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NASA NTRS1986

Paleosols and the chemical evolution of the atmosphere

The chemistry and mineralogy of soils reflects the chemistry of the atmosphere below which they develop. Today the presence of a cover of land plants can obscure the signature of a highly oxidizing atmosphere. Prior to the advent of higher land plants ca. 400 m.y. ago the obscuring effect of a biological interface should have been minor. It can be shown that under such conditions the behavior of ferrous iron during weathering depends on the relationship between the ratio of the net concentration of oxidants to the concentration of acids in rainwater, and on the ratio of the oxygen demand to the acid demand for complete weathering of the parent rock. An analysis of the behavior of iron in some 15 paleosols between 1.0 and 2.9 b.y. in age showed some time ago that iron was retained, or largely retained, in paleosols developed on rocks with a low ratio of oxidant demand to acid demand (R value) and was lost from paleosols with a high R value. The results indicate that between 1.1 and 2.9 b.y.b.p. the ratio of the net concentration of oxidants to CO2 in rainwater was less than ca. 1/600 of the present-day value. Work during the past year has sought to extend the data base for paleosols and to define more precisely the relationships between the composition of paleosols and the chemistry of the atmosphere below which they developed.

Holland, H. D.↗

NASA NTRS1986

Communications platform payload definition study

Large geostationary communications platforms were investigated in a number of studies since 1974 as a possible means to more effectively utilize the geostationary arc and electromagnetic spectrum and to reduce overall satellite communications system costs. The commercial feasibility of various communications platform payload concepts circa 1998 was addressed. Promising payload concepts were defined, recurring costs were estimated, and critical technologies needed to enable eventual commercialization were identified. Ten communications service aggregation scenarios describing potential groupings of service were developed for a range of conditions. Payload concepts were defined for four of these scenarios: (1) Land Mobile Satellite Service (LMSS) meets 100% of Contiguous United States (CONUS) plus Canada demand with a single platform; (2) Fixed Satellite Service (FSS) (trunking + Customer Premises Service (CPS)), meet 20% of CONUS demand;(3) FSS (trunking + CPS + video distribution), 10 to 13% of CONUS demand; and (4) FSS (20% of demand) + Inter Satellite Links (ISL) + Tracking and Data Relay Satellite System (TDRSS)/Tracking and Data Acquisition System (TDAS) Data Distribution.

Clopp, H. W.↗

NASA NTRS1986

Communications platform payload definition study, executive summary

Large geostationary communications platforms have been investigated in a number of studies since 1974 as a possible means to more effectively utilize the geostationary orbital arc and electromagnetic spectrum and to reduce overall satellite communications system costs. This NASA Lewis sponsored study addresses the commercial feasibility of various communications platform payload concepts circa 1998. It defines promising payload concepts, estimates recurring costs and identifies critical technologies needed to permit eventual commercialization. Ten communications service aggregation scenarios describing potential groupings of services were developed for a range of conditions. Payload concepts were defined for four of these scenarios: (1) Land Mobile Satellite Service (LMSS), meet 100% of CONUS plus Canada demand with a single platform; (2) Fixed Satellite Service (FSS) (Trunking + Customer Premises Service (CPS), meet 20% of CONUS demands; (3) FSS (Trunking + video distribution), 10 to 13% of CONUS demand; and (4) FSS (20% of demand) + Inter Satellite Links (ISL) + TDRSS/TDAS Data Distribution.

Clopp, H. W.↗

NASA NTRS1993

Liquid metal drop ejection

The aim of this project was to demonstrate the possibility of ejecting liquid metals using drop on demand printing technology. The plan was to make transducers for operation in the 100 MHz frequency range and to use these transducers to demonstrate the ability to eject drops of liquid metals such as gallium. Two transducers were made by indium bonding piezoelectric lithium niobate to quartz buffer rods. The lithium niobate plates were thinned by mechanical polishing to a thickness of 37 microns for operation at 100 MHz. Hemispherical lenses were polished in the opposite ends of the buffer rods. The lenses, which focus the sound waves in the liquid metal, had an F-number equals 1. A mechanical housing was made to hold the transducers and to allow precise control over the liquid level above the lens. We started by demonstrating the ability to eject drops of water on demand. The drops of water had a diameter of 15 microns which corresponds to the wavelength of the sound wave in the water. A videotape of this ejection was made. We then used a mixture of Gallium and Indium (used to lower the melting temperature of the Gallium) to demonstrate the ejection of liquid metal drops. This proved to be difficult because of the oxide skin which forms on the surface of the liquid. In some instances, we were able to eject metal drops, however, this was not consistent and reproducible. An experiment was set up at NASA-Lewis to stabilize the process of drop on demand liquid metal ejection. The object was to place the transducer and liquid metal in a vacuum station so that no oxide would form on the surface. We were successful in demonstrating that liquid metals could be ejected on demand and that this technology could be used for making sheet metal in space.

