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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Automated aircraft scheduling methods in the near terminal area.

A general scheduling algorithm for aircraft from terminal area entry to touchdown is developed. The method has the following novel features: (1) many speed classes of aircraft are considered and speed variations within classes and along portions of the flight path are permitted; (2) multiple paths are considered which may merge or diverge - the analysis is not restricted to a single runway nor to departures only; (3) landings are scheduled along conflict free flight paths in minimum time. The algorithm is currently being incorporated in a fast-time simulation of a STOL air traffic system.

Tobias, L.↗
NASA NTRS1986

Optimal control laws for microburst encounter

Simplified structures for longitudinal control laws that reduce an aircraft's response to the strong head-tailwind and downdraft variations associated with microbursts are presented. They are based on non-zero-set-point linear-quadratic regulators that command throttle setting and angle of attack as functions of velocity and flight path angle, and they can incorporate direct measurements of the wind profile if available. Selection of cost functions to be minimized by feedback control has been aided by a prior study of classical control laws and exact nonlinear-optimal flight paths through realistic microburst wind profiles. The resulting optimal control laws have an adaptive, dual-mode structure that can be implemented either in flight-director logic or in an autopilot.

Stengel, R. F.↗
NASA NTRS1976

Determination of statistics for any rotation of axes of a bivariate normal elliptical distribution

Transformation of statistics from a dimensional set to another dimensional set involves linear functions of the original set of statistics. Similarly, linear functions will transform statistics within a dimensional set such that the new statistics are relevant to a new set of coordinate axes. A restricted case of the latter is the rotation of axes in a coordinate system involving any two correlated random variables. A special case is the transformation for horizontal wind distributions. Wind statistics are usually provided in terms of wind speed and direction (measured clockwise from north) or in east-west and north-south components. A direct application of this technique allows the determination of appropriate wind statistics parallel and normal to any preselected flight path of a space vehicle. Among the constraints for launching space vehicles are critical values selected from the distribution of the expected winds parallel to and normal to the flight path. These procedures are applied to space vehicle launches at Cape Kennedy, Florida.

Falls, L. W.↗
NASA NTRS1980

Instrumented aircraft verification of clear-air radar detection of low-level wind shear

A technique is described in which the longitudinal wind component at airports, measured by Doppler radar, is put through a Fourier transformation to produce an energy density spectrum. The result is multiplied by the aircraft response characteristics to produce quantitative data on aircraft performance in a wind shear situation. The Doppler radar measurements are made along the intended flight path. Two case studies, along a 3 deg approach path, are described from measurements in two modes: Lagrangian, where predictions were computed one range gate ahead of the plane, and Eulerian, where samples were measured instantaneously along the flight path. Wind data obtained every second were interpolated to fit a numerical model by using a cubic spline. Eulerian data were superior to Lagrangian data in terms of ranging, and nearly equal for wind speeds. Improvements in current 75% accuracy are noted to be possible with shrouded antennas to reduce sidelobes and use of Doppler radar with higher resolution to eliminate effects of small scale disturbances within the pulse volume.

Mccarthy, J.↗
NASA NTRS1983

Path discrepancies between great circle and rhumb line

A mathematical model for a comparative analysis of great circle vs. rhumb line navigation in the continental United States has been developed at the Avionics Engineering Center, Ohio University. A FORTRAN simulation of the model has been implemented on the IBM 370 computer. The simulation predicts pertinent navigation information for the two flight paths. The basis for the project, which is a part of an M.S. thesis, is to provide a data base for computing discrepancies between the two flight paths. This document briefly describes the model and discusses the implications of the results obtained.

Kaul, R.↗
NASA NTRS1984

Effects of aircraft and flight parameters on energy-efficient profile descents in time-based metered traffic

Attention is given to a computer algorithm yielding the data required for a flight crew to navigate from an entry fix, about 100 nm from an airport, to a metering fix, and arrive there at a predetermined time, altitude, and airspeed. The flight path is divided into several descent and deceleration segments. Results for the case of a B-737 airliner indicate that wind and nonstandard atmospheric properties have a significant effect on the flight path and must be taken into account. While a range of combinations of Mach number and calibrated airspeed is possible for the descent segments leading to the metering fix, only small changes in the fuel consumed were observed for this range of combinations. A combination that is based on scheduling flexibility therefore seems preferable.

Dejarnette, F. R.↗
NASA NTRS2017

'Fly Like This': Natural Language Interface for UAV Mission Planning

With the increasing presence of unmanned aerial vehicles (UAVs) in everyday environments, the user base of these powerful and potentially intelligent machines is expanding beyond exclusively highly trained vehicle operators to include non-expert system users. Scientists seeking to augment costly and often inflexible methods of data collection historically used are turning towards lower cost and reconfigurable UAVs. These new users require more intuitive and natural methods for UAV mission planning. This paper explores two natural language interfaces - gesture and speech - for UAV flight path generation through individual user studies. Subjects who participated in the user studies also used a mouse-based interface for a baseline comparison. Each interface allowed the user to build flight paths from a library of twelve individual trajectory segments. Individual user studies evaluated performance, efficacy, and ease-of-use of each interface using background surveys, subjective questionnaires, and observations on time and correctness. Analysis indicates that natural language interfaces are promising alternatives to traditional interfaces. The user study data collected on the efficacy and potential of each interface will be used to inform future intuitive UAV interface design for non-expert users.

