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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Integrated Back-to-Back Barrier-N-N + Varactor Diode Tripler Using a Split-waveguide Block

The back-to-back barrier-N-N + (bbBNN) varactor is a nonlinear device being developed for frequency multiplier applications above 100 GHz. Its symmetrical C-V characteristic, low series resistance and suitability to planarization make it ideal choice for high frequency, low power, odd harmonic generation. In this paper, development of an integrated planar multiplier device and its performance as a 220 GHz tripler is presented. A new split-waveguide block design has been used to provide the proper embedding impedances to the device. The performance over 200-240 GHz has been measured and the integrated bbBNN device is shown to provide as much as 734 microwatts output power. A flange-to-flange tripling efficiency of 7% has been obtained. This is believed to be the highest conversion efficiency yet reported for all planar tripler at this frequency. The performance is expected to be improved further with minor changes to the device and circuit parameters.

interstellar↗
NASA NTRS2002

Photovoltaic Power for Future NASA Missions

Recent advances in crystalline solar cell technology are reviewed. Dual-junction and triple-junction solar cells are presently available from several U. S. vendors. Commercially available triple-junction cells consisting of GaInP, GaAs, and Ge layers can produce up to 27% conversion efficiency in production lots. Technology status and performance figures of merit for currently available photovoltaic arrays are discussed. Three specific NASA mission applications are discussed in detail: Mars surface applications, high temperature solar cell applications, and integrated microelectronic power supplies for nanosatellites.

Landis, Geoffrey↗
NASA NTRS2009

In-Phase Power-Combined Frequency Tripler at 300 GHz

This design starts with commercial 85- to 115-GHz sources that are amplified to as much as 250 mW using power amplifiers developed for the Herschel Space Observatory. The frequency is then tripled using a novel waveguide GaAs Schottky diode frequency tripler. This planar diode produces 26 mW at 318 GHz. Peak conversion efficiency is over 15 percent, and the measured bandwidth of about 265 - 30 GHz is limited more by the driving source than by the tripler itself. This innovation is based on an integrated circuit designed originally for a single-chip 260- to 340-GHz balanced tripler. The power-combined version has two mirror-image tripler chips that are power-combined in-phase in a single waveguide block using a compact Y-junction divider at the input waveguide, and a Y-junction combiner at the output waveguide. The tripler uses a split-block waveguide design with two independent DC bias lines.

Maestrini, Alain↗
NASA NTRS1994

Obscuration, orientation, and the infrared properties of radio-loud active galaxies

We report on a study of the mid- and far-infrared (MFIR) properties of several different classes of radio-loud active galactic nuclei (AGNs) using the IRAS database. Our goal is to try to improve the understanding of the possible relationships between the diverse classes of AGNs. The MFIR and radio properties of radio-loud AGNs are especially useful in this regard, since (excluding the blazar class, which we do not study here) the radio emission is thought to be emitted isotropically, and the radio and MFIR radiation should be much less affected by dust obscuration than radiation at shorter wavelengths. We have first compared samples of 3CR broad-line radio galaxies (BLRGs) and narrow-line radio galaxies (NLRGs) matched in radio flux and mean redshift. We find that the BLRGs are stronger than the NLRGs by a factor of 4-5 in their mid-IR emission but are similar to the NLRGs in the far-IR. This is qualitatively consistent with recent 'unification' models for NLRGs and BLRGs which invoke thermal MFIR emission from dusty 'obscuring tori,' but there may be an additional source of far-IR emission present in the more luminous broad-line objects (the radio-loud quasars) studied previously by Heckman, Chambers & Postman (1992). We have also compared samples of Fanaroff-Riley class I (FRI) and Fanaroff-Riley class II (FRII) radio galaxies matched in radio flux and redshift. The FRII galaxies are stronger MFIR emitters than the FRI galaxies by a factor of about 4. This is consistent with suggestions that the central engine in FRI galaxies produces relatively little radiant energy per unit jet power (expecially since we find that the weak MFIR emission from the FRI galaxies may not be powered by the AGN). Comparing samples of gigahertz-peaked spectrum (GPS) and compact steep spectrum (CSS) sources versus non-GPS-CSS sources, we find that the GPS-CSS and non-GPS-CSS sources have similar MFIR strengths. This suggests that the efficiency of the conversion of jet kinetic energy into radio emission is not much higher in the GPS-CSS sources, contrary to some theoretical predictions. Overall, we find that the MFIR and radio powers of all the classes of radio-loud AGNs we have studied correlate well with one another over a range of about 10(exp 3) in power. This is most naturally understood if the MFIR is primarily powered by the AGN in most highly luminous radio-loud AGNs. However, other processes (starbursts or the intracluster medium) may contribute significantly in the less radio-luminous radio galaxies.

