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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Large deflection analysis of a tension-foil bearing

The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are as follows: rolling or sliding contact within the bearing has life-limiting consequences; and REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's. CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contacts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exist for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. Recently, a new tension-foil bearing configuration has been proposed for turbomachinery applications.

Elrod, David A.↗
NASA NTRS1991

Update on results of SPRE testing at NASA Lewis

The Space Power Research Engine (SPRE), a free-piston Stirling engine with a linear alternator, is being tested at NASA Lewis Research Center as part of the Civilian Space Technology Initiative (CSTI) as a candidate for high capacity space power. Results are presented from recent SPRE tests designed to investigated the effects of variation in the displacer seal clearance and piston centering port area on engine performance and dynamics. The impact of these variations on PV power and efficiency are presented. Comparisons of the displacer seal clearance tests results with HFAST code predictions show good agreement for PV power, but show poor agreement for PV efficiency. Correlations are presented relating the piston midstroke position to the dynamic Delta P across the piston and the centering port area. Test results indicate that a modest improvement in PV power and efficiency may be realized with a reduction in piston centering port area.

Cairelli, James E.↗
NASA NTRS1991

Update on results of SPRE testing at NASA Lewis

The Space Power Research Engine (SPRE), a free-piston Stirling engine with a linear alternator, is being tested at NASA Lewis Research Center as part of the Civilian Space Technology Initiative (CSTI) as a candidate for high capacity space power. Results are presented from recent SPRE tests designed to investigate the effects of variation in the displacer seal clearance and piston centering port area on engine performance and dynamics. The effects of these variations on PV power and efficiency are presented. Comparisons of the displacer seal clearance test results with HFAST code predictions show good agreement for PV power but poor agreement for PV efficiency. Correlations are presented relating the piston mid-stroke position to the dynamic Delta P across the piston and the centering port area. Test results indicate that a modest improvement in PV power and efficiency may be realized with a reduction in piston centering port area.

Cairelli, James E.↗
NASA NTRS1977

Molten salt thermal energy storage for utility peaking loads

This paper considers the use of thermal energy storage (TES) in molten salts to increase the capacity of power plants. Five existing fossil and nuclear electric utility plants were selected as representative of current technology. A review of system load diagrams indicated that TES to meet loads over 95% of peak was a reasonable goal. Alternate TES heat exchanger locations were evaluated, showing that the stored energy should be used either for feedwater heating or to generate steam for an auxiliary power cycle. Specific salts for each concept are recommended. Design layouts were prepared for one plant, and it was shown that a TES tube/shell heat exchanger system could provide about 7% peaking capability at lower cost than adding steam generation capacity. Promising alternate heat exchanger concepts were also identified.

Ferrara, A.↗
NASA NTRS2003

Flasher Powered by Photovoltaic Cells and Ultracapacitors

A unique safety flasher powered by photovoltaic cells and ultracapacitors has been developed. Safety flashers are used wherever there are needs to mark actually or potentially hazardous locations. Examples of such locations include construction sites, highway work sites, and locations of hazardous operations. Heretofore, safety flashers have been powered by batteries, the use of which entails several disadvantages: Batteries must be kept adequately charged, and must not be allowed to become completely discharged. Batteries have rather short cycle lives, and their internal constituents that react chemically to generate electricity deteriorate (and hence power-generating capacities decrease) over time. The performances of batteries are very poor at low temperatures, which often occur in the circumstances in which safety flashers are most needed. The disposal of batteries poses a threat to the environment. The development of the present photovoltaic/ultracapacitor- powered safety flasher, in which the ultracapacitors are used to store energy, overcomes the aforementioned disadvantages of using batteries to store energy. The ultracapacitors in this flasher are electrochemical units that have extremely high volumetric capacitances because they contain large-surface-area electrodes separated by very small gaps. Ultracapacitors have extremely long cycle lives, as compared to batteries; consequently, it will never be necessary to replace the ultracapacitors in the safety flasher. The reliability of the flasher is correspondingly increased, and the life-of-system cost and the adverse environmental effects of the flasher are correspondingly reduced. Moreover, ultracapacitors have excellent low-temperature characteristics, are maintenance-free, and provide consistent performance over time.

