The nuclear explosion would only impart say, a 100-gees, to the reaction balls during detonation. This gee-load during detonation is what imparts the reaction ball with an instantaneous velocity in a direction perpendicular to its original plane of rotation (3rd dimension thrust). The purpose of the long tether is to allow the reaction balls to swing forward through a long gradual arc, using it like a pendulum to store the energy of the bomb. I don't think the tether would experience the same extreme gee-loading during this process, only the reaction ball, but I could be wrong. A pendulum with a steady force applied, like gravity, is relatively straightforward calculus. But when I add the additional spinning condition instead of gravity, it creates a non-steady centripetal force that depends on radius and initial rotation frequency. I find it quite confusing in fact, and I haven't had a chance to sit down and work it out.

I don't know off the top of my head how much energy is released by a nuclear bomb. How small can they be made? This system doesnt necessarily have to use the Czar bomb to propel it. Another interesting aspect of this is that the pendulum effect could be extremely efficient means of storing the energy of the bomb and converting it into kinetic energy. The Orion pusher-plate system used shock absorbers, which would instead waste huge amounts of energy by converting the impulse of the explosions into heat! The Nuclear Pulse AutoGyro would act like a pure spring instead, but with a very gradual vibrational motion in the direction of travel.