Gas dynamics of laser exhaust external to spacecraft
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Authors
Abramovich, Shaul
Subjects
Spacecraft Laser Exhaust
Method of Characteristics
Direct Simulation - Monte Carlo
Molecular Simulation - Monte Carlo
Ring Jet
Underexpanded Flow
Hard Sphere Molecules
Method of Characteristics
Direct Simulation - Monte Carlo
Molecular Simulation - Monte Carlo
Ring Jet
Underexpanded Flow
Hard Sphere Molecules
Advisors
Date of Issue
1985-11
Date
1985-11
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
Some procedures have been developed to analyze the flowfield of highly underexpanded axisymmetric ring jets operated at high altitudes. The Method of Characteristics (MOS) was used to compute the Prandtl Meyer expansion fan and flow parameters in that region. The MOC may also be used to obtain some indications about the repetitive expansion compression behavior of the jet as well as the divergent shape of the compression part downstream, when the ambient pressure goes below certain limits. The continuum methods may be used as far as the limit where translational equilibrium ceases to exist. The breakdown of the continuum theory may be evaluated using the experimental breakdown parameter. Beyond this limit, the molecular Direct-Simulation-Monte-Carlo method (DSMC) is applied. The axisymmetric Monte Carlo Simulation begins outside the nozzle, where the breakdown parameter has a value of approximately 0.05. The actual shape of this breakdown limit is a closed lobe surface which starts at the nozzle lips, approximately follows a specific Mach wave in the Prandtl Meyer fan and closes back to the axis far downstream. Because our interest is limited to the close vicinity of the corners, there the shape of this limit may be approximated to a straight line (for an axisymmetric flow making cone). The program runs as far as the collision frequency is still high and the mean free path is low compared with the size of the cells. Beyond this limit the flow may be regarded as collisionless, and the flux towards the solid wall may be computed directly
Type
Technical Report
Description
Series/Report No
Department
Identifiers
NPS Report Number
NPS-67-84-006CR
Sponsors
Defense Advanced Research Projects Agency
Funder
N62271-3140-5157
Format
Citation
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.