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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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31 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Status of 30 cm mercury ion thruster development

Two engineering model 30-cm ion thrusters have been assembled, calibrated, and qualification tested. This paper discusses the thruster design, performance, and power system. Test results include documentation of thrust losses due to doubly charged mercury ions and beam divergence by both direct thrust measurements and beam probes. Diagnostic vibration tests have led to improved designs of the thruster backplate structure, feed system, and harness. Thruster durability is being demonstrated over a thrust range of 97 to 113 mN at a specific impulse of about 2900 seconds. As of August 15, 1974, the thruster has successfully operated for over 4000 hours.

Sovey, J. S.↗
NASA NTRS1975

Compressed air demand-type firefighter's breathing system, volume 1

The commercial availability of lightweight high pressure compressed air vessels has resulted in a lightweight firefighter's breathing apparatus. The improved apparatus, and details of its design and development are described. The apparatus includes a compact harness assembly, a backplate mounted pressure reducer assembly, a lightweight bubble-type facemask with a mask mounted demand breathing regulator. Incorporated in the breathing regulator is exhalation valve, a purge valve and a whistle-type low pressure warning that sounds only during inhalation. The pressure reducer assembly includes two pressure reducers, an automatic transfer valve and a signaling device for the low pressure warning. Twenty systems were fabricated, tested, refined through an alternating development and test sequence, and extensively examined in a field evaluation program. Photographs of the apparatus are included.

Sullivan, J. L.↗
NASA NTRS1977

A high-temperature wideband pressure transducer

A condenser microphone AM carrier system, which has been developed to measure pressure fluctuations at elevated temperatures, consists of the following components: a condenser microphone designed for operation at elevated temperatures; existing carrier electronics developed under two previous research grants but adapted to meet present requirements; a 6 m cable operating as a half-wavelength transmission line between the microphone and carrier electronics; and a voltage-controlled oscillator used in a feedback loop for automatic tuning control. Both theoretical and practical aspects of the development program are considered. The three predominant effects of temperature changes are changes in the membrane-backplate gap, membrane tension, and air viscosity. The microphone is designed so that changes in gap and membrane tension tend to have compensating effects upon the microphone sensitivity.

Zuckerwar, A. J.↗
NASA NTRS1984

A high performance magnetoplasmadynamic thruster

A flared-anode MPD thruster has been modified to permit injection of propellant through the backplate near the anode wall. At 6 g/sec argon, this thruster displays an onset current of 41.4 kA, almost double the value observed for propellant injection at the cathode and intermediate radial positions. A magnetic field survey of the interelectrode region shows current density is highest at the upstream and downstream ends of the chamber. The operating efficiency at onset current inferred from magnetic field data exceeds 50 percent, but swinging-gate thrust stand measurements reveal a progressive divergence between inferred and actual thrust with increasing power. Near onset, the measured thrust is approximately 20 percent lower than that inferred from magnetic probing. Explanations for this behavior have been explored with viscous drag emerging as the most probable cause of performance degradation.

Wolff, M.↗
NASA NTRS1990

Toward decimeter Topex orbit determination using GPS

Several practical aspects of precision GPS-based Topex orbit determination are investigated. Multipath signals contaminating Topex pseudorange data are greatly reduced by placing the GPS antenna on a conducting backplate consisting of concentric choke rings to attenuate signals coming in from the Topex horizon and below, and by elevating it on a boom to keep it well above all reflecting surfaces. A proper GPS antenna cutoff view angle is chosen so that a sufficient number of GPS satellites with good geometry are in view while reception of reflected signals is minimized. The geometrical strength of the tracking data is optimized by properly selecting GPS satellites to be observed so as to provide data with moderate continuity, low PDOP, and common visibility with ground tracking sites. The tracking performance is greatly enhanced when three complementary sites are added to the minimum ground tracking network consisting of the three NASA DSN sites.

Wu, Sien-Chong↗
NASA NTRS1991

Development and testing of CMC components for automotive gas turbine engines

Ceramic matrix composite (CMC) materials are currently being developed and evaluated for advanced gas turbine engine components because of their high specific strength and resistance to catastrophic failure. Components with 2D and 3D composite architectures have been successfully designed and fabricated. This is an overview of the test results for a backplate, combustor, and a rotor.

