Acknowledgment

We would like to thank Professor Gatsonis for his guidance, patience, and encouragement during the course of last three terms. We would also like to thank Richard Nanson, a graduate assistant at the Computational Gas and Plasma Dynamics Lab, for his technical advice and assistance.

Abstract

Small cold-gas thrusters are used for satellite orbital maneuvering, attitude control and station keeping. A performance optimization study is performed using small cold-gas conical, trumpet, and bell-shaped thrusters with an exit radius of 5.10 mm and area ratio of 104.04 . The flow is simulated using an axisymmetric Navier-Stokes code, and the thrust, specific impulse and discharge coefficient are evaluated for stagnation pressures between 2-7 kPa and stagnation temperature of 300K. The code is validated by comparisons with one-dimensional analytical results and previous numerical work. The importance of rarefaction efftects in the thruster are also discussed. For all three thrusters considered, the numerical values of thrust, specific impulse and discharge coefficient are lower than the analytical values due to geometrical and boundary layer effects not included in the analytical model. The bell and conical thrusters are shown to achieve the higher thrust, specific impulse and discharge coefficient for the entire range of stagnation pressures considered. It is also found that in all cases considered the flow rarefies at the exit and as such a combination of continuum and rarefied numerical techniques may be necessary in order to obtain accurate results.