Blimps and zeppelins plied the skies in the early part of the 20th Century, carrying passengers and cargo and even serving as military aircraft during the World Wars. But it didn't take long for airplanes to replace dirigibles for commercial and military flight and by the middle of the 20th Century, airships were mostly use for advertising, sightseeing and surveillance.
But blimps may be back. Montabello, Calif.-based Aeros is working on a rigid airship that can fly like a plane and float like a balloon. If realized, the 500-foot-long Aeroscraft would greatly alter the way cargo is shipped. The craft is designed to take off vertically and cruise at up to 130 miles an hour at an altitude of 12,000 feet. It will be able to travel thousands of miles on a single tank of fuel, carrying 66 tons of cargo -- that's three times the capacity of a C-130 and half that of the C-5, the largest military aircraft flown by the United States.
"This vehicle doesn't need infrastructure," Munir Tojo-Verge, the flight control systems engineer at Aeros, told Discovery News. "It could even land on water."
The Aeroscraft could serve both military and humanitarian efforts, delivering extremely heavy loads to areas without transportation infrastructure, such as roads, train tracks or airports.
Aeros recently tested a 230-foot-long prototype and has received $35 million from DARPA and NASA to get a full-sized version off the ground.
The Aeroscraft has a rigid shell made of a lightweight, carbon-fiber composite and has special honeycomb-like chambers designed to hold helium. The helium is housed separately in compression tanks. To fly, the compressed helium is released into the chambers. To sink, the helium is pumped back into the tanks and replaced with air. That eliminates the need for ballast. And because helium is nonflammable, there is no risk of a Hindenburg-like explosion.
The gas pressure inside isn't much different from the outside air, so even if one were to put a hole in the skin of the Aeroscraft, the gas wouldn't escape very fast. Blimps, by contrast, are under high pressure, so they deflate much faster.
A set of turboprop engines like those on a plane provide thrust, combined with another type that Tojo-Verge said he could not discuss. The airship's arrowhead shape keeps it stable a higher speeds and helps give it lift.
All this makes the Aeroscraft much different from blimps, which are basically flexible, helium-filled balloons outfitted with propellers to move and steer, or zeppelins, which have rigid frames containing lots of small, helium-filled balloons called ballonets. Both types of airship need ballast and are difficult to maneuver in rough weather. The zeppelins of the 1930s also needed ground crews with ropes to wrangle the craft to the ground. The Aeroscraft won't require that.
For cost and capability, the Aeroscraft compares well with helicopters. The biggest helicopter available now is the Sikorsky Skycrane, which travels at 126 mph and is able to carry 10 tons. These copters are often used in rescue missions and to carry heavy equipment. But they cost a lot to operate and their range is only 230 miles with a maximum load of fuel. The Aeroscraft will have a similar speed, carry much more cargo and be able to travel much farther.
While the Aeroscraft is technologically advanced, the next step is making airship transport a viable business, which may be harder than it sounds. Jose Holguin-Veras, director of the Center for Infrastructure, Transportation, and the Environment at Rensselaer Polytechnic Institute, said it would take a lot of airships to make a dent in the service area they aim to fulfill and he's skeptical that the market will be large enough to give way to that many vehicles.