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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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At least 271 records · Page 15
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NASA NTRS2024

A Decade of Salt Marsh Elevation Change in New York City’s Coastal Urban Parks

Coastal salt marshes of the eastern United States are particularly vulnerable to accelerated sea level rise, and urban marshes are at greater risk of erosion, inundation, and conversion to mudflat if left unmanaged. To guide New York City (NYC) salt marsh restoration strategies, NYC Parks collected up to 10 years of salt marsh elevation change data through 2020 at six salt marsh sites using the Surface Elevation Table-Marker Horizon (SET-MH) method, conducted a salt marsh trends analysis to determine shoreline change from 1974 to 2012, and conducted a salt marsh conditions assessment. We found that the citywide average surface elevation trend of 3.31 mm yr −1 was not significantly different from the 30-year (1990–2020) Relative Sea Level Rise of 4.23 mm yr −1 at The Battery, NY, tide station, probably due to high variability across and within sites. We also found that accretion rates differed across sites and watersheds, and sites situated lower in the tidal zone had higher accretion rates. Notably, Jamaica Bay’s Idlewild salt marsh, long suspected of being sediment-starved and ranking lowest in our conditions assessment, had the highest accretion rate at 9.5 mm yr −1 . Our salt marsh trends analysis also showed marsh loss at the shoreline edge, bare ground cover, and other indicators of marsh degradation. In mitigating marsh loss, the design grades for our recent wetland restoration projects enlarge the upper elevation ranges of the low- and high-marsh zones and incorporate wider and more gradual slopes in upland transition zones to enable inland marsh migration.

Salt marsh elevation change↗
NASA NTRS2022

Mini-disk accretion onto spinning black hole binaries: quasi-periodicities and outflows

We perform a full 3D general relativistic magnetohydrodynamical (GRMHD) simulation of an equal-mass, spinning, binary black hole approaching merger, surrounded by a circumbinary disk and with mini-disks around each black hole. For this purpose, we evolve the ideal GRMHD equations on top of an approximated spacetime for the binary that is valid in every position of space, including the black hole horizons, during the inspiral regime. We use relaxed initial data for the circumbinary disk from a previous long-term simulation, where the accretion is dominated by an m = 1 overdensity called the lump. We compare our new spinning simulation with a previous non-spinning run, studying how spin influences the mini-disk properties. We analyze the accretion from the inner edge of the lump to the black hole, focusing on the angular momentum budget of the fluid around the mini-disks. We find that mini-disks in the spinning case have more mass over a cycle than the non-spinning case. However, in both cases we find most of the mass received by the black holes is delivered by direct plunging of material from the lump. We also analyze the morphology and variability of the electromagnetic fluxes and we find they share the same periodicities of the accretion rate. In the spinning case, we find that the outflows are stronger than the non-spinning case. Our results will be useful to understand and produce realistic synthetic light curves and spectra, which can be used in future observations.

Astrophysics↗
NASA NTRS1976

A 0.4 to 10 GHz airborne electromagnetic environment survey of USA urban areas

An airborne electromagnetic-environment survey of some U.S. metropolitan areas measured terrestrial emissions within the broad frequency spectrum from 0.4 to 10 GHz. A Cessna 402 commercial aircraft was fitted with both nadir-viewing and horizon-viewing antennas and instrumentation, including a spectrum analyzer, a 35 mm continuous film camera, and a magnetic tape recorder. Most of the flights were made at a nominal altitude of 10,000 feet, and Washington, D. C., Baltimore, Philadelphia, New York, and Chicago were surveyed. The 450 to 470 MHz land-mobile UHF band is especially crowded, and the 400 to 406 MHz space bands are less active. This paper discusses test measurements obtained up to 10 GHz. Sample spectrum analyzer photograhs were selected from a total of 5,750 frames representing 38 hours of data.

Taylor, R. E.↗
NASA NTRS1976

0.4- to 10-GHz airborne electromagnetic-environment survey of United States urban areas

An airborne electromagnetic-environment survey of some U.S. metropolitan areas measured terrestrial emissions within the broad-frequency spectrum from 0.4 to 10 GHz. A Cessna 402 commercial aircraft was fitted with both nadir-viewing and horizon-viewing antennas and instrumentation, including a spectrum analyzer, a 35-mm continuous-film camera, and a magnetic-tape recorder. Most of the flights were made at a nominal altitude of 10,000 ft, and Washington, Baltimore, Philadelphia, New York, and Chicago were surveyed. The 450- to 470-MHz land-mobile UHF band is especially crowded, and the 400- to 406-MHz space bands are less active. Test measurements obtained up to 10 GHz are discussed. Sample spectrum-analyzer photographs were selected from a total of 5750 frames representing 38 hours of data.

