Dirigibles: Bobbing Along Toward a Comeback

The Aeroscraft actually aloft Aeros

A class of aircraft is rising from the near-dead. The Aeroscraft ML866, which entered production in early September, is poised to be the world's largest aircraft — and it's a dirigible.

If the term is unfamiliar, it's probably because many people incorrectly refer to all dirigibles as blimps. It also could be because dirigibles all but disappeared after 1937, when the Hindenburg caught fire and crashed in New Jersey, killing 36 people. 

May 15, 1936: The Hindenburg rests in Frankfurt after completing a record flight of 48 hours in the air, May 15, 1936.

Dirigibles, or airships, are any powered, steerable, lighter-than-air aircraft. They achieve lift via inflation with gases that are more buoyant than air, and they come in three types: 

1. The blimp, which has no internal structure and maintains its shape only through inflation (like a balloon, but not a hot air balloon, which you can't steer.

2. The semi-rigid airship, which maintains its shape only through inflation but has some internal structure to help balance loads and aid in maneuvering.

3. The rigid airship, which has a complete internal framework that keeps it structured whether inflated with gas or not.

Aeroscraft is a rigid airship. So was the Hindenburg.

The Hindenburg's downfall was its lifting gas (and an apparent leak in the system). It used hydrogen, which is extremely flammable. Today's dirigibles use helium, which is inert. Helium is heavier than hydrogen, so it doesn't create as much lift, but it also won't ignite.

For the last 60 years or so, airships have mainly served as advertising vehicles, like the Goodyear Blimp that flies over sports stadiums. A handful of companies with dirigibles in various stages of development, including Aeros (the company behind Aeroscraft), Hybrid Air Vehicles and Altran, may get airships back in the business of actual air travel. John Kiehle, the director of communications for Aeros, estimates Aeroscraft will be doing cargo runs within five years.

Not passenger travel, though. At least not yet. Aeros does have distant dreams of floating cruise ships. But right now, according to Kiehle, the plan focuses on cargo.

"Today the logistics world has a large gap between air and the other modes between time vs. cost (land or sea, often both)," says Kiehle via email. "[That's] a gap the Aeroscraft is poised to fill as a new speed and cost intermediary alternative between current sealift and airlift."

The Aeroscraft in production

With a maximum payload of 73 tons (66 metric tons), the Aeroscraft ML866 can't beat the largest airplanes on payload weight. The biggest cargo plane, the Antonov An-225, carries 275 tons (250 metric tons). But it beats every plane on cargo length. Commercial turbine blades, for instance, would be no problem for the dirigible.

The ML866 measures 555 feet (169 meters) long and 120 feet (36 meters) tall, and it has a 177-foot (54-meter) wingspan. That's slightly wider and about 200 feet (60 meters) longer than an American football field, including the end zones.

It's also 300 feet (90 meters) longer than the largest Boeing model, the 747-8, and 250 feet (76 meters) longer than the Airlander 10, a hybrid airship that flew briefly in 2012 and is currently considered the world's longest aircraft.

Aeroscraft's other claim to fame is a unique buoyancy-control technology. Most airships need to carry and deploy external ballast, like sandbags or water containers, to hold them down for ground operations. Aeroscraft stays grounded on its own.

In this rendering, the Aeroscraft extends its landing cushions for a landing.

"People have been trying to figure out how to make airships into efficient and economical cargo airships for many years," says Kiehle. "However, one of the major historical problems has to do with an airship's arrival at destination. How do you remove a payload from a helium-filled aircraft and keep the vehicle grounded without first weighing it down with compensating weight, like lead or sandbags?"

The Aeroscraft system compresses the ship's helium gas, which both reduces the helium's buoyancy and creates a vacuum in the gas enclosures that pulls in regular air — or environmental ballast, as Aeros calls it. The combined effect is to make the ship heavier than air, so it stays grounded without external weights. Aeros compares this functionality to the buoyancy-control systems in submarines.

Aeroscraft will fly considerably lower than an airplane, with a maximum altitude of 12,000 feet (3,700 meters). It will also fly a lot slower. Its cruising speed is 100 knots (115 mph, 185 kph), compared to 569 knots (655 mph, 1,054 kph) for the 747-8. But speed is not its thing. What the airship offers, besides a whole lot of space, is flexibility.

Aeroscraft won't just deliver cargo. It will deliver cargo to areas that airplanes can't access, making it a possible go-to for emergency relief and military operations. Features like vertical takeoff and landing (like a helicopter), variable buoyancy control and special suction-equipped landing pads mean it doesn't need a runway, a big ground crew or any other special infrastructure in place for its operations.

It also uses less fuel than an airplane and runs on regular diesel fuel, which is cheaper and more widely available than jet fuel.

Assuming success with the ML866, the company plans an Aeroscraft model with three times the payload.