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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 325 records · Page 18

Performance seeking control program overview

The Performance Seeking Control (PSC) program evolved from a series of integrated propulsion-flight control research programs flown at NASA Dryden Flight Research Center (DFRC) on an F-15. The first of these was the Digital Electronic Engine Control (DEEC) program and provided digital engine controls suitable for integration. The DEEC and digital electronic flight control system of the NASA F-15 were ideally suited for integrated controls research. The Advanced Engine Control System (ADECS) program proved that integrated engine and aircraft control could improve overall system performance. The objective of the PSC program was to advance the technology for a fully integrated propulsion flight control system. Whereas ADECS provided single variable control for an average engine, PSC controlled multiple propulsion system variables while adapting to the measured engine performance. PSC was developed as a model-based, adaptive control algorithm and included four optimization modes: minimum fuel flow at constant thrust, minimum turbine temperature at constant thrust, maximum thrust, and minimum thrust. Subsonic and supersonic flight testing were conducted at NASA Dryden covering the four PSC optimization modes and over the full throttle range. Flight testing of the PSC algorithm, conducted in a series of five flight test phases, has been concluded at NASA Dryden covering all four of the PSC optimization modes. Over a three year period and five flight test phases 72 research flights were conducted. The primary objective of flight testing was to exercise each PSC optimization mode and quantify the resulting performance improvements.

Orme, John S.↗

Analysis of oil lubricated, fluid film, thrust bearings with allowance for temperature dependent viscosity

A preliminary design study was performed to seek a fluid-film thrust bearing design intended to be part of a high-speed, hybrid (rolling element/fluid film) bearing configuration. The base line used is a design previously tested. To improve the accuracy of theoretical predictions of load capacity, flow rate, and friction power loss, an analytical procedure was developed to include curvature effects inherent in thrust bearings and to allow for the temperature rise in the fluid due to viscous heating. Also, a narrow-groove approximation in the treatment of the temperature field was formulated to apply the procedure to the Whipple thrust bearing. A comparative trade-off study was carried out assuming isothermal films; its results showed the shrouded-step design to be superior to the Whipple design for the intended application. An extensive parametric study was performed, employing isoviscous calculations, to determine the optimized design, which was subsequently recalculated allowing for temperature effects.

Pan, C. H. T.↗

Waveguide CO2 laser gain: Dependence on gas kinetic and discharge properties

Using a simple rate equation approach the gas kinetic and discharge properties of waveguide CO2 lasers were examined. The dependence was calculated of the population inversion and laser small signal gain on gas pressure, gas mixture, pumping rate (discharge current), tube bore diameter, and wall temperature. At higher pressures the gain is optimized by using more helium rich mixtures and smaller bore diameters. The dependence of laser tunability on the gas kinetic properties and cavity losses was determined, it was found that for loss cavities the laser tunability may substantially exceed the molecular fullwidth at half maximum. The more helium rich gas mixtures give greater tunability when cavity losses are small and less tunability when cavity losses are large. The role of the various gases in the waveguide CO2 laser is the same as that in conventional devices, by contrast with conventional lasers, the waveguide laser transition is homogeneously broadened. The dependence of gain on gas pressure and other kinetic and discharge properties differs substantially from that predicted by scaling results from conventional low pressure lasers.

Cohen, S. C.↗

Radiative equilibrium temperatures in the stratosphere and mesosphere - A comparison for the stellar occultation and BUV ozone data

Recently published ozone densities in the equatorial stratosphere and mesosphere from satellite stellar occultation measurements are appreciably larger than previous independent midlatitude measurements and ozone densities predicted by photochemical theory. Radiative equilibrium temperature profiles with a stratosphere-mesosphere optimized model have been calculated for each of these ozone profiles; it is found that the stellar occultation studies cannot be discounted on energy balance grounds.

