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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Projected network performance for next-generation xenon monitoring systems

Next-generation radioxenon monitoring systems are reaching maturity and are expected to improve certain aspects of performance in verifying the absence of nuclear tests. To predict the improvement in detecting and locating nuclear releases, thousands of releases all over the globe were simulated and the global detection probability was calculated. This was done for the International Monitoring System network of noble gas samplers as it currently exists (25 certified stations), and how it would be for potential future network sizes of 39 and 79 stations. The probability of detection was calculated for releases ranging from 10 10 Bq to 10 16 Bq of 133 Xe and presented as coverage maps and global integrals for both current and next-generation monitoring systems. Similarly, the number of detecting stations and the number of detecting samples were tabulated to elucidate the possibilities for enhanced location capability. Improvements in global detection coverage are maximized at different release sizes in a way that depends on the station density. For example, for releases of 3×10 14 Bq and 39 stations, the detection probability would rise from 60% to 70% with next-generation systems, while for releases of 10 13 Bq and 79 stations, it would rise from 37% to 52%. Achieving an average of two detecting stations requires a 1015 Bq release for a 39-station network and a 10 14 Bq release for a 79-station network. The largest impact of using next-generation systems may be the confidence, failure tolerance, and location capability that arise from obtaining multiple samples associated with a single release event.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1974

Adaptive voting computer system

A computer system is reported that uses adaptive voting to tolerate failures and operates in a fail-operational, fail-safe manner. Each of four computers is individually connected to one of four external input/output (I/O) busses which interface with external subsystems. Each computer is connected to receive input data and commands from the other three computers and to furnish output data commands to the other three computers. An adaptive control apparatus including a voter-comparator-switch (VCS) is provided for each computer to receive signals from each of the computers and permits adaptive voting among the computers to permit the fail-operational, fail-safe operation.

Koczela, L. J.↗
NASA NTRS1975

Essential uncontrollability of discrete linear, time-invariant, dynamical systems

The concept of a 'best approximating m-dimensional subspace' for a given set of vectors in n-dimensional whole space is introduced. Such a subspace is easily described in terms of the eigenvectors of an associated Gram matrix. This technique is used to approximate an achievable set for a discrete linear time-invariant dynamical system. This approximation characterizes the part of the state space that may be reached using modest levels of control. If the achievable set can be closely approximated by a proper subspace of the whole space then the system is 'essentially uncontrollable'. The notion finds application in studies of failure-tolerant systems, and in decoupling.

Cliff, E. M.↗
NASA NTRS1984

Ultralight reactive metal foams produced as structural shapes in space: System design

This autonomous experiment for foaming metals in space involved: (1) payload support structure; (2) furnace and foaming apparatus; (3) electronic controls; (4) battery power; and (5) metallurgy. Emphasis was laid on a modular design which was easily modifiable and which offered maximum durability, safety, and failure tolerance.

Cocks, F. H.↗
NASA NTRS1984

Progress towards large wind tunnel magnetic suspension and balance systems

Recent developments and current research efforts leading towards realization of a large scale production wind tunnel Magnetic Suspension and Balance facility are reviewed. Progress has been made in the areas of model roll control, high angle-of-attack testing, digital system control, high magnetic moment superconducting solenoid model cores, and system failure tolerance. Formal design studies of large scale facilities have commenced and are continuing.

Britcher, C. P.↗
NASA NTRS1985

Development of the space shuttle body flap actuation subsystem

Development of the Body Flap Actuation Subsystem for Space Shuttles included alterations from the original design to mechanical stops, planet gears, control valves, and solenoid valves. The mechanical stops were redesigned to absorb stall load and rotating inertia of the hydraulic motors instead of only stall load. The institution of a quill shaft (torsion spring) was a successful solution. The planet gears in the geared rotary actuators developed cracks during testing. This failure was alleviated via modification to the gears. A motor pressurization - brake release timing technique was developed thru analysis and testing. This resulted in a control valve configuration which would not permit freewheeling of the body flap surface. Finally, several solenoid valve configurations were tested to obtain the desired performance. Conceptual redesigns and modifications were weighted against each other to optimize a solution. Tradeoffs were usually made between life, performance, failure tolerance, and reliability versus weight, envelope, and maintainability.

Boggs, C. R.↗
NASA NTRS1988

The magnetic field investigation on Cluster

The magnetic field investigation of the Cluster four-spacecraft mission is designed to provide intercalibrated measurements of the B magnetic field vector. The instrumentation and data processing of the mission are discussed. The instrumentation is identical on the four spacecraft. It consists of two triaxial fluxgate sensors and of a failure tolerant data processing unit. The combined analysis of the four spacecraft data will yield such parameters as the current density vector, wave vectors, and the geometry and structure of discontinuities.

