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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 883 records · Page 49

Decay Properties of K-Vacancy States in Fe X-Fe XVII

We report extensive calculations of the decay properties of fine-structure K-vacancy levels in Fe X-Fe XVII. A large set of level energies, wavelengths, radiative and Auger rates, and fluorescence yields has been computed using three different standard atomic codes, namely Cowan's HFR, AUTOSTRUCTURE and the Breit-Pauli R-matrix package. This multi-code approach is used to the study the effects of core relaxation, configuration interaction and the Breit interaction, and enables the estimate of statistical accuracy ratings. The Ksigma and KLL Auger widths have been found to be nearly independent of both the outer-electron configuration and electron occupancy keeping a constant ratio of 1.53 +/- 0.06. By comparing with previous theoretical and measured wavelengths, the accuracy of the present set is determined to be within 2 m Angstrom. Also, the good agreement found between the different radiative and Auger data sets that have been computed allow us to propose with confidence an accuracy rating of 20% for the line fluorescence yields greater than 0.01. Emission and absorption spectral features are predicted finding good correlation with measurements in both laboratory and astrophysical plasmas.

Mendoza, C.↗

Power-Amplifier Module for 145 to 165 GHz

A power-amplifier module that operates in the frequency range of 145 to 165 GHz has been designed and constructed as a combination of (1) a previously developed monolithic microwave integrated circuit (MMIC) power amplifier and (2) a waveguide module. The amplifier chip was needed for driving a high-electron-mobility-transistor (HEMT) frequency doubler. While it was feasible to connect the amplifier and frequency-doubler chips by use of wire bonds, it was found to be much more convenient to test the amplifier and doubler chips separately. To facilitate separate testing, it was decided to package the amplifier and doubler chips in separate waveguide modules. Figure 1 shows the resulting amplifier module. The amplifier chip was described in "MMIC HEMT Power Amplifier for 140 to 170 GHz" (NPO-30127), NASA Tech Briefs, Vol. 27, No. 11, (November 2003), page 49. To recapitulate: This is a three-stage MMIC power amplifier that utilizes HEMTs as gain elements. The amplifier was originally designed to operate in the frequency range of 140 to 170 GHz. The waveguide module is based on a previously developed lower frequency module, redesigned to support operation in the frequency range of 140 to 220 GHz. Figure 2 presents results of one of several tests of the amplifier module - measurements of output power and gain as functions of input power at an output frequency of 150 GHz. Such an amplifier module has many applications to test equipment for power sources above 100 GHz.

Samoska, Lorene↗

X- to Ka- Band Cryogenic LNA Module for Very Long Baseline Interferometry

We report a new result of a packaged low noise amplifier (LNA) module with wide bandwidth of 5 to 35 GHz with low noise temperature performance of 10 - 18 K, while operated at 10 K ambient. The LNA used 3-stages of sub-50 nm gate length, 100% indium channel content indium phosphide (InP) high electron mobility transistors (HEMTs). Wideband cryogenic LNAs are important for future radio astronomy observatories. To our knowledge these results represent the lowest noise achieved in a wideband amplifier from 5-35 GHz.

Fung, Andy↗

Aircraft electromagnetic compatibility

Illustrated are aircraft architecture, electromagnetic interference environments, electromagnetic compatibility protection techniques, program specifications, tasks, and verification and validation procedures. The environment of 400 Hz power, electrical transients, and radio frequency fields are portrayed and related to thresholds of avionics electronics. Five layers of protection for avionics are defined. Recognition is given to some present day electromagnetic compatibility weaknesses and issues which serve to reemphasize the importance of EMC verification of equipment and parts, and their ultimate EMC validation on the aircraft. Proven standards of grounding, bonding, shielding, wiring, and packaging are laid out to help provide a foundation for a comprehensive approach to successful future aircraft design and an understanding of cost effective EMC in an aircraft setting.

