Search NASA⌕ Search

SEARCH · Search NASA

Results for “Transient simulations”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Turbomachinery design for Space Shuttle auxiliary power systems.

Review of the major factors affecting Space Shuttle auxiliary power system design decisions, and discussion of turbine aerodynamic design optimization techniques. The working fluid to be used and the vehicle mission requirements are shown to be the two major factors that affect auxiliary power system design decisions. Analytical techniques developed for optimization of turbine aerodynamic design parameters are shown to be applicable to transient-state simulation and design optimization of other components, including the turbine controller.

Burriss, W. L.↗
NASA NTRS1976

Journal bearing impedance descriptions for rotordynamic applications

The paper deals with the development of analytic descriptions for plain circumferentially-symmetric fluid journal bearings, which are suitable for use in rotor dynamic analysis. The bearing impedance vector is introduced, which defines the bearing reaction force components as a function of the bearing motion. Impedances are derived directly for the Ocvirk (short) and Sommerfeld (long) bearings, and the relationships between the impedance vector and the more familiar mobility vector are developed and used to derive analytic impedance for finite-length bearings. The static correctness of the finite-length cavitating impedance is verified. Analytic stiffness and damping coefficient definitions are derived in terms of an impedance vector for small motion around an equilibrium position and demonstrated for the finite-length cavitating impedance. Nonlinear transient rotordynamic simulations are presented for the short pi and 2-pi impedances and the finite-length cavitating impedance. It is shown that finite-length impedance yields more accurate results for substantially less computer time than the short-bearing numerical-pressure-integration approach.

Childs, D.↗
NASA NTRS1980

Structural tests on a tile/strain isolation pad thermal protection system

The aluminum skin of the space shuttle is covered by a thermal protection system (TPS) consisting of a low density ceramic tile bonded to a matted-felt material called strain insulation pad (SIP). The structural characteristics of the TPS were studied experimentally under selected extreme load conditions. Three basic types of loads were imposed: tension, eccentrically applied tension, and combined in-plane force and transverse pressure. For some tests, transverse pressure was applied rapidly to simulate a transient shock wave passing over the tile. The failure mode for all specimens involved separation of the tile from the SIP at the silicone rubber bond interface. An eccentrically applied tension load caused the tile to separate from the SIP at loads lower than experienced at failure for pure tension loading. Moderate in-plane as well as shock loading did not cause a measurable reduction in the TPS ultimate failure strength. A strong coupling, however, was exhibited between in-plane and transverse loads and displacements.

Williams, J. G.↗
NASA NTRS1980

Orbiter integrated active thermal control subsystem test

Integrated subsystem level testing of the systems within the orbiter active thermal chamber capable of simulating ground, orbital, and entry temperature and pressure profiles. The test article was in a closed loop configuration that included flight type and functionally simulated protions of all ATCS components for collecting, transporting, and rejecting orbiter waste heat. Specially designed independently operating equipment simulated the transient thermal input from the cabin, payload, fuel cells, freon cold plates, hydraulic system, and space environment. Test team members using data, controls, and procedures available to a flight crew controlled the operation of the ATCS. The ATCS performance met or exceeded all thermal and operational requirements for planned and contingency mission support.

Jaax, J. R.↗
NASA NTRS1984

Data and results of a laboratory investigation of microprocessor upset caused by simulated lightning-induced analog transients

A methodology was developed a assess the upset susceptibility/reliability of a computer system onboard an aircraft flying through a lightning environment. Upset error modes in a general purpose microprocessor were studied. The upset tests involved the random input of analog transients which model lightning induced signals onto interface lines of an 8080 based microcomputer from which upset error data was recorded. The program code on the microprocessor during tests is designed to exercise all of the machine cycles and memory addressing techniques implemented in the 8080 central processing unit. A statistical analysis is presented in which possible correlations are established between the probability of upset occurrence and transient signal inputs during specific processing states and operations. A stochastic upset susceptibility model for the 8080 microprocessor is presented. The susceptibility of this microprocessor to upset, once analog transients have entered the system, is determined analytically by calculating the state probabilities of the stochastic model.

Belcastro, C. M.↗
NASA NTRS1983

Analysis, testing, and evaluation of faulted and unfaulted Wye, Delta, and open Delta connected electromechanical actuators

Mathematical models capable of simulating the transient, steady state, and faulted performance characteristics of various brushless dc machine-PSA (power switching assembly) configurations were developed. These systems are intended for possible future use as primemovers in EMAs (electromechanical actuators) for flight control applications. These machine-PSA configurations include wye, delta, and open-delta connected systems. The research performed under this contract was initially broken down into the following six tasks: development of mathematical models for various machine-PSA configurations; experimental validation of the model for failure modes; experimental validation of the mathematical model for shorted turn-failure modes; tradeoff study; and documentation of results and methodology.

