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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Engine Gaseous, Aerosol Precursor and Particulated Flight Altitude Conditions

The overall objective of the NASA Atmospheric Effects of Aviation Project (AEAP) is to develop scientific bases for assessing atmospheric impacts of the exhaust emissions by both current and future fleets of subsonic and supersonic aircraft. Among the six primary elements of the AEAP is Emissions Characterization. The objective of the Emission Characterization effort is to determine the exhaust emission constituents and concentrations at the engine exit plane. The specific objective of this engine test is to obtain a database of gaseous and particulate emissions as a function of fuel sulfur and engine operating conditions. The database of the particulate emission properties is to be used as a comparative baseline with subsequent flight measurement. The engine used in this test was a Pratt & Whitney F1OO-200E turbofan engine. Aviation fuel (Jet A) with a range of fuel sulfur was used. Low and high sulfur values are limited by commercially available fuels and by fuel specification limits of O.3% by weight. Test matrix was set by parametrically varying the combustor inlet temperature (T(sub 3) between idle and maximum power setting at simulated SLS and up to five other altitudes for each fuel. Four diagnostic systems, extractive and non-intrusive, were assembled for the gaseous and particulate emissions characterization measurements study. NASA extractive system includes smoke meter and analyzers for measurement of CO, CO2, NO, NOx, O2, total unburnt hydrocarbons (THC), and SO2. Particulate emissions were characterized by University of Missouri-Rolla Mobile Aerosol Sampling System. A chemical ionization mass spectrometer from the Air Force Research Laboratory at Hanscom AFB was used to measure SO2 and HNO3. Aerodyne Research. Inc. used infrared tunable diode laser absorption to measure SO2, SO3, NO, H2O and CO2.

Wey, C. C.↗
NASA NTRS1992

Computational fluid dynamics analysis of Space Shuttle main engine multiple plume flows at high-altitude flight conditions

Computational fluid dynamics (CFD) analysis is providing verification of Space Shuttle flight performance details and is being applied to Space Shuttle Main Engine Multiple plume interaction flow field definition. Advancements in real-gas CFD methodology that are described have allowed definition of exhaust plume flow details at Mach 3.5 and 107,000 ft. The specific objective includes the estimate of flow properties at oblique shocks between plumes and plume recirculation into the Space Shuttle Orbiter base so that base heating and base pressure can be modeled accurately. The approach utilizes the Rockwell USA Real Gas 3-D Navier-Stokes (USARG3D) Code for the analysis. The code has multi-zonal capability to detail the geometry of the plumes based region and utilizes finite-rate chemistry to compute the plume expansion angle and relevant flow properties at altitude correctly. Through an improved definition of the base recirculation flow properties, heating, and aerodynamic design environments of the Space Shuttle Vehicle can be further updated.

Dougherty, N. S.↗
NASA NTRS1972

High altitude flight test of a disk gap band parachute deployed behind a bluff body at a Mach number of 2.69

A flight test was conducted with a 55-foot diameter disk-gap-band parachute located at a trailing distance of 4.4 forebody diameters behind a 15-foot diameter bluff-body planetary entry aeroshell and attached instrumented payload. At the time of parachute deployment the aeroshell-payload combination was oscillating through an angle-of-attack range of plus or minus 40 deg. Continued oscillatory motion of the aeroshell-payload combination and similar motion of the parachute caused rapid changes in parachute shape and loading which resulted in extensive cloth damage in the band and outer disk-edge areas of the parachute canopy. During steady-state descent the damage parachute provided an effective-drag coefficient of about 0.33 which was about 60 percent of that expected.

Eckstrom, C.↗
NASA NTRS1973

Spacecraft separation systems mechanisms: Characteristics/performance during high altitude flight test from NASA Wallops Station, Va.

The applications of various separation mechanisms to meet flight mission goals within the physical and environmental constraints of a single stage rocket test vehicle are considered. Each separation concept was selected from the numerous choices available on the basis of its unique requirement and the flight test vehicle incorporated several different concepts. Attention to specific requirements and thoroughness in design and testing were essential to success since there is no specific single answer to separation problems.

Pride, J. D.↗
NASA NTRS1973

Sonic boom analysis for high altitude flight at high Mach number

Numerical programs are presented which take into account the nonlinear effects of high Mach number, the entropy change across the shock, the entropy and enthalpy variations in the atmospheric layer and the gravitational effect. Extension of the programs for the axisymmetric problems to handle nonaxisymmetric terms is described. The asymmetry can be caused by the geometry of the body, the lift and also the fact that the variations in the atmospheric layer are two-dimensional. Numerical results demonstrating the influences of these effects and comparison with existing approximate theories are presented.

