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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Low cost Ku-band earth terminals for voice/data/facsimile

A Ku-band satellite earth terminal capable of providing two way voice/facsimile teleconferencing, 128 Kbps data, telephone, and high-speed imagery services is proposed. Optimized terminal cost and configuration are presented as a function of FDMA and TDMA approaches to multiple access. The entire terminal from the antenna to microphones, speakers and facsimile equipment is considered. Component cost versus performance has been projected as a function of size of the procurement and predicted hardware innovations and production techniques through 1985. The lowest cost combinations of components has been determined in a computer optimization algorithm. The system requirements including terminal EIRP and G/T, satellite size, power per spacecraft transponder, satellite antenna characteristics, and link propagation outage were selected using a computerized system cost/performance optimization algorithm. System cost and terminal cost and performance requirements are presented as a function of the size of a nationwide U.S. network. Service costs are compared with typical conference travel costs to show the viability of the proposed terminal.

Kelley, R. L.↗
NASA NTRS1984

Modular approach for satellite communication ground terminals

The trend in satellite communications is toward completely digital, time division multiple access (TDMA) systems with uplink and downlink data rates dictated by the type of service offered. Trunking terminals will operate in the 550 MBPS (megabit per second) region uplink and downlink, whereas customer premise service (CPS) terminals will operate in the 25 to 10 MBPS region uplink and in the 200 MBPS region downlink. Additional criteria for the ground terminals will be to maintain clock sychronization with the system and burst time integrity to within a matter of nanoseconds, to process required order-fire information, to provide adaptive data scrambing, and to compensate for variations in the user input output data rates, and for changes in range in the satellite communications links resulting from satellite perturbations in orbit. To achieve the required adaptability of a ground terminal to the above mentioned variables, programmable building blocks can be developed that will meet all of these requirements. To maintain system synchronization, i.e., all bursted data arriving at the satellite within assigned TDMA windows, ground terminal transmit data rates and burst timing must be maintained within tight tolerances. With a programmable synchronizer as the heart of the terminal timing generation, variable data rates and burst timing tolerances are achievable. In essence, the unit inputs microprocessor generated timing words and outputs discrete timing pulses.

Gould, G. R.↗
NASA NTRS1991

Graphics Software For VT Terminals

VTGRAPH graphics software tool for DEC/VT computer terminal or terminals compatible with it, widely used by government and industry. Callable in FORTRAN or C language, library program enabling user to cope with many computer environments in which VT terminals used for window management and graphic systems. Provides PLOT10-like package plus color or shade capability for VT240, VT241, and VT300 terminals. User can easily design more-friendly user-interface programs and design PLOT10 programs on VT terminals with different computer systems. Requires ReGis graphics set terminal and FORTRAN compiler.

Wang, Caroline↗
NASA NTRS1993

Solar wind conditions in the outer heliosphere and the distance to the termination shock

The Plasma Science experiment on the Voyager 2 spacecraft has measured the properties of solar wind protons from 1 to 40.4 AU. We use these observations to discuss the probable location and motion of the termination shock of the solar wind. Assuming that the interstellar pressure is due to a 5 micro-G magnetic field draped over the upstream face of the heliopause, the radial variation of ram pressure implies that the termination shock will be located at an average distance near 89 AU. This distance scales inversely as the assumed field strength. There are also large variations in ram pressure on time scales of tens of days, due primarily to large variations in solar wind density at a given radius. Such rapid changes in the solar wind ram pressure can cause large perturbations in the location of the termination shock. We study the nonequilibrium location of the termination shock as it responds to these ram pressure changes. The results of this study suggest that the position of the termination shock can vary by as much as 10 AU in a single year, depending on the nature of variations in the ram pressure, and that multiple crossings of the termination shock by a given outer heliosphere spacecraft are likely. After the first crossing, such models of shock motion will be useful for predicting the timing of subsequent crossings.

