Actually The Pilgrim Project, by Hank Searls.
From jacket flap:
When a routine orbital flight is interrupted for no reason and at a tremendous cost to the nation official excuses are too lame to satisfy the press, and far too mysterious for a crew brought back to earth without apparent reason. But one of the crew members, a famous colonel, does understand, and can scarcely conceal his elation, for he has long since been chosen for a top-secret project that will land him on the moon, and he knows that the moment has come.
When the colonel is suddenly replaced by Steven Lawrence, a young civilian astronaut, because the Russians, to prove their peaceful intentions, are sending up a civilian specialist, our space experts and politicians, scientists and astronauts are plunged into a deadly secret debate over the purposes, the means, and the aims of a project that begins to seem more suicidal than heroic in proportions.