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At least 631 records · Page 35

Lewis' enhanced laboratory for research into the fatigue and constitutive behavior of high temperature materials

Lewis Research Center's high temperature fatigue laboratory has undergone significant changes resulting in the addition of several new experimental capabilities. New materials testing systems have been installed enabling research to be conducted in multiaxial fatigue and deformation at high temperature, as well as cumulative creep-fatigue damage wherein the relative failure-life levels are widely separated. A key component of the new high-temperature fatigue and structures laboratory is a local, distributed computer system whose hardware and software architecture emphasizes a high degree of configurability, which in turn, enables the researcher to tailor a solution to the problem at hand.

Mcgaw, Michael A.↗

Integrated tracking of components by engineering and logistics utilizing logistics asset tracking system

The Logistics Asset Tracking System (LATS) devised by NASA contains data on Space Shuttle LRUs that are daily updated to reflect such LRU status changes as repair due to failure or modification due to changing engineering requirements. The implementation of LATS has substantially increased personnel responsiveness, preventing costly delays in Space Shuttle processing and obviating hardware cannibalization. An evaluation is presented of LATS achievements in the direction of an integrated logistical support posture.

Renfroe, Michael B.↗

Design Criteria for Controlling Stress Corrosion Cracking

This document sets forth the criteria to be used in the selection of materials for space vehicles and associated equipment and facilities so that failure resulting from stress corrosion will be prevented. The requirements established herein apply to all metallic components proposed for use in space vehicles and other flight hardware, ground support equipment, and facilities for testing. These requirements are applicable not only to items designed and fabricated by MSFC (Marshall Space Flight Center) and its prime contractors, but also to items supplied to the prime contractor by subcontractors and vendors.

Franklin, D. B.↗

Strategy for Developing Technologies for Megawatt-class Nuclear Electric Propulsion Systems

A strategy for maturing the technologies required for a megawatt-class nuclear electric propulsion (NEP) system is presented. The effort is responsive to recent non-advocate reviews stating high-power NEP technologies were relatively immature and significant maturation was required before contemplating the use of NEP on a flight mission. The maturation strategy presented accomplishes this through hardware test and evaluation at the sizes, scales, and conditions expected during high-power NEP missions. The development effort is accompanied by modeling of such a system to demonstrate thorough understanding and verification of the performance, lifetime, and failure modes. The proposed effort uses a building-block approach, maturing technologies for a 1 MWe block under the assumption that a future high-power NEP mission will have requirements that can be met either through straightforward scaling of this building block to the levels required or through the use of multiple blocks to meet the overall power needs. The plan is outlined for maturation to technology readiness level 5, characterized by test and evaluation using brassboard-fidelity hardware in a relevant environment and by demonstration of agreement between test data and analytical predictions.

Kurt A. Polzin↗

Communication Research in Aviation and Space Operations: Symptoms and Strategies of Crew Coordination

The day-to-day operators of today's aerospace systems work under increasing pressures to accomplish more with less. They work in operational systems which are complex, technology-based, and high-risk; in which incidents and accidents have far-reaching and costly consequences. For these and other reasons, there is concern that the safety net formerly built upon redundant systems and abundant resources may become overburdened. Although we know that human ingenuity can overcome incredible odds, human nature can also fail in unpredictable ways. Over the last 20 years, a large percentage of aviation accidents and incidents have been attributed to human errors rather than hardware or environmental factors alone. A class of errors have been identified which are not due to a lack of individual, technical competencies. Rather, they are due to the failure of teams to utilize readily available resources or information in a timely fashion. These insights began a training revolution in the aviation industry called Cockpit Resource Management, which later became known as Crew Resource Management (CRM) as its concepts and applications extended to teams beyond the flightdeck. Then, as now, communication has been a cornerstone in CRM training since crew coordination and resource management largely resides within information transfer processes--both within flightcrews, and between flightcrews and the ground operations teams that support them. The research I will describe takes its roots in CRM history as we began to study communication processes in order to discover symptoms of crew coordination problems, as well as strategies of effective crew management. On the one hand, communication is often the means or the tool by which team members manage their resources, solve problems, maintain situational awareness and procedural discipline. Conversely, it is the lack of planning and resource management, loss of vigilance and situational awareness, and non-standard communications that are implicated in accidents and incidents. NASA/Ames Crew Factors researchers have been developing a model of effective crew coordination in order to understand the sources of performance breakdowns, and to develop effective solutions and interventions. Because communication is a primary mechanism by which information is received and transmitted, and because it is observable behavior, we focus on these group processes in order to identify patterns of communication that distinguish effective from less effective crew performance. Since a prime objective is to develop training recommendations for enhancing communication skills, we interpret our findings in the context of relevant task and environmental conditions, role and procedural constraints, and the normal real-time parameters of flight operations. Another research objective is to consider how communication and coordination can be enhanced through design. For example, flight deck and hardware design as well as procedural and software design may greatly influence the efficiency with which crews communicate and coordinate their work. In addition, teams and tasks may be designed, organized, and trained so that team interactions with each other are based upon appropriately shared knowledge, procedures and situation awareness. In short, we are interested in enhancing communication practices through (1) the training of specific communication skills, and (2) the design of equipment, tasks, procedures, and teams that optimize smooth, unambiguous communication processes. Two examples of communication research will be described; one in aviation and one in space operations. The first example is a high-fidelity full mission simulation study which investigates the affect of flightdeck automation on crew coordination and communication (contrasting crew performance in the DC-9 vs. MD88). Additional information is contained in the original extended abstract.

