A century ago, airships were a hot trend in the fast-growing aerospace industry. The future looked bright, until theHindenburgdisaster in 1937. Today, a new generation of airships that claim to be the greenest aircraft in the sky may transform 21st century aviation, especially for cargo and surveillance applications.

For instance, E-Green Technologies Inc. recently completed an inflation test of theBullet 580, the world’s largest airship. Using a nontraditional design, the company plans to fly the 235-foot-long, 65-foot-diameter vehicle by the end of the year.

“Airships offer cost-efficient operations vs. fixed-wing aircraft, and post great potential for vast cargo capacity, heavy lift, and the ability to take off and land vertically with . . . great maneuverability,” claims Michael Lawson, chairman and CEO of E-Green Technologies, which holds 18 patents on airship technology.

TheBullet 580uses four engines that are powered by algae-produced bio-diesel fuel. And, a water condensate recovery system reduces the need for helium replenishment.

“Airships have undergone surprisingly little evolution throughout their more than 150-year history,” Lawson points out. “Our airships are radically different designs that move beyond the performance limitations of traditional blimps or zeppelins by combining advanced technology with simple construction.”

Major aerospace companies, such as Boeing, Lockheed Martin and Northrop Grumman, also see the green benefits of airships. Engineers at Boeing Advanced Rotorcraft Systems are developing a heavy-lift rotorcraft for SkyHook International Inc. TheSkyHook JHL-40will be capable of lifting a 40-ton sling load in remote locations and transporting it up to 200 miles without refueling. It features a neutrally-buoyant, helium-filled envelope, with lift provided by four rotors.

Lockheed Martin engineers have created an unmanned High Altitude Airship for round-the-clock surveillance applications at altitudes above 60,000 feet. It features state-of-the-art technology, such as high-strength fabrics to minimize hull weight, thin-film solar arrays for regenerative power supply and lightweight propulsion units.

Northrop Grumman is currently developing a new hybrid airship weapons system for the U.S. Army. The unmanned Long Endurance Multi-Intelligence Vehicle (LEMV) will operate at altitudes of 20,000 feet for a three-week period.