Printed in 1971. Its hard to find a copy of this book in print.
From the back cover: "The mindship was the break-through to the stars. In spite of working on Faster Than Light, hyperdrives, and such, it was the power of the mind that turned out to be the most certain directionf force between the worlds. So the mindships came into being, drivein forward by the lines of mental energy, directed by trained crews -- and held together not by the navigator or the captain but the man they called the cork.
He was just another man but he had the ability to siphon out the discords which could wreck a ship, to create the harmony without which starflight would be disatrous.
Kilgarin was such a "cork," but he had deliberatly grounded himself until they forced him to take up the mental reins again. It was their risk and they should have known better -- because Kilgarin had ulterior motives no ship's cork had a right to harbor."