Iman Alizadeh
University of California, Irvine
Image from http://dawn.jpl.nasa.gov/multimedia/images/vestaorbit_300.jpg
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Designing Space missions with low-cost.
 Low-thrust propulsion technology are very efficient
Image Credit: NASA/JPL
Image Credit: NASA/JPL
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Designing Space missions with low-cost.
 Low-thrust propulsion technology are very efficient
BUT
Time of powered flight is long
Very low control authority T/W < 0.01
Risk of failure (continues thrust)
Image Credit: JAXA
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In multi-body environments trajectories are very sensitive to
perturbations ( Launch errors, temporary engine loss, …)
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Stability is critical for low-thrust missions in multi body
environments.
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Current trajectory design methods do not take the
risk from loss of control into account.
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Sensitivity analysis is preformed by Monte Carlo
simulation around the reference trajectory which is
computationally expensive.
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Provide methods to reduce the sensitivity and
increase the life-time of low-thrust trajectories.
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Modeling
Indirect stability improvement
Direct stability improvement
Conclusions and future works
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Circular Restricted Three Body Problem
U
 2 y
x
U
y 
 2 x
y
U
z 
z
x 
U
1 2
1  
x  y2 

2
r1
r2


V 2  x 2  y 2  z 2
C  2U  V 2
Jacobi constant
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Equilibrium points, periodic orbits and invariant manifolds
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CRTBP dynamics
J= maximizing payload at final time
Solution: shooting method
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How to reduce sensitivity of the reference
trajectory to loss of control?
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Remains small
in case of loss of control
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How to improve the life-time characteristics of
an optimal trajectory?
Important to address planetary protection
requirements
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1- Design an optimal
retargeting trajectory for the
initial condition.
2- Integrate the fuel-optimal
retargeting trajectory
backward in time.
3- extract the required control
to traverse the backward
integrated path.
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Improving robustness of low-thrust trajectories to loss of
control systematically by:
 Minimizing the angle between controlled and
uncontrolled vector field.
 Back-propagating an optimal retargeting trajectory and
extract control using inverse dynamics.
 The proposed methods are computationally less
expensive than traditional approaches.
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Considering the constant specific impulse
engines for the transfers.
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Investigation of the optimality of the inverse
dynamics.
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Design of robust guidance scheme to account
for engine performance degradation.
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Thank YOU !
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