A fixed-wing aircraft is a heavier-than-air aircraft, such as an airplane, which is capable of flight using aerodynamic lift. Fixed-wing aircraft are distinct from rotary-wing aircraft, and ornithopters. The wings of a fixed-wing aircraft are not necessarily rigid; kites, hang gliders, variable-sweep wing aircraft, and airplanes that use wing morphing are all classified as fixed wing.
Flight or flying is the process by which an object moves through a space without contacting any planetary surface, either within an atmosphere or through the vacuum of outer space. This can be achieved by generating aerodynamic lift associated with gliding or propulsive thrust, aerostatically using buoyancy, or by ballistic movement.
Buoyancy, or upthrust is a net upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus, the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the displaced fluid.
A bathyscaphe is a free-diving, self-propelled deep-sea submersible, consisting of a crew cabin similar to a Bathysphere, but suspended below a float rather than from a surface cable, as in the classic Bathysphere design.
An underwater environment is a environment of, and immersed in, liquid water in a natural or artificial feature, such as an ocean, sea, lake, pond, reservoir, river, canal, or aquifer. Some characteristics of the underwater environment are universal, but many depend on the local situation.
Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces. Archimedes' principle is a law of physics fundamental to fluid mechanics. It was formulated by Archimedes of Syracuse.
A Cartesian diver or Cartesian devil is a classic science experiment which demonstrates the principle of buoyancy and the ideal gas law. The first written description of this device is provided by Raffaello Magiotti, in his book Renitenza certissima dell'acqua alla compressione published in 1648. It is named after René Descartes as the toy is said to have been invented by him.
A buoyancy compensator (BC), also called a buoyancy control device (BCD), stabilizer, stabilisor, stab jacket, wing or adjustable buoyancy life jacket (ABLJ), depending on design, is a type of diving equipment which is worn by divers to establish neutral buoyancy underwater and positive buoyancy at the surface, when needed.
Diving physics, or the physics of underwater diving is the basic aspects of physics which describe the effects of the underwater environment on the underwater diver and their equipment, and the effects of blending, compressing, and storing breathing gas mixtures, and supplying them for use at ambient pressure. These effects are mostly consequences of immersion in water, the hydrostatic pressure of depth and the effects of pressure and temperature on breathing gases. An understanding of the physics behind is useful when considering the physiological effects of diving, breathing gas planning and management, diver buoyancy control and trim, and the hazards and risks of diving.
A submersible is an underwater vehicle which needs to be transported and supported by a larger watercraft or platform. This distinguishes submersibles from submarines, which are self-supporting and capable of prolonged independent operation at sea.
An emergency landing is a premature landing made by an aircraft in response to an emergency involving an imminent or ongoing threat to the safety and operation of the aircraft, or involving a sudden need for a passenger or crew on board to terminate the flight. It typically involves a forced diversion to the nearest or most suitable airport or airbase, or an off airport landing or ditching if the flight cannot reach an airfield. Flights under air traffic control will be given priority over all other aircraft operations upon the declaration of the emergency.
An underwater glider is a type of autonomous underwater vehicle (AUV) that employs variable-buoyancy propulsion instead of traditional propellers or thrusters. It employs variable buoyancy in a similar way to a profiling float, but unlike a float, which can move only up and down, an underwater glider is fitted with hydrofoils that allow it to glide forward while descending through the water. At a certain depth, the glider switches to positive buoyancy to climb back up and forward, and the cycle is then repeated.
Glider or Gliders may refer to:
Gliding flight is heavier-than-air flight without the use of thrust; the term volplaning also refers to this mode of flight in animals. It is employed by gliding animals and by aircraft such as gliders. This mode of flight involves flying a significant distance horizontally compared to its descent and therefore can be distinguished from a mostly straight downward descent like a round parachute.
A glider or sailplane is a type of glider aircraft used in the leisure activity and sport of gliding. This unpowered aircraft can use naturally occurring currents of rising air in the atmosphere to gain altitude. Sailplanes are aerodynamically streamlined and so can fly a significant distance forward for a small decrease in altitude.
Certain species of fish and birds are able to locomote in both air and water, two fluid media with very different properties. A fluid is a particular phase of matter that deforms under shear stresses and includes any type of liquid or gas. Because fluids are easily deformable and move in response to applied forces, efficiently locomoting in a fluid medium presents unique challenges. Specific morphological characteristics are therefore required in animal species that primarily depend on fluidic locomotion. Because the properties of air and water are so different, swimming and flying have very disparate morphological requirements. As a result, despite the large diversity of animals that are capable of flight or swimming, only a limited number of these species have mastered the ability to both fly and swim. These species demonstrate distinct morphological and behavioral tradeoffs associated with transitioning from air to water and water to air.
A float is an oceanographic instrument platform used for making subsurface measurements in the ocean without the need for a ship, propeller, or a person operating it. Floats measure the physical and chemical aspects of the ocean in detail, such as measuring the direction and speed of water or the temperature and salinity. A float will descend to a predetermined depth where it will be neutrally buoyant. Once a certain amount of time has passed, most floats will rise back to the surface by increasing its buoyancy so it can transmit the data it collected to a satellite. A float can collect data while it is neutrally buoyant or moving through the water column. Often, floats are treated as disposable, as the expense of recovering them from remote areas of the ocean is prohibitive; when the batteries fail, a float ceases to function, and drifts at depth until it runs aground or floods and sinks. In other cases, floats are deployed for a short time and recovered.
In engineering, variable-buoyancy propulsion is the use of a buoyancy engine to provide propulsion for a vehicle. The concept was first explored in the 1960s for use with underwater gliders, but has since been applied to autonomous aircraft as well.
A variable-buoyancy pressure vessel system is a type of rigid buoyancy control device for diving systems that retains a constant volume and varies its density by changing the weight (mass) of the contents, either by moving the ambient fluid into and out of a rigid pressure vessel, or by moving a stored liquid between internal and external variable-volume containers. A pressure vessel is used to withstand the hydrostatic pressure of the underwater environment. A variable-buoyancy pressure vessel can have an internal pressure greater or less than ambient pressure, and the pressure difference can vary from positive to negative within the operational depth range, or remain either positive or negative throughout the pressure range, depending on design choices.
Underwater exploration is the exploration of any underwater environment, either by direct observation by the explorer, or by remote observation and measurement under the direction of the investigators. Systematic, targeted exploration is the most effective method to increase understanding of the ocean and other underwater regions, so they can be effectively managed, conserved, regulated, and their resources discovered, accessed, and used. Less than 10% of the ocean has been mapped in any detail, less has been visually observed, and the total diversity of life and distribution of populations is similarly obscure.
