Analyzing Damping Vibration Methods of Large-Size Space Vehicles in the Earth's Magnetic Field

Abstract

It is known that most of today's space vehicles comprise large antennas, which are bracket-attached to the vehicle body. Dimensions of reflector antennas may be of 30 ... 50 m. The weight of such constructions can reach approximately 200 kg. Since the antenna dimensions are significantly larger than the size of the vehicle body and the points to attach the brackets to the space vehicles have a low stiffness, conventional dampers may be inefficient. The paper proposes to consider the damping antenna in terms of its interaction with the Earth's magnetic field. A simple dynamic model of the space vehicle equipped with a large-size structure is built. The space vehicle is a parallelepiped to which the antenna is attached through a beam. To solve the model problems, was used a simplified model of Earth's magnetic field: uniform, with intensity lines parallel to each other and perpendicular to the plane of the antenna. The paper considers two layouts of coils with respect to the antenna, namely: a vertical one in which an axis of magnetic dipole is perpendicular to the antenna plane, and a horizontal layout in which an axis of magnetic dipole lies in the antenna plane. It also explores two ways for magnetic damping of oscillations: through the controlled current that is supplied from the power supply system of the space vehicle, and by the self-induction current in the coil. Thus, four objectives were formulated. In each task was formulated an oscillation equation. Then a ratio of oscillation amplitudes and their decay time were estimated. It was found that each task requires the certain parameters either of the antenna itself, its dimensions and moment of inertia, or of the coil and, respectively, the current, which is supplied from the space vehicle. In each task for these parameters were found the ranges, which allow us to tell of efficient damping vibrations. The conclusion can be drawn based on the analysis of tasks that a specialized control system can be used for damping vibrations of large-size antennas. In this case the actuating elements can be coils. It is shown that efficient damping is possible when the certain system parameters are taken into consideration.