Taylor, R. E.↗
NASA NTRS2002

High Resolution X-ray Imaging

NAG5-5020 covered a period of 7.5 years during which a great deal of progress was made in x-ray optical techniques under this grant. We survived peer review numerous times during the effort to keep the grant going. In 1994, when the grant started we were actively pursuing the application of spherical mirrors to improving x-ray telescopes. We had found that x-ray detectors were becoming rapidly more sophisticated and affordable, but that x-ray telescopes were only being improved through the intense application of money within the AXAF program. Clearly new techniques for the future were needed. We were successful in developing and testing at the HELSTF facility in New Mexico a four reflection coma-corrected telescope made from spheres. We were able to demonstrate 0.3 arcsecond resolution, almost to the diffraction limit of the system. The community as a whole was, at that time, not particularly interested in looking past AXAF (Chandra) and the effort needed to evolve. Since we had reached the diffraction limit using non-Wolter optics we then decided to see if we could build an x-ray interferometer in the laboratory. In the lab the potential for improved resolution was substantial. If synthetic aperture telescopes could be built in space, then orders of magnitude improvement would become feasible. In 1998 NASA, under the direction of Dr Nick White of Goddard, started a study to assess the potential and feasibility of x-ray interferometry in space. My work became of central interest to the committee because it indicated that such was possible. In early 1999 we had the breakthrough that allowed us build a practical interferometer. By using flats and hooking up with the Marshall Space Flight Center facilities we were able to demonstrate fringes at 1.25keV on a one millimeter baseline. This actual laboratory demonstration provided the solid proof of concept that NASA needed. As the year progressed the future of x-ray astronomy jelled around the Maxim program. Maxim is a set of two major x-ray astronomy missions based on the concepts I developed and demonstrated under this SR&T grant. The first Maxim is to image the sky at 100 micro-arcsecond resolution. That is one thousand times higher resolution than Hubble. The full Maxim has the ultimate goal of imaging the event horizon of a black hole in an active galactic nucleus (ALAN). This will require 0.1 micro-arcsecond resolution - one million times higher than Hubble! Nonetheless, using the techniques developed under this grant, it has become possible. Maxim Pathfinder is now in the NASA planning for a new start in approximately 20 10. The full Maxim is carried as a vision mission for the post 2015 timeframe. Finally, this grant is the evolved version of the SR&T grant we carried during the 1980s and up to 1994. At that point in time this grant was also working on x-ray optics, but concentrating on x-ray spectroscopy. The techniques developed by 1990 were not chosen for use on Chandra or XMM-Newton because they were too new. During the last year, however, the Constellation-X mission recognized the need for better spectroscopy techniques and tapped our expertise. We were able to support the initial work on Con-X through this program. It now appears that the off-plane mount will be used in Con-X, increasing performance and decreasing cost and risk.

Cash, Webster↗
NASA NTRS1984

New antenna feed revitalizes Space Shuttle tracker at NASA Edwards

An account is given of the upgrading of a 12-ft-diameter single-channel monopulse tracking system, which had been relegated to slaved backup status at NASA Edwards, to support research flights for Ames Dryden Research Center and for tracking orbital passes of the Space Shuttle and Shuttle landings both at Edwards and at White Sands. The improved system is now a stand-alone telemetry tracking system. A new conical scanning feed (known as Radscan) replaces the single channel monopulse feed in the upgraded system. Where previously the system would not autotrack at elevation angles below 5 degrees, it now automatically acquires the Space Shuttle when it appears on the horizon and autotracks from approximately 2 degrees in elevation to touchdown, and does so virtually unattended.

Wrin, J. W.↗
NASA NTRSDate not supplied

Where IMERG Goes Next: Version 08 and Beyond

With the Version 07 (V07) Integrated Multi-satellitE Retrievals for GPM (IMERG) algorithm finalized and production initiated, the focus turns to enhancements for Version 08. These include innovations not included in V07 due to time constraints, plus issues revealed by the initial V07 products. One high priority is to evaluate and revise the schemes in V07 that rectify temporal artifacts caused by the time interpolation that fills the gaps between the various passive microwave (PMW) sensor overpasses. A second priority is to improve the homogeneity between the TRMM and GPM eras by characterizing differences between the two eras, determining the causes of these differences, and applying corrections as feasible, perhaps by enforcing spatial scale consistency (an overarching issue). Certainly, we must account for GPROF and the Combined Radar-Radiometer Algorithm converting to Machine Learning schemes in V08. Other priority topics include additional automated quality control for artifacts in the IR brightness temperatures and PMW precipitation fields, revisions to the specification algorithm for the probability of liquid precipitation, and accommodating new PMW sensors, which include the next generation of small-sats. We also consider the post-V08 landscape; the final GPM reprocessing will be restricted to fixing known code or algorithmic errors. Nonetheless, there are several data sources on the horizon to consider, including more small-sat PMW radiometers, AVHRR-based precipitation estimates (most useful in high latitudes), and the ISCCP-Next Generation and GEO-Ring projects that could provide easy access to multiple geosynchronous satellite channels and enable significantly improved algorithms compared to GEO-IR alone.