Chandarana, Meghan↗
NASA NTRS1975

Abort-once-around entry corridor analysis program document

The abort once around entry target corridor analysis program (ABECAP) was studied. The allowable range of flight path angles at entry interface for acceptable entry trajectories from a shuttle abort once around (AOA) situation was established. The solutions thus determined may be shown as corridor plots of entry interface flight path angle versus range from entry interface (EI) to the target.

Kyle, H. C.↗
NASA NTRS1986

Validation of a new flying quality criterion for the landing task

A strong correlation has been found to exist between flight path angle peak overshoot and pilot ratings for the landing task. The use of flightpath overshoot as a flying quality metric for landing is validated by correlation with four different in-flight simulation programs and a ground simulation study. Configurations tested were primarily medium-weight generic transports. As a result of good correlation with this extensive data base, criterion boundaries are proposed for landing based on the flight path peak overshoot metric.

Berry, D. T.↗
NASA NTRS1990

DFW microburst model based on AA-539 data

Analysis of the August 2, 1985 crash for an L-1011 jumbo jet (DL-191) on approach to the Dallas-Ft. Worth International Airport (DFW) in a thunderstorm indicates that the severe windshear microburst that caused the crash was composed not only of a strong downflow and outflow but also included several large-scale vortex rings entrained in the flowfield. This paper presents a detailed two-dimensional model of the DFW microburst based on data from the MD-80 (AA-539) that followed behind DL-191 and flew through the microburst about two minutes after the crash of DL-191. The model was developed using wind-vector and flight-path data reconstructed by NASA Ames Research Center and a combination of interactive graphics and least-squares error best fit between the modeled and measured wind vectors along the AA-539 flight path. The model indicates that the flowfield contains some significant elements and vortices not previously reported. The alternating direction of rotation of the vortices in the model suggests a microburst structure based on a von Karman vortex street rather than on a Kelvin-Helmholtz instability. The model also indicates that the reconstructed wind-vector data contain a time lag of at least one second in the horizontal winds.

Grantham, Walter J.↗
NASA NTRS1984

Effects of aircraft and flight parameters on energy-efficient profile descents in time-based metered traffic

Concepts to save fuel while preserving airport capacity by combining time based metering with profile descent procedures were developed. A computer algorithm is developed to provide the flight crew with the information needed to fly from an entry fix to a metering fix and arrive there at a predetermined time, altitude, and airspeed. The flight from the metering fix to an aim point near the airport was calculated. The flight path is divided into several descent and deceleration segments. Descents are performed at constant Mach numbers or calibrated airspeed, whereas decelerations occur at constant altitude. The time and distance associated with each segment are calculated from point mass equations of motion for a clean configuration with idle thrust. Wind and nonstandard atmospheric properties have a large effect on the flight path. It is found that uncertainty in the descent Mach number has a large effect on the predicted flight time. Of the possible combinations of Mach number and calibrated airspeed for a descent, only small changes were observed in the fuel consumed.

Dejarnette, F. R.↗
NASA NTRS1989

Preliminary investigation of parameter sensitivities for atmospheric entry and aerobraking at Mars

The proposed manned Mars mission will need to be as weight efficient as possible. A way of lowering the weight of the vehicle by using aeroassist braking instead of retro-rockets to slow a craft once it reaches its destination is discussed. The two vehicles studied are a small vehicle similar in size to the Mars Rover Sample Return (MRSR) vehicle and a larger vehicle similar in size to a six-person Manned Mars Mission (MMM) vehicle. Simulated entries were made using various coefficients of lift (C sub L), coefficients of drag (C sub D), and lift-to-drag ratios (L/D). A range of acceptable flight path angles with their corresponding bank angle profiles was found for each case studied. These ranges were then compared, and the results are reported here. The sensitivity of velocity and acceleration to changes in flight path angle and bank angle is also included to indicate potential problem areas for guidance and navigation system design.

Lee, Mary C.↗
NASA NTRS1976

Maneuver sequence design for the post-Jupiter leg of Pioneer Saturn

After passing the planet Jupiter in December 1974, Pioneer 11 is on a flight path on which it will encounter Saturn in late 1979. Following an uncorrected trajectory, the spacecraft would pass 2 million km behind Saturn. A sequence of midcourse maneuvers for modifying the Pioneer trajectory is discussed. The corrected flight path is to bring the spacecraft within 500,000 km of Saturn's satellite Titan. Attention is given to maneuver capabilities and constraints, the maneuver design concept, questions related to the selection of an interim aimpoint, and aspects of maneuver implementation.

