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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2000

Noise-Reduction Benefits Analyzed for Over-the-Wing-Mounted Advanced Turbofan Engines

As we look to the future, increasingly stringent civilian aviation noise regulations will require the design and manufacture of extremely quiet commercial aircraft. Also, the large fan diameters of modern engines with increasingly higher bypass ratios pose significant packaging and aircraft installation challenges. One design approach that addresses both of these challenges is to mount the engines above the wing. In addition to allowing the performance trend towards large diameters and high bypass ratio cycles to continue, this approach allows the wing to shield much of the engine noise from people on the ground. The Propulsion Systems Analysis Office at the NASA Glenn Research Center at Lewis Field conducted independent analytical research to estimate the noise reduction potential of mounting advanced turbofan engines above the wing. Certification noise predictions were made for a notional long-haul commercial quadjet transport. A large quad was chosen because, even under current regulations, such aircraft sometimes experience difficulty in complying with certification noise requirements with a substantial margin. Also, because of its long wing chords, a large airplane would receive the greatest advantage of any noise-shielding benefit.

Berton, Jeffrey J.↗
NASA NTRS1993

Next generation initiation techniques

Four-dimensional data assimilation strategies can generally be classified as either current or next generation, depending upon whether they are used operationally or not. Current-generation data-assimilation techniques are those that are presently used routinely in operational-forecasting or research applications. They can be classified into the following categories: intermittent assimilation, Newtonian relaxation, and physical initialization. It should be noted that these techniques are the subject of continued research, and their improvement will parallel the development of next generation techniques described by the other speakers. Next generation assimilation techniques are those that are under development but are not yet used operationally. Most of these procedures are derived from control theory or variational methods and primarily represent continuous assimilation approaches, in which the data and model dynamics are 'fitted' to each other in an optimal way. Another 'next generation' category is the initialization of convective-scale models. Intermittent assimilation systems use an objective analysis to combine all observations within a time window that is centered on the analysis time. Continuous first-generation assimilation systems are usually based on the Newtonian-relaxation or 'nudging' techniques. Physical initialization procedures generally involve the use of standard or nonstandard data to force some physical process in the model during an assimilation period. Under the topic of next-generation assimilation techniques, variational approaches are currently being actively developed. Variational approaches seek to minimize a cost or penalty function which measures a model's fit to observations, background fields and other imposed constraints. Alternatively, the Kalman filter technique, which is also under investigation as a data assimilation procedure for numerical weather prediction, can yield acceptable initial conditions for mesoscale models. The third kind of next-generation technique involves strategies to initialize convective scale (non-hydrostatic) models.

Warner, Tom↗
NASA NTRS2013

Evaluation of the Terminal Area Precision Scheduling and Spacing System for Performance-Based Navigation Arrivals

The growth of global demand for air transportation has put increasing strain on the nation's air traffic management system. To relieve this strain, the International Civil Aviation Organization has urged all nations to adopt Performance-Based Navigation (PBN), which can help to reduce air traffic congestion, decrease aviation fuel consumption, and protect the environment. NASA has developed a Terminal Area Precision Scheduling and Spacing (TAPSS) system that can support increased use of PBN during periods of high traffic, while supporting fuel-efficient, continuous descent approaches. In the original development of this system, arrival aircraft are assigned fuel-efficient Area Navigation (RNAV) Standard Terminal Arrival Routes before their initial descent from cruise, with routing defined to a specific runway. The system also determines precise schedules for these aircraft that facilitate continuous descent through the assigned routes. To meet these schedules, controllers are given a set of advisory tools to precisely control aircraft. The TAPSS system has been evaluated in a series of human-in-the-loop (HITL) air traffic simulations during 2010 and 2011. Results indicated increased airport arrival throughput up to 10 over current operations, and maintained fuel-efficient aircraft decent profiles from the initial descent to landing with reduced controller workload. This paper focuses on results from a joint NASA and FAA HITL simulation conducted in 2012. Due to the FAA rollout of the advance terminal area PBN procedures at mid-sized airports first, the TAPSS system was modified to manage arrival aircraft as they entered Terminal Radar Approach Control (TRACON). Dallas-Love Field airport (DAL) was selected by the FAA as a representative mid-sized airport within a constrained TRACON airspace due to the close proximity of a major airport, in this case Dallas-Ft Worth International Airport, one of the busiest in the world. To address this constraint, RNAV routes and Required Navigation Performance with the particular capability known as Radius-to-Fix (RNP-RF) approaches to a short final were used. The purpose of this simulation was to get feedback on how current operations could benefit with the TAPSS system and also to evaluate the efficacy of the advisory tools to support the broader use of PBN in the US National Airspace System. For this NASA-FAA joint experiment, an Air Traffic Control laboratory at NASA Ames was arranged to simulate arrivals into DAL in Instrument Meteorological Conditions utilizing parallel dependent approaches, with two feeder positions that handed off traffic to one final position. Four FAA controllers participated, alternately covering these three positions. All participants were Full-Performance Level terminal controllers and members of the National Air Traffic Controllers Association. During the simulation, PBN arrival operations were compared and contrasted in three conditions. They were the Baseline, where none of the TAPSS systems TRACON controller decision support advisories were provided, the Limited Advisories, reflecting the existing but dormant capabilities of the current terminal automation equipment with providing a subset of the TAPSS systems advisories; numerical delay, landing sequence, and runway assignment information, and the Full Advisories, with providing the following in addition to the ones in the Limited condition; trajectory slot markers, timelines of estimated times of arrivals and sched

