Analysis and simulation of discharging residual rocket Propellants in orbit
火箭剩余推进剂排放过程的分析与模拟

To diminish the generation of space debris,the residual propellants in the storage tank of a final-stage rocket have to be discharged after the satellite-rocket separation.An analysis shows that the propellant jets under the discharge conditions,once entering the space,will break up into a number of liquid droplets.The droplets diffuse in the high vacuum,while gaseous molecules successively evaporate from the droplet surfaces.This process yields a rarefied vapor and droplet field around the final-stage rocket.This article employs the Lagrange means to track trajectories and evaporation processes of the droplets,and employs the direct simulation Monte Carlo (DSMC) method to calculate motion and collisions of the gaseous molecules.Macroscopic quantities of interest,such as the flow fields,surface pressure,shear stress and heat flux,etc.,are obtained through statistically averaging the corresponding microscopic quantities.This scheme is validated to simulate a steam plume around a water jet into vacuum,and the calculated Pitot pressure distributions in the radial direction agree with Fuchs and Legge's measured data.The scheme is then applied to three dimensional rarefied vapor and droplet plumes arising from original and new manners discharging in orbit the residual fuel 1,1-dimethyl-hydrazine of a CZ-4B final-stage rocket.The calculation shows that the original manner may lead to quite large disturbance moments beyond the rocket attitude-control range,whereas the new manner very small disturbance moments within the range.These predictions are supported by the remotely measured data of flights