Spy Blimps and Heavy Lifters
The latest thing in airships.
- By Ben Iannotta
- Air & Space magazine, September 2007
(Page 3 of 4)
O Mighty ISIS
Under a research effort called ISIS (Integrated Sensor Is Structure), engineers at DARPA hope to build a stratospheric airship containing a giant radar antenna. The antenna will double as the interior support structure—a weight-saving design. “We’re really a radar program,” says electrical engineer Tim Clark, DARPA’s ISIS program manager. “The platform just turned out to be a stratospheric airship. And that’s because we wanted big antennas. You can’t get much more surface area than a stratospheric airship.”
The bigger the antenna, the more detail it can see. “If the wind blows a tree and it sways, you’ve got to be able to separate out the tree movements from a vehicle’s movement,” explains Clark. “It’s easier to do if your resolution on the ground or near the ground is small. You have [fewer] things competing.” The 17,200-square-foot antenna would park itself over areas of interest and transmit and receive radar signals that enable it to spot moving trucks, cars, airplanes, and cruise missiles.
Northrop Grumman Electronic Systems of Baltimore, Maryland, and Lockheed Martin’s fabled Skunk Works unit in Palmdale, California, are working on competing ISIS architectures. Lockheed’s Akron unit is developing the lightweight hull materials. If the technology passes a series of reviews, DARPA will shoot for a flight in 2010 or 2011.
21st Century Sampsons
An airship is built to generate lift. Could that lift be harnessed to haul heavy equipment?
Other air freighters have limitations: Cargo planes need runways, and helicopters are expensive—$25,000 an hour or more. And even the most powerful lifter, Russia’s Mil Mi-26 helicopter (see “We Haul It All,” June/July 2006), has limits: Its maximum payload capacity is 30.5 tons, whereas oil companies need to lift objects weighing up to 40 tons.
What makes using an airship as a hauler tricky is that when the craft drops off its load, the sudden loss of weight would make it shoot up in the air, in turn making the helium inside expand until it blew the hull apart. Keeping tons of ballast—dead weight—on hand to counteract the bounce is an “incredibly awkward” solution, Hokan Colting says.
The answer is to build a craft that doesn’t need ballast, or can create its own.
This was one of the goals of a now-defunct DARPA program called Walrus, which aimed to develop a test airship that would match the C-130’s 30-ton lift capacity. Phil Hunt, DARPA’s Walrus program manager, recounts that engineers explored several concepts for generating ballast on the craft. In one, exhaust from combustion engines would be captured and treated with nitrogen gleaned from the air and bottled hydrogen, a process that would produce water and ammonium—liquid ballast that would keep the craft controllable. Once the ship had landed, says Hunt, you could wheel the payload off and the ballast would be sufficient to keep the craft from wafting away.
Though Congress did not fund the Walrus program in 2006, several companies continue to work on such concepts. Hokan Colting won’t discuss 21st Century Airships’ proprietary approach. For the most part, neither will Worldwide Aeros, which is promising a vehicle called Aeroscraft, scheduled to fly in 24 to 36 months. Edward Pevzner, Aeroscraft marketing manager, will say that buoyancy would be managed in part through the compression of helium.
Officials at the SkyCat Group of Cardington, Great Britain, are more open. When viewed from the side, their SkyCat airship will look like the cross-section of an airplane wing. From the front it will look like a flattened cigar. The inside will consist of three chambers filled with helium and ballonets. The helium will provide 60 percent of the lift necessary to take off with a heavy load. For a full load, blowers will push air downward through two hover pads, keeping the craft above water, ice, or rocks. The SkyCat will use propellers to move itself forward.