Clarke, Clifton A.↗

Implementation of Adaptive Digital Controllers on Programmable Logic Devices

Much has been made of the capabilities of Field Programmable Gate Arrays (FPGA's) in the hardware implementation of fast digital signal processing functions. Such capability also makes an FPGA a suitable platform for the digital implementation of closed loop controllers. Other researchers have implemented a variety of closed-loop digital controllers on FPGA's. Some of these controllers include the widely used Proportional-Integral-Derivative (PID) controller, state space controllers, neural network and fuzzy logic based controllers. There are myriad advantages to utilizing an FPGA for discrete-time control functions which include the capability for reconfiguration when SRAM- based FPGA's are employed, fast parallel implementation of multiple control loops and implementations that can meet space level radiation tolerance requirements in a compact form-factor. Generally, a software implementation on a Digital Signal Processor (DSP) device or microcontroller is used to implement digital controllers. At Marshall Space Flight Center, the Control Electronics Group has been studying adaptive discrete-time control of motor driven actuator systems using DSP devices. While small form factor, commercial DSP devices are now available with event capture, data conversion, Pulse Width Modulated (PWM) outputs and communication peripherals, these devices are not currently available in designs and packages which meet space level radiation requirements. In general, very few DSP devices are produced that are designed to meet any level of radiation tolerance or hardness. An alternative is required for compact implementation of such functionality to withstand the harsh environment encountered on spacemap. The goal of this effort is to create a fully digital, flight ready controller design that utilizes an FPGA for implementation of signal conditioning for control feedback signals, generation of commands to the controlled system, and hardware insertion of adaptive-control algorithm approaches. Radiation tolerant FPGA's are a feasible option for reaching this goal.

Gwaltney, David A.↗

Characterizing the Performance of the Wheel Electrostatic Spectrometer

A Wheel Electrostatic Spectrometer has been developed as a surveying tool to be incorporated into a Martian rover design. Electrostatic sensors with various protruding cover insulators are embedded into a prototype rover wheel. When these insulators come into contact with a surface, a charge develops on the cover insulator through tribocharging. A charge spectrum is created by analyzing the accumulated charge on each of the dissimilar cover insulators. This charge spectrum can be used to determine differences in Martian regolith properties. In this study, we analyzed the repeatability of the measurements for this sensor package and found that the sensor repeatability lies within one standard deviation of the noise in the signal. In addition, we tested the need for neutralizing the surface charge on the cover insulators and discovered a need to discharge the sensor cover insulators after each revolution. Future work includes an electronics redesign to reduce noise and a Martian pressure static elimination tool that can be used to neutralize the charge on the sensor cover insulators after each wheel revolution.

Johansen, M. R.↗

A cryogenic multichannel electronically scanned pressure module

Consideration is given to a cryogenic multichannel electronically scanned pressure (ESP) module developed and tested over an extended temperature span from -184 to +50 C and a pressure range of 0 to 5 psig. The ESP module consists of 32 pressure sensor dice, four analog 8 differential-input multiplexers, and an amplifier circuit, all of which are packaged in a physical volume of 2 x 1 x 5/8 in with 32 pressure and two reference ports. Maximum nonrepeatability is measured at 0.21 percent of full-scale output. The ESP modules have performed consistently well over 15 times over the above temperature range and continue to work without any sign of degradation. These sensors are also immune to repeated thermal shock tests over a temperature change of 220 C/sec.

Shams, Qamar A.↗

A New Instrument Design for Imaging Low Energy Neutral Atoms

The MidSTAR-2 satellite, to be built at the US Naval Academy as a follow-on to the successful MidSTAR-1 satellite (http://web.ew.usna.edu/~midstar/), will launch in 2011 and carry three Goddard Space Flight Center (GSFC) experiments developed under Goddard's Internal Research and Development (IRAD) program. One of these GSFC instruments, the Miniature Imager for Neutral Ionospheric atoms and Magnetospheric Electrons (MINI-ME) builds on the heritage of the Goddard-developed Low-Energy Neutral Atom (LENA) imager launched on the IMAGE spacecraft in 2000. MINI-ME features a Venetian-blind conversion surface assembly that improves both light rejection and conversion efficiency in a smaller and lighter package than LENA making this an highly effective instrument for viewing solar wind charge exchange with terrestrial and planetary exospheres. We will describe the MINI-ME prototyping effort and its science targets.

