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NASA NTRS2016

Operational Characteristics Identification and Simulation Model Verification for Incheon International Airport

Incheon International Airport (ICN) is one of the hub airports in East Asia. Airport operations at ICN have been growing more than 5% per year in the past five years. According to the current airport expansion plan, a new passenger terminal will be added and the current cargo ramp will be expanded in 2018. This expansion project will bring 77 new stands without adding a new runway to the airport. Due to such continuous growth in airport operations and future expansion of the ramps, it will be highly likely that airport surface traffic will experience more congestion, and therefore, suffer from efficiency degradation. There is a growing awareness in aviation research community of need for strategic and tactical surface scheduling capabilities for efficient airport surface operations. Specific to ICN airport operations, a need for A-CDM (Airport - Collaborative Decision Making) or S-CDM(Surface - Collaborative Decision Making), and controller decision support tools for efficient air traffic management has arisen since several years ago. In the United States, there has been independent research efforts made by academia, industry, and government research organizations to enhance efficiency and predictability of surface operations at busy airports. Among these research activities, the Spot and Runway Departure Advisor (SARDA) developed and tested by National Aeronautics and Space Administration (NASA) is a decision support tool to provide tactical advisories to the controllers for efficient surface operations. The effectiveness of SARDA concept, was successfully verified through the human-in-the-loop (HITL) simulations for both spot release and runway operations advisories for ATC Tower controllers of Dallas/Fort Worth International Airport (DFW) in 2010 and 2012, and gate pushback advisories for the ramp controller of Charlotte/Douglas International Airport (CLT) in 2014. The SARDA concept for tactical surface scheduling is further enhanced and is being integrated into NASA's Airspace Technology Demonstration - 2 (ATD-2) project for technology demonstration of Integrated Arrival/Departure/Surface (ADS) operations at CLT. This study is a part of the international research collaboration between KAIA (Korea Agency for Infrastructure Technology Advancement)/KARI (Korea Aerospace Research Institute) and NASA, which is being conducted to validate the effectiveness of SARDA concept as a controller decision support tool for departure and surface management of ICN. This paper presents the preliminary results of the collaboration effort. It includes investigation of the operational environment of ICN, data analysis for identification of the operational characteristics of the airport, construction and verification of airport simulation model using Surface Operations Simulator and Scheduler (SOSS), NASA's fast-time simulation tool.

scheduling↗
NASA NTRS2016

Operational Characteristics Identification and Simulation Model Verification for Incheon International Airport

Incheon International Airport (ICN) is one of the hub airports in East Asia. Airport operations at ICN have been growing more than 5 percent per year in the past five years. According to the current airport expansion plan, a new passenger terminal will be added and the current cargo ramp will be expanded in 2018. This expansion project will bring 77 new stands without adding a new runway to the airport. Due to such continuous growth in airport operations and future expansion of the ramps, it will be highly likely that airport surface traffic will experience more congestion, and therefore, suffer from efficiency degradation. There is a growing awareness in aviation research community of need for strategic and tactical surface scheduling capabilities for efficient airport surface operations. Specific to ICN airport operations, a need for A-CDM (Airport - Collaborative Decision Making) or S-CDM (Surface - Collaborative Decision Making), and controller decision support tools for efficient air traffic management has arisen since several years ago. In the United States, there has been independent research efforts made by academia, industry, and government research organizations to enhance efficiency and predictability of surface operations at busy airports. Among these research activities, the Spot and Runway Departure Advisor (SARDA) developed and tested by National Aeronautics and Space Administration (NASA) is a decision support tool to provide tactical advisories to the controllers for efficient surface operations. The effectiveness of SARDA concept, was successfully verified through the human-in-the-loop (HITL) simulations for both spot release and runway operations advisories for ATC Tower controllers of Dallas-Fort Worth International Airport (DFW) in 2010 and 2012, and gate pushback advisories for the ramp controller of Charlotte-Douglas International Airport (CLT) in 2014. The SARDA concept for tactical surface scheduling is further enhanced and is being integrated into NASA's Airspace Technology Demonstration-2 (ATD-2) project for technology demonstration of Integrated Arrival-Departure-Surface (IADS) operations at CLT. This study is a part of the international research collaboration between KAIA (Korea Agency for Infrastructure Technology Advancement), KARI (Korea Aerospace Research Institute) and NASA, which is being conducted to validate the effectiveness of SARDA concept as a controller decision support tool for departure and surface management of ICN. This paper presents the preliminary results of the collaboration effort. It includes investigation of the operational environment of ICN, data analysis for identification of the operational characteristics of the airport, construction and verification of airport simulation model using Surface Operations Simulator and Scheduler (SOSS), NASA's fast-time simulation tool.

