Pilots who can swivel their heads to cheek six on successive six-g turns without losing concentration may gain a tactical edge over those who can't. And fighter pilots are always looking for an edge.

Any story about what goes on at Brooks AFB in San Antonio, Texas, has to begin with the human centrifuge. The centrifuge is big, flashy, and fast. It's high-tech reminiscent of a carnival ride.

"Every g-LOC episode goes through two relatively distinct periods. The first is a period of absolute incapacitation in which the subject is ...unconscious. The second is a period of relative incapacitation — a sort of semi-consciousness. During this period, the subject appears to be responsive, but actually isn't.