Performance based navigation↗
NASA NTRS2020

The NASA MODIS-VIIRS Continuity Cloud Optical Properties Products

The NASA Aqua MODIS and Suomi National Polar-Orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite (VIIRS) climate data record continuity cloud properties products (CLDPROP) were publicly released in April 2019 with an update later that year (Version 1.1). These cloud products, having heritage with the NASA Moderate-resolution Imaging Spectroradiometer (MODIS) MOD06 cloud optical properties product and the NOAA GOES-R Algorithm Working Group (AWG) Cloud Height Algorithm (ACHA), represent an effort to bridge the multispectral imager records of NASA’s Earth Observing System (EOS) and NOAA’s current generation of operational weather satellites to achieve a continuous, multi-decadal climate data record for clouds that can extend well into the 2030s. CLDPROP offers a “continuity of approach,” applying common algorithms and ancillary datasets to both MODIS and VIIRS, including utilizing only a subset of spectral channels available on both sensors to help mitigate instrument differences. The initial release of the CLDPROP_MODIS and CLDPROP_VIIRS data records spans the SNPP observational record (2012-present). Here, we present an overview of the algorithms and an evaluation of the intersensor continuity of the core CLDPROP_MODIS and CLDPROP_VIIRS cloud optical property datasets, i.e., cloud thermodynamic phase, optical thickness, effective particle size, and derived water path. The evaluation includes analyses of pixel-level MODIS/VIIRS co-locations as well as spatial and temporal aggregated statistics, with a focus on identifying and understanding the root causes of individual dataset discontinuities. The results of this evaluation will inform future updates to the CLDPROP products and help scientific users determine the appropriate use of the product datasets for their specific needs.

satellite remote sensing↗
NASA NTRSDate not supplied

Having a Come-Apart: Lessons Learned from Additively Manufactured Hardware Failures

NASA has been engaged with additively manufactured (AM) process and component development since the 2000’s. AM offers various technical advantages, such as enhanced hardware design complexity, part consolidation, and processing of novel alloys in addition to programmatic advantages for reduction in processing time and cost. The focus of much of the AM development at NASA has been to mature the various processes, characterize material properties, develop standards, produce demonstrator parts, and integrate AM hardware in liquid rocket engines. These aspects have been demonstrated through process and design iterations using a methodical characterization, test-fail-fix cycles, as well as application and dissemination of lessons learned. In addition to these fundamental demonstrations of the AM process and hardware development, alloys that provide performance advantages in the high temperature and high-pressure environments have been matured for use in rocket engines. These environments are challenging for any alloy and any design, and the AM process is required to fully meet the intended design requirements. The importance of proper AM process was made evident in the failure of a Laser Powder Bed Fusion (L-PBF) copper-alloy combustion chamber during a hot-fire test due to a degraded material quality resulted from an AM process issue. The hot-fire test aimed to demonstrate high duty cycle under a risk-tolerant development project, where consequences of component failure would be minimal. However, the unintentional component failure emphasized the necessity of robust material characterization and rigorous process control procedures for the safe use of AM components in critical applications. In part, such concerns motivate the AM certification approach that NASA has recently adopted in NASA-STD-6030 “Additive Manufacturing Requirements for Spaceflight Systems”. This presentation provides an overview of the previously mentioned failure, a discussion on the evaluation of the failed chamber and supplemental chambers produced at the same time, a representative material samples that included intentional build witness lines, and a summary of the key results and recommendations from the evaluations. NASA continues to approach AM processes and designs with a level of risk and acceptance of failures that is appropriate for the project objectives, with the overall goal of safe implementation of AM technology and transferring AM technology into commercial space applications. The objective of this presentation is to provide awareness to the community working critical and non-critical AM components and the lessons learned on proper implementation of AM.

