Aerostat

Aerostats, also called Jogayen in Umbrak, are lighter-than-air aircraft used for both civilian and military applications across Duurn. Originally, lifting gases such as hydrogen and helium were used for buoyancy, but developments in materials and energy technologies and the industrialization of mechanurgy has allowed for the use of low-pressure chambers that have revolutionized aerostats. Many modern aerostats also utilize rotors for takeoff, landing, and fine course-adjustment. Both common names come from the use of aerostatic buoyancy, where the average density of the craft is less than the density of the air around it, causing it to rise through the air without the use of aerodynamic forces. The addition of rotors and even wings in modern aerostats technically makes them a hybrid between aerostatic and aerodynamic craft, but most of the lifting force still comes from aerostatic buoyancy.   There are, however, vehicles that predominantly use aerodynamic lift. Autogyros are widely used in conjunction with aerostats or for shorter journeys with lighter loads. Additionally, early models of fixed-wing vehicles called aerodynes are showing a great deal of promise.

Design

Buoyancy

Originally, aerostats used balloons of lighter-than-air gases, called envelopes, for lift. Most used fabric coated with something to make it airtight, such as rubber. Ballonets were placed inside the envelope. The ballonets would be inflated or deflated to adjust the density of the contents of the envelope, in order to raise or lower the craft. This style of aerostat was widely used for several centuries and still sees some use in civilian applications, but this style of aerostat has poor maneuverability, low carrying-capacity, and has become increasingly vulnerable to modern weaponry.   The advent of mechanurgy and modern industrial techniques have allowed for stronger, lighter materials and energy sources capable of providing power without excessive weight constraints. Now, there are two primary buoyancy designs used in modern aerostats. The first retains the use of lifting gases such as hydrogen and helium but utilizes rigid materials for the envelope. In 1284 CE, the first rigid aerostat was developed by Nasuc Iwutan in Khahlanong. These designs originally retained the balloon-like envelope, but more modern designs compartmentalize the envelope or spread multiple gas envelopes across the craft. The second design, created in 1339 CE by Etqecmnyof Bantfe, uses chambers kept at extremely low pressures compared to the surrounding air. These low-pressure chambers are kept at a near-vacuum, which is both more efficient for buoyancy than hydrogen and is far safer. Until recently, the structural challenges made it impossible, as chambers strong enough to not collapse in on themselves would be heavy enough to counteract the benefits. Low-pressure buoyancy allows for significantly larger aerostats, which became a crucial factor in the Last War.

Propulsion and Steering

For centuries, aerostats were propelled by sails of coated canvas stretched over a frame, typically mounted on both sides of the vessel to distribute the force. Rudders made with the same principle were mounted on the back, to steer the craft. This design lasted decades after the introduction of powered seafaring vessels and locomotives, because of the difficulties of building an engine light enough to make the benefits worth the increased weight. In 1273 CE, a team of researchers at Tshakuksuha University were able to integrate a steam engine into an aerostat to power propellors, and within a decade sail-powered vessels were nearly obsolete.   Modern aerostats primarily use mechanurgical engines, which are far-outstrip any engine running on non-transcendental properties. These engines allow the use of powerful rotors for takeoff and landing, as well as quick course adjustments, removing the necessity of a rudder. Many aerostats are now built with aerodynamic elements, such as the aforementioned rotors. Flattened designs are used to increase aerodynamic lift, and adjustable elevators are built in to increase vertical maneuverability.   Within the last couple decades, some vessels have been designed with extended wing planes to provide aerodynamic lift. This allows for much greater speeds but with significant tradeoffs in carrying capacity and efficiency.

Carrying Compartments

In older designs, passengers and equipment would be placed in a compartment beneath the envelope. Newer designs distribute the envelope(s) across the vessel, and the carrying compartments are integrated into the design. Depending on the purpose of the aerostat, the compartments will be placed in different configurations. Most military aerostats shift the carrying compartments upwards to protect the crew and equipment.   Larger aerostats, particularly those with military applications, are often equipped with skyhooks. These are hook-shaped protrusions, often found in sheltered nooks on the sides of the aerostat, that carry autogyros for quick deployment. The skyhooks can be extended to catch returning autogyros.

Applications

Trade and Transportation

Wilderness in Duurn is dangerous and the seas even moreso, making transportation by air much more appealing. For about three hundred years, aerostats have been used at every level for civilian transportation. Shipping companies own fleets of huge cargo aerostats, while smaller merchants might own one or two dated vessels. They are much too expensive for most individuals to own or maintain, but some wealthy families can afford the expense. In the civilian sphere, old-model aerostats using hydrogen or helium gas for lift are most common, though some larger companies and extremely wealthy individuals possess low-pressure buoyant vessels. Fabric envelopes have fallen almost completely out of use, but they are still sometimes seen in economically poorer regions or as antiques.

Military

Since their invention, aerostats have been used by Duurn militaries, but the strategies around their application have changed significantly, especially during the Last War. Prior to the Last War, most aerial doctrine tended to revolve around decisive battles between massive fleets. Most aerial strategy was directed towards hunting and eliminating the enemy fleet to establish air control. The development of oil-fueled transcendental machines and low-pressure buoyancy allowed for the creation of a class of aerostat called the dreadnought, both better armored and armed than any class of aerostat before it. An arms race began towards ever larger vessels.   The creation of dreadnoughts, the development of radio, and advancements in ballistics all made decisive battle doctrine much less effective. New naval doctrines emphasize raiding tactics, blockades, and area denial. While massive fleets still exist, they rarely engage directly with one another and instead send raiding detachments to attack merchant vessels, provide support to ground forces, and skirmish with enemy detachments. In many ways, aerostats have become mobile command hubs, able to land units of infantry and support them from the air with artillery strikes and autogyro support.

Piracy

Traditionally, pirates drew to their ranks the dispossessed and down-on-their-luck, and they did not often have the resources to acquire and maintain the most modern vessels. instead, they used repurposed cargo aerostats, decomissioned military vessels, and civilian ships. Some lucky pirates used military aerostats seized during a raid. During the Last War, many military vessels were lost to deserters or resourceful scavengers, flooding the black markets. Pirate aerostats are often smaller and more focused on agile hit-and-run raids and boarding actions.