Kuhn, W. R.↗

The catalysis of nucleotide polymerization by compounds of divalent lead

The nonenzymatic, nontemplate catalysis of nucleotide polymerization by Pb(2+) ions, a possible prebiotic catalyst, is reported. Adenosine and uridine phosphoimidazoles were reacted in buffered solutions of lead salts and products were analyzed by means of paper chromatography and electrophoresis. In the presence of Pb(2+) ion at pH 8.0 and 7.0 the reaction is found to progress rapidly with excellent yields of oligomers, with optimal yields observed at pH 8.0. Little temperature dependence in the range 0 to 30 C is observed, however hydrolysis of the reaction products is minimal when the reaction is carried out at 0 C. Results show that the yield of oligomers is insensitive to mixing or the source of lead ions, indicating that naturally occurring minerals or precipitates could be a source of Pb(2+) ions under prebiotic conditions.

Sleeper, H. L.↗

The effect of preparation conditions on the structure and mechanical properties of reaction-sintered silicon nitride

The microstructure of reaction sintered silicon nitride (RSSN) was changed over a wide range by varying the grain density, grain size of the silicon starting powder, nitriding conditions, and by introducing artificial pores. The influence of single microstructural parameters on mechanical properties like room temperature strength, creep behavior, and resistance to thermal shock was investigated. The essential factors influencing these properties were found to be total porosity, pore size distribution, and the fractions of alpha and beta Si3N4. In view of high temperature engineering applications of RSSN, potentials for optimizing the material's properties by controlled processing are discussed.

Heinrich, J.↗

Performance of computer-optimized tapered-roller bearings to 2.4 million DN

The temperature distribution and bearing heat generation of 120.65 mm bore high-speed tapered roller bearings was determined at shaft speeds of 20,000 rpm under simultaneous thrust and radial loads. The temperatures and thermal outputs were computed as functions of shaft speed, loading lubricant flow rates, and lubricant inlet temperatures. Bearing temperatures and heat generation were considerably lower than in standard bearings; cup cooling was effective in lowering cup temperatures to levels of cone temperatures.

Parker, R. J.↗

Experimental evaluation of a translating nozzle sidewall radial turbine

Studies have shown that reduced specific fuel consumption of rotorcraft engines can be achieved with a variable capacity engine. A key component in such an engine in a high-work, high-temperature variable geometry gas generator turbine. An optimization study indicated that a radial turbine with a translating nozzle sidewall could produce high efficiency over a wide range of engine flows but substantiating data were not available. An experimental program with Teledyne CAE, Toledo, Ohio was undertaken to evaluate the moving sidewall concept. A variety of translating nozzle sidewall turbine configurations were evaluated. The effects of nozzle leakage and coolant flows were also investigated. Testing was done in warm air (121 C). The results of the contractual program were summarized.

Roelke, Richard J.↗

Stabilization of high T(sub c) phase in bismuth cuprate superconductor by lead doping

It has widely been ascertained that doping of lead in Bi:Sr:Ca:Cu:O systems promotes the growth of high T(sub c) (110 K) phase, improves critical current density, and lowers processing temperature. A systematic investigation is undertaken to determine optimum lead content and processing conditions to achieve these. A large number of samples with cationic compositions of Bi(2-x)Pb(x)Sr2Ca2Cu3 (x = 0.2 to 2.0) were prepared by conventional solid state reaction technique. Samples of all compositions were annealed together at a temperature and characterized through resistance-temperature (R-T) measurements and x ray diffraction (XRD) to determine the zero resistance temperature, T(sub c)(0) and to identify presence of phases, respectively. The annealing temperature was varied between 790 C to optimize processing parameters. Results are given. In brief, an optimum process is reported along with composition of leaded bismuth cuprate superconductor which yields nearly a high T(sub c) single phase with highly stable superconducting properties.

