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At least 199 records · Page 11

Mechanisms of nitrogen retention in forest ecosystems - A field experiment

Intensive forest management led to elevated losses of nitrogen from a recently harvested loblolly pine plantation in North Carolina. Measurements of nitrogen-15 retention in the field demonstrated that microbial uptake of nitrogen during the decomposition of residual organic material was the most important process retaining nitrogen. Management practices that remove this material cause increased losses of nitrogen to aquatic ecosystems and the atmosphere.

Vitousek, P. M.↗

Heat pipes for terrestrial applications in dehumidification systems

A novel application of heat pipes which greatly enhances dehumidification performance of air-conditioning systems is presented. When an air-to-air heat pipe heat exchanger is placed between the warm return air and cold supply air streams of an air conditioner, heat is efficiently transferred from the return air to the supply air. As the warm return air precools during this process, it moves closer to its dew-point temperature. Therefore, the cooling system works less to remove moisture. This paper discusses the concept, its benefits, the challenges of incorporating heat pipes in an air-conditioning system, and the preliminary results from a field demonstration of an industrial application.

Khattar, Mukesh K.↗

A Science Rationale for Mobility in Planetary Environments

For the last several decades, the Committee on Planetary and Lunar Exploration (COMPLEX) has advocated a systematic approach to exploration of the solar system; that is, the information and understanding resulting from one mission provide the scientific foundations that motivate subsequent, more elaborate investigations. COMPLEX's 1994 report, An Integrated Strategy for the Planetary Sciences: 1995-2010,1 advocated an approach to planetary studies emphasizing "hypothesizing and comprehending" rather than "cataloging and categorizing." More recently, NASA reports, including The Space Science Enterprise Strategic Plan2 and, in particular, Mission to the Solar System: Exploration and Discovery-A Mission and Technology Roadmap,3 have outlined comprehensive plans for planetary exploration during the next several decades. The missions outlined in these plans are both generally consistent with the priorities outlined in the Integrated Strategy and other NRC reports,4-5 and are replete with examples of devices embodying some degree of mobility in the form of rovers, robotic arms, and the like. Because the change in focus of planetary studies called for in the Integrated Strategy appears to require an evolutionary change in the technical means by which solar system exploration missions are conducted, the Space Studies Board charged COMPLEX to review the science that can be uniquely addressed by mobility in planetary environments. In particular, COMPLEX was asked to address the following questions: (1) What are the practical methods for achieving mobility? (2) For surface missions, what are the associated needs for sample acquisition? (3) What is the state of technology for planetary mobility in the United States and elsewhere, and what are the key requirements for technology development? (4) What terrestrial field demonstrations are required prior to spaceflight missions?

Source record↗

Enhanced Airport Capacity Through Safe, Dynamic Reductions in Aircraft Separation: NASA's Aircraft VOrtex Spacing System (AVOSS)

An aspect of airport terminal operations that holds potential for efficiency improvements is the separation criteria applied to aircraft for wake vortex avoidance. These criteria evolved to represent safe spacing under weather conditions conducive to the longest wake hazards, and are consequently overly conservative during a significant portion of operations. Under many ambient conditions, such as moderate crosswinds or turbulence, wake hazard durations are substantially reduced. To realize this reduction NASA has developed a proof-of-concept Aircraft Vortex Spacing System (AVOSS). Successfully operated in a real-time field demonstration during July 2000 at the Dallas Ft. Worth International Airport, AVOSS is a novel integration of weather sensors, wake sensors, and analytical wake prediction algorithms. Gains in airport throughput using AVOSS spacing as compared to the current criteria averaged 6%, with peak values approaching the theoretical maximum of 16%. The average throughput gain translates to 15-40% reductions in delay when applied to realistic capacity ratios at major airports.

OConnor, Cornelius J.↗

Passive Microwave Studies of Atmospheric Precipitation and State

The principal contributions of this research on novel passive microwave spectral techniques are in the areas of: (1) global precipitation mapping using the opaque spectral bands on research and operational weather satellites, (2) development and analysis of extensive aircraft observational imaging data sets obtained using the MIT instrument NAST-M near 54 and 118 GHz over hurricanes and weather ranging from tropical to polar; simultaneous data from the 8500-channel infrared spectrometer NAST-I was obtained and analyzed separately, (3) estimation of hydrometeor diameters in cell tops using data from aircraft and spacecraft, (4) continued improvement of expressions for atmospheric transmittance at millimeter and sub-millimeter wavelengths, (5) development and airborne use of spectrometers operating near 183- and 425-GHz bands, appropriate to practical systems in geosynchronous orbit, and (6) preliminary studies of the design and performance of future geosynchronous microwave sounders for temperature and humidity profiles and for continuous monitoring of regional precipitation through most clouds. This work was a natural extension of work under NASA Grant NAG5-2545 and its predecessors. This earlier work had developed improved airborne imaging microwave spectrometers and had shown their sensitivity to precipitation altitude and character. They also had prepared the foundations for precipitation estimation using the opaque microwave bands. The field demonstration and improvement of these capabilities was then a central part of the present research reported here, during which period the first AMSU data became available and several hurricanes were overflown by NAST-M, yielding unique data about their microwave signatures. This present work has in turn helped lay the foundation for future progress in incorporating the opaque microwave channels in systems for climatologically precise global precipitation mapping from current and future operational satellites. Extension of these techniques to global snowfall mapping, even over ice and snow, is one such opportunity signaled by this research.

