What may look like an ordinary blimp is actually one of the largest and most unusual aircraft in the world.
Designed and built by the British company Hybrid Air Vehicles, the Airlander 10 is a hybrid airship that gets its lift both from the helium gas it carries and the shape of its hull.
Instead of a circular cross-section like a typical blimp, the Airlander has a flattened elliptical shape that looks like two blimps stuck together. The design, while rather curious -- it does resemble a flying butt -- is completely deliberate. When its four engines are driving the Airlander's forward, its hull acts as a giant wing, giving it 40 percent of its lift. In other words, it flies like a blimp, a helicopter and a plane.
The Airlander was built in Lakehurst, New Jersey (the site of the 1937 Hindenburg crash), and took its first flight there on August 7, 2012. Then called the HAV 304, the airship was meant to serve as a reconnaissance, surveillance and intelligence vehicle for the US Army.
But its military life ended abruptly just six months later when the Army canceled its Long Endurance Multi-intelligence Vehicle program following budget sequestration from the Budget Control Act of 2011.
The US government had spent $300 million on the project, but following the cancellation, Hybrid bought the HAV 304 back from the Feds for $300,001.
In December, 2013 the company shipped it home to England (it didn't fly across the Atlantic, sadly) where it reassembled the airship for civilian use and gave it its new name.
Hybrid is now modifying and promoting the Airlander for a variety of uses including freight, advertising, surveillance, communications and luxury passenger transport. Since it doesn't need a runway, it can carry heavy loads to remote areas where an airplane couldn't land. Or closer to home, it could monitor large public events for safety while broadcasting Wi-Fi and cellular service to the data-starved participants below. For me, the idea of sailing leisurely above the Earth with the view of a lifetime sounds the most appealing.
At 302 feet long the Airlander is 64 feet (19.5 meters) longer than the largest commercial aircraft, the Airbus A380. Its other dimensions (143 feet wide and 85 feet high, or 43.6 by 25.9 meters) are just as impressive, but it still fits comfortably in its hangar.
Hybrid Air Vehicles is based in Cardington, a village in Bedfordshire 46 miles north of London. On the site of a former Royal Air Force base are two massive airship sheds (or hangars) that were originally built for the Royal Navy's rigid airship program. Hangar One (left), first constructed in 1915 and later expanded in 1924 and 1926, now houses the Airlander 10 and the Hybrid's offices. Hangar Two (right), completed in 1928, is now a giant sound stage. It's been used to shoot many films, including "Rogue One," "Inception" and "Batman Begins."
After languishing empty for several years, Hangar One had begun to deteriorate by 2007, at which point English Heritage (now Historic England) declared it to be at risk of being unusable. Now a Grade II listed building, the UK's version of a historic landmark, it was completely refurbished between 2012 and 2015.
Each hangar is 812 feet long, 180 feet wide and 157 feet high (247.5 by 54.9 by 47.9 meters), making them the largest such hangars in Britain. They're so colossal that I was able to see them while approaching on the train from about 5 miles away.
Cardington sits in a broad, shallow valley that protects it from strong winds. Gusty conditions are the last thing you want when flying an airship.
An early Hangar One resident was the R101, a rigid airship built by the British government in 1929. Like the German zeppelins of the same era, it was developed for long-range passenger transport at a time when airplanes could barely cross the ocean. It could carry 100 passengers in ocean liner-like accommodations that included sleeping cabins, a dining room, a lounge and a smoking room.
Though luxury air travel across the far-flung British Empire was the promise, the R101 was plagued by an overly complicated design that made it too heavy and barely airworthy. After just a few test flights, it crashed in northern France on October 5, 1930, during its first passenger flight to India. A fire from the flammable hydrogen gas killed 48 of the 54 people aboard, ending Britain's rigid airship program.
You have to stand alongside the Airlander to really appreciate its scale. Its envelope has a volume of 1.34 million cubic feet (37,945 cubic meters). Like other non-rigid airships it has no supporting internal structure, meaning that it will lose its shape when deflated.
The yellow strip stretching across the floor of the hangar hides a helium line connected to the nine separate helium compartments.
Multiple compartments mean that less helium will escape if one compartment is punctured. Also, because the air pressure inside the hull is comparable to the pressure outside, Hybrid says the Airlander's helium would leak slowly enough to not put the ship in immediate danger.
Like other non-rigid airships, the Airlander uses air-filled ballonets inside the envelope to help control lift and maintain its internal shape and pressure. When the airship takes off and climbs, air is let out of the four ballonets to increase lift. To descend and land, air is sucked into the ballonets, which adds weight and reduces the volume of the helium compartments.