Belcher, John W.↗
NASA NTRS1994

Evaluation of the fuselage lap joint fatigue and terminating action repair

Terminating action is a remedial repair which entails the replacement of shear head countersunk rivets with universal head rivets which have a larger shank diameter. The procedure was developed to eliminate the risk of widespread fatigue damage (WFD) in the upper rivet row of a fuselage lap joint. A test and evaluation program has been conducted by Foster-Miller, Inc. (FMI) to evaluate the terminating action repair of the upper rivet row of a commercial aircraft fuselage lap splice. Two full scale fatigue tests were conducted on fuselage panels using the growth of fatigue cracks in the lap joint. The second test was performed to evaluate the effectiveness of the terminating action repair. In both tests, cyclic pressurization loading was applied to the panels while crack propagation was recorded at all rivet locations at regular intervals to generate detailed data on conditions of fatigue crack initiation, ligament link-up, and fuselage fracture. This program demonstrated that the terminating action repair substantially increases the fatigue life of a fuselage panel structure and effectively eliminates the occurrence of cracking in the upper rivet row of the lap joint. While high cycle crack growth was recorded in the middle rivet row during the second test, failure was not imminent when the test was terminated after cycling to well beyond the service life. The program also demonstrated that the initiation, propagation, and linkup of WFD in full-scale fuselage structures can be simulated and quantitatively studied in the laboratory. This paper presents an overview of the testing program and provides a detailed discussion of the data analysis and results. Crack distribution and propagation rates and directions as well as frequency of cracking are presented for both tests. The progression of damage to linkup of adjacent cracks and to eventual overall panel failure is discussed. In addition, an assessment of the effectiveness of the terminating action repair and the occurrence of cracking in the middle rivet row is provided, and conclusions of practical interest are drawn.

Samavedam, Gopal↗
NASA NTRS1994

Motion of the heliospheric termination shock 3: Incident interplanetary shocks

In this paper the response of the heliospheric termination shock to an incident interplanetary shock is examined. This paper is an extension of a recent study by Barnes (1993), which treated the analogous problem for an incident contact discontinuity. The termination shock is treated as a strong gas-dynamic shock. The post-interaction configuration consists of a moving termination shock, a postshock contact discontinuity, and either a shock or rarefaction wave propagating the disturbance signal into the downstream medium. For a decrease in dynamic pressure a rarefaction wave propagates downstream, and the new termination shock propagates inward, while, for an enhancement of dynamic pressure, the termination shock moves outwards and a weak outer shock propagates into the downstream medium; speeds of motion of the termination shock are typically of the order of approximately 100 km/s. The results are similar to those presented by Barnes (1993) indicating that the results of that paper are robust within the gas-dynamic model, in the sense of being independent of the details of the initial disturbance.

Naidu, Kamcilla↗
NASA NTRS1995

Locations of termination shock and heliopause based on Voyager plasma and magnetic field data

The locations of the termination shock and the heliopause are studied taking into account the effects of pickup protons. The study uses available plasma and magnetic field data from Voyagers over a 14-year period (1978-1991) and Voyager observation of the 1992-93 radio emission event. Outside 30 AU, pickup protons have a significant influence on dynamical structures of the outer heliosphere. The solar wind is treated as a mixture of electrons, solar wind protons, and interstellar pickup protons. If the magnitude of the interstellar magnetic field B(sub int) is given, one can quantitatively study the motion and location of the termination shock. The location is anti-correlated with the sun spot number and the shock has an average speed of approx. 24 km/s. Because B(sub int) is poorly known, additional information is needed in studying the termination shock. Cummings, et al. have used observations of anomalous cosmic rays to estimate the location of the shock. The observations of the 1991 GMIR and GMIR shock and the 1992-93 radio emission event provide another handle for the study of the termination shock and the heliopause. After its penetration through the termination shock, the GMIR shock continued to propagate in the subsonic region of the solar wind and eventually interacted with the heliopause. This interaction produces a transmitted shock propagating outward in the interstellar medium and a reflected shock propagating inward toward the sun in the subsonic solar wind. The plasma frequencies behind the reflected and the transmitted shock can be, respectively, responsible for the 2- and 3-kHz radio emissions. Taking into account the effects of pickup protons we found that the average locations of the termination shock and the heliopause in 1991-92 are at approximately 66 AU and 150 AU, respectively.