Khuri-Yakub, B. T.↗

NASA NTRS1993

Predicting scheduling success

This paper provides an analytical formulation to predict scheduling success for a class of problems frequently referred to as activity scheduling. Space Network communications scheduling is an example of activity scheduling. The principal assumption is that the activity start times are randomly distributed over the available time in the time line. The formulation makes it possible to estimate how much of the demand can be scheduled as a function of the demand, number of resources, activity duration, and activity flexibility. The paper includes computed results for a variety of resource and demand conditions. The results demonstrate that even with highly flexible activities, it is difficult to schedule demand greater than 60 percent of resources without the use of optimization and conflict resolution capabilities in the scheduling system.

Messing, Fredric↗

NASA NTRS1993

Interworking and integration of the Inmarsat Standard-M with Pan-European GSM system

The market demand on mobile telephone communications has been increasing since the introduction of the cellular mobile telephone systems about twelve years ago. In Europe, projections indicate a demand of about 17 million subscribers for a fully deployed Pan European system. The Pan-European GSM system is to harmonize the growth of the terrestrial mobile system. Studies conducted by the European Space Agency (ESA) indicate that even with 60-70 percent of the area being covered by the GSM, a significant traffic demand (voice and data) will still exist for areas not covered by the terrestrial systems. This demand could be satisfied by a land mobile satellite system. The satellite system is therefore seen in a complementary role rather than in competition with the terrestrial system in an integrated telecommunications network. One possible scenario may be that initially the satellite system provides services to the rural areas together with areas still not covered by the GSM system. This service area is then gradually diminished as the terrestrial system expands until an optimum point is reached where the systems co-exist optimally. The objective of this paper is to investigate the possibility of integration of a space based system, in this case Inmarsat Standard-M, with the GSM (Global System for Mobile communications). One very important advantage of incorporating GSM services in Standard-M is that it will be feasible to extend the GSM services economically worldwide, not only to land mobiles but also to aeronautical and maritime mobiles.

Tafazolli, R.↗

NASA NTRS1997

Operational Issues: What Science in Available?

Flight/duty/rest considerations involve two highly complex factors: the diverse demands of aviation operations and human physiology (especially sleep and circadian rhythms). Several core operational issues related to fatigue have been identified, such as minimum rest requirements, duty length, flight time considerations, crossing multiple time zones, and night flying. Operations also can involve on-call reserve status and callout, delays due to unforeseen circumstances (e.g., weather, mechanical), and on-demand flights. Over 40 years of scientific research is now available to apply to these complex issues of flight/duty/rest requirements. This research involves controlled 'laboratory studies, simulations, and data collected during regular flight operations. When flight/duty/rest requirements are determined they are typically based on a variety of considerations, such as operational demand, safety, economic, etc. Rarely has the available, state-of-the-art science been a consideration along with these other factors when determining flight/duty/rest requirements. While the complexity of the operational demand and human physiology precludes an absolute solution, there is an opportunity to take full advantage of the current scientific data. Incorporating these data in a rational operational manner into flight/duty/rest requirements can improve flight crew performance, alertness, and ultimately, aviation safety.

