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Lee, H. P.

Publications and source records attributed to Lee, H. P..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Development of the L-1011 four-dimensional flight management system

The development of 4-D guidance and control algorithms for the L-1011 Flight Management System is described. Four-D Flight Management is a concept by which an aircraft's flight is optimized along the 3-D path within the constraints of today's ATC environment, while its arrival time is controlled to fit into the air traffic flow without incurring or causing delays. The methods developed herein were designed to be compatible with the time-based en route metering techniques that were recently developed by the Dallas/Fort Worth and Denver Air Route Traffic Control Centers. The ensuing development of the 4-D guidance algorithms, the necessary control laws and the operational procedures are discussed. Results of computer simulation evaluation of the guidance algorithms and control laws are presented, along with a description of the software development procedures utilized.

Lee, H. P.↗
NASA NTRS1982

Advanced flight control system study

A fly by wire flight control system architecture designed for high reliability includes spare sensor and computer elements to permit safe dispatch with failed elements, thereby reducing unscheduled maintenance. A methodology capable of demonstrating that the architecture does achieve the predicted performance characteristics consists of a hierarchy of activities ranging from analytical calculations of system reliability and formal methods of software verification to iron bird testing followed by flight evaluation. Interfacing this architecture to the Lockheed S-3A aircraft for flight test is discussed. This testbed vehicle can be expanded to support flight experiments in advanced aerodynamics, electromechanical actuators, secondary power systems, flight management, new displays, and air traffic control concepts.

Hartmann, G. L.↗
NASA NTRS1982

NASTRAN thermal analyzer in a unified finite-element treatment of thermo-structural analyses

The NASTRAN thermal analyzer (NTA) which performs large-scale unified thermo-structural analyses with the NASTRAN (NASA structural analysis) computer program is described. The mathematical similitude between these two distinct disciplines of thermal and structure is examined. It serves as the theoretical basis upon which the implementation of the thermal capability in NASTRAN was accomplished. The program structure, the functional flow, the solution algorithms, the organization of an input data deck and the solution capabilities of NTA are summarized. Emphasis is placed on the interface of the unified approach in thermo-structural analyses where stresses, deflections, vibrations and bucklings induced by the effect of temperature change are of concern. Attentions are also directed to the preprocessor and post processors. As a specially designed preprocessor, the VIEW program is capable of generating exchange factors which can be output, at user's option, in formats compatible with that required by NTA. Two post processors that serve specific objectives are included. They are the thermal variance analysis and the graphical displaying capability of temperatures in color or black and white.

Lee, H. P.↗
NASA NTRS1980

On the application of nonlinear load elements to thermal analyses using the NASTRAN thermal analyzer

The nonlinear load elements in thermal analysis are used to simulate an undocumented nonlinear thermal boundary condition. The treatment of the nonlinearity arising from the temperature-dependent convective film coefficients is shown in detail. As an illustration, emphasis is placed on the modeling techniques and their interrelationships with the solution accuracy as affected by a specific integration algorithm of the transient thermal analysis used in the NASTRAN Thermal Analyzer. Briefly shown is the underlying theory on which the maneuvering of terms pertinent to the modeling depends. This demonstration provides some insight into the intricacies of the method that would be general to all applications. A recommendation is also made to modify a nonlinear load element that will enhance the solution capability and broaden the scope of application.

Lee, H. P.↗
NASA NTRS1980

Development of advanced avionics systems applicable to terminal-configured vehicles

A technique to add the time constraint to the automatic descent feature of the existing L-1011 aircraft Flight Management System (FMS) was developed. Software modifications were incorporated in the FMS computer program and the results checked by lab simulation and on a series of eleven test flights. An arrival time dispersion (2 sigma) of 19 seconds was achieved. The 4 D descent technique can be integrated with the time-based metering method of air traffic control. Substantial reductions in delays at today's busy airports should result.

Heimbold, R. L.↗
NASA NTRS1978

An assessment of thermal design procedures for Shuttle payloads

A review of the thermal design options for unmanned Shuttle payloads is presented. Because many future Shuttle payloads will have budgets and less time available for the definition of their thermal subsystems, simplified design procedures will be the most cost-effective. The thermal interface between an individual payload and the Orbiter is discussed. A simplified, modular thermal control system that will reduce the cost of providing thermal protection by minimizing both the initial procurement cost of any specialized hardware and the need for a detailed thermal interface analysis is described.

Almgren, D. W.↗
NASA NTRS1976

On modeling and the use of the NASTRAN thermal analyzer

Eight alternative modeling techniques to specify prescribed temperature at grid or scalar points for transient thermal analyses are presented. Four cases are for constant temperatures, and the others are time varying temperature functions. Theoretical explications and detailed listing of input data cards used for illustrating different modelings are given. It is shown that the NTA is exploited to extend beyond its normal capabilities through innovative modeling techniques. In addition, the effect of node valency on the energy distribution grid points is illustrated and discussed. Guidelines to delineate this effect are given.

Lee, H. P.↗
NASA NTRS1976

The GSFC NASTRAN thermal analyzer new capabilities

An overview of four analysis capabilities, which developed and integrated into the NASTRAN Thermal Analyzer, is given. To broaden the scope of applications, these additions provide the NTA users with the following capabilities: (1) simulating a thermal louver as a means of the passive thermal control, (2) simulating a fluid loop for transporting energy as a means of the active thermal control, (3) condensing a large sized finite element model for an efficient transient thermal analysis, and (4) entering multiple boundary condition sets in a single submission for execution in steady state thermal analyses.

Lee, H. P.↗
NASA NTRS1975

NASTRAN thermal analyzer status, experience, and new developments

The unique finite element based NASTRAN Thermal Analyzer originally developed as a general purpose heat transfer analysis incorporated into the NASTRAN system is described. The current status, experiences from field applications, and new developments are included.

Lee, H. P.↗
NASA NTRS1972

Structural-Thermal-Optical Program (STOP)

A structural thermal optical computer program is developed which uses a finite element approach and applies the Ritz method for solving heat transfer problems. Temperatures are represented at the vertices of each element and the displacements which yield deformations at any point of the heated surface are interpolated through grid points.

Lee, H. P.↗