For nearly a century, the image of the Airstream travel trailer, with sunlight gleaming off the aluminum of its sleek silver-bullet body, has evoked the romance of escape and the mystique of a world where a new adventure is waiting just over the next hill. No matter the model of Airstream — Bambi, Caravel, Flying Cloud, Tommy Bahama, Classic, Serenity — Wally Byam’s invention o...