1. On problems of active space debris
removal using tethered towing
Vladimir S. Aslanov and Vadim V. Yudintsev
Samara State Aerospace University (SSAU), Russia
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2. Satellites with flexible
appendages and/or
fuel residuals
Upper stages
with fuel residuals
Large Space Debris:
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3. Tug-Tether-Debris system
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4. • Analysis of the pre-capture motion of the debris
• Pre-burn stabilization of the debris
• Post-burn dynamics and stabilization taking into account
properties of the debris (flexible appendages, fuel)
• Post burn dynamics & motion of the center of mass
• Atmospheric re-entry of the debris
Problems need to be considered
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Solved
Not yet solved

5. Re-enter into atmosphere
Deorbit
Catch & Stabilization
Uncontrolled motion
Operational stage
Active Stage / Separation
Stages
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Initial conditions for the upper stage type
debris uncontrolled motion
Initial conditions for the re-entry
Initial conditions for the catch stage
This stage determine safety of the ADR

6. The attitude motion of the upper
stage (debris) can be predicted using
the models of the perturbing forces
of:
• separation system
• the Earth gravity&magnetic fields
• the atmosphere
• the Moon, the Sun etc.
The motion of the upper stage
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7. The motion of the non-operating satellite
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The attitude motion of the satellite
(debris) can be predicted using the
models of the perturbing forces and
last telemetry data.

8. • Equations for the osculating orbital
elements
• Equations in non-inertial orbital frame
• Flexible appendages: floating frame of
reference formulation
• Sloshing dynamics: pendulum equivalent
models
Mathematical model structure
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1. Equations of the mass
center
2. Equations of the attitude
motion of the system
3. Equations for additional
elements (fuel, flexible
appendages)

9. Forces and Torques
9
• Tug’s thrust
• Tether tension (depend on Young's
modulus, cross section area,
damping)
• Aerodynamic forces
• Gravitational forces and torques
• Magnetic forces and torques
• Sunlight pressure
• Control forces and torques
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10. • Debris
• Flexible
appendages
• Fuel
• Tether
• Stiffness
• Damping
• Tug
• Tether control
Complex model of the tug-debris system
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11. • Figure shows oscillations of the
angles α between the tether and
the axis Oyo of the orbital rotating
frame with undesirably high
amplitudes while θ is small.
• Marked oscillations caused by the
gravitational torque that is
created by the difference between
the gravity forces act on the space
tug and on the orbital debris.
Example: the influence of gravitational torque
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12. Stationary point as a function of tether length
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F=0,3 N
safe

13. Example: closely spaced frequencies
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• The amplitude of the tether vibrations is
influenced by the vibrations of the solar
panels and and vice versa.
• At t=15 the deformation of the panel 2 reach
the breaking strain (dotted red lines) causing
structure failure.

14. Debris with fuel residuals
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• Sloshing liquid is modelled as an
equivalent pendulum.
• The oscillations of liquid are small

15. Example: Nonlinear vs. linearized formulation
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16. We have developed the mathematical model of the attitude
motion of the debris+tether+tug system:
• Tug + Elastic Tether + Debris with flexible appendages
• Tug + Elastic Tether + Debris with fuel residuals
Conclusion
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17. • Capture dynamics of debris (harpoon, net, lasso ...)
• The stabilization phase after debris capture
What we will intend to do?
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We will study:
We will create comprehensive model for all stages:
from the capture to re-entry

18. Rigid body debris
[1] V.S. Aslanov, V. V. Yudintsev, Dynamics of Large Debris Connected to Space Tug by a Tether, J.
Guid. Control. Dyn. 36, 2013. P. 1654–1660.
[2] V. Aslanov, V. Yudintsev, Dynamics of large space debris removal using tethered space tug, Acta
Astronaut. Volume 91, 2013, P. 149-156.
Debris with flexible appendages
[3] V. S. Aslanov, V. V. Yudintsev, Behaviour of Tethered Debris With Flexible Appendages Acta
Astronaut. 104, Issue 1, 2014. P. 91-98.
[4] V. S. Aslanov and V. V. Yudintsev Dynamics, Analytical Solutions and Choice of Parameters for
Towed Space Debris with Flexible Appendages. Adv. Sp. Res. Volume 55, Issue 2, 2015. P. 660-667.
Debris with fuel residuals
[5] V. S. Aslanov and V. V. Yudintsev The motion of tethered tug-debris system with fuel residuals.
Adv. Sp. Res. (Accepted for publication).
Re-entry
[6] V. Aslanov, A. Ledkov, Dynamics of towed large space debris taking into account atmospheric
disturbance, Acta Mech. Volume 225, Issue 9, 2014. P. 1-13.
Publications
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19. Thank You for attention
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20. • Vladimir S. Aslanov
Prof., Head of the Theoretical Mechanics Department,
Samara State Aerospace University
aslanov_vs@mail.ru
http://aslanov.ssau.ru
• Vadim V. Yudintsev
Associate Prof., Theoretical Mechanics Department,
Samara State Aerospace University
yudintsev@classmech.ru
http://yudintsev.info
Authors
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