surface operations analysis↗
NASA NTRS2016

International Coordination of Exploring and Using Lunar Polar Volatiles

Fourteen international space agencies are participating in the International Space Exploration Coordination Group (ISECG), working together to advance a long-range strategy for human and robotic space exploration beyond low earth orbit. The ISECG is a voluntary, non-binding international coordination mechanism through which individual agencies may exchange information regarding interests, objectives, and plans in space exploration with the goal of strengthening both individual exploration programs as well as the collective effort. The ISECG has developed a Global Exploration Roadmap (GER) that reflects the coordinated international dialog and continued preparation for exploration beyond low-Earth orbit, beginning with the Moon and cis-lunar space, and continuing to near-Earth asteroids, and Mars.

Gruener, J. E.↗
NASA NTRS2016

International Space Exploration Coordination Group Assessment of Technology Gaps for Dust Mitigation for the Global Exploration Roadmap

The International Space Exploration Coordination Group (ISECG) formed two Gap Assessment teams to evaluate topic discipline areas that had not been worked at an international level to date. Accordingly, the ISECG Technology Working Group (TWG) recommended two discipline areas based on Global Exploration Roadmap (GER) Critical Technology Needs reflected within the GER Technology Development Map (GTDM): Dust Mitigation and LOX/Methane Propulsion, with this paper addressing the former. The ISECG approved the recommended Gap Assessment teams, and tasked the TWG to formulate the new teams with subject matter experts (SMEs) from the participating agencies. The participating agencies for the Dust Mitigation Gap Assessment Team were ASI, CSA, ESA, JAXA, and NASA. The team was asked to identify and make a presentation on technology gaps related to the GER2 mission scenario (including cislunar and lunar mission themes and long-lead items for human exploration of Mars) at the international level. In addition the team was tasked to produce a gap assessment in the form of a summary report and presentation identifying those GER Critical Technology Needs, including opportunities for international coordination and cooperation in closing the identified gaps. Dust is still a principal limiting factor in returning to the lunar surface for missions of any extended duration. However, viable technology solutions have been identified, but need maturation to be available to support both lunar and Mars missions.

dust↗
NASA NTRS2016

International Space Exploration Coordination Group Assessment of Technology Gaps for Dust Mitigation for the Global Exploration Roadmap

The International Space Exploration Coordination Group (ISECG) formed two Gap Assessment teams to evaluate topic discipline areas that had not been worked at an international level to date. Accordingly, the ISECG Technology Working Group (TWG) recommended two discipline areas based on Global Exploration Roadmap (GER) Critical Technology Needs reflected within the GER Technology Development Map (GTDM): Dust Mitigation and LOX/Methane Propulsion, with this paper addressing the former. The ISECG approved the recommended Gap Assessment teams, and tasked the TWG to formulate the new teams with subject matter experts (SMEs) from the participating agencies. The participating agencies for the Dust Mitigation Gap Assessment Team were ASI, CSA, ESA, JAXA, and NASA. The team was asked to identify and make a presentation on technology gaps related to the GER2 mission scenario (including cislunar and lunar mission themes and long-lead items for human exploration of Mars) at the international level. In addition the team was tasked to produce a gap assessment in the form of a summary report and presentation identifying those GER Critical Technology Needs, including opportunities for international coordination and cooperation in closing the identified gaps. Dust is still a principal limiting factor in returning to the lunar surface for missions of any extended duration. However, viable technology solutions have been identified, but need maturation to be available to support both lunar and Mars missions.

