For seven decades, they were a curiosity, a relic of a lighter-than-air future that never quite came true. But in recent years, airships have once again become a major force in aviation. The Pentagon has gone especially blimp-crazy, pouring hundreds of millions of dollars into advanced -- and massive -- surveillance airships that can stay in the sky way longer than any drone. Here are some of the new Blimps of War.

This "freakishly large" airship would hover 20,000 feet above ground, using its on-board supercomputer to spy for miles around. The power comes from up to 12 different sensors, including an eavesdropping unit and nine tiny cameras that talk to each other while adjusting precisely where to look and listen. After collecting all that data, the Blue Devil has enough real estate on board to do much of the processing in the air – no human analyst required.

According to retired Lt. Gen. David Deptula, "it could change the nature of overhead surveillance." For one, he estimates it'd be a lot cheaper, costing about $1,000 per hour (compared to the $8,000 of other airships).

The construction of this longer than a football field blimp is still underway, but it's expected to be ready for the Air Force by January. Right now, the same surveillance gear that would be used on the airship is already in Afghanistan atop four Blue Devil planes.

Photo: USAF