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  • Meteorology and Climatology  (48)
  • Aircraft Propulsion and Power  (34)
  • 1995-1999  (82)
  • 1
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    Status of and Outlook for Largescale Modeling of Atmosphere-Ice-Ocean Interactions in the Arctic (1998)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: Arctic air masses have direct impacts on the weather and climatic extremes of midlatitude areas such as central North America. Arctic physical processes pose special and very important problems for global atmospheric models used for climate simulation and numerical weather prediction. At present, the observational database is inadequate to support research aimed at overcoming these problems. Three interdependent Arctic field programs now being planned will help to remedy this situation: SHEBA, which will operate an ice camp in the Arctic for a year-, ARM, which will supply instruments for use at the SHEBA ice camp and which will also conduct longer-term measurements near Barrow, Alaska; and FIRE, which will conduct one or more aircraft campaigns, in conjunction with remote-sensing investigations focused on the SHEBA ice camp. This paper provides an introductory overview of the physics of the Arctic from the perspective of large-scale modelers, outlines some of the modeling problems that arise in attempting to simulate these processes, and explains how the data to be provided by the three field programs can be used to test and improve large-scale models.
    Keywords: Meteorology and Climatology
    Type: Bulletin of the American Meteorological Society (ISSN 0003-0007); Volume 79; No. 2; 197-219
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Workstation-Based Real-Time Mesoscale Modeling Designed for Weather Support to Operations at the Kennedy Space Center and Cape Canaveral Air Station (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper describes the capabilities and operational utility of a version of the Mesoscale Atmospheric Simulation System (MASS) that has been developed to support operational weather forecasting at the Kennedy Space Center (KSC) and Cape Canaveral Air Station (CCAS). The implementation of local, mesoscale modeling systems at KSC/CCAS is designed to provide detailed short-range (less than 24 h) forecasts of winds, clouds, and hazardous weather such as thunderstorms. Short-range forecasting is a challenge for daily operations, and manned and unmanned launches since KSC/CCAS is located in central Florida where the weather during the warm season is dominated by mesoscale circulations like the sea breeze. For this application, MASS has been modified to run on a Stardent 3000 workstation. Workstation-based, real-time numerical modeling requires a compromise between the requirement to run the system fast enough so that the output can be used before expiration balanced against the desire to improve the simulations by increasing resolution and using more detailed physical parameterizations. It is now feasible to run high-resolution mesoscale models such as MASS on local workstations to provide timely forecasts at a fraction of the cost required to run these models on mainframe supercomputers. MASS has been running in the Applied Meteorology Unit (AMU) at KSC/CCAS since January 1994 for the purpose of system evaluation. In March 1995, the AMU began sending real-time MASS output to the forecasters and meteorologists at CCAS, Spaceflight Meteorology Group (Johnson Space Center, Houston, Texas), and the National Weather Service (Melbourne, Florida). However, MASS is not yet an operational system. The final decision whether to transition MASS for operational use will depend on a combination of forecaster feedback, the AMU's final evaluation results, and the life-cycle costs of the operational system.