Technicians can access the ballonets for inspection via hatches on the bottom of the Airlander when the airship is on the ground.
When tethered to the ground, the Airlander rests on two air-filled skids that run almost the full length of either side of the hull. They're "sucked in" during flight for a smoother aerodynamic profile.
The skids also let the Airlander land on water or marshland and they act as a hovercraft of sorts when the Airlander is on the ground. If it were moored outside, the Airlander can slide on the skids as the wind direction changes.
Since it's filled with helium, you have to keep the Airlander tied down or it will float away. Like all airships, the Airlander is attached to a mooring mast at its nose when it's on the ground. The mast is on the back of a trailer that can be towed anywhere.
Other lines on the hull are attached to large weights resting on the hangar floor.
The lines are attached to several points on the Airlander's skin. No thicker than a few sheets of paper, the skin is made from a carbon weave fiber that includes Vectran, Tedlar and Mylar. Tedlar provides weather-proofing on the hull's exterior and Mylar forms the gas barrier. Technicians regularly check the fabric for leaks. By itself, the skin weighs 6 tons (5.4 tonnes).
Though about 22 tons of materials make up the Airlander, when inflated with lighter-than-air helium, the entire ship can weigh as little as 1,300 pounds (590 kg).
Valves track the pressure inside the various helium compartments, ballonets and skids.
The control cabin, which is made of carbon composite materials, contains the cockpit, room for freight and a passenger compartment. When configured only for passengers, the Airlander can carry up to 48 people. The Airlander requires a minimum crew of two.
The Airlander can carry up to 11 tons of cargo either in the control cabin or attached directly to the hull.
Though Hybrid has no customers for the Airlander yet, the company has talked with several potential clients. The Swedish government, for instance, is considering using the airship to deliver wind turbine pylons to remote locations.
The Airlander has four 325-horsepower V8 engines. Two are at the aft end of the airship with the others positioned on either side hull. Cameras trained on each engine allow the crew to monitor them from the control cabin.
The engines run on jet fuel, which is stored in two tanks on the Airlander's underside. They burn 35 gallons (132 liters) of fuel per hour.
Though the engines deliver a top 80 knots (92 mph), the Airlander's average speed is 70 knots (81 mph). The airship's loitering speed, or the slowest speed the engines can manage (with the ship basically hovering), is 20 knots (23 mph).
With a full passenger load and a full tank of gas the Airlander can fly 1,864 miles (3,000 km). It can stay aloft for nine days at a time with a crew, but keep in mind there's no bathroom. Unmanned it could stay aloft for three weeks.
On the aft end of the hull are four fins, which hold the control surfaces for turning the Airlander. Covered in polyurethane, the fins were heat-welded onto the skin.
Vanes on the four engines can be adjusted to move the Airlander up and down. The Airlander can fly as high as 16,000 feet (about 5 km), though the control cabin is not pressurized.
Climb up the stairway to the hanger's catwalks for the best view of the Airlander.
The, er, posterior view.
The catwalk also delivers an amazing view down the full length of the hangar. The day we visited, there was gorgeous light coming through the windows that illuminated the maze of girders.
The bow of the Airlander almost touches a fabric barrier that cuts off the other end of the hangar.
Hybrid's Mission Control Bus follows the Airlander when it flies.
On the bus are several stations where technicians can monitor the Airlander's condition and performance.
To move the Airlander out of the hangar, workers must first open the massive doors that entirely cover the end of the hangar.
Each door slides opens on rails set into the grass.
Replenishment helium is stored in giant tanks outside the hanger. These aren't the kind you'd rent to blow up balloons at your kid's birthday party. Hybrid says that only 10 percent of the Airlander's helium capacity is lost during a typical year of operation.
The Airlander made its first flight from Cardington on August 17, 2016. On its second flight a week later, the airship nosedived just before landing after the mooring line became entangled with electrical wires. Though no one was injured, the nose hit the ground hard, damaging the cockpit.
Since that time, Hybrid has installed a new Auxiliary Landing System (ALS) to minimize damage from any similar future accident. The ALS consists of two pressurized air cushions on either side of the control cabin that will hit the ground before other parts of the Airlander. Like the skids, the ALS will retract during flight.
After additional testing, the Airlander will take to the skies for another flight soon. Hybrid also is designing an even larger ship, the Airlander 50, but hasn't set a date to start construction. Hybrid says that each Airlander costs about $40 million to build, but the amount will depend on specifications.