dust↗
NASA NTRS2016

Expanded Benefits for Humanity from the International Space Station

In 2012, the International Space Station (ISS) partnership published the updated International Space Station Benefits for Humanity, 2nd edition, a compilation of stories about the many benefits being realized in the areas of human health, Earth observations and disaster response, and global education. This compilation has recently been revised to include updated statistics on the impacts of the benefits, and new benefits that have developed since the first publication. Two new sections have also been added to the book, economic development of space and innovative technology. This paper will summarize the updates on behalf of the ISS Program Science Forum, made up of senior science representatives across the international partnership. The new section on "Economic Development of Space" highlights case studies from public-private partnerships that are leading to a new economy in low earth orbit (LEO). Businesses provide both transportation to the ISS as well as some research facilities and services. These relationships promote a paradigm shift of government-funded, contractor-provided goods and services to commercially-provided goods purchased by government agencies. Other examples include commercial firms spending research and development dollars to conduct investigations on ISS and commercial service providers selling services directly to ISS users. This section provides examples of ISS as a test bed for new business relationships, and illustrates successful partnerships. The second new section, Innovative Technology, merges technology demonstration and physical science findings that promise to return Earth benefits through continued research. Robotic refueling concepts for life extensions of costly satellites in geo-synchronous orbit have applications to robotics in industry on Earth. Flame behavior experiments reveal insight into how fuel burns in microgravity leading to the possibility of improving engine efficiency on Earth. Nanostructures and smart fluids are examples of materials improvements that are being developed using data from ISS. The publication also expands the benefits of research results in human health, environmental change and disaster response and in education activities developed to capture student imaginations in support of science, technology, engineering and mathematics, or STEM, education internationally. Applications to human health of the knowledge gained on ISS continues to grow and improve healthcare technologies and our understanding of human physiology. Distinct benefits return to Earth from the only orbiting multi-disciplinary laboratory of its kind. The ISS is a stepping stone for future space exploration by providing findings that develop LEO and improve life on our planet.

Rai, Amelia↗
NASA NTRS2018

Updated Benefits for Humanity from the International Space Station

Final document is attached. In 2018, the International Space Station (ISS) [Figure 1] partnership completed a revision for the third edition of the International Space Station Benefits for Humanity, a compilation of case studies of benefits being realized from ISS activities in the areas of human health, Earth observations and disaster response, innovative technology, global education, and economic development of space. The revision included new assessments of economic value and scientific value with more detail than the second edition. The third edition contains updated statistics on the impacts of the benefits as well as new benefits that have developed since the previous publication. This presentation will summarize the updates on behalf of the ISS Program Science Forum, which consists of senior science representatives across the ISS international partnership. An independent consultant determined the economic valuation (EV) of ISS research benefits case studies and the third edition contains the results. The process involved a preliminary assessment of economic, social, and innovation factors. A more detailed assessment followed, which included factors such as addressable market, market penetration, revenue generation, ability to leverage across other applications or customer groups, quality of life improvements, health benefits, environmental benefits, cultural and community cohesion, inspiration, new knowledge, novel approaches, creation of a unique market niche, and research leadership. Because of the unique microgravity environment of the ISS laboratory, the multidisciplinary and international nature of the research, and the significance of the investment in its development, analyzing ISS scientific impacts is an exceptional challenge. As a result, the ISS partnership determined the scientific valuation (SV) of ISS research using a combination of citation analyses, bibliometrics, and narratives of important ISS utilization results. Approximately 2,100 ISS results publications comprised of scientific journal articles, conference proceedings, and gray literature, representing over 5,000 authors and co-authors on Earth were used in this evaluation to enable the communication of impacts of ISS research on various science and technology fields across many countries. The publication also updates and expands the previously described benefits of research results in the areas of space commerce, technology development, human health, environmental change and disaster response, and education activities. Distinct benefits return to Earth from the only orbiting multidisciplinary laboratory of its kind. The ISS is a stepping-stone for future space exploration while also providing findings that develop low Earth orbit as a place for sustained human activity and improve life on our planet.

research↗
NASA NTRS2018

Updated Benefits for Humanity, Third Edition (B4H3), from the International Space Station (ISS)

