Inertial energy storage hardware definition study (ring rotor)
Rotor analysis, interference stresses, fabrication/assembly, failure analysis, ring tolerances, stren plots, and drawings are discussed.
Kirk, J. A.↗
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Tailoring dynamic qualification tests for interplanetary spacecraft
It is pointed out that the word 'tailoring' has become quite popular in the past few years. Thus, two recently revised environmental test documents make frequent mention of test tailoring. 'Tailoring' is defined by MIL STD 810D (Environmental Test Methods and Engineering Guidelines). The word refers to 'the process of choosing or altering test procedures, conditions, values, tolerances, measures of failure, etc., to simulate or exaggerate the effects of one or more forcing functions to which an item will be subjected during its life cycle...'. This paper is concerned with requirement level test tailoring. Attention is given to examples of dynamic qualification test tailoring for an interplanetary spacecraft program. These examples are to provide ideas for test tailoring which can be applied to other space flight programs.
Kern, D. L.↗
Reconfiguration algorithms for tree architectures using sub-tree oriented fault tolerance
An approach to reconfiguration in tree architectures has been developed in which redundant processors are allocated at the leaves. The scheme is called sub-tree oriented fault tolerances (SOFT) and is capable of tolerating both link failures as well as multiple processor failures. In this paper, the SOFT scheme is examined from the perspective of reconfigurability. Specific algorithms are presented for reconfiguration.
Lowrie, M. B.↗
Fault Detection and Isolation for Hydraulic Control
Pressure sensors and isolation valves act to shut down defective servochannel. Redundant hydraulic system indirectly senses failure in any of its electrical control channels and mechanically isolates hydraulic channel controlled by faulty electrical channel so flat it cannot participate in operating system. With failure-detection and isolation technique, system can sustains two failed channels and still functions at full performance levels. Scheme useful on aircraft or other systems with hydraulic servovalves where failure cannot be tolerated.
Source record↗
Toggle release
The invention relates to a pyrotechnic actuated release mechanism which is mechanically two fault tolerant for effecting release. It is particularly well suited for releasably connecting structures to be used in the space environment or in other aerospace applications. The device comprises a fastener plate and fastener body, each attachable to either one of a pair of structures to be joined. The fastener plate and the body are fastenable by a toggle supported at one end on the fastener plate and mounted for universal pivotal movement thereon. At its other end, which is received in a central opening in the fastener body and adapted for limited pivotal movement therein, the toggle is restrained by three retractable latching pins. Each pin is individually retractable by combustion of a pyrotechnic charge. While retraction of all three pins releases the toggle, the fastener is mechanically two fault tolerant since the failure of any single or pair of the latch pins to retract results in an asymmetrical loading on the toggle and its pivotal movement to effect a release. An annular bolt is mounted on the fastener plate as a support for the socket mounting of the toggle whereby its selective axial movement provides a means for pre-loading the toggle.
Graves, Thomas Joseph↗
Hardware and software fault tolerance - A unified architectural approach
The loss of hardware fault tolerance which often arises when design diversity is used to improve the fault tolerance of computer software is considered analytically, and a unified design approach is proposed to avoid the problem. The fundamental theory of fault-tolerant (FT) architectures is reviewed; the current status of design-diversity software development is surveyed; and the FT-processor/attached-processor (FTP/AP) architecture developed by Lala et al. (1986) is described in detail and illustrated with diagrams. FTP/AP is shown to permit efficient implementation of N-version FT software while still tolerating random hardware failures with very high coverage; the reliability is found to be significantly higher than that of conventional majority-vote N-version software.
Lala, Jaynarayan H.↗
Double swivel toggle release
A pyrotechnic actuated structural release device is disclosed which is mechanically two fault tolerant for release. The device comprises a fastener plate and fastener body each attachable to one of a pair of structures to be joined. The fastener plate and the fastener body are fastened by a dual swivel toggle member. The toggle member is supported at one end on the fastener plate and mounted for universal pivotal movement thereon. Its other end is received in a central opening in the fastener body, and has a universally mounted retainer ring member. The toggle member is restrained by three retractable latching pins symmetrically disposed in equiangular spacing about the axis of the toggle member and positionable in latching engagement with the retainer ring member on the toggle member. Each pin is retractable by a pyrotechnic charge, the expanding gases of which are applied to a pressure receiving face on the latch pins to effect retraction from the ring member. While retraction of all three pins releases the ring member, the fastener is mechanically two fault tolerant since the failure of any single one or pair of the latch pins to retract results in an asymmetrical loading on the ring member and its dual pivotal movement ensures a release.