Eichenberg, Dennis J.↗
NASA NTRS2002

Power System for Venus Surface Exploration

A radioisotope power and cooling system is designed to provide electrical power for a probe operating on the surface of Venus. Most foreseeable electronics devices and sensors cannot operate at the 450 C ambient surface temperature of Venus. Because the mission duration is substantially long and the use of thermal mass to maintain an operable temperature range is likely impractical, some type of active refrigeration may be required to keep electronic components at a temperature below ambient. The fundamental cooling parameters are the cold sink temperature, the hot sink temperature, and the amount of heat to be removed. In this instance, it is anticipated that electronics would have a nominal operating temperature of 300 C. Due to the highly thermal convective nature of the high-density (90 bar CO2) atmosphere, the hot sink temperature was assumed to be 50 C, which provided a 500 C temperature of the cooler's heat rejecter to the ambient atmosphere. The majority of the heat load on the cooler is from the high temperature ambient surface environment on Venus, with a small contribution of heat generation from electronics and sensors. Both thermoelectric (RTG) and dynamic power conversion systems were analyzed, based on use of a standard isotope (General-purpose heat source, or GPHS) brick. For the radioisotope Stirling power converter configuration designed, the Sage model predicts a thermodynamic power output capacity of 478.1 watts, which slightly exceeds the required 469.1 watts. The hot sink temperature is 1200 C, and the cold sink temperature is 500 C. The required heat input is 1740 watts. This gives a thermodynamic efficiency of 27.48 %. It is estimated that the mechanical efficiency of the power converter design is on the order of 85 %, based on experimental measurements taken from 500-watt power class, laboratory-tested Stirling engines. The overall efficiency is calculated to be 23.36 %. The mass of the power converter is estimated at approximately 21.6 kg. Additional information is included in the original extended abstract.

Landis, Geoffrey A.↗
NASA NTRS1975

Tug avionics system overview

The recently defined Tug avionics system takes maximum advantage of projected technology advances to attain: low system weight; power system capacity essentially independent of mission duration; sensors for rendezvous, docking, and navigation update; all attitude communications; onboard checkout and redundancy management; and modular fault tolerant computer control. The requirements, selection trades, and configurations are discussed for the major subsystems: data management, guidance navigation and control, communications, rendezvous and docking, and electrical power. The integrated avionics system and the interfaces with the payload, Shuttle and ground are described.

Raaberg, M. T.↗
NASA NTRS1978

A wide bandwidth CCD buffer memory system

A prototype system was implemented to demonstrate that CCD's can be applied advantageously to the problem of low power digital storage and particularly to the problem of interfacing widely varying data rates. CCD shift register memories (8K bit) were used to construct a feasibility model 128 K-bit buffer memory system. Serial data that can have rates between 150 kHz and 4.0 MHz can be stored in 4K-bit, randomly-accessible memory blocks. Peak power dissipation during a data transfer is less than 7 W, while idle power is approximately 5.4 W. The system features automatic data input synchronization with the recirculating CCD memory block start address. System expansion to accommodate parallel inputs or a greater number of memory blocks can be performed in a modular fashion. Since the control logic does not increase proportionally to increase in memory capacity, the power requirements per bit of storage can be reduced significantly in a larger system.

