The Pentagon is looking at some 19th century technology -- gas-filled airships, also known as blimps or dirigibles -- as it tries to transform America's military into a 21st century fighting force.
The Army's Missile Defense Agency is spending tens of millions of dollars to develop what it calls a "high altitude airship."
The unmanned, untethered, helium-filled, solar-powered craft would stay aloft 65,000 feet above Earth for up to a year while carrying 500 pounds of equipment.
According to Pentagon budget documents, officials hope to have a test flight for a HAA prototype as soon as 2008.
A potential use of a HAA would be to patrol a 500-mile buffer zone over the ocean along the U.S. coastline, using infra-red surveillance devices that could spot sophisticated cruise missiles more than 370 miles away and boats on the water nearly 200 miles away.
Backers of the project say airships are much cheaper than manned surveillance aircraft or satellites.
The airship is being developed by defense contracting giants Lockheed Martin Corp., Raytheon Co., and Northrop Grumman Corp.
It could be as much as 17 times bigger than the Goodyear blimp.
It will be covered with a man-made fiber stronger than the material now used for blimps.
This fiber will protect the airship from harsh, high-altitude conditions and possible small-arms fire from enemy forces.
"The vision for this stratospheric platform is an array of sensors to create a radar nearly as large as the airship itself," said Jeffery Mack, program director for the Air Force Research Laboratory in Rome, N.Y.
The military already uses tethered gas-filled balloons -- sometimes called aerostats -- as floating observation posts in operations in Afghanistan and Iraq, and along the U.S.-Mexican border.
Positioned about 1,000 feet above the ground, these balloons are fitted with sensors and cameras.
The Israeli military has also equipped tethered balloons with remote-controlled rifles, turning them into floating snipers.
The history of airships traces back to hot-air balloons, which were first flown by the brothers Joseph and Etienne Montgolfier as early as the spring of 1783.
While the materials and technology are very different, the principles used by the earliest 18th century experimenters continue to carry modern sport and weather balloons aloft.
Early balloons, however, were not truly navigable.
In 1852, French engineer Henri Giffard was credited with creating the first navigable full-size airship after he attached a small, steam-powered engine to a huge propeller and flew through the air for 17 miles at a peak speed of 5 mph.
The invention of the gasoline-powered engine in 1896 led to the production of practical airships, and Brazilian engineer Alberto Santos-Dumont was the first to construct and fly a gasoline-powered airship in 1898.
Dirigibles -- whose name is derived from the French word dirigeable, which means "steerable" -- first saw military duty in World War I.
The Germans and French both used aircrafts as bombers until each side grew better at attacking the other's dirigibles with airplanes.
The French, Germans, British and Americans continued to use them as transports and observation platforms.
In World War II, the United States used airships for coastal patrols and to escort naval convoys, directing ship movements and looking out for submarines.
Only one was ever shot down during that war.
In July 1943, an airship spotted a German submarine on the surface of the ocean near Florida.
As the airship moved into position to attack with depth charges, the submarine fired first, shooting it out of the sky.
The crew survived the attack, but one crew member later died from a shark attack while waiting to be rescued.