    Keywords: Meteorology and Climatology
    Type: NASA-CR-204818 , NAS 1.26:204818 , Bulletin of the American Meteorological Society (ISSN 0003-0007); 77; 4; 653-672
    Format: application/pdf
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  • 3
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    High Stability Engine Control (HISTEC): Flight Demonstration Results (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Future aircraft turbine engines, both commercial and military, must be able to accommodate expected increased levels of steady-state and dynamic engine-face distortion. The current approach of incorporating sufficient design stall margin to tolerate these increased levels of distortion would significantly reduce performance. The High Stability Engine Control (HISTEC) program has developed technologies for an advanced, integrated engine control system that uses measurement- based estimates of distortion to enhance engine stability. The resulting distortion tolerant control reduces the required design stall margin, with a corresponding increase in performance and/or decrease in fuel burn. The HISTEC concept was successfully flight demonstrated on the F-15 ACTIVE aircraft during the summer of 1997. The flight demonstration was planned and carried out in two parts, the first to show distortion estimation, and the second to show distortion accommodation. Post-flight analysis shows that the HISTEC technologies are able to successfully estimate and accommodate distortion, transiently setting the stall margin requirement on-line and in real-time. Flight demonstration of the HISTEC technologies has significantly reduced the risk of transitioning the technology to tactical and commercial engines.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-1998-208655 , NAS 1.15:208655 , SAE-985556 , E-11375 , 1998 World Aviation Congress and Exposition; Sep 28, 1998 - Sep 30, 1998; Anaheim, CA; United States
    Format: application/pdf
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  • 4
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    Development and Testing of a High Stability Engine Control (HISTEC) System (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Flight tests were recently completed to demonstrate an inlet-distortion-tolerant engine control system. These flight tests were part of NASA's High Stability Engine Control (HISTEC) program. The objective of the HISTEC program was to design, develop, and flight demonstrate an advanced integrated engine control system that uses measurement-based, real-time estimates of inlet airflow distortion to enhance engine stability. With improved stability and tolerance of inlet airflow distortion, future engine designs may benefit from a reduction in design stall-margin requirements and enhanced reliability, with a corresponding increase in performance and decrease in fuel consumption. This paper describes the HISTEC methodology, presents an aircraft test bed description (including HISTEC-specific modifications) and verification and validation ground tests. Additionally, flight test safety considerations, test plan and technique design and approach, and flight operations are addressed. Some illustrative results are presented to demonstrate the type of analysis and results produced from the flight test program.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-1998-206562 , H-2269 , NAS 1.15:206562 , AIAA Paper 98-3715 , Propulsion; Jul 13, 1998 - Jul 15, 1998; Cleveland, OH; United States
    Format: application/pdf
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  • 5
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    High Stability Engine Control (HISTEC) Flight Test Results (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The High Stability Engine Control (HISTEC) Program, managed and funded by the NASA Lewis Research Center, is a cooperative effort between NASA and Pratt & Whitney (P&W). The program objective is to develop and flight demonstrate an advanced high stability integrated engine control system that uses real-time, measurement-based estimation of inlet pressure distortion to enhance engine stability. Flight testing was performed using the NASA Advanced Controls Technologies for Integrated Vehicles (ACTIVE) F-15 aircraft at the NASA Dryden Flight Research Center. The flight test configuration, details of the research objectives, and the flight test matrix to achieve those objectives are presented. Flight test results are discussed that show the design approach can accurately estimate distortion and perform real-time control actions for engine accommodation.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-1998-208481 , E-11255 , NAS 1.15:208481 , AIAA Paper 98-3757 , Propulsion; Jul 12, 1998 - Jul 15, 1998; Cleveland, OH; United States
    Format: application/pdf
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  • 6
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    The High Stability Engine Control (HISTEC) Program: Flight Demonstration Phase (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Future aircraft turbine engines, both commercial and military, must be able to accommodate expected increased levels of steady-state and dynamic engine-face distortion. The current approach of incorporating sufficient design stall margin to tolerate these increased levels of distortion would significantly reduce performance. The objective of the High Stability Engine Control (HISTEC) program is to design, develop, and flight-demonstrate an advanced, integrated engine control system that uses measurement-based estimates of distortion to enhance engine stability. The resulting distortion tolerant control reduces the required design stall margin, with a corresponding increase in performance and decrease in fuel burn. The HISTEC concept has been developed and was successfully flight demonstrated on the F-15 ACTIVE aircraft during the summer of 1997. The flight demonstration was planned and carried out in two phases, the first to show distortion estimation, and the second to show distortion accommodation. Post-flight analysis shows that the HISTEC technologies are able to successfully estimate and accommodate distortion, transiently setting the stall margin requirement on-line and in real-time. This allows the design stall margin requirement to be reduced, which in turn can be traded for significantly increased performance and/or decreased weight. Flight demonstration of the HISTEC technologies has significantly reduced the risk of transitioning the technology to tactical and commercial engines.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-1998-208482 , E-11257 , NAS 1.15:208482 , AIAA Paper 98-3756 , Joint Propulsion Conference; Jul 12, 1998 - Jul 15, 1998; Cleveland, OH; United States
    Format: application/pdf
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  • 7
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    Innovative Sealing Technology for Next Generation Subsonic Engines (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The next generation of subsonic engines can be expected to continue the historical trend towards increased thrust to weight (T/W) and decreased specific fuel consumption (SFC). Development programs currently underway throughout the gas turbine industry such as DOD's Integrated High Performance Turbine Engine Technology (IHPTET), and more recently NASA's Advanced Subsonic Transport (AST) programs, have altered these trends in both pace and magnitude. Advanced seals and sealing technologies have become a prominent part of these efforts due to the large potential performance gains which can be realized. Allison has recently completed a study for NASA the goal of which was to quantize the potential performance benefits which might accrue through the use of advanced seals in future subsonic gas turbine engines. For the study, two engines where analyzed, a small turboshaft and a larger turbofan engine to help assess the effect of engine size on the results. Engines were analyzed stage by stage with the most sensitive areas highlighted. Leakage characteristics for advanced seals were then substituted into secondary airflow models, and the leakage reductions documented. These leakage reductions were then converted to changes in performance, i.e. increased range, decreased takeoff gross weight, etc. and presented. It was found that the development and use of a realtively few advanced seals, less than 5, could for example reduce SFC by 10% or more.
