I have been developing my method of reaching another solar system in a beam craft. I am using a beam craft as I want to maintain my story within the realms of possibility and this is the most likely method of travelling vast distances. My Original sketch of an idea Originally I went into it on the following basis: - 1) The craft would be accelerated/ decelerated by solar-powered lasers (and lenses along the route). The craft will use constant acceleration/ deceleration at 1g to/ from a sizable percentage of light speed (say 0.6c). 2) When drifting in interstellar space it will rely upon centripetal forces to produce gravity. 3) The target solar system is circa 11 light years away, and travel times will be circa 15 years ship time and 25 years planet time. My work will be plotted around these timescales and this time dilation. 4) It will be in the future (say a century or two) so we will have some future technology, human lifespans will have increased by a reasonable margin (to 130 years or so) and there will be some sort of Induced Hibernation for large periods of the journey. Trip hazard ahead Here are the various problems I have run into: - a) Power Requirements Regarding the propulsion, obtaining 1 g acceleration using a light sail involves some pretty large mass-specific power levels, at the order of at least 1 to 2 GW/kg. At Earth's distance from the Sun this means I need around 1 square kilometer of solar panels per kg of spaceship I want to accelerate, and that is assuming an unrealistic 100% energy efficiency converting solar energy to laser beam energy. For a 10 ton ship, this means I need a total laser beam energy of 20 TW, increasing to even more during the end of the acceleration phase due to relativistic dilation and distance. Just to give these figures some perspective, a craft of 10 tonnes is about the same as the Apollo Command and Control module, i.e. tiny; and 20 TW is the output of circa 20,000 nuclear power plants. b) Maintaining the laser via lenses along the route With a lens diameter of 1km (no idea how to make such a lens with the necessary precision), I need one lens every ~20 AU (give or take a factor of 4 depending on details). With the proposed acceleration profile, I would need 11000 AU to accelerate, or ~500 lenses. At that level, reflection at the lenses is a significant problem. 20 TW for 1km^2 would give 20MW/m^2, probably too much for the lenses to handle (also for the primary mirror of the laser beam). c) Manufacture of the required equipment Even ignoring the engineering obstacles it will prove to be an incredibly lengthy process simply getting the infrastructure in place. Lengthy communication times and the manufacturer and placement of 500 separate lenses would take at least a century; and by the time you were halfway through the process your technology would have far surpassed your earlier work. d) The problem of deceleration at the target solar system Luckily in my scenario I am allowing for a similar laser and lens set up at the destination star built by an alien civilization. Let's just say that without this in place, decelerating the craft would be practically impossible. Conclusion Even taking the most realistic method of travel, a lot of hand-waving is required.