Keller, John W.↗

Method for Fabricating and Packaging an M.Times.N Phased-Array Antenna

A method for fabricating an M.times.N, P-bit phased-array antenna on a flexible substrate is disclosed. The method comprising ink jet printing and hardening alignment marks, antenna elements, transmission lines, switches, an RF coupler, and multilayer interconnections onto the flexible substrate. The substrate of the M.times.N, P-bit phased-array antenna may comprise an integrated control circuit of printed electronic components such as, photovoltaic cells, batteries, resistors, capacitors, etc. Other embodiments are described and claimed.

Subbaraman, Harish↗

Milli-Watt Radioisotope Power to Enable Small, Long-Term Robotic “Probe” Space Exploration

Milli-watt Radioisotope Power Systems (RPS) based on Radioisotope Heater Units (RHUs) could be an ideal power source for certain spacecraft that cannot use solar power due to large distances from the sun, or other environmental constraints, and where they enable or significantly enhance the ability of a mission to meet its scientific or operational goals. Various modular, compact RHU-based thermoelectric (TE) generator concepts developed or derived from current NASA Small Business Innovation Research (SBIR) projects satisfying this need have been investigated. These modular, compact and low mass power systems could support small, highly-mobile robotic exploration packages, and could be incorporated into different robotic package concepts, spacecraft or satellites. Current modular RPS design concepts with 40mW, 80mW and 120mW power levels use RHUs and Bi2Te3 TE converters. Skutterudites materials could be used in the future if new higher thermal energy output and higher temperature miniature heat sources were developed, for example, using technologies currently in the General Purpose Heat Source (GPHS) used in higher electric power output RTGs. Small (a.k.a., “mice-like”) robotic packages could effectively utilize these RHU-driven power levels to accommodate crawling, climbing, monitoring, taking measurements, and communicating during long-term planetary missions aimed at gathering environmental and geologic data (i.e., over multiple decades). Waste heat from the cold side of the TE converter could also be directed toward the electronics and / or energy storage (e.g. batteries) to keep them within design temperature ranges. In addition to power generation and electronics / battery heating, the RHU / TE configuration could be designed to survive an external 500°C bake out procedure for critical spacecraft sterilization, environmental certification and planetary protection. Analytical studies have been performed to optimize various design configurations for power, mass, volume and robotic mobility. Specific power (mW/kg) and volumetric specific power (mW/cm3) characteristics of various design configurations will be presented and key conceptual design tradeoffs will be discussed. Hot- and cold-side thermal interfaces required to meet power and mass goals and associated design sensitivities will also be discussed. RHU / TE systems must overcome critical design challenges to survive high-g loadings in some robotic applications and we will examine the mass impacts required to satisfy various dynamic loading environments up to 10,000 g’s. Power can be generated for a minimum of 30 years or more using plutonium-238 dioxide heat sources (given that Pu-238 has an 87.7 year half-life) with some reduction in power as the heat source naturally degrades.

Bahrami, Poyan↗

Ram ion scattering caused by Space Shuttle v x B induced differential charging

Observations of secondary, high-inclination ions streams have been reported in the literature. The authors of these previous papers attributed the source of the secondary ions to a disturbed region in the plasma about 10 m from the Space Shuttle Orbiter. A new theory has been developed which shows how v x B induced differential charging on the plasma diagnostics package (PDP) can scatter the ram ion flux. Some of these ions are reflected back to the PDP and may be the sorce of the observed ion distributions. The effect is unique to large spacecraft; it occurs only when the magnitude of the induced v x B potentials are much larger than the electron thermal energy and of the order of the ion ram energy. That the ion streams observed at large angles must have been reflected from the PDP surface is demonstrated with three-dimensional sheath and particle trajectory calculations using the low earth orbit version of the NASA Charging Analyzer Program (NASCAP/LEO).