In 2018, the International Space Station (ISS) [Figure 1] partnership completed a revision for the third edition of the International Space Station Benefits for Humanity, a compilation of case studies of benefits being realized from ISS activities in the areas of human health, Earth observations and disaster response, innovative technology, global education, and economic development of space. The revision included new assessments of economic value and scientific value with more detail than the second edition. The third edition contains updated statistics on the impacts of the benefits as well as new benefits that have developed since the previous publication. This presentation will summarize the updates on behalf of the ISS Program Science Forum, which consists of senior science representatives across the ISS international partnership. An independent consultant determined the economic valuation (EV) of ISS research benefits case studies and the third edition contains the results. The process involved a preliminary assessment of economic, social, and innovation factors. A more detailed assessment followed, which included factors such as addressable market, market penetration, revenue generation, ability to leverage across other applications or customer groups, quality of life improvements, health benefits, environmental benefits, cultural and community cohesion, inspiration, new knowledge, novel approaches, creation of a unique market niche, and research leadership. Because of the unique microgravity environment of the ISS laboratory, the multidisciplinary and international nature of the research, and the significance of the investment in its development, analyzing ISS scientific impacts is an exceptional challenge. As a result, the ISS partnership determined the scientific valuation (SV) of ISS research using a combination of citation analyses, bibliometrics, and narratives of important ISS utilization results. Approximately 2,100 ISS results publications comprised of scientific journal articles, conference proceedings, and gray literature, representing over 5,000 authors and co-authors on Earth were used in this evaluation to enable the communication of impacts of ISS research on various science and technology fields across many countries. The publication also updates and expands the previously described benefits of research results in the areas of space commerce, technology development, human health, environmental change and disaster response, and education activities. Distinct benefits return to Earth from the only orbiting multidisciplinary laboratory of its kind. The ISS is a stepping-stone for future space exploration while also providing findings that develop low Earth orbit as a place for sustained human activity and improve life on our planet.

ISS↗
NASA NTRSDate not supplied

Noise of Internally Mixed Exhaust Systems With External Plug For Supersonic Transport Applications

Internally mixed exhaust systems produce more noise than would be expected from an equivalent fully mixed flow. This ‘excess noise’ has never been fully explained and has not been researched recently as it is not as much of a problem for high bypass-ratio exhaust systems. Commercial supersonic vehicles, however, will use more moderate bypass ratio engines. Their exhaust systems will also likely feature external plugs to improve boat tail angle for cruise performance. Thus the problem of excess noise will need to be addressed along with the impacts of having an external plug. Recently, acoustic tests of dual-stream jet flows from both internal and external plug nozzles have been conducted. Measurements of noise from flows with an axisymmetric splitter and lobed forced mixer were made. These measurements show the baseline ‘excess noise’ previously found in forced mixer exhaust systems, and show how this noise source differs depending upon the plug geometry. Background-oriented schlieren measurements acquired simultaneously document the differences in shock structures over the transonic flow regime tested. The far-field acoustic measurements indicate that an external plug can slightly reduce the mixing noise of the jet plume when the flow is completely mixed, e.g. when the core and bypass streams have the same temperature and the flow is a single-stream jet. However, when the flow is not fully mixed, e.g. the usual case of an internally mixed exhaust system, the plug seems to amplify the ‘excess noise’ associated with the mixer. This additional noise source presents a challenge for nozzle designers wanting to use internally mixed exhaust systems with external plug nozzles.

Jet noise↗
NASA NTRS2021

ANOPP2’s Farassat Formulations Internal Functional Module (AFFIFM) Reference Manual

This manual documents version 1.4.0 of ANOPP2’s Farassat Formulations Internal Functional Modules (AFFIFMs) developed by NASA Langley Research Center’s Aeroacoustics Branch. The AFFIFMs provide the capability of calculating an acoustic pressure time history (APTH), or similar metric, provided one or more Ffowcs Williams and Hawkings (FWH) surfaces. AFFIFMs also allow for compact line sources. This application programming interface (API) is part of a larger toolkit called the Aircraft NOise Prediction Program 2 (ANOPP2). The goal of ANOPP2 is to provide the ability to independently: (1) assess aircraft system noise; (2) assess aircraft component noise; and (3) evaluate aircraft noise reduction technologies and flight procedures. Additionally, ANOPP2 is designed to provide a capability for understanding the fundamental physics involved in noise generation to support experiments and flight demonstration activities. As a component of ANOPP2, ANOPP2’s Farassat Formulations Internal Functional Modules and this document may be included as part of the ANOPP2 distribution, or they may be provided independent of that distribution. This is the ANOPP2 internal version of this document. It supersedes the NASA Internal Distribution(NID), US General Distribution (UGD), and General Public Distribution (GPD) versions.

