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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

The Fiber Optic System for the Advanced Topographic Laser Altimeter System (ATLAS) Instrument

The Advanced Topographic Laser Altimeter System (ATLAS) Instrument has been in integration and testing over the past 18 months in preparation for the Ice, Cloud and Land Elevation Satellite - 2 (ICESat-2) Mission, scheduled to launch in 2017. ICESat-2 is the follow on to ICESat which launched in 2003 and operated until 2009. ATLAS will measure the elevation of ice sheets, glaciers and sea ice or the "cryosphere" (as well as terrain) to provide data for assessing the earth's global climate changes. Where ICESat's instrument, the Geo-Science Laser Altimeter (GLAS) used a single beam measured with a 70 m spot on the ground and a distance between spots of 170 m, ATLAS will measure a spot size of 10 m with a spacing of 70 cm using six beams to measure terrain height changes as small as 4 mm. The ATLAS pulsed transmission system consists of two lasers operating at 532 nm with transmitter optics for beam steering, a diffractive optical element that splits the signal into 6 separate beams, receivers for start pulse detection and a wavelength tracking system. The optical receiver telescope system consists of optics that focus all six beams into optical fibers that feed a filter system that transmits the signal via fiber assemblies to the detectors. Also included on the instrument is a system that calibrates the alignment of the transmitted pulses to the receiver optics for precise signal capture. The larger electro optical subsystems for transmission, calibration, and signal receive, stay aligned and transmitting sufficiently due to the optical fiber system that links them together. The robust design of the fiber optic system, consisting of a variety of multi fiber arrays and simplex assemblies with multiple fiber core sizes and types, will enable the system to maintain consistent critical alignments for the entire life of the mission. Some of the development approaches used to meet the challenging optical system requirements for ATLAS are discussed here.

global climate changes↗
NASA NTRS1986

Gas dispersion measurements using a mobile Raman lidar system

The exploitation of natural gas resources to supply energy demands has resulted in the need to engineer pipelines and plants capable of handling extremely high pressures and throughputs. Consequently, more attention has been directed to evaluating the consequences of releases of material whether accidental or deliberate in nature. An important aspect of assessing the consequences of a release is an understanding of how gas disperses in the atmosphere over a wide range of release and atmospheric conditions. The most cost effective way of providing such information is through the development and use of reliable theoretical prediction methods. The need for some form of remote sensing device was identified. The various possibilities studied led to the conclusion that LIDAR (Light Detection And Ranging) offered the most suitable method. The system designed and built is described, and its recent use in monitoring operational ventings from a high pressure transmission system is discussed.

Houston, J. D.↗
NASA NTRS1961

Tiros Program Results

Tiros operational satellite system - tiros i and tiros ii - transmission of useful meteorological information

TIROS II SATELLITE↗
NASA NTRS1971

A real time programmable data compression system for video data.

Description of the implementation of a data compression system for the real-time operational transmission (through microwave links) of ATS satellite pictures between the command and data acquisition station and a central location for computer processing. The system features the use of general-purpose minicomputers for encoding and decoding; this makes it possible to vary the employed data compression technique and to make simultaneous statistical calculations on the data. Data compression and expansion is accomplished in a manner that does not lower data quality.

Kutz, R. L.↗
NASA NTRS1993

Antenna system providing a spherical radiation pattern

An antenna system provides a substantially spherical radiation pattern about a structure located above ground level, by locating the individual radiation pattern of each of a plurality of individual antennae, each positioned to have a radiation pattern covering only a portion of the desired sphere, and then applying all antenna signals, during either transmission or reception time intervals, through space-diversity and/or time-diversity apparatus, to cause the patterns of all of the antennae to combine into the desired substantially-spherical pattern. The antennae may have substantially hemispherical patterns, with each antenna of a pair thereof being directed in a direction generally opposite to the other antenna of that pair. Time domain multiple access (TDMA) operation of a master system station, with transmission in different time slots for different portions of the coverage sphere, and selection of the strongest received signal from among all of the plurality N of signals simultaneously received by the plurality N of antennae, can provide the desired spherical radiation pattern in both the transmission and reception modes of operation.

