摘要 :
We analyze the data of purposeful rupture experiments with LOx and LH2 tanks, the Hydrogen-Oxygen Vertical Impact (HOVI) tests that were performed to clarify the ignition mechanisms, the explosive power of cryogenic H2/Ox mixtures...
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We analyze the data of purposeful rupture experiments with LOx and LH2 tanks, the Hydrogen-Oxygen Vertical Impact (HOVI) tests that were performed to clarify the ignition mechanisms, the explosive power of cryogenic H2/Ox mixtures under different conditions, and to elucidate the puzzling source of the initial formation of flames near the intertank section during the Challenger disaster. We carry out a physics-based analysis of general explosions scenarios for cryogenic gaseous H2/Ox mixtures and determine their realizability conditions, using the well-established simplified models from the detonation and deflagration theory. We study the features of aerosol H2/Ox mixture combustion and show, in particular, that aerosols intensify the deflagration flames and can induce detonation for any ignition mechanism. We propose a cavitation-induced mechanism of self-ignition of cryogenic H2/Ox mixtures that may be realized when gaseous H2 and Ox flows are mixed with a liquid Ox turbulent stream, as occurred in all HOVI tests. We present an overview of the HOVI tests to make conclusion on the risk of strong explosions in possible liquid rocket incidents and provide a semi-quantitative interpretation of the HOVI data based on aerosol combustion. We uncover the most dangerous situations and discuss the foreseeable risks which can arise in space missions and lead to tragic outcomes. Our analysis relates to only unconfined mixtures that are likely to arise as a result of liquid propellant space vehicle incidents.
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摘要 :
A physics-based, simulation-assisted risk assessment of a crewed launch vehicle is used to evaluate the efficacy of failure detection mechanisms and response logic, known together as 'abort triggers,' with respect to crew safety i...
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A physics-based, simulation-assisted risk assessment of a crewed launch vehicle is used to evaluate the efficacy of failure detection mechanisms and response logic, known together as 'abort triggers,' with respect to crew safety in the event of a vehicle failure during ascent to low earth orbit. Loss-of-crew risk is evaluated against three configurations of abort triggers, representing progressively broader and deeper sub-system coverage. An extensive effort undertaken to select new abort triggers beyond a limited baseline set is described. Available warning time between failure detection and failure criticality is a critical factor in determining an abort trigger contribution to crew safety. While few of the newly proposed abort triggers are credited with warning time due to analysis resource constraints, upper bounds on the risk reducing potential of the new triggers based on failure scenario risk coverage is established. The importance of the baseline set of abort triggers is also established, particularly one trigger pertaining to detecting the wholesale breakup of the vehicle as a trigger of last resort, and the final abort trigger selection is presented.
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The purpose of this manual is to provide instruction on the use of the computerprogram DRIVEN. This manual details the installation procedure, provides narration for each user input and output screen, discusses the engineering bac...
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The purpose of this manual is to provide instruction on the use of the computerprogram DRIVEN. This manual details the installation procedure, provides narration for each user input and output screen, discusses the engineering background used in the analytical development of the program, presents example problems, and finally provides a detailed description of the driveability analysis. This program is a significant step forward in pile design computing capability for the engineer. Please take the time to completely readh through this manual. Only by reading through this manual can the DRIVEN software be utilized to its full potential.
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摘要 :
An Aquatic Habitat Appraisal Guide (AHAG) was developed to evaluate fish habitatin the Upper Mississippi River System (UMRS). AHAG numerically rates existing and future habitat quality according to Habitat Suitability index (HSI) ...
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An Aquatic Habitat Appraisal Guide (AHAG) was developed to evaluate fish habitatin the Upper Mississippi River System (UMRS). AHAG numerically rates existing and future habitat quality according to Habitat Suitability index (HSI) values, accounts for impacts of an engineering project, and documents fishery benefits of environmental features (e.g., creation of slack-water habitat and construction of weirs) incorporated in the project design. A software program of AHAG was developed to facilitate modifications of the default matrix of HSI values based on site-specific data and calculate final HSI scores for an array of project alternatives. The default matrix consists of HSI values for eight species of fish common in the UMRS: white bass, emerald shiner, river darter, northern pike, smallmouth buffalo, walleye, largemouth bass, and bluegill. This report provides instructions on installing and using AHAG software to evaluate fish habitat according to season and life stage of the species.
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