Interesting thing about the nuclear-propelled spacecraft design is that it was begun years before manned flight and even before the earliest unmanned craft sent to Luna and Venus (by the Soviets -- the USA was far behind until our own manned flights around and to the Earth's moon). I do not see anything about concerns about collisions at 10 percent of the speed of light (I think that was the max speed achievable based on the estimated speed of particles from a nuclear explosions and the Tsiolkovsky Rocket Equation although even at slower speeds, such collisions would be a problem) -- it seems what Dyson et al were concerned about was the ablation of the pusher plate and other effects of the explosions. Is there any discussion of the dangers and how to deal with them?
I am thinking space travel was so new that they perhaps deliberately did not want to dwell on reasons why such a radical new idea would not work since, of course, there would be plenty of opposition to the project without them helping.