Sickles, II, Louis↗
NASA NTRS1975

The assembly of large structures in space

Techniques developed for orbital assembly of the support structure for a 1000 meter diameter microwave power transmission system antenna are described. The operation is performed in two phases using the shuttle remote manipulator system in low earth orbit, and a mobile assembler in geosynchronous orbit.

Smith, G. W.↗
NASA NTRS1986

Model analysis of remotely controlled rendezvous and docking with display prediction

Manual control of rendezvous and docking (RVD) of two spacecraft in low earth orbit by a remote human operator is discussed. Experimental evidence has shown that control performance degradation for large transmission delays (between spacecraft and operations control center) can be substantially improved by the introduction of predictor displays. An intial Optimal Control Model (OCM) analysis of RVD translational and rotational perturbation control was performed, with emphasis placed on the predictive capabilities of the combined Kalman estimator/optimal predictor with respect to control performance, for a range of time delays, motor noise levels and tracking axes. OCM predictions are then used as a reference for comparing tracking performance with a simple predictor display, as well as with no display prediction at all. Use is made here of an imperfect internal model formulation, whereby it is assumed that the human operator has no knowledge of the system transmission delay.

Milgram, P.↗
NASA NTRS1996

Features Of Cavity Flow And Acoustics Of Stratospheric Observatory For Infrared Astronomy

The stratospheric observatory for infrared astronomy (SOFIA) is a 2.5 meter aperture Cassegrain telescope with a Nasmyth focus that will be housed in an open cavity in the Boeing 747-SP aircraft and operated at altitudes around 41,000 feet for infrared (IR) viewing of celestial events of astronomical nature. At these altitudes the IR viewing capability of SOFIA far exceeds that of any ground based system. To minimize IR transmission losses, SOFIA will operate with an open cavity. Such an open cavity during flight creates several challenging aerodynamic and aeroacoustic design problems. Foremost of these are: the shear layer over the cavity may cause unwanted resonance if the cavity is untreated; this might give rise to excessive sound pressure levels (SPL) in the cavity and thus affect the unsteady loads on the telescope; the unsteady flow within the cavity produces large dynamic loads and moments that will impact the pointing accuracy of the telescope; the open cavity and the shear layer control devices produce additional drag that will affect directly the time of flight of the mission; the aft location of the cavity down stream of port wing will affect the the flow on the aircraft control surfaces and thus the stability of the aircraft. Also, the highly turbulent shear layer over the cavity and the temperature gradients and 'hot spots' within the cavity can produce a wave front error of the image when it reaches the focal plane of the recorder.

Srinivasan, G. R.↗
NASA NTRS1991

Issues concerning centralized versus decentralized power deployment

The results of a study of proposed lunar base architectures to identify issues concerning centralized and decentralized power system deployment options are presented. The power system consists of the energy producing system (power plant), the power conditioning components used to convert the generated power into the form desired for transmission, the transmission lines that conduct this power from the power sources to the loads, and the primary power conditioning hardware located at the user end. Three power system architectures, centralized, hybrid, and decentralized, were evaluated during the course of this study. Candidate power sources were characterized with respect to mass and radiator area. Two electrical models were created for each architecture to identify the preferred method of power transmission, dc or ac. Each model allowed the transmission voltage level to be varied at assess the impact on power system mass. The ac power system models also permitted the transmission line configurations and placements to determine the best conductor construction and installation location. Key parameters used to evaluate each configuration were power source and power conditioning component efficiencies, masses, and radiator areas; transmission line masses and operating temperatures; and total system mass.