Gupta, Ram. P.↗

Applying design principles to fusion reactor configurations for propulsion in space

We applied three design principles (DPs) to adapt and optimize three candidate-terrestrial-fusion-reactor configurations for propulsion in space. The three design principles are: (1) provide maximum direct access to space for waste radiation, (2) operate components as passive radiators to minimize cooling-system mass, and (3) optimize the plasma fuel, fuel mix, and temperature for best specific Jet power. The three candidate-terrestrial-fusion-reactor configurations are: (1) the thermal-barrier-tandem-mirror (TBTM), (2) field-reversed-mirror (FRM), and (3) levitated-dipole-field (LDF). The resulting three candidate-space-fusion-propulsion systems have their initial-mass-to-LEO minimized and their specific jet power and reusability maximized. We performed a preliminary rating of these configurations and concluded that the leading engineering-design solution to space fusion propulsion is a modified TBTM that we call the Mirror Fusion Propulsion System.

Carpenter, Scott A.↗

Applying design principles to fusion reactor configurations for propulsion in space

The application of fusion power to space propulsion requires rethinking the engineering-design solution to controlled-fusion energy. Whereas the unit cost of electricity (COE) drives the engineering-design solution for utility-based fusion reactor configurations; initial mass to low earth orbit (IMLEO), specific jet power (kW(thrust)/kg(engine)), and reusability drive the engineering-design solution for successful application of fusion power to space propulsion. We applied three design principles (DP's) to adapt and optimize three candidate-terrestrial-fusion-reactor configurations for propulsion in space. The three design principles are: provide maximum direct access to space for waste radiation, operate components as passive radiators to minimize cooling-system mass, and optimize the plasma fuel, fuel mix, and temperature for best specific jet power. The three candidate terrestrial fusion reactor configurations are: the thermal barrier tandem mirror (TBTM), field reversed mirror (FRM), and levitated dipole field (LDF). The resulting three candidate space fusion propulsion systems have their IMLEO minimized and their specific jet power and reusability maximized. We performed a preliminary rating of these configurations and concluded that the leading engineering-design solution to space fusion propulsion is a modified TBTM that we call the Mirror Fusion Propulsion System (MFPS).

Carpenter, Scott A.↗

Development of methodologies for the estimation of thermal properties associated with aerospace vehicles

Thermal stress analyses are an important aspect in the development of aerospace vehicles such as the National Aero-Space Plane (NASP) and the High-Speed Civil Transport (HSCT) at NASA-LaRC. These analyses require knowledge of the temperature within the structures which consequently necessitates the need for thermal property data. The initial goal of this research effort was to develop a methodology for the estimation of thermal properties of aerospace structural materials at room temperature and to develop a procedure to optimize the estimation process. The estimation procedure was implemented utilizing a general purpose finite element code. In addition, an optimization procedure was developed and implemented to determine critical experimental parameters to optimize the estimation procedure. Finally, preliminary experiments were conducted at the Aircraft Structures Branch (ASB) laboratory.

Scott, Elaine P.↗

Dual Wall Angles Would Enhance Performance Of A Solar Pond

Proposed dual-angle design for Sun-facing wall of solar pond enhances solar-energy-storage performance of pond; increase in performance over that of similar pond with conventional (single-angle) wall estimated to be 25 percent. Design compromises between maximizing heating and minimizing convection. Top part of Sun-facing wall optimized for top colder layer of water, less tendency toward convective mixing. Bottom part of wall optimized for bottom, warmer layer of water, greater tendency towards convection. Optimization involves consideration of both anticipated temperature-vs.-depth profile (affects tendency toward convection) and latitude (affects angle of incidence of solar radiation and rate of heating).

Noever, David A.↗

Determination of (alpha)-dialkylamino acids and their Enantiomers in Geological Samples by High-Performance Liquid Chromatography after Dervatization with a Chiral Adduct of (omicron)-Phthaldialdehyde

Derivatization with (omicron)-phthaldialdehyde (OPA) and the chiral thiol N-acetyl-L-cysteine (NAC) is a convenient and sensitive technique for the HPLC detection and resolution of protein amino acid enantiomers. The kinetics of the reaction of OPA-NAC with (alpha)-dialkylamino acids was investigated. The fluorescence yield of (alpha)-dialkylamino acids was only about 10% of that of protein amino acids when the derivatization was carried out at room temperature for 1-2 min, which is the procedure generally used for protein amino acid analyses. The fluorescence yield of (alpha)-dialkylamino acids can be enhanced by up to ten-fold when the derivatization reaction time is increased to 15 min at room temperature. The OPA-NAC technique was optimized for the detection and enantiomeric resolution of a-dialkylamino acids in geological samples which contain a large excess of protein amino acids. The estimated detection limit for a-dialkylamino acids is 1-2 pmol, comparable to that for protein amino acids.