Siemens, K.↗
NASA NTRS2004

Venus Surface Power and Cooling System Design

A radioisotope power and cooling system is designed to provide electrical power for the a probe operating on the surface of Venus. Most foreseeable electronics devices and sensors simply cannot operate at the 450 C ambient surface temperature of Venus. Because the mission duration is substantially long and the use of thermal mass to maintain an operable temperature range is likely impractical, some type of active refrigeration may be required to keep certain components at a temperature below ambient. The fundamental cooling requirements are comprised of the cold sink temperature, the hot sink temperature, and the amount of heat to be removed. In this instance, it is anticipated that electronics would have a nominal operating temperature of 300 C. Due to the highly thermal convective nature of the high-density atmosphere, the hot sink temperature was assumed to be 50 C, which provided a 500 C temperature of the cooler's heat rejecter to the ambient atmosphere. The majority of the heat load on the cooler is from the high temperature ambient surface environment on Venus. Assuming 5 cm radial thickness of ceramic blanket insulation, the ambient heat load was estimated at approximately 77 watts. With an estimated quantity of 10 watts of heat generation from electronics and sensors, and to accommodate some level of uncertainty, the total heat load requirement was rounded up to an even 100 watts. For the radioisotope Stirling power converter configuration designed, the Sage model predicts a thermodynamic power output capacity of 478.1 watts, which slightly exceeds the required 469.1 watts. The hot sink temperature is 1200 C, and the cold sink temperature is 500 C. The required heat input is 1740 watts. This gives a thermodynamic efficiency of 27.48 %. The maximum theoretically obtainable efficiency is 47.52 %. It is estimated that the mechanical efficiency of the power converter design is on the order of 85 %, based on experimental measurements taken from 500 watt power class, laboratory-tested Stirling engines at GRC. The overall efficiency is calculated to be 23.36 %. The mass of the power converter is estimated at approximately 21.6 kg.

Landis, Geoffrey A.↗
NASA NTRS2005

International Space Station Electric Power System Performance Code-SPACE

The System Power Analysis for Capability Evaluation (SPACE) software analyzes and predicts the minute-by-minute state of the International Space Station (ISS) electrical power system (EPS) for upcoming missions as well as EPS power generation capacity as a function of ISS configuration and orbital conditions. In order to complete the Certification of Flight Readiness (CoFR) process in which the mission is certified for flight each ISS System must thoroughly assess every proposed mission to verify that the system will support the planned mission operations; SPACE is the sole tool used to conduct these assessments for the power system capability. SPACE is an integrated power system model that incorporates a variety of modules tied together with integration routines and graphical output. The modules include orbit mechanics, solar array pointing/shadowing/thermal and electrical, battery performance, and power management and distribution performance. These modules are tightly integrated within a flexible architecture featuring data-file-driven configurations, source- or load-driven operation, and event scripting. SPACE also predicts the amount of power available for a given system configuration, spacecraft orientation, solar-array-pointing conditions, orbit, and the like. In the source-driven mode, the model must assure that energy balance is achieved, meaning that energy removed from the batteries must be restored (or balanced) each and every orbit. This entails an optimization scheme to ensure that energy balance is maintained without violating any other constraints.

Hojnicki, Jeffrey↗
NASA NTRS2012

An Integrated, Layered-Spinel Composite Cathode for Energy Storage Applications

At low operating temperatures, commercially available electrode materials for lithium-ion batteries do not fully meet the energy and power requirements for NASA fs exploration activities. The composite cathode under development is projected to provide the required energy and power densities at low temperatures and its usage will considerably reduce the overall volume and weight of the battery pack. The newly developed composite electrode material can provide superior electrochemical performance relative to a commercially available lithium cobalt system. One advantage of using a composite cathode is its higher energy density, which can lead to smaller and lighter battery packs. In the current program, different series of layered-spinel composite materials with at least two different systems in an integrated structure were synthesized, and the volumetric and gravimetric energy densities were evaluated. In an integrated network of a composite electrode, the effect of the combined structures is to enhance the capacity and power capabilities of the material to levels greater than what is possible in current state-of-the-art cathode systems. The main objective of the current program is to implement a novel cathode material that meets NASA fs low temperature energy density requirements. An important feature of the composite cathode is that it has at least two components (e.g., layered and spinel) that are structurally integrated. The layered material by itself is electrochemically inactive; however, upon structural integration with a spinel material, the layered material can be electrochemically activated, thereby delivering a large amount of energy with stable cycling. A key aspect of the innovation has been the development of a scalable process to produce submicronand micron-scale particles of these composite materials. An additional advantage of using such a composite electrode material is its low irreversible loss (.5%), which is primarily due to the unique activation of the composite. High columbic efficiency (greater than 99%) upon cycling may indicate the formation of a stable SEI (solid-electrolyte interface) layer, which can contribute to long cycle life. The innovation in the current program, when further developed, will enable the system to maintain high energy and power densities at low temperatures, improve efficiency, and further stabilize and enhance the safety of the cell.