Metcalf, Kenneth J.↗
NASA NTRS1983

Multibus-based parallel processor for simulation

A Multibus-based parallel processor simulation system is described. The system is intended to serve as a vehicle for gaining hands-on experience, testing system and application software, and evaluating parallel processor performance during development of a larger system based on the horizontal/vertical-bus interprocessor communication mechanism. The prototype system consists of up to seven Intel iSBC 86/12A single-board computers which serve as processing elements, a multiple transmission controller (MTC) designed to support system operation, and an Intel Model 225 Microcomputer Development System which serves as the user interface and input/output processor. All components are interconnected by a Multibus/IEEE 796 bus. An important characteristic of the system is that it provides a mechanism for a processing element to broadcast data to other selected processing elements. This parallel transfer capability is provided through the design of the MTC and a minor modification to the iSBC 86/12A board. The operation of the MTC, the basic hardware-level operation of the system, and pertinent details about the iSBC 86/12A and the Multibus are described.

Ogrady, E. P.↗
NASA NTRS1980

Satellite Power Systems /SPS/ - Overview of system studies and critical technology

Systems studies and critical technology issues for the development and evaluation of Satellite Power Systems (SPS) for the photovoltaic generation of electrical energy and its transmission to earth are reviewed. Initial concept studies completed in 1976 and system definition studies initiated in the same year have indicated the technical feasibility of SPS and identified challenging issues to be addressed as part of the SPS Concept Development and Evaluation Program. Systems considered in the study include photovoltaic and solar thermal power conversion configurations employing klystron or solid state microwave generators or lasers for power transmission, and power transmission options, system constructability and in-orbit and ground operations. Technology investigations are being performed in the areas of microwave power transmission, structure/controls interactions and the behavior of key materials in the space/SPS environment. Favorable results have been obtained in the areas of microwave phase distribution and phase control, dc-RF conversion, antenna radiating element, and no insurmountable problems have been discovered in any of the investigations to date.

Manson, S. V.↗
NASA NTRS1991

Precise time and time interval applications to electric power systems

There are many applications of precise time and time interval (frequency) in operating modern electric power systems. Many generators and customer loads are operated in parallel. The reliable transfer of electrical power to the consumer partly depends on measuring power system frequency consistently in many locations. The internal oscillators in the widely dispersed frequency measuring units must be syntonized. Elaborate protection and control systems guard the high voltage equipment from short and open circuits. For the highest reliability of electric service, engineers need to study all control system operations. Precise timekeeping networks aid in the analysis of power system operations by synchronizing the clocks on recording instruments. Utility engineers want to reproduce events that caused loss of service to customers. Precise timekeeping networks can synchronize protective relay test-sets. For dependable electrical service, all generators and large motors must remain close to speed synchronism. The stable response of a power system to perturbations is critical to continuity of electrical service. Research shows that measurement of the power system state vector can aid in the monitoring and control of system stability. If power system operators know that a lightning storm is approaching a critical transmission line or transformer, they can modify operating strategies. Knowledge of the location of a short circuit fault can speed the re-energizing of a transmission line. One fault location technique requires clocks synchronized to one microsecond. Current research seeks to find out if one microsecond timekeeping can aid and improve power system control and operation.

Robert E. Wilson↗
NASA NTRS1975

Radiated microwave power transmission system efficiency measurements

The measured and calculated results from determining the operating efficiencies of a laboratory version of a system for transporting electric power from one point to another via a wireless free space radiated microwave beam are reported. The system's overall end-to-end efficiency as well as intermediated conversion efficiencies were measured. The maximum achieved end-to-end dc-to-ac system efficiency was 54.18% with a probable error of + or - 0.94%. The dc-to-RF conversion efficiency was measured to be 68.87% + or - 1.0% and the RF-to-dc conversion efficiency was 78.67 + or - 1.1%. Under these conditions a dc power of 495.62 + or - 3.57 W was received with a free space transmitter antenna receiver antenna separation of 170.2 cm (67 in).