King, Guy L.↗
Test and evaluation of the generalized gate logic system simulator
The results of the initial testing of the Generalized Gate Level Logic Simulator (GGLOSS) are discussed. The simulator is a special purpose fault simulator designed to assist in the analysis of the effects of random hardware failures on fault tolerant digital computer systems. The testing of the simulator covers two main areas. First, the simulation results are compared with data obtained by monitoring the behavior of hardware. The circuit used for these comparisons is an incomplete microprocessor design based upon the MIL-STD-1750A Instruction Set Architecture. In the second area of testing, current simulation results are compared with experimental data obtained using precursors of the current tool. In each case, a portion of the earlier experiment is confirmed. The new results are then viewed from a different perspective in order to evaluate the usefulness of this simulation strategy.
Miner, Paul S.↗
Integrating security in a group oriented distributed system
A distributed security architecture is proposed for incorporation into group oriented distributed systems, and in particular, into the Isis distributed programming toolkit. The primary goal of the architecture is to make common group oriented abstractions robust in hostile settings, in order to facilitate the construction of high performance distributed applications that can tolerate both component failures and malicious attacks. These abstractions include process groups and causal group multicast. Moreover, a delegation and access control scheme is proposed for use in group oriented systems. The focus is the security architecture; particular cryptosystems and key exchange protocols are not emphasized.
Reiter, Michael↗
Sliding-Mode Control Applied for Robust Control of a Highly Unstable Aircraft
An investigation into the application of an observer based sliding mode controller for robust control of a highly unstable aircraft and methods of compensating for actuator dynamics is performed. After a brief overview of some reconfigurable controllers, sliding mode control (SMC) is selected because of its invariance properties and lack of need for parameter identification. SMC is reviewed and issues with parasitic dynamics, which cause system instability, are addressed. Utilizing sliding manifold boundary layers, the nonlinear control is converted to a linear control and sliding manifold design is performed in the frequency domain. An additional feedback form of model reference hedging is employed which is similar to a prefilter and has large benefits to system performance. The effects of inclusion of actuator dynamics into the designed plant is heavily investigated. Multiple Simulink models of the full longitudinal dynamics and wing deflection modes of the forward swept aero elastic vehicle (FSAV) are constructed. Additionally a linear state space models to analyze effects from various system parameters. The FSAV has a pole at +7 rad/sec and is non-minimum phase. The use of 'model actuators' in the feedback path, and varying there design, is heavily investigated for the resulting effects on plant robustness and tolerance to actuator failure. The use of redundant actuators is also explored and improved robustness is shown. All models are simulated with severe failure and excellent tracking, and task dependent handling qualities, and low pilot induced oscillation tendency is shown.
Vetter, Travis Kenneth↗
Toggle release
A pyrotechnic actuated structural release device 10 which is mechanically two fault tolerant for release. The device 10 comprises a fastener plate 11 and fastener body 12, each attachable to a different one of a pair of structures to be joined. The fastener plate 11 and body 12 are fastenable by a toggle 13 supported at one end on the fastener plate and mounted for universal pivotal movement thereon. At its other end which is received in a central opening in the fastener body 12 and adapted for limited pivotal movement therein the toggle 13 is restrained by three retractable latching pins 61 symmetrically disposed in equiangular spacing about the axis of the toggle 13 and positionable in latching engagement with an end fitting on the toggle. Each pin 61 is individually retractable by combustion of a pyrotechnic charge 77, the expanding gases of which are applied to a pressure receiving face 67 on the latch pin 61 to effect its retraction from the toggle. While retraction of all three pins 62 releases the toggle, the fastener is mechanically two fault tolerant since the failure of any single one or pair of the latch pins to retract results in an asymmetrical loading on the toggle and its pivotal movement to effect a release. An annular bolt 18 is mounted on the fastener plate 11 as a support for the socket mounting 30, 37 of the toggle whereby its selective axial movement provides a means for preloading the toggle.
Graves, Thomas J.↗
Power Goals for NASA's Exploration Program
Exciting Future Programs ahead for NASA. Power is needed for all Exploration vehicles and for the missions. For long term missions as in Lunar and Mars programs, safe, high energy/ultra high energy batteries are required. Safety is top priority for human-rated missions. Two-fault tolerance to catastrophic failures is required for human-rated safety To meet power safety goals -inherent cell safety may be required; it can lessen complexity of external protective electronics and prevents dependency on hardware that may also have limitations. Inherent cell safety will eliminate the need to carry out screening of all cells (X-rays, vibration, etc.)
