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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Framework for Network Co-Simulation

The Framework for Network Co-Simulation (FNCS) uses a federated approach to integrate simulations which may have differing time scales. Special consideration is given to integration with a communication network simulation such that inter-simulation messages may be optionally routed through and delayed by such a simulation. In addition, FNCS uses novel time synchronization algorithms to accelerate co-simulation including the application of speculative multithreading. FNCS accomplishes all of these improvements with minimal end user intervention. Simulations can be integrated using FNCS while maintaining their original model input files simply by linking with the FNCS library and making appropriate calls into the FNCS API.

Daily, Jeff↗
NASA NTRS1990

Rain-fade simulation and power augmentation for satellite communication systems

The design and implementation of an automated rain-fade simulation and power augmentation system is presented. The system experimentally simulates and measures the effects of radiofrequency power fade on a 20 GHz communication link using a multimode travelling wave tube amplifier for loss compensation. Precision, computer-controlled attenuators are used in the fade simulation. Test plans for analog and digital testing are discussed.

Shalkhauser, Kurt A.↗
NASA NTRS2012

Three-Dimensional Analysis of Deep Space Network Antenna Coverage

There is a need to understand NASA s Deep Space Network (DSN) coverage gaps and any limitations to provide redundant communication coverage for future deep space missions, especially for manned missions to Moon and Mars. The DSN antennas are required to provide continuous communication coverage for deep space flights, interplanetary missions, and deep space scientific observations. The DSN consists of ground antennas located at three sites: Goldstone in USA, Canberra in Australia, and Madrid in Spain. These locations are not separated by the exactly 120 degrees and some DSN antennas are located in the bowl-shaped mountainous terrain to shield against radiofrequency interference resulting in a coverage gap in the southern hemisphere for the current DSN architecture. To analyze the extent of this gap and other coverage limitations, simulations of the DSN architecture were performed. In addition to the physical properties of the DSN assets, the simulation incorporated communication forward link calculations and azimuth/elevation masks that constrain the effects of terrain for each DSN antenna. Analysis of the simulation data was performed to create coverage profiles with the receiver settings at a deep space altitudes ranging from 2 million to 10 million km and a spherical grid resolution of 0.25 degrees with respect to longitude and latitude. With the results of these simulations, two- and three-dimensional representations of the area without communication coverage and area with coverage were developed, showing the size and shape of the communication coverage gap projected in space. Also, the significance of this communication coverage gap is analyzed from the simulation data.

Kegege, Obadiah↗
NASA NTRS1995

Further Developments in the Communication Link and Error Analysis (CLEAN) Simulator

During the period 1 July 1993 - 30 June 1994, significant developments to the Communication Link and Error ANalysis (CLEAN) simulator were completed. Many of these were reported in the Semi-Annual report dated December 1993 which has been included in this report in Appendix A. Since December 1993, a number of additional modules have been added involving Unit-Memory Convolutional codes (UMC). These are: (1) Unit-Memory Convolutional Encoder module (UMCEncd); (2) Hard decision Unit-Memory Convolutional Decoder using the Viterbi decoding algorithm (VitUMC); and (3) a number of utility modules designed to investigate the performance of LTMC's such as LTMC column distance function (UMCdc), UMC free distance function (UMCdfree), UMC row distance function (UMCdr), and UMC Transformation (UMCTrans). The study of UMC's was driven, in part, by the desire to investigate high-rate convolutional codes which are better suited as inner codes for a concatenated coding scheme. A number of high-rate LTMC's were found which are good candidates for inner codes. Besides the further developments of the simulation, a study was performed to construct a table of the best known Unit-Memory Convolutional codes. Finally, a preliminary study of the usefulness of the Periodic Convolutional Interleaver (PCI) was completed and documented in a Technical note dated March 17, 1994. This technical note has also been included in this final report.

Ebel, William J.↗
NASA NTRS2009

Space Communications and Navigation (SCaN) Network Simulation Tool Development and Its Use Cases

In this work, we focus on the development of a simulation tool to assist in analysis of current and future (proposed) network architectures for NASA. Specifically, the Space Communications and Navigation (SCaN) Network is being architected as an integrated set of new assets and a federation of upgraded legacy systems. The SCaN architecture for the initial missions for returning humans to the moon and beyond will include the Space Network (SN) and the Near-Earth Network (NEN). In addition to SCaN, the initial mission scenario involves a Crew Exploration Vehicle (CEV), the International Space Station (ISS) and NASA Integrated Services Network (NISN). We call the tool being developed the SCaN Network Integration and Engineering (SCaN NI&E) Simulator. The intended uses of such a simulator are: (1) to characterize performance of particular protocols and configurations in mission planning phases; (2) to optimize system configurations by testing a larger parameter space than may be feasible in either production networks or an emulated environment; (3) to test solutions in order to find issues/risks before committing more significant resources needed to produce real hardware or flight software systems. We describe two use cases of the tool: (1) standalone simulation of CEV to ISS baseline scenario to determine network performance, (2) participation in Distributed Simulation Integration Laboratory (DSIL) tests to perform function testing and verify interface and interoperability of geographically dispersed simulations/emulations.