Kanki, Barbara G.↗

Use of Probabilistic Engineering Methods in the Detailed Design and Development Phases of the NASA Ares Launch Vehicle

The United States National Aeronautics and Space Administration (NASA) is in the midst of a space exploration program called Constellation to send crew and cargo to the international Space Station, to the moon, and beyond. As part of the Constellation program, a new launch vehicle, Ares I, is being developed by NASA Marshall Space Flight Center. Designing a launch vehicle with high reliability and increased safety requires a significant effort in understanding design variability and design uncertainty at the various levels of the design (system, element, subsystem, component, etc.) and throughout the various design phases (conceptual, preliminary design, etc.). In a previous paper [1] we discussed a probabilistic functional failure analysis approach intended mainly to support system requirements definition, system design, and element design during the early design phases. This paper provides an overview of the application of probabilistic engineering methods to support the detailed subsystem/component design and development as part of the "Design for Reliability and Safety" approach for the new Ares I Launch Vehicle. Specifically, the paper discusses probabilistic engineering design analysis cases that had major impact on the design and manufacturing of the Space Shuttle hardware. The cases represent important lessons learned from the Space Shuttle Program and clearly demonstrate the significance of probabilistic engineering analysis in better understanding design deficiencies and identifying potential design improvement for Ares I. The paper also discusses the probabilistic functional failure analysis approach applied during the early design phases of Ares I and the forward plans for probabilistic design analysis in the detailed design and development phases.

Fayssal, Safie↗

3-D CFD Simulation and Validation of Oxygen-Rich Hydrocarbon Combustion in a Gas-Centered Swirl Coaxial Injector using a Flamelet-Based Approach

Injector design is a critical part of the development of a rocket Thrust Chamber Assembly (TCA). Proper detailed injector design can maximize propulsion efficiency while minimizing the potential for failures in the combustion chamber. Traditional design and analysis methods for hydrocarbon-fuel injector elements are based heavily on empirical data and models developed from heritage hardware tests. Using this limited set of data produces challenges when trying to design a new propulsion system where the operating conditions may greatly differ from heritage applications. Time-accurate, Three-Dimensional (3-D) Computational Fluid Dynamics (CFD) modeling of combusting flows inside of injectors has long been a goal of the fluid analysis group at Marshall Space Flight Center (MSFC) and the larger CFD modeling community. CFD simulation can provide insight into the design and function of an injector that cannot be obtained easily through testing or empirical comparisons to existing hardware. However, the traditional finite-rate chemistry modeling approach utilized to simulate combusting flows for complex fuels, such as Rocket Propellant-2 (RP-2), is prohibitively expensive and time consuming even with a large amount of computational resources. MSFC has been working, in partnership with Streamline Numerics, Inc., to develop a computationally efficient, flamelet-based approach for modeling complex combusting flow applications. In this work, a flamelet modeling approach is used to simulate time-accurate, 3-D, combusting flow inside a single Gas Centered Swirl Coaxial (GCSC) injector using the flow solver, Loci-STREAM. CFD simulations were performed for several different injector geometries. Results of the CFD analysis helped guide the design of the injector from an initial concept to a tested prototype. The results of the CFD analysis are compared to data gathered from several hot-fire, single element injector tests performed in the Air Force Research Lab EC-1 test facility located at Edwards Air Force Base.

