Frequency generation and control - Comparison of frequency synthesizers
Phase noise power spectral density, phase noise variance with time, and phase noise amplitude distribution for frequency synthesizers
NOISE MEASUREMENT↗
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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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Light-Emitting Diodes (LED) for Primary Animal Habitat Lighting in Highly Controlled Environments
Significant alterations in Biological Clock responses have been reported following sidereal time changes (e.g., Jet-lag), and exposure to microgravity (e.g., daytime sleepiness). Additionally, light reduces circulating melatonin (spectral specificity greatest between 450-500 nm). It was hypothesized that LEDs can replace the current light sources used in zero gravity and terrestrial research laboratories because of their small size, low mass, low energy consumption and long functional life. This report evaluates the capacity of LEDs to entrain the circadian system of rats as judged by measurement of overt behavioral circadian rhythms (activity, feeding, drinking). These data were collected in highly controlled environments similar to the shuttle Animal Enclosure Modules. Two groups were compared: control - animals exposed to standard cool-white fluorescent lights, and test - animals exposed to LEDs with a spectral power distribution matching the fluorescent lights. Gross locomotor activity, feeding and drinking frequencies were continuously monitored and stored at 10 minute intervals. Animals were exposed to the following photoperiods: 28 days of 12L:12D, 19 days of 24L:0D and 16 days of 12L:12D. Light intensities tested varied between 0.1 to 100 lux. Rats received food and water ad libitum, and temperature and humidity were controlled throughout the study. The general health status of all rats was acceptable for each day of this study. No incidents of aggressive behavior were observed. Growth, locomotor activity, food and water consumption were comparable for all groups of animals, i.e, the circadian characteristics of the animals under these conditions were comparable. These results indicate that LED arrays are as effective in maintaining circadian rhythm stability as the commonly used cool-white fluorescent light sources. LEDs with their flexible spectrum, low energy requirements and minimal heat production have advantages for some chronopharmacology studies and for microgravity animal habitats.
Winget, C. M.↗
Space tug point design study. Volume 1: Summary
The design and characteristics of a space tug are discussed. The primary objective of the study is to verify the performance capability of a baseline design to deliver and retrieve payloads between 100 nautical miles, 28.5 degrees inclination, and geosynchronous. The space tug is ground based, reusable for 20 mission cycles, and is shuttled to and from low earth orbit by an earth orbital shuttle (EOS) with a 65,000 pound payload capability. It is shown that the baseline concept can meet the target performance goals. The design analysis encompassed: (1) definition of the vehicle primary structure, (2) thermal control, (3) meteoroid protection, (4) propulsion and mechanical subsystems, and (5) avionics including power generation and distribution.
Source record↗
Studies of advanced transport aircraft
Several concepts for possible future airplanes, including all-wing distributed-load airplanes, multibody airplanes, a long-range laminar flow control airplane, a nuclear-powered airplane designed for towing conventionally powered airplanes during long-range cruise, and an aerial transportation system comprised of continuously flying liner airplanes operated in conjunction with short-range feeder airplanes are described. Performance and economic advantages of each concept are indicated. Further research is recommended in the following areas: all-wing airplane aerodynamics, aerial rendezvous, nuclear aircraft engines, air-cushion landing systems, and laminar flow control, as well as the basic research discipline areas of aerodynamics, structures, propulsion, avionics, and computer applications.
Nagel, A. L.↗
Space Transportation System/Spacelab accommodations
A description is provided of the capabilities offered by the Spacelab design for doing research in space. The Spacelab flight vehicle consists of two basic elements including the habitable pressurized compartments and the unpressurized equipment mounting platforms. Spacelab services to payloads are considered, taking into account payload mass, electrical power and energy, heat rejection for Spacelab and payload, aspects of Spacelab data handling, and the extended flight capability. Attention is also given to the Spacelab structure, crew station and habitability, the electrical power distribution subsystem, the command and data management subsystem, the experiment computer operating system, the environmental control subsystem, the experiment vent assembly, the common payload support equipment, the instrument pointing subsystem, and details concerning the utilization of Spacelab.
