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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Optimization and guidance of abort landing trajectories in a windshear

The abort landing problem for flight trajectories in the presence of windshear is considered with reference to flight in a vertical plane. The optimal trajectory (OT) problem is a minimax problem or Chebyshev problem of optimal control which can be converted into a Bolza problem through suitable transformations. Numerical results for several combinations of windshear intensities and initial altitudes are presented. A guidance trajectory (GT) law is implemented in feedback control form, subject to prescribed bounds on the angle of attack and its time derivative. Simplified guidance trajectories (SGT) are then considered, leading to a safe target altitude guidance. Conclusions derived for strong-to-severe windshear conditions include GT and SGT preserving the basic properties of OT, and the peak altitude drop of GT and SGT being less than that of the constant pitch trajectory and the maximum angle-of-attack trajectory.

Miele, A.↗
NASA NTRS1987

Optimal abort landing trajectories in the presence of windshear

The abort landing problem is considered with reference to flight in a vertical plane. It is assumed that, upon sensing that the aircraft is in a windshear, the pilot increases the power setting at a constant time rate until maximum power setting is reached; afterward, the power setting is held constant. The performance index being minimized is the peak value of the altitude drop; the resulting optimization problem is a minimax or Chebyshev problem of optimal control. It is found that, for strong-to-severe windshears, the optimal trajectory includes three branches: a descending flight branch followed by a nearly horizontal flight branch, followed by an ascending flight branch after the aircraft has passed through the shear region. The peak altitude drop depends on the windshear intensity, the initial altitude, and the power setting rate; it increases as the windshear intensity increases and the initial altitude increases, and it decreases as the power setting rate increases.

Miele, A.↗
NASA NTRS1988

Quasi-steady flight to quasi-steady flight transition for abort landing in a windshear - Trajectory optimization and guidance

Trajectory optimization and trajectory-guidance problems for abort-landing maneuvers in the presence of low-altitude wind shear are investigated by means of numerical simulations, with a focus on methods designed to achieve quasi-steady flight recovery (final values of the relative velocity, path inclination, and angle of attack equal to those for quasi-steady steepest climb). The derivation of the governing equations is outlined; the modeling techniques are explained; and results for a B-727 transport aircraft approaching a sea-level airfield at temperature 100 F are presented in extensive tables and graphs and characterized in detail. The techniques developed are shown to be effective in restoring the aircraft to stable quasi-steady flight.

Miele, A.↗
NASA NTRS1988

Transformation techniques for minimax optimal control problems and their application to optimal flight trajectories in a windshear - Optimal abort landing trajectories

The optimal-control problem of abort-landing trajectories in the presence of low-altitude wind shear is investigated analytically. The vertical-plane Newtonian motion of a point-mass aircraft in a steady wind field is modeled, and a sequential gradient-restoration algorithm is applied. Numerical results showing the effects of wind-shear intensity, initial altitude, and power-setting rate are presented in extensive graphs and discussed in detail. Optimal trajectories for strong or severe wind shears are found to begin with a descent, followed by level flight and then an ascent after leaving the shear region.

Miele, A.↗
NASA NTRS1989

Abort landing guidance trajectories in the presence of windshear

The flight trajectory of abort landing in the presence of windshear is examined with reference to flight in a vertical plane. It is assumed that the only control is the angle of attack. Inequality constraints are imposed on both the angle of attack and its time derivative. Numerical results are obtained for several combinations of windshear intensities and initial altitudes. Guidance trajectories are considered, approximating the optimal trajectories and using local information on the state of the aircraft, the initial altitude, and the total wind velocity difference. Results are presented for optimal trajectories, guidance trajectories, simplified guidance trajectories, constant pitch trajectories, and maximum angle of attack trajectories.

Miele, A.↗
NASA NTRS1989

Acceleration, gamma, and theta guidance for abort landing in a windshear

This paper is concerned with the guidance of abort landing trajectories in a windshear. First, optimal trajectories are determined by minimizing the peak value of the altitude drop. Then, two guidance schemes, approximating the optimal trajectors, are developed: acceleration guidance (based on the relative acceleration) and gamma guidance (based on the absolute path inclination). From numerical experiments, it appears that both the acceleration guidance and the gamma guidance yield trajectories that are close to the optimal trajectory. In addition, a theta guidance scheme (modified constant pitch guidance) is developed that is superior to the constant pitch guidance in terms of the altitude loss and the survival capability in severe windshears.

