2016 International Conference on Advanced Communication Control and Computing Technologies (ICACCCT) ISBN No.978-1-4673-9544-1 _______________________________________________________________________________________________________ Organized by Syed Ammal Engineering College, Ramanathapuram, Tamilnadu, India 313 Capacitance Computation of Arbitrarily Shaped Conducting Bodies by Spacecraft Surface Charging Analysis M. Dhamodaran R.Dhanasekaran Research Scholar, Director-Research, Department of Electronics and Communication Engineering, Department of Electrical and Electronics Engineering Syed Ammal Engineering College, Ramanathapuram, Syed Ammal Engineering College, Ramanathapuram, dhamodaran@syedengg.ac.in, rdhanashekar@syedengg.ac.in Abstract ─ This paper presents numerical estimation for the capacitance of an arbitrarily shaped conducting bodies based on the moment method with triangular patch modeling. The integral equation is evaluated numerically using a Gaussian quadrature method for triangles. The singular elements of the moment matrix are evaluated by using the Duffy transformation method. The Numerical data on the capacitance of conducting objects such as cuboid is presented. The computed results are compared with the previously published results. The findings of our study show that the Method of Moments is a more accurate method for the computation of free space capacitance. Index Terms— Free space capacitance, method of moments, modeling, cuboid, plasma, spacecraft charging. I. INTRODUCTION Spacecraft charging is the technique of amplifying charges on the external surfaces of the spacecraft and builds up potential on the surfaces. The potential is called absolute or surface potential [1-3]. Eventually, it leads to electrostatic discharge (ESD) on the structure and damage the spacecraft electronics. In order to calculate the surface potential, it is essential to develop the electric circuit model of the spacecraft using element resistance, inductance and capacitance [4]. The charging of orbital spacecraft bodies in the space plasma atmosphere may be harmful to the health of on-board electric subsystems [5]. It may affect telemetry, navigation, process and even the survivability of spacecraft degrading the scientific quantities. The orbiting spacecraft structure consists mainly of metallic rectangular cuboid which houses all the satellite subsystems, payload and the equipment required for its operation. The orbiting satellite generates its own power from the solar panels. Thus, the satellite structure can be represented as cuboid with a hemisphere protruding outside the spacecraft cuboid boundary representing the rear part of the fuel tank and rectangular metal plates representing the solar panels. Since the spacecraft is covered with connected conducting bodies, surface charging occurs[6]. Spacecraft charging remains to be one of the important factors of the consistency of the spacecraft electric systems in the space atmosphere. Spacecraft surfaces interrelate with the Earth’s plasma atmosphere and forms up potential on its surfaces. After exceeding the threshold voltage, it discharges uncontrolled Electrostatic Discharge on the spacecraft surfaces. The discharge results in transient structural current and radiated electromagnetic energy which modifies the electrical state of the spacecraft systems. The charging induced unwanted currents pose a serious threat to the survivability of the spacecraft in the orbit. The surface potential also affects the scientific measurements in the orbit. The motivation about the computation of the free space capacitance of the spacecraft surfaces for calculating the charging effects. As, the spacecraft surfaces are covered with conductive materials, every surface substantial has different capacitances with respect to infinity. Due to different values of the capacitance for every surface, the profile of the period dependent potential is changed for every surface. This generates the arcing actions due to variance charging among the surfaces[7]. The method is pure theoretic investigation for computing the free space capacitance and time dependent charging potential. An algorithm based on the method of moments with parametric triangular patch modeling is proposed to compute the free space capacitance of the arbitrarily shaped objects[8]. This algorithm is more general, purely numerical, and capability to model the geometrically complex spacecraft. This is amenable for the object oriented programming. Based on the proposed approach, the capacitance of the metallic cuboid is analyzed. This paper presents the Method of Moments (MoM) based analysis for the computation of capacitance matrix and charge distribution of a three dimensional spacecraft body[9]. The integral equations which are formed by relating the unknown charge density of the satellite body represented by metallic cuboid and solar panel consisting of two rectangular plates to the potential on the surface of these bodies are solved using MoM. In order to apply the MoM, the surfaces of the metallic bodies are discretized using uniform triangular subsections. The numerical data on the capacitance and charge distribution of this structure are presented. The validity of this analysis has been