Khandelwal, Pramod K.↗
NASA NTRS1992

Multimegawatt MPD thruster design considerations

Performance and lifetime requirements for multimegawatt magnetoplasmadynamic (MPD) thrusters were used to establish a baseline 2.5 MW thruster design. The chamber surface power deposition resulting from current conduction, plasma and surface radiation, and conduction from the hot plasma was then evaluated to establish the feasibility of thruster operation. It was determined that state of the art lithium heat pipes were adequate to cool the anode electrode, and that the liquid hydrogen propellant could be used to cool the applied field magnet, cathode, and backplate. Unresolved issues having an impact of thruster design are discussed to help focus future research.

Myers, Roger M.↗
NASA NTRS1992

Theoretical and experimental study of a fiber optic microphone

Modifications to condenser microphone theory yield new expressions for the membrane deflections at its center, which provide the basic theory for the fiber optic microphone. The theoretical analysis for the membrane amplitude and the phase response of the fiber optic microphone is given in detail in terms of its basic geometrical quantities. A relevant extension to the original concepts of the optical microphone includes the addition of a backplate with holes similar in design to present condenser microphone technology. This approach generates improved damping characteristics and extended frequency response that were not previously considered. The construction and testing of the improved optical fiber microphone provide experimental data that are in good agreement with the theoretical analysis.

Hu, Andong↗
NASA NTRS2007

Microrectenna: A Terahertz Antenna and Rectifier on a Chip

A microrectenna that would operate at a frequency of 2.5 THz has been designed and partially fabricated. The circuit is intended to be a prototype of an extremely compact device that could be used to convert radio-beamed power to DC to drive microdevices (see Figure 1). The microrectenna (see Figure 2) circuit consists of an antenna, a diode rectifier and a DC output port. The antenna consists of a twin slot array in a conducting ground plane (denoted the antenna ground plane) over an enclosed quarter-wavelength-thick resonant cavity (denoted the reflecting ground plane). The circuit also contains a planar high-frequency low-parasitic Schottky-barrier diode, a low-impedance microstrip transmission line, capacitors, and contact beam leads. The entire 3-D circuit is fabricated monolithically from a single GaAs wafer. The resonant cavity renders the slot radiation pattern unidirectional with a half-power beam width of about 65. A unique metal mesh on the rear of the wafer forms the backplate for the cavity but allows the GaAs to be wet etched from the rear surface of the twin slot antennas and ground plane. The beam leads protrude past the edge of the chip and are used both to mount the microrectenna and to make the DC electrical connection with external circuitry. The antenna ground plane and the components on top of it are formed on a 2- m thick GaAs membrane that is grown in the initial wafer MBE (molecular beam epitaxy) process. The side walls of the antenna cavity are not metal coated and, hence, would cause some loss of power; however, the relatively high permittivity (epsilon=13) of the GaAs keeps the cavity modes well confined, without the usual surface-wave losses associated with thick dielectric substrates. The Schottky-barrier diode has the usual submicron dimensions associated with THz operation and is formed in a mesa process above the antenna ground plane. The diode is connected at the midpoint of a microstrip transmission line, which is formed on 1- m-thick SiO (permittivity of 5) laid down on top of the GaAs membrane. The twin slots are fed in phase by this structure. To prevent radio-frequency (RF) leakage past the slot antennas, low-loss capacitors are integrated into the microstrip transmission line at the edges of the slots. The DC current- carrying lines extend from the outer edges of the capacitors, widen approaching the edges of the chip, and continue past the edges of the chip to become the beam leads used in tacking down the devices. The structure provides a self-contained RF to DC converter that works in the THz range.

Siegel, Peter↗
NASA NTRS2011

High Power Flex-Propellant Arcjet Performance

A MW-class electrothermal arcjet based on a water-cooled, wall-stabilized, constricted arc discharge configuration was subjected to extensive performance testing using hydrogen and simulated ammonia propellants with the deliberate aim of advancing technology readiness level for potential space propulsion applications. The breadboard design incorporates alternating conductor/insulator wafers to form a discharge barrel enclosure with a 2.5-cm internal bore diameter and an overall length of approximately 1 meter. Swirling propellant flow is introduced into the barrel, and a DC arc discharge mode is established between a backplate tungsten cathode button and a downstream ringanode/ spin-coil assembly. The arc-heated propellant then enters a short mixing plenum and is accelerated through a converging-diverging graphite nozzle. This innovative design configuration differs substantially from conventional arcjet thrusters, in which the throat functions as constrictor and the expansion nozzle serves as the anode, and permits the attainment of an equilibrium sonic throat (EST) condition. During the test program, applied electrical input power was varied between 0.5-1 MW with hydrogen and simulated ammonia flow rates in the range of 4-12 g/s and 15-35 g/s, respectively. The ranges of investigated specific input energy therefore fell between 50-250 MJ/kg for hydrogen and 10-60 MJ/kg for ammonia. In both cases, observed arc efficiencies were between 40-60 percent as determined via a simple heat balance method based on electrical input power and coolant water calorimeter measurements. These experimental results were found to be in excellent agreement with theoretical chemical equilibrium predictions, thereby validating the EST assumption and enabling the utilization of standard TDK nozzle expansion analyses to reliably infer baseline thruster performance characteristics. Inferred specific impulse performance accounting for recombination kinetics during the expansion process implied nearly frozen flow in the nozzle and yielded performance ranges of 800-1100 sec for hydrogen and 400-600 sec for ammonia. Inferred thrust-to-power ratios were in the range of 30-10 lbf/MWe for hydrogen and 60-20 lbf/MWe for ammonia. Successful completion of this test series represents a fundamental milestone in the progression of high power arcjet technology, and it is hoped that the results may serve as a reliable touchstone for the future development of MW-class regeneratively-cooled flex-propellant plasma rockets.

