But with the Sept. 11 terrorist attacks, the U.S. military has been forced to reassess threats, and two major defense contractors are pitching the zeppelin as a potential piece in the homeland security puzzle. Military planners envision unmanned airships as high-altitude radar platforms keeping watch for anything trying to penetrate U.S. airspace.
"What Sept. 11 proved is the ability of a group of people being able to outwit a sophisticated country by using unconventional methods," said Nick Cook, a London-based aerospace consultant for Jane's Defense Weekly. "You can put as much into an SDI (Strategic Defense Initiative) Star Wars type thing as you want and a cruise missile would sneak under, but an airship could plug the gap."
The surface radar arrays that currently watch U.S. borders cannot see into valleys and ravines, and surveillance satellites are limited to glimpses because of the earth's rotation, Cook said. The zeppelins would provide essentially the same view as radar-equipped planes, but could be kept aloft for months at a time.
Two of the largest companies developing dirigibles are Boeing, through its partnership with Germany's CargoLifter AG, and Lockheed Martin's subsidiary Goodyear Aerospace. They say they have airships ready to be built should the government need them.
Critics worry that the big airships might interfere with air traffic and have to be grounded during storms, but North American Aerospace Defense Command, or NORAD, is looking at stratospheric ships that would float at 70,000 feet - well above weather systems and commercial air traffic, said Pentagon spokesman Lt. Col. Rivers Johnson.
Modern materials allow today's airships to hit altitudes that would have been unimaginable when the first ones flew in France in 1852.
Also, airships are now filled with nonflammable helium instead of the explosive hydrogen that made the Hindenburg catch fire in 1937 in Lakehurst, N.J., killing 35 of the 97 people on board.
"They're marvelous," said pilot Hans-Paul Stroehle, using a joystick to maneuver the zeppelin Bodensee over Berlin on a recent sunny spring day, with a dozen tourists aboard. "The only thing similar to the 80- or 90-year-old airships is the shape - otherwise it's all modern materials and technology."
The U.S. Coast Guard and U.S. Customs Service use radar on low-altitude tethered balloons to look for drug smugglers. Israel used a similar balloon carrying cameras to monitor Bethlehem's Church of the Nativity during its recent standoff with Palestinian militants.
This month NORAD asked for U.S. government funding to build a prototype high-altitude airship, with the idea of stationing 10 ships to cover all the continental borders of the United States, said Maj. Ed Thomas, a NORAD spokesman. Canada, the United States' partner in NORAD, is looking separately at airship technology, but might participate in a U.S. program, Thomas said.
"They would look for anything that traditional radar looks for ... ICBMs, cruise missile threats, air threats," Thomas said.
CargoLifter, which sold its first tethered balloon designed to lift heavy cargo in March, entered an agreement this month to collaborate with Boeing's Phantom Works. Chief financial officer Karl Bangert said plans for the largest piloted airship ever built could be adapted to be an unmanned radar platform.
CargoLifter, which has been maneuvering in recent weeks to stave off bankruptcy, just needs a contract to get the project started, Bangert said. He estimated the airships would cost around $100 million each.
Goodyear Aerospace - maker of the Goodyear blimp - also already has "an engineering concept" to the stage that the company can start building as soon as there is a contract, said Lockheed spokesman Cary Dell.
The zeppelin that Stroehle flies for tourists is too small for use as a high-altitude radar platform, but the Friedrichshafen manufacturer is also looking at another military application - to detect mines.
Trials done in Kosovo for the United Nations have demonstrated that the ability to fly low and slow without the downwash and vibrations of a helicopter make the airship suited for mine detection, Stroehle said.
"It saves years for the ground sweepers," he said.
By David Rising