Katz, I.↗

Implementation of Adaptive Digital Controllers on Programmable Logic Devices

Much has been made of the capabilities of FPGA's (Field Programmable Gate Arrays) in the hardware implementation of fast digital signal processing. Such capability also makes an FPGA a suitable platform for the digital implementation of closed loop controllers. Other researchers have implemented a variety of closed-loop digital controllers on FPGA's. Some of these controllers include the widely used proportional-integral-derivative (PID) controller, state space controllers, neural network and fuzzy logic based controllers. There are myriad advantages to utilizing an FPGA for discrete-time control functions which include the capability for reconfiguration when SRAM-based FPGA's are employed, fast parallel implementation of multiple control loops and implementations that can meet space level radiation tolerance requirements in a compact form-factor. Generally, a software implementation on a DSP (Digital Signal Processor) or microcontroller is used to implement digital controllers. At Marshall Space Flight Center, the Control Electronics Group has been studying adaptive discrete-time control of motor driven actuator systems using digital signal processor (DSP) devices. While small form factor, commercial DSP devices are now available with event capture, data conversion, pulse width modulated (PWM) outputs and communication peripherals, these devices are not currently available in designs and packages which meet space level radiation requirements. In general, very few DSP devices are produced that are designed to meet any level of radiation tolerance or hardness. The goal of this effort is to create a fully digital, flight ready controller design that utilizes an FPGA for implementation of signal conditioning for control feedback signals, generation of commands to the controlled system, and hardware insertion of adaptive control algorithm approaches. An alternative is required for compact implementation of such functionality to withstand the harsh environment encountered on spacecraft. Radiation tolerant FPGA's are a feasible option for reaching this goal.

Gwaltney, David A.↗

Differential Resonant Ring YIG Tuned Oscillator

A differential SiGe oscillator circuit uses a resonant ring-oscillator topology in order to electronically tune the oscillator over multi-octave bandwidths. The oscillator s tuning is extremely linear, because the oscillator s frequency depends on the magnetic tuning of a YIG sphere, whose resonant frequency is equal to a fundamental constant times the DC magnetic field. This extremely simple circuit topology uses two coupling loops connecting a differential pair of SiGe bipolar transistors into a feedback configuration using a YIG tuned filter creating a closed-loop ring oscillator. SiGe device technology is used for this oscillator in order to keep the transistor s 1/f noise to an absolute minimum in order to achieve minimum RF phase noise. The single-end resonant ring oscillator currently has an advantage in fewer parts, but when the oscillation frequency is greater than 16 GHz, the package s parasitic behavior couples energy to the sphere and causes holes and poor phase noise performance. This is because the coupling to the YIG is extremely low, so that the oscillator operates at near the unloaded Q. With the differential resonant ring oscillator, the oscillation currents are just in the YIG coupling mechanisms. The phase noise is even better, and the physical size can be reduced to permit monolithic microwave integrated circuit oscillators. This invention is a YIG tuned oscillator circuit making use of a differential topology to simultaneously achieve an extremely broadband electronic tuning range and ultra-low phase noise. As a natural result of its differential circuit topology, all reactive elements, such as tuning stubs, which limit tuning bandwidth by contributing excessive open loop phase shift, have been eliminated. The differential oscillator s open-loop phase shift is associated with completely non-dispersive circuit elements such as the physical angle of the coupling loops, a differential loop crossover, and the high-frequency phase shift of the n-p-n transistors. At the input of the oscillator s feedback loop is a pair of differentially connected n-p-n SiGe transistors that provides extremely high gain, and because they are bulk-effect devices, extremely low 1/f noise (leading to ultralow RF phase noise). The 1/f corner frequency for n-p-n SiGe transistors is approximately 500 Hz. The RF energy from the transistor s collector output is connected directly to the top-coupling loop (the excitation loop) of a single-sphere YIG tuned filter. A uniform magnetic field to bias the YIG must be at a right angle to any vector associated with an RF current in a coupling loop in order for the precession to interact with the RF currents.