Staelin, David H.↗

Special Issue: 4th International Workshop on Space Radiation (IWSRR)

This special issue of the journal "Radiation and Environmental Biophysics" contains 20 peer-reviewed papers contributed by leading space radiation researcher's world-wide attending the 4th IWSRR. Manuscripts cover a broad range of topics ranging from radiation environments and transport in shielding and planetary surfaces to new results in understanding the biological effects of protons and high-charge and energy (HZE) nuclei on the risk of cancer, and degenerative diseases such as central nervous system effects, heart disease, and cataracts. The issue provides a snapshot of the state-of-the-art of the research in this field, demonstrating both the important results gathered in the past few years with experiments at accelerators, and the need for more research to quantify the risk and develop countermeasures.

Cucinotta, Francis A.↗

Chaotic Motion of Relativistic Electrons Driven by Whistler Waves

Canonical equations governing an electron motion in electromagnetic field of the whistler mode waves propagating along the direction of an ambient magnetic field are derived. The physical processes on which the equations of motion are based .are identified. It is shown that relativistic electrons interacting with these fields demonstrate chaotic motion, which is accompanied by the particle stochastic heating and significant pitch angle diffusion. Evolution of distribution functions is described by the Fokker-Planck-Kolmogorov equations. It is shown that the whistler mode waves could provide a viable mechanism for stochastic energization of electrons with energies up to 50 MeV in the Jovian magnetosphere.

Khazanov, G. V.↗

Herschel-ATLAS: Dust Temperature and Redshift Distribution of SPIRE and PACS Detected Sources Using Submillimetre Colours

We present colour-colour diagrams of detected sources in the Herschel-ATLAS Science Demonstration Field from 100 to 500/microns using both PACS and SPIRE. We fit isothermal modified-blackbody spectral energy distribution (SED) models in order to extract the dust temperature of sources with counterparts in GAMA or SDSS with either a spectroscopic or a photometric redshift. For a subsample of 331 sources detected in at least three FIR bands with significance greater than 30 sigma, we find an average dust temperature of (28 plus or minus 8)K. For sources with no known redshifts, we populate the colour-colour diagram with a large number of SEDs generated with a broad range of dust temperatures and emissivity parameters and compare to colours of observed sources to establish the redshift distribution of those samples. For another subsample of 1686 sources with fluxes above 35 mJy at 350 microns and detected at 250 and 500 microns with a significance greater than 3sigma, we find an average redshift of 2.2 plus or minus 0.6.

Amblard, A.↗

Robust and Opportunistic Autonomous Science for a Potential Titan Aerobot

We are developing onboard planning and execution technologies to provide robust and opportunistic mission operations for a potential Titan aerobot. Aerobot have the potential for collecting a vast amount of high priority science data. However, to be effective, an aerobot must address several challenges including communication constraints, extended periods without contact with Earth, uncertain and changing environmental conditions, maneuverability constraints and potentially short-lived science opportunities. We are developing the AerOASIS system to develop and test technology to support autonomous science operations for a potential Titan Aerobot. The planning and execution component of AerOASIS is able to generate mission operations plans that achieve science and engineering objectives while respecting mission and resource constraints as well as adapting the plan to respond to new science opportunities. Our technology leverages prior work on the OASIS system for autonomous rover exploration. In this paper we describe how the OASIS planning component was adapted to address the unique challenges of a Titan Aerobot and we describe a field demonstration of the system with the JPL prototype aerobot.

autonomous science↗

Using Analog Field Tests To Link and Prepare Science and In-Situ Resource Utilization for Future Space Missions

A major goal of NASA s human exploration program is to learn how to use the resources of space, known as In-Situ Resource Utilization (ISRU), to lower the cost and risk of human space exploration. Successful implementation of ISRU requires detailed knowledge of surface and subsurface materials, minerals, and volatiles that may be present. This same information is required to better understand the physical and geologic composition, structure, origin, and evolution of the Moon, Mars, and other extraterrestrial bodies of interest. It is also important to recognize that while ISRU and science objectives may be similar, the desired method or hardware to achieve the information desired may be drastically different. One method to promote understanding, coordination, and joint development of instruments and operations between Science and ISRU is the use of analog field demonstrations.

