You're having a dream where you're floating noiselessly over a landscape looking down. For most of us, it's just a dream, but for a lucky few who have flown in a lighter-than-air aircraft, it's a reality.
There are multiple types of lighter-than-air aircraft:
* Airship - any powered, steerable aircraft that it is inflated with a gas that is lighter than air
* Dirigible - synonymous with an airship, it is any lighter-than-air craft that is powered and steerable; from the French verb diriger, "to steer"
* Blimp - a powered, steerable, lighter-than-air vehicle whose shape is maintained by the pressure of the gases within its envelope
* Rigid Airship - has a framework surrounding one or more individual gas cells, and the framework determines its shape
* Zeppelin - a rigid airship that is manufactured by the Luftschiffbau Zeppelin company of Germany which was founded by Count Ferdinand von Zeppelin who is considered the father of the rigid airship
* Semi-Rigid Airship - like a blimp, it maintains its aerodynamic shape from internal gas pressure, but it has a partial rigid frame which supports and distributes loads
* Hybrid Airship - a powered aircraft that obtains some of its lift as a lighter-than-air (LTA) airship and some from aerodynamic lift as a heavier-than-air aerodyne
People are most familiar with airships from the Goodyear Blimps which hover over sporting events and air shows. The Goodyear company began using blimps to advertise their brand back in 1925. From the 1920s through the 1950s, the U.S. Navy used blimps for anti-submarine and reconnaissance purposes.
People are also familiar with airships from the Hindenburg Disaster.
On May 6, 1937, while landing at Lakehurst, New Jersey, the Zeppelin exploded killing 13 passengers, 22 crewmen, and one worker on the ground. Hindenburg was designated "LZ-129" for "Luftschiff Zeppelin" and she was the 129th ship designed by the firm.
Hindenburg was only the last of four high-profile airship accidents. In 1930, the British airship R101 crashed and burned in France, and the the U.S. Navy lost its airships USS Akron and USS Macon in 1933 and 1935, respectively.
The mast atop the iconic Empire State Building in New York City was originally intended to be a dirigible mast, in anticipation of passenger airship service.
Zeppelins are still flying today. Goodyear's new airship isn't a blimp, it's a Zeppelin NT, which stands for "new technology".
To provide buoyancy, a lifting gas must be less dense than the air surrounding it. When heated, air expands, lowering its density. The Chinese have flown hot air lanterns since ancient times. There was renewed interest in hot air ballooning during the latter half of the 20th century.
Hydrogen is the lightest of all gases. Before the Hindenburg Disaster, hydrogen was used in both balloons and airships, but due to its flammability, it has been phased out.
Coal gas is a mix of methane and other gases, and it has about half the lifting power of hydrogen. During the late nineteenth and early twentieth centuries, coal gas was commonly made in municipal gas works.
Helium is the only lifting gas which is both non-flammable and non-toxic. It has 92 percent of the lifting power of hydrogen. Quantities of helium weren't discovered until the early twentieth century, and for many years, only the U.S. had sufficient quantities to use in airships. Almost all gas balloons and airships now use helium.
Only a few companies are currently working on building airships.
Worldwide Aeros Corp. is hoping its new Aeroscraft will bring major changes to the freight shipping industry. Its COSH (Control of Static Heaviness) system rapidly compresses helium contained in the ship, making the airship heavier than air. This will allow the ship to land within a much smaller area. Aeroscraft hope to create prototypes capable of hauling 66 tons and 250 tons.
The Phoenix, officially known as an "ultra-long endurance autonomous aircraft" was developed by scientists at the University of the Highlands and Islands Perth College in Scotland. The blimp-like aircraft is 15 meters long with a wingspan of 10.5 meters.
The Phoenix's fuselage contains helium, which allows it to ascend, and it contains an air bag that "inhales" and compresses air, allowing the craft to descend. Solar cells on its wings and tail charge the battery that powers the craft's valves and pumps.
Described as half heavier-than-air airplane, and half lighter-than-air balloon, the Phoenix had its first test flight in March 2019, when it flew 120 meters (394 feet). Its creators hope it can be used as a pseudo satellite, providing a cheaper alternative for telecommunication services. It could also be used to provide Wi-Fi coverage to remote areas.
The Hybrid Air Vehicles HAV 304 was originally built for the U.S. Army Long Endurance Multi-intelligence Vehicle (LEMV) program. When that program was canceled, the British firm purchased the HAV 304 back, and returned it to the UK where it was renamed the Airlander 10.
On August 17, 2016, the Airlander 10 had its first successful test flight outside the Cardington Hangars at RAF Cardington. Work on a production version has begun after the craft received approval from the UK's Civil Aviation Authority (CAA).
Airlander 10 has a 150-foot-long cabin with bedrooms for 19 passengers, and a common room with a bar and glass floors. The craft will be able to fly at 6,100 meters (16,000 feet).
Just this week, Arizona company World View Enterprises Inc. completed a 16-day test mission of its high-altitude, long-range surveillance balloons. Flying over the states of Nevada, Utah and southern Oregon, the unmanned balloons carried surveillance equipment capable of monitoring mines, pipelines, and other infrastructure.
The equipment can also see into your backyard, and that presents a problem for groups such as the American Civil Liberties Union and the Electronic Privacy Information Center.
The ACLU's senior policy analyst Jay Stanley was quoted in a Yahoo! Finance article: "There’s a very real potential here that these kinds of systems will lead to a pervasive aerial surveillance of cities where our every move will be tracked."