Jennings, Esther↗
NASA NTRS1965

Detection of, and communication with space vehicles during atmospheric entry, problems in simulation

In considering the problem of communicating with outer space and detection of spacecraft from the ground, one usually has to worry about only the propagation characteristics of electromagnetic waves of vacuum wavelength falling within either one of the two well known "atmospheric windows," namely; (1) the "optical window" extending from about 0.3 microns to a few microns, and (2) the "RF window" extending from a few millimeters to about 30 meters in the wavelength scale. However, during entry (or reentry) of a spacecraft into the earth's atmosphere, there exists two physical phenomena which tend to complicate the communication problem on the one hand, and to simplify the detection problem on the other hand.

Detection↗
NASA NTRS2012

Three Dimensional Computer Graphics Federates for the 2012 Smackdown Simulation

The Simulation Interoperability Standards Organization (SISO) Smackdown is a two-year old annual event held at the 2012 Spring Simulation Interoperability Workshop (SIW). A primary objective of the Smackdown event is to provide college students with hands-on experience in developing distributed simulations using High Level Architecture (HLA). Participating for the second time, the University of Alabama in Huntsville (UAHuntsville) deployed four federates, two federates simulated a communications server and a lunar communications satellite with a radio. The other two federates generated 3D computer graphics displays for the communication satellite constellation and for the surface based lunar resupply mission. Using the Light-Weight Java Graphics Library, the satellite display federate presented a lunar-texture mapped sphere of the moon and four Telemetry Data Relay Satellites (TDRS), which received object attributes from the lunar communications satellite federate to drive their motion. The surface mission display federate was an enhanced version of the federate developed by ForwardSim, Inc. for the 2011 Smackdown simulation. Enhancements included a dead-reckoning algorithm and a visual indication of which communication satellite was in line of sight of Hadley Rille. This paper concentrates on these two federates by describing the functions, algorithms, HLA object attributes received from other federates, development experiences and recommendations for future, participating Smackdown teams.

Fordyce, Crystal↗
NASA NTRS1998

Performance of Duplex Communication Between a LEO Satellite and Terrestrial Location Using a GEO Constellation

A network comprised of a terrestrial site, a constellation of three GEO satellites and a LEO satellite is modeled and simulated. Continuous communication between the terrestrial site and the LEO satellite is facilitated by the GEO satellites. The LEO satellite has the orbital characteristics of the International Space Station. Communication in the network is based on TCP/IP over ATM, with the ABR service category providing the QoS, at OC-3 data rate. The OSPF protocol is used for routing. We simulate FTP file transfers, with the terrestrial site serving as the client and the LEO satellite being the server. The performance characteristics are presented.

Robinson, Daryl C.↗
DOE OSTI2022

Implementation Aspects of Smart Grids Cyber-Security Cross-Layered Framework for Critical Infrastructure Operation

Communication networks in power systems are a major part of the smart grid paradigm. It enables and facilitates the automation of power grid operation as well as self-healing in contingencies. Such dependencies on communication networks, though, create a roam for cyber-threats. An adversary can launch an attack on the communication network, which in turn reflects on power grid operation. Attacks could be in the form of false data injection into system measurements, flooding the communication channels with unnecessary data, or intercepting messages. Using machine learning-based processing on data gathered from communication networks and the power grid is a promising solution for detecting cyber threats. In this paper, a co-simulation of cyber-security for cross-layer strategy is presented. The advantage of such a framework is the augmentation of valuable data that enhances the detection as well as identification of anomalies in the operation of the power grid. The framework is implemented on the IEEE 118-bus system. The system is constructed in Mininet to simulate a communication network and obtain data for analysis. A distributed three controller software-defined networking (SDN) framework is proposed that utilizes the Open Network Operating System (ONOS) cluster. According to the findings of our suggested architecture, it outperforms a single SDN controller framework by a factor of more than ten times the throughput. This provides for a higher flow of data throughout the network while decreasing congestion caused by a single controller’s processing restrictions. Furthermore, our CECD-AS approach outperforms state-of-the-art physics and machine learning-based techniques in terms of attack classification. The performance of the framework is investigated under various types of communication attacks.

cross-layered↗
NASA NTRS2014

Time Triggered Ethernet System Testing Means and Method

Methods and apparatus are provided for evaluating the performance of a Time Triggered Ethernet (TTE) system employing Time Triggered (TT) communication. A real TTE system under test (SUT) having real input elements communicating using TT messages with output elements via one or more first TTE switches during a first time interval schedule established for the SUT. A simulation system is also provided having input simulators that communicate using TT messages via one or more second TTE switches with the same output elements during a second time interval schedule established for the simulation system. The first and second time interval schedules are off-set slightly so that messages from the input simulators, when present, arrive at the output elements prior to messages from the analogous real inputs, thereby having priority over messages from the real inputs and causing the system to operate based on the simulated inputs when present.

