Simplified model for calculation of backflow contamination from rocket exhausts in vacuum
Abstract
A computationally simple procedure for estimating the backflow from a plume expanding into a vacuum has been developed. The continuum flow is modeled as in the Simons method, with straight streamlines radiating from a point on the plume axis of symmetry, constant velocity, and density varying inversely as the square of the radius. The continuous transition from continuum to freemolecular flow is replaced by a suitably defined discontinuity surface. Particle number densities outside the discontinuity surface are calculated by assuming that a Maxwellian velocity distribution exists for particles located within small volumes adjacent to that surface. The boundary layer at the nozzle exit is accounted for and may be large compared with the freestream inviscid flow region. Calculated results are compared with existing backflow data for nozzles using CO2 as a propellant.
 Publication:

Journal of Spacecraft and Rockets
 Pub Date:
 March 1994
 DOI:
 10.2514/3.26432
 Bibcode:
 1994JSpRo..31..265J
 Keywords:

 Rocket Exhaust;
 Spacecraft Contamination;
 Vacuum;
 Carbon Dioxide;
 Continuum Flow;
 Continuum Mechanics;
 Free Molecular Flow;
 MaxwellBoltzmann Density Function;
 Transition Flow;
 Velocity Distribution;
 Spacecraft Design, Testing and Performance