Heckman, Timothy M.↗
NASA NTRS1993

Review of betavoltaic energy conversion

Betavoltaic energy conversion refers to the generation of power by coupling a beta source to a semiconductor junction device. The theory of betavoltaic energy conversion and some past studies of the subject are briefly reviewed. Calculations of limiting efficiencies for semiconductor cells versus bandgap are presented along with specific studies for Pm-147 and Ni-63 fueled devices. The approach used for fabricating Pm-147 fueled batteries by the author in the early 1970's is reviewed. Finally, the potential performance of advanced betavoltaic power sources is considered.

Olsen, Larry C.↗
NASA NTRS1976

Laser engines operating by resonance absorption

Basic tutorial article on the thermodynamic feasibility of laser engines at the present state of the art. Three main options are considered: (1) laser power applied externally to a heat reservoir (boiler approach); (2) internal heating of working fluid by resonance absorption; and (3) direct conversion of selective excitation into work. Only (2) is considered practically feasible at present. Basic concepts and variants, efficiency relations, upper temperature limits of laser engines, selection of absorbing gases, engine walls, bleaching, thermodynamic cycles of optimized laser engines, laser-powered turbines, laser heat pumps are discussed. Photon engines and laser dissociation engines are also considered.

Garbuny, M.↗
NASA NTRS2007

Advanced Stirling Convertor Testing at NASA Glenn Research Center

The U.S. Department of Energy (DOE), Lockheed Martin Space Systems (LMSS), Sunpower Inc., and NASA Glenn Research Center (GRC) have been developing an Advanced Stirling Radioisotope Generator (ASRG) for use as a power system on space science and exploration missions. This generator will make use of the free-piston Stirling convertors to achieve higher conversion efficiency than currently available alternatives. The ASRG will utilize two Advanced Stirling Convertors (ASC) to convert thermal energy from a radioisotope heat source to electricity. NASA GRC has initiated several experiments to demonstrate the functionality of the ASC, including: in-air extended operation, thermal vacuum extended operation, and ASRG simulation for mobile applications. The in-air and thermal vacuum test articles are intended to provide convertor performance data over an extended operating time. These test articles mimic some features of the ASRG without the requirement of low system mass. Operation in thermal vacuum adds the element of simulating deep space. This test article is being used to gather convertor performance and thermal data in a relevant environment. The ASRG simulator was designed to incorporate a minimum amount of support equipment, allowing integration onto devices powered directly by the convertors, such as a rover. This paper discusses the design, fabrication, and implementation of these experiments.

Oriti, Salvatore↗
NASA NTRS2007

Advanced Stirling Convertor Testing at NASA Glenn Research Center

The U.S. Department of Energy (DOE), Lockheed Martin Space Systems (LMSS), Sunpower Inc., and NASA Glenn Research Center (GRC) have been developing an Advanced Stirling Radioisotope Generator (ASRG) for use as a power system on space science and exploration missions. This generator will make use of the free-piston Stirling convertors to achieve higher conversion efficiency than currently available alternatives. The ASRG will utilize two Advanced Stirling Convertors (ASC) to convert thermal energy from a radioisotope heat source to electricity. NASA GRC has initiated several experiments to demonstrate the functionality of the ASC, including: in-air extended operation, thermal vacuum extended operation, and ASRG simulation for mobile applications. The in-air and thermal vacuum test articles are intended to provide convertor performance data over an extended operating time. These test articles mimic some features of the ASRG without the requirement of low system mass. Operation in thermal vacuum adds the element of simulating deep space. This test article is being used to gather convertor performance and thermal data in a relevant environment. The ASRG simulator was designed to incorporate a minimum amount of support equipment, allowing integration onto devices powered directly by the convertors, such as a rover. This paper discusses the design, fabrication, and implementation of these experiments.