Ferri, A.↗
NASA NTRS1988

Computer vision techniques for rotorcraft low-altitude flight

A description is given of research that applies techniques from computer vision to automation of rotorcraft navigation. The effort emphasizes the development of a methodology for detecting the ranges to obstacles in the region of interest based on the maximum utilization of passive sensors. The range map derived from the obstacle detection approach can be used as obstacle data for the obstacle avoidance in an automataic guidance system and as advisory display to the pilot. The lack of suitable flight imagery data, however, presents a problem in the verification of concepts for obstacle detection. This problem is being addressed by the development of an adequate flight database and by preprocessing of currently available flight imagery. Some comments are made on future work and how research in this area relates to the guidance of other autonomous vehicles.

Sridhar, Banavar↗
NASA NTRS1988

Simulation and analysis of image-based navigation system for rotorcraft low-altitude flight

The automation of helicopter NOE flight entails the modification of nominal trajectories on the basis of the detection and location of obstacles by means of onboard sensors. This process is presently studied using a sequence of images from a passive sensor mounted at the helicopter's center of gravity and oriented with the viewing axis along the rotorcraft's longitudinal body-axis. Three different Kalman filters are used to estimate the location of an object on the ground during the course of various simulated helicopter maneuvers; two of the three filters are found to yield good object location estimates.

Sridhar, Banavar↗
NASA NTRS1992

Analysis of image-based navigation system for rotorcraft low-altitude flight

Some of the issues in the location of objects using a sequence of images from a passive sensor are examined. Image-object differential equations for a rotorcraft executing an arbitrary maneuver are developed. Assuming an onboard inertial navigation system for rotorcraft, state estimation, this study considers how object location is affected by the choice of Kalman filter estimation technique, the rotorcraft, and the object. Simulation results are presented.

Sridhar, Banavar↗
NASA NTRS1991

Vision based techniques for rotorcraft low altitude flight

An overview of research in obstacle detection at NASA Ames Research Center is presented. The research applies techniques from computer vision to automation of rotorcraft navigation. The development of a methodology for detecting the range to obstacles based on the maximum utilization of passive sensors is emphasized. The development of a flight and image data base for verification of vision-based algorithms, and a passive ranging methodology tailored to the needs of helicopter flight are discussed. Preliminary results indicate that it is possible to obtain adequate range estimates except at regions close to the FOE. Closer to the FOE, the error in range increases since the magnitude of the disparity gets smaller, resulting in a low SNR.

Sridhar, Banavar↗
NASA NTRS1998

Design and Performance Calculations of a Propeller for Very High Altitude Flight

Reported here is a design study of a propeller for a vehicle capable of subsonic flight in Earth's stratosphere. All propellers presented were required to absorb 63.4 kW (85 hp) at 25.9 km (85,000 ft) while aircraft cruise velocity was maintained at Mach 0.40. To produce the final design, classic momentum and blade-element theories were combined with two and three-dimensional results from the Advanced Ducted Propfan Analysis Code (ADPAC), a numerical Navier-Stokes analysis code. The Eppler 387 airfoil was used for each of the constant section propeller designs compared. Experimental data from the Langley Low-Turbulence Pressure Tunnel was used in the strip theory design and analysis programs written. The experimental data was also used to validate ADPAC at a Reynolds numbers of 60,000 and a Mach number of 0.20. Experimental and calculated surface pressure coefficients are compared for a range of angles of attack. Since low Reynolds number transonic experimental data was unavailable, ADPAC was used to generate two-dimensional section performance predictions for Reynolds numbers of 60,000 and 100,000 and Mach numbers ranging from 0.45 to 0.75. Surface pressure coefficients are presented for selected angles of attack. in addition to the variation of lift and drag coefficients at each flow condition. A three-dimensional model of the final design was made which ADPAC used to calculated propeller performance. ADPAC performance predictions were compared with strip-theory calculations at design point. Propeller efficiency predicted by ADPAC was within 1.5% of that calculated by strip theory methods, although ADPAC predictions of thrust, power, and torque coefficients were approximately 5% lower than the strip theory results. Simplifying assumptions made in the strip theory account for the differences seen.

Koch, L. Danielle↗
NASA NTRS1986

Liquid crystals for high-altitude in-flight boundary layer flow visualization

A novel method for visualization of laminar to turbulent boundary layer transition in flight is presented, in which liquid crystal coatings are used to indicate the transition by a change of color (in response to the changes in the wall shear and the temperature). The liquid crystals applied to the wing surfaces were either cholesteric crystals formulated to be active between temperatures of 30 and 100 F or a sample of chiral nematic liquid crystals formulated to be active between -18 and -22 F. Liquid crystal coatings were shown to provide visualization data at flight altitudes and temperatures at which data could not be obtained previously. Flight evaluations were successfully conducted on a T-34C and a Learjet research aircraft at Mach numbers of up to 0.8 and altitudes of up to 50,000 ft. The time response during oscillating sideslip tests was very rapid. In wind tunnel tests, a hysteresislike behavior was observed in the liquid crystal coatings, possibly because of the lower dynamic pressures in wind tunnels as compared to flight.