Rosekind, Mark R.↗

NASA NTRS2002

The Integrated Air Transportation System Evaluation Tool

Throughout U.S. history, our nation has generally enjoyed exceptional economic growth, driven in part by transportation advancements. Looking forward 25 years, when the national highway and skyway systems are saturated, the nation faces new challenges in creating transportation-driven economic growth and wealth. To meet the national requirement for an improved air traffic management system, NASA developed the goal of tripling throughput over the next 20 years, in all weather conditions while maintaining safety. Analysis of the throughput goal has primarily focused on major airline operations, primarily through the hub and spoke system.However, many suggested concepts to increase throughput may operate outside the hub and spoke system. Examples of such concepts include the Small Aircraft Transportation System, civil tiltrotor, and improved rotorcraft. Proper assessment of the potential contribution of these technologies to the domestic air transportation system requires a modeling capability that includes the country's numerous smaller airports, acting as a fundamental component of the National Air space System, and the demand for such concepts and technologies. Under this task for NASA, the Logistics Management Institute developed higher fidelity demand models that capture the interdependence of short-haul air travel with other transportation modes and explicitly consider the costs of commercial air and other transport modes. To accomplish this work, we generated forecasts of the distribution of general aviation based aircraft and GA itinerant operations at each of nearly 3.000 airport based on changes in economic conditions and demographic trends. We also built modules that estimate the demand for travel by different modes, particularly auto, commercial air, and GA. We examined GA demand from two perspectives: top-down and bottom-up, described in detail.

Wingrove, Earl R., III↗

NASA NTRS1992

Modeling the effects of hypoxia on ATP turnover in exercising muscle

Most models of metabolic control concentrate on the regulation of ATP production and largely ignore the regulation of ATP demand. We describe a model, based on the results of Hogan et al. (J. Appl. Physiol. 73: 728-736, 1992), that incorporates the effects of ATP demand. The model is developed from the premise that a unique set of intracellular conditions can be measured at each level of ATP turnover and that this relationship is best described by energetic state. Current concepts suggest that cells are capable of maintaining oxygen consumption in the face of declines in the concentration of oxygen through compensatory changes in cellular metabolites. We show that these compensatory changes can cause significant declines in ATP demand and result in a decline in oxygen consumption and ATP turnover. Furthermore we find that hypoxia does not directly affect the rate of anaerobic ATP synthesis and associated lactate production. Rather, lactate production appears to be related to energetic state, whatever the PO2. The model is used to describe the interaction between ATP demand and ATP supply in determining final ATP turnover.

Non-NASA Center↗

NASA NTRS2007

Methane Hydrates: More Than a Viable Aviation Fuel Feedstock Option

Demand for hydrocarbon fuels is steadily increasing, and greenhouse gas emissions continue to rise unabated with the energy demand. Alternate fuels will be coming on line to meet that demand. This report examines the recovering of methane from methane hydrates for fuel to meet this demand rather than permitting its natural release into the environment, which will be detrimental to the planet. Some background on the nature, vast sizes, and stability of sedimentary and permafrost formations of hydrates are discussed. A few examples of the severe problems associated with methane recovery from these hydrates are presented along with the potential impact on the environment and coastal waters. Future availability of methane from hydrates may become an attractive option for aviation fueling, and so future aircraft design associated with methane fueling is considered.

Hendricks, Robert C.↗

NASA NTRS1990

Aircraft propeller control

In the invention, the speeds of both propellers in a counterrotating aircraft propeller pair are measured. Each speed is compared, using a feedback loop, with a demanded speed and, if actual speed does not equal demanded speed for either propeller, pitch of the proper propeller is changed in order to attain the demanded speed. A proportional/integral controller is used in the feedback loop. Further, phase of the propellers is measured and, if the phase does not equal a demanded phase, the speed of one propeller is changed, by changing pitch, until the proper phase is attained.

Day, Stanley G.↗

NASA NTRS2009

Halophytes, Algae, and Bacteria Food and Fuel Feedstocks

The constant, increasing demand for energy, freshwater, and food stresses our ability to meet these demands within reasonable cost and impact on climate while sustaining quality of life. This environmental Triangle of Conflicts between energy, food, and water--while provoked by anthropogenic monetary and power struggles--can be resolved through an anthropogenic paradigm shift in how we produce and use energy, water, and food. With world population (6.6 billion) projected to increase 40 percent in 40 to 60 yr, proper development of saline agriculture and aquaculture is required, as 43 percent of the Earth's landmass is arid or semi-arid and 97 percent of the Earth's water is seawater. In light of this, we seek fuel alternatives in plants that thrive in brackish and saltwater with the ability to survive in arid lands. The development and application of these plants (halophytes) become the primary focus. Herein we introduce some not-so-familiar halophytes and present a few of their benefits, cite a few research projects (including some on the alternatives algae and bacteria), and then set theoretical limits on biomass production followed by projections in terms of world energy demands. Based on diverse arid lands with a total size equivalent to the Sahara Desert (8.6(exp 8) ha, or 2.1(exp 9) acres), these projections show that halophyte agriculture and algae systems can provide for the projected world energy demand.