Litchford, Ron J.↗
NASA NTRS2017

A Cryogenic Thermal Source for Detector Array Characterization

We describe the design, fabrication, and validation of a cryogenically compatible quasioptical thermal source for characterization of detector arrays. The source is constructed using a graphite-loaded epoxy mixture that is molded into a tiled pyramidal structure. The mold is fabricated using a hardened steel template produced via a wire electron discharge machining process. The absorptive mixture is bonded to a copper backplate enabling thermalization of the entire structure and measurement of the source temperature. Measurements indicate that the reflectance of the source is less than 0.001 across a spectral band extending from 75 to 330 gigahertz.

Chuss, David T.↗
NASA NTRSDate not supplied

Advanced Material Options for the Portable Life Support System

Meeting an aggressive mass requirement is a challenge for new space suit development efforts, including that of the Exploration Extravehicular Mobility Unit Portable Life Support System (PLSS) government reference design. To reduce overall system mass, titanium was selected as the primary metal for the PLSS backplate and thermal loop. However, galvanically compatible metals (Hastelloy, Inconel, Monel) have relatively high densities and require further design complexities such as coatings and more challenging manufacturing. Efforts to reduce the mass of the government reference design for an International Space Station (ISS) or lunar mission were halted due to the government’s transition to a commercial Extravehicular Activity (EVA) services approach, but research was conducted into methodologies for mass savings using advanced materials. With the advent of a lunar Artemis mission and potential for future Mars missions, mass becomes a more critical driver going forward. Therefore, alternative materials and processes must be considered to fully close the mass requirement. There are many new materials and processes that can be considered; however, considerations must be made to ensure galvanic compatibility, radiation concerns for sensitive electronics, vacuum compatibility, tight tolerances, fluid compatibility with oxygen and water, and thread insert options. Individual PLSS components may have different requirements and need to be considered separately for reducing overall mass. This report will touch on comparisons between advanced materials, focusing on composites, additive manufacturing, and plastics. It will also address the different processes that may need to be applied when using these materials in the harsh environment of space. Lastly, it will look at specific components and make recommendations for options to reduce the mass of each one.

Ryan Ogilvie↗
NASA NTRS2024

Advanced Material Options for the Portable Life Support System (PLSS)

Meeting an aggressive mass requirement is a challenge for new space suit development efforts, including that of the Exploration Extravehicular Mobility Unit Portable Life Support System (PLSS) government reference design. To reduce overall system mass, titanium was selected as the primary metal for the PLSS backplate and thermal loop. However, galvanically compatible metals (Hastelloy, Inconel, Monel) have relatively high densities and require further design complexities such as coatings and more challenging manufacturing. Efforts to reduce the mass of the government reference design for an International Space Station (ISS) or lunar mission were halted due to the government’s transition to a commercial Extravehicular Activity (EVA) services approach, but research was conducted into methodologies for mass savings using advanced materials. With the advent of a lunar Artemis mission and potential for future Mars missions, mass becomes a more critical driver going forward. Therefore, alternative materials and processes must be considered to fully close the mass requirement. There are many new materials and processes that can be considered; however, considerations must be made to ensure galvanic compatibility, radiation concerns for sensitive electronics, vacuum compatibility, tight tolerances, fluid compatibility with oxygen and water, and thread insert options. Individual PLSS components may have different requirements and need to be considered separately for reducing overall mass. This report will touch on comparisons between advanced materials, focusing on composites, additive manufacturing, and plastics. It will also address the different processes that may need to be applied when using these materials in the harsh environment of space. Lastly, it will look at specific components and make recommendations for options to reduce the mass of each one.

Ryan Ogilvie↗