Timeline for Exorcist, Ninth Configuration

Since Cutshaw is the same astronaut who the possessed Regan in the Exorcist tells "You're going to die up there," I wonder about the timeline.

Are we to assume that the events of The Ninth Configuration take place after the Exorcist, and that Regan's comments caused Cutshaw's breakdown at launch? That seems reasonable, but there are some problems with this. First, the events of the Exorcist take place toward the end of the Vietnam war, while the events in Ninth Configuration take place in the midst of it. Second, Twinkle Twinkle Killer Kane was written before The Exorcist.

So my take has been that Cutshaw had the fear of dying alone in space long before the events in The Exorcist, and the Regan/the Demon were just using his past fears to torment Cutshaw at the dinner party.