On the bound of first excursion probability
Boundary values for first excursion probability as related to reliability and safe performance of mechanical and structural systems
Shinozuka, M.↗
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On the bound of first excursion probability
Method has been developed to improve the lower bound of the first excursion probability that can apply to the problem with either constant or time-dependent barriers. The method requires knowledge of the joint density function of the random process at two arbitrary instants.
Yang, J. N.↗
Nonlinear solid propellant burning rate behavior during abrupt pressure excursions.
Solid propellant burning rate behavior during abrupt environmental pressure excursions, using transient combustion model
Marxman, G. A.↗
On the bound of first excursion probability.
Bounding technique of first excursion probability for random vibration, considering relation to reliability of mechanical and structural systems under random disturbances
Shinozuka, M.↗
Lunar excursion module RCS engine vacuum chamber contamination study
Plume deposits of reaction control system in lunar excursion model engine vacuum chamber and contamination of test beds
Arnett, G. M.↗
Space shuttle. Volume 3 - Initial vehicle spectrum and parametric excursions Final technical report
Initial vehicle spectrum and parametric excursions of reusable space shuttle systems having multimission capability - Vol. 3
Source record↗
The hypergolic reciprocating engine electrical power system and its application to the lunar excursion module
Hypergolic reciprocating engine electrical power system and application to lunar excursion module
Haines, C. D.↗
Flow excursions in a simulated gas-cooled reactor passage
Flow excursions in simulated gas-cooled reactor passages
Reshotko, E.↗
First-excursion probability in non-stationary random vibration.
The first-excursion probability of a non-stationary Gaussian process with zero mean has been studied. Within the framework of the point process approach, a variety of analytical approximations applicable to stationary random processes is extended herein to non-stationary random processes. The extension is possible owing to a recent definition of non-stationary envelope processes proposed by the author. With the aid of numerical examples, merits of each approximation are examined by comparing with the results of simulation. It is found that under non-stationary excitations with short duration, the Markov approximation is the best among all the approximations discussed in this paper.
Yang, J.-N.↗
Estimates of the effectiveness of automatic control in alleviating wake vortex induced roll excursions
Estimates of the effectiveness of a model following type control system in reducing the roll excursion due to a wake vortex encounter were obtained from single degree of freedom computations with inputs derived from the results of wind tunnel, flight, and simulation experiments. The analysis indicates that the control power commanded by the automatic system must be roughly equal to the vortex induced roll acceleration if effective limiting of the maximum bank angle is to be achieved.
Tinling, B. E.↗
Work Capability and physiological effects predictive studies. 4: In He-O2 excursions to pressures of 400- 800- 1200- and 1600 feet of sea water
Experiments which exposed men in chambers, breathing helium with oxygen, to progressive increases of pressure equivalent to 400-800-1200-1600 feet of sea water (fsw) were conducted. Rates of compression and exposure to stable high pressure. Goals included: 1) determination of the specific character and time course of onset of physiological and performance decrements during the intentionally rapid compressions, and determination of rates of adaptation on reaching stable elevated pressure; 2) investigation of accelerated methods for decompression in deep saturation excursion diving; and 3) determination of competence in practical work performed in water at pressures equivalent to the extreme diving depths of 1200 and 1600 fsw.
Lambertsen, C. J.↗
Depriming of arterial heat pipes: An investigation of CTS thermal excursions
Four thermal excursions of the Transmitter Experiment Package (TEP) were the result of the depriming of the arteries in all three heat pipes in the Variable Conductance Heat Pipe System which cooled the TEP. The determined cause of the depriming of the heat pipes was the formation of bubbles of the nitrogen/helium control gas mixture in the arteries during the thaw portion of a freeze/thaw cycle of the inactive region of the condenser section of the heat pipe. Conditions such as suction freezeout or heat pipe turn-on, which moved these bubbles into the active region of the heat pipe, contributed to the depriming mechanism. Methods for precluding, or reducing the probability of, this type of failure mechanism in future applications of arterial heat pipes are included.
Antoniuk, D.↗
Excursion set mass functions for hierarchical Gaussian fluctuations
It is pointed out that most schemes for determining the mass function of virialized objects from the statistics of the initial density perturbation field suffer from the cloud-in-cloud problem of miscounting the number of low-mass clumps, many of which would have been subsumed into larger objects. The paper proposes a solution based on the theory of the excursion sets of F(r, R sub f), the four-dimensional initial density perturbation field smoothed with a continuous hierarchy of filters of radii R sub f.