    Keywords: Aircraft Propulsion and Power
    Type: Seals Code Development Workshop; 327-336; NASA-CP-10181
    Format: text
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  • 8
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    Differential Absorption Measurements of Atmospheric Water Vapor with a Coherent Lidar at 2050.532 nm (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Wind and water vapor are two major factors driving the Earth's atmospheric circulation, and direct measurement of these factors is needed for better understanding of basic atmospheric science, weather forecasting, and climate studies. Coherent lidar has proved to be a valuable tool for Doppler profiling of wind fields, and differential absorption lidar (DIAL) has shown its effectiveness in profiling water vapor. These two lidar techniques are generally considered distinctly different, but this paper explores an experimental combination of the Doppler and DIAL techniques for measuring both wind and water vapor with an eye-safe wavelength based on a solid-state laser material. Researchers have analyzed and demonstrated coherent DIAL water vapor measurements at 10 micrometers wavelength based on CO2 lasers. The hope of the research presented here is that the 2 gm wavelength in a holmium or thulium-based laser may offer smaller packaging and more rugged operation that the CO2-based approach. Researchers have extensively modeled 2 um coherent lasers for water vapor profiling, but no published demonstration is known. Studies have also been made, and results published on the Doppler portion, of a Nd:YAG-based coherent DIAL operating at 1.12 micrometers. Eye-safety of the 1.12 micrometer wavelength may be a concern, whereas the longer 2 micrometer and 10 micrometer systems allow a high level of eyesafety.
    Keywords: Meteorology and Climatology
    Type: Tenth Biennial Coherent Laser Radar Technology and Applications Conference; 68-71; NASA/CP-1999-209758
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  • 9
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    The Lightning Imaging Sensor (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Lightning Imaging Sensor (LIS) is a NASA Earth Observing System (EOS) instrument on the Tropical Rainfall Measuring Mission (TRMM) platform designed to acquire and investigate the distribution and variability of total lightning (i.e., cloud-to-ground and intracloud) between q35' in latitude. Since lightning is one of the responses of the atmosphere to thermodynamic and dynamic forcing, the LIS data is being used to detect deep convection without land-ocean bias, estimate the precipitation mass in the mixed phased region of thunderclouds, and differentiate storms with strong updrafts from those with weak vertical motion.
    Keywords: Meteorology and Climatology
    Type: 11th International Conference on Atmospheric Electricity; 746-749; NASA/CP-1999-209261
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  • 10
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    Global Frequency and Distribution of Lightning as Observed by the Optical Transient Detector (OTD) (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Optical Transient Detector (OTD) is a space-based instrument specifically designed to detect and locate lightning discharges (intracloud and cloud-to-ground) as it orbits the Earth. A statistical examination of OTD lightning data reveals that nearly 1.2 billion flashes occurred over the entire earth during the one year period from September 1995 through August 1996. This translates to an average of 37 lightning flashes occurring around the globe every second, which is well below the traditional estimate of 100 flashes per second. An average of 75% of the global lightning activity during the year occurs between 30' S and 30' N. An analysis of the annual lightning distribution reveals that an average of 82% of the lightning flashes occur over the continents and 18% over the oceans, which translates to an average land-ocean flash density ratio of nearly 11.
    Keywords: Meteorology and Climatology
    Type: 11th International Conference on Atmospheric Electricity; 726-729; NASA/CP-1999-209261
    Format: text
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