Portland, Ore. 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.
The Air Force's Combat SkySat was subject to preliminary helium balloon tests in the Arizona desert earlier this year. Likewise, Lockheed Martin has done preliminary tests of its prototype for a High Altitude Airship and expects to conduct full tests in 2006. Both blimps are roughly 500-foot-long, unmanned, radar-carrying surveillance vehicles that will be able to hover for months, tracking ground activity with a payload of thousands of pounds of sensors and other equipment. Lockheed's airship is designed specifically to track incoming missiles, and with a 750-mile-wide viewing range per blimp, just 10 of them could provide missile defense for all U.S. coastal regions.
Neither the Air Force's SkySat nor Lockheed's airship, however, will be fast-reacting, since both will be ground-launched. By contrast, Johns Hopkins' "disposable" blimp officially called the High Altitude Reconnaissance Vehicle (HARVe) can be packaged for rapid deployment from a missile. Each HARVe will carry about 100 pounds' worth of sensors, will likely be used only for a month or so and will cost just $100,000, according to Johns Hopkins.
"Specifically, we have been looking at deployment from a Tomahawk Cruise missile," said Neradka. "HARVe could be launched with the existing infrastructure of the Tomahawk, and the missile has the range to penetrate areas of denied access that are 400 or 500 miles away from the battleship or submarine that launches it. It can get up to its altitude in a very short time and then do the inflation [of the blimp] and the housekeeping. The blimp can then hover over an area, doing what we call station-keeping, using GPS to keep itself flying over the same spot."
Power by solar cells
Neradka recently worked with three engineering undergrads who built a 17-foot-long version of HARVe as their senior project. The project proved so successful that Neradka said he now views the students' blimp as a low-altitude test bed for HARVe.
The craft carries no fuel; it's powered entirely by solar cells on its upper surface. The cells power the on-board sensors as well as the propulsion system that allows the craft to fight the wind and stay in position. The solar cells also provide sufficient energy to charge batteries, which would fuel the sensors and propulsion propellers during the night.
"Our goal is for [deployment] durations on the order of months, which would certainly accomplish the military's need for quick-reaction reconnaissance," said Neradka. "HARVe will be up in the realm of 100,000 feet. There is a lot of interest in surveillance from those altitudes. HARVe will cruise lower than low-orbit satellites but can hover like a geosynchronous satellite."
Military reconnaissance could use disposable HARVes to track enemy troop movements or the comings and goings of suspected terrorists. HARVe could be ejected from a missile above areas of interest to surveil as well as provide a communications node. The technology could greatly enhance the U.S. military's ability to survey large areas of land, John Hopkins believes.
Mike Chin, Ben Jackson and Nick Keim, the engineering majors who worked on the 17-foot prototype, built their own navigation, guidance and control systems into a small commercial blimp to complete the design during a two-semester course. The prototype craft can be piloted using a wireless remote or can employ an on-board computer for preprogrammed flights. It hovers 50 to 200 feet off the ground.
The commercial blimp used was capable of carrying a 10-pound aluminum gondola, equipped with two propellers facing forward and two reversible propellers, plus a video camera and the electronic navigation control and guidance system.