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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Vacuum Plasma Spray (VPS) Forming of Solar Thermal Propulsion Components Using Refractory Metals

The Thermal Spray Laboratory at NASA's Marshall Space Flight Center has developed and demonstrated a fabrication technique using Vacuum Plasma Spray (VPS) to form structural components from a tungsten/rhenium alloy. The components were assembled into an absorber cavity for a fully-functioning, ground test unit of a solar then-nal propulsion engine. The VPS process deposits refractory metal onto a graphite mandrel of the desired shape. The mandrel acts as a male mold, forming the required contour and dimensions of the inside surface of the deposit. Tungsten and tungsten/25% rhenium were used in the development and production of several absorber cavity components. These materials were selected for their high temperature (greater than 25000 C [greater than 4530 F]) strength. Each absorber cavity comprises 3 coaxial shells with two, double-helical flow passages through which the propellant gas flows. This paper describes the processing techniques, design considerations, and process development associated with forming these engine components.

Zimmerman, Frank R.↗
NASA NTRS1980

Rotary balance data for a single-engine agricultural airplane configuration for an angle-of-attack range of 8 deg to 90 deg

Aerodynamic characteristics obtained in a helical flow environment utilizing a rotary balance located in the Langley spin tunnel are presented in plotted form for a 1/10 scale single engine agricultural airplane model. The configurations tested include the basic airplane, various wing leading edge and wing tip devices, elevator, aileron, and rudder control settings, and other modifications. Data are presented without analysis for an angle of attack range of 8 deg to 90 deg, and clockwise and counter-clockwise rotations covering a spin coefficient range from 0 to .9.

Mulcay, W. J.↗
NASA NTRS1980

Engine identification for adaptive control

An attempt to obtain a dynamic model for a turbofan gas turbine engine for the purpose of adaptive control is described. The requirements for adaptive control indicate that a dynamic model should be identified from data sampled during engine operation. The dynamic model identified was of the form of linear differential equations with time varying coefficients. A turbine engine is, however, a highly nonlinear system, so the identified model would be valid only over a small area near the operating point, thus requiring frequent updating of the coefficients in the model. Therefore it is necessary that the identifier use only recent information to perform its function. The identifier selected minimized the square of the equation errors. Known linear systems were used to test the characteristics of the identifier. It was found that the performance was dependent on the number of data points used in the computations and upon the time interval over which the data points were obtained. Preliminary results using an engine deck for the quiet, clean, shorthaul experimental engine indicate that the identified model predicts the engine motion well when there is sufficient dynamic information, that is when the engine is in transient operation.

Leonard, R. G.↗
NASA NTRS1996

Crystals of Serum Albumin for Use in Genetic Engineering and Rational Drug Design

Serum albumin crystal forms have been produced which exhibit superior x-ray diffraction quality. The crystals are produced from both recombinant and wild-type human serum albumin, canine, and baboon serum albumin and allow the performance of drug-binding studies as well as genetic engineering studies. The crystals are grown from solutions of polyethylene glycol or ammonium sulphate within prescribed limits during growth times from one to several weeks and include the following space groups: P2(sub 1), C2, P1.

Carter, Daniel C.↗
NASA NTRS2000

The Faster, Better, Cheaper Approach to Space Missions: An Engineering Management Assessment

This paper describes, in viewgraph form, the faster, better, cheaper approach to space missions. The topics include: 1) What drives "Faster, Better, Cheaper"? 2) Why Space Programs are Costly; 3) Background; 4) Aerospace Project Management (Old Culture); 5) Aerospace Project Management (New Culture); 6) Scope of Analysis Limited to Engineering Management Culture; 7) Qualitative Analysis; 8) Some Basic Principles of the New Culture; 9) Cause and Effect; 10) "New Ways of Doing Business" Survey Results; 11) Quantitative Analysis; 12) Recent Space System Cost Trends; 13) Spacecraft Dry Weight Trend; 14) Complexity Factor Trends; 15) Cost Normalization; 16) Cost Normalization Algorithm; 17) Unnormalized Cost vs. Normalized Cost; and 18) Concluding Observations.

Hamaker, Joe↗
NASA NTRS1985

Fabrication of ceramic substrate-reinforced and free forms

Components fabricated of, or coated with, ceramics have lower parasitic cooling requirements. Techniques are discussed for fabricating thin-shell ceramic components and ceramic coatings for applications in rocket or jet engine environments. Thin ceramic shells with complex geometric forms involving convolutions and reentrant surfaces were fabricated by mandrel removal. Mandrel removal was combined with electroplating or plasma spraying and isostatic pressing to form a metal support for the ceramic. Rocket engine thrust chambers coated with 0.08 mm (3 mil) of ZrO2-8Y2O3 had no failures and a tenfold increase in engine life. Some measured mechanical properties of the plasma-sprayed ceramic are presented.

