1704.03871
Optimized trajectories to the nearest stars using lightweight high-velocity photon sails
Heller, Hippie, Kervella
New means of interstellar travel are now begin considered by various research teams, assuming lightweight spacechips that can be accelerated either via laser or solar radiation to a significant fraction of the speed of light. Recently demonstrated that gravitational assists can be combined with the deflection from the stellar photon pressure to decelerate an incoming light sail from Earth and either fling it around a star or bring it to rest. Demonstrate that such a photo gravitational assist is more effective when the star is used as a bumper (i.e. the sail passes "in front of' the star) rather than as a catapult (i.e. the sail passes "behind" or "around" the star). This increases the maximum deceleration at alpha Can A and B and reduces the travel time of a nominal sail with a mass-to-surface ratio (sigma) similar to graphene (8.6e-4 gram/m^2) from 95 yr to 75 yr. The maximum possible velocity (v_inf) that can be absorbed upon arrival depends on the required deflection angle from alpha Cen A to B and therefore on the orbital phase of alpha Cen AB. Here, calculate the resulting variation of the travel times from Earth to Proxima for the next 300 yr. Then compute the travel times for all stars within about 300 ly with available parallaxes from either Hipparcos or Gaia (about 22,000 in total). Although alpha Cen is the most nearby star system, find that Sirius A, with a luminosity of 24 solar luminosities, offers the maximum possible declaration in the solar neighborhood, and therefore the shortest possible travel times: 69 yr assuming 12.5%c can be obtained at departure from the solar system. Sirius A thus offers the opportunity of fly-by exploration plus deceleration into a bound orbit of the companion white dwarf after relatively short times of interstellar travel.
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