Sanders, Gerald B.↗

Boudreaux the Robot (a.k.a. EVA Robotic Assistant)

The EVA Robotic Assistant is a prototype for an autonomous rover designed to assist human astronauts. The primary focus of the research is to explore the interaction between humans and robots, particularly in extreme environments, and to develop a software infrastructure that could be applied to any type of assistant robot, whether for planetary exploration or orbital missions. This paper describes the background and current status of the project, the types of scenarios addressed in field demonstrations, the hardware and software that comprise the current prototype, and future research plans.

Shillcutt, Kimberly↗

360-Degree Visual Detection and Target Tracking on an Autonomous Surface Vehicle

This paper describes perception and planning systems of an autonomous sea surface vehicle (ASV) whose goal is to detect and track other vessels at medium to long ranges and execute responses to determine whether the vessel is adversarial. The Jet Propulsion Laboratory (JPL) has developed a tightly integrated system called CARACaS (Control Architecture for Robotic Agent Command and Sensing) that blends the sensing, planning, and behavior autonomy necessary for such missions. Two patrol scenarios are addressed here: one in which the ASV patrols a large harbor region and checks for vessels near a fixed asset on each pass and one in which the ASV circles a fixed asset and intercepts approaching vessels. This paper focuses on the ASV's central perception and situation awareness system, dubbed Surface Autonomous Visual Analysis and Tracking (SAVAnT), which receives images from an omnidirectional camera head, identifies objects of interest in these images, and probabilistically tracks the objects' presence over time, even as they may exist outside of the vehicle's sensor range. The integrated CARACaS/SAVAnT system has been implemented on U.S. Navy experimental ASVs and tested in on-water field demonstrations.

ASV (AUTONOMOUS SEA SURFACE VEHICLE)↗

Cost-Benefit Analysis For Alternative Low-Emission Surface Preparation/ Depainting Technologies for Structural Steel

Stennis Space Center (SSC), Kennedy Space Center (KSC) and Air Force Space Command (AFSPC) identified particulate emissions and waste generated from the depainting process of steel structures as hazardous materials to be eliminated or reduced. A Potential Alternatives Report, Potential Alternatives Report for Validation of Alternative Low Emission Surface Preparation/Depainting Technologies for Structural Steel, provided a technical analyses of identified alternatives to the current coating removal processes, criteria used to select alternatives for further analysis, and a list of those alternatives recommended for testing. The initial coating removal alternatives list was compiled using literature searches and stakeholder recommendations. The involved project participants initially considered approximately 13 alternatives. In late 2003, core project members selected the following depainting processes to be further evaluated: (1) Plastic Blast Media-Quickstrip(R)-A. (2) Hard Abrasive-Steel-Magic(R). (3) Sponge Blasting-Sponge-Jet(R). (4) Liquid Nitrogen-NItroJet(R). (5) Mechanical Removal with Vacuum Attachment-DESCO and OCM Clean-Air (6) Laser Coating Removal Alternatives were tested in accordance with the Joint Test Protocol for Validation of Alternative Low-Emission Surface Preparation/Depainting Technologies for Structural Steel, and the Field Evaluation Test Plan for Validation of Alternative Low-Emission Surface Preparation/Depainting Technologies for Structural Steel. Results of the testing are documented in the Joint Test Report. This Cost-Benefit Analysis (CBA) focuses on the three alternatives (Quickstrip(R)-A, SteelMagic (R), and Sponge-Jet(R)) that were considered viable alternatives for large area operations based on the results of the field demonstration and lab testing. This CBA was created to help participants determine if implementation of the candidate alternatives is economically justified. Each of the alternatives examined reduced Environmental Activity (EA) Costs-those costs associated with complying with environmental regulations. One alternative, Steel-Magic(R), also showed reduced Direct Costs and reduced total costs.

Lewis, Pattie↗

Simulations of Continuous Descent Operations with Arrival-management Automation and Mixed Flight-deck Interval Management Equipage

Air traffic management simulations conducted in the Airspace Operations Laboratory at NASA Ames Research Center have addressed the integration of trajectory-based arrival-management automation, controller tools, and Flight-Deck Interval Management avionics to enable Continuous Descent Operations (CDOs) during periods of sustained high traffic demand. The simulations are devoted to maturing the integrated system for field demonstration, and refining the controller tools, clearance phraseology, and procedures specified in the associated concept of operations. The results indicate a variety of factors impact the concept's safety and viability from a controller's perspective, including en-route preconditioning of arrival flows, useable clearance phraseology, and the characteristics of airspace, routes, and traffic-management methods in use at a particular site. Clear understanding of automation behavior and required shifts in roles and responsibilities is important for controller acceptance and realizing potential benefits. This paper discusses the simulations, drawing parallels with results from related European efforts. The most recent study found en-route controllers can effectively precondition arrival flows, which significantly improved route conformance during CDOs. Controllers found the tools acceptable, in line with previous studies.