Parrott, Ronald A.↗

Development of Thick-Film Thermoelectric Microcoolers Using Electrochemical Deposition

Advanced thermoelectric microdevices integrated into thermal management packages and low power, electrical source systems are of interest for a variety of space and terrestrial applications. By shrinking the size of the thermoelements, or legs, of these devices, it becomes possible to handle much higher heat fluxes, as well as operate at much lower currents and higher voltages that are more compatible with electronic components. The miniaturization of state-of-the-art thermoelectric module technology based on Bi2Te3 alloys is limited due to mechanical and manufacturing constraints for both leg dimensions (100-200 gm thick minimum) and the number of legs (100-200 legs maximum). We are investigating the development of novel microdevices combining high thermal conductivity substrate materials such as diamond, thin film metallization and patterning technology, and electrochemical deposition of thick thermoelectric films. It is anticipated that thermoelectric microcoolers with thousands of thermocouples and capable of pumping more than 200 W/sq cm over a 30 to 60 K temperature difference can be fabricated. In this paper, we report on our progress in developing an electrochemical deposition process for obtaining 10-50 microns thick films of Bi2Te3 and its solid solutions. Results presented here indicate that good quality n-type Bi2Te3, n-type Bi2Te(2.95)Se(0.05) and p-type Bi(0.5)Sb(1.5)Te3 thick films can be deposited by this technique. Some details about the fabrication of the miniature thermoelements are also described.

Fleurial, J.-P.↗

Different Approaches for Ensuring Performance/Reliability of Plastic Encapsulated Microcircuits (PEMs) in Space Applications

Engineers within the commercial and aerospace industries are using trade-off and risk analysis to aid in reducing spacecraft system cost while increasing performance and maintaining high reliability. In many cases, Commercial Off-The-Shelf (COTS) components, which include Plastic Encapsulated Microcircuits (PEMs), are candidate packaging technologies for spacecrafts due to their lower cost, lower weight and enhanced functionality. Establishing and implementing a parts program that effectively and reliably makes use of these potentially less reliable, but state-of-the-art devices, has become a significant portion of the job for the parts engineer. Assembling a reliable high performance electronic system, which includes COTS components, requires that the end user assume a risk. To minimize the risk involved, companies have developed methodologies by which they use accelerated stress testing to assess the product and reduce the risk involved to the total system. Currently, there are no industry standard procedures for accomplishing this risk mitigation. This paper will present the approaches for reducing the risk of using PEMs devices in space flight systems as developed by two independent Laboratories. The JPL procedure involves primarily a tailored screening with accelerated stress philosophy while the APL procedure is primarily, a lot qualification procedure. Both Laboratories successfully have reduced the risk of using the particular devices for their respective systems and mission requirements.

Gerke, R. David↗

RF Technologies for Advancing Space Communication Infrastructure

This paper will address key technologies under development at the NASA Glenn Research Center designed to provide architecture-level impacts. Specifically, we will describe deployable antennas, a new type of phased array antenna and novel power amplifiers. The evaluation of architectural influence can be conducted from two perspectives where said architecture can be analyzed from either the top-down to determine the areas where technology improvements will be most beneficial or from the bottom-up where each technology s performance advancement can affect the overall architecture s performance. This paper will take the latter approach with focus on some technology improvement challenges and address architecture impacts. For example, using data rate as a performance metric, future exploration scenarios are expected to demand data rates possibly exceeding 1 Gbps. To support these advancements in a Mars scenario, as an example, Ka-band and antenna aperture sizes on the order of 10 meters will be required from Mars areostationary platforms. Key technical challenges for a large deployable antenna include maximizing the ratio of deployed-to-packaged volume, minimizing aerial density, maintaining RMS surface accuracy to within 1/20 of a wavelength or better, and developing reflector rigidization techniques. Moreover, the high frequencies and large apertures manifest a new problem for microwave engineers that are familiar to optical communications specialists: pointing. The fine beam widths and long ranges dictate the need for electronic or mechanical feed articulation to compensate for spacecraft attitude control limitations.