Jeevarajan, Judith A.↗
Design, Optimization, and Evaluation of Integrally-Stiffened Al-2139 Panel with Curved Stiffeners
A curvilinear stiffened panel was designed, manufactured, and tested in the Combined Load Test Fixture at NASA Langley Research Center. The panel is representative of a large wing engine pylon rib and was optimized for minimum mass subjected to three combined load cases. The optimization included constraints on web buckling, material yielding, crippling or local stiffener failure, and damage tolerance using a new analysis tool named EBF3PanelOpt. Testing was performed for the critical combined compression-shear loading configuration. The panel was loaded beyond initial buckling, and strains and out-of-plane displacements were extracted from a total of 20 strain gages and 6 linear variable displacement transducers. The VIC-3D system was utilized to obtain full field displacements/strains in the stiffened side of the panel. The experimental data were compared with the strains and out-of-plane deflections from a high fidelity nonlinear finite element analysis. The experimental data were also compared with linear elastic finite element results of the panel/test-fixture assembly. Overall, the panel buckled very near to the predicted load in the web regions.
Havens, David↗
Development of the Orion Crew-Service Module Umbilical Retention and Release Mechanism
The Orion CSM umbilical retention and release mechanism supports and protects all of the cross-module commodities between the spacecrafts crew and service modules. These commodities include explosive transfer lines, wiring for power and data, and flexible hoses for ground purge and life support systems. The mechanism employs a single separation interface which is retained with pyrotechnically actuated separation bolts and supports roughly two dozen electrical and fluid connectors. When module separation is commanded, either for nominal on-orbit CONOPS or in the event of an abort, the mechanism must release the separation interface and sever all commodity connections within milliseconds of command receipt. There are a number of unique and novel aspects of the design solution developed by the Orion mechanisms team. The design is highly modular and can easily be adapted to other vehiclesmodules and alternate commodity sets. It will be flight tested during Orions Exploration Flight Test 1 (EFT-1) in 2014, and the Orion team anticipates reuse of the design for all future missions. The design packages fluid, electrical, and ordnance disconnects in a single separation interface. It supports abort separations even in cases where aerodynamic loading prevents the deployment of the umbilical arm. Unlike the Apollo CSM umbilical which was a destructive separation device, the Orion design is resettable and flight units can be tested for separation performance prior to flight.Initial development testing of the mechanisms separation interface resulted in binding failures due to connector misalignments. The separation interface was redesigned with a robust linear guide system, and the connector separation and boom deployment were separated into two discretely sequenced events. These changes addressed the root cause of the binding failure by providing better control of connector alignment. The new design was tuned and validated analytically via Monte Carlo simulation. The analytical validation was followed by a repeat of the initial test suite plus test cases at thermal extremes and test cases with imposed mechanical failures demonstrating fault tolerance. The mechanism was then exposed to the qualification vibration environment. Finally, separation testing was performed at full speed with live ordnance.All tests of the redesigned mechanism resulted in successful separation of the umbilical interface with adequate force margins and timing. The test data showed good agreement with the predictions of the Monte Carlo simulation. The simulation proved invaluable due to the number of variables affecting the separation and the uncertainty associated with each. The simulation allowed for rapid assessment of numerous trades and contingency scenarios, and can be easily reconfigured for varying commodity sets and connector layouts.
Separation↗
Service Life Extension of the ISS Propulsion System Elements
The International Space Station (ISS) is a result of international collaboration in building a sophisticated laboratory of an unprecedented scale in Low Earth Orbit. After a complex assembly sequence spanning over a decade, some of the early modules launched at the beginning of the program would reach the end of their certified lives, while the newer modules were just being commissioned into operation. To maximize the return on global investments in this one-of-a-kind orbiting platform that was initially conceived for a service life until 2016, it is essential for the cutting edge research on ISS to continue as long as the station can be sustained safely in orbit. ISS Program is assessing individual modules in detail to extend the service life of the ISS to 2024, and possibly to 2028. Without life extension, Functional Cargo Block (known by its Russian acronym as FGB) and the Service Module (SM), two of the early modules on the Russian Segment, would reach the end of their certified lives in 2013 and 2015 respectively. Both FGB and SM are critical for the propulsive function of the ISS. This paper describes the approach used for the service life extension of the FGB propulsion system. Also presented is an overview of the system description along with the process adopted for developing the life test plans based on considerations of system failure modes, fault tolerance and safety provisions. Tests and analyses performed, important findings and life estimates are summarized. Based on the life extension data, FGB propulsion system, in general, is considered ready for a service life until 2028.
