Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “computer programs”

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 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Performance analysis of SA-3 missile second stage

One SA-3 missile was disassembled. The constituents of the second stage were thoroughly investigated for geometrical details. The second stage slotted composite propellant grain was subjected to mechanical properties testing, physiochemical analyses, and burning rate measurements at different conditions. To determine the propellant performance parameters, the slotted composite propellant grain was machined into a set of small-size tubular grains. These grains were fired in a small size rocket motor with a set of interchangeable nozzles with different throat diameters. The firings were carried out at three different conditions. The data from test motor firings, physiochemical properties of the propellant, burning rate measurement results and geometrical details of the second stage motor, were used as input data in a computer program to compute the internal ballistic characteristics of the second stage.

Helmy, A. M.↗
NASA NTRS1984

Topics in the optimization of millimeter-wave mixers

This report is in three parts: 1. In the first part a user-oriented computer program for the analysis of single-ended Schottky diode mixers is described. The program is used to compute the performance of a 140-220 GHz mixer and excellent agreement with measurements at 150 and 180 GHz is obtained. A sensitivity analysis indicates the importance of various diode and mount characteristics on the mixer performance. 2. The second part of this report describes a computer program for the analysis of varactor diode multipliers. The diode may operate in either the reverse biased varactor mode or with substantial forward current flow where the conversion mechanism is predominantly resistive. In addition, a design for a varactor diode doubler, tunable over an output frequency range of 150-220 GHz, is given. The doubler has 10-20% conversion efficiency with an instantaneous bandwidth of 3%. 3. The third section of this report contains a description and analysis of i new H-plane rectangular waveguide transformer. The transformer can be made luckily and easily in split-block waveguide using a standard slitting saw. It is particularly suited for use in the millimeter-wave band, replacing conventional electroformed stepped transformers. A theoretical analysis of the transformer is given, and good agreement is obtained with measurements made at X-band. Design curves are included for transitions which have a VSWR <1.2 over a full waveguide band when the impedance ratio is as high as 4 to 1.

Millimeter-wave↗
NASA NTRS1986

Graphics Programs for the DEC VAX Computer

Variety of plots available in video or printed form. LONGLIB library of computer programs set of subroutines designed for vector plotting on cathode-ray tubes and dot-matrix printers. LONGLIB subroutines invoked by program calls similar to standard CALCOMP routines. In addition to basic plotting routines, LONGLIB contains extensive set of routines to allow viewport clipping, extended character sets, graphic input, gray-level plots, polar plots, and three-dimensional plotting with or without removal of hidden lines. LONGLIB written in FORTRAN 77 and C for batch execution.

Long, D.↗
NASA NTRS1990

Computational methods for probability of instability calculations

This paper summarizes the development of the methods and a computer program to compute the probability of instability of a dynamic system than can be represented by a system of second-order ordinary linear differential equations. Two instability criteria based upon the roots of the characteristics equation or Routh-Hurwitz test functions are investigated. Computational methods based on system reliability analysis methods and importance sampling concepts are proposed to perform efficient probabilistic analysis. Numerical examples are provided to demonstrate the methods.

Wu, Y.-T.↗
NASA NTRS1991

Calculating Flow Through A Helicopter Rotor

New method for calculating flow of air through and around helicopter rotor incorporated into General Rotorcraft Aeromechanical Stability Program (GRASP) (computer program for aeroelastic analysis). Flow about helicopter rotor represented by axisymmetric flow field in cylindrical region with actuator disk as source of flow.

Kunz, Donald L.↗
NASA NTRS1991

Navier-Stokes Computations On Zonal Grids

Report describes numerical simulations of transonic flow of air about isolated wing and about wing and fuselage (not tail assembly) of F-16A aircraft. Fast, diagonalized Beam-Warming numerical-integration algorithm for solution of Euler and Navier-Stokes equations applied via Transonic Navier-Stokes computer program, using computational grids divided into zones of coarse and finer meshes.

Flores, Jolen↗
NASA NTRS1991

Inverse problem in incompressible, irrotational axisymmetric flow

A vortex-sheet method for solving the axisymmetric inverse problem is presented, and an iterative, interactive computer program for computing the body shape starting from an assumed shape is developed. The method eliminates the calculation of the direct problem at every iteration using the given velocity. The singular integral that arises in the problem formulation has been integrated analytically. The efficiency of the vortex-sheet method is demonstrated using three test cases, and the obtained body shapes and the corresponding surface velocity distributions are presented.

Dinavahi, Surya P. G.↗
NASA NTRS1991

Probabilistic methods for rotordynamics analysis

This paper summarizes the development of the methods and a computer program to compute the probability of instability of dynamic systems that can be represented by a system of second-order ordinary linear differential equations. Two instability criteria based upon the eigenvalues or Routh-Hurwitz test functions are investigated. Computational methods based on a fast probability integration concept and an efficient adaptive importance sampling method are proposed to perform efficient probabilistic analysis. A numerical example is provided to demonstrate the methods.

Wu, Y.-T.↗
NASA NTRS2007

Flyby Geometry Optimization Tool

The Flyby Geometry Optimization Tool is a computer program for computing trajectories and trajectory-altering impulsive maneuvers for spacecraft used in radio relay of scientific data to Earth from an exploratory airplane flying in the atmosphere of Mars.

Karlgaard, Christopher D.↗
NASA NTRS1989

A distributed program composition system

A graphical technique for creating distributed computer programs is investigated and a prototype implementation is described which serves as a testbed for the concepts. The type of programs under examination is restricted to those comprising relatively heavyweight parts that intercommunicate by passing messages of typed objects. Such programs are often presented visually as a directed graph with computer program parts as the nodes and communication channels as the edges. This class of programs, called parts-based programs, is not well supported by existing computer systems; much manual work is required to describe the program to the system, establish the communication paths, accommodate the heterogeneity of data types, and to locate the parts of the program on the various systems involved. The work described solves most of these problems by providing an interface for describing parts-based programs in this class in a way that closely models the way programmers think about them: using sketches of diagraphs. Program parts, the computational modes of the larger program system are categorized in libraries and are accessed with browsers. The process of programming has the programmer draw the program graph interactively. Heterogeneity is automatically accommodated by the insertion of type translators where necessary between the parts. Many decisions are necessary in the creation of a comprehensive tool for interactive creation of programs in this class. Possibilities are explored and the issues behind such decisions are presented. An approach to program composition is described, not a carefully implemented programming environment. However, a prototype implementation is described that can demonstrate the ideas presented.

Brown, Robert L.↗
NASA NTRS1975

Study of Synthetic Aperture Radar (SAR) imagery characteristics

Sources of geometric and radiometric fidelity errors in AN/APQ-102A radar imagery are discussed, along with a digital computer program to correct the distortions. The major effort, a computer program which will process digitalized recorded AN/APQ-102A phase histories into imagery, is described. All computer programs are listed.

Source record↗
NASA NTRS2018

High-Performance Spaceflight Computing (HPSC) Program Overview

The High Performance Spaceflight Computing (HPSC) project is dramatically advancing the state of the art for spaceflight computing, providing both increased performance and greater operational flexibility. Initial studies derived an reference architecture for the HPSC Chiplet, and this has evolved as development has progress. NASA and JPL are jointly developing HPSC Middleware to ease the development of future applications for the Chiplet. Several NASA use cases are identified for HPSC, ranging from smallsats to crewed missions.

avionics↗