Thrust control of tethered satellite with a short constant tether in orbital maneuvering

Abstract

Tethered satellite with chemical propulsion has broad application prospects in the space debris removal, the orbital transfer of space detector and the orbital rescue of malfunctioning satellite. In orbital maneuvering, tethered satellite with a short constant tether can avoid using certain windlass mechanism of base satellite, which is helpful for the implementation of project. In this article, based on a dumbbell model of tethered satellite, dynamic equations of tethered system in orbital maneuvering are established. Furthermore, taking elastic strain of the tether into account in the dynamic model, as the slackness of tether occurs, the effects on tethered satellite of the degree of slackness, initial states of librational angles and the variation of thrust acceleration are analyzed. To avoid several adverse phenomena aroused by the slackness of tether, such as tether winding or collision between satellites, a thrust control method of tethered satellite with a short constant tether in orbital maneuvering is proposed. In this method, the thrust acceleration imposed on the base satellite can be adjusted to avoid the slackness of tether and damp out the librational angles; meanwhile, it is required that the regulating value of thrust acceleration meets with accuracy requirements of orbital trajectory in practical engineering; therefore, a continuous thrust controller is presented based on the feedback of tether tension; besides, considering in practical engineering that the continuous thrust is always replaced by an impulse thrust, the ranges of impulse thrust parameters, such as impulse width and duty cycle, are studied. Afterwards, an orbital transfer case between two circular orbits is studied to demonstrate the effectiveness of the tethered satellite with a short constant tether in orbital maneuvering. In this case, an orbital transfer strategy for tethered satellite is designed based on a continuous thrust. Numerical simulation results show that the slackness of tether can be eliminated and the librational angles are damped out according to the thrust control scheme in orbital maneuvering; in addition, the stability of tethered system could be guaranteed by the designed thrust controller, which is useful for flight safety.