Quentmeyer, R. J.↗
NASA NTRS1972

Fan noise and performance

Tradeoffs between aerodynamic and acoustic properties of various fan configurations led to the selection of a variety of fans that produce noise levels in the range of 100 to 120 PNdb. Fan configuration and design pressure ratio required for specific mission operations depend in part on the type of mission to be performed. Noise data obtained for single-stage low speed fans, single-stage high speed fans, and two-stage fan engines are presented in table form.

Kramer, J. J.↗
NASA NTRS1977

Effects of control inputs on the estimation of stability and control parameters of a light airplane

The maximum likelihood parameter estimation technique was used to determine the values of stability and control derivatives from flight test data for a low-wing, single-engine, light airplane. Several input forms were used during the tests to investigate the consistency of parameter estimates as it relates to inputs. These consistencies were compared by using the ensemble variance and estimated Cramer-Rao lower bound. In addition, the relationship between inputs and parameter correlations was investigated. Results from the stabilator inputs are inconclusive but the sequence of rudder input followed by aileron input or aileron followed by rudder gave more consistent estimates than did rudder or ailerons individually. Also, square-wave inputs appeared to provide slightly improved consistency in the parameter estimates when compared to sine-wave inputs.

Cannaday, R. L.↗
NASA NTRS1983

F100 Multivariable Control Synthesis Program. Computer Implementation of the F100 Multivariable Control Algorithm

As turbofan engines become more complex, the development of controls necessitate the use of multivariable control techniques. A control developed for the F100-PW-100(3) turbofan engine by using linear quadratic regulator theory and other modern multivariable control synthesis techniques is described. The assembly language implementation of this control on an SEL 810B minicomputer is described. This implementation was then evaluated by using a real-time hybrid simulation of the engine. The control software was modified to run with a real engine. These modifications, in the form of sensor and actuator failure checks and control executive sequencing, are discussed. Finally recommendations for control software implementations are presented.

Soeder, J. F.↗
NASA NTRS1984

Measurement of local connective heat transfer coefficients of four ice accretion shapes

In the analytical study of ice accretions that form on aerodynamic surfaces (airfoils, engine inlets, etc.) it is often necessary to be able to calculate convective heat transfer rates. In order to do this, local convective heat transfer coefficients for the ice accretion shapes must be known. In the past, coefficients obtained for circular cylinders were used as an approximation to the actual coefficients since no better information existed. The purpose of this experimental study was to provide local convective heat transfer coefficients for four shapes that represent ice accretions. The shapes were tested with smooth and rough surfaces. The experimental method chosen was the thin-skin heat rate technique. Using this method local Nusselt numbers were determined for the ice shapes. In general it was found that the convective heat transfer was higher in regions where the model's surfaces were convex and lower in regions where the model's surfaces were concave. The effect of roughness was to increase the heat transfer in the high heat transfer regions by approximately 100% while little change was apparent in the low heat transfer regions.

Smith, M. E.↗
NASA NTRS1988

Improved silicon carbide for advanced heat engines

This is the third annual technical report for the program entitled, Improved Silicon Carbide for Advanced Heat Engines, for the period February 16, 1987 to February 15, 1988. The objective of the original program was the development of high strength, high reliability silicon carbide parts with complex shapes suitable for use in advanced heat engines. Injection molding is the forming method selected for the program because it is capable of forming complex parts adaptable for mass production on an economically sound basis. The goals of the revised program are to reach a Weibull characteristic strength of 550 MPa (80 ksi) and a Weibull modulus of 16 for bars tested in 4-point loading. Two tasks are discussed: Task 1 which involves materials and process improvements, and Task 2 which is a MOR bar matrix to improve strength and reliability. Many statistically designed experiments were completed under task 1 which improved the composition of the batches, the mixing of the powders, the sinter and anneal cycles. The best results were obtained by an attritor mixing process which yielded strengths in excess of 550 MPa (80 ksi) and an individual Weibull modulus of 16.8 for a 9-sample group. Strengths measured at 1200 and 1400 C were equal to the room temperature strength. Annealing of machined test bars significantly improved the strength. Molding yields were measured and flaw distributions were observed to follow a Poisson process. The second iteration of the Task 2 matrix experiment is described.

Whalen, Thomas J.↗
NASA NTRS1990

Fine-tuning of process conditions to improve product uniformity of polystyrene particles used for wind tunnel velocimetry

Monodisperse polymer particles (having uniform diameter) were used for the last two decades in physical, biological, and chemical sciences. In NASA Langley Research Center monodisperse polystyrene particles are used in wind tunnel laser velocimeters. These polystyrene (PS) particles in latex form were formulated at the Engineering Laboratory of FENGD using emulsion-free emulsion polymerization. Monodisperse PS latices particles having different particle diameters were formulated and useful experimental data involving effects of process conditions on particle size were accumulated. However, similar process conditions and chemical recipes for polymerization of styrene monomer have often yielded monodisperse particles having varying diameters. The purpose was to improve the PS latex product uniformity by fine-tuning the process parameters based on the knowledge of suspension and emulsion polymerization.

Ray, Asit K.↗
NASA NTRS1992

The MPD thruster program at JPL

The topics covered are presented in viewgraph form and include the following: engine lifetime assessment; lithium magnetoplasmadynamic (MPD) thruster development; and radiation-cooled, applied-field engine testing.