Kamath, Ulhas↗
Operating Modes and Cooling Capabilities of the Flight ADR for the SXS Instrument on Astro-H
The microcalorimeter array on the Soft X-ray Spectrometer instrument on Astro-H requires cooling to 50 mK, which will be accomplished by a 3-stage adiabatic demagnetization refrigerator (ADR). The ADR is surrounded by a cryogenic system consisting of a superfluid helium tank, a 4.5 K Joule-Thomson (JT) cryocooler, and additional 2-stage Stirling cryocoolers that pre-cool the JT cooler and radiation shields within the cryostat. The unique ADR design allows the instrument to meet all of its science requirements using either the stored cryogen or the JT cryocooler as its heat sink, giving the instrument an unusual degree of tolerance for component failures or degradation in the cryogenic system. The flight detector assembly, ADR and dewar were integrated in early 2014, and have since been extensively characterized and calibrated. At present, the four instruments are being integrated with the spacecraft in preparation for an early 2016 launch. This presentation summarizes the operation and performance of the ADR in all of its operating modes.
adiabatic demagnetization refrigerator↗
Operating Modes and Cooling Capabilities of the 3-Stage ADR Developed for the Soft-X-Ray Spectrometer Instrument on Astro-H
A 3-stage adiabatic demagnetization refrigerator (ADR) is used on the Soft X-ray Spectrometer instrument on Astro-H to cool a 6x6 array of x-ray microcalorimeters to 50 mK. The ADR is supported by a cryogenic system consisting of a superfluid helium tank, a 4.5 K Joule-Thomson (JT) cryocooler, and additional 2-stage Stirling cryocoolers that pre-cool the JT cooler and cool radiation shields within the cryostat. The ADR is configured so that it can use either the liquid helium or the JT cryocooler as its heat sink, giving the instrument an unusual degree of tolerance for component failures or degradation in the cryogenic system. The flight detector assembly, ADR and dewar were integrated into the flight dewar in early 2014, and have since been extensively characterized and calibrated. This paper summarizes the operation and performance of the ADR in all of its operating modes
x-ray astronomy↗
Complex Dynamics of Air Traffic Flow
Air traffic in the United States has continued to grow at a steady pace since 1980, except for a dip immediately after the tragic events of September 11, 2001. There are different growth scenarios associated both with the magnitude and the composition of the future air traffic. The Terminal Area Forecast (TAF), prepared every year by the FAA, projects the growth of traffic in the United States. Both Boeing and Airbus publish market outlooks for air travel annually. Although predicting the future growth of traffic is difficult, there are two significant trends: heavily congested major airports continue to see an increase in traffic, and the emergence of regional jets and other smaller aircraft with fewer passengers operating directly between non-major airports. The interaction between air traffic demand and the ability of the system to provide the necessary airport and airspace resources can be modeled as a network. The size of the resulting network varies depending on the choice of its nodes. It would be useful to understand the properties of this network to guide future design and development. Many questions, such as the growth of delay with increasing traffic demand and impact of the en route weather on future air traffic, require a systematic understanding of the properties of the air traffic network. There has been a major advance in the understanding of the behavior of networks with a large number of components. Several theories have been advanced about the evolution of large biological and engineering networks by authors in diversified disciplines like physics, mathematics, biology and computer science. Several networks exhibit a scale-free property in the sense that the probabilistic distribution of their nodes as a function of connections decreases slower than an exponential. These networks are characterized by the fact that a small number of components have a disproportionate influence on the performance of the network. Scale-free networks are tolerant to random failure of components, but are vulnerable to selective attack on components. This paper examines two network representations for the baseline air traffic system. A network defined with the 40 major airports as nodes and with standard flight routes as links has a characteristic scale: all nodes have 60 or more links and no node has more than 460 links. Another network is defined with baseline aircraft routing structure exhibits an exponentially truncated scale-free behavior. Its degree ranges from 2 connections to 2900 connections, and 225 nodes have more than 250 connections. Furthermore, those high-degree nodes are homogeneously distributed in the airspace. A consequence of this scale-free behavior is that the random loss of a single node has little impact, but the loss of multiple high-degree nodes (such as occurs during major storms in busy airspace) can adversely impact the system. Two future scenarios of air traffic growth are used to predict the growth of air traffic in the United States. It is shown that a three-times growth in the overall traffic may result in a ten-times impact on the density of traffic in certain parts of the United States.
Scale-free Networks↗