Gas dynamics of laser exhaust external to spacecraft
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 DirectSimulationMonteCarlo 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).
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 November 1985
 Bibcode:
 1985STIN...8631011A
 Keywords:

 Axisymmetric Flow;
 Exhaust Gases;
 Flow Distribution;
 Gas Dynamics;
 Gas Lasers;
 Jet Flow;
 Method Of Characteristics;
 Monte Carlo Method;
 Plumes;
 Spacecraft Environments;
 Continuum Mechanics;
 Mean Free Path;
 Space Environment Simulation;
 Fluid Mechanics and Heat Transfer