I am trying to find out if there is any reason other than cost that Breakthrough Starshot is only looking at Alpha Centauri. It seems to me that once the laser system is in place that creating more nanocraft to go to other, even more interesting, places would be just a matter of mass production. I also wonder if a space-based laser satellite may be better as it may be able to accelerate the ships more slowly for a longer period of time. Is such a laser satellite using nuclear or solar power not feasible or again just too costly? I tried to find answers on their website, but was unsatisfied.
The laser needs to be very powerful. The largest powerplant we have in space today is the ISS, with about 200 kW peak power. Breakthrough Starshot are talking about GW of power. We'd have to ramp up the space industry by a factor of 1000 to make a space-based laser that large feasible.
Our current best estimate for the Star Shot ground-based approach is it will cost on the order of \$10 B. We estimate the space-based approach to cost on the order of \$100 B.
We intend to send probes to planets in the habitable zone around nearby stars. The Alpha Centauri system is the closest sun-like star, which is why it is our first target. About 80% of the nearby stars are dwarf stars; there is a debate if life is possible in these systems.