Dickinson, R. M.↗
NASA NTRS1994

Feasibility study of transmission of OTV camera control information in the video vertical blanking interval

The Operational Television system at Kennedy Space Center operates hundreds of video cameras, many remotely controllable, in support of the operations at the center. This study was undertaken to determine if commercial NABTS (North American Basic Teletext System) teletext transmission in the vertical blanking interval of the genlock signals distributed to the cameras could be used to send remote control commands to the cameras and the associated pan and tilt platforms. Wavelength division multiplexed fiberoptic links are being installed in the OTV system to obtain RS-250 short-haul quality. It was demonstrated that the NABTS transmission could be sent over the fiberoptic cable plant without excessive video quality degradation and that video cameras could be controlled using NABTS transmissions over multimode fiberoptic paths as long as 1.2 km.

White, Preston A., III↗
NASA NTRS1982

AMPA experimental communications systems

The program was conducted to demonstrate the satellite communication advantages of Adaptive Phased Array Technology. A laboratory based experiment was designed and implemented to demonstrate a low earth orbit satellite communications system. Using a 32 element, L-band phased array augmented with 4 sets of weights (2 for reception and 2 for transmission) a high speed digital processing system and operating against multiple user terminals and interferers, the AMPA system demonstrated: communications with austere user terminals, frequency reuse, communications in the face of interference, and geolocation. The program and experiment objectives are described, the system hardware and software/firmware are defined, and the test performed and the resultant test data are presented.

Beckerman, D.↗
NASA NTRS1993

On structuring the rules of a fuzzy controller

Since the pioneering work of Zadeh and Mamdani and Assilian, fuzzy logic control has emerged as one of the most active and fruitful research areas. The applications of fuzzy logic control can be found in many fields such as control of stream generators, automatic train operation systems, elevator control, nuclear reactor control, automobile transmission control, etc. In this paper, two new structures of hierarchical fuzzy rule-based controller are proposed to reduce the number of rules in a complete rule set of a controller. In one approach, the overall system is split into sub-systems which are treated independently in parallel. A coordinator is then used to take into account the interactions. This is done via an iterating information exchange between the lower level and the coordinator level. From the point of view of information used, this structure is very similar to central structure in that the coordinator can have at least in principle, all the information that the local controllers have.

Zhou, Jun↗
NASA NTRS2002

Low Resolution Picture Transmission (LRPT) Demonstration System

Low-Resolution Picture Transmission (LRPT) is a proposed standard for direct broadcast transmission of satellite weather images. This standard is a joint effort by the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) and the National Oceanic Atmospheric Administration (NOAA). As a digital transmission scheme, its purpose is to replace the current analog Automatic Picture Transmission (APT) system for use in the Meteorological Operational (METOP) satellites. Goddard Space Flight Center has been tasked to build an LRPT Demonstration System (LDS). It's main objective is to develop or demonstrate the feasibility of a low-cost receiver utilizing a Personal Computer (PC) as the primary processing component and determine the performance of the protocol in the simulated Radio Frequency (RF) environment. The approach would consist of two phases. In the phase 1, a Commercial-off-the-Shelf (COTS) Modulator-Demodulator (MODEM) board that would perform RF demodulation would be purchased allowing the Central Processing Unit (CPU) to perform the Consultative Committee for Space Data Systems (CCSDS) protocol processing. Also since the weather images are compressed the PC would perform the decompression. Phase 1 was successfully demonstrated on December 1997. Phase 2 consists of developing a high-fidelity receiver, transmitter and environment simulator. Its goal is to find out how the METOP Specification performs in a simulated noise environment in a cost-effective receiver. The approach would be to produce a receiver using as much software as possible to perform front-end processing to take advantage of the latest high-speed PCs. Thus the COTS MODEM used in Phase 1 is performing RF demodulation along with data acquisition providing data to the receiving software. Also, environment simulator is produced using the noise patterns generated by Institute for Telecommunications Sciences (ITS) from their noise environment study.

Fong, Wai↗