Whang, Y. C.↗
NASA NTRS1995

Global aspects of the motion of the heliospheric termination shock: A gasdynamic model

The heliospheric termination shock is expected to move in response to variation in upstream solar wind conditions. Using numerical techniques, we extend an earlier strictly one-dimensional analytic gas dynamic model of shock motion to two dimensions, to investigate the qualitative features of global behavior of shock motion, and the consequences of latitudinal variation in dynamic pressure. The boundary conditions of the calculation are given by the solar wind parameters as a function of latitude and time on an inner spherical boundary, and a constant pressure (roughly simulating the effect of the local interstellar medium) on an outer boundary. Density variations, specified at the inner boundary as a function of time, are convected into the termination shock. Immediately after the interaction, the shock moves with speeds given by the earlier analytic model. However, as the termination shock propagates outward (or inward), it begins to slow down. After about 2 to 10 years, depending on details of boundary conditions, the signal from the shock interaction has reached the outer boundary and propagates inward to the position of the termination shock, strongly affecting the behavior of the shock. Assuming no further disturbances in the solar wind, the termination shock will reach its new equilibrium after some tens of years. In reality, large-scale variations in solar wind dynamic pressure occur on time scales short in comparison with the eleven year solar cycle, so that one expects that the termination shock is never in an equilibrium position, but rather oscillates inward and outward; this oscillation will vary with heliographic latitude. The effects of a variety of types of solar wind disturbances are investigated and summarized.

Ratkiewicz, R.↗
NASA NTRS1995

ACTS broadband aeronautical terminal

This paper discusses the design of, and experiments with, the ACTS Broadband Aeronautical Terminal. As part of the ongoing effort to investigate commercial applications of ACTS technologies, NASA's Jet Propulsion Laboratory and various industry/government partners are developing a broadband mobile terminal for aeronautical applications. The ACTS Broadband Aeronautical Terminal is designed to explore the use of K/Ka-band for high data rate aeronautical satellite communications. Currently available commercial aeronautical satellite communications systems are only capable of achieving data rates on the order of tens of kilobits per second. The broadband terminal used in conjunction with the ACTS mechanically steerable antenna, can achieve data rates of 384 kilobits per second, while use of an ACTS spot beam antenna with this terminal will allow up to T1 data rates (1.544 megabits per second). The aeronautical terminal will be utilized to test a variety of applications that require a high data rate communications link. The use of the K/Ka-band for wideband aeronautical communications has the advantages of spectrum availability and smaller antennas, while eliminating the one major drawback of this frequency band, rain attenuation, by flying above the clouds the majority of the time.

Agan, M. J.↗
NASA NTRS1996

Novel Afferent Terminal Structure in the Crista Ampullaris of the Goldfish, Carassius auratus

Using transmission electron microscopy, we have identified a new type of afferent terminal structure in the crista ampullaris of the goldfish Carassius auratus. In addition to the bouton-type afferent terminals previously described in the ear of this species, the crista also contained enlarged afferent terminals that enveloped a portion of the basolateral hair cell membrane. The hair cell membrane was evaginated and protruded into the afferent terminal in a glove-and-finger configuration. The membranes of the two cells were regularly aligned in the protruded region of the contact and had a distinct symmetrical electron density. The electron-dense profiles of these contacts were easily identified and were present in every crista sampled. In some cases, efferent terminals synapsed onto the afferents at a point where the hair cell protruded into the terminal. The ultrastructural similarities of the goldfish crista afferents to calyx afferents found in amniotes (birds, reptiles, and mammals) are discussed. The results of the study support the hypothesis that structural variation in the vertebrate inner ear may have evolved much earlier in evolution than previously supposed.

