 58 mm length) has been machined at NASA Lewis. The pressures at 16 ports along the bearing circumference at the middle of the bearing length were measured and compared to the theoretical prediction. The bearing ran at speeds up to 15,000 RPM and certain loads. Good agreement was found between the measured and calculated pressures.

Dimofte, Florin↗

NASA NTRS1994

Control of unsteady separated flow associated with the dynamic stall of airfoils

A unique active flow-control device is proposed for the control of unsteady separated flow associated with the dynamic stall of airfoils. The device is an adaptive-geometry leading-edge which will allow controlled, dynamic modification of the leading-edge profile of an airfoil while the airfoil is executing an angle-of-attack pitch-up maneuver. A carbon-fiber composite skin has been bench tested, and a wind tunnel model is under construction. A baseline parameter study of compressible dynamic stall was performed for flow over an NACA 0012 airfoil. Parameters included Mach number, pitch rate, pitch history, and boundary layer tripping. Dynamic stall data were recorded via point-diffraction interferometry and the interferograms were analyzed with in-house developed image processing software. A new high-speed phase-locked photographic image recording system was developed for real-time documentation of dynamic stall.

Wilder, M. C.↗

NASA NTRS1995

System results from FRECOPA

The work carried out over the past three years on FRECOPA and the LDEF has enabled a large quantity of information to be collected, part of which has already been exploited. As far as CNES is concerned, the major spin-offs of this mission mainly focus on the orbital environment and the behavior of materials in such an environment. With respect to the environment, the authors shall develop the lessons learned from expert appraisals on impacts by microparticles, which are the main feature observed in this area. As for the materials, the results show a variety of behavior when subjected to the space environment and even now constitute a wealth of information for the designing and validation of future mechanical systems. Apart from these direct spin-offs, there are repercussions on in-flight and ground testing, the calibration of test benches and improvements to simulation models.

Durin, Christian↗

NASA NTRS1996

Smart Material Demonstrators Based on Shape Memory Alloys and Electroceramics

This paper describes the development and characterization of two technology demonstrators that were produced under the auspices of an ARPA sponsored smart materials synthesis and processing effort. The ARPA Smart Materials and Synthesis (SMS) Program was a 2 year, $10M partnership led by Martin Marietta Laboratories - Baltimore and included Lockheed Missiles & Space Co., NRL, AVX Corp., Martin Marietta Astronautics Groups, BDM Federal, Inc., Virginia Tech, Clemson, University of Maryland, Denver University, and The Johns Hopkins University. In order to demonstrate the usefulness of magnetron sputtered shape memory foil and the manufacturability of reliable, reproducible electrostrictive actuators, the team designed a broadband active vibration cancellation device for suppressing the vibration load on delicate instruments and precision pointing devices mounted on orbiting satellites and spacecraft. The results of extensive device characterization and bench testing are discussed. Initial simulation results show excellent control authority and amplitude attenuation over the range of anticipated disturbance frequencies. The SMS Team has also developed an active 1-3 composite comprising micro-electrostrictive actuators embedded in a polymeric matrix suitable for underwater applications such as sonar quieting and listening arrays, and for medical imaging. Follow-on programs employing these technologies are also described.

Cooke, Arther V.↗

NASA NTRS1997

Damping Experiment of Spinning Composite Plates with Embedded Viscoelastic Material

One way to increase gas turbine engine blade reliability and durability is to reduce blade vibration. It is well known that vibration reduction can be achieved by adding damping to metal and composite blade-disk systems. This experiment was done to investigate the use of integral viscoelastic damping treatments to reduce vibration of rotating composite fan blades. It is part of a joint research effort with NASA LeRC and the University of California, San Diego (UCSD). Previous vibration bench test results obtained at UCSD show that plates with embedded viscoelastic material had over ten times greater damping than similar untreated plates; and this was without a noticeable change in blade stiffness. The objectives of this experiment, were to verify the structural integrity of composite plates with viscoelastic material embedded between composite layers while under large steady forces from spinning, and to measure the damping and natural frequency variation with rotational speed.

Mehmed, Oral↗

NASA NTRS2001

A Thin Film Multifunction Sensor for Harsh Environments

The status of work at NASA Glenn Research Center to develop a minimally intrusive integrated sensor to provide realtime measurement of strain, heat flux and flow in high temperature environments is presented in this paper. The sensor can be beneficial as a single package to characterize multiple stress and strain modes simultaneously on materials and components during engine development and validation. A major technical challenge is to take existing individual gauge designs and modify them into one integrated thin film sensor. Ultimately, the goal is to develop the ability to deposit the sensors directly onto internal engine parts or on a small thin substrate that can be attached to engine components. Several prototype sensors constructed of platinum, platinum-rhodium alloy, and alumina on constant-strain alumina beams have been built and bench-tested. The technical challenges of the design. construction, and testing are discussed. Data from the preliminary testing of the sensor array is presented. The future direction for the sensor development is discussed as well.

