The Mechanics Behind Blimps

Chances are, you've witnessed a Goodyear blimp delivering live TV coverage at major sporting events like football games or golf tournaments. These remarkable vessels fall under the category of lighter-than-air (LTA) crafts known as airships. Similar to hot air balloons, blimps rely on gas for lift. However, unlike balloons, blimps can propel themselves forward, much like airplanes. They possess the ability to hover akin to helicopters, navigate through diverse weather conditions, and remain airborne for extended periods. In this Mytour feature, we delve into the workings of these captivating vehicles.

Inside a Blimp

In contrast to a balloon, a blimp possesses a defined shape and structural design that allow it to fly and navigate effectively. The following components make this possible:

Each of these components will be explored in detail in the sections that follow.

Envelope

The envelope serves as the expansive container for the helium gas. Typically shaped like a cigar to enhance aerodynamics, it is crafted from a robust, airtight, and lightweight material (polyester composites), resembling the fabric used in space suits. Notably, many envelopes are produced by ILC Dover Corporation, the same company responsible for manufacturing spacesuits for NASA.

Depending on the specific blimp, the envelopes can accommodate between 67,000 and 250,000 cubic feet (1,900 to 7,093 cubic meters) of helium. The internal pressure is maintained at a low level, around 0.07 pounds per square inch (0.005 ATM).

Nose Cone Battens

The nose cone battens are structural supports extending from the blimp's tip. They reinforce the front section to prevent damage during mooring to the mooring mast. Additionally, they provide an aerodynamic contour to the nose and prevent it from collapsing as the blimp moves forward. The mooring hooks are also situated in the nose area.

Ballonets

Ballonets are air-filled compartments situated within the envelope. Each blimp features two ballonets, one at the front and one at the rear. Functioning similarly to the ballast tanks in a submarine, these ballonets are filled or emptied with air to regulate the blimp's ascent or descent, as air is denser than helium. They also play a crucial role in maintaining the blimp's trim, ensuring it remains level.

Catenary Curtain and Suspension Cables

Inside the envelope, two catenary curtains run along the length of the blimp. Constructed from fabric and integrated into the envelope, these curtains are connected to the gondola via suspension cables. They provide structural support, help maintain the envelope's shape, and secure the gondola in place.

Flight Control Surfaces

The flight control surfaces are rigid, adjustable components mounted on the blimp's tail. These include the rudder and elevators. The rudder directs the blimp to the left or right (yaw axis), while the elevators manage the angle of climb or descent (pitch axis). Pilots manipulate these surfaces during flight, and they can be arranged in either a "+" or "x" configuration.

Engines

The blimp's two engines generate the required thrust for forward motion. These engines are turbo-propeller airplane engines powered by gasoline fuel and utilize air cooling. Depending on the blimp model, they can produce several hundred horsepower. Positioned on either side of the gondola, these engines enable blimps to travel at speeds ranging from 30 to 70 mph (48 to 113 kph).

Air Scoops

The air scoops channel exhaust air from the propellers into the ballonets. This mechanism allows pilots to inflate the ballonets mid-flight. When the engines are inactive, electric fans take over the task of moving air into the ballonets.

Air Valves

Pilots need the ability to both release and add air to the ballonets. This is managed by air valves positioned on each ballonet, with a total of four valves — two at the front and two at the rear.

Helium Valve

The helium pressure within the envelope is regulated by adjusting the air volume in the ballonets. Typically, blimp pilots do not need to add or remove helium from the envelope. However, a helium valve is installed on the envelope to release helium if the pressure surpasses its safe threshold. This valve can be operated either manually or automatically.

Gondola

The gondola is the enclosed compartment that accommodates passengers and crew. Depending on the blimp model, it can seat two pilots and up to 12 crew members (for instance, Goodyear's Eagle and Stars & Stripes each carry two pilots and six passengers). Some gondolas are equipped with specialized gear, such as cameras, mounted externally.

The control panels utilized by the pilots include the following components:

Blimp pilots hold FAA certification for operating lighter-than-air (LTA) vehicles. Goodyear's pilots complete an extensive training program before earning FAA certification. Beyond flying, these pilots also perform roles as ground-support crew, such as electronics technicians, mechanics, riggers, and administrative staff. A dedicated ground crew accompanies the blimp, equipped with support vehicles like a bus for administrative tasks, a tractor-trailer serving as an electrical/mechanical workshop, and a van functioning as the command and utility vehicle.

Night Signs

Certain blimps, like those operated by Goodyear, feature electric lighting systems for nighttime advertising. The Goodyear blimp utilizes a matrix of red, green, and blue light-emitting diodes (LEDs) for its night signs. The LED intensities can be adjusted to produce a range of colors. Messages are programmed using a compact laptop computer carried onboard.