Lanford, Pamela J.↗
NASA NTRS1997

Ultra Small Aperture Terminal for Ka-Band SATCOM

An ultra small aperture terminal (USAT) at Ka-band frequency has been developed by Lewis Research Center (LeRC) for data rates up to 1.5 Mbps in the transmit mode and 40 Mbps in receive mode. The terminal consists of a 35 cm diameter offset-fed parabolic antenna which is attached to a solid state power amplifier and low noise amplifier. A single down converter is used to convert the Ka-band frequency to 70 MHz intermediate frequency (IF). A variable rate (9.6 Kbps to 10 Mbps) commercial modem with a standard RS-449/RS-232 interface is used to provide point-to-point digital services. The terminal has been demonstrated numerous times using the Advanced Communications Technology Satellite (ACTS) and the 4.5 in Link Evaluation Terminal (LET) in Cleveland. A conceptual design for an advanced terminal has also been developed. This advanced USAT utilizes Microwave Monolithic Integrated Circuit (MMIC) and flat plate array technologies. This terminal will be self contained in a single package which will include a 1 watt solid state amplifier (SSPA), low noise amplifier (LNA) and a modem card located behind the aperture of the array. The advanced USAT will be light weight, transportable, low cost and easy to point to the satellite. This paper will introduce designs for the reflector based and array based USAT's.

Acosta, Roberto↗
NASA NTRS1997

Light microscopic image analysis system to quantify immunoreactive terminal area apposed to nerve cells

The present report describes a desktop computer-based method for the quantitative assessment of the area occupied by immunoreactive terminals in close apposition to nerve cells in relation to the perimeter of the cell soma. This method is based on Fast Fourier Transform (FFT) routines incorporated in NIH-Image public domain software. Pyramidal cells of layer V of the somatosensory cortex outlined by GABA immunolabeled terminals were chosen for our analysis. A Leitz Diaplan light microscope was employed for the visualization of the sections. A Sierra Scientific Model 4030 CCD camera was used to capture the images into a Macintosh Centris 650 computer. After preprocessing, filtering was performed on the power spectrum in the frequency domain produced by the FFT operation. An inverse FFT with filter procedure was employed to restore the images to the spatial domain. Pasting of the original image to the transformed one using a Boolean logic operation called 'AND'ing produced an image with the terminals enhanced. This procedure allowed the creation of a binary image using a well-defined threshold of 128. Thus, the terminal area appears in black against a white background. This methodology provides an objective means of measurement of area by counting the total number of pixels occupied by immunoreactive terminals in light microscopic sections in which the difficulties of labeling intensity, size, shape and numerical density of terminals are avoided.

Non-NASA Center↗
NASA NTRS1993

The C-terminal region of alpha-crystallin: involvement in protection against heat-induced denaturation

Recent studies have demonstrated that the alpha-crystallins can protect other proteins against heat-induced denaturation and aggregation. To determine the possible involvement of the C-terminal region in this activity, the alpha-crystallins were subjected to limited tryptic digestion, and the amount of cleavage from the N-terminal and C-terminal regions of the alpha-A and alpha-B crystallin chains was assessed using antisera specific for these regions. Limited tryptic digestion resulted in cleavage only from the C-terminal region of alpha-A crystallin. This trypsin-treated alpha-A crystallin preparation showed a decreased ability to protect proteins from heat-induced aggregation using an in vitro assay. Together, these results demonstrate that the C-terminal region of alpha-A crystallin is important for its ability to protect against heat-induced aggregation, which is consistent with the hypothesis that post-translational changes that are known to occur at the C-terminal region may have significant effects on the ability of alpha-A crystallin to protect against protein denaturation in vivo.

NASA Discipline Cell Biology↗
NASA NTRS2013

Evaluation of the Terminal Area Precision Scheduling and Spacing System for Performance-Based Navigation Arrivals