Additive Manufacturing↗
NASA NTRS2003

Simulated Fuel Usage for Drag Compensated Spacecraft in Low Earth Orbit

Atmospheric drag causes the greatest uncertainty in the spacecraft flight dynamics equation for spacecraft in Low Earth Orbit (LEO). The continuously varying atmospheric density levels require increased spacecraft tracking to accurately predict spacecraft location. In addition, periodic propulsive maneuvers must be designed and performed to counteract the effects of drag on the spacecraft orbit. If atmospheric drag effects can be continuously and autonomously counteracted through the use of a drag-free control system, they will essentially be eliminated from the spacecraft flight dynamics equation. The main perturbations on the spacecraft will then be those due to the Earth s gravitational field, which are easily predicted. Although theoretically beneficial from a flight dynamics perspective, the costs associated with drag-free control must be determined and weighed against those benefits before the feasibility of drag-free control of spacecraft in LEO can be determined. Through the use of a MATLAEV Satellite Tool Kit simulation, this paper attempts to quantify one such cost associated with drag-free control: the amount of fuel needed for continuous drag compensation as measured by cumulative orbital velocity changes, or AV. This AV cost can then be compared to the fuel required for more traditional, periodic orbit raising maneuvers of every two to four weeks. The simulation considers various sized spacecraft, as measured by the spacecraft ballistic coefficient, in circular orbits of various altitudes and inclinations. The time between orbit raising maneuvers is allowed to decrease until it approaches near continuous. In this manner, the trend in AV cost can be seen as drag compensation moves from periodic to near continuous.

Fleck, Melissa E.↗
NASA NTRS2001

Computer Simulation of the Forces Acting on a Submerged Polystyrene Probe as it Approaches the Succinonitrile Melt-Solid Interface

A Modeling approach to simulate both mesoscale and microscopic forces acting in a typical AFM experiment is presented. A mesoscale level interaction between the cantilever tip and the sample surface is primarily described by the balance of attractive Van der Waals and repulsive forces. Ultimately, the goal is to measure the forces between a particle and the crystal-melt interface. Two modes of AFM operation are considered in this paper - a stationary and a "tapping" one. The continuous mechanics approach to model tip-surface interaction is presented. At microscopic levels, tip contamination and details of tip-surface interaction are modeled using a molecular dynamics approach for the case of polystyrene - succinonitrile contact. Integration of the mesoscale model with a molecular dynamic model is discussed.

Bune, Andris V.↗
NASA NTRS1987

New approaches to some methodological problems of meteor science

Several low cost approaches to continuous radioscatter monitoring of the incoming meteor flux are described. Preliminary experiments were attempted using standard time frequency stations WWVH and CHU (on frequencies near 15 MHz) during nighttime hours. Around-the-clock monitoring using the international standard aeronautical beacon frequency of 75 MHz was also attempted. The techniques are simple and can be managed routinely by amateur astronomers with relatively little technical expertise. Time series analysis can now be performed using relatively inexpensive microcomputers. Several algorithmic approaches to the analysis of meteor rates are discussed. Methods of obtaining optimal filter predictions of future meteor flux are also discussed.

Meisel, David D.↗
NASA NTRS2018

Assurance of Model-Based Fault Diagnosis

Autonomy is an increasingly important technology for robotic scientific and commercial spacecraft. An important motivation for developing onboard autonomy is to enable quick response to dynamic environment and situations, including fault conditions that a spacecraft may encounter. The reliability of such autonomous capabilities depends on the quality of their knowledge of a spacecraft’s health state. Model-based approaches to fault management, i.e. model-based fault diagnosis (MBFD), is one approach to continuously verify correct behavior in addition to diagnosing symptoms to estimate the spacecraft’s health state. The proper functioning of MBFD is dependent on 1) the quality of the model that is analyzed and compared to the outputs of onboard sensors to estimate the system’s health state, and 2) the correct functioning of the diagnosis engine that interrogates the model and compares its analysis to observed system behavior. We are currently developing Verification and Validation (V&V) approaches to provide the necessary confidence that MBFD systems are correctly estimating the health of on-board spacecraft components and systems. Our work is intended to narrow the gap between the rapidly maturing field of ModelBased System Engineering (including MBFD) and the less-well understood area of identifying and applying appropriate V&V techniques to MBFD. Our effort is investigating three areas: 1) developing V&V techniques for the diagnostic model, 2) developing V&V techniques for the diagnostic engine in isolation, and 3) developing V&V techniques for the diagnostic engine and model in combination. This paper describes the work we have completed in the first area. We describe our approach to selecting a system to be represented by a model, the approach to modeling the system, the verification approach we developed for the model, and the results of the verification activity. We conclude with a description of the work remaining in the last two areas, which will be addressed over the next two years.