Goodfellow, Keith↗
NASA NTRS1931

The N.A.C.A. Apparatus for Studying the Formation and Combustion of Fuel Sprays and the Results from Preliminary Tests

Described here is an apparatus for studying the formation and combustion of fuel sprays under conditions closely simulating those in a high speed compression-ignition engine. The apparatus consists of a single-cylinder modified test engine, a fuel injection system so designed that a single charge of fuel can be injected into the combustion chamber, an electric driving motor, and a high-speed photographic apparatus. The cylinder head of the engine has a vertical disk form of combustion chamber whose sides are glass windows. When the fuel is injected into the combustion chamber, motion pictures at the rate of 2000 per second are taken of the spray formation by means of spark discharges. When combustion takes place, the light of combustion is recorded on the same photographic film as the spray photographs. Included here are the results of some tests to determine the effect of air temperature, air flow, and nozzle design on the spray formation. The results show that the compression temperature has little effect on the penetration of the fuel spray, but does not affect the dispersion, that air velocities of about 300 feet per second are necessary to destroy the core of the spray, and that the effect of air flow on the spray is controlled to a certain extent by the design of the injection nozzle. The results on the combustion of the spray show that when ignition does not take place until after spray cut-off, the ignition may start almost simultaneously throughout the combustion chamber or at different points throughout the chamber. When ignition takes place before spray cut-off, the combustion starts around the edge of the spray and then spreads throughout the chamber.

Rothrock, A M↗
NASA NTRS1993

NASA/DOD Aerospace Knowledge Diffusion Research Project. Report 15: Technical uncertainty and project complexity as correlates of information use by US industry-affiliated aerospace engineers and scientists: Results of an exploratory investigation

An exploratory study was conducted that investigated the influence of technical uncertainty and project complexity on information use by U.S. industry-affiliated aerospace engineers and scientists. The study utilized survey research in the form of a self-administered mail questionnaire. U.S. aerospace engineers and scientists on the Society of Automotive Engineers (SAE) mailing list served as the study population. The adjusted response rate was 67 percent. The survey instrument is appendix C to this report. Statistically significant relationships were found to exist between technical uncertainty, project complexity, and information use. Statistically significant relationships were found to exist between technical uncertainty, project complexity, and the use of federally funded aerospace R&D. The results of this investigation are relevant to researchers investigating information-seeking behavior of aerospace engineers. They are also relevant to R&D managers and policy planners concerned with transferring the results of federally funded aerospace R&D to the U.S. aerospace industry.

Pinelli, Thomas E.↗
NASA NTRS1997

A New 1000 F Magnetic Bearing Test Rig

NASA and the Army are currently exploring the possibility of using magnetic bearings in gas turbine engines. The use of magnetic bearings in gas turbine engines could increase the reliability by eliminating the lubrication system. The use of magnetic bearings could also increase the speed and the size of the shafts in the engine, thus reducing vibrations and possibly eliminating third bearings. Magnetic bearings can apply forces to the shafts and move them so that blade tips and seals do not rub. This could be part of an active vibration cancellation system. Also, whirling (displacing the shaft center line) may delay rotating stall and increase the stall margin of the engine. Magnetic bearings coupled with an integral starter generator could result in a more efficient 'more electric' engine. The IHPTET program, a joint DOD-industry program, has identified a need for a high temperature, (as high as 1200 F), magnetic bearing that could be demonstrated in a phase m engine. A magnetic bearing is similar to an electric motor. The magnetic bearing has a laminated rotor and stator made out of cobalt steel. The stator has a series of coils of wire wound around it. These coils f u. a series of electromagnets around the circumference. These magnets exert a force on the rotor to keep the rotor in the center of the cavity. The centering force is commanded by a controller based on shaft position, (measured by displacement probes). The magnetic bearing can only pull and is basically unstable before active control is applied The engine shafts, bearings, and case form a flexible structure which contain a large number of modes. A controller is necessary to stabilize these modes. A power amplifier is also necessary to provide the current prescribed by the controller to the magnetic bearings. In case of very high loads, a conventional back up bearing will engage and stop the rotor and stator from rubbing.

Kascak, Albert F.↗
NASA NTRS1993

Resources Management System

Delta Data Systems, Inc. was originally formed by NASA and industry engineers to produce a line of products that evolved from ELAS, a NASA-developed computer program. The company has built on that experience, using ELAS as the basis for other remote sensing products. One of these is AGIS, a computer package for geographic and land information systems. AGIS simultaneously processes remotely sensed and map data. The software is designed to operate on a low cost microcomputer, putting resource management tools within reach of small operators.

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NASA NTRS1985

Transportation by Air-On the Ground

A Rolair air flotation system is a spinoff of NASA/General Motors technology developed for the Apollo Program. It allows heavy loads to be moved easily by separating the load from the ground by a thin air cushion, virtually eliminating surface friction. Rolair Systems, Inc. was formed by former General Motors engineers and has successfully employed the system for both aerospace and nonaerospace industries.

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