If a set of N points or nodes with a nonnegative cost associated with each ordered pair is known, it is desired to find a path from one given node to another given node which minimizes the cost sum. An algorithm is presented which yields a global minimum solution after at most N - 1 iterations or on a typical large third-generation computer, after 1 hour of computation time for a 10,000-node problem. The rapid-access data storage capacity demanded by the algorithm is approximately 3N words for...
Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, CRITICAL PATH METHOD, HUYGENS PRINCIPLE, COST...
The method proposed tries to enumerate all the critical fault-patterns (successive occurrences of failures) without analyzing every single possible fault. The conditions for the system to be operating in a given mode can be expressed in terms of the static states. Thus, one can find all the system states that correspond to a given critical mode of operation. The next step consists in analyzing the fault-detection mechanisms, the diagnosis algorithm and the process of switch control. From them,...
Topics: NASA Technical Reports Server (NTRS), CRITICAL PATH METHOD, DIGITAL SYSTEMS, FAILURE ANALYSIS,...
The Network Generation Program (NETGEN), which creates logic networks from task chart data is presented. NETGEN is written in CDC FORTRAN IV (Extended) and runs in a batch mode on the CDC 6000 and CYBER 170 series computers. Data is input via a two-card format and contains information regarding the specific tasks in a project. From this data, NETGEN constructs a logic network of related activities with each activity having unique predecessor and successor nodes, activity duration, descriptions,...
Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMS, CRITICAL PATH METHOD, LOGIC CIRCUITS,...
Several existing computer programs for estimating life cycle cost of mining systems were evaluated. A commercially available program, ADAM/1 was found to be satisfactory in relation to the needs of the advanced coal extraction project. Two test cases were run to confirm the ability of the program to handle nonconventional mining equipment and procedures. The results were satisfactory. The model, therefore, is recommended to the project team for evaluation of their conceptual designs.
Topics: NASA Technical Reports Server (NTRS), COAL, COMPUTER PROGRAMS, MINING, BOREHOLES, COMPUTERIZED...
The measurement of rainfall by remote sensors is investigated. One parameter radar rainfall measurement is limited because both reflectivity and rain rate are dependent on at least two parameters of the drop size distribution (DSD), i.e., representative raindrop size and number concentration. A generalized rain parameter diagram is developed which includes a third distribution parameter, the breadth of the DSD, to better specify rain rate and all possible remote variables. Simulations show the...
Topics: NASA Technical Reports Server (NTRS), DROP SIZE, PARTICLE DENSITY (CONCENTRATION), PARTICLE SIZE...
The use of auditory displays for selected cockpit instruments was examined. In auditory, visual, and combined auditory-visual compensatory displays of a vertical axis, critical tracking task were studied. The visual display encoded vertical error as the position of a dot on a 17.78 cm, center marked CRT. The auditory display encoded vertical error as log frequency with a six octave range; the center point at 1 kHz was marked by a 20-dB amplitude notch, one-third octave wide. Asymptotic...
Topics: NASA Technical Reports Server (NTRS), AUDITORY TASKS, CRITICAL PATH METHOD, DISPLAY DEVICES, MANUAL...
An interactive fracture mechanics program was developed in BASIC minima on a CBM 4032 microcomputer. It furnishes stress intensity factors and the critical size of a flaw.
Topics: NASA Technical Reports Server (NTRS), COMPUTER SYSTEMS PROGRAMS, FRACTURE MECHANICS,...
The design and construction of embedded operating systems for real-time advanced aerospace applications was investigated. The applications require reliable operating system support that must accommodate computer networks. Problems that arise in the construction of such operating systems, reconfiguration, consistency and recovery in a distributed system, and the issues of real-time processing are reported. A thesis that provides theoretical foundations for the use of atomic actions to support...
Topics: NASA Technical Reports Server (NTRS), AEROSPACE ENGINEERING, COMPUTER NETWORKS, EMBEDDING, FAULT...
Some path-following techniques are described and compared with other methods. Use of multipurpose techniques that can be used at more than one stage of the path-following computation results in a system that is relatively simple to understand, program, and use. Comparison of path-following methods with the method of parametric differentiation reveals definite advantages for the path-following methods. The fact that parametric differentiation has found a broader range of applications indicates...
Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMMING, CRITICAL PATH METHOD, DIFFERENTIAL...
An investigation performed for NASA LeRC by COMSAT Labs, of a digitally implemented on-board demultiplexer/demodulator able to process a mix of uplink carriers of differing bandwidths and center frequencies and programmable in orbit to accommodate variations in traffic flow is reported. The processor accepts high speed samples of the signal carried in a wideband satellite transponder channel, processes these as a composite to determine the signal spectrum, filters the result into individual...
Topics: NASA Technical Reports Server (NTRS), DEMODULATION, DEMULTIPLEXING, MULTICHANNEL COMMUNICATION,...
A FORTRAN program describing the vibration modes of a rotor-bearing system is analyzed for parellelism in this simulation using a Pascal-like structured language. Potential vector operations are also identified. A critical path through the simulation is identified and used in conjunction with somewhat fictitious processor characteristics to determine the time to calculate the problem on a parallel processing system having those characteristics. A parallel processing overhead time is included as...
Topics: NASA Technical Reports Server (NTRS), COMPUTERIZED SIMULATION, PARALLEL PROCESSING (COMPUTERS),...
The problem of finding the distribution of the shortest path length through a stochastic network is investigated. A general algorithm for determining the exact distribution of the shortest path length is developed based on the concept of conditional factoring, in which a directed, stochastic network is decomposed into an equivalent set of smaller, generally less complex subnetworks. Several network constructs are identified and exploited to reduce significantly the computational effort required...
Topics: NASA Technical Reports Server (NTRS), COMMUNICATION NETWORKS, CRITICAL PATH METHOD, DATA LINKS,...
The technical requirements and performance of a first generation space interferometer is discussed. The performance of an interferometer, sensitivity, field of view, dynamic range, astrometric accuracy, etc, in space is set by what cannot be achieved for a ground-based instrument. For the Orbiting Space Interferometer (OSI), the nominal performance parameters are 20 mag sensitivity, field of view of approximately 500*500 pixels, a 1000:1 dynamic range in the image with one milliarcsec...
Topics: NASA Technical Reports Server (NTRS), ASTROMETRY, FAINT OBJECTS, OPTICAL PATHS, OSO, STELLAR...
This report describes Aerojet's methods and procedures used to control and administer contractual schedules for the EOS/AMSU-A program. Included are the following: the master, intermediate, and detail schedules; critical path analysis; and the total program logic network diagrams.
Topics: NASA Technical Reports Server (NTRS), EARTH OBSERVING SYSTEM (EOS), MICROWAVE SOUNDING, PROJECT...
The following topics are discussed concerning scheduling: (1) milestone scheduling; (2) network scheduling; (3) program evaluation and review technique; (4) critical path method; (5) developing a network; (6) converting an ugly duckling to a swan; (7) network scheduling problem; (8) (9) network scheduling when resources are limited; (10) multi-program considerations; (11) influence on program performance; (12) line-of-balance technique; (13) time management; (14) recapitulization; and (15)...
Topics: NASA Technical Reports Server (NTRS), CRITICAL PATH METHOD, MANAGEMENT METHODS, MULTIPROGRAMMING,...
In recent years a variety of space-activity schedulers have been developed within the aerospace community. Space-activity schedulers are characterized by their need to handle large numbers of activities which are time-window constrained and make high demands on many scarce resources, but are minimally constrained by predecessor/successor requirements or critical paths. Two needs to exchange data between these schedulers have materialized. First, there is significant interest in comparing and...
Topics: NASA Technical Reports Server (NTRS), AEROSPACE INDUSTRY, CRITICAL PATH METHOD, INTERNATIONAL SPACE...
POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometric measurements from space, yielding submicroarcsecond astrometric results from the mission. It comprises a pair of independent Michelson stellar interferometers and a laser metrology system that measures both the critical starlight paths and the angle between the baselines. The instrument has two baselines of 2 m, each with two subapertures of 35 cm; by articulating the angle between the baselines,...
Topics: NASA Technical Reports Server (NTRS), OPTICAL MEASURING INSTRUMENTS, ASTROMETRY, OPTICAL...