Chung, Seung↗
NASA NTRS2004

Research and Development at NASA

The Vision for Space Exploration marks the next segment of NASA's continuing journey to find answers to compelling questions about the origins of the solar system, the existence of life beyond Earth, and the ability of humankind to live on other worlds. The success of the Vision relies upon the ongoing research and development activities conducted at each of NASA's 10 field centers. In an effort to promote synergy across NASA as it works to meet its long-term goals, the Agency restructured its Strategic Enterprises into four Mission Directorates that align with the Vision. Consisting of Exploration Systems, Space Operations, Science, and Aeronautics Research, these directorates provide NASA Headquarters and the field centers with a streamlined approach to continue exploration both in space and on Earth.

Source record↗
NASA NTRS2012

Flying Schedule-Matching Descents to Explore Flight Crews' Perceptions of Their Load and Task Feasibility

Multiple studies have investigated the development and use of ground-based (controller) tools to manage and schedule traffic in future terminal airspace. No studies have investigated the impacts that such tools (and concepts) could have on the flight-deck. To begin to redress the balance, an exploratory study investigated the procedures and actions of ten Boeing-747-400 crews as they flew eight continuous descent approaches in the Los Angeles terminal airspace, with the descents being controlled using speed alone. Although the study was exploratory in nature, four variables were manipulated: speed changes, route constraints, clearance phraseology, and winds. Despite flying the same scenarios with the same events and timing, there was at least a 50 second difference in the time it took crews to fly the approaches. This variation is the product of a number of factors but highlights potential difficulties for scheduling tools that would have to accommodate this amount of natural variation in descent times. The primary focus of this paper is the potential impact of ground scheduling tools on the flight crews performance and procedures. Crews reported "moderate to low" workload, on average; however, short periods of intense and high workload were observed. The non-flying pilot often reported a higher level of workload than the flying-pilot, which may be due to their increased interaction with the Flight Management Computer, when using the aircraft automation to assist with managing the descent clearances. It is concluded that ground-side tools and automation may have a larger impact on the current-day flight-deck than was assumed and that studies investigating this impact should continue in parallel with controller support tool development.

Martin, Lynne Hazel↗
NASA NTRSDate not supplied

An Agile-Like Approach to Hardware Development: The Ejectable Data Recorder (EDR) for Orion's Ascent Abort 2 (AA-2) Test Flight

On July 2, 2019, the Ascent Abort 2 (AA-2) Flight Test Vehicle was launched from Cape Canaveral, with the goal of demonstrating the performance of Orion’s Launch Abort System (LAS) and collecting data from hundreds of sensors throughout the vehicle. The data collected during this test flight is of paramount importance, as it will be used to certify the Orion vehicle for human spaceflight. Originally, the data was to be downlinked via a single string network of antennas on the LAS, with the associated risk of potential data dropouts, as well as loss of data once the LAS was jettisoned. Thus, additional antennas were added onto the crew module (CM) to support data downlink post-LAS jettison, a buffer rebroadcast capability was added to fill in any gaps in data downlink transmissions, and an ejectable data recorder (EDR) subsystem was added to the CM as a redundant measure to collect all the instrumentation data. The EDR subsystem was added to the project about one year after the project commenced, which significantly reduced the available development time when compared with the other subsystems of the AA-2 Test Flight. The project was further accelerated by six months, around the critical design review gate. Due to the schedule compression challenge and the fact that the EDR subsystem was a backup system and not flight critical, the EDR subsystem was further challenged to find a new and more efficient way to develop hardware. Thus, the EDR subsystem experimented with different management and systems engineering processes, team sizes, communication methods, and tools. Some examples are novel uses of SharePoint as a Data-centric Project Management & Systems Engineering environment, a continuous testing approach through the lifecycle, and a Skunkworks approach to managing the team. The EDR subsystem blended Commercial Off The Shelf (COTS) hardware with in-house developed hardware and software to create a novel data retrieval capability. The capability evolved rapidly through a hardware in the loop simulation environment that enabled incremental component updates for not only the EDR subsystem but across the entire Crew Module. This paper will present an overview of how the EDR subsystem was managed and compare it to an Agile approach to managing projects. The paper will further provide a recommended approach to future Agile-like hardware development that incorporates lessons learned from the EDR experience.