George J. Huffman↗
NASA NTRS2010

Reactive Collision Avoidance Algorithm

The reactive collision avoidance (RCA) algorithm allows a spacecraft to find a fuel-optimal trajectory for avoiding an arbitrary number of colliding spacecraft in real time while accounting for acceleration limits. In addition to spacecraft, the technology can be used for vehicles that can accelerate in any direction, such as helicopters and submersibles. In contrast to existing, passive algorithms that simultaneously design trajectories for a cluster of vehicles working to achieve a common goal, RCA is implemented onboard spacecraft only when an imminent collision is detected, and then plans a collision avoidance maneuver for only that host vehicle, thus preventing a collision in an off-nominal situation for which passive algorithms cannot. An example scenario for such a situation might be when a spacecraft in the cluster is approaching another one, but enters safe mode and begins to drift. Functionally, the RCA detects colliding spacecraft, plans an evasion trajectory by solving the Evasion Trajectory Problem (ETP), and then recovers after the collision is avoided. A direct optimization approach was used to develop the algorithm so it can run in real time. In this innovation, a parameterized class of avoidance trajectories is specified, and then the optimal trajectory is found by searching over the parameters. The class of trajectories is selected as bang-off-bang as motivated by optimal control theory. That is, an avoiding spacecraft first applies full acceleration in a constant direction, then coasts, and finally applies full acceleration to stop. The parameter optimization problem can be solved offline and stored as a look-up table of values. Using a look-up table allows the algorithm to run in real time. Given a colliding spacecraft, the properties of the collision geometry serve as indices of the look-up table that gives the optimal trajectory. For multiple colliding spacecraft, the set of trajectories that avoid all spacecraft is rapidly searched on-line. The optimal avoidance trajectory is implemented as a receding-horizon model predictive control law. Therefore, at each time step, the optimal avoidance trajectory is found and the first time step of its acceleration is applied. At the next time step of the control computer, the problem is re-solved and the new first time step is again applied. This continual updating allows the RCA algorithm to adapt to a colliding spacecraft that is making erratic course changes.

Scharf, Daniel↗
NASA NTRS1998

A Domain-Decomposed Multi-Level Method for Adaptively Refined Cartesian Grids with Embedded Boundaries

The work presents a new method for on-the-fly domain decomposition technique for mapping grids and solution algorithms to parallel machines, and is applicable to both shared-memory and message-passing architectures. It will be demonstrated on the Cray T3E, HP Exemplar, and SGI Origin 2000. Computing time has been secured on all these platforms. The decomposition technique is an outgrowth of techniques used in computational physics for simulations of N-body problems and the event horizons of black holes, and has not been previously used by the CFD community. Since the technique offers on-the-fly partitioning, it offers a substantial increase in flexibility for computing in heterogeneous environments, where the number of available processors may not be known at the time of job submission. In addition, since it is dynamic it permits the job to be repartitioned without global communication in cases where additional processors become available after the simulation has begun, or in cases where dynamic mesh adaptation changes the mesh size during the course of a simulation. The platform for this partitioning strategy is a completely new Cartesian Euler solver tarcreted at parallel machines which may be used in conjunction with Ames' "Cart3D" arbitrary geometry simulation package.

Aftosmis, M. J.↗
NASA NTRS1992

TechSAT attitude control

TechSAT is an academic program of the Technion - Israel Institute of Technology. Emphasizing new engineering solutions, it will be a low-cost, sun-synchronized, 3-axis stabilized, nadir-pointing 50-kg microsat, and will be launched by Arianne as a piggyback payload. The satellite is actually a gyrostat, based on a momentum wheel, a static horizon sensor, three magnetotorquers and a 3-axis magnetometer, all especially designed for TechSAT, with total power consumption of under 3 W. The satellite is designed to be released with unknown attitude and with zero stored momentum. The wheel is accelerated to its biased momentum and the body is slowly controlled to become stabilized, using algorithms that utilize magnetometer data only, to an accuracy of 5 deg, which is considered as coarse cruise. Next, fine cruise uses the static horizon sensor, and a final accuracy of 0.1 deg is achieved.

