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NASA Technical Reports Server (NTRS) (664,209 recursos)
The NTRS is a valuable resource for students, educators, researchers, and the public for access to NASA's current and historical technical literature since it was first released in 1994. NTRS provides access to approximately 500K aerospace related citations, 90K full-text online documents, and 111K images and videos. NTRS numbers continues to grow over time as new scientific and technical information (STI) is created or funded by NASA. The type of information found in NTRS include: conference papers, images, journal articles, photos, meeting papers, movies, patents, research reports, and technical videos.

NASA Center for AeroSpace Information (CASI) (513,494) NIX Images (81,938)


Mostrando recursos 1 - 20 de 298,161

1. CLEANing the Reward: Counterfactual Actions to Remove Exploratory Action Noise in Multiagent Learning - Taylor, Mathew E.; Agogino, Adrian; HolmesParker, Chris; Tumer, Kagan
Learning in multiagent systems can be slow because agents must learn both how to behave in a complex environment and how to account for the actions of other agents. The inability of an agent to distinguish between the true environmental dynamics and those caused by the stochastic exploratory actions of other agents creates noise in each agent's reward signal. This learning noise can have unforeseen and often undesirable effects on the resultant system performance. We define such noise as exploratory action noise, demonstrate the critical impact it can have on the learning process in multiagent settings, and introduce a reward...

2. Generic Airspace Research Phase 5 Report - Peknik, Dan N.; Bridges, Wayne W.; Lee, Paul U.; Gujral, Vimmy; Preston, William E.; Mogford, Richard H.
Human-in-the-loop testing was completed to assess the subjective preferences, usage, and operational benefits of Integrated and Separated Controller Information Tools (CITs) in support of Generic Airspace Research. Participants controlled traffic in in a busy, high altitude sector with the aid of the CITs. When the participants were asked which CIT that they preferred to use, they overwhelmingly chose the integrated version of the CIT. The primary reason for this seemed to be that it allowed participants to remain focused on the traffic situation, whereas the Standalone CIT required them to focus their attention for short periods away from the radar...

3. UAS Conflict-Avoidance Using Multiagent RL with Abstract Strategy Type Communication - Knudson, Matt; Tumer, Kagan; Rebhuhn, Carrie
The use of unmanned aerial systems (UAS) in the national airspace is of growing interest to the research community. Safety and scalability of control algorithms are key to the successful integration of autonomous system into a human-populated airspace. In order to ensure safety while still maintaining efficient paths of travel, these algorithms must also accommodate heterogeneity of path strategies of its neighbors. We show that, using multiagent RL, we can improve the speed with which conflicts are resolved in cases with up to 80 aircraft within a section of the airspace. In addition, we show that the introduction of abstract...

4. Modeling Analysis for NASA GRC Vacuum Facility 5 Upgrade - Herman, D. A.; Yim, J. T.; Burt, J. M.
A model of the VF5 test facility at NASA Glenn Research Center was developed using the direct simulation Monte Carlo Hypersonic Aerothermodynamics Particle (HAP) code. The model results were compared to several cold flow and thruster hot fire cases. The main uncertainty in the model is the determination of the effective sticking coefficient -- which sets the pumping effectiveness of the cryopanels and oil diffusion pumps including baffle transmission. An effective sticking coefficient of 0.25 was found to provide generally good agreement with the experimental chamber pressure data. The model, which assumes a cold diffuse inflow, also fared satisfactorily in...

5. Probabilistic Modeling of the Renal Stone Formation Module - Jackson, Travis C.; Myers, Jerry G.; McRae, Michael P.; Goodenow, Debra A.; Best, Lauren M.
The Integrated Medical Model (IMM) is a probabilistic tool, used in mission planning decision making and medical systems risk assessments. The IMM project maintains a database of over 80 medical conditions that could occur during a spaceflight, documenting an incidence rate and end case scenarios for each. In some cases, where observational data are insufficient to adequately define the inflight medical risk, the IMM utilizes external probabilistic modules to model and estimate the event likelihoods. One such medical event of interest is an unpassed renal stone. Due to a high salt diet and high concentrations of calcium in the blood...

6. Extreme Environment Simulation - Current and New Capabilities to Simulate Venus and Other Planetary Bodies - Vento, Dan; Palinski, Timothy; Kremic, Tibor; Lalli, Nick
Science, technology, and planetary mission communities have a growing interest in components and systems that are capable of working in extreme (high) temperature and pressure conditions. Terrestrial applications range from scientific research, aerospace, defense, automotive systems, energy storage and power distribution, deep mining and others. As the target environments get increasingly extreme, capabilities to develop and test the sensors and systems designed to operate in such environments will be required. An application of particular importance to the planetary science community is the ability for a robotic lander to survive on the Venus surface where pressures are nearly 100 times that...