Hendricks, R. C.↗

NASA NTRS2009

Benefits Assessment of Algorithmically Combining Generic High Altitude Airspace Sectors

In today's air traffic control operations, sectors that have traffic demand below capacity are combined so that fewer controller teams are required to manage air traffic. Controllers in current operations are certified to control a group of six to eight sectors, known as an area of specialization. Sector combinations are restricted to occur within areas of specialization. Since there are few sector combination possibilities in each area of specialization, human supervisors can effectively make sector combination decisions. In the future, automation and procedures will allow any appropriately trained controller to control any of a large set of generic sectors. The primary benefit of this will be increased controller staffing flexibility. Generic sectors will also allow more options for combining sectors, making sector combination decisions difficult for human supervisors. A sector-combining algorithm can assist supervisors as they make generic sector combination decisions. A heuristic algorithm for combining under-utilized air space sectors to conserve air traffic control resources has been described and analyzed. Analysis of the algorithm and comparisons with operational sector combinations indicate that this algorithm could more efficiently utilize air traffic control resources than current sector combinations. This paper investigates the benefits of using the sector-combining algorithm proposed in previous research to combine high altitude generic airspace sectors. Simulations are conducted in which all the high altitude sectors in a center are allowed to combine, as will be possible in generic high altitude airspace. Furthermore, the algorithm is adjusted to use a version of the simplified dynamic density (SDD) workload metric that has been modified to account for workload reductions due to automatic handoffs and Automatic Dependent Surveillance Broadcast (ADS-B). This modified metric is referred to here as future simplified dynamic density (FSDD). Finally, traffic demand sets with increased air traffic demand are used in the simulations to capture the expected growth in air traffic demand by the mid-term.

Bloem, Michael↗

NASA NTRS2013

Data Mining for Understanding and Improving Decision-making Affecting Ground Delay Programs

Weather↗

NASA NTRS2013

Data Mining for Understanding and Impriving Decision-Making Affecting Ground Delay Programs

The continuous growth in the demand for air transportation results in an imbalance between airspace capacity and traffic demand. The airspace capacity of a region depends on the ability of the system to maintain safe separation between aircraft in the region. In addition to growing demand, the airspace capacity is severely limited by convective weather. During such conditions, traffic managers at the FAA's Air Traffic Control System Command Center (ATCSCC) and dispatchers at various Airlines' Operations Center (AOC) collaborate to mitigate the demand-capacity imbalance caused by weather. The end result is the implementation of a set of Traffic Flow Management (TFM) initiatives such as ground delay programs, reroute advisories, flow metering, and ground stops. Data Mining is the automated process of analyzing large sets of data and then extracting patterns in the data. Data mining tools are capable of predicting behaviors and future trends, allowing an organization to benefit from past experience in making knowledge-driven decisions. The work reported in this paper is focused on ground delay programs. Data mining algorithms have the potential to develop associations between weather patterns and the corresponding ground delay program responses. If successful, they can be used to improve and standardize TFM decision resulting in better predictability of traffic flows on days with reliable weather forecasts. The approach here seeks to develop a set of data mining and machine learning models and apply them to historical archives of weather observations and forecasts and TFM initiatives to determine the extent to which the theory can predict and explain the observed traffic flow behaviors.

data mining↗

NASA NTRS2013

Modeling Weather Impact on Airport Arrival Miles-in-Trail Restrictions

When the demand for either a region of airspace or an airport approaches or exceeds the available capacity, miles-in-trail (MIT) restrictions are the most frequently issued traffic management initiatives (TMIs) that are used to mitigate these imbalances. Miles-intrail operations require aircraft in a traffic stream to meet a specific inter-aircraft separation in exchange for maintaining a safe and orderly flow within the stream. This stream of aircraft can be departing an airport, over a common fix, through a sector, on a specific route or arriving at an airport. This study begins by providing a high-level overview of the distribution and causes of arrival MIT restrictions for the top ten airports in the United States. This is followed by an in-depth analysis of the frequency, duration and cause of MIT restrictions impacting the Hartsfield-Jackson Atlanta International Airport (ATL) from 2009 through 2011. Then, machine-learning methods for predicting (1) situations in which MIT restrictions for ATL arrivals are implemented under low demand scenarios, and (2) days in which a large number of MIT restrictions are required to properly manage and control ATL arrivals are presented. More specifically, these predictions were accomplished by using an ensemble of decision trees with Bootstrap aggregation (BDT) and supervised machine learning was used to train the BDT binary classification models. The models were subsequently validated using data cross validation methods. When predicting the occurrence of arrival MIT restrictions under low demand situations, the model was able to achieve over all accuracy rates ranging from 84% to 90%, with false alarm ratios ranging from 10% to 15%. In the second set of studies designed to predict days on which a high number of MIT restrictions were required, overall accuracy rates of 80% were achieved with false alarm ratios of 20%. Overall, the predictions proposed by the model give better MIT usage information than what has been currently provided under current day operations. Traffic flow managers can use these predictions to identify potential MIT restrictions to eliminate (e.g., those occurring during low arrival demand periods), and to determine the days in which a significant number of restrictions may be required