Acoustics↗
NASA NTRS2022

Constraining Venus and Mars Internal Structures from the Gravity Response to Atmospheric Loading

The gravity fields of celestial bodies that possess an atmosphere are periodically perturbed by the redistribution of fluid mass associated with the atmospheric dynamics. A component of this perturbation is due to the gravitational response of the body to the deformation of its surface induced by the atmospheric pressure loading. The magnitude of this effect depends on the relation between the loading and the response in terms of geopotential variations measured by the load Love numbers. In this work, we simulate and analyze the gravity field generated by the atmospheres of Venus and Mars by accounting for different models of their internal structure. By precisely characterizing the phenomena that drive the mass transportation in the atmosphere through general circulation models, we determine the effect of the interior structure on the response to the atmospheric loading. An accurate estimation of the time-varying gravity field, which measures the atmospheric contribution, may provide significant constraints on the interior structure through the measurement of the load Love numbers. A combined determination of tidal and load Love numbers would enhance our knowledge of the interior of planetary bodies, providing further geophysical constraints in the inversion of internal structure models.The gravity fields of celestial bodies that possess an atmosphere are periodically perturbed by the redistribution of fluid mass associated with the atmospheric dynamics. A component of this perturbation is due to the gravitational response of the body to the deformation of its surface induced by the atmospheric pressure loading. The magnitude of this effect depends on the relation between the loading and the response in terms of geopotential variations measured by the load Love numbers. In this work, we simulate and analyze the gravity field generated by the atmospheres of Venus and Mars by accounting for different models of their internal structure. By precisely characterizing the phenomena that drive the mass transportation in the atmosphere through general circulation models, we determine the effect of the interior structure on the response to the atmospheric loading. An accurate estimation of the time-varying gravity field, which measures the atmospheric contribution, may provide significant constraints on the interior structure through the measurement of the load Love numbers. A combined determination of tidal and load Love numbers would enhance our knowledge of the interior of planetary bodies, providing further geophysical constraints in the inversion of internal structure models.

Mars↗
NASA NTRS2022

International Space Power System Interoperability Standards (ISPSIS)

This International Space Power System Interoperability Standards(ISPSIS) is the result of collaborations within the International Space Station (ISS) and Gateway memberships to establish interoperable interfaces, terminology, and techniques, to facilitate collaborative endeavors of space exploration in cislunar and deep space environments. These standards are available for international and commercial partnerships. Standards that are established and internationally recognized have been selected where possible to enable a variety of providers. Increasing hardware commonality among providers while decreasing unique configurations has the potential to reduce the traditional barriers in space exploration: overall mass and volume required to execute a mission. Standardizing interfaces reduces the scope of the development effort. The information within this document represents a set of parameters, which if accommodated in the system architecture support greater efficiencies, promote cost savings, and increase the probability of mission success. These standards are not intended to specify system details needed for implementation nor do they dictate design features behind the interface; specific requirements will be defined in unique documents.

David James Sadey↗
NASA NTRS2022

Geodetic Investigations of the Mission Concept MAGIC to Reveal Callisto’s Internal Structure

Geodetic and geophysical investigations of the Galilean moon Callisto address fundamental questions regarding the formation and evolution of the Jovian system. Callisto's evolution and internal structure appear to significantly differ from the other Jovian satellites. Similarly-sized Ganymede is a highly evolved ice-rock moon with a differentiated interior, intrinsic magnetic field, and abundant surface evidence of internal activity. In contrast, Callisto's surface is ancient, and Galileo spacecraft data suggest its interior is only incompletely differentiated, despite the presumed presence of a sub-surface ocean. These properties make Callisto uniquely able to constrain the timing and nature of the Jovian system formation. The Magnetics, Altimetry, Gravity, and Imaging of Callisto (MAGIC) mission concept is conceived to fully characterize the properties of this enigmatic moon from its deep interior to the icy shell. Three main instruments are included as a scientific payload. Highly accurate measurements of Callisto's topography, magnetic field, and morphology are obtained by the onboard laser altimeter, magnetometer, and camera, respectively. The telecommunication system supports an additional gravity and radio science investigation. Long- and short-wavelength gravity anomalies afford powerful constraints on internal differentiation and the properties of the hydrosphere (water and ice). Comprehensive numerical simulations and covariance analyses of MAGIC mission scenarios presented in this paper show that the gravitational degree-2 normalized coefficients and the pole obliquity enable the determination of the moment of inertia with an accuracy better than 0.015%. The combination of gravity and altimetry measurements acquired by MAGIC are essential to the characterization of Callisto's interior if – as is likely – the degree-2 gravity includes non-hydrostatic terms. MAGIC's radio science data yield the estimation of Callisto's gravity field with spatial resolutions of <100 km. The combination of gravitational and deformation tides that are retrieved by the radio science and altimetry investigations, respectively, leads to the recovery of the rigid ice shell thickness to within ∼3 km. Together these datasets would resolve ambiguities inherent in Galileo flyby data, revealing Callisto's interior structure as well as the existence and properties of its postulated internal ocean.