The growth of global demand for air transportation has put increasing strain on the nation's air traffic management system. To relieve this strain, the International Civil Aviation Organization has urged all nations to adopt Performance-Based Navigation (PBN), which can help to reduce air traffic congestion, decrease aviation fuel consumption, and protect the environment. NASA has developed a Terminal Area Precision Scheduling and Spacing (TAPSS) system that can support increased use of PBN during periods of high traffic, while supporting fuel-efficient, continuous descent approaches. In the original development of this system, arrival aircraft are assigned fuel-efficient Area Navigation (RNAV) Standard Terminal Arrival Routes before their initial descent from cruise, with routing defined to a specific runway. The system also determines precise schedules for these aircraft that facilitate continuous descent through the assigned routes. To meet these schedules, controllers are given a set of advisory tools to precisely control aircraft. The TAPSS system has been evaluated in a series of human-in-the-loop (HITL) air traffic simulations during 2010 and 2011. Results indicated increased airport arrival throughput up to 10 over current operations, and maintained fuel-efficient aircraft decent profiles from the initial descent to landing with reduced controller workload. This paper focuses on results from a joint NASA and FAA HITL simulation conducted in 2012. Due to the FAA rollout of the advance terminal area PBN procedures at mid-sized airports first, the TAPSS system was modified to manage arrival aircraft as they entered Terminal Radar Approach Control (TRACON). Dallas-Love Field airport (DAL) was selected by the FAA as a representative mid-sized airport within a constrained TRACON airspace due to the close proximity of a major airport, in this case Dallas-Ft Worth International Airport, one of the busiest in the world. To address this constraint, RNAV routes and Required Navigation Performance with the particular capability known as Radius-to-Fix (RNP-RF) approaches to a short final were used. The purpose of this simulation was to get feedback on how current operations could benefit with the TAPSS system and also to evaluate the efficacy of the advisory tools to support the broader use of PBN in the US National Airspace System. For this NASA-FAA joint experiment, an Air Traffic Control laboratory at NASA Ames was arranged to simulate arrivals into DAL in Instrument Meteorological Conditions utilizing parallel dependent approaches, with two feeder positions that handed off traffic to one final position. Four FAA controllers participated, alternately covering these three positions. All participants were Full-Performance Level terminal controllers and members of the National Air Traffic Controllers Association. During the simulation, PBN arrival operations were compared and contrasted in three conditions. They were the Baseline, where none of the TAPSS systems TRACON controller decision support advisories were provided, the Limited Advisories, reflecting the existing but dormant capabilities of the current terminal automation equipment with providing a subset of the TAPSS systems advisories; numerical delay, landing sequence, and runway assignment information, and the Full Advisories, with providing the following in addition to the ones in the Limited condition; trajectory slot markers, timelines of estimated times of arrivals and sched

Performance based navigation↗
NASA NTRS2016

AIRNOISE: A Tool for Preliminary Noise-Abatement Terminal Approach Route Design

Noise from aircraft in the airport vicinity is one of the leading aviation-induced environmental issues. The FAA developed the Integrated Noise Model (INM) and its replacement Aviation Environmental Design Tool (AEDT) software to assess noise impact resulting from all aviation activities. However, a software tool is needed that is simple to use for terminal route modification, quick and reasonably accurate for preliminary noise impact evaluation and flexible to be used for iterative design of optimal noise-abatement terminal routes. In this paper, we extend our previous work on developing a noise-abatement terminal approach route design tool, named AIRNOISE, to satisfy this criterion. First, software efficiency has been significantly increased by over tenfold using the C programming language instead of MATLAB. Moreover, a state-of-the-art high performance GPU-accelerated computing module is implemented that was tested to be hundreds time faster than the C implementation. Secondly, a Graphical User Interface (GUI) was developed allowing users to import current terminal approach routes and modify the routes interactively to design new terminal approach routes. The corresponding noise impacts are then calculated and displayed in the GUI in seconds. Finally, AIRNOISE was applied to Baltimore-Washington International Airport terminal approach route to demonstrate its usage.

aircraft noise↗
NASA NTRS2018

An Exploratory Evaluation of UAS Detect and Avoid Operations in the Terminal Environment

