Aerostat in the context of Weight

Aviation includes the activities surrounding mechanical flight and the aircraft industry. Aircraft include fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air aircraft such as hot air balloons and airships.

Aviation began in the 18th century with the development of the hot air balloon, an apparatus capable of atmospheric displacement through buoyancy. Clément Ader built the "Ader Éole" in France and made an uncontrolled, powered hop in 1890. This was the first powered aircraft, although it did not achieve controlled flight. Some of the most significant advancements in aviation technology came with the controlled gliding flying of Otto Lilienthal in 1896. A major leap followed with the construction of the Wright Flyer, the first powered airplane by the Wright brothers in the early 1900s.

A vehicle (from Latin vehiculum) is a machine designed for self-propulsion, usually to transport people, cargo, or both. The term "vehicle" typically refers to ground transport vehicles such as human-powered land vehicles (e.g. bicycles, tricycles, velomobiles), animal-powered transports (e.g. horse-drawn carriages/wagons, ox carts, dog sleds), motor vehicles (e.g. motorcycles, cars, trucks, buses, mobility scooters) and railed vehicles (trains, trams and monorails), but more broadly also includes cable transport (cable cars and elevators), watercraft (ships, boats and underwater vehicles), amphibious vehicles (e.g. screw-propelled vehicles, hovercraft, seaplanes), aircraft (airplanes, helicopters, gliders and aerostats) and space vehicles (spacecraft, spaceplanes and launch vehicles).

This article primarily concerns the more ubiquitous land vehicles, which can be broadly classified by the type of contact interface with the ground: wheels, tracks, rails or skis, as well as the non-contact technologies such as maglev. ISO 3833-1977 is the international standard for road vehicle types, terms and definitions.

Flight or flying is the motion of an object through an atmosphere or through the vacuum of space, in this case also called spaceflight, without contacting any planetary surface. This can be achieved by generating aerodynamic lift associated with gliding or propulsive thrust, aerostatically using buoyancy, or by ballistic movement.

Many things can fly, from animal aviators such as birds, bats and insects, to natural gliders/parachuters such as patagial animals, anemochorous seeds and ballistospores, to human inventions like aircraft (airplanes, helicopters, airships, balloons, etc.) and rockets which may propel spacecraft and spaceplanes.

In aeronautics, a balloon is an unpowered aerostat, which remains aloft or floats due to its buoyancy. It may use hot air as a lifting gas, or it may use gas that is not air like hydrogen or helium. A balloon may be free, moving with the wind, or tethered to a fixed point. It is distinct from an airship, which is a powered aerostat that can propel itself through the air in a controlled manner.

Many balloons have a basket, gondola, or capsule suspended beneath the main envelope for carrying people or equipment (including cameras and telescopes, and flight-control mechanisms).

An airship, dirigible balloon or dirigible is a type of aerostat (lighter-than-air) aircraft that can navigate through the air flying under its own power. Aerostats use buoyancy from a lifting gas that is less dense than the surrounding air to achieve the lift needed to stay airborne.

In early dirigibles, the lifting gas used was hydrogen, due to its high lifting capacity and ready availability, but the inherent flammability led to several fatal accidents that rendered hydrogen airships obsolete. The alternative lifting gas, helium, is not flammable, but is rare and relatively expensive. Significant amounts were first discovered in the United States and for a while helium was only available for airship usage in North America. Most airships built since the 1960s have used helium, though some have used hot air.

Police aviation is the use of aircraft in police operations. Police services commonly use aircraft for traffic control, ground support, search and rescue, high-speed car pursuits, observation, air patrol and control of large-scale public events and/or public order incidents. They may employ rotary-wing aircraft, fixed-wing aircraft, nonrigid-wing aircraft or lighter-than-air aircraft. In some major cities, police rotary-wing aircraft are also used as air transportation for personnel belonging to police tactical units. In large, sparsely populated areas, fixed-wing aircraft are sometimes used to transport personnel and equipment.

Army aviation is military aviation that is organized as a sub-branch under the command of an army, separate from a nation's dedicated air force. Army aviation units, sometimes described as air corps, are typically attached as a part of to a ground force and tasked to tactically assist its land warfare by providing close air support, rapid insertion, reconnaissance and logistics for front line ground operations. They usually comprise VTOL aircraft such as military helicopters, as well as gyrocopters, light fixed-wing attack aircraft and unmanned aerial vehicles (drones), and historically also aerostats such as military balloons and airships.

Prior to the establishment of separate national air forces, many armies had aviation units, which as the importance of aviation increased, were spun off into independent branches of the military. As the separation between a nation's ground and air forces led to a divergence of priorities, many armies sought to re-establish their own aviation branches to best serve their own organic tactical needs.

Bartolomeu Lourenço de Gusmão (December 1685 – 18 November 1724) was a Portuguese priest and naturalist from Colonial Brazil who was a pioneer of lighter-than-air aerostat design, being among the first scholars at that time to understand the operational principles of the hot air balloon and to build a functional prototype of such device. He is also one of the main characters in Nobel Prize-winning José Saramago's Baltasar and Blimunda.

Takeoff or take-off is the phase of flight during which an aerial vehicle leaves the ground and becomes airborne. For space vehicles that launch vertically, this is known as liftoff.

For fixed-wing aircraft that take off horizontally (conventional takeoff), this usually involves an accelerating ground run (known as the roll) on a runway to build up speed so the wings can generate enough lift. For aerostats (balloons and airships), helicopters, tiltrotors (e.g. the V-22 Osprey) and thrust-vectoring STOVL fixed-wing aircraft (e.g. the Harrier jump jet and F-35B), a helipad/STOLport is sufficient and no runway is needed.

The Tethered Aerostat Radar System (TARS) is an American low-level airborne ground surveillance system that uses aerostats (moored balloons) as radar platforms. Similar systems include the EL/M-2083 and JLENS.

A tethered, moored or captive balloon is a balloon that is restrained by one or more tethers attached to the ground so it cannot float freely. The base of the tether is wound around the drum of a winch, which may be fixed or mounted on a vehicle, and is used to raise and lower the balloon.

A balloon is a form of aerostat, along with the powered free-flying airship, although the American GAO has used the term "aerostat" to describe a tethered balloon in contrast to the powered airship.

A ballonet is an inflatable bag inside the outer 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.

Ballonets may typically be used in non-rigid or semi-rigid airships, commonly with multiple ballonets located both fore and aft to maintain balance and to control the pitch of the airship.