Agile↗
NASA NTRS1977

Automatic flight performance of a transport airplane on complex microwave landing system paths

Essential characteristics of the U.S. microwave landing system (MLS) and the TCV B-737 aircraft used in flight demonstrations are described, with special emphasis on the analysis of the approach paths. MLS is used to provide the aircraft with guidance for automatic control on complex, curved descending paths with precision turns into short final approaches terminating in landing and rollout, even when subjected to strong and gusty tail- and cross-wind components and severe wind shear. The tracking performance achieved on these paths under MLS guidance is examined in detail, and the wind environment where the flights are conducted are quantified. The flights demonstrate the utility of the wide-area coverage of MLS for curved, descending paths commencing with a standard RNAV approach into a terminal area and continuation of this approach throughout the MLS coverage and onto the runway.

Walsh, T. M.↗
NASA NTRS1991

Error latency measurements in symbolic architectures

Error latency, the time that elapses between the occurrence of an error and its detection, has a significant effect on reliability. In computer systems, failure rates can be elevated during a burst of system activity due to increased detection of latent errors. A hybrid monitoring environment is developed to measure the error latency distribution of errors occurring in main memory. The objective of this study is to develop a methodology for gauging the dependability of individual data categories within a real-time application. The hybrid monitoring technique is novel in that it selects and categorizes a specific subset of the available blocks of memory to monitor. The precise times of reads and writes are collected, so no actual faults need be injected. Unlike previous monitoring studies that rely on a periodic sampling approach or on statistical approximation, this new approach permits continuous monitoring of referencing activity and precise measurement of error latency.

Young, L. T.↗
NASA NTRS1991

An experimental cockpit display for TDWR wind shear alerts

The first successful ground-to-air data link and cockpit display of terminal Doppler weather radar (TDWR) wind shear warnings in real-time are reported. During the summer of 1990, wind shear warnings generated by the TDWR testbed radar at Orlando, Florida, were transmitted in real-time to a research aircraft performing microburst penetrations. Automatic delivery of TDWR wind shear warnings potentially result in decreased controller workload and improved pilot information. Pilot responses indicate that the information provided by the cockpit displays was useful in visualizing the location of wind shear hazards. The graphical display of microburst hazards provided better information than that currently provided by ATC verbal messages and pilot reports. This information was useful in assessing the microburst hazard, deciding whether to continue the approach, and planning escape maneuvers.

Campbell, Steven D.↗
NASA NTRS1994

Solar wind mass and momentum flux variations at 0.3 AU

In the past we have used electron Thomson scattering brightness observations, obtained with the zodiacal-light photometers on board the spacecraft Helios 1 and Helios 2, to study the global density structure of the quiet corona and inner heliosphere (greater than 17 solar radii). This was done by means of a comparison of synoptic maps based on these Thomson scattering observations and synoptic maps based on other solar/heliospheric data, such as IPS velocity, K-coronameter brightness and magnetic source surface data. In this paper we continue this approach by combining the Helios Thomson scattering maps (which provide density information) with IPS solar wind velocity maps to map out variations in mass and momentum flux of the solar wind as a function of latitude and phase of the solar cycle. The method used to construct the Helios and IPS synoptic maps emphasizes the global, persistent (as opposed to transient) structures, and thus can be viewed as approximating conditions in the quiet corona and inner heliosphere.

Hick, P.↗
NASA NTRS1995

Space-flight experience and life test performance of a synthetic hydrocarbon lubricant

An alternative wet lubricant known as Pennzane(TM) SHF X-2000 is recommended for some spaceflight bearing systems. The performance characteristics between Pennzane(TM) SHF X-2000 and Bray 815Z were compared. The life tests showed excellent performances with continuous operation approaching three years in conservative operating environments. Space flight performance data are provided for several of the tested mechanisms which are operating in-orbit since February 1994.

Bialke, Bill↗