New technical standards for Unmanned Aircraft Systems (UAS) detect and avoid (DAA) systems mark recent progress toward realizing the goal of full integration of UAS into the National Airspace System (NAS). The DAA system is intended to provide a means of compliance with operating regulations that required pilots on board manned aircraft to remain "well clear" of other aircraft which is accomplished through out-the-window visual acquisition of other aircraft and application of a subjective judgment of safe separation. The requirements for the DAA system, including the specification of a DAA well clear threshold as well as functional requirements for detecting, tracking, alerting and guidance processing, and displays, are specified in DO-365, Minimum Operational Performance Standards (MOPS) for DAA Systems developed within RTCA Special Committee 228 (SC-228). Intended as the first in a series of phased versions, these requirements are frequently referred to as the "Phase 1" DAA system. The Phase 1 DAA system is limited for use by aircraft transitioning to and from Class A or special use airspace, through Class D, E, and G airspace. In particular, the Phase 1 DAA MOPS are not intended for terminal airspace operations, a critical gap for enabling a full range of UAS operations. The application of the Phase 1 DAA system and DAA well clear threshold within the terminal area is predicted to result in a high number of unnecessary alerts when the UAS is safely separated from other traffic. The goal of the present study was to examine pilot performance and operational issues related to the operation of the Phase 1 DAA system in a terminal area. This experiment was intended as an exploratory study that would be used to inform the development of a new terminal area-specific DAA well clear definition, and associated alerting and guidance requirements. The two main objectives of this study were to: 1) characterize pilot behavior in the terminal environment with the Phase 1 DAA system, and 2) investigate the effect of modifications to the Phase 1 DAA alerting and guidance structure. In particular, the authors were interested in determining whether the removal of specific alerting and guidance levels, without changing the DAA well clear definition or alerting thresholds, would impact pilot performance while conducting terminal operations. The results indicate that the Phase 1 well clear definition and alerting and guidance resulted in frequent alerting that degraded pilots' ability to discriminate between encounters where another aircraft was safely separated versus when a maneuver was necessary. The resulting impact on pilot performance was slower response times and higher frequency and severity of losses of DAA well clear compared to those observed for experiments examining pilot performance in the en route environment. There was no significant effect of alerting and guidance display configuration on pilot performance.

Rorie, Conrad↗
NASA NTRSDate not supplied

A Flexible Low-Cost Optical Communications Ground Terminal at NASA Goddard Space Flight Center

We present the status of ongoing work at NASA-Goddard Space Flight Center (GSFC) to build a low-cost flexible ground terminal for optical communication. Previous laser communication missions at NASA have been supported by one-of-a-kind ground terminals built specifically for each mission. If NASA is to build a global network of optical terminals to enable widespread use of optical communications, then a blueprint for an economical ground terminal able to support a variety of missions is needed. With this goal in mind, NASA is constructing a ground terminal in Greenbelt, Maryland to enable testing of new ground terminal technologies from industry to academia.

Robert E Lafon↗
DOE OSTI2026

Performance measurement of emerging 3- and 4-terminal tandem solar cells

Tandem solar cells are not limited to the conventional two-terminal (2-T) configuration. Multi-terminal designs like three-terminal (3-T) and four-terminal (4-T) devices have gained increasing attention in the PV community due to their relaxed current-matching requirement between subcells and their potential for enhanced energy yield. However, reliable and standardized methods for evaluating the performance of multi-terminal tandems remain underdeveloped. This work addresses this gap by providing comprehensive measurement guidelines tailored to these advanced configurations. We examine key coupling mechanisms between subcells, including the shared electrical load in 3-T devices and optical luminescent coupling in both 3-T and 4-T devices, to enable accurate and consistent performance evaluation. Furthermore, we propose two stabilized measurement methods for emerging 3-T tandem cells incorporating perovskite subcells: (1) a two-dimensional maximum-power-point tracking (MPPT) approach that continuously tracks both subcells' maximum power points (P MAX ) until convergence to stabilized outputs, and (2) a hybrid approach that combines MPPT for one subcell with stabilized current recording under fixed voltage biases near the P MAX of the other, allowing robust extraction of the overall stabilized P MAX (termed “MPPT + asymptotic P MA X scan” method). These methods directly address the dynamic current responses inherent to perovskite-containing tandems, providing a foundation for meaningful and reproducible performance comparisons.

14 SOLAR ENERGY↗