Antonio Genova↗
NASA NTRS2022

The International DORIS Service contribution to ITRF2020

For the realization of the 2020 International Terrestrial Reference Frame (ITRF2020), the International DORIS Service delivered to the International Earth Rotation and Reference Systems Service (IERS) a set of 1456 weekly solution files from 1993.0 to 2021.0 including station coordinates and Earth orientation parameters (EOPs). The data come from fourteen DORIS satellites: TOPEX/Poseidon, SPOT-2, SPOT-3, SPOT-4, SPOT-5, Envisat, Jason-1, Jason-2, Cryosat-2, Saral, HY-2A, Jason-3, Sentinel-3A and Sentinel-3B. In their processing, the four analysis centers which contributed to the DORIS combined solution used the latest time variable gravity models, the new mean pole and diurnal-subdiurnal tidal EOP models recommended by IERS. In addition, all the analysis centers included in their processing precise SPOT-5 solar panel angle values and quaternions for, at least, the Jason satellites. Furthermore, a new Alcatel phase center variation model was implemented for the ITRF2020 processing. The main objective of this study is to present the combination process and to analyze the impact of the new modeling on the performance of the new combined solution. Comparisons with the IDS contribution to ITRF2014 show that i) the application of the new phase center variations for the Alcatel DORIS ground antennas in the data processing combined with the gradual replacement over time of the Alcatel by Starec antennas implies a scale drift from 1993.0 to 2002.5 and ii) thanks to a better modeling of the surface forces on the satellites, the new combined solution shows smaller annual and 118-day signals in the geocenter. A new DORIS terrestrial reference frame was computed to evaluate the intrinsic quality of the new combined solution. That evaluation shows that over almost the full time span the intrinsic IDS scale values lie in a range of ±5 mm. After mid-2008, the new DORIS reference frame has an internal position consistency in North-East-Up better than 7.5 mm.

DORIS↗
NASA NTRSDate not supplied

Diagnosing Noise Features Of Internally Mixed, External Plug Exhaust Systems

In internally mixed exhaust systems, a lobed or forced mixer is employed to mix the core and bypass streams before they exit the common nozzle. For moderate bypass-ratio engines this marginally improves thrust, and provides a significant acoustic benefit. Indeed, it has been thought that a fully mixed jet creates the lowest noise you can get from a two-stream engine. Typically, the forced mixer system produces a bit more noise than a fully mixed equivalent jet, noise that has been called “excess noise”. In recent testing, this excess noise seemed to be amplified when an external plug was employed in the exhaust system to reduce boattail drag. Identifying the mechanism of this excess noise and mitigating it is key to creating commercial supersonic vehicles that are acoustically acceptable around airports. This paper adds to that investigation, analyzing results from recent tests where far-field acoustic data were acquired on two sets of flows with matched fully mixed flow conditions. One set of flows had a heated core stream, making it a dual-stream jet. The other set had both streams heated to the same temperature, making a single-stream jet that matched the fully mixed temperature and velocity of the dual-stream jet. These flows were tested in two lobed-mixer exhaust systems with internal and external plugs. Analysis of flow and noise data from the nozzles with combinations of single- and dual-stream flows, and with and without flight streams, gives insight into how and why the noise of the dual-stream and single-stream jet differ. One additive source, present in nozzles both with and without external plugs, comes from inside the nozzle, likely the internal shear layer coming off the lobed mixer. This noise source is not impacted by a change in flight stream and has a distinctive spectral directivity that is amplified by the presence of the external plug. Finding the exact source mechanism of this new source will be key to making the internally mixed exhaust systems reach their lowest possible sound level.

