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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elative to the asteroid at arrival <strong>and</strong> v ast<br />
is the heliocentric velocity of the asteroid.<br />
GTOC2 required participants to <strong>design</strong> a low-thrust trajectory that rendezvous with one<br />
asteroid in each of four predefined groups, while maximizing the ratio of final mass to<br />
total time of flight. 8,9<br />
For this problem, no gravity assists were allowed. GTOC3 also<br />
involved a multiple-asteroid rendezvous mission, but in this case the goal was to <strong>design</strong> a<br />
low-thrust trajectory that would rendezvous with three asteroids out of a single group of<br />
140 <strong>and</strong> then return to Earth. 10 Gravity assists of Earth were allowed <strong>and</strong> the objective<br />
function was to maximize a weighted combination of mass ratio <strong>and</strong> the minimum stay<br />
time at the three asteroids. Most recently, the GTOC4 problem asked participants to<br />
maximize the number of asteroids visited (via a flyby) en route to a rendezvous with a<br />
final asteroid, without the use of any gravity assists. 11<br />
There were 1436 c<strong>and</strong>idate<br />
asteroids <strong>for</strong> participants to choose from.<br />
In light of the recent developments in electric propulsion <strong>and</strong> emerging scientific<br />
interest in asteroids, this work will focus on the development of a <strong>method</strong>ology <strong>for</strong><br />
solving a multiple-asteroid rendezvous low-thrust mission <strong>design</strong> problem at the<br />
conceptual <strong>design</strong> level. Two specific types of asteroid rendezvous problems are<br />
considered. First is the case of rendezvousing with one asteroid from each of a given<br />
number of predetermined groups, as presented in the GTOC2 problem. This type of<br />
mission would be relevant if the goal were to visit asteroids with different scientific<br />
properties. The second type of problem is to rendezvous with several asteroids out of a<br />
single group, such as the Near Earth Asteroids (NEAs). In either case, a <strong>space</strong>craft could<br />
return to Earth at the end of the mission duration, which would be representative of a<br />
sample return mission. Because the target application is conceptual <strong>design</strong>, the goal will<br />
be to identify a large set of good solutions to a given multiple-asteroid rendezvous<br />
mission. Unlike the GTOC competitions, which required only a single best solution to be<br />
submitted, the result of the <strong>method</strong>ology will be a suite of solutions that could then be<br />
carried <strong>for</strong>ward into the more detailed <strong>design</strong> phases, where higher fidelity analysis with<br />
3