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V. A. Obukhov et al.
10.1 Introduction
Much attention has recently been paid to the removal of space debris object (SDO)
from near-Earth space. Many different methods of removal of large objects on the
disposal orbits or low orbits for their destruction in dense layers of the Earth’s atmosphere are proposed. The concept of contactless removal of SDO (so-called Ion
Shepherd technology) was proposed in [1], according to which the SDO orbit is
altered by a high-velocity ion beam injected from a service spacecraft (SSC) moving
in immediate vicinity of SDO. There are quite a few publications that address some
or other issues of controlling the SSC-SDO cluster during the contactless removal.
In [2, 3], such issues were considered in a broad sense; however, they did not take
into account the peculiarities of the SSC design.
Within the framework of the Ion Shepherd concept, the SSC scheme was proposed
in [4], in which electric propulsion system (EPS) comprising two electric propulsion
thrusters (EPTs), each of which is mounted on a two-coordinate gimbal, is used to
produce thrust that should compensate the thrust of a high-velocity ion beam source.
In this case, ion beam source (IBS) and EPS are mounted along the SSC longitudinal
axis.
For such a spacecraft, the strategy and algorithms of controlling the motion of the
SSC center of mass by creating control impacts in the plane orthogonal to the SSC
longitudinal axis were considered in [5]. For numerical modeling and performance
analysis of the considered control algorithms, a simplified model of ion beam impact
on SDO was used in [5].
In this chapter, we consider the problems of controlling the angles of the EPT
rotation to implement changes in the EPS thrust vector components in the direction of
the SSC longitudinal axis and in the transverse direction. Motion control for the SSCSDO cluster, in addition to its lateral motion control, also requires to control the thrust
projection onto the SSC longitudinal axis. Algorithm of thruster rotation angle control
for implementing the required values of the thrust projections that allows to control
the sign of the momentum relative to the SSC longitudinal axis depending on the
accumulated total momentum should be based on a certain arrangement of thrusters,
taking into account the solar arrays location and the difference in permissible thruster
deflection angles in different planes. It should be noted that pivoted thrusters can be
used not only to create the required values of thrust projection onto the axes of the
associated coordinate system, but also to unload the flywheels of the SSC inertial
attitude control system.
Before a description of the thruster rotation angle control, a problem statement
with service spacecraft is described in Sect. 10.2. The ideas of the thruster rotation angle control are introduced in Sect. 10.3. The ion beam momentum transfer
modeling is presented in Sect. 10.4. The results of spacecraft motion dynamics simulation are presented in Sect. 10.5. Finally, the conclusions of the study are reported
in Sect. 10.6.
V. A. Obukhov et al.
10.1 Introduction
Much attention has recently been paid to the removal of space debris object (SDO)
from near-Earth space. Many different methods of removal of large objects on the
disposal orbits or low orbits for their destruction in dense layers of the Earth’s atmosphere are proposed. The concept of contactless removal of SDO (so-called Ion
Shepherd technology) was proposed in [1], according to which the SDO orbit is
altered by a high-velocity ion beam injected from a service spacecraft (SSC) moving
in immediate vicinity of SDO. There are quite a few publications that address some
or other issues of controlling the SSC-SDO cluster during the contactless removal.
In [2, 3], such issues were considered in a broad sense; however, they did not take
into account the peculiarities of the SSC design.
Within the framework of the Ion Shepherd concept, the SSC scheme was proposed
in [4], in which electric propulsion system (EPS) comprising two electric propulsion
thrusters (EPTs), each of which is mounted on a two-coordinate gimbal, is used to
produce thrust that should compensate the thrust of a high-velocity ion beam source.
In this case, ion beam source (IBS) and EPS are mounted along the SSC longitudinal
axis.
For such a spacecraft, the strategy and algorithms of controlling the motion of the
SSC center of mass by creating control impacts in the plane orthogonal to the SSC
longitudinal axis were considered in [5]. For numerical modeling and performance
analysis of the considered control algorithms, a simplified model of ion beam impact
on SDO was used in [5].
In this chapter, we consider the problems of controlling the angles of the EPT
rotation to implement changes in the EPS thrust vector components in the direction of
the SSC longitudinal axis and in the transverse direction. Motion control for the SSCSDO cluster, in addition to its lateral motion control, also requires to control the thrust
projection onto the SSC longitudinal axis. Algorithm of thruster rotation angle control
for implementing the required values of the thrust projections that allows to control
the sign of the momentum relative to the SSC longitudinal axis depending on the
accumulated total momentum should be based on a certain arrangement of thrusters,
taking into account the solar arrays location and the difference in permissible thruster
deflection angles in different planes. It should be noted that pivoted thrusters can be
used not only to create the required values of thrust projection onto the axes of the
associated coordinate system, but also to unload the flywheels of the SSC inertial
attitude control system.
Before a description of the thruster rotation angle control, a problem statement
with service spacecraft is described in Sect. 10.2. The ideas of the thruster rotation angle control are introduced in Sect. 10.3. The ion beam momentum transfer
modeling is presented in Sect. 10.4. The results of spacecraft motion dynamics simulation are presented in Sect. 10.5. Finally, the conclusions of the study are reported
in Sect. 10.6.