Balogh, A.↗
NASA NTRS1989

Space Station Freedom integrated fault model

A demonstration of an integrated fault propagation model for Space Station Freedom is described. The demonstration uses a HyperCard graphical interface to show how failures can propagate from one component to another, both within a system and between systems. It also shows how hardware failures can impact certain defined functions like reboost, atmosphere maintenance or collision avoidance. The demonstration enables the user to view block diagrams for the various space station systems using an overview screen, and interactively choose a component and see what single or dual failure combinations can cause it to fail. It also allows the user to directly view the fault model, which is a collection of drawing and text listings accessible from a guide screen. Fault modeling provides a useful technique for analyzing individual systems and also interactions between systems in the presence of multiple failures so that a complete picture of failure tolerance and component criticality can be achieved.

Becker, Fred J.↗
NASA NTRS1990

Investigation of air transportation technology at Princeton University, 1988-1989

The Air Transportation Technology Program at Princeton University, a program emphasizing graduate and undergraduate student research, proceeded along several avenues during the past year. A study of optimal trajectories for penetration of microbursts when encounter is unavoidable was conducted. The emphasis of current wind shear research is on developing an expert system for wind shear avoidance. A knowledge-based reconfigurable flight control system that is implemented with the Pascal programming language using parallel microprocessors was developed. This expert system could be considered a prototype for a failure-tolerant control system that can be constructed using existing hardware. Development of a real-time cockpit simulator continued during the year. The simulator provides a single-person crew station with both conventional and advanced control devices; it currently is programmed to simulate the Navion single-engine general aviation airplane. Alternatives for the air traffic control system giving particular attention to the institutional structure of the FAA are analyzed. A simple numerical procedure for estimating the stochastic robustness of control systems is being investigated. The revitalization of the general aviation industry is also discussed.

Stengel, Robert F.↗
NASA NTRS1990

A robot end effector exchange mechanism for space applications

Efficient robot operation requires the use of specialized end effectors or tools for tasks. In spacecraft applications, the microgravity environment precludes the use of gravitational forces to retain the tools in holding fixture. As a result of this, a retention mechanism which forms a part of the tool storage container is required. A unique approach to this problem has resulted in the development of an end effector exchange mechanism that meets the requirements for spaceflight applications while avoiding the complexity usually involved. This mechanism uses multiple latching cams both on the manipulator and in the tool storage container, combined with a system of catch rings to provide retention in both locations and the required failure tolerance. Because of the cam configuration the mechanism operates passively, requiring no electrical commands except those needed to move the manipulator into position. Similarly, it inherently provides interlocks to prevent the release of one cam before its opposite number is engaged.

Gorin, Barney F.↗
NASA NTRS1991

Joint University Program for Air Transportation Research, 1990-1991

The goals of this program are consistent with the interests of both NASA and the FAA in furthering the safety and efficiency of the National Airspace System. Research carried out at the Massachusetts Institute of Technology (MIT), Ohio University, and Princeton University are covered. Topics studied include passive infrared ice detection for helicopters, the cockpit display of hazardous windshear information, fault detection and isolation for multisensor navigation systems, neural networks for aircraft system identification, and intelligent failure tolerant control.

Morrell, Frederick R.↗
NASA NTRS1991

Investigation of air transportation technology at Princeton University, 1990-1991

The Air Transportation Technology Program at Princeton University is a program that emphasizes graduate and undergraduate student research. The program proceeded along six avenues during the past year: microburst hazards to aircraft, intelligent failure tolerant control, computer-aided heuristics for piloted flight, stochastic robustness of flight control systems, neural networks for flight control, and computer-aided control system design.

Stengel, Robert F.↗
NASA NTRS1991

Space transfer vehicle concepts and requirements. Volume 1: Executive summary

The objectives of the Space Transfer Vehicle (STV) Concepts and Requirements studies were to provide sensitivity data on usage, economics, and technology associated with new space transportation systems. The study was structured to utilize data on the emerging launch vehicles, the latest mission scenarios, and Space Exploration Initiative (SEI) payload manifesting and schedules, to define a flexible, high performance, cost effective, evolutionary space transportation system for NASA. Initial activities were to support the MSFC effort in the preparation of inputs to the 90 Day Report to the National Space Council (NSC). With the results of this study establishing a point-of-departure for continuing the STV studies in 1990, additional options and mission architectures were defined. The continuing studies will update and expand the parametrics, assess new cargo and manned ETO vehicles, determine impacts on the redefined Phase 0 Space Station Freedom, and to develop a design that encompasses adequate configuration flexibility to ensure compliance with on-going NASA study recommendations with major system disconnects. In terms of general requirements, the objectives of the STV system and its mission profiles will address crew safety and mission success through a failure-tolerant and forgiving design approach. These objectives were addressed through the following: engine-out capability for all mission phases; built-in-test for vehicle health monitoring to allow testing of all critical functions such as, verification of lunar landing and ascent engines before initiating the landing sequence; critical subsystems will have multiple strings for redundancy plus adequate supplies of onboard spares for removal and replacement of failed items; crew radiation protection; and trajectories that optimize lunar and Mars performance and flyby abort capabilities.