Noise prediction, supersonic, jet noise↗
NASA NTRSDate not supplied

Diagnosing Noise Features Of Internally Mixed, External Plug Exhaust Systems

In internally mixed exhaust systems, a lobed or forced mixer is employed to mix the core and bypass streams before they exit the common nozzle. For moderate bypass-ratio engines this marginally improves thrust, and provides a significant acoustic benefit. Indeed, it has been thought that a fully mixed jet creates the lowest noise you can get from a two-stream engine. Typically, the forced mixer system produces a bit more noise than a fully mixed equivalent jet, noise that has been called “excess noise”. In recent testing, this excess noise seemed to be amplified when an external plug was employed in the exhaust system to reduce boattail drag. Identifying the mechanism of this excess noise and mitigating it is key to creating commercial supersonic vehicles that are acoustically acceptable around airports. This paper adds to that investigation, analyzing results from recent tests where far-field acoustic data were acquired on two sets of flows with matched fully mixed flow conditions. One set of flows had a heated core stream, making it a dual-stream jet. The other set had both streams heated to the same temperature, making a single-stream jet that matched the fully mixed temperature and velocity of the dual-stream jet. These flows were tested in two lobed-mixer exhaust systems with internal and external plugs. Analysis of flow and noise data from the nozzles with combinations of single- and dual-stream flows, and with and without flight streams, gives insight into how and why the noise of the dual-stream and single-stream jet differ. One additive source, present in nozzles both with and without external plugs, comes from inside the nozzle, likely the internal shear layer coming off the lobed mixer. This noise source is not impacted by a change in flight stream and has a distinctive spectral directivity that is amplified by the presence of the external plug. Finding the exact source mechanism of this new source will be key to making the internally mixed exhaust systems reach their lowest possible sound level.

Noise prediction↗
DOE OSTI2025

Domestic and International Consensus Standards for Nuclear Criticality Safety - Overview & Status

The domestic and international consensus standards for nuclear criticality safety (NCS) were developed based on the lessons-learned from process criticality accidents. These consensus standards were developed to reduce the rate of process criticality accidents in facilities that process, store, handle, or transport fissionable materials by hand. After a significant increase in criticality accidents through the mid-1960s, the rate of criticality accidents decreased as a result of these standards, and the criticality accident rate is extremely low from an industrial safety perspective. The last known criticality accident inside the United States was in 1978 (nearly 47 years ago) at the Idaho Chemical Processing Plant, and outside the United States, an accident occurred at Tokai-mura, Japan, in 1999 (almost 26 years ago). The domestic consensus standards for NCS include the American National Standards (ANS) that are prepared and published by the American Nuclear Society and approved by the American National Standards Institute (ANSI). The ANS Standards Board, the NCS Consensus Committee, and the ANS-8 Subcommittee oversee the development and maintenance of these standards. There are currently 18 standards in the ANS-8 series. Nine ANS-8 standards are either in revision mode or planned for revision. A new standard for the use of nondestructive assay measurements (ANSI/ANS-8.28-2024) for NCS was approved in March of 2024. The international consensus standards for NCS calculations, procedures, and practices are maintained and developed within the International Organization for Standardization, Technical Committee 85 “Nuclear Energy,” Subcommittee 5, “Nuclear Fuel Technology,” and Working Group 8, “Nuclear Criticality Safety.” Eleven standards are currently available, four standards are proposed for revision, and four standards are at various stages of development. This paper provides the NCS community with a high-level overview and status report of domestic and international NCS consensus standards to stimulate interest and to support their continued development.

Bowen, Douglas G [ORNL] (ORCID:0000000212460026)↗
DOE OSTI2025

DECOVALEX-2023: An international collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems

The DECOVALEX initiative is an international research collaboration (www.decovalex.org), initiated in 1992, for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. DECOVALEX stands for “DEvelopment of COupled Models and VALidation against EXperiments”. The creation of this international initiative was motivated by the recognition that prediction of these coupled effects is an essential part of the performance and safety assessment of geologic disposal systems for radioactive waste and spent nuclear fuel. DECOVALEX emphasizes joint analysis and comparative modeling of the complex perturbations and coupled processes in geologic repositories and how these impact long-term performance predictions. The most recent phase of the DECOVALEX Project, here referred to as DECOVALEX-2023, started in early 2020 and ended in late 2023. More than fifty research teams associated with 17 international DECOVALEX partner organizations participated in the comparative evaluation of eight modeling tasks covering a wide range of spatial and temporal scales, geological formations, and coupled processes. This Virtual Special Issue on DECOVALEX-2023 provides an in-depth overview of these collaborative research efforts and how these have advanced the state-of-the-art of understanding and modeling coupled THMC processes. While primarily focused on radioactive waste, much of the work included here has wider application to many geoengineering topics.

Coupled processes↗