De Sanctis, C. E.↗
Advances in solid state switchgear technology for large space power systems
High voltage solid state remote power controllers (RPC's) and the required semiconductor power switches to provide baseline technology for large, high power distribution systems in the space station, all electric airplane and other advanced aerospace applications were developed. The RPC's were developed for dc voltages from 28 to 1200 V and ac voltages of 115, 230, and 440 V at frequencies of 400 Hz to 20 kHz. The benefits and operation of solid state RPC's and highlights of several developments to bring the RPC to technology readiness for future aerospace needs are examined. The 28 V dc Space Shuttle units, three RPC types at 120 V dc, two at 270/300 V dc, two at 230 V ac and several high power RPC models at voltages up to 1200 V dc with current ratings up to 100 A are reviewed. New technology programs to develop a new family of (DI)2 semiconductor switches and 20 kHz, 440 V ac RPC's are described.
Sundberg, G. R.↗
Advanced in solid state switchgear technology for large space power systems
High voltage solid state remote power controllers (RPC's) and the required semiconductor power switches to provide baseline technology for large, high power distribution systems in the Space Station, all electric airplane and other advanced aerospace applications were developed. The RPC's were developed for dc voltages from 28 to 1200 V and ac voltages of 115, 230, and 440 V at frequencies of 400 Hz to 20 kHz. The benefits and operation of solid state RPC's and highlights of several developments to bring the RPC to technology readiness for future aerospace needs are examined. The 28 V dc Space Shuttle units, three RPC types at 120 V dc, two at 270/300 V dc, two at 230 V ac and several high power RPC models at voltages up to 1200 V dc with current ratings up to 100 A are reviewed. New technology programs to develop a new family of (DI)2 semiconductor switches and 20 kHz, 440 V ac RPC's are described.
Sundberg, G. R.↗
Human factors in space station architecture 1: Space station program implications for human factors research
The space station program is based on a set of premises on mission requirements and the operational capabilities of the space shuttle. These premises will influence the human behavioral factors and conditions on board the space station. These include: launch in the STS Orbiter payload bay, orbital characteristics, power supply, microgravity environment, autonomy from the ground, crew make-up and organization, distributed command control, safety, and logistics resupply. The most immediate design impacts of these premises will be upon the architectural organization and internal environment of the space station.
Cohen, M. M.↗
Intermediate Levels of Autonomy within the SSM/PMAD Breadboard
The Space Station Module Power Management and Distribution (SSM/PMAD) bread-board is a test bed for the development of advanced power system control and automation. Software control in the SSM/PMAD breadboard is through co-operating systems, called Autonomous Agents. Agents can be a mixture of algorithmic software and expert systems. The early SSM/PMAD system was envisioned as being completely autonomous. It soon became apparent, though, that there would always be a need for human intervention, at least as long as a human interacts with the system in any way. In a system designed only for autonomous operation, manual intervention meant taking full control of the whole system, and loosing whatever expertise was in the system. Several methods for allowing humans to interact at an appropriate level of control were developed. This paper examines some of these intermediate modes of autonomy. The least humanly intrusive mode is simple monitoring. The ability to modify future behavior by altering a schedule involves high-level interaction. Modification of operating activities comes next. The coarsest mode of control is individual, unplanned operation of individual Power System components. Each of these levels is integrated into the SSM/PMAD breadboard, with support for the user (such as warnings of the consequences of control decisions) at every level.
Dugal-Whitehead, Norma R.↗
The impact of circulation control on rotary aircraft controls systems
Application of circulation to rotary wing systems is a new development. Efforts to determine the near and far field flow patterns and to analytically predict those flow patterns have been underway for some years. Rotary wing applications present a new set of challenges in circulation control technology. Rotary wing sections must accommodate substantial Mach number, free stream dynamic pressure and section angle of attack variation at each flight condition within the design envelope. They must also be capable of short term circulation blowing modulation to produce control moments and vibration alleviation in addition to a lift augmentation function. Control system design must provide this primary control moment, vibration alleviation and lift augmentation function. To accomplish this, one must simultaneously control the compressed air source and its distribution. The control law algorithm must therefore address the compressor as the air source, the plenum as the air pressure storage and the pneumatic flow gates or valves that distribute and meter the stored pressure to the rotating blades. Also, mechanical collective blade pitch, rotor shaft angle of attack and engine power control must be maintained.