This report summarizes the chronology, results, and lessons learned from the development of the SSFF-MIS. This system has been nearly two years in development and has yielded some valuable insights into specialized MIS development. General: In December of 1994, the Camber Corporation and Science Applications International Corporation (SAIC) were contracted to design, develop, and implement a MIS for Marshall Space Flight Center's Space Station Furnace Facility Project. The system was to be...
Topics: NASA Technical Reports Server (NTRS), SPACE STATIONS, FURNACES, CAMBER, SYSTEMS ENGINEERING,...
Thios report summarizes the chronology, results, and lessons learned from the development of the SSFF-MIS. This system has been nearly two years in development and has yielded some valuable insights into specialized MIS development. Attachment A contains additions, corrections, and deletions by the COTR.
Topics: NASA Technical Reports Server (NTRS), MANAGEMENT INFORMATION SYSTEMS, SYSTEMS ENGINEERING,...
One of the most recent techniques for propagating resource constraints in Constraint Based scheduling is Energy Constraint. This technique focuses in precedence based scheduling, where precedence relations are taken into account rather than the absolute position of activities. Although, this particular technique proved to be efficient on discrete unary resources, it provides only loose bounds for jobs using discrete multi-capacity resources. In this paper we show how mutual exclusion reasoning...
Topics: NASA Technical Reports Server (NTRS), EXCLUSION, PROPAGATION, CRITICAL PATH METHOD, MATHEMATICAL...
The Bioastronautics Critical Path Roadmap is the framework used to identify and assess the risks to crews exposed to the hazardous environments of space. It guides the implementation of research strategies to prevent or reduce those risks. Although the BCPR identifies steps that must be taken to reduce the risks to health and performance that are associated with human space flight, the BCPR is not a "critical path" analysis in the strict engineering sense. The BCPR will evolve to...
Topics: NASA Technical Reports Server (NTRS), BIOASTRONAUTICS, AEROSPACE ENVIRONMENTS, PROJECT MANAGEMENT,...
Currently, the most common approach used in project planning tools is the Critical Path Method (CPM). While this method was a great improvement over the basic Gantt chart technique being used at the time, it now suffers from three primary flaws: (1) task duration is an input, (2) productivity impacts are not considered , and (3) management corrective actions are not included. Today, computers have exceptional computational power to handle complex simulations of task e)(eculion and project...
Topics: NASA Technical Reports Server (NTRS), PROJECT MANAGEMENT, SIMULATION, COST ESTIMATES, CRITICAL PATH...
In Fiscal Year 2011 Dryden Flight Research Center (DFRC) implemented a new project management system called Critical Chain Project Management (CCPM). Recent NASA audits have found that the Dryden workforce is strained under increasing project demand and that multi-tasking has been carried to a whole new level at Dryden. It is very common to have an individual work on 10 different projects during a single pay period. Employee surveys taken at Dryden have identified work/life balance as the...
Topics: NASA Technical Reports Server (NTRS), PROJECT MANAGEMENT, MANAGEMENT SYSTEMS, PROJECT PLANNING,...
This presentation demonstrates how the ASRC Scheduling team developed working practices to support multiple NASA and ASRC Project Managers using the enterprise capabilities of Primavera P6 and P6 Web Access. This work has proceeded as part of Kennedy Ground Systems' preparation for its transition from the Shuttle Program to the Constellation Program. The presenters will cover Primavera's enterprise-class capabilities for schedule development, integrated critical path analysis, and reporting, as...
Topics: NASA Technical Reports Server (NTRS), PROJECT PLANNING, SCHEDULING, CONSTELLATION PROGRAM, MANNED...
The Space Launch System (SLS) Program is essential to achieving the Nation's and NASA's goal of human exploration and scientific investigation of the solar system. As a multi-element program with emphasis on safety, affordability, and sustainability, SLS is becoming America's next great ship of exploration. The SLS Core Stage includes avionics, main propulsion system, pressure vessels, thrust vector control, and structures. Boeing manufactures and assembles the SLS core stage at the Michoud...
Topics: NASA Technical Reports Server (NTRS), SPACE PROGRAMS, MANUFACTURING, SAFETY, PROJECT MANAGEMENT,...