Now that we've explored all the components of a blimp, let's delve into how it achieves flight!

How a Blimp Flies

Airships are classified as lighter-than-air (LTA) craft because they utilize gases lighter than air to generate lift. Helium is the most commonly used gas today, with a lifting capacity of 0.064 lb/ft (1.02 kg/m). In the early days of airships, hydrogen was frequently used due to its lighter weight (0.070 lb/ft or 1.1 kg/m) and lower cost. However, the Hindenburg disaster led to the discontinuation of hydrogen in airships because of its high flammability. Helium, in contrast, is non-flammable.

Although these lifting capacities may appear modest, airships contain vast volumes of gas—up to hundreds of thousands of cubic feet (thousands of cubic meters). This immense lifting power enables airships to transport heavy loads with ease.

A blimp or airship manages its buoyancy similarly to how a submarine operates in water. The ballonets function like ballast tanks, holding "heavy" air. During takeoff, the pilot releases air from the ballonets via air valves. The helium creates positive buoyancy, causing the blimp to ascend. The pilot adjusts the engine throttle and elevators to align the blimp with the wind. The blimp's conical shape also contributes to generating lift.

As the blimp ascends, the external air pressure drops, causing the helium inside the envelope to expand. Pilots compensate by pumping air into the ballonets to maintain pressure equilibrium with the helium. Adding air increases the blimp's weight, so pilots must balance air and helium pressures to achieve neutral buoyancy for steady cruising. To keep the blimp level, air pressure is adjusted between the front and rear ballonets. Blimps typically cruise at altitudes ranging from 1,000 to 7,000 feet (305 to 2,135 meters). The engines provide forward and reverse thrust, while the rudder is used for steering.

To descend, pilots fill the ballonets with air, increasing the blimp's density and making it negatively buoyant. The elevators are adjusted to control the descent angle.

When not in operation, blimps are secured to a mooring mast, either outdoors or inside a hangar. To move the blimp in or out of its hangar, a tractor pulls the mooring mast with the blimp attached.

Uses of Blimps and Airships

Since gas generates lift in an airship or blimp, unlike the wing-and-engine mechanism of airplanes, airships can fly and hover without consuming fuel or energy. Additionally, airships can remain airborne for extended periods, ranging from hours to days—far longer than airplanes or helicopters. These characteristics make blimps perfect for applications such as broadcasting sporting events, advertising, and certain research activities, like whale tracking.

Recently, there has been a resurgence of interest in employing rigid airships for lifting and transporting heavy cargo, such as ships, tanks, and oil rigs, for both military and civilian purposes. Modern airships, like the Zeppelin NT and CargoLifter, utilize lightweight carbon-composite frames, enabling them to be massive, lightweight, and structurally robust. Beyond cargo transport, airships may also see a revival in tourism. As a result, the sight of a large airship gliding across the sky could become more frequent in the near future.

Blimp History

In 1783, French brothers Jacques Etienne and Joseph Michel Montgolfier created the hot-air balloon, achieving an altitude of 6,000 feet (1,800 meters). That same year, French physicist Jean Pilatre de Rozier completed the first manned balloon flight. While balloons could reach great heights, they lacked self-propulsion and were dependent on wind currents. The balloon's shape was determined by the pressure of the air or gas (such as hydrogen or helium) inside it.

In 1852, Henri Giffard constructed the first powered airship, featuring a 143-foot (44-meter) long, cigar-shaped gas bag equipped with a propeller driven by a 3-horsepower (2.2-kW) steam engine. Later, in 1900, Count Ferdinand von Zeppelin of Germany introduced the first rigid airship.

The rigid airship featured a metal framework—420 feet (123 meters) long and 28 feet (12 meters) in diameter—housing hydrogen-filled rubber bags. The initial Zeppelin model included tail fins, rudders, and was powered by internal combustion engines. It transported five individuals to an altitude of 1,300 feet (396 meters) and covered a distance of 3.75 miles (6 kilometers). Numerous Zeppelin models were developed in the early 20th century, serving both military and civilian roles, including transatlantic voyages. The most renowned Zeppelin, the Hindenburg, tragically caught fire in 1937 during its landing in Lakehurst, New Jersey. For more details, see Fall of the Hindenburg.

In 1925, Goodyear Tire & Rubber Company began producing blimp-style airships. These aircraft were utilized for advertising and military operations, including surveillance and anti-submarine warfare, during World War II. By 1962, the U.S. military discontinued the use of blimps. Today, blimps are primarily employed for advertising, TV coverage, tourism, and certain research applications. However, airships are experiencing a resurgence.