Shachar, M.↗
NASA NTRS1997

Summer High School Apprenticeship Research Program (SHARP)

The summer of 1997 will not only be noted by NASA for the mission to Mars by the Pathfinder but also for the 179 brilliant apprentices that participated in the SHARP Program. Apprentice participation increased 17% over last year's total of 153 participants. As indicated by the End-of-the-Program Evaluations, 96% of the programs' participants rated the summer experience from very good to excellent. The SHARP Management Team began the year by meeting in Cocoa Beach, Florida for the annual SHARP Planning Conference. Participants strengthened their Education Division Computer Aided Tracking System (EDCATS) skills, toured the world-renowned Kennedy Space Center, and took a journey into space during the Alien Encounter Exercise. The participants returned to their Centers with the same goals and objectives in mind. The 1997 SHARP Program goals were: (1) Utilize NASA's mission, unique facilities and specialized workforce to provide exposure, education, and enrichment experiences to expand participants' career horizons and inspire excellence in formal education and lifelong learning. (2) Develop and implement innovative education reform initiatives which support NASA's Education Strategic Plan and national education goals. (3) Utilize established statistical indicators to measure the effectiveness of SHARP's program goals. (4) Explore new recruiting methods which target the student population for which SHARP was specifically designed. (5) Increase the number of participants in the program. All of the SHARP Coordinators reported that the goals and objectives for the overall program as well as their individual program goals were achieved. Some of the goals and objectives for the Centers were: (1) To increase the students' awareness of science, mathematics, engineering, and computer technology; (2) To provide students with the opportunity to broaden their career objectives; and (3) To expose students to a variety of enrichment activities. Most of the Center goals and objectives were consistent with the overall program goals. Modem Technology Systems, Inc., was able to meet the SHARP Apprentices, Coordinators and Mentors during their site visits to Stennis Space Center, Ames Research Center and Dryden Flight Research Center. All three Centers had very efficient programs and adhered to SHARP's general guidelines and procedures. MTSI was able to meet the apprentices from the other Centers via satellite in July during the SHARP Video-Teleconference(ViTS). The ViTS offered the apprentices and the NASA and SHARP Coordinators the opportunity to introduce themselves. The apprentices from each Center presented topical "Cutting Edge Projects". Some of the accomplishments for the 1997 SHARP Program year included: MTSI hiring apprentices from four of the nine NASA Centers, the full utilization of the EDCATS by apprentices and NASA/SHARP Coordinators, the distribution of the SHARP Apprentice College and Scholarship Directory, a reunion with former apprentices from Langley Research Center and the development of a SHARP Recruitment Poster. MTSI developed another exciting newsletter containing graphics and articles submitted by the apprentices and the SHARP Management Team.

Source record↗
NASA NTRS1976

Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 2: Final report

The results are presented of a study which identifies over 100 new and highly capable space systems for the 1980-2000 time period: civilian systems which could bring benefits to large numbers of average citizens in everyday life, much enhance the kinds and levels of public services, increase the economic motivation for industrial investment in space, expand scientific horizons; and, in the military area, systems which could materially alter current concepts of tactical and strategic engagements. The requirements for space transportation, orbital support, and technology for these systems are derived, and those requirements likely to be shared between NASA and the DoD in the time period identified. The high leverage technologies for the time period are identified as very large microwave antennas and optics, high energy power subsystems, high precision and high power lasers, microelectronic circuit complexes and data processors, mosaic solid state sensing devices, and long-life cryogenic refrigerators.

Bekey, I.↗
NASA NTRSDate not supplied

Performance and Accuracy Assessment of Line Marching Algorithm Computations Utilizing GPUs Within a Predictive GNSS Quality Service

This paper presents a detailed analysis of the accuracy and performance of line marching algorithms executing on a GPU. In the context of an accurate Global Navigation Satellite System(GNSS) quality of service simulation, horizon sky-plots are a useful tool to determine satellite visibility in the presence of obstructions from objects, such as buildings or dense foliage. In order to accurately model satellite visibility at a point of interest on a map, a horizon plot can identify the viewing angles at which objects are blocking the sky. This computation requires traversing a line starting at the point of interest on a 2D altitude map, moving outward for every azimuth angle. To explore the performance of this computation, we propose a new dynamic stopping condition for the traversal of the line, benefiting from objects close to the point of interest. We compare the accuracy of common line marching algorithms, and consider their parallel performance when developed in CUDA. We find that our proposed stopping condition for line marching provides a significant improvement in performance in urban canyon sky-plots, as compared to previous work. Additionally, these results show that simpler algorithms, such as the digital differential analyzer line algorithm, are better suited for GPUs than more sophisticated schemes such as Bresenham’s algorithm, specifically in the context of sky-plothorizon computations. The trade-off between accuracy and performance is analyzed and providing guidance that depends on the targeted goal of the GNSS application.