Romanofsky, Robert R.↗

Incorporation of a circulating protein into megakaryocyte and platelet granules

To determine whether or not proteins circulating in plasma can be incorporated into megakaryocytes and platelets, horseradish peroxidase (HRP) was injected intravenously into guinea pigs and these cells were examined for its uptake by electron microscopy and cytochemistry. Enriched samples of megakaryocytes enabled ultrastructural analysis of large numbers of these rare cells. In megakaryocytes, 50% of alpha granules contained HRP between 75 min and 7 hr after injection. At 24 hr, 25% of the megakaryocyte granules were peroxidase-positive, less were positive by 48 hr, and there were none at 4 days. Thus, the findings demonstrate that a circulating protein can be endocytosed by megakaryocytes and rapidly packaged into alpha granules. Platelet granules also contain HRP by 7 hr after injection, and they can secrete it in response to thrombin. Unfortunately, our present studies do not allow us to distinguish between direct endocytosis by the platelet and/or shedding of new platelets from recently labeled megakaryocytes. It is concluded that while some alpha granule proteins are synthesized by megakaryocytes, others may be acquired from plasma by endocytosis. In addition to providing evidence that some of the proteins of alpha granules may be of exogenous origin, this study has allowed the definition of a pathway whereby plasma proteins may be temporarily sequestered in megakaryocytes before reentering the circulation in platelets.

Megakaryocytes/metabolism/ultrastructure↗

Status of the US Space Station ECLSS and internal TCS

The U.S. Space Station includes many elements and systems. Responsibility for these have been delegated to four NASA centers via a work packaging concept. Marshall Space Flight Center (MSFC) is responsible for work package one (WPOI) which includes the habitation, laboratory modules, the logistic carrier elements, as well as the environmental control and life support system (ECLSS), the internal thermal control system (ITCS), and the internal audio and video systems. Current status of the ECLSS and internal thermal are the subjects of this paper. The ECLSS is composed of six subsystem groups: the temperature humidity control, the atmosphere control and supply, the air revitalization, water reclamation and management, fecal waste management, and the fire detection and suppression subsystems. The internal TCS consists of all WP01 elements of passive and active thermal measures. The ECLSS and ITCS provide services for the permanently orbiting pressurized modules as well as the pressurized and unpressurized logistics carriers. The logistics carriers are used as ground-to-station ferries for both resupply and initial delivery of selected new equipment and later replacement items. Equipment, which cannot be subjected to the rigors of the space environment, will be carried in the pressurized logistic carrier; while an unpressurized carrier is used to resupply other commodities, such as external fluid consumables. The laboratory module houses the equipment for both payloads and subsystem maintenance and repair. The habitation module is dedicated to providing living and sleeping quarters including a galley, sleeping provisions, hygiene facilities, medical services as well as services for exercise and relaxation. The four nodes that join the two modules at their ends also house electronics as well as work stations and outside viewing cupolas. The airlocks, one providing an emergency hyperbaric chamber capability, are also attached. This assembly constitutes the U.S. provided portion of the initial station. Additional international modules and docking provisions for future attached pressurized payload as well as dual logistic module and growth capabilities are also provided. The primary heat rejection mechanism is achieved via a central set of radiators provided by another work package. The interface with the central TCS at the module heat exchangers defines the active control interface boundary of the ITCS with the central TCS. All internal cooling of the permanent orbital elements are provided via internal active fluid loops within the elements utilizing water as the transport media. Cabin and equipment cooling are provided by forced air flow and cold plate heat sinks. A special active cooling loop is provided in the laboratory module to accommodate experiments and other payloads. Coatings and insulation are used in conjunction with the active components to passively limit heat losses/gains. The most challenging ECLSS new technology issues relate to oxygen and water recovery. Closure of the oxygen loop requires the use of new regenerative CO 2 removal and concentration techniques, CO 2 reduction to convert the CO 2 to water with a waste by-product, and the electrolysis of water to produce breathing oxygen for water recovery. For water recovery three separate loops are currently planned. One loop provides potable water by utilizing a combination of recovered condensate and CO 2 reduction water. A second loop purifies hygiene water from waste from the showers, clothes washer, hygiene/hand wash stations and a dishwasher. The third loop provides hygiene water by the reclamation and purification of urine water. This paper outlines the basic services provided by the ECLSS and ITCS and describes the ECLSS functional distribution throughout the pressurized assembly.

R. Humphries↗