SAN FRANCISCO — Nowadays blimps are used mainly as advertising gimmicks meant to make people look up at the sky. But in a technological twist these slow-moving airships may be making a comeback as the world rediscovers their usefulness for staring back down at earth.

More than 70 years after the Hindenburg disaster doomed the first generation of hydrogen-filled airships, governments around the world are using helium-filled airships as surveillance platforms to track enemies or spot smugglers.

At the same time, commercial and university engineers are testing the potential for airships to serve as floating relay stations for broadband or cellular communications.

As one example in the military realm, the government of Thailand recently ordered an airship to keep watch over its southern provinces where a Muslim insurgency has been blamed for more than 3,300 deaths. The $9.7 million contract with the U.S. firm, Aria International, is an example of how little it can cost a nation to create its own aerial surveillance capability.

“They're a poor man's satellite,” said Jerry Vorachek, a retired engineer who used to work for Goodyear Aerospace, in Akron, Ohio, home base of the famous Goodyear advertising blimps. Engineers prefer the term airship to describe the entire genre of lighter-than-air craft and reserve blimp to describe a vessel with no internal support that would deflate like a balloon if emptied of gas.

Vorachek said no matter how airships are constructed, they make ideal observation platforms because they move slowly and can linger longer than competing surveillance aircraft, such as unmanned aerial vehicles. They are also cheaper to build and operate than any competing surveillance option, he said.

In recent years, Vorachek has served on the Council of Legends, a group of retired Goodyear engineers who have advised the aerospace contractor, Lockheed-Martin Corp., in its efforts to build the world's most ambitious airship for the U.S. military.

Lockheed-Martin, which now owns the former Goodyear Aerospace facilities in Akron, is leading a $400 million Pentagon program to develop a new generation of unmanned airships that would float at altitudes above 60,000 feet and stay aloft for 10 years, offering continuous surveillance of areas up to 600-miles in diameter. According to Lockheed Martin, this proposed High Altitude Airship “gives users capabilities on par with satellites at a fraction of the cost.”

But far more modest blimps, to use the popular term, have found military uses in at least 20 countries, including Britain, France, Ireland, Pakistan and Poland, according to a report in the the Economist magazine. The wars in Iraq and Afghanistan, in particular, have helped spur the deployment of lighter-than-air surveillance systems.

“It's all about having the high ground,” said Eric Brothers, a board member of the Lighter than Air Society, an enthusiast group based in Akron that has about 700 members worldwide.

Brothers says that while military surveillance remains the predominant use for airships, there have been periodic revivals of interest in their commercial applications as well. After the 1973 Arab oil embargo, for instance, airships were briefly studied as transport vessels, although the idea was never taken very far.

Brothers said airships are now being considered as aerial platforms for propagating wireless or broadband signals. In the developed world, wireless signals are broadcast from towers erected on buildings, but in developing nations small fleets of airships might be an economical solution, he said. Academic scientists in Egypt have studied that option for their country. In the United Kingdom, the University of York has considered the use of airships as high-altitude platforms for the dissemination of broadband Internet.

Brothers said advances in solar technology now make it possible for airships to generate electricity without the need to carry and replenish fuels, which enhances their commercial potential by giving them the power to serve as floating broadcast stations. Remote control capabilities also make it possible to envision positioning airships at high altitudes and leaving them on station for years.

But much as he would like to see a revival of lighter-than-air flight, Brothers does not downplay the difficulty of going from cool ideas to commercial deployment.

“The trouble is no one's really built airships in large numbers since the 1930s,” he said, adding. “That's why the military interest makes the difference. It's driving the research and development.”

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