Laws to Control a Rotating Space Tether System

A mathematical model allowing to effectively control a group of satellites connected to each other with tethers has been created by scientists of Samara University being part of the international research group. According to the authors, the model allows to effectively control a cluster of spacecrafts. Results were presented in Acta Astronautica.

Rotating space tether system is a cluster of two spacecrafts, being a mode of rotation as a “space slingshot,” while its center of mass is moved on the given orbit. “As a rule, it includes a large main satellite and small sub-satellite connected with a thin firm tether with a length of tens kilometers,” told specialists of Samara National Research University.

Rotating tether systems in the aerospace allow to perform tasks that are impossible, unreasonable, or uneconomic to be solved by existing space hardware. They are used, in particular, for creating simulated gravity, forming clusters of satellites, satellite deployment. Recently, considerable attention is paid to a possibility to use tether systems as a “aerospace sanitarians” for cleaning orbits from space debris.

Associate Professor of the Department of Flight Dynamics and Control Pavel Fadeenkov in collaboration with Chinese colleagues under the supervision of Professor of the Automatics Institute of the Xi’an Northwestern Polytechnical University (PRC) Wang Changqing created a mathematical model that allows building the system to control low thrust engines of spacecrafts for changing plane of rotation of the tether system for considerable angles. According to researchers, based on the Lagrangian Formalism, they obtained the equations of motion in a rotating coordinate system. “Main advantage is that the new model allowed to deduce laws to control electric engines in analytical form in order to induce the rotation of the system and compensate various disturbances. This allows to rapidly create a real space system,” noted Fadeenkov. He added that the motion of a cluster of satellite with the weights of 1,600 and 60 kilograms with the tether with the length of 3 kilometers, located at the height of 500 kilometers, had been investigated. A plane of rotation of the cluster can be changed for 90 degrees using electric rocket engines with the maximum thrust of 2 newtons.

Scientists established that the control system can ensure the accuracy as regard to orientation of not less one thousandth of radian (less than 0.05 degree). “Usage of the mathematical model offers possibilities to examine a larger number of tasks related to space rotating motion of various bodies,” told specialists of the higher educational establishment. At a later time, scientists are going to develop a real space system that allow to remove space debris from the orbit towards necessary direction.

Source: ria.ru