Oriti, Salvatore M.↗
NASA NTRS2018

Creating a Multifunctional Composite Stator Slot Material System to Enable High Power Density Electric Machines for Electrified Aircraft Applications

Increasing the power density and efficiency of electric machines (motors and generators) is integral to bringing Electrified Aircraft (EA) to commercial realization. However, power density and efficiency are not qualities that can be developed independently. At the heart of any electric machine are the conductors (usually copper) that carry current and generate magnetic fields. Increased power density means increased current density and increased joule heating in a smaller volume. To increase efficiency at the wire level means minimizing electrical resistance and hence power lost to joule heating. There are fundamental challenges with concomitantly increasing both power density and efficiency since the copper resistivity is very temperature sensitive at common electric machine operating conditions. Simple calculations of the linear increase in resistivity of copper as a function of temperature, reveals that a one degree Celsius increase in temperature results in a 0.39% decrease in efficiency. Conversely, a 20 degree Celsius decrease in copper temperature produces a 7.8% increase in efficiency. Therefore, improved thermal management concepts for electric machine building blocks such as stator winding are a priority for improving efficiency and power density. This paper proposing changing the view of component materials in the stator slots from individual components with singular functionality to a composite system where the components take on a multifunctional roles. In the composite framework, achievable material development goals are defined that together have maximum system impact on the thermal environment inside of high power density electric machines for aerospace applications.

thermal management↗
NASA NTRS1985

Efficient frequency conversion of laser sources in nonlinear crystals

The use of nonlinear crystals to extend the frequency range of solid-state laser sources is proposed. The harmonic generation of high-average-power laser sources and CW-laser-sources nonlinear crystals is considered. The development of Nd:YAG pumped parametric oscillators and optical parametric amplifiers using LiNbO3 or AgGaS2 is studied. The LiNbO3 oscillator has tunable output over the 1.4-4.0 micron range and is applicable for remote sensing measurements of molecules and of humidity and temperature; AgGaS2 oscillators provide the potential for 3-15 micron infrared generation. Advances in material synthesis techniques related to the design and synthesis of nonlinear media are discussed. Various procedures for the synthesis of nonlinear crystals are described.

Byer, R. L.↗
NASA NTRS1972

Investigation of a liquid-metal magnetohydrodynamic power system.

Liquid-metal magnetohydrodynamic power conversion is being investigated for nuclear-electric propulsion. A liquid-metal MHD converter has no moving mechanical parts and requires a heat source temperature of only 1300 K. Cycle efficiencies of 5% to 8% for single-stage converters and 10% for multistage converters appear attainable. The specific weight of a 240 kWe MHD power plant has been estimated as 30 kg/kWe with shielding for unmanned science missions.

Elliott, D. G.↗
NASA NTRS1972

Study of aircraft electrical power systems

The formulation of a philosophy for devising a reliable, efficient, lightweight, and cost effective electrical power system for advanced, large transport aircraft in the 1980 to 1985 time period is discussed. The determination and recommendation for improvements in subsystems and components are also considered. All aspects of the aircraft electrical power system including generation, conversion, distribution, and utilization equipment were considered. Significant research and technology problem areas associated with the development of future power systems are identified. The design categories involved are: (1) safety-reliability, (2) power type, voltage, frequency, quality, and efficiency, (3) power control, and (4) selection of utilization equipment.

Source record↗
NASA NTRS1984

Overview of NASA Lewis Research Center free-piston Stirling engine activities

A generic free-piston Stirling technology project is being conducted to develop technologies generic to both space power and terrestrial heat pump applications in a cooperative, cost-shared effort. The generic technology effort includes extensive parametric testing of a 1 kW free-piston Stirling engine (RE-1000), development of a free-piston Stirling performance computer code, design and fabrication under contract of a hydraulic output modification for RE-1000 engine tests, and a 1000-hour endurance test, under contract, of a 3 kWe free-piston Stirling/alternator engine. A newly initiated space power technology feasibility demonstration effort addresses the capability of scaling a free-piston Stirling/alternator system to about 25 kWe; developing thermodynamic cycle efficiency or equal to 70 percent of Carnot at temperature ratios in the order of 1.5 to 2.0; achieving a power conversion unit specific weight of 6 kg/kWe; operating with noncontacting gas bearings; and dynamically balancing the system. Planned engine and component design and test efforts are described.