Hagh, Nader↗
NASA NTRS1969

Fuel element concept for long life high power nuclear reactors

Nuclear reactor fuel elements have burnups that are an order of magnitude higher than can currently be achieved by conventional design practice. Elements have greater time integrated power producing capacity per unit volume. Element design concept capitalizes on known design principles and observed behavior of nuclear fuel.

Mcdonald, G. E.↗
NASA NTRS1972

High power microstrip RF switches.

Description of a microstrip-type single-pole double-throw switch, which uses only two PIN diodes, eliminates usual dc blocking capacitors, and has demonstrated an RF power handling capacity greater than 100 W CW at S-band. The insertion loss is less than 0.25 dB, and the input-to-off port isolation is greater than 36 dB over a bandwidth larger than 30 MHz.

Choi, S. D.↗
NASA NTRS1974

Microstrip antenna study for Pioneer Saturn/Uranus atmosphere entry probe

The design parameters of a microstrip antenna were studied to determine its performance characteristics as affected by an atmospheric entry probe environment. The technical literature was reviewed to identify the known design and performance characteristics. These data were used to evaluate the expected effects of mission environments on the microstrip antenna design proposed for the Saturn/Uranus Atmospheric Entry Probe (SAEP). Radiation patterns and VSWR measurements were made to evaluate the performance in the SAEP thermal environment. Results of the literature search and pattern tests confirm that the microstrip antenna is a good choice as a transmitting antenna on the SAEP. The microstrip antenna is efficient, compact, and well suited to a space environment. The pattern can be controlled with a minimum beamwidth of 60 degrees (air substrate; e.g., honeycomb structure) and a maximum on the order of 100 degrees with higher dielectric constant substrates. The power handling capacity is good and can be improved by covering the antenna with a dielectric cover.

Kuhlman, E. A.↗
NASA NTRS1978

The 30-cm ion thruster power processor

A power processor unit for powering and controlling the 30 cm Mercury Electron-Bombardment Ion Thruster was designed, fabricated, and tested. The unit uses a unique and highly efficient transistor bridge inverter power stage in its implementation. The system operated from a 200 to 400 V dc input power bus, provides 12 independently controllable and closely regulated dc power outputs, and has an overall power conditioning capacity of 3.5 kW. Protective circuitry was incorporated as an integral part of the design to assure failure-free operation during transient and steady-state load faults. The implemented unit demonstrated an electrical efficiency between 91.5 and 91.9 at its nominal rated load over the 200 to 400 V dc input bus range.

Herron, B. G.↗
NASA NTRS1980

Simplified fatigue life analysis for traction drive contacts

A simplified fatigue life analysis for traction drive contacts of arbitrary geometry is presented. The analysis is based on the Lundberg-Palmgren theory used for rolling-element bearings. The effects of torque, element size, speed, contact ellipse ratio, and the influence of traction coefficient are shown. The analysis shows that within the limits of the available traction coefficient, traction contacts exhibit longest life at high speeds. Multiple, load-sharing roller arrangements have an advantageous effect on system life, torque capacity, power-to-weight ratio and size.

Rohn, D. A.↗
NASA NTRS1980

Simplified fatigue life analysis for traction drive contacts

A simplified fatigue life analysis for traction drive contacts of arbitrary geometry is presented. The analysis is based on the Lundberg-Palmgren theory used for rolling-element bearings. The effects of torque, element size, speed, contact ellipse ratio, and the influence of traction coefficient are shown. The analysis shows that within the limits of the available traction coefficient, traction contacts exhibit longest life at high speeds. Multiple, load-sharing roller arrangements have an advantageous effect on system life, torque capacity, power-to-weight ratio and size.

Rohn, D. A.↗
NASA NTRS1985

Optical Mass Memory System Specification

Specifications given for computer controlled optical mass memory system that stores and retrieves data from silver halide fiches 148-mmsquare and 7 mils (0.18mm) thick at user bit density of 30 Mbit/in. 2 (4.7 Mbit/cm2) with uncorrectable bit-error rate of 10 to negative 9th power or less. Allows for expansion to 10 the 15th power bit capacity.

Source record↗