imrsIn the 2012 movie “The Avengers,” Captain America, the Hulk, Iron Man and the rest of the gang flew on a massive aircraft carrier that carried dozens of planes through the air and disappeared from plain view with the help of a cloaking device. The idea that the U.S. military could develop something similar is still seen as far-fetched, but this much is true: a Pentagon agency has just launched a new effort to develop an airship sure to draw comparisons. More