Source record↗
NASA NTRS1998

Microgravity Science in Space Flight Gloveboxes

Microgravity science studies the influences of gravity on phenomena in fluids, materials processes, combustion, and human cell growth in the low acceleration environment of space flight. During the last decade, the accomplishment of the flight research in the field has evolved into an effective cooperation between the flight crew in the Shuttle and the ground-based investigator using real-time communication via voice and video links. This team structure has led to interactive operations in which the crew performs the experimentation while guided, as necessary, by the science investigator who formulated the investigation and who will subsequently interpret and analyze the data. One of the primary challenges to implementing this interactive research has been the necessity of structuring a means of handling fluids, gases, and hazardous materials in a manned laboratory that exhibits the novelty of weightlessness. Developing clever means of designing experiments in closed vessels is part of the solution- but the space flight requirement for one and two failure-tolerant containment systems leads to serious complications in the physical handling of sample materials. In response to the conflict between the clear advantage of human operation and judgment, versus the necessity to isolate the experiment from the crewmember and the spacecraft environment, the Microgravity Research Program has initiated a series of Gloveboxes in the various manned experiment carriers. These units provide a sealed containment vessel whose interior is under a negative pressure with respect to the ambient environment but is accessible to a crewmember through the glove ports.

Baugher, Charles↗
NASA NTRS2004

Risk Assessment and Control through Countermeasure System Iplementation for Long-term Crew Exposure to Microgravity

Experience with the International Space Station (ISS) program demonstrates the degree to which engineering design and operational solutions must protect crewmembers from health risks due to long-term exposure to the microgravity environment. Risks to safety and health due to degradation in the microgravity environment include crew inability to complete emergency or nominal activities, increased risk of injury, and inability to complete safe return to the ground due to reduced strength or embrittled bones. These risks without controls slowly increase in probability for the length of the mission and become more significant for increasing mission durations. Countermeasures to microgravity include hardware systems that place a crewmember s body under elevated stress to produce an effect similar to daily exposure to gravity. The ISS countermeasure system is predominately composed of customized exercise machines. Historical treatment of microgravity countermeasure systems as medical research experiments unintentionally reduced the foreseen importance and therefore the capability of the systems to function in a long-term operational role. Long-term hazardous effects and steadily increasing operational risks due to non-functional countermeasure equipment require a more rigorous design approach and incorporation of redundancy into seemingly non- mission-critical hardware systems. Variations in the rate of health degradation and responsiveness to countermeasures among the crew population drastically increase the challenge for design requirements development and verification of the appropriate risk control strategy. The long-term nature of the hazards and severe limits on logistical re-supply mass, volume and frequency complicates assessment of hardware availability and verification of an adequate maintenance and sparing plan. Design achievement of medically defined performance requirements by microgravity countermeasure systems and incorporation of adequate failure tolerance significantly reduces these risks. Future implementation of on-site monitoring hardware for critical health parameters such as bone mineral density would allow greater responsiveness, efficiency, and optimized design of the countermeasures system.

Gernand, Jeremy M.↗
NASA NTRS2008

Safety Critical Mechanisms

Spaceflight mechanisms have a reputation for being difficult to develop and operate successfully. This reputation is well earned. Many circumstances conspire to make this so: the environments in which the mechanisms are used are extremely severe, there is usually limited or no maintenance opportunity available during operation due to this environment, the environments are difficult to replicate accurately on the ground, the expense of the mechanism development makes it impractical to build and test many units for long periods of time before use, mechanisms tend to be highly specialized and not prone to interchangeability or off-the-shelf use, they can generate and store a lot of energy, and the nature of mechanisms themselves, as a combination of structures, electronics, etc. designed to accomplish specific dynamic performance, makes them very complex and subject to many unpredictable interactions of many types. In addition to their complexities, mechanism are often counted upon to provide critical vehicle functions that can result in catastrophic events should the functions not be performed. It is for this reason that mechanisms are frequently subjected to special scrutiny in safety processes. However, a failure tolerant approach, along with good design and development practices and detailed design reviews, can be developed to allow such notoriously troublesome mechanisms to be utilized confidently in safety-critical applications.

Robertson, Brandan↗
NASA NTRS2009

Laser Peening Effects on Friction Stir Welding

The laser peening process can result in considerable improvement to crack initiation, propagation, and mechanical properties in FSW which equates to longer hardware service life Processed hardware safety is improved by producing higher failure tolerant hardware, and reducing risk. Lowering hardware maintenance cost produces longer hardware service life, and lower hardware down time. Application of this proposed technology will result in substantial benefits and savings throughout the life of the treated components

Hatameleh, Omar↗