design space pruning heuristics and global optimization method for ...
design space pruning heuristics and global optimization method for ...
design space pruning heuristics and global optimization method for ...
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Problem<br />
Description<br />
Small Sample<br />
Problem<br />
Intermediate<br />
Sample<br />
Problem<br />
Modified<br />
GTOC3<br />
Problem<br />
Modified<br />
GTOC2<br />
Problem<br />
Full GTOC2<br />
Problem<br />
Table 31: Summary of <strong>global</strong> <strong>optimization</strong> phase applied to each problem.<br />
# Branch<strong>and</strong>-Bound<br />
Iterations<br />
# Sequences<br />
Requiring<br />
Low-Thrust<br />
Optimization<br />
2 14<br />
2 55<br />
3 17<br />
1 809<br />
N/A<br />
308<br />
(in 2 weeks)<br />
Best Set of Sequences Found<br />
− Optimal solution found<br />
− 5 of the top 10 remaining solutions<br />
found<br />
− Optimal solution found<br />
− 5 of top 9 remaining solutions<br />
found<br />
− Best known solution found<br />
− 8 of the top 10 remaining solutions<br />
found<br />
− Best known solution found<br />
− 7 solutions found with J>80 kg/yr:<br />
− 4 of 4 competition solutions<br />
remaining after <strong>pruning</strong> phase<br />
− 3 new solutions not reported in<br />
competition<br />
− Three new solutions with J>80<br />
kg/yr found that were not reported<br />
in competition<br />
− Better solution would have ranked<br />
3 rd in GTOC2<br />
For the full GTOC2 problem, the branch-<strong>and</strong>-bound algorithm was allowed to run<br />
<strong>for</strong> two weeks to simulate the time constraints from the competition. In those two weeks,<br />
308 asteroid sequences were optimized in low-thrust. Of these, three previously<br />
unknown asteroid sequences were identified with J > 80 kg/yr, the best of which would<br />
have placed third in the competition. Furthermore, Section 5.2.2 analyzed how many<br />
low-thrust <strong>optimization</strong>s would be required to locate the additional known good<br />
solutions. It was determined that using an initial guess <strong>for</strong> the lower bound of 100 kg/yr<br />
(same assumption as was made in the two weeks of analysis), 4,620 asteroid sequences<br />
would have to be optimized in low-thrust in order to locate eight of the thirteen known<br />
solutions with J > 80 kg/yr. The thirteen known solutions include the seven reported<br />
147