Slaby, J. G.↗
NASA NTRS1984

Overview of NASA Lewis Research Center free-piston Stirling engine activities

A generic free-piston Stirling technology project is being conducted to develop technologies generic to both space power and terrestrial heat pump applications in a cooperative, cost-shared effort. The generic technology effort includes extensive parametric testing of a 1 kW free-piston Stirling engine (RE-1000), development of a free-piston Stirling performance computer code, design and fabrication under contract of a hydraulic output modification for RE-1000 engine tests, and a 1000-hour endurance test, under contract, of a 3 kWe free-piston Stirling/alternator engine. A newly initiated space power technology feasibility demonstration effort addresses the capability of scaling a free-piston Stirling/alternator system to about 25 kWe; developing thermodynamic cycle efficiency or equal to 70 percent of Carnot at temperature ratios in the order of 1.5 to 2.0; achieving a power conversion unit specific weight of 6 kg/kWe; operating with noncontacting gas bearings; and dynamically balancing the system. Planned engine and component design and test efforts are described.

Slaby, J. G.↗
NASA NTRS1988

Radioisotope powered alkali metal thermoelectric converter design for space systems

The design concept of an alkali-metal thermoelectric converter (AMTEC) for 15-30-percent-efficient conversion of heat from the General Purpose (radioisotope) Heat Source (GPHS) on spacecraft is presented. The basic physical principles of the conversion cycle are outlined; a theoretical model is derived; a modular design is described and illustrated with drawings; and the overall AMTEC/GPHS system design is characterized. Predicted performance data are presented in extensive tables and graphs and discussed in detail.

Sievers, R. K.↗
NASA NTRS2010

Test Rack Development for Extended Operation of Advanced Stirling Convertors at NASA Glenn Research Center

The U.S. Department of Energy, Lockheed Martin Space Systems Company, Sunpower Inc., and NASA Glenn Research Center (GRC) have been developing an Advanced Stirling Radioisotope Generator (ASRG) for use as a power system on space science missions. This generator will make use of free-piston Stirling convertors to achieve higher conversion efficiency than with currently available alternatives. One part of NASA GRC's support of ASRG development includes extended operation testing of Advanced Stirling Convertors (ASCs) developed by Sunpower Inc. and GRC. The ASC consists of a free-piston Stirling engine integrated with a linear alternator. NASA GRC has been building test facilities to support extended operation of the ASCs for several years. Operation of the convertors in the test facility provides convertor performance data over an extended period of time. One part of the test facility is the test rack, which provides a means for data collection, convertor control, and safe operation. Over the years, the test rack requirements have changed. The initial ASC test rack utilized an alternating-current (AC) bus for convertor control; the ASRG Engineering Unit (EU) test rack can operate with AC bus control or with an ASC Control Unit (ACU). A new test rack is being developed to support extended operation of the ASC-E2s with higher standards of documentation, component selection, and assembly practices. This paper discusses the differences among the ASC, ASRG EU, and ASC-E2 test racks.

Dugala, Gina M.↗
NASA NTRS2026

Center for High-Efficiency Electrical Technologies for Aircraft: Phase I Final Report

Under the University Leadership Initiative (ULI), the Center for High-Efficiency for Electrical Technologies (CHEETA) was established to develop and mature early-stage technologies pertaining to hydrogen-electric power and energy systems for aircraft. In particular, integration of these technologies on an aircraft system is envisioned to leverage the high specific energy content of liquid hydrogen (LH2) with fuel cell energy conversion and an electrically driven ducted fan system to provide an ultra-efficient propulsion drivetrain. For this concept, the LH2 system is not just used as an energy storage mechanism, but also as a cryogen to enable highly efficient superconducting electric systems. The end result of this concept is an integrated aircraft system with a quiet, efficient propulsion architecture that produces zero CO2, NOx, SOx, and particulate matter emissions at the vehicle level.

Hydrogen↗