Kingloff, R. F.↗
Design and fabrication of a photovoltaic power system for the Papago Indian village of Schuchuli (Gunsight), Arizona
A stand alone photovoltaic power system for installation in the Papago Indian village of Schuchuli is being designed and fabricated to provide electricity for village water pumping and basic domestic needs. The system will consist of a 3.5 kW (peak) photovoltaic array; controls, instrumentations, and storage batteries located in an electrical equipment building and a 120 volt dc village distribution network. The system will power a 2 HP dc electric motor.
Bifano, W. J.↗
Design and breadboard evaluation of the SPS reference phase control system concept
The total breadboard system includes one pilot transmitter, one pilot receiver, nine phase distribution units, and two power transponders. With this complement of equipment, segments of a typical phase distribution system can be assembled to facilitate the evaluation of significant system parameters. The achievable accuracy of a large phase distribution system, the sensitivity of the system to parameter variations, and the limitations of commercially available components in such applications were determined.
Hopkins, P. M.↗
Coherent Frequency Reference System for the NASA Deep Space Network
The NASA Deep Space Network (DSN) requires state-of-the-art frequency references that are derived and distributed from very stable atomic frequency standards. A new Frequency Reference System (FRS) and Frequency Reference Distribution System (FRD) have been developed, which together replace the previous Coherent Reference Generator System (CRG). The FRS and FRD each provide new capabilities that significantly improve operability and reliability. The FRS allows for selection and switching between frequency standards, a flywheel capability (to avoid interruptions when switching frequency standards), and a frequency synthesis system (to generate standardized 5-, 10-, and 100-MHz reference signals). The FRS is powered by redundant, specially filtered, and sustainable power systems and includes a monitor and control capability for station operations to interact and control the frequency-standard selection process. The FRD receives the standardized 5-, 10-, and 100-MHz reference signals and distributes signals to distribution amplifiers in a fan out fashion to dozens of DSN users that require the highly stable reference signals. The FRD is also powered by redundant, specially filtered, and sustainable power systems. The new DSN Frequency Distribution System, which consists of the FRS and FRD systems described here, is central to all operational activities of the NASA DSN. The frequency generation and distribution system provides ultra-stable, coherent, and very low phase-noise references at 5, l0, and 100 MHz to between 60 and 100 separate users at each Deep Space Communications Complex.
Tucker, Blake C.↗
180-GHz Interferometric Imager
A 180-GHz interferometric imager uses compact receiver modules, combined high- and low-gain antennas, and ASIC (application specific integrated circuit) correlator technology, enabling continuous, all-weather observations of water vapor with 25-km resolution and 0.3-K noise in 15 minutes of observation for numerical weather forecasting and tropical storm prediction. The GeoSTAR-II prototype instrument is broken down into four major subsystems: the compact, low-noise receivers; sub-array modules; IF signal distribution; and the digitizer/correlator. Instead of the single row of antennas adopted in GeoSTAR, this version has four rows of antennas on a coarser grid. This dramatically improves the sensitivity in the desired field of view. The GeoSTAR-II instrument is a 48-element, synthetic, thinned aperture radiometer operating at 165-183 GHz. The instrument has compact receivers integrated into tiles of 16 elements in a 4x4 arrangement. These tiles become the building block of larger arrays. The tiles contain signal distribution for bias controls, IF signal, and local oscillator signals. The IF signals are digitized and correlated using an ASIC correlator to minimize power consumption. Previous synthetic aperture imagers have used comparatively large multichip modules, whereas this approach uses chip-scale modules mounted on circuit boards, which are in turn mounted on the distribution manifolds. This minimizes the number of connectors and reduces system mass. The use of ASIC technology in the digitizers and correlators leads to a power reduction close to an order of magnitude.
