When forest fires broke out in a remote area of Massachusetts a couple of years ago, firefighters hampered by a lack of access roads to the blaze relied on helicopters to douse the flames. But the  helicopters were ill-equipped for the task: each small craft could carry only 100 gallons of water. In fact, to extinguish the blaze, firefighters spent several days scooping water from a pond, flying to affected areas, dumping water on the flames, and then returning for more pond water.

Mike deGyurky, a program manager at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., figures there must be a better way to handle such emergencies. His novel approach would entail deploying a giant blimp, perhaps a mile in length. With a capacity of 50,000 tons or more, such an airship could pour more than 10 million gallons of water on a forest fire. It could also be used to transport food and water (perhaps even a small iceberg) to drought-stricken regions, dump tons of dirt and sand on a nuclear reactor to smother an incipient meltdown, or even deploy a vast tarp to contain oil spills from leaky seafaring tankers.

The concept began as a “what-if” exercise spawned during one of JPL’s lunchtime brainstorming sessions. De-Gyurky was also inspired by Theodore von Karman, JPL’s cofounder who speculated about mile-long blimps after conducting research on lighter-than-air vessels in the 1930s.

“We’re basically taking von Karman’s idea and applying technologies that have become available in the intervening 60 years,” deGyurky explains. “These include lightweight materials-synthetic fibers such as Kevlar, graphite epoxies, and the like-that are awesome in strength, and thin-film solar cells that would line the roof of the airship and provide most of the propulsive power.”

DeGyurky’s idea is still in the conceptual stage, and it’s unclear whether the plan will ever reach fruition. Nevertheless, interest in developing airships for a variety of transportation needs is rising again, 60 years after the Hindenburg explosion in 1937 grounded the commercial industry. For example, Lloyd Van Warren, deGyurky’s former colleague at JPL who now heads his own engineering firm, Warren Design Vision in Little Rock, Ark., has a somewhat different notion. Instead of a single gigantic ship, Warren is pursuing a “train in the sky”-a string of blimps linked together like sausages.

This “skytrain” would offer several advantages, according to Warren. “Flying in formation would reduce aerodynamic drag,” he says. “With a train of 50 airships, as opposed to 50 independent airships, you could realize perhaps a 50 percent savings in energy, and the savings go up as the speed of travel increases. That’s why ducks fly in formations, bicyclists ride in packs, and trucks travel in convoys.” Flexibility is another advantage: a train flying from Seattle to San Diego could uncouple along the way, dropping cars in Portland, San Francisco, and Los Angeles, and thus enable passengers and goods to travel nonstop. Security is an added bonus: whereas the failure of a gigantic blimp would mean great financial loss for its owner, one car in a string could go down without jeopardizing the entire train. Finally, solar-powered propulsion would operate virtually pollution-free.

Warren has analyzed “sky boxcars” of varying sizes-everything from a 46-foot-long ship costing about $300,000 to a half-mile-long $9 billion unit. Although preliminary price estimates are daunting, he predicts that costs could come down considerably as the price of solar cells, by far the most expensive element, continues to drop. That would raise the economic viability of skytrains and the prospects that  the idea will ever proceed beyond the computer modeling stage.

The skytrain is not the only grandiose proposal being floated these days. Charles Owen, a professor of design at the Illinois Institute of Technology, and his students won the Bronze Prize at the 1993 International Design Competition in Osaka, Japan, for their conception of the AeroCarrier, a mile-and-a-half-long airship that would be “like a city in the sky,” according to Owen. The egg-shaped structure, designed to be longer than the Sears Tower is tall, would carry 3,500 passengers and crew members and still haul 35,000 tons of cargo-more than four times the capacity of the largest seafaring container ships. Once filled with helium gas, the AeroCarrier would stay aloft indefinitely. Loading and unloading of passengers and cargo would be handled by six smaller vehicles called shuttle pods.

Owen concedes the odds are slim that an airship on the mammoth scale he proposes would ever be built. But the idea has generated inquiries from several businesses, he says, including a company in Iowa interested in using an airship to transport grain, and a Texas firm that would deliver heavy oil-drilling equipment to Siberia. The attraction, says Owens, is the ability to move “very big things” not feasible by standard air freight.

Fredrick Ferguson, head of the Pan Atlantic Aerospace Corp. in Ottawa, has also received inquiries about his Cargo Airships, which are much closer to realization. In fact, Pan Atlantic has already designed a 1,500-foot-long airship composed of modular, cylindrical sections. Each section would be amenable to mass production-a feature that could make the airships “cheaper than anything that flies,” Ferguson says.

Airships have never been cost-competitive before, because there’s never been mass production in this industry.” He estimates that transport costs would be about four times lower than conventional air cargo-operating at a projected cost of 10 cents per ton-mile, compared with  the 40-to-50 cents per ton-mile charged by standard air carriers. Although several times slower than cargo airplanes, the cargo airships could deliver freight three to four times faster than container ships, Ferguson maintains.

Pan Atlantic has built and flown two 50-foot prototypes and hopes to have a 600-footer up and running soon. Meanwhile prospective customers, including delivery companies like Federal Express and TNT of Australia, have already expressed interest. A tour company hopes to fly passengers from downtown Washington to a nearby (though not yet built) theme park in a Pan Atlantic airship. A Vancouver mining firm has told Ferguson that his airship might make it economical to harvest small mines that have gone untapped because of high costs and environmental impacts of laying down roads. The U.S. military also believes the airships could be used to mobilize troops and supplies quickly.

In what is perhaps the most compelling evidence of renewed interest in lighter-than-air ships, the German Zeppelin company is now back in business after lofting a 240-foot-long airship this April-its first since the 1937 crash. Called Zeppelin NT (New Technology) the airship may soon see a 360-foot-long successor that could ferry 84 passengers.