Smithgall, William Todd↗
NASA NTRS2018

Medical Simulations for Exploration Medicine

Medical simulation is a useful tool that can be used to train personnel, develop medical processes, and assist cross-disciplinary communication. Medical simulations have been used in the past at NASA for these purposes, however they are usually created ad hoc. A stepwise approach to scenario development has not previously been used. The NASA Exploration Medical Capability (ExMC) created a medical scenario development tool to test medical procedures, technologies, concepts of operation and for use in systems engineering (SE) processes.

Reyes, David↗
NASA NTRSDate not supplied

Urban Air Mobility Conflict Resolution: Centralized or Decentralized?

This work begins to address one of the critical questions in the urban air mobility and small unmanned aircraft communities: Should the en-route conflict resolution function in an urban air mobility traffic system be centralized or decentralized? Three conflict resolution architectures are modeled and analyzed: centralized, decentralized with uniform rules, and decentralized with mixed rules. This study compares these architectures and investigates their robustness to communication and state information errors in terms of safety and efficiency metrics. Experiments are conducted using a high-fidelity Monte Carlo traffic simulator and a generic set of traffic scenarios with increasing traffic density. When no errors were modeled, the centralized architecture marginally outperformed the decentralized architecture. However, performance of the centralized architecture was found to be adversely affected by the modeled input errors to a greater degree than was the decentralized architecture. Performance of the centralized architecture also was degraded significantly by the modeled transmission errors of the centralized resolution maneuvers. In the decentralized architecture, uniform rules outperformed mixed rules because, in the mixed rules case, system safety performance was undermined and dominated by the poor performers.

Urban Air Mobility (UAM) traffic system↗
DOE OSTI2022

Multiple Phase Screen Electromagnetic Propagation Simulations of Starfish Prime Event

It has been decided at this point to pause development of the trans-ionospheric model, and the main goal of this document is to record the current status and maintain a list of references for the future. The 2D model appears to work: however, to truly gain meaningful information about the environment, the scintillation model should be integrated into an end-to-end communication link simulation, which includes much more phenomenology. It would be beneficial at this point to specify a particular link or system and import a HANE environments into existing simulations. Multiple realizations of the noise could then be applied, and communication signal budgets could be analyzed for particular systems.

42 ENGINEERING↗
DOE OSTI2019

Cybersecurity Assessments on Emulated DER Communication Networks

An increasing number of public utility commissions are adopting Distributed Energy Resource (DER) interconnection standards which require photovoltaic (PV) inverters, energy storage systems, and other DER to include interoperable grid-support functionality. The recently updated national standard, IEEE 1547-2018, requires all DER to include a Sun Spec Modbus, IEEE 2030.5, or IEEE 1815 communication interface in order to provide local and bulk power system services. Those communication protocols and associated information models will ensure system interoperability for PV and storage systems, but these new utility-to-DER communication networks must be deployed with sufficient cybersecurity to protect the U.S. power system and other critical infrastructure reliant on dependable power. Unlike bulk generators, DER are commonly connected to grid operators via public internet channels. These DER networks are exposed to a large attack surface that may leverage sophisticated techniques and infrastructure developed on IT systems, including remote exploits and distributed attacks. Although DER make up a growing portion of the national generation mix, they have limited processing capabilities and do not typically support modern security features such as encryption or authentication. In this work, Sandia National Laboratories constructed simulated DER communication net- works with a range of security features in order to study the security posture of different communication approaches. The experimental test environment was created in a Sandia-developed co-simulation platform, called SCEPTRE, which emulated Sun Spec-compliant DER equipment, the utility DER management system, communication network, and distribution power system. Adversary-based assessments were conducted and a quantitative scoring criteria was applied to evaluate the resilience of various architectures against cyber attacks and to measure the systemic impact during such attacks. The team found that network segmentation, encryption, and moving target defense improved the security of these networks and would be recommended for utility, aggregator, and local DER networks.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1991

Individual differences in airline captains' personalities, communication strategies, and crew performance

Aircrew effectiveness in coping with emergencies has been linked to captain's personality profile. The present study analyzed cockpit communication during simulated flight to examine the relation between captains' discourse strategies, personality profiles, and crew performance. Positive Instrumental/Expressive captains and Instrumental-Negative captains used very similar communication strategies and their crews made few errors. Their talk was distinguished by high levels of planning and strategizing, gathering information, predicting/alerting, and explaining, especially during the emergency flight phase. Negative-Expressive captains talked less overall, and engaged in little problem solving talk, even during emergencies. Their crews made many errors. Findings support the theory that high crew performance results when captains use language to build shared mental models for problem situations.

Orasanu, Judith↗
NASA NTRS1972

Study of mathematical modeling of communication systems transponders and receivers

The modeling of communication receivers is described at both the circuit detail level and at the block level. The largest effort was devoted to developing new models at the block modeling level. The available effort did not permit full development of all of the block modeling concepts envisioned, but idealized blocks were developed for signal sources, a variety of filters, limiters, amplifiers, mixers, and demodulators. These blocks were organized into an operational computer simulation of communications receiver circuits identified as the frequency and time circuit analysis technique (FATCAT). The simulation operates in both the time and frequency domains, and permits output plots or listings of either frequency spectra or time waveforms from any model block. Transfer between domains is handled with a fast Fourier transform algorithm.

Walsh, J. R.↗