design space pruning heuristics and global optimization method for ...

≤
Because these are all near-Earth asteroids, their semi-major axes all fall between 0.9 AU
and 1.1 AU. All have low inclination orbits – less than 10 degrees – while their
eccentricities range from near circular to a maximum value of 0.87. Note that this is a
significantly different design space than in the GTOC2 problem.
In addition, the objective function for GTOC3 is also slightly different, as it
involves maximizing a combination of final mass and stay time at the asteroids:
J =
m
m
f
i
min
j=
1,3
+ K
τ
( τ )
max
j
(19)
In Equation 19, m i and m f are the spacecraft initial and final mass, τ j is the stay time at the
j th asteroid, τ max is the maximum allowable flight time, and K = 0.2. Unlike GTOC2,
gravity assists using Earth were permitted. Additional problem constraints are listed in
Table 13.
Table 13: Constraints on GTOC3 problem.
Constraint Value Notes
Earth Launch VB∞B 0.5 km/s Unconstrained direction
Earth Launch Date 2016 – 2025 Inclusive
Asteroid Stay Time ≥ 60 days
Total Flight Time ≤ 10 years
Spacecraft Initial Mass 2000 kg
Thruster Isp
3000 s
Maximum Thrust 0.15 N
Can be turned on/off at will
No constraint on direction
For the purpose of validating the proposed methodology, the problem is altered
slightly. The objective function is changed to maximizing the final mass at Earth return.
This does not change the problem significantly, since the maximum value of the stay time
portion of the GTOC3 objective function contributes only marginally to the overall
objective function. The first portion of the original objective function will be on the
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