Jet propulsion in the context of "Jet engines"

An octopus (pl.: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (/ɒkˈtɒpədə/, ok-TOP-ə-də). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like other cephalopods, an octopus is bilaterally symmetric with two eyes and a beaked mouth at the centre point of the eight limbs. An octopus can radically deform its shape, enabling it to squeeze through small gaps. They trail their appendages behind them as they swim. The siphon is used for respiration and locomotion (by water jet propulsion). Octopuses have a complex nervous system and excellent sight, and are among the most intelligent and behaviourally diverse invertebrates.

Octopuses inhabit various ocean habitats, including coral reefs, pelagic waters, and the seabed; some live in the intertidal zone and others at abyssal depths. Most species grow quickly, mature early, and are short-lived. In most species, the male uses a specially-adapted arm to deliver sperm directly into the female's mantle cavity, after which he becomes senescent and dies, while the female deposits fertilised eