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NASA NTRS2012

Radiation Shielding Materials Containing Hydrogen, Boron, and Nitrogen: Systematic Computational and Experimental Study

The key objectives of this study are to investigate, both computationally and experimentally, which forms, compositions, and layerings of hydrogen, boron, and nitrogen containing materials will offer the greatest shielding in the most structurally robust combination against galactic cosmic radiation (GCR), secondary neutrons, and solar energetic particles (SEP). The objectives and expected significance of this research are to develop a space radiation shielding materials system that has high efficacy for shielding radiation and that also has high strength for load bearing primary structures. Such a materials system does not yet exist. The boron nitride nanotube (BNNT) can theoretically be processed into structural BNNT and used for load bearing structures. Furthermore, the BNNT can be incorporated into high hydrogen polymers and the combination used as matrix reinforcement for structural composites. BNNT's molecular structure is attractive for hydrogen storage and hydrogenation. There are two methods or techniques for introducing hydrogen into BNNT: (1) hydrogen storage in BNNT, and (2) hydrogenation of BNNT (hydrogenated BNNT). In the hydrogen storage method, nanotubes are favored to store hydrogen over particles and sheets because they have much larger surface areas and higher hydrogen binding energy. The carbon nanotube (CNT) and BNNT have been studied as potentially outstanding hydrogen storage materials since 1997. Our study of hydrogen storage in BNNT - as a function of temperature, pressure, and hydrogen gas concentration - will be performed with a hydrogen storage chamber equipped with a hydrogen generator. The second method of introducing hydrogen into BNNT is hydrogenation of BNNT, where hydrogen is covalently bonded onto boron, nitrogen, or both. Hydrogenation of BN and BNNT has been studied theoretically. Hyper-hydrogenated BNNT has been theoretically predicted with hydrogen coverage up to 100% of the individual atoms. This is a higher hydrogen content than possible with hydrogen storage; however, a systematic experimental hydrogenation study has not been reported. A combination of the two approaches may be explored to provide yet higher hydrogen content. The hydrogen containing BNNT produced in our study will be characterized for hydrogen content and thermal stability in simulated space service environments. These new materials systems will be tested for their radiation shielding effectiveness against high energy protons and high energy heavy ions at the HIMAC facility in Japan, or a comparable facility. These high energy particles simulate exposure to SEP and GCR environments. They will also be tested in the LaRC Neutron Exposure Laboratory for their neutron shielding effectiveness, an attribute that determines their capability to shield against the secondary neutrons found inside structures and on lunar and planetary surfaces. The potential significance is to produce a radiation protection enabling technology for future exploration missions. Crew on deep space human exploration missions greater than approximately 90 days cannot remain below current crew Permissible Exposure Limits without shielding and/or biological countermeasures. The intent of this research is to bring the Agency closer to extending space missions beyond the 90-day limit, with 1 year as a long-term goal. We are advocating a systems solution with a structural materials component. Our intent is to develop the best materials system for that materials component. In this Phase I study, we have shown, computationally, that hydrogen containing BNNT is effective for shielding against GCR, SEP, and neutrons over a wide range of energies. This is why we are focusing on hydrogen containing BNNT as an innovative advanced concept. In our future work, we plan to demonstrate, experimentally, that hydrogen, boron, and nitrogen based materials can provide mechanically strong, thermally stable, structural materials with effective radiation shielding against GCR, SEP, and neutrons.

Radiation↗

NASA NTRS2016

Probabilistic Modeling of Aircraft Trajectories for Dynamic Separation Volumes

With a proliferation of new and unconventional vehicles and operations expected in the future, the ab initio airspace design will require new approaches to trajectory prediction for separation assurance and other air traffic management functions. This paper presents an approach to probabilistic modeling of the trajectory of an aircraft when its intent is unknown. The approach uses a set of feature functions to constrain a maximum entropy probability distribution based on a set of observed aircraft trajectories. This model can be used to sample new aircraft trajectories to form an ensemble reflecting the variability in an aircraft's intent. The model learning process ensures that the variability in this ensemble reflects the behavior observed in the original data set. Computational examples are presented.

Lewis, Timothy A.↗

NASA NTRS2016

Tool for Generation of MAC/GMC Representative Unit Cell for CMC/PMC Analysis

This document describes a recently developed analysis tool that enhances the resident capabilities of the Micromechanics Analysis Code with the Generalized Method of Cells (MAC/GMC) 4.0. This tool is especially useful in analyzing ceramic matrix composites (CMCs), where higher fidelity with improved accuracy of local response is needed. The tool, however, can be used for analyzing polymer matrix composites (PMCs) as well. MAC/GMC 4.0 is a composite material and laminate analysis software developed at NASA Glenn Research Center. The software package has been built around the concept of the generalized method of cells (GMC). The computer code is developed with a user friendly framework, along with a library of local inelastic, damage, and failure models. Further, application of simulated thermomechanical loading, generation of output results, and selection of architectures to represent the composite material have been automated to increase the user friendliness, as well as to make it more robust in terms of input preparation and code execution. Finally, classical lamination theory has been implemented within the software, wherein GMC is used to model the composite material response of each ply. Thus, the full range of GMC composite material capabilities is available for analysis of arbitrary laminate configurations as well. The primary focus of the current effort is to provide a graphical user interface (GUI) capability that generates a number of different user-defined repeating unit cells (RUCs). In addition, the code has provisions for generation of a MAC/GMC-compatible input text file that can be merged with any MAC/GMC input file tailored to analyze composite materials. Although the primary intention was to address the three different constituents and phases that are usually present in CMCs-namely, fibers, matrix, and interphase-it can be easily modified to address two-phase polymer matrix composite (PMC) materials where an interphase is absent. Currently, the tool capability includes generation of RUCs for square packing, hexagonal packing, and random fiber packing as well as RUCs based on actual composite micrographs. All these options have the fibers modeled as having a circular cross-sectional area. In addition, a simplified version of RUC is provided where the fibers are treated as having a square cross section and are distributed randomly. This RUC facilitates a speedy analysis using the higher fidelity version of GMC known as HFGMC. The first four mentioned options above support uniform subcell discretization. The last one has variable subcell sizes due to the primary intention of keeping the RUC size to a minimum to gain the speed ups using the higher fidelity version of MAC. The code is implemented within the MATLAB (The Mathworks, Inc., Natick, MA) developmental framework; however, a standalone application that does not need a priori MATLAB installation is also created with the aid of the MATLAB compiler.

Materials Engineering↗

NASA NTRS2015

3rd Annual NASA Ames Space Science and Astrobiology Jamboree

The Space Science and Astrobiology Division at NASA Ames Research Center consists of over 50 civil servants and more than 110 contractors, co-‐ops, post-‐docs and associates. Researchers in the division are pursuing investigations in a variety of fields including exoplanets, planetary science, astrobiology and astrophysics. In addition, division personnel support a wide variety of NASA missions including (but not limited to) Kepler, SOFIA, LADEE, JWST, and New Horizons. With such a wide variety of interesting research going on, distributed among three branches in at least 5 different buildings, it can be difficult to stay abreast of what one's fellow researchers are doing. Our goal in organizing this symposium is to facilitate communication and collaboration among the scientists within the division, and to give center management and other ARC researchers and engineers an opportunity to see what scientific research and science mission work is being done in the division. We are also continuing the tradition within the Space Science and Astrobiology Division to honor one senior and one early career scientist with the Pollack Lecture and the Early Career Lecture, respectively. With the Pollack Lecture, our intent is to select a senior researcher who has made significant contributions to any area of research within the space sciences, and we are pleased to honor Dr. William Borucki this year. With the Early Career Lecture, our intent is to select a young researcher within the division who, by their published scientific papers, shows great promise for the future in any area of space science research, and we are pleased to honor Dr. Melinda Kahre this year

Dotson, Jessie↗

NASA NTRS2016

Heuristics for Relevancy Ranking of Earth Dataset Search Results

As the Variety of Earth science datasets increases, science researchers find it more challenging to discover and select the datasets that best fit their needs. The most common way of search providers to address this problem is to rank the datasets returned for a query by their likely relevance to the user. Large web page search engines typically use text matching supplemented with reverse link counts, semantic annotations and user intent modeling. However, this produces uneven results when applied to dataset metadata records simply externalized as a web page. Fortunately, data and search provides have decades of experience in serving data user communities, allowing them to form heuristics that leverage the structure in the metadata together with knowledge about the user community. Some of these heuristics include specific ways of matching the user input to the essential measurements in the dataset and determining overlaps of time range and spatial areas. Heuristics based on the novelty of the datasets can prioritize later, better versions of data over similar predecessors. And knowledge of how different user types and communities use data can be brought to bear in cases where characteristics of the user (discipline, expertise) or their intent (applications, research) can be divined. The Earth Observing System Data and Information System has begun implementing some of these heuristics in the relevancy algorithm of its Common Metadata Repository search engine.

science data management↗

NASA NTRS2017

Relevancy Ranking of Satellite Dataset Search Results

science data management↗

NASA NTRS2017

Progress of High Efficiency Centrifugal Compressor Simulations Using TURBO

Three-dimensional, time-accurate, and phase-lagged computational fluid dynamics (CFD) simulations of the High Efficiency Centrifugal Compressor (HECC) stage were generated using the TURBO solver. Changes to the TURBO Parallel Version 4 source code were made in order to properly model the no-slip boundary condition along the spinning hub region for centrifugal impellers. A startup procedure was developed to generate a converged flow field in TURBO. This procedure initialized computations on a coarsened mesh generated by the Turbomachinery Gridding System (TGS) and relied on a method of systematically increasing wheel speed and backpressure. Baseline design-speed TURBO results generally overpredicted total pressure ratio, adiabatic efficiency, and the choking flow rate of the HECC stage as compared with the design-intent CFD results of Code Leo. Including diffuser fillet geometry in the TURBO computation resulted in a 0.6 percent reduction in the choking flow rate and led to a better match with design-intent CFD. Diffuser fillets reduced annulus cross-sectional area but also reduced corner separation, and thus blockage, in the diffuser passage. It was found that the TURBO computations are somewhat insensitive to inlet total pressure changing from the TURBO default inlet pressure of 14.7 pounds per square inch (101.35 kilopascals) down to 11.0 pounds per square inch (75.83 kilopascals), the inlet pressure of the component test. Off-design tip clearance was modeled in TURBO in two computations: one in which the blade tip geometry was trimmed by 12 mils (0.3048 millimeters), and another in which the hub flow path was moved to reflect a 12-mil axial shift in the impeller hub, creating a step at the hub. The one-dimensional results of these two computations indicate non-negligible differences between the two modeling approaches.

turbomachinery↗

NASA NTRS2017

Wind Tunnel Strain-Gage Balance Calibration Data Analysis Using a Weighted Least Squares Approach

A new approach is presented that uses a weighted least squares fit to analyze wind tunnel strain-gage balance calibration data. The weighted least squares fit is specifically designed to increase the influence of single-component loadings during the regression analysis. The weighted least squares fit also reduces the impact of calibration load schedule asymmetries on the predicted primary sensitivities of the balance gages. A weighting factor between zero and one is assigned to each calibration data point that depends on a simple count of its intentionally loaded load components or gages. The greater the number of a data point's intentionally loaded load components or gages is, the smaller its weighting factor becomes. The proposed approach is applicable to both the Iterative and Non-Iterative Methods that are used for the analysis of strain-gage balance calibration data in the aerospace testing community. The Iterative Method uses a reasonable estimate of the tare corrected load set as input for the determination of the weighting factors. The Non-Iterative Method, on the other hand, uses gage output differences relative to the natural zeros as input for the determination of the weighting factors. Machine calibration data of a six-component force balance is used to illustrate benefits of the proposed weighted least squares fit. In addition, a detailed derivation of the PRESS residuals associated with a weighted least squares fit is given in the appendices of the paper as this information could not be found in the literature. These PRESS residuals may be needed to evaluate the predictive capabilities of the final regression models that result from a weighted least squares fit of the balance calibration data.

calibration analysis↗

NASA NTRS2016

Anthropomorphic Robot Design and User Interaction Associated with Motion

Though in its original concept a robot was conceived to have some human-like shape, most robots now in use have specific industrial purposes and do not closely resemble humans. Nevertheless, robots that resemble human form in some way have continued to be introduced. They are called anthropomorphic robots. The fact that the user interface to all robots is now highly mediated means that the form of the user interface is not necessarily connected to the robots form, human or otherwise. Consequently, the unique way the design of anthropomorphic robots affects their user interaction is through their general appearance and the way they move. These robots human-like appearance acts as a kind of generalized predictor that gives its operators, and those with whom they may directly work, the expectation that they will behave to some extent like a human. This expectation is especially prominent for interactions with social robots, which are built to enhance it. Often interaction with them may be mainly cognitive because they are not necessarily kinematically intricate enough for complex physical interaction. Their body movement, for example, may be limited to simple wheeled locomotion. An anthropomorphic robot with human form, however, can be kinematically complex and designed, for example, to reproduce the details of human limb, torso, and head movement. Because of the mediated nature of robot control, there remains in general no necessary connection between the specific form of user interface and the anthropomorphic form of the robot. But their anthropomorphic kinematics and dynamics imply that the impact of their design shows up in the way the robot moves. The central finding of this report is that the control of this motion is a basic design element through which the anthropomorphic form can affect user interaction. In particular, designers of anthropomorphic robots can take advantage of the inherent human-like movement to 1) improve the users direct manual control over robot limbs and body positions, 2) improve users ability to detect anomalous robot behavior which could signal malfunction, and 3) enable users to be better able to infer the intent of robot movement. These three benefits of anthropomorphic design are inherent implications of the anthropomorphic form but they need to be recognized by designers as part of anthropomorphic design and explicitly enhanced to maximize their beneficial impact. Examples of such enhancements are provided in this report. If implemented, these benefits of anthropomorphic design can help reduce the risk of Inadequate Design of Human and Automation Robotic Integration (HARI) associated with the HARI-01 gap by providing efficient and dexterous operator control over robots and by improving operator ability to detect malfunctions and understand the intention of robot movement.

automation/robotic integration↗

NASA NTRS2018

Overview of the Exploration Exercise Device Validation Study Plans

The NASA has determined that a multi-functional exercise device will be developed for use as an exercise device during exploration missions. The device will allow for full body resistance and metabolic exercise necessary to minimize physiological losses during space flight and to maintain fitness necessary to perform critical mission tasks. Prior to implementation as an exercise device on an Exploration vehicle, there will be verification and validation testing completed to determine device efficacy at providing the necessary training stimuli to achieve desired goals. Because the exploration device will be new device that has yet be specified, specific Verification and Validation (V&V) protocols have yet to be developed. Upon delivery of an exploration exercise device training unit, stakeholders throughout NASA will develop V&V plans that include ground-based testing and testing on the International Space Station (ISS). Stakeholders will develop test protocols that include success criterion for the device. Ground tests will occur at NASA Johnson Space Station prior to flight testing. The intents of the ground tests are to allow crew, spaceflight medicine, science, engineering, Astronaut Strength, Conditioning, and Reconditioning staff, and others to gain experience in the best utilization of the device. The goal is to obtain an evidence base for recommending use of the device on the ISS. The developed protocol will be created to achieve multiple objectives, including determining if the device provides an adequate training stimulus for 5th - 95th percentile males and females, allows for exercise modalities that protect functional capability, and is robust and can withstand extensive human use. Although protocols are yet to be determined, current expectations include use of the device by test subjects and current crew in order to obtain quantitative and qualitative feedback. Information obtained during the ground tests may be used to influence device modifications during design iterations. Assuming successful ground tests, the device will be installed on the ISS for testing during space flight. Spaceflight testing is envisioned to include an activation and checkout (ACO) phase and a V&V phase. During the ACO phase, 1-2 crewmembers will exercise with the device to ensure proper function. ACO is expected to last multiple months because of the many modes and methods of exercise that need to be assessed. However, the goal is to complete the ACO as quickly as possible. Once successful ACO occurs, the crew will be free to use the device for normal exercise pending concurrence from stakeholders. V&V tests on the ISS will ideally consist of crew using the device for all of their exercise for an entire mission. Exercise prescriptions will be supplied that replicate expected prescriptions during exploration missions. Crew that are not enrolled in the V&V studies would be also free to use the device as their schedule permits. As experience is gained by users, exercise protocols could change. The intent of all V&V testing is to ensure that all have thorough understanding of experience at optimizing device capability

DeWitt, J. K.↗

NASA NTRS2018

Creating Innovative Frameworks to Spur Cultural Change at NASA Armstrong Flight Research Center

Changing the culture of an organization is a monumental task that often takes years and has no set formula. Steps can be taken, however, to spur cultural change by creating spaces and infrastructure to serve as the initial driving force. An innovation space and a bicycle sharing (bike share) program were implemented at the National Aeronautics and Space Administration (NASA) Armstrong Flight Research Center (AFRC) (Edwards, California) with a vision toward connecting Center personnel, fostering collaboration and innovation, retaining newer employees, promoting flexibility, and improving the culture and workplace atmosphere. This paper discusses the steps taken, challenges faced, novel culture-change-focused design elements, lessons learned, acquired metrics, and how these initiated cultural change at AFRC. For both the innovation space and the bike share program, funding was negotiated and provided through the NASA Convergent Aeronautics Solutions (CAS) project, which was seeking to improve the innovation and collaboration capabilities at each of the four NASA aeronautics Centers. Key stakeholders across AFRC from upper management, facilities, safety, engineering, and procurement were identified early in the process and were consulted and included throughout execution to ensure that any encountered roadblocks could be easily navigated. Research was then conducted by attending conferences and visiting culture-changing organizations both inside and outside United States Government agencies. Distilling the research, identifying available space, and deciding on specific design elements for the space was conducted by a subset of individuals of diverse backgrounds to enable quick, effective decision-making. Decisions were made with the intent to increase usage and diversity of users of the space; care was taken to ensure a well-crafted atmosphere that would foster the desired culture change. The allocated physical space required major structural modifications, new furniture, and new capabilities that would bring people in. Decisions and desires underwent a rapid reiterative process in order to stay within budget and short deadlines, while holding firm to what was seen as fundamental elements of an innovation space. The framework for cultural change being established, the more difficult task began: incubating the desired culture. Intentional workday use of the innovation space was encouraged, and organized events coordinated in order to truly foster culture change. Such incubation supports the organic spread of culture change to all areas of AFRC. This framework was complemented and expanded by the implementation of the bike share program. Steps for implementation included bike selection based on lessons learned, creating bike stations and signage, implementing bike share rules, and building a volunteer maintenance infrastructure. A novel user-reporting feedback system at each bike station is a low-impact method of capturing usage metrics. Due to the nature of the work conducted at AFRC, the bike share program and feedback system were negotiated and vetted through various organizations including legal, safety, and operations. The innovation space and the bike share program together are an effective initial framework for innovation and collaboration. Culture change takes time, but the innovation space and the bike share program are already showing signs of making a positive impact on the AFRC workforce.

rooms↗

NASA NTRS2019

Swirl Distortion Using Stream Vanes for Boundary Layer Ingestion Research

The swirl distortion of a StreamVane (Trademark) was investigated in the NASA Glenn Research Center W8 test facility. The StreamVane (Trademark) was designed and generated by Virginia Tech based on CFD simulations and included a center body at the aerodynamic interface plane. The swirl pattern generated by the distortion was evaluated using a dense grid of 5-hole Pitot probe measurements captured using a rotating array of probes. Good agreement was found between the design intent and the results at 38.5 kg/s mass flow. The StreamVane (Trademark) swirl results were compared to clean facility flow at 5 inlet mass flows and found to be consistent. Additionally, the axial location of the StreamVane (Trademark) relative to the measurement plane was investigated to determine the impact on downstream total pressure loss generated by the vanes. The intent of this work was to assess the viability of using a StreamVane (Trademark) to generate a Type I or Type II distortion into a Boundary Layer Ingesting propulsor to assess its aerodynamic performance and aeromechanic response.

swirl distortion↗

NASA NTRS2015

Conflict Alerts for Aircraft Conducting Visual Approaches

It is common for aircraft to conduct visual and instrument final approaches to a single runway or multiple parallel runways. Useful, nonexcessive safety alerts on aircraft conducting visual approaches are helpful to air traffic controllers, though pilots are responsible for separation with the preceding aircraft. A variety of visual approaches to various runway configurations are studied, and a set of safety alert thresholds is proposed. Fast-time simulations with recorded real-world air traffic data of mostly visual approach flights are performed on a prototype tactical separation assurance system for terminal airspace. Alerts are generated -- with both the standard separation thresholds and the proposed safety alert thresholds -- and compared with those from the Conflict Alert (CA) functionality in the Standard Terminal Automation Replacement System (STARS). The results show that the number of Mode-C Intruder alerts generated was reduced 76% as compared to STARS CA. The nuisance alerts generated by assuming visual to be instrument approaches was reduced by 92% when the proposed safety alert thresholds were used and visual approaches were assumed.A set of safety alert thresholds, which allow safety alerts to be provided to the controllers for aircraft conductingvisual approaches to a single runway or multiple parallel runways, has been proposed based on input from SubjectMatter Experts as well as visual approach procedures and common practices. The goal is to maximize the thresholdswithin the guidance of the procedures and common practices and to minimize the number of nuisance alerts and totalnumber of alerts with the support of flight intent information. Tests have been performed using a recently developedprototype tactical separation assurance system for terminal airspace, called Terminal Tactical Separation-AssuredFlight Environment (T-TSAFE). The input was a full day of air traffic data from Dallas/Fort Worth (DFW) TRACONwith most arriving flights conducting visual approaches. The results compare favorably with those of the ConflictAlert (CA) functionality of the Standard Terminal Automation Replacement System (STARS).When fast-time simulation experiment was performed using T-TSAFE with all arriving flights assumed to conductinstrument approaches, the expected large number of separation alerts were observed. When compared with STARSCA, the conflict pairs common to both T-TSAFE and STARS CA was only 21% of the total STARS CA alerts. As aresult, the nuisance-alert rate for STARS CA was estimated to be about 70%, which is comparable to a similar previously estimation of 80% nuisance-alert rate for CARTS (Common Automated Radar Terminal System) CA. The Mode-CIntruder (MCI) alerts were also reduced by 76% as compared to STARS CA.Examination of the common conflict pairs between T-TSAFE and STARS CA shows that they are valid separationconflicts with good alert lead times for T-TSAFE. However, many of them would still be considered nuisance alertsif the aircraft were conducting visual approaches. This was confirmed by another visual approach fast-time simulationT-TSAFE experiment, in which all DFW arriving flights were assumed to be on visual approaches and our proposedsafety alert thresholds were used and tested. The result of the experiment showed that the number of non-MCI alertswas less by 92% as compared to the number when all DFW arrivals were assumed to be conducting instrumentapproaches. The common conflict pairs involving aircraft conducting visual approaches to parallel runways werereduced by 93% as well. Thus, the flight intent information and the safety alert thresholds are effective in reducingnuisance alerts.T-TSAFE can thus provide separation and safety conflict alerts seamlessly in the real-world environment of mixedterminal operations with arriving flights of both visual and instrument approaches. Compared with STARS CA, TTSAFEhas fewer false alerts, larger alert lead time, and larger alert thresholds. While the nuisance alerts are reducedsignificantly with the safety alert thresholds, further work is needed to study if the alert lead time for safety alerts issufficient.