arrival management↗

Simulation Evaluation of Controller-Managed Spacing Tools under Realistic Operational Conditions

Controller-Managed Spacing (CMS) tools have been developed to aid air traffic controllers in managing high volumes of arriving aircraft according to a schedule while enabling them to fly efficient descent profiles. The CMS tools are undergoing refinement in preparation for field demonstration as part of NASA's Air Traffic Management (ATM) Technology Demonstration-1 (ATD-1). System-level ATD-1 simulations have been conducted to quantify expected efficiency and capacity gains under realistic operational conditions. This paper presents simulation results with a focus on CMS-tool human factors. The results suggest experienced controllers new to the tools find them acceptable and can use them effectively in ATD-1 operations.

simulation↗

Overview of NASA's Air Traffic Management - eXploration (ATM-X) Project

Projected increases in new vehicle types, new missions, and the continual growth in traditional (e.g., airlines, general aviation) aviation will require changes to the current air traffic system, particularly to accommodate the desire of operators to be more involved in air traffic decisions. To address these challenges, the National Airspace System needs to undergo a transformation to a more scalable, flexible, user-focused system that addresses safety and security requirements and resiliency for current and new users. A system designed to integrate modular software services, provided by users, third parties and government for air traffic management functions, will be scalable and more easily allow modernization and for collaboration between users and service providers. ATM-X is responding to NASA's pivot towards integrating projected new, diverse entrants into the NAS, while also leveraging NASA's prior ATM achievements that continue to improve traditional airspace operations. This project is a two-phased approach to conduct research and focused evaluations to assess the feasibility of a service-based approach and to identify critical design considerations to enable airspace access for new entrants, integrated with current traditional operations. Phase 1 research will be conducted to determine what is needed to reach the ATM-X goals based on specific use-cases to enable large-scale, passenger-carrying Urban Air Mobility operations in a metroplex environment, and also to improve traditional operations in the Northeast Region leveraging mature NASA technologies. Some of these evaluations will be conducted in simulations and field activities. Phase 2 will build upon Phase 1 towards more defined, focused research and field demonstrations in real-world environments to integrate multiple elements of a scalable, service-based ATM-X concept.

air traffic management↗

Energy Efficient Large-Scale Storage of Liquid Hydrogen

The world’s largest liquid hydrogen storage tanks were constructed in the mid-1960sat the NASA Kennedy Space Center. These two vacuum-jacketed, perlite powder insulated tanks, still in service today, have 3,200 m3 of useable capacity. In 2018, construction began on an additional storage tank at Launch Complex 39B. This new tank will give an additional storage capacity of 4,700 m3 for a total on-site storage capacity of roughly 8,000 m3. NASA’s new Space Launch System (SLS) heavy lift rocket for the Artemis program includes an LH2tank that makes up the bulk of the vehicle, holding 2,033 m3 of LH2 in its 8.4-m diameter by40-m height. The new storage tank includes two new energy-efficient technologies: a glass bubbles insulation system in lieu of perlite, and an Integrated Refrigeration and Storage (IRAS)heat exchanger for controlled storage capability. The evacuated glass bubbles insulation system is based on the prior two decades of research to prove the thermal performance benefits as well as the mechanical and vacuum integrity; and has been shown to reduce LH2 boiloff by 46%versus perlite in field demonstrations. The IRAS capability is centered on a heat exchanger system that is built within the inner vessel to reject heat from the bulk liquid through the future implementation of an external helium refrigerator. Controlled storage via IRAS, when fully implemented, will provide full control of the ullage pressure, zero boiloff, and even production of densified LH2 pending its adoption on future launch vehicles. The design basics are described along with main construction and testing processes involved. The key features of the new technology items and implications on simplified operations and long-term energy savings are addressed

cryogenics↗

Energy Efficient Large-Scale Storage of Liquid Hydrogen

World’s largest LH2storage tanks constructed in mid-1960s at NASA/KSC. These vacuum-perlite insulated tanks, still in service today, are 3,200 m3capacity (ea.). In 2018, construction began on an additional 4,700 m3LH2storage tank at LC-39B•NASA’s new Space Launch System (SLS) heavy lift rocket for Artemis program holds 2,033 m3of LH2in its 8.4-m diameter by 40-m height. Two new energy-efficient technologies are included: glass bubbles insulation system and an Integrated Refrigeration and Storage (IRAS) heat exchanger for passive + active thermal control:•Evacuated glass bubbles insulation system has been shown to reduce LH2boiloff by 46% versus perlite in field demonstrations. Controlled storage via IRAS, when fully implemented, will provide full control of ullage pressure, zero boiloff, and even production of densified LH22CEC-2021

cryogenics↗