When the U.S. military stormed Fallujah, it relied on a range of aerial surveillance sources � high-orbit geosynchronous satellites deployed 20,000 miles over Iraq, low-Earth-orbit probes that scanned the horizon from just 20 miles up, unmanned Predator drone aircraft surveying the ground below from an altitude of 65,000 feet. None of those eyes in the sky, however, was cheap enough to be considered disposable, nor could any hover in the "no-man's land" above aircraft but below satellites. Now Johns Hopkins University has developed a blimp that it claims will achieve both aims. "What we can do is what a satellite cannot do � provide persistent intelligence, surveillance and reconnaissance from no-man's land" at a relatively low cost, said Vincent Neradka, an engineer at Johns Hopkins' Applied Physics Laboratory in Baltimore. No-man's land isn't just an expression in this context: It's the gap between the 65,000-foot ceiling of commercial aircraft and the 100,000-foot (20-mile) minimal distance required for low-Earth-orbit satellites. Nor is Johns Hopkins the only organization targeting that void: Unmanned military blimps from the U.S. Air Force Space Command and Lockheed Martin are close to deployment.