Richardson, Brian↗

Insights into the Behavior of Potential Structural Failures Originating from Localized High Stress Regions in Configurations Relevant to Solid Rocket Motor Nozzles

During the structural certification effort for the Space Launch System solid rocket booster nozzle, it was identified that no consistent method for addressing local negative margins of safety in non-metallic materials had been developed. Relevant areas included bond-line terminations and geometric features in the composite nozzle liners. In order to gain understanding, analog test specimens were designed that very closely mimic the conditions in the actual full scale hardware. Different locations in the nozzle were represented by different analog specimen designs. This paper describes those tests and corresponding results. Finite element analysis results for the tests are presented. Strain gage correlation of the analysis to the test results is addressed. Furthermore, finite fracture mechanics (a coupled stress and energy failure criterion) is utilized to predict the observed crack pop-in loads for the different configurations. The finite fracture mechanics predictions are found to be within a 10% error relative to the average measured pop-in load for each of four configurations. Initiation locations, arrest behaviors, and resistances to further post-arrest crack propagation are also discussed.

McCutcheon, David Matthew↗

Systems special investigation group overview

The Systems Special Investigation Group (SIG) has undertaken investigations in the four major engineering disciplines represented by LDEF hardware: electrical, mechanical, thermal, and optical systems. Testing was planned for the highest possible level of assembly, and top level system tests for nearly all systems were performed at this time. Testing to date was performed on a mix of LDEF and individual experimenter systems. No electrical or mechanical system level failures attributed to the spaceflight environment were detected by the Systems SIG. Some low cost electrical components were used successfully, although relays were a continuing problem. Extensive mechanical galling was observed, but no evidence of coldwelding was identified. A working index of observed systems anomalies was created and will be used to support the tracking and resolution of these effects. LDEF hardware currently available to the Systems SIG includes most of the LDEF facility systems hardware, and some significant experimenter hardware as well. A series of work packages was developed for each of several subsystem types where further testing is of critical interest. The Systems SIG is distributing a regular newsletter to the greater LDEF community in order to maintain coherence in an investigation which is widely scattered both in subject matter and in geography. Circulation of this informal document has quadrupled in its first year.

James B Mason↗

Systems special investigation group overview

The Systems Special Investigation Group (SIG) has undertaken investigations in the four major engineering disciplines represented in the Long Duration Exposure Facility (LDEF) hardware: electrical, mechanical, thermal, and optical systems. Testing was planned for the highest possible level of assembly, and top level system tests for nearly all systems were performed at this time. To date, testing was performed on a mix of LDEF and individual experimenter systems. No electrical or mechanical system level failures attributed to the spaceflight environment have yet been detected. Some low cost electrical components were used successfully, although relays were a continuing problem. Mechanical galling was observed unexpectedly, but no evidence of cold welding was identified yet. A working index of observed systems anomalies was created and will be used to support the tracking and resolution of these effects. The LDEF hardware currently available to the Systems SIG includes most of the LDEF systems hardware, and some significant experimenter hardware as well. A series of work packages was developed for each of several subsystem types where further testing is of critical interest. The System SIG is distributing a regular newsletter to the greater LDEF community in order to maintain coherence in an investigation which is widely scattered both in subject matter and in geography. Circulation of this informal document has quadrupled in its first year.

Mason, James B.↗

Characteristics of oxygen

Oxygen reactivity and the design of special hardware to be used in oxygen service are discussed. Safety factors, passing mixing characteristics, and oxygen absorption by porous materials are considered. Special attention was given to system failure prevention and resulting hazards, costs, and time loss.

Source record↗

Real-time computer simulation/emulation for verification of multi-fault-tolerant control of Centaur-in-Shuttle

NASA has contracted with General Dynamics to design and develop an advanced Centaur liquid upper stage for support of the Galileo and Solar Polar interplanetary missions in 1985-86. The control of the Centaur while it resides in the Shuttle cargo bay must meet the STS safety requirements to be dual failure tolerant in all mission critical functions. The demonstration of the integrity of this control system in the event of multiple component failures and worst-case time-phase asynchroniety among the system's computers is performed by a real-time computer simulation. The simulation emulates the control hardware, subsystem interfaces, and imbedded software processes, wire-by-wire, to provide accessibility for fault insertion. Observability is provided via graphics and diagnostic software. Verification is the product of Monte Carlo simulation analysis.

Szatkowski, G. P.↗

Traveling-wave maser closed-cycle refrigerator data acquisition and display system

A data acquisition and display system that automatically monitors the performance of the 4.5-K closed-cycle refrigerators used to cryogenically cool traveling-wave masers is described. The system displays and stores operating parameters for the purpose of providing status information, failure prediction, and analysis. A prototype of this system will be installed at Deep Space Network 12 in the near future. The advantages of using commercial data acquisition hardware with installed operating systems and BASIC programs for this application are discussed.

