Analysis of Interstellar Spacecraft Cycling Between the Sun and the New Stars

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R. W. Moir; W. L. Barr (2005), JBIS, 58, 332-341

Refcode: 2005.58.332
Keywords: Cycling interstellar spacecraft, cyclic interstellar orbits, minimum travel time interstellar orbits, world ship cyclic trajectory

Abstract:
This paper explores what cyclic trajectories are possible within the limits of known laws of physics and practical propulsions systems for a spacecraft or world ship that could travel between the Sun and the near stars periodically. Because of the long durations, the spacecraft is assumed to be massive to house many people for many generations. The spacecraft is initially accelerated up to speed at great expense but from then on only minimal propulsion is assumed to be available for course corrections. The spacecraft, as it nears a star, follows a hyperbolic trajectory. The spacecraft returns by using gravity to “swing” around each of three or more stars, one of which is the Sun. The minimum distance of closest approach found during the flyby was 3 Sun radii, where the heat flux of 7 MW/m2 was shielded from the spacecraft by a radiation-cooled shield made of a porous woven carbon fiber whose peak temperature was about 2500 K. A thin sheet of graphite by contrast would have a temperature of 2800 K and high evaporation mass loss rate. The coasting speed was found to be 115 km/s or 0.0004c. The minimum period found for this class of trajectory was about 41,000 years for a trip around three stars with a 16 light-year closed path and about 57,000 years for four stars with a 22 light-year path length. If an order of magnitude more heat flux could be handled somehow, then the spacecraft could just skim the surface of the Sun (200 km/s or 0.0007c) giving a minimum cycle time of 24,000 years for three stars and 33,000 years for fours stars.

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