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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

A Decision Tool that Combines Discrete Event Software Process Models with System Dynamics Pieces for Software Development Cost Estimation and Analysis

The development process for a large software development project is very complex and dependent on many variables that are dynamic and interrelated. Factors such as size, productivity and defect injection rates will have substantial impact on the project in terms of cost and schedule. These factors can be affected by the intricacies of the process itself as well as human behavior because the process is very labor intensive. The complex nature of the development process can be investigated with software development process models that utilize discrete event simulation to analyze the effects of process changes. The organizational environment and its effects on the workforce can be analyzed with system dynamics that utilizes continuous simulation. Each has unique strengths and the benefits of both types can be exploited by combining a system dynamics model and a discrete event process model. This paper will demonstrate how the two types of models can be combined to investigate the impacts of human resource interactions on productivity and ultimately on cost and schedule.

Mizell, Carolyn Barrett↗
NASA NTRS1981

Software models: A Bayesian approach to parameter estimation in the Jelenski-Moranda software reliability model

Maximum likelihood estimation procedures for the Jelinski-Moranda software reliability model often give misleading answers. A reparameterization and a Bayesian analysis eliminate some of the problems incurred by MLE methods and often give better predictions on sets of real and simulated data. Practical difficulties in estimating the initial number of errors N and the failure rate of each error phi by the method of maximum likelihood are: N, the MLE of N, is occasionally infinite (i.e., the routines for calculating N and phi do not converge). It is shown that N is finite sub i only if the regression line of the interevent times t sub i vs. i has positive slope. A serious problem is that often N approximates n, the sample size, and sometimes N = n. Thus the MLE predicts that the program is perfect even when it is far from being so. Only when almost all failures have been removed can N and phi be trusted near the end of debugging.

Littlewood, B.↗
NASA NTRS1988

Empirical studies of design software: Implications for software engineering environments

The empirical studies team of MCC's Design Process Group conducted three studies in 1986-87 in order to gather data on professionals designing software systems in a range of situations. The first study (the Lift Experiment) used thinking aloud protocols in a controlled laboratory setting to study the cognitive processes of individual designers. The second study (the Object Server Project) involved the observation, videotaping, and data collection of a design team of a medium-sized development project over several months in order to study team dynamics. The third study (the Field Study) involved interviews with the personnel from 19 large development projects in the MCC shareholders in order to study how the process of design is affected by organizationl and project behavior. The focus of this report will be on key observations of design process (at several levels) and their implications for the design of environments.

Krasner, Herb↗
NASA NTRS1996

Software Reliability Issues Concerning Large and Safety Critical Software Systems

This research was undertaken to provide NASA with a survey of state-of-the-art techniques using in industrial and academia to provide safe, reliable, and maintainable software to drive large systems. Such systems must match the complexity and strict safety requirements of NASA's shuttle system. In particular, the Launch Processing System (LPS) is being considered for replacement. The LPS is responsible for monitoring and commanding the shuttle during test, repair, and launch phases. NASA built this system in the 1970's using mostly hardware techniques to provide for increased reliability, but it did so often using custom-built equipment, which has not been able to keep up with current technologies. This report surveys the major techniques used in industry and academia to ensure reliability in large and critical computer systems.

Kamel, Khaled↗
NASA NTRS1994

Using Commercial Off-the-Shelf Software Tools for Space Shuttle Scientific Software

In October 1993, the Astronaut Science Advisor (ASA) was on board the STS-58 flight of the space shuttle. ASA is an interactive system providing data acquisition and analysis, experiment step re-scheduling, and various other forms of reasoning. As fielded, the system runs on a single Macintosh PowerBook 170, which hosts the six ASA modules. There is one other piece of hardware, an external (GW Instruments, Sommerville, Massachusetts) analog-to-digital converter connected to the PowerBook's SCSI port. Three main software tools were used: LabVIEW, CLIPS, and HyperCard: First, a module written in LabVIEW (National Instruments, Austin, Texas) controls the A/D conversion and stores the resulting data in appropriate arrays. This module also analyzes the numerical data to produce a small set of characteristic numbers or symbols describing the results of an experiment trial. Second, a forward-chaining inference system written in CLIPS (NASA) uses the symbolic information provided by the first stage with a static rule base to infer decisions about the experiment. This expert system shell is used by the system for diagnosis. The third component of the system is the user interface, written in HyperCard (Claris Inc. and Apple Inc., both in Cupertino, California).

Groleau, Nicolas↗
NASA NTRS2005

A Reusable and Adaptable Software Architecture for Embedded Space Flight System: The Core Flight Software System (CFS)

The contents include the following: High availability. Hardware is in harsh environment. Flight processor (constraints) very widely due to power and weight constraints. Software must be remotely modifiable and still operate while changes are being made. Many custom one of kind interfaces for one of a kind missions. Sustaining engineering. Price of failure is high, tens to hundreds of millions of dollars.

Wilmot, Jonathan↗
NASA NTRS2005

Incubator Display Software Cost Reduction Toolset Software Requirements Specification

The Incubator Display Software Requirements Specification was initially developed by Intrinsyx Technologies Corporation (Intrinsyx) under subcontract to Lockheed Martin, Contract Number NAS2-02090, for the National Aeronautics and Space Administration (NASA) Ames Research Center (ARC) Space Station Biological Research Project (SSBRP). The Incubator Display is a User Payload Application (UPA) used to control an Incubator subrack payload for the SSBRP. The Incubator Display functions on-orbit as part of the subrack payload laptop, on the ground as part of the Communication and Data System (CDS) ground control system, and also as part of the crew training environment.

Moran, Susanne↗
NASA NTRS2016

Advanced Spacesuit Informatics Software Design for Power, Avionics and Software Version 2.0

A description of the software design for the 2016 edition of the Informatics computer assembly of the NASAs Advanced Extravehicular Mobility Unit (AEMU), also called the Advanced Spacesuit. The Informatics system is an optional part of the spacesuit assembly. It adds a graphical interface for displaying suit status, timelines, procedures, and warning information. It also provides an interface to the suit mounted camera for recording still images, video, and audio field notes.

Instrumentation↗