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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CHAPTER III<br />
OVERVIEW OF METHODOLOGY<br />
The final <strong>method</strong>ology combines a three-level heuristic <strong>pruning</strong> step, which<br />
quickly reduces the size of the <strong>design</strong> <strong>space</strong>, with a multi-level <strong>global</strong> <strong>optimization</strong> step,<br />
which locates a suite of good solutions. Each of the steps of the <strong>method</strong>ology is<br />
presented here, followed by a discussion of the assumptions <strong>and</strong> scope.<br />
3.1 Overview of Methodology<br />
The <strong>pruning</strong> phase of the <strong>method</strong>ology applies three <strong>pruning</strong> metrics, in order of<br />
required computation time:<br />
(1) a i ≤ a i+1 – keep only asteroid sequences where the semi-major axis of the<br />
asteroids increases from one asteroid to the next<br />
(2) θ wedge – angle between the angular momentum vectors of asteroid pairs<br />
a. θ wedge is computed <strong>for</strong> all Leg 1 (Earth – 1 st asteroid) asteroid pairs; the<br />
worst k 1 percent is eliminated from the <strong>design</strong> <strong>space</strong>.<br />
b. θ wedge is computed <strong>for</strong> all remaining Leg 2 (1 st asteroid – 2 nd asteroid)<br />
asteroid pairs; the worst k 2 percent is eliminated from the <strong>design</strong> <strong>space</strong>.<br />
c. θ wedge is computed <strong>for</strong> all remaining Leg 3 (2 nd asteroid – 3 rd asteroid)<br />
asteroid pairs; the worst k 3 percent is eliminated from the <strong>design</strong> <strong>space</strong>.<br />
d. θ wedge is computed <strong>for</strong> all remaining Leg 4 (3 rd asteroid – 4 th asteroid)<br />
asteroid pairs; the worst k 3 percent is eliminated from the <strong>design</strong> <strong>space</strong>.<br />
(3) ∆V opt – optimal two-impulse, phase-free delta-V between asteroid pairs<br />
a. ∆V opt is computed <strong>for</strong> all remaining Leg 1 (Earth – 1 st asteroid) asteroid<br />
pairs; the worst k 1 percent is eliminated from the <strong>design</strong> <strong>space</strong>.<br />
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