Frauenholz, R. B.↗
NASA NTRS1982

Evaluation of a trajectory command concept for manual control of carrier approaches and landings

A novel trajectory control system concept was implemented to provide manual control of a conventional jet aircraft. This concept, called Total Aircraft Flight Control System (TAFCOS), utilizes an inverse model of the aerodynamic and propulsion characteristics and employs feedforward control to provide the required acceleration command. The concept requires on-board digital computations which can easily be handled by a modern airborne computer. The system was studied in a piloted simulation of the carrier approach and landing task with primarily visual flight and guidance cues. The principal modes of vertical flight-path control investigated were vertical velocity command and vertical acceleration command. The study included manual carrier approaches with and without moderate ship motion and associated air disturbances, and tests of the effects of discrete gusts. Manual control of flight path through this new concept was shown to be feasible as an addition to an automatic control system and to have potential as an improved mode of control over conventional control for the carrier approach task.

Mcneill, W. E.↗
NASA NTRS1973

A new approach to performance optimization of the 1975 Mars Viking lander.

The design of the 1975 Viking lander is based, in part, upon performance optimization analyses and a requirement to maximize operational flexibility. The analysis technique is characterized by a graphical tradeoff approach found to be the most effective for evaluating lifting-entry trajectory performance. The analysis eliminates the constraint of a level flight trajectory and allows the lander to reach positive flight-path angles before parachute deployment. Updated Mars environmental knowledge and recent test results and design decisions are analysis factors. The entry-phase analysis indicates that a hypersonic lift-to-drag ratio of 0.18 and an entry flight-path-angle corridor of -15 to -19 deg satisfy the requirements of optimum performance (maximum payload and sufficient terrain height capability).

Zeiner, H. N.↗
NASA NTRS1973

Aircraft control system

An aircraft control system is described which is particularly suited to rotary wing aircraft. Longitudinal acceleration and course rate commands are derived from a manual control stick to control translational velocity of the aircraft along a flight path. In the collective channel the manual controls provide vertical velocity commands. In the yaw channel the manual controls provide sideslip or heading rate commands at high or low airspeeds, respectively. The control system permits pilots to fly along prescribed flight paths in a precise manner with relatively low work load.

Rempfer, P. S.↗
NASA NTRS1999

A Three-Dimensional Total Odd Nitrogen (NO(y)) Simulation During SONEX using a Stretched-Grid Chemical Transport Model

The relative importance of various odd nitrogen (NOy) sources including lightning, aircraft, and surface emissions on upper tropospheric total odd nitrogen is illustrated as a first application of the three-dimensional Stretched-Grid University of Maryland/Goddard Chemical-Transport Model (SG-GCTM). The SG-GCTM has been developed to look at the effect of localized sources and/or small scale mixing processes on the large-scale or global chemical balance. For this simulation, the stretched-arid was chosen so that its maximum resolution is located over eastern North America and the North Atlantic; a region that includes most of the SONEX (the SASS (Subsonic Assessment) Ozone and Nitrogen Oxides Experiment) flight paths. The SONEX period (October-November 1997) is simulated by driving the SG-GCTM with assimilated data from the GEOS-STRAT DAS (Goddard Earth Observing System-STRAT Data Assimilation System). A new algorithm is used to parameterize the lightning, flash rates that are needed to calculate emissions of NOy by lightning. Model-calculated upper tropospheric NOy and NOy measurements from the NASA DC-8 aircraft are compared. Spatial variations in NOy were well captured especially with the stretched-grid run; however, model-calculated concentrations were often too high in the upper troposphere, particularly during the first several flights. The lightning algorithm does a reasonably good job; however, the use of emissions from observed lightning, flashes significantly improves the simulation on a few occasions, especially November 3, 1997, indicating that significant uncertainty remains in parameterizing lightning in CTMS. Aircraft emissions play a relatively minor role (about 12%) in the upper tropospheric NOY budget averaged along SONEX flight paths; however, the contribution of such emmissions is as large as about 30% during portions of some flights.

Allen, Dale↗
NASA NTRS2019

Analyzing Error in Balloon-Based Wind Measurements Due to Spatial Separation Using the North American Regional Reanalysis

Weather balloons have been a longstanding asset to NASA and Aerospace meteorology. Balloons are used from launch vehicle design to day-of-launch operations. One of the most valuable assets from these balloons is wind data from the surface up to 30 kilometers. Due to aloft winds, the balloons may drift downrange of the launch site and vehicle flight path. A 2017 study found balloons at Kennedy Space Center (KSC) can drift as far as 200 kilometers from the launch site (Decker 2017). To obtain robust launch vehicle wind assessments, it is highly desirable to characterize the wind environment along the flight path. This study looks into the errors associated with spatial separation of wind measurements using the North American Regional Reanalysis (NARR).

Curtis, Nathan↗