Miele, A.↗
NASA NTRS1989

Summary of miscellaneous hazard environments for hypothetical Space Shuttle and Titan IV launch abort accidents

The various analyses described here were aimed at obtaining a more comprehensive understanding and definition of the environments in the vicinity of the Radioisotope Thermal Generator (RTG) during certain Space Transportation System (STS) and Titan IV launch abort accidents. Addressed here are a number of issues covering explosion environments and General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG) responses to those environments.

Eck, M.↗
NASA NTRS1991

Shuttle abort landing site emergency medical services

NASA and DOD studies of medical-planning and logistical problems are reviewed as applicable to providing emergency medical care at remote transoceanic abort landing (TAL) sites. Two options are analyzed including a modified surgical response team and a combination physician/medical technician team. The two concepts are examined in terms of cost-effectiveness, specific types of medical support such as blood procurement, and search-and-rescue requirements. It is found that the physician/technician team is more economically efficient, and the description of the concept permits the development of an effective TAL-site astronaut medical-support system. A balance is struck between the competing problems of cost and medical capability by planning for on-scene medical stabilization and air evacuation to DOD tertiary medical centers.

Mckenas, David K.↗
NASA NTRS1993

Optimal RTLS abort trajectories for an HL-20 personnel launch vehicle

The primary objective of this study was to determine whether Return To Launch Site (RTLS) abort at T seconds along the launch trajectory of the Personnel Launch System (PLS) is possible using optimal control theory. The secondary objective is to assess effects of bank angle constraint, lift coefficient constraint, free and fixed final boundary conditions, etc. of the vehicle. The PLS is a complementary system to the Space Shuttle.

Dutton, Kevin↗
NASA NTRS2001

Recent CFD Simulations of Shuttle Orbiter Contingency Abort Aerodynamics

Modern Computational Fluid Dynamics (CFD) techniques were used to compute aerodynamic forces and moments of the Space Shuttle Orbiter in specific portions of contingency abort trajectory space. The trajectory space covers a Mach number range of 3.5-15, an angle-of-attack range of 20-60 degrees, an altitude range of 100-190 kft, and several different settings of the control surfaces (elevons, body flap, and speed brake). While approximately 40 cases have been computed, only a sampling of the results is presented here. The computed results, in general, are in good agreement with the Orbiter Operational Aerodynamic Data Book (OADB) data (i.e., within the uncertainty bands) for almost all the cases. However, in a limited number of high angle-of-attack cases (at Mach 15), there are significant differences between the computed results, especially the vehicle pitching moment, and the OADB data. A preliminary analysis of the data from the CFD simulations at Mach 15 shows that these differences can be attributed to real-gas/Mach number effects.

Papadopoulos, Periklis↗
NASA NTRS2004

Evaluation of the Space Shuttle Transatlantic Abort Landing Atmospheric Sounding System

This paper describes a study that was conducted to determine the quality of thermodynamic and wind data measured by the Space Shuttle Transatlantic Abort Landing (TAL) Atmospheric Sounding System (TASS). The system has Global Positioning System (GPS) tracking capability and provides profiles of atmospheric parameters such as temperature, relative humidity, and wind in support of potential emergency Space Shuttle landings at TAL sites. Ten comparison flights between the Low-Resolution Flight Element (LRFE) of the Automated Meteorological Profiling System (AMPS) and TASS were conducted at the Eastern Test Range (ETR) in early 2002. Initial results indicated that wind, temperature, and relative humidity compared well. However, incorrect GPS settings in the TASS software were resulting in altitude differences of about 60 to 70 m (approximately 200 to 230 ft) and air pressure differences of approximately 4 hectoPascals (hPa). TASS software updates to correct altitude data were completed in early 2003. Subsequent testing showed that altitude and air pressure differences were generally less than 5 m and 1 hPa, respectively.

Leahy, Frank B.↗
NASA NTRS1990

RS-88 Pad Abort Demonstrator Thrust Chamber Assembly Testing at NASA Marshall Space Flight Center

This paper documents the effort conducted to collect hot-tire dynamic and acoustics environments data during 50,000-lb thrust lox-ethanol hot-fire rocket testing at NASA Marshall Space Flight Center (MSFC) in November-December 2003. This test program was conducted during development testing of the Boeing Rocketdyne RS-88 development engine thrust chamber assembly (TCA) in support of the Orbital Space Plane (OSP) Crew Escape System Propulsion (CESP) Program Pad Abort Demonstrator (PAD). In addition to numerous internal TCA and nozzle measurements, induced acoustics environments data were also collected. Provided here is an overview of test parameters, a discussion of the measurements, test facility systems and test operations, and a quality assessment of the data collected during this test program.

