AIAA JOURNAL Vol. 42, No. 8, August 2004 Direct Simulation Monte Carlo Analysis of Thruster Plumes/Satellite Base Region Interaction Jae Hyun Park ∗ and Seung Wook Baek † Korea Advanced Institute of Science and Technology, Daejon 305-701, Republic of Korea and Jeong Soo Kim ‡ Korea Aerospace Research Institute, Daejon 305-333, Republic of Korea The interaction of thruster plumes with satellite components is investigated, with emphasis on undesirable effects, such as disturbance force/torque, thermal loading, and species deposition in the Korea Multipurpose Satellite-II (KOMPSAT-II) base region. The actual configuration of the satellite is simplified by the consideration of four major components of hydrazine thrusters, the S-band antenna, and the surrounding ring. For the numerical simulation, a fully unstructured three-dimensional discrete simulation Monte Carlo (DSMC) code is developed and validated. The DSMC computation allows for examination of the detailed flowfield dynamics, as well as the wall conditions, which, otherwise, would not be possible from a simplified engineering analysis. The computations show that the present thruster arrangement used in KOMPSAT-II incurs a negligible disturbance force/torque and thermal loading compared with its nominal thrust/torque and solar heating. The simulations also indicate that the species deposition is insignificant due to the high surface temperature of the satellite body. Of the chemical species considered (H 2 ,N 2 , and NH 3 ), more H 2 molecules collide with the S-band antenna cone. This study clearly shows the usefulness of DSMC calculations for analysis of plume effects in the development phase of a satellite. Nomenclature P 0 = chamber pressure q sol = solar constant r th = radius of thrust throat r 0 = radius of thruster exit T 0 = chamber temperature x , y , z = coordinates t = time step σ T = thermal accommodation coefficient Subscript BOL = beginning of life Introduction S ATELLITE motion is usually controlled by gas exhaustion from the thrusters into near-vacuum surroundings. Then, an unde- sirable interaction between plume and spacecraft body may cause considerable adverse effects such as disturbance force/torque, ther- mal loads, and contamination of sensitive equipment and sensors. Because these effects would result in a reduction of the satellite mission lifetime, their accurate modeling and predictions are very important at the design stage of a satellite. 1,2 Received 16 April 2003; revision received 14 November 2003; accepted for publication 14 November 2003. Copyright c  2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0001-1452/04 $10.00 in correspondence with the CCC. ∗ Ph.D. Candidate, Division of Aerospace Engineering, 373-1 Kusung- dong, Yusung-ku; currently Postdoctoral Associate, Beckman Insti- tute for Advanced Science and Technology, University of Illinois at Urbana–Champaign, 405 North Mathews Avenue, Urbana, IL 61801; jaepark@uiuc.edu. Member AIAA. † Professor, Division of Aerospace Engineering, 373-1 Kusung-dong, Yusung-ku; swbaek@kaist.ac.kr. Senior Member AIAA. ‡ Principal Researcher, Satellite Research and Development Division, Yusung-ku; currently Professor, School of Mechanical and Automotive En- gineering, Sunchon National University, 315 Maegok, Sunchon, Jeonnam 540-742, Republic of Korea; jskim@suchon.ac.kr. Member AIAA. The examination of the interaction between the exhausted plume and the satellite components through ground-based experiments is quite complicated and expensive, because it requires construction and operation of high vacuum facilities to reproduce the desired op- erating conditions, such as nozzle pressure ratio and Mach/Reynolds number at the nozzle exit. As a result, a numerical analysis is preferred. Among many numerical methods, the direct simulation Monte Carlo 3 (DSMC) technique is usually adopted for this kind of problem because the flowfield around a satellite involves a broad range of flow regimes, from the near continuum in the vicinity of the nozzle exit, through the transitional regime, to free-molecular flow in the region far from the nozzle. Many researchers have investigated the fundamental character- istics of plume exhaust by comparing DSMC results with the ex- perimental data. 1,4,5 However, recent studies concentrate more on the plume interactions in realistic spacecraft missions. Lumpkin et al. 6 and Rault 7 examined plume effects in the shuttle/Mir docking, whereas Giordano et al. 8 considered the x-ray multimirror mission (XMM) satellite. Gatsonis et al. 9 investigated the induced pressure environment incurred by the firing of small cold-gas altitude con- trol thrusters onboard the suborbital environment monitor package (EMP) spacecraft. Other than the use of a DSMC method, a sim- plified plume analysis method 10 was developed earlier, based on the approximate relations 11-13 and continuum analysis. However, Markelov et al. 14 have pointed out that such an approach may cause low accuracy in the analysis of a practical complex system because it neglects some physical phenomena such as semishadow and mul- tiple reflections. Previous DSMC studies regarding satellites have usually focused on the nominal influences by the plume, rather than its undesir- able side effects. 8,9 Given these factors, in the present study, the interaction between the thruster plume and the satellite base region is investigated by the use of the DSMC method, with emphasis on the estimation of plume disturbance effects. To deal success- fully with the extremely complicated configuration of the satellite base region (in which the thrusters are installed and most exhaust gas mixture resides), a three-dimensional unstructured DSMC code is developed and validated through comparison with experimental data. It is then applied to the base region of the Korea Multipur- pose Satellite-II (KOMPSAT-II) with firing thrusters. The exhausted plume interacts with various base region components such as the 1622