Zhoa, Meixun↗

Development of Ultra Low Temperature, Impact Resistant Lithium Battery for the Mars Microprobe

The requirements of the power source for the Mars Microprobe, to be backpacked on the Mars 98 Spacecraft, are fairly demanding, with survivability to a shock of the order of 80,000 g combined with an operational requirement at -80 C. Development of a suitable power system, based on primary lithium-thionyl chloride is underway for the last eighteen months, together with Yardney Technical Products Inc., Pawcatuck, CT. The battery consists of 4 cells of 2 Ah capacity at 25 C, of which at least 25 % would be available at -80 C, at a moderate rate of C/20. Each probe contains two batteries and two such probes will be deployed. The selected cell is designed around an approximate 1/2 "D" cells, with flat plate electrodes. Significant improvements to the conventional Li-SOCl2 cell include: (a) use of tetrachlorogallate salt instead of aluminate for improved low temperature performance and reduced voltage delay, (b) optimization of the salt concentration, and (c) modification of the cell design to develop shock resistance to 80,000 g. We report here results from our several electrical performance tests, mission simulation tests, microcalorimetry and AC impedance studies, and Air gun tests. The cells have successfully gone through mission-enabling survivability and performance tests for the Mars Microprobe penetrator.

Frank, H.↗

Lithium-Ion Batteries for Aerospace Applications

This presentation reviews: (1) the goals and objectives, (2) the NASA and Airforce requirements, (3) the potential near term missions, (4) management approach, (5) the technical approach and (6) the program road map. The objectives of the program include: (1) develop high specific energy and long life lithium ion cells and smart batteries for aerospace and defense applications, (2) establish domestic production sources, and to demonstrate technological readiness for various missions. The management approach is to encourage the teaming of universities, R&D organizations, and battery manufacturing companies, to build on existing commercial and government technology, and to develop two sources for manufacturing cells and batteries. The technological approach includes: (1) develop advanced electrode materials and electrolytes to achieve improved low temperature performance and long cycle life, (2) optimize cell design to improve specific energy, cycle life and safety, (3) establish manufacturing processes to ensure predictable performance, (4) establish manufacturing processes to ensure predictable performance, (5) develop aerospace lithium ion cells in various AH sizes and voltages, (6) develop electronics for smart battery management, (7) develop a performance database required for various applications, and (8) demonstrate technology readiness for the various missions. Charts which review the requirements for the Li-ion battery development program are presented.

Surampudi, S.↗

Membrane Separation of Gases From The Martian Atmosphere

A test bed has been constructed to test membrane modules for separation of gases under temperature and pressure conditions normally encountered on the surface of Mars. The test bed allows independent control of (1) feed flow rates, (2) feed composition, (3) feed pressure, (4) permeate pressure, and (5) operating temperature. Preliminary data obtained at a nominal feed pressure of 760 torr and permeate pressure of 10 torr has demonstrated the ability of one membrane module to operate at temperatures as low as -70 C. At temperatures below -40 C, however, significant loss of carbon dioxide and argon was observed, probably indicating condensation at the relatively high pressure used. As expected, permeation flow rates decreased with decreasing temperature, the flow at -30 C approximately 37% of the value at +23 C. Values of permeability for individual gas components showed similar decreases with decreasing temperature, but permeability ratios changed significantly. For example, the ratio of the permeabilities of carbon dioxide and nitrogen increased from 2.6 at 23 C to 5.6 at -30 C. Additional data at lower operating pressures and temperatures must be obtained in order to optimize design of a usable separation system.

Jennings, Paul A.↗