Fowler, L.↗

Telescope protection algorithm for the Space Infrared Telescope Facility

This paper presents a proposed on-board Telescope Protection Algorithm (TPA) for the Space Infrared Telescope Facility (SIRTF). This TPA consists of hardware and software capable of performing both fail-operational and fail-safe modes of operation. In the fail-operational mode, each ephemeris load and slew/dwell command sequence is checked on-board before use. The slew command monitor detects unallowable slew/dwell commands and transfers control to an algorithm which slews to and maintains a safe telescope orientation while preserving precise attitude determination and control. This fail-operational mode is also given the authority to autonomously restart the slew/dwell sequence at a point beyond the faulty command. The fail-safe system consists of software and hardware which detects impending earth, moon, or sun avoidance zone violations and activates a backup hardware safe hold mode. The subject TPA and relevant sensor complement were designed for the SIRTF mission; however, this system can easily be used as a basis for failure detection and correction in a wide range of other missions.

Class, B. F.↗

Test Results for the Automated Rendezvous and Capture System

The Automated Rendezvous and Capture (AR&C) system was designed and tested at NASA's Marshall Space Flight Center (MSFC) to demonstrate technologies and mission strategies for automated rendezvous and docking of spacecraft in Earth orbit, The system incorporates some of the latest innovations in Global Positioning, System space navigation, laser sensor technologies and automated mission sequencing algorithms. The system's initial design and integration was completed in 1998 and has undergone testing at MSFC. This paper describes the major components of the AR&C system and presents results from the official system tests performed in MSFC's Flight Robotics Laboratory with digital simulations and hardware in the loop tests. The results show that the AR&C system can safely and reliably perform automated rendezvous and docking missions in the absence of system failures with 100 percent success. When system failures are included, the system uses its automated collision avoidance maneuver logic to recover in a safe manner. The primary objective of the AR&C project is to prove that by designing a safe and robust automated system, mission operations cost can be reduced by decreasing the personnel required for mission design, preflight planning and training required for crewed rendezvous and docking missions.

Cruzen, Craig↗

Structural Analysis Made 'NESSUSary'

Everywhere you look, chances are something that was designed and tested by a computer will be in plain view. Computers are now utilized to design and test just about everything imaginable, from automobiles and airplanes to bridges and boats, and elevators and escalators to streets and skyscrapers. Computer-design engineering first emerged in the 1970s, in the automobile and aerospace industries. Since computers were in their infancy, however, architects and engineers during the time were limited to producing only designs similar to hand-drafted drawings. (At the end of 1970s, a typical computer-aided design system was a 16-bit minicomputer with a price tag of $125,000.) Eventually, computers became more affordable and related software became more sophisticated, offering designers the "bells and whistles" to go beyond the limits of basic drafting and rendering, and venture into more skillful applications. One of the major advancements was the ability to test the objects being designed for the probability of failure. This advancement was especially important for the aerospace industry, where complicated and expensive structures are designed. The ability to perform reliability and risk assessment without using extensive hardware testing is critical to design and certification. In 1984, NASA initiated the Probabilistic Structural Analysis Methods (PSAM) project at Glenn Research Center to develop analysis methods and computer programs for the probabilistic structural analysis of select engine components for current Space Shuttle and future space propulsion systems. NASA envisioned that these methods and computational tools would play a critical role in establishing increased system performance and durability, and assist in structural system qualification and certification. Not only was the PSAM project beneficial to aerospace, it paved the way for a commercial risk- probability tool that is evaluating risks in diverse, down- to-Earth application

Source record↗

Risk as a Resource - A New Paradigm

NASA must change dramatically because of the current United States federal budget climate. The American people and their elected officials have mandated a smaller, more efficient and effective government. For the past decade, NASA's budget had grown at or slightly above the rate of inflation. In that era, taking all steps to avoid the risk of failure was the rule. Spacecraft development was characterized by extensive analyses, numerous reviews, and multiple conservative tests. This methodology was consistent with the long available schedules for developing hardware and software for very large, billion dollar spacecraft. Those days are over. The time when every identifiable step was taken to avoid risk is being replaced by a new paradigm which manages risk in much the same way as other resources (schedule, performance, or dollars) are managed. While success is paramount to survival, it can no longer be bought with a large growing NASA budget.

Risk Resource↗

Failure Analysis of Fractured Poppet from Space Shuttle Orbiter Flow Control Valve

This slide presentation reviews the failure analysis of a fractured poppet from a flow control valve (FCV) used on the space shuttle. This presentation has focused on the laboratory analysis of the failed hardware. The use of Scanning electron fractography during the investigation led to the conclusion that the poppet failed due to fatigue cracking that, most likely, occurred under changing loading conditions. The initial investigation led to a more thorough test of poppets that had been retired, this testing led to the conclusion that the thumbnail cracks in the flight hardware had existed for the life of the shuttle program. This led to a program to develop an eddy current technique that was capable of detecting small very tight cracks.

Russell, Richard↗