GNSS↗
NASA NTRS1975

A seismic refraction technique used for subsurface investigations at Meteor Crater, Arizona

A seismic refraction technique for interpreting the subsurface shape and velocity distribution of an anomalous surface feature such as an impact crater is described. The method requires the existence of a relatively deep refracting horizon and combines data obtained from both standard shallow refraction spreads and distant offset shots by using the deep refractor as a source of initial arrivals. Results obtained from applying the technique to Meteor crater generally agree with the known structure of the crater deduced by other investigators and provide new data on an extensive fractured zone surrounding the crater. The breccia lens is computed to extend roughly 190 m below the crater floor, about 30 m less than the value deduced from early drilling data. Rocks around the crater are fractured as distant as 900 m from the rim crest and to a depth of at least 800 m beneath the crater floor.

Ackermann, H. D.↗
NASA NTRS1979

A study of the cost-effective markets for new technology agricultural aircraft

A previously developed data base was used to estimate the regional and total U.S. cost-effective markets for a new technology agricultural aircraft as incorporating features which could result from NASA-sponsored aerial applications research. The results show that the long-term market penetration of a new technology aircraft would be near 3,000 aircraft. This market penetration would be attained in approximately 20 years. Annual sales would be about 200 aircraft after 5 to 6 years of introduction. The net present value of cost savings benefit which this aircraft would yield (measured on an infinite horizon basis) would be about $35 million counted at a 10 percent discount rate and $120 million at a 5 percent discount rate. At both discount rates the present value of cost savings exceeds the present value of research and development (R&D) costs estimated for the development of the technology base needed for the proposed aircraft. These results are quite conservative as they have been derived neglecting future growth in the agricultural aviation industry, which has been averaging about 12 percent per year over the past several years.

Hazelrigg, G. A., Jr.↗
NASA NTRS2016

Telemetry Options for LDB Payloads

The Columbia Scientific Balloon Facility provides Telemetry and Command systems necessary for balloon operations and science support. There are various Line-Of-Sight (LOS) and Over-The-Horizon (OTH) systems and interfaces that provide communications to and from a science payload. This presentation will discuss the current data throughput options available and future capabilities that may be incorporated in the LDB Support Instrumentation Package (SIP) such as doubling the TDRSS data rate. We will also explore some new technologies that could potentially expand the data throughput of OTH communications.

Balloon↗
NASA NTRS2020

Improved LOLA Elevation Maps for South Pole Landing Sites: Error Estimates and Their Impact on Illumination Conditions

We present new high-resolution topographic models of 4 high-priority lunar south pole landing sites based exclusively on the laser altimetry data acquired by the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter. By iteratively adjusting the LOLA tracks to the LOLA-based digital elevation model (LDEM) in a self-consistent fashion, we reduce the orbital geolocation errors by over a factor of 10 such that the new ground track geolocation uncertainty is ~10–20 ​cm horizontally and ~2–4 ​cm vertically over each 16 ​× ​16 km region. These new and improved 5 ​m/pix LDEMs will be useful to constrain higher-resolution topographic models derived from imagery, which are not as well controlled geodetically and which can be hindered by shadows. We developed a method to estimate surface height uncertainty in the new LDEMs, which accounts for the reduced orbital errors and interpolation errors by assuming a fractal behavior for the short-scale topography. The LDEM surface height and slope uncertainties have typical RMS values of ~0.30–0.50 ​m and ~1.5–2.5°, respectively. Finally, we examine how height uncertainties propagate to variations in horizon elevation and thus the predicted illumination conditions at these polar latitudes, and we show how this error characterization can inform landing site studies.

Michael K Barker↗
NASA NTRS1986

Homogeneous cosmological models and new inflation

The promise of the inflationary-universe scenario is to free the present state of the universe from extreme dependence upon initial data. Paradoxically, inflation is usually analyzed in the context of the homogeneous and isotropic Robertson-Walker cosmological models. It is shown that all but a small subset of the homogeneous models undergo inflation. Any initial anisotropy is so strongly damped that if sufficient inflation occurs to solve the flatness and horizon problems, the universe today would still be very isotropic.

Turner, Michael S.↗