Kangaslahti, Pekka P.↗
Monitoring and control requirement definition study for Dispersed Storage and Generation (DSG). Volume 4, appendix C: Identification from utility visits of present and future approaches to integration of DSG into distribution networks
Visits to four utilities concerned with the use of DSG power sources on their distribution networks yielded useful impressions of present and future approaches to the integration of DSGs into electrical distribution network. Different approaches to future utility systems with DSG are beginning to take shape. The new DSG sources will be in decentralized locations with some measure of centralized control. The utilities have yet to establish firmly the communication and control means or their organization. For the present, the means for integrating the DSGs and their associated monitoring and control equipment into a unified system have not been decided.
Source record↗
Power system monitoring and source control of the Space Station Freedom DC power system testbed
Unlike a terrestrial electric utility which can purchase power from a neighboring utility, the Space Station Freedom (SSF) has strictly limited energy resources; as a result, source control, system monitoring, system protection, and load management are essential to the safe and efficient operation of the SSF Electric Power System (EPS). These functions are being evaluated in the DC Power Management and Distribution (PMAD) Testbed which NASA LeRC has developed at the Power System Facility (PSF) located in Cleveland, Ohio. The testbed is an ideal platform to develop, integrate, and verify power system monitoring and control algorithms. State Estimation (SE) is a monitoring tool used extensively in terrestrial electric utilities to ensure safe power system operation. It uses redundant system information to calculate the actual state of the EPS, to isolate faulty sensors, to determine source operating points, to verify faults detected by subsidiary controllers, and to identify high impedance faults. Source control and monitoring safeguard the power generation and storage subsystems and ensure that the power system operates within safe limits while satisfying user demands with minimal interruptions. System monitoring functions, in coordination with hardware implemented schemes, provide for a complete fault protection system. The objective of this paper is to overview the development and integration of the state estimator and the source control algorithms.
Kimnach, Greg L.↗
Power system monitoring and source control of the Space Station Freedom dc-power system testbed
Unlike a terrestrial electric utility which can purchase power from a neighboring utility, the Space Station Freedom (SSF) has strictly limited energy resources; as a result, source control, system monitoring, system protection, and load management are essential to the safe and efficient operation of the SSF Electric Power System (EPS). These functions are being evaluated in the dc Power Management and Distribution (PMAD) Testbed which NASA LeRC has developed at the Power System Facility (PSF) located in Cleveland, Ohio. The testbed is an ideal platform to develop, integrate, and verify power system monitoring and control algorithms. State Estimation (SE) is a monitoring tool used extensively in terrestrial electric utilities to ensure safe power system operation. It uses redundant system information to calculate the actual state of the EPS, to isolate faulty sensors, to determine source operating points, to verify faults detected by subsidiary controllers, and to identify high impedance faults. Source control and monitoring safeguard the power generation and storage subsystems and ensure that the power system operates within safe limits while satisfying user demands with minimal interruptions. System monitoring functions, in coordination with hardware implemented schemes, provide for a complete fault protection system. The objective of this paper is to overview the development and integration of the state estimator and the source control algorithms.
Kimnach, Greg L.↗
Studies of advanced transport aircraft
Concepts for possible future airplanes are studied that include all-wing distributed-load airplanes, multi-body airplanes, a long-range laminar flow control airplane, a nuclear powered airplane designed for towing conventionally powered airplanes during long range cruise, and an aerial transportation system comprised of continuously flying liner airplanes operated in conjunction with short range feeder airplanes. Results indicate that each of these concepts has the potential for important performance and economic advantages, provided certain suggested research tasks are successfully accomplished. Indicated research areas include all-wing airplane aerodynamics, aerial rendezvous, nuclear aircraft engines, air-cushion landing systems, and laminar flow control, as well as the basic research discipline areas of aerodynamics, structures, propulsion, avionics, and computer applications.
Nagel, A. L.↗