Gall, P. D.↗
NASA NTRS2018

Calculation Method for Predicting AM0 Isc from High Altitude Aircraft Flight Data

High altitude aircraft have been used by by the space photovoltaic (PV) community to determine the Air Mass Zero (AM0) performance of solar cells for over fifty years. Relative to in-space measurement opportunities, these methods are generally cheaper and more readily available. The data obtained, however, must be corrected for residual atmospheric effects. This paper details the correction method currently being used for the calculation of the AM0 short-circuit current (Isc) for photovoltaic devices flown on the NASA ER-2 (Earth Resources-2) calibration platform. This method would also be applicable to any other high altitude method where Isc data is collected over a sufficiently large range of altitudes.

Myers, Matthew G.↗
NASA NTRS2018

Calculation Method for Predicting AM0 Isc from High Altitude Aircraft Flight Data

High altitude aircraft have been used by the space photovoltaic (PV) community to determine the air mass Zero (AM0) performance of solar cells for over fifty years. Relative to in-space measurement opportunities, these methods are generally cheaper and more readily available. The data obtained, however, must be corrected for residual atmospheric effects. This paper details the correction method currently being used for the calculation of the estimated AM0 short-circuit current (Isc) for photovoltaic devices flown on the NASA ER-2 calibration platform. This method would also be applicable to other high altitude methods where Isc data is collected over a sufficiently large range of altitudes. An initial comparison with a four junction (4J) cell flown on the CASOLBA high altitude balloon platform showed an agreement to 0.2%.

AM0↗
NASA NTRS1993

Flight evaluation of a computer aided low-altitude helicopter flight guidance system

The Flight Systems Development branch of the U.S. Army's Avionics Research and Development Activity (AVRADA) and NASA Ames Research Center have developed for flight testing a Computer Aided Low-Altitude Helicopter Flight (CALAHF) guidance system. The system includes a trajectory-generation algorithm which uses dynamic programming and a helmet-mounted display (HMD) presentation of a pathway-in-the-sky, a phantom aircraft, and flight-path vector/predictor guidance symbology. The trajectory-generation algorithm uses knowledge of the global mission requirements, a digital terrain map, aircraft performance capabilities, and precision navigation information to determine a trajectory between mission way points that seeks valleys to minimize threat exposure. This system was developed and evaluated through extensive use of piloted simulation and has demonstrated a 'pilot centered' concept of automated and integrated navigation and terrain mission planning flight guidance. This system has shown a significant improvement in pilot situational awareness, and mission effectiveness as well as a decrease in training and proficiency time required for a near terrain, nighttime, adverse weather system. AVRADA's NUH-60A STAR (Systems Testbed for Avionics Research) helicopter was specially modified, in house, for the flight evaluation of the CALAHF system. The near terrain trajectory generation algorithm runs on a multiprocessor flight computer. Global Positioning System (GPS) data are integrated with Inertial Navigation Unit (INU) data in the flight computer to provide a precise navigation solution. The near-terrain trajectory and the aircraft state information are passed to a Silicon Graphics computer to provide the graphical 'pilot centered' guidance, presented on a Honeywell Integrated Helmet And Display Sighting System (IHADSS). The system design, piloted simulation, and initial flight test results are presented.

Swenson, Harry N.↗
NASA NTRS1993

Flight evaluation of a computer aided low-altitude helicopter flight guidance system

The Flight Systems Development branch of the U.S. Army's Avionics Research and Development Activity (AVRADA) and NASA Ames Research Center developed for flight testing a Computer Aided Low-Altitude Helicopter Flight (CALAHF) guidance system. The system includes a trajectory-generation algorithm which uses dynamic programming and a helmet-mounted display (HMD) presentation of a pathway-in-the-sky, a phantom aircraft, and flight-path vector/predictor guidance symbology. The trajectory-generation algorithm uses knowledge of the global mission requirements, a digital terrain map, aircraft performance capabilities, and precision navigation information to determine a trajectory between mission waypoints that seeks valleys to minimize threat exposure. This system was developed and evaluated through extensive use of piloted simulation and has demonstrated a 'pilot centered' concept of automated and integrated navigation and terrain mission planning flight guidance. This system has shown a significant improvement in pilot situational awareness, and mission effectiveness as well as a decrease in training and proficiency time required for a near terrain, nighttime, adverse weather system.

Swenson, Harry N.↗