Operation↗

NASA NTRS2014

Temperature and Snow-Mediated Moisture Controls of Summer Photosynthetic Activity in Northern Terrestrial Ecosystems Between 1982 and 2011

Recent warming has stimulated the productivity of boreal and Arctic vegetation by reducing temperature limitations. However, several studies have hypothesized that warming may have also increased moisture limitations because of intensified summer drought severity. Establishing the connections between warming and drought stress has been difficult because soil moisture observations are scarce. Here we use recently developed gridded datasets of moisture variability to investigate the links between warming and changes in available soil moisture and summer vegetation photosynthetic activity at northern latitudes (greater than 45N) based on the Normalized Difference Vegetation Index (NDVI) since 1982. Moisture and temperature exert a significant influence on the inter-annual variability of summer NDVI over about 29% (mean r(sup 2) = 0.29 +/ 0.16) and 43% (mean r(sup 2 = 0.25 +/- 0.12) of the northern vegetated land, respectively. Rapid summer warming since the late 1980s (approximately 0.7deg C) has increased evapotranspiration demand and consequently summer drought severity, but contrary to earlier suggestions it has not changed the dominant climate controls of NDVI over time. Furthermore, changes in snow dynamics (accumulation and melting) appear to be more important than increased evaporative demand in controlling changes in summer soil moisture availability and NDVI in moisture-sensitive regions of the boreal forest. In boreal North America, forest NDVI declines are more consistent with reduced snowpack rather than with temperature-induced increases in evaporative demand as suggested in earlier studies. Moreover, summer NDVI variability over about 28% of the northern vegetated land is not significantly associated with moisture or temperature variability, yet most of this land shows increasing NDVI trends. These results suggest that changes in snow accumulation and melt, together with other possibly non-climatic factors are likely to play a significant role in modulating regional ecosystem responses to the projected warming and increase in evapotranspiration demand during the coming decades.

Snowpack↗

NASA NTRS2016

A Satellite Data-Driven, Client-Server Decision Support Application for Agricultural Water Resources Management

Water cycle extremes such as droughts and floods present a challenge for water managers and for policy makers responsible for the administration of water supplies in agricultural regions. In addition to the inherent uncertainties associated with forecasting extreme weather events, water planners need to anticipate water demands and water user behavior in a typical circumstances. This requires the use decision support systems capable of simulating agricultural water demand with the latest available data. Unfortunately, managers from local and regional agencies often use different datasets of variable quality, which complicates coordinated action. In previous work we have demonstrated novel methodologies to use satellite-based observational technologies, in conjunction with hydro-economic models and state of the art data assimilation methods, to enable robust regional assessment and prediction of drought impacts on agricultural production, water resources, and land allocation. These methods create an opportunity for new, cost-effective analysis tools to support policy and decision-making over large spatial extents. The methods can be driven with information from existing satellite-derived operational products, such as the Satellite Irrigation Management Support system (SIMS) operational over California, the Cropland Data Layer (CDL), and using a modified light-use efficiency algorithm to retrieve crop yield from the synergistic use of MODIS and Landsat imagery. Here we present an integration of this modeling framework in a client-server architecture based on the Hydra platform. Assimilation and processing of resource intensive remote sensing data, as well as hydrologic and other ancillary information occur on the server side. This information is processed and summarized as attributes in water demand nodes that are part of a vector description of the water distribution network. With this architecture, our decision support system becomes a light weight 'app' that connects to the server to retrieve the latest information regarding water demands, land use, yields and hydrologic information required to run different management scenarios. Furthermore, this architecture ensures all agencies and teams involved in water management use the same, up-to-date information in their simulations.

Agricultural↗