Wrbanek, John D.↗

NASA NTRS1960

Satellite Attitude Control Using a Combination of Inertia Wheels and a Bar Magnet

The use of inertia wheels to control the attitude of a satellite has currently aroused much interest. The stability of such a system has been studied in this investigation. A single-degree-of-freedom analysis indicates that a response with suitable dynamic characteristics and precise control can be achieved by commanding the angular velocity of the inertia wheel with an error signal that is the sum of the attitude error, the attitude rate, and the integral of the attitude error. A digital computer was used to study the three-degree-of-freedom response to step displacements, and the results indicate that the cross-coupling effects of inertia coupling and precession coupling had no effect on system stability. A study was also made of the use of a bar magnet to supplement the inertia wheels by providing a means of removing any momentum introduced into the system by disturbances such as aerodynamic torques. A study of a case with large aerodynamic torques, with a typical orbit, indicated that the magnet was a suitable device for supplying the essential trimming force. Single-degree-of-freedom bench tests generally verified the dynamic response predicted by the analytical study. the test table to within plus or minus 9 arc-seconds of the reference direction, even though the hardware components that were used in these tests were not specifically designed for the control system.

Adams, James J.↗

NASA NTRS2005

A Prototype Actuator Concept for Membrane Boundary Vibration Control

In conjunction with the research in ultra-lightweight deployable spacecraft and membrane structures is an underlying need for shape and vibration control. For thin film membrane structures, fundamental modes of vibration for the membrane can be excited through station keeping, attitude adjustments, orbital maneuvers, or contact with space junk or micrometeorites. In order to maintain structural integrity as well as surface shape contour, which may be essential for inflatable antennas, reflective surfaces, or solar sails; vibration damping is a necessary component. This paper discusses development of an actuator attached at the membrane boundary, containing two types of piezoelectric elements, which can be used to perform active control of vibration from the boundary of a membrane. The actuator is designed to control the membrane out-of-plane displacement and in-plane tension by varying the boundary conditions. Results from an initial experimental evaluation of the concept are presented with bench tests of the actuator alone, and with the actuator connected to a large membrane.

Solter, Micah J.↗

NASA NTRS2001

Accurate Time-Dependent Traveling-Wave Tube Model Developed for Computational Bit-Error-Rate Testing

The phenomenal growth of the satellite communications industry has created a large demand for traveling-wave tubes (TWT's) operating with unprecedented specifications requiring the design and production of many novel devices in record time. To achieve this, the TWT industry heavily relies on computational modeling. However, the TWT industry's computational modeling capabilities need to be improved because there are often discrepancies between measured TWT data and that predicted by conventional two-dimensional helical TWT interaction codes. This limits the analysis and design of novel devices or TWT's with parameters differing from what is conventionally manufactured. In addition, the inaccuracy of current computational tools limits achievable TWT performance because optimized designs require highly accurate models. To address these concerns, a fully three-dimensional, time-dependent, helical TWT interaction model was developed using the electromagnetic particle-in-cell code MAFIA (Solution of MAxwell's equations by the Finite-Integration-Algorithm). The model includes a short section of helical slow-wave circuit with excitation fed by radiofrequency input/output couplers, and an electron beam contained by periodic permanent magnet focusing. A cutaway view of several turns of the three-dimensional helical slow-wave circuit with input/output couplers is shown. This has been shown to be more accurate than conventionally used two-dimensional models. The growth of the communications industry has also imposed a demand for increased data rates for the transmission of large volumes of data. To achieve increased data rates, complex modulation and multiple access techniques are employed requiring minimum distortion of the signal as it is passed through the TWT. Thus, intersymbol interference (ISI) becomes a major consideration, as well as suspected causes such as reflections within the TWT. To experimentally investigate effects of the physical TWT on ISI would be prohibitively expensive, as it would require manufacturing numerous amplifiers, in addition to acquiring the required digital hardware. As an alternative, the time-domain TWT interaction model developed here provides the capability to establish a computational test bench where ISI or bit error rate can be simulated as a function of TWT operating parameters and component geometries. Intermodulation products, harmonic generation, and backward waves can also be monitored with the model for similar correlations. The advancements in computational capabilities and corresponding potential improvements in TWT performance may prove to be the enabling technologies for realizing unprecedented data rates for near real time transmission of the increasingly larger volumes of data demanded by planned commercial and Government satellite communications applications. This work is in support of the Cross Enterprise Technology Development Program in Headquarters' Advanced Technology & Mission Studies Division and the Air Force Office of Scientific Research Small Business Technology Transfer programs.

Kory, Carol L.↗