From: defensetech.org

The problem with the American military today is that it doesn't have a giant, robotic airship, two-and-a-half times the size of the Goodyear blimp, that can watch over an entire city at once. Thankfully, the Pentagon's way-out research arm, Darpa, is trying to fix that.

The program is called ISIS, short for "Integrated Sensor Is Structure." And the idea is to park an unmanned airship over a hot zone for a year, at nearly 65,000 feet in the sky. Up there, ISIS can spot enemy soldiers up to 180 miles away, target tanks and trucks, and watch out for incoming cruise missiles 350 miles in the distance -- a "detailed, real-time picture of all movement on or above the battlefield," one Darpa program manager says. During down times, ISIS might even serve as a cell tower in the sky, relaying communications to U.S. troops.

But to pull it all off, almost the entire hull of the ISIS ship would have to be turned into a phased-array radar antenna. And that is no mean task.

To get the airship to fly, the antenna would have to weigh about 2 kilograms/meter -- as opposed to 20 kg/m today. And new tricks in power storage will be needed, too -- batteries that can store a kilowatt-hour's worth of juice in half a kilogram, instead of the 2 kg currently required.

Darpa, along with the Air Force Research Lab, just handed Lockheed Martin the latest in a $42.5 million series of contracts to develop components the uber-blimp. If all goes well -- and that's a big, fat if -- the ISIS could fly by 2011.

Article from: http://www.defensetech.org/archives/002541.html