The human organism cannot survive those kind of G forces. The starting, stopping, instant 90 degree turns?
Have heard a couple things on that score:
1. the ‘envelope’ within the craft has a different contextual reality vis a vis inertial forces as seen from outside that envelope.
2. My relative asserted that we had craft that didn’t carry people that did the right angle at light speed stuff.
3. Some reports have talked of a kind of inertial damping mechanism. More have asserted that the envelope within the craft is just so different in terms of such inertial forces from the perspective of outside that envelope that it just is not a problem.
Even knowning that was not enough to convince him that he, his son, and his neighbors had had a joint hallucination. What it did instead was to demonstrate to him that human knowledge of the limitations and possibilities in the physical realm are incomplete.