7. Numerical Analysis of a Rotating Detonation Engine in the Relative Reference Frame - Paxson, Daniel E.
A two-dimensional, computational fluid dynamic (CFD) simulation of a semi-idealized rotating detonation engine (RDE) is described. The simulation operates in the detonation frame of reference and utilizes a relatively coarse grid such that only the essential primary flow field structure is captured. This construction yields rapidly converging, steady solutions. Results from the simulation are compared to those from a more complex and refined code, and found to be in reasonable agreement. The performance impacts of several RDE design parameters are then examined. Finally, for a particular RDE configuration, it is found that direct performance comparison can be made with a...

8. Detection of the Impact of Ice Crystal Accretion in an Aircraft Engine Compression System During Dynamic Operation - Simon, Donald L.; Guo, Ten-Huei; May, Ryan D.
The accretion of ice in the compression system of commercial gas turbine engines operating in high ice water content conditions is a safety issue being studied by the aviation community. While most of the research focuses on the underlying physics of ice accretion and the meteorological conditions in which accretion can occur, a systems-level perspective on the topic lends itself to potential near-term operational improvements. Here a detection algorithm is developed which has the capability to detect the impact of ice accretion in the Low Pressure Compressor of an aircraft engine during steady flight as well as during changes in...

9. A Communication Architecture for an Advanced Extravehicular Mobile Unit - Oldham, Daniel R.; Ivancic, William D.; Sands, Obed S.; Klebau, Joseph M.; Bakula, Casey J.; Wright, Ted; Bradish, Martin A.
This document describes the communication architecture for the Power, Avionics and Software (PAS) 1.0 subsystem for the Advanced Extravehicular Mobility Unit (AEMU). The following systems are described in detail: Caution Warning and Control System, Informatics, Storage, Video, Audio, Communication, and Monitoring Test and Validation. This document also provides some background as well as the purpose and goals of the PAS subsystem being developed at Glenn Research Center (GRC).

10. Space Link Extension Protocol Emulation for High-Throughput, High-Latency Network Connections - Murawski, Robert; Tchorowski, Nicole
New space missions require higher data rates and new protocols to meet these requirements. These high data rate space communication links push the limitations of not only the space communication links, but of the ground communication networks and protocols which forward user data to remote ground stations (GS) for transmission. The Consultative Committee for Space Data Systems, (CCSDS) Space Link Extension (SLE) standard protocol is one protocol that has been proposed for use by the NASA Space Network (SN) Ground Segment Sustainment (SGSS) program. New protocol implementations must be carefully tested to ensure that they provide the required functionality, especially...

11. The OSIRIS-Rex Asteroid Sample Return: Mission Operations Design - Gal-Edd, Jonathan; Cheuvront, Allan
The OSIRIS-REx mission employs a methodical, phased approach to ensure success in meeting the missions science requirements. OSIRIS-REx launches in September 2016, with a backup launch period occurring one year later. Sampling occurs in 2019. The departure burn from Bennu occurs in March 2021. On September 24, 2023, the SRC lands at the Utah Test and Training Range (UTTR). Stardust heritage procedures are followed to transport the SRC to Johnson Space Center, where the samples are removed and delivered to the OSIRIS-REx curation facility. After a six-month preliminary examination period the mission will produce a catalog of the returned sample,...

12. NASA Mars 2020 Rover Mission: New Frontiers in Science - Calle, Carlos I.
The Mars 2020 rover mission is the next step in NASAs robotic exploration of the red planet. The rover, based on the Mars Science Laboratory Curiosity rover now on Mars, will address key questions about the potential for life on Mars. The mission would also provide opportunities to gather knowledge and demonstrate technologies that address the challenges of future human expeditions to Mars.Like the Mars Science Laboratory rover, which has been exploring Mars since 2012, the Mars 2020 spacecraft will use a guided entry, descent, and landing system which includes a parachute, descent vehicle, and, during the provides the ability...

13. EVA Development and Verification Testing at NASA's Neutral Buoyancy Laboratory - Ney, Zane; Parazynski, Scott; Sipila, Stephanie; Marak, Ralph; Durkin, Robert; Jairala, Juniper; Prince, Angela; Thomason, Arthur
As an early step in preparing for future EVAs, astronauts perform neutral buoyancy testing to develop and verify EVA hardware and operations. To date, neutral buoyancy demonstrations at NASA JSCs Sonny Carter Training Facility have primarily evaluated assembly and maintenance tasks associated with several elements of the ISS. With the retirement of the Space Shuttle, completion of ISS assembly, and introduction of commercial participants for human transportation into space, evaluations at the NBL will take on a new focus. In this session, Juniper Jairala briefly discussed the design of the NBL and, in more detail, described the requirements and process...