Tang, Huabin↗

NASA NTRS2016

NASA Ames Space Science and Astrobiology: 4th Annual Jamboree

Welcome to the Fourth Annual Ames Space Sciences and Astrobiology Jamboree! The Space Science and Astrobiology Division at NASA Ames Research Center consists of over 50 civil servants and more than 110 contractors, co-‐ops, post-‐docs and associates. Researchers in the division are pursuing investigations in a variety of fields including exoplanets, planetary science, astrobiology and astrophysics. In addition, division personnel support a wide variety of NASA missions including (but not limited to) Kepler, SOFIA, LADEE, JWST, and New Horizons. With such a wide variety of interesting research going on, distributed among three branches in at least 5 different buildings, it can be difficult to stay abreast of what one’s fellow researchers are doing. Our goal in organizing this symposium is to facilitate communication and collaboration among the scientists within the division, and to give center management and other ARC researchers and engineers an opportunity to see what scientific research and science mission work is being done in the division. We are also continuing the tradition within the Space Science and Astrobiology Division to honor one senior and one early career scientist with the Pollack Lecture and the Early Career Lecture, respectively. With the Pollack Lecture, our intent is to select a senior researcher who has made significant contributions to any area of research within the space sciences, and we are pleased to honor Dr. David DesMarais this year. With the Early Career Lecture, our intent is to select a young researcher within the division who, by their published scientific papers, shows great promise for the future in any area of space science research, and we are pleased to honor Dr. Christiaan Boersma this year.

Dotson, Jessie↗

NASA NTRS2019

Over-the-Rotor Liner Investigation via the NASA Langley Normal Incidence Tube

NASA Langley and Glenn Research Centers have collaborated on the usage of acoustic liners mounted very near or directly over the rotor of turbofan aircraft engines. This collaboration began over a decade ago with the investigation of a metallic foam liner. Similar to conventional acoustic liner applications, this liner was designed to absorb sound generated by the rotor-alone and rotor-stator interaction sources within the fan duct. Given its proximity to the rotor tips, the expectation was that the liner would also serve as a pressure release and thereby inhibit the amount of noise generated. Initial acoustic results were promising, but there was concern regarding potential aerodynamic penalties. Nevertheless, there were sufficient positive results to warrant further investigation. To that end, the current report presents results obtained in the NASA Langley Normal Incidence Tube for 20 acoustic liner candidates for the OTR application. The majority contain grooves at their surface, designed to minimize aerodynamic penalties caused by placing the liner in close proximity to the fan rotor tips. The intent is to assess the acoustic properties of each liner configuration, and in particular to assess the effects of including the grooves on the overall acoustic performance. An additional intent of this paper is to provide documentation regarding recent enhancements to the NASA Langley Normal Incidence Tube.

Jones, Michael G↗

NASA NTRS2019

Overview of the Main Propulsion System for a Nuclear Thermal Propulsion Flight Demonstrator

A demonstration of a Nuclear Thermal Propulsion (NTP) engine has not been conducted in over 50 years. Several tests were conducted during the NERVA program but no NTP engine was ever flown in space. In the last several years there has been a considerable amount of conceptual design work on NTP engines conducted. With the prospect of human Mars missions in the 2030’s there has been a renewed interest in NTP engines. A concept design study was conducted with the intent to design 2 flight demonstrator vehicles that would buy down programmatic and technical risks associated with launching and operating nuclear reactors in space. The intent of the first demonstrator mission would be to employ a simplified NTP engine and buy down programmatic risks whereas the second demonstrator would buy down technical risks with a NTP engine designed to be similar to an operational NTP model. The results of the study showed that a simplified NTP engine demonstrator could be feasibly built and flown in the near term with mostly high TRL, commercial off-the-shelf components.

Simpson, S. P.↗

NASA NTRS2020

A Systems Analysis Approach to Understanding the Physiological Adaptation to Spaceflight

This book is a summary of interdisciplinary research (physiology, space medicine, engineering, computer science, mathematics) that spans two decades (1972-1992). The research was an attempt to use systems analysis, mathematical modeling, computer simulations, and database systems to integrate the biomedical spaceflight data that was being collected during this period. The goal of the effort was to achieve a better understanding of the human physiological response to short-term and long-term space travel. The activity was primarily devoted to analyzing the biomedical results of Skylab (1973-74), a series of three space missions which is still ranked as the most comprehensive of all long-term biomedical space studies to date. This work was begun as a coordinated effort between the National Aeronautics and Space Administration (Johnson Space Center) and the General Electric Company’s Space Division (Houston, TX). It was the intent that this multidisciplined, integrative approach could reveal aspects of the then-new science of microgravity adaptation that were not obvious by adhering to the traditional methodology of examining each organ system in isolation. Some joint work with the Russians, including the Apollo-Soyez test project and a joint bedrest study was also supported during this period. In the 1980’s the systems analysis group’s effort was redirected to support the science management of human and animal experiments on the Space Shuttle. A few examples from this era are also included in the book. Parts of this work have been published elsewhere, presented at technical meetings, and documented in reports with limited distribution. These publications will be referenced throughout the text and the interested reader is advised to use these as resource material where additional details are desired. The intent of this book is not to reproduce these documents but rather to present a coherent view of the integrative analysis under one cover. This volume contains the first detailed publication (other than in internal reports) of an extensive metabolic balance analysis of Skylab data, the development and validation of the “Whole-Body Algorithm,” and simulation studies of diverse hypogravic environments. An analysis of cardiovascular deconditioning and a description of the calcium regulatory model are also new. A long period has passed between the completion of the main body of work represented in this book and its publication in this form. It was inevitable that new research efforts would lead to developments related to the spaceflight problems addressed and thereby make some of our biomedical conclusions obsolete. Although in some cases reference to more recent work have been included, for the most part this book should be considered an historical summary demonstrating the approach and utility of systems analysis and computer modeling in the NASA Life Sciences program at the time the studies were conducted.

Leonard, Joel I.↗

NASA NTRS2020

Tactical Separation and Safety Alerting System for Terminal Airspace

Provision of tactical alerts to aid air traffic controllers in providing separation assurance in terminal airspace is hindered by the complexity of the airspace, its operations, and flight procedures. A prototype automation system is studied that provides controllers with both separation and safety alerts based on or derived from the separation standard for terminal airspace. The system models flight trajectories heuristically, with use of merged intent information from readily available sources: area navigation departure procedures, flight-plan routes, and arrival nominal interior routes used in terminal automation systems. Flight vertical intent is modeled according to standard procedural restrictions except when superseded by controller-issued altitude clearances. Importantly, flight trajectories are modeled for all aircraft, including those conducting visual approaches. New safety-alert thresholds for aircraft conducting visual approaches are studied. Performance of the system is evaluated through fast-time playback of recorded air traffic data from high-fidelity Human-In-The-Loop simulations and real-world operations in two Terminal Radar Approach Control facilities. The prototype system is found to produce a false-alert rate of 8% for separation alerts. The number and validity of safety alerts are studied by comparing with the current Conflict Alert system, showing that the false alerts of Conflict Alert are at 85% and they are avoided in the prototype system.

Air Traffic Management↗