Farr, Rebecca A.↗
NASA NTRS2007

Rapid Geometry Creation for Computer-Aided Engineering Parametric Analyses: A Case Study Using ComGeom2 for Launch Abort System Design

ComGeom2, a tool developed to generate Common Geometry representation for multidisciplinary analysis, has been used to create a large set of geometries for use in a design study requiring analysis by two computational codes. This paper describes the process used to generate the large number of configurations and suggests ways to further automate the process and make it more efficient for future studies. The design geometry for this study is the launch abort system of the NASA Crew Launch Vehicle.

Hawke, Veronica↗
NASA NTRS2007

Simulation Environment for Orion Launch Abort System Control Design Studies

The development and use of an interactive environment to perform control system design and analysis of the proposed Crew Exploration Vehicle Launch Abort System is described. The environment, built using a commercial dynamic systems design package, includes use of an open-source configuration control software tool and a collaborative wiki to coordinate between the simulation developers, control law developers and users. A method for switching between multiple candidate control laws and vehicle configurations is described. Aerodynamic models, especially in a development program, change rapidly, so a means for automating the implementation of new aerodynamic models is described.

McMinn, J. Dana↗
NASA NTRS2010

The Range Safety Debris Catalog Analysis in Preparation for the Pad Abort One Flight Test

With each flight test a Range Safety Data Package is assembled to understand the potential consequences of various failure scenarios. Debris catalog analysis considers an overpressure failure of the Abort Motor and the resulting debris field created 1. Characterize debris fragments generated by failure: weight, shape, and area 2. Compute fragment ballistic coefficients 3. Compute fragment ejection velocities.

Kutty, Prasad↗
NASA NTRS2010

Acoustic-Modal Testing of the Ares I Launch Abort System Attitude Control Motor Valve

The Attitude Control Motor (ACM) is being developed for use in the Launch Abort System (LAS) of NASA's Ares I launch vehicle. The ACM consists of a small solid rocket motor and eight actuated pintle valves that directionally allocate.thrust_- 1t.has-been- predicted-that significant unsteady. pressure.fluctuations.will.exist. inside the-valves during operation. The dominant frequencies of these oscillations correspond to the lowest several acoustic natural frequencies of the individual valves. An acoustic finite element model of the fluid volume inside the valve has been critical to the prediction of these frequencies and their associated mode shapes. This work describes an effort to experimentally validate the acoustic finite model of the valve with an acoustic modal test. The modal test involved instrumenting a flight-like valve with six microphones and then exciting the enclosed air with a loudspeaker. The loudspeaker was configured to deliver broadband noise at relatively high sound pressure levels. The aquired microphone signals were post-processed and compared to results generated from the acoustic finite element model. Initial comparisons between the test data and the model results revealed that additional model refinement was necessary. Specifically, the model was updated to implement a complex impedance boundary condition at the entrance to the valve supply tube. This boundary condition models the frequency-dependent impedance that an acoustic wave will encounter as it reaches the end of the supply tube. Upon invoking this boundary condition, significantly improved agreement between the test data and the model was realized.

Davis, R. Benjamin↗
NASA NTRS2010

Modeling the Launch Abort Vehicle's Subsonic Aerodynamics from Free Flight Testing

An investigation into the aerodynamics of the Launch Abort Vehicle for NASA's Constellation Crew Launch Vehicle in the subsonic, incompressible flow regime was conducted in the NASA Langley 20-ft Vertical Spin Tunnel. Time histories of center of mass position and Euler Angles are captured using photogrammetry. Time histories of the wind tunnel's airspeed and dynamic pressure are recorded as well. The primary objective of the investigation is to determine models for the aerodynamic yaw and pitch moments that provide insight into the static and dynamic stability of the vehicle. System IDentification Programs for AirCraft (SIDPAC) is used to determine the aerodynamic model structure and estimate model parameters. Aerodynamic models for the aerodynamic body Y and Z force coefficients, and the pitching and yawing moment coefficients were identified.

Hartman, Christopher L.↗
NASA NTRS2010

Orion Launch Abort Vehicle Separation Analysis Using OVERFLOW

This slide presentation reviews the use of OVERFLOW, a flow solver, to analyze the effect of separation for a launch abort vehicle (i.e., Orion capsule) if required. Included in the presentation are views of the geometry, and the Overset grids, listing of the assumptions, the general run strategy, inputs into the Overflow solver, the required computational resources, the results of the convergence study. Charts and graphics are presented to show the results.

Booth, Tom↗