Editing Airship (section)

==Construction==
[[File:Usn-airships (cropped).jpg|thumb|U.S. Navy airships and balloons, 1931: in the background, ZR-3, in front of it, (l to r) J-3 or 4, K-1, ZMC-2, in front of them, [[Caquot kite balloon|"Caquot" observation balloon]], and in foreground free balloons used for training]]

===Envelope===
The envelope is the structure which contains the buoyant gas. Envelopes in the early 19th century were made from [[goldbeater's skin]], selected for its low weight, relatively high strength, and impermeability compared to paper or linen. By the 1920s, [[natural rubber]] treated with cotton became the predominant [[elastomer]] used in envelope construction. The natural rubber was succeeded by [[neoprene]] in the 1930s and [[Nylon]] and [[Polyethylene terephthalate|PET]] in the 1950s. A few [[metal-clad airship|airships have been metal-clad]].<ref>{{Cite book |last=Brooks |first=Peter |url=https://archive.org/details/zeppelin-rigid-airships-1893-1940_compress/page/93/mode/2up |title=Zeppelin: Rigid Airships, 1893-1940 |date=1992}}</ref> The most successful of which is the [[ZMC-2|Detroit ZMC-2]], which logged 2265 hours of flight time from 1929 to 1941 before being scrapped, as it was considered too small for operational use on anti-submarine patrols.<ref>[http://nasgi.org/zmc2.htm NAS Grosse Ile] {{Webarchive|url=https://web.archive.org/web/20110709085217/http://nasgi.org/zmc2.htm|date=2011-07-09}}, NASGIVM. 2006.</ref>

The problem of the exact determination of the pressure on an airship envelope is still problematic and has fascinated major scientists such as [[Theodor Von Karman]].<ref>{{Cite web|url=http://authors.library.caltech.edu/47901/1/19930094841.pdf|title=Von Karman, Theodor. "Calculation of pressure distribution on airship hulls." (1930).}}</ref>

The envelope may contain [[ballonets]] (see below), allowing adjustment of the density of the buoyant gas by adding or subtracting envelope volume.

===Ballonet===
{{Main|Ballonet}}
[[File:ballonet analogue.jpg|thumb|upright|The air-filled red balloon acts as a simple ballonet inside the outer balloon, which is filled with lifting gas.]]

A [[ballonet]] is an air bag inside the outer [[Aerostat|envelope]] of an airship which, when inflated, reduces the volume available for the lifting gas, making it more dense. Because air is also denser than the lifting gas, inflating the ballonet reduces the overall lift, while deflating it increases lift. In this way, the ballonet can be used to adjust the lift as required by controlling the buoyancy. By inflating or deflating ballonets strategically, the pilot can control the airship's altitude and attitude.

Ballonets may typically be used in [[Non-rigid airship|non-rigid]] or [[Semi-rigid airship|semi-rigid]] airships, commonly with multiple ballonets located both [[Bow (ship)|fore]] and [[Stern|aft]] to maintain balance and to control the [[Flight dynamics (aircraft)|pitch]] of the airship.

===Lifting gas===
{{Main|Lifting gas}}
[[Lifting gas]] is generally hydrogen, helium or hot air.

Hydrogen gives the highest lift {{convert|1.1|kg/m3|lb/ft3|abbr=on}} and is inexpensive and easily obtained, but is highly flammable and can detonate if mixed with air. Helium is completely non flammable, but gives lower performance-{{convert|1.02|kg/m3|lb/ft3|abbr=on}} and is a rare element<ref name=":1">{{Cite journal |last1=Wilkinson |first1=Stephen |last2=Gerth |first2=Florian |date=2024 |title=A Review of the Sustainability of Helium: An Assessment of Its Past, Present and a Zero-Carbon Future |journal=Regional Science and Environmental Economics |language=en |volume=1 |issue=1 |pages=78–103 |doi=10.3390/rsee1010006 |doi-access=free |issn=3042-4658}}</ref> and much more expensive.<ref>{{cite web |last=Freudenrich |first=Craig |title=How Blimps Work |url=https://science.howstuffworks.com/transport/flight/modern/blimp2.htm |website=[[HowStuffWorks]] |access-date=2023-10-18 }}</ref>

[[Thermal airship]]s use a heated lifting gas, usually air, in a fashion similar to [[hot air balloon]]s. The first to do so was flown in 1973 by the British company [[Cameron Balloons]].<ref>"Jane's All the World's Aircraft 1980–81", pp. 609–610</ref>

===Gondola===
[[File:Modern airship gondola.jpg|thumb|A gondola fitted with twin propellers]]

===Propulsion and control===
{{Update section|date=December 2019}}
Small airships carry their engine(s) in their gondola. Where there were multiple engines on larger airships, these were placed in separate nacelles, termed ''power cars'' or ''engine cars''.<ref name="Brew, 1998" >{{cite book
  |title=Sunbeam Aero-engines
  |last=Brew |first=Alec
  |year=1998
  |publisher=Airlife
  |isbn=1-84037-023-8
  |pages=41, 43, 92
}}</ref> To allow asymmetric thrust to be applied for maneuvering, these power cars were mounted towards the sides of the envelope, away from the centre line gondola. This also raised them above the ground, reducing the risk of a propeller strike when landing. Widely spaced power cars were also termed ''wing cars'', from the use of "wing" to mean being on the side of something, as in a theater, rather than the [[wing|aerodynamic device]].<ref name="Brew, 1998" /> These engine cars carried a crew during flight who maintained the engines as needed, but who also worked the engine controls, throttle etc., mounted directly on the engine. Instructions were relayed to them from the pilot's station by a [[engine order telegraph|telegraph system]], as on a ship.<ref name="Brew, 1998" />

If fuel is burnt for propulsion, then progressive reduction in the airship's overall weight occurs. In hydrogen airships, this is usually dealt with by simply venting cheap hydrogen lifting gas. In helium airships water is often condensed from the exhaust and stored as ballast.<ref>{{cite web | url=https://www.airships.net/helium-hydrogen-airships/ | title=Hydrogen and Helium in Airship Operations }}</ref>

===Fins and rudders===
To control the airship's direction and stability, it is equipped with fins and rudders. Fins are typically located on the tail section and provide stability and resistance to rolling. Rudders are movable surfaces on the tail that allow the pilot to steer the airship left or right.

===Empennage===
{{Main|Empennage}}
The [[empennage]] refers to the tail section of the airship, which includes the fins, rudders, and other aerodynamic surfaces. It plays a crucial role in maintaining stability and controlling the airship's attitude.

===Fuel and power systems===
Airships require a source of power to operate their propulsion systems. This includes engines, generators, or batteries, depending on the type of airship and its design. Fuel tanks or batteries are typically located within the envelope or gondola.

===Navigation and communication equipment===
To navigate safely and communicate with ground control or other aircraft, airships are equipped with a range of instruments, including GPS systems, radios, radar, and navigation lights.

===Landing gear===
Some airships have landing gear that allows them to land on runways or other surfaces. This landing gear may include wheels, skids, or landing pads.