Bond, J. R.↗
Oxidation instability of SiC and Si3N4 following thermal excursions
The effect of thermal excursion and thermal cycling on the oxidation stability of chemical vapor-deposited (CVD) SiC and Si3N4 was studied at 1350 C. Thermal cycling alone produced no noticeable change in oxidation kinetics. However, TEM showed that oxide scales grown in cycles consist of alternating layers of SiO2 and Si2N2O. When the oxidation of CVD SiC or Si3N4 at 1350 C was interrupted with a 1.5-h annealing in Ar at 1500 C, the kinetics of reoxidation at 1350 C were found to be drastically increased. The SiC and Si3N4 then oxidized essentially at the same rate, which is over 50 times the preannealing rate, and comparable to the expected oxidation rate of these materials at 1500 C.
Ogbuji, Linus U. J. T.↗
Optimization of vehicle weight for Mars excursion missions
The excursion class mission to Mars is defined as a mission with one year durations coupled with a stay time of up to 30 days. The fuel budget for such a mission is investigated. The overall figure of merit in such an assessment is the vehicle weight ratio, the ratio between the wet vehicle weight to the dry vehicle weight. It is necessary to minimize the overall fuel budget for the mission in order to maximize the benefits that could be obtained by sending humans to Mars. Assumptions used in the analysis are: each mission will depart and terminate in low-earth-orbit (LEO) (500 km circular) and the maximum stay time at Mars is 30 days. The maximum mission duration is one year (355-375 days). The mass returned to LEO is 135,000 kg, the dropoff mass left at Mars is 168,000 kg. Three propulsive techniques for atmospheric interface are investigated: aerobraking, all-chemical propulsion, and nuclear thermal propulsion. By defining the fuel requirements, the space transfer vehicle's configuration is defined.
Ferebee, Melvin J., Jr.↗
Excursion-Set-Mediated Genetic Algorithm
Excursion-set-mediated genetic algorithm (ESMGA) is embodiment of method of searching for and optimizing computerized mathematical models. Incorporates powerful search and optimization techniques based on concepts analogous to natural selection and laws of genetics. In comparison with other genetic algorithms, this one achieves stronger condition for implicit parallelism. Includes three stages of operations in each cycle, analogous to biological generation.
Noever, David↗
Geolab 2010 Hardware in NASA's Pressurized Excursion Module
NASA is designing and building the Habitat Demonstration Unit - 1 in a Pressurized Excursion Module (HDU1- PEM) configuration for analog testing at NASA s annual Desert Research and Technology Studies (DRATS) near Flagstaff, Arizona in late summer 2010. The HDU1-PEM design is based on NASA Constellation program s Lunar Scenario 12.1 (nicknamed "Lunabago"). This scenario uses Lunar Electric Rovers (LER) and a PEM for long-distance lunar exploration. The 2010 HDU version 1.0 will be an unpressurized PEM that contains a GeoLab in one of the eight PEM sections. The GeoLab is designed to facilitate sample curation protocol development including such activities as preliminary examination, sample archiving, and high grading of astromaterials for return to Earth. Geolab operations will be integrated with the DRATS science traverses and operations.
Calaway, M. J.↗
GeoLab in NASA's Pressurized Excursion Module: First Results from the 2010 Field Trials
Before humans explore other planets, NASA must develop advanced techniques for collection, preservation and return of unique extraterrestrial samples. To help evaluate hardware requirements and operational concepts for future sample-return missions, we designed and built GeoLab our first generation lab for geological samples into NASA s Habitat Demonstration Unit in the Pressurized Excursion Module (HDU1-PEM). The center of GeoLab is a glovebox for the examination of samples in a shirt-sleeve environment. As part of a deployable habitat, GeoLab can participate in NASA s analog missions that simulate planetary exploration activities and support the testing of relevant technologies for collecting and handling geological samples. Over time, these tests will evaluate sample handling environments (field and lab), sampling tools and analytical instruments, and different scenarios involving both robotic and human procedures. The GeoLab design supports evolving tests and configurations. The glovebox is mounted on the habitat bulkhead, with three sample pass-though chambers that allow for direct sample transfer into the glovebox from the outside. The glovebox design and construction (low-particle shedding, minimally off-gassing materials) provides a clean environment to reduce sample contamination; in the future, we will integrate a positive pressure, enriched nitrogen atmosphere. The glovebox is equipped with configurable instrument ports. The 2010 test included a mass balance, a stereomicroscope with a HD camera for detailed imaging of samples, and a handheld XRF analyzer for preliminary geochemical characterization of samples. Network cameras provided context imagery and sample handling activities. We present early results from the initial field trial of GeoLab during the 2010 Desert Research and Technology Studies (D-RATS) planetary analog test near Flagstaff AZ. The 2010 D-RATS mission involved two rovers, the habitat with GeoLab, four crew members, and a team of scientists and flight controllers. The crewed rovers conducted geological traverses and collected samples on the planetary surface. Selected samples were transferred into GeoLab for detailed examination and initial analysis, providing critical data to the science team for evaluation and prioritization of samples.
Evans, Cynthia A.↗