14. Near-Earth Asteroids: Threats and Opportunities - Love, Stan
Love's presentation reviewed the basics of NEAs: how many there are, how likely they are to hit the Earth, ways to prevent a threatening asteroid from hitting us, and some thoughts on human exploration of these interesting objects.

15. Probiotics in the Space Food System: Delivery, Microgravity Effects, and the Potential Benefit to Crew Health - Ott, C. M.; Douglas, G. L.; Castro, S. L.
As mission distance and duration increase, the need grows for noninvasive disease prevention and immunomodulation, especially given the limited medical response capability expected for these missions and the immune dysregulation documented in crew. Additionally, changes in diet, lifestyle, antibiotic usage, and the environmental stresses during spaceflight may alter crewmembers' intestinal microbiome. The addition of probiotic bacteria to the space food system is expected to confer immunostimulatory benefits on crewmembers, with the potential to counteract the immune dysregulation that has been documented in spaceflight. Based on previous studies that demonstrated unique microbiological responses to the low shear environment of spaceflight, probiotic...

16. Risk of Oxidative Damage to Bone from Increased Iron Stores During Space Flight - Zwart, S. R.; Smith, S. M.
Iron stores are increased secondary to neocytolysis of red blood cells and a high dietary intake of iron during space flight. This raises concerns about the risk of excess iron causing oxidative damage in many tissues, including bone. Biomarkers of iron status, oxidative damage, and bone resorption during space flight were analyzed for 23 (16 M/7 F) International Space Station crewmembers as part of the Nutrition SMO project. Up to 5 in-flight blood samples and 24-h urine pools were collected over the course of the 4-6 month missions. Serum iron increased slightly during space flight and was decreased at landing...

17. Bone Metabolism on ISS Missions - Heer, M. A.; Zwart, S. R.; Smith, S. M.; Shackelford, L. C.
Spaceflight-induced bone loss is associated with increased bone resorption (1, 2), and either unchanged or decreased rates of bone formation. Resistive exercise had been proposed as a countermeasure, and data from bed rest supported this concept (3). An interim resistive exercise device (iRED) was flown for early ISS crews. Unfortunately, the iRED provided no greater bone protection than on missions where only aerobic and muscular endurance exercises were available (4, 5). In 2008, the Advanced Resistive Exercise Device (ARED), a more robust device with much greater resistance capability, (6, 7) was launched to the ISS. Astronauts who had access to...

18. Using Tests Designed to Measure Individual Sensorimotor Subsystem Perfomance to Predict Locomotor Adaptability - Guined, J. R.; Mulavara, A. P.; Gadd, N. E.; Stepanyan, V.; Peters, B. T.; DeDios, Y. E.; Batson, C. D.; Caldwell, E. E.; Szecsy, D. L.; Seidler, R. D.; Bloomberg, J. J.
Astronauts experience sensorimotor disturbances during the initial exposure to microgravity and during the readapation phase following a return to a gravitational environment. These alterations may lead to disruption in the ability to perform mission critical functions during and after these gravitational transitions. Astronauts show significant inter-subject variation in adaptive capability following gravitational transitions. The way each individual's brain synthesizes the available visual, vestibular and somatosensory information is likely the basis for much of the variation. Identifying the presence of biases in each person's use of information available from these sensorimotor subsystems and relating it to their ability to adapt to...

19. Assessing the Effect of Spaceflight on the Propensity for Astronauts to Develop Disk Herniation - Mendez, C. M.; Feiveson, A. H.; Somers, J. T.
BACKGROUND: A previous study [1] reported that the instantaneous risk of developing a Herniated Nucleus Pulposus (HNP) was higher in astronauts who had flown at least one mission, as compared with those in the corps who had not yet flown. However, the study only analyzed time to HNP after the first mission (if any) and did not account for the possible effects of multiple missions. While many HNP's occurred well into astronauts' careers or in some cases years after retirement, the higher incidence of HNPs relatively soon after completion of space missions appears to indicate that spaceflight may lead to...

20. Pharmacokinetic Modeling of Intranasal Scopolamine in Plasma Saliva and Urine - Chow, D. S. L.; Putcha, L.; Tam, V.; Wu, L.
An intranasal gel formulation of scopolamine (INSCOP) was developed for the treatment of Space Motion Sickness. The bioavailability and pharmacokinetics (PK) were evaluated under the Food and Drug Administration guidelines for clinical trials for an Investigative New Drug (IND). The aim of this project was to develop a PK model that can predict the relationship between plasma, saliva and urinary scopolamine concentrations using data collected from the IND clinical trial with INSCOP. METHODS: Twelve healthy human subjects were administered three dose levels (0.1, 0.2 and 0.4 mg) of INSCOP. Serial blood, saliva and urine samples were collected between 5 min...

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