Monday, July 8, 2013

1307.1648 (Arwen Nicholson et al.)

Slingshot Dynamics for Self Replicating Probes and the Effect on Exploration Timescales    [PDF]

Arwen Nicholson, Duncan Forgan
Interstellar probes can carry out slingshot manoeuvres around the stars they visit, gaining a boost in velocity by extracting energy from the star's motion around the Galactic Centre. These maneouvres carry little to no extra energy cost, and in previous work it has been shown that a single Voyager-like probe exploring the galaxy does so 100 times faster when carrying out these slingshots than when navigating purely by powered flight (Forgan et al. 2012). We expand on these results by repeating the experiment with self-replicating probes. The probes explore a box of stars representative of the local Solar neighbourhood, to investigate how self-replication affects exploration timescales when compared with a single non-replicating probe. We explore three different scenarios of probe behaviour: i) standard powered flight to the nearest unvisited star (no slingshot techniques used), ii) flight to the nearest unvisited star using slingshot techniques, and iii) flight to the next unvisited star that will give the maximum velocity boost under a slingshot trajectory. In all three scenarios we find that as expected, using self-replicating probes greatly reduces the exploration time, by up to three orders of magnitude for scenario i) and iii) and two orders of magnitude for ii). The second case (i.e. nearest-star slingshots) remains the most time effective way to explore a population of stars. As the decision-making algorithms for the fleet are simple, unanticipated "race conditions" amongst probes are set up, causing the exploration time of the final stars to become much longer than necessary. From the scaling of the probes' performance with star number, we conclude that a fleet of self-replicating probes can indeed explore the Galaxy in a sufficiently short time to warrant the existence of the Fermi Paradox.
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