Nehl, T. W.↗
NASA NTRS1984

Data and results of a laboratory investigation of microprocessor upset caused by simulated lightning-induced analog transients

Advanced composite aircraft designs include fault-tolerant computer-based digital control systems with thigh reliability requirements for adverse as well as optimum operating environments. Since aircraft penetrate intense electromagnetic fields during thunderstorms, onboard computer systems maya be subjected to field-induced transient voltages and currents resulting in functional error modes which are collectively referred to as digital system upset. A methodology was developed for assessing the upset susceptibility of a computer system onboard an aircraft flying through a lightning environment. Upset error modes in a general-purpose microprocessor were studied via tests which involved the random input of analog transients which model lightning-induced signals onto interface lines of an 8080-based microcomputer from which upset error data were recorded. The application of Markov modeling to upset susceptibility estimation is discussed and a stochastic model development.

Belcastro, C. M.↗
NASA NTRS1984

Development and application of a generalized transient computer program for Shuttle atmospheric pressure and composition control analysis

A generalized computer program for analysis of pressure and composition in a multiple-volume system has been developed by NASA. This paper describes the development of the program, outlines the program's capabilities, and illustrates the application of the program to Space Shuttle-related atmospheric pressure and composition control analyses. The program's features include the calculation of transient partial pressures of four gases in four volumes, an option for either isothermal or temperature-transient analyses, simulation of pressure and composition control hardware, and simulation involving 0-10 crewmembers. This computer program has been used successfully for a variety of Shuttle-related analyses to support hardware design, develop operating procedures, and provide real-time Shuttle mission support. Due to the versatility of this computer program, it will be utilized for Space Station program analyses.

Lafuse, S. A.↗
NASA NTRS1986

Estimating Transient Pressure Surges in Cryogenic Systems

Potentially-damaging pressure waves anticipated and, therefore, avoided. Mathematical model developed for prediction of pressure behavior in single-and two-phase cryogenic systems. Transient liquid-flow analysis modified to incorporate behavior of vapor bubbles and used to predict maximum pressure in cryogenic transfer systems consisting of complex pipe and valve arrangements under both steady-state and transient conditions. Simulation compared favorably with data obtained during transfer of liquid oxygen from ground storage tanks to Space Shuttle orbiter external tanks. Program written in FORTRAN 77 for batch execution.

Pfister, P.↗
NASA NTRS1988

Behavior Of Joint Seal In Solid Rocket Booster

Report analyzes behavior of O-ring seals in case of Solid Rocket Booster. Numerical simulations of transient response of seal presented with measurements of relevant mechanical properties of O-rings to show there is range of operating conditions in which seal can fail.

Moore, Carleton J.↗
NASA NTRS1988

Overview of numerical codes developed for predicted electrothermal deicing of aircraft blades

An overview of the deicing computer codes that have been developed at the University of Toledo under sponsorship of the NASA-Lewis Research Center is presented. These codes simulate the transient heat conduction and phase change occurring in an electrothermal deicier pad that has an arbitrary accreted ice shape on its surface. The codes are one-dimensional rectangular, two-dimensional rectangular, and two-dimensional with a coordinate transformation to model the true blade geometry. All modifications relating to the thermal physics of the deicing problem that have been incorporated into the codes will be discussed. Recent results of reformulating the codes using different numerical methods to increase program efficiency are described. In particular, this reformulation has enabled a more comprehensive two-dimensional code to run in much less CPU time than the original version. The code predictions are compared with experimental data obtained in the NASA-Lewis Icing Research Tunnel with a UH1H blade fitted with a B. F. Goodrich electrothermal deicer pad. Both continuous and cyclic heater firing cases are considered. The major objective in this comparison is to illustrate which codes give acceptable results in different regions of the airfoil for different heater firing sequences.

Keith, Theo G.↗
NASA NTRS1988

A comparison of numerical methods for the prediction of two-dimensional heat transfer in an electrothermal deicer pad

Transient, numerical simulations of the deicing of composite aircraft components by electrothermal heating have been performed in a 2-D rectangular geometry. Seven numerical schemes and four solution methods were used to find the most efficient numerical procedure for this problem. The phase change in the ice was simulated using the Enthalpy method along with the Method for Assumed States. Numerical solutions illustrating deicer performance for various conditions are presented. Comparisons are made with previous numerical models and with experimental data. The simulation can also be used to solve a variety of other heat conduction problems involving composite bodies.

Deicer↗
NASA NTRS1990

Numerical investigation of the transient SSME fuel preburner combustor flowfield

A computational fluid dynamics (CFD) model with finite-rate reactions, FDNS2DR, has been developed to study the start transient of the Space Shuttle Main Engine Fuel Preburner (FPB) operation. This design tool can predict accurately the severe thermal gradients which are impressed upon the fuel preburner and turbine during the start transient. An axisymmetric configuration with a grid size of 68 x 45 is used to represent the FPB flowfield. The transient upstream boundary conditions are obtained from a one-dimensional Digital Transient Model simulation to better represent the actual operation. The results of the CFD calculation show temperature spikes near the FPB exit whose timing and magnitude agree well with those of the measured turbine inlet temperature data.

Wang, Ten-See↗
NASA NTRS1991

SRB Environment Evaluation and Analysis. Volume 2: RSRB Joint Filling Test/Analysis Improvements

Following the Challenger accident a very comprehensive solid rocket booster (SRB) redesign program was initiated. One objective of the program was to develop expertise at NASA/MSFC in the techniques for analyzing the flow of hot gases in the SRB joints. Several test programs were undertaken to provide a data base of joint performance with manufactured defects in the joints to allow hot gases to fill the joints. This data base was used also to develop the analytical techniques. Some of the test programs were Joint Environment Simulator (JES), Nozzle Joint Environment Simulator (NJES), Transient Pressure Test Article (TPTA), and Seventy-Pound Charge (SPC). In 1988 the TPTA test hardware was moved from the Utah site to MSFC and several RSRM tests were scheduled, to be followed by tests for the ASRM program. REMTECH Inc. supported these activities with pretest estimates of the flow conditions in the test joints, and post-test analysis and evaluation of the measurements. During this support REMTECH identified deficiencies in the gas-measurement instrumentation that existed in the TPTA hardware, made recommendations for its replacement, and identified improvements to the analytical tools used in the test support. Only one test was completed under the TPTA RSRM test program, and those scheduled for the ASRM were rescheduled to a time after the expiration of this contract. The attention of this effort was directed toward improvements in the analytical techniques in preparation for when the ASRM program begins.

Knox, E. C.↗
NASA NTRS1992

ASDA - Advanced Suit Design Analyzer computer program

An ASDA model developed to evaluate the heat and mass transfer characteristics of advanced pressurized suit design concepts for low pressure or vacuum planetary applications is presented. The model is based on a generalized 3-layer suit that uses the Systems Integrated Numerical Differencing Analyzer '85 in conjunction with a 41-node FORTRAN routine. The latter simulates the transient heat transfer and respiratory processes of a human body in a suited environment. The user options for the suit encompass a liquid cooled garment, a removable jacket, a CO2/H2O permeable layer, and a phase change layer.

Bue, Grant C.↗
NASA NTRS1988

Eigenvalue/Eigenvector derivatives for SAVI Gimbalflex nonlinear transient response analysis

An eigenvector expansion method is utilized to predict eigenvalue and eigenvector derivatives due to geometric reconfiguration of a Gimbalflex fine-pointing/vibration isolation system called SAVI (Space Active Vibration Isolation). The eigenvector expansion method used is a modification of the classical method and allows for rigid body roots. Using the resulting modal derivatives, free-free nonlinear equations of motion are developed with Lagrange's Method. These equations represent a nonlinear plant model to be used in conjunction with a control system transient response simulation.

Orr, M. F., Jr.↗
NASA NTRS1992

Phase change energy storage for solar dynamic power systems

This paper presents the results of a transient computer simulation that was developed to study phase change energy storage techniques for Space Station Freedom (SSF) solar dynamic (SD) power systems. Such SD systems may be used in future growth SSF configurations. Two solar dynamic options are considered in this paper: Brayton and Rankine. Model elements consist of a single node receiver and concentrator, and takes into account overall heat engine efficiency and power distribution characteristics. The simulation not only computes the energy stored in the receiver phase change material (PCM), but also the amount of the PCM required for various combinations of load demands and power system mission constraints. For a solar dynamic power system in low earth orbit, the amount of stored PCM energy is calculated by balancing the solar energy input and the energy consumed by the loads corrected by an overall system efficiency. The model assumes an average 75 kW SD power system load profile which is connected to user loads via dedicated power distribution channels. The model then calculates the stored energy in the receiver and subsequently estimates the quantity of PCM necessary to meet peaking and contingency requirements. The model can also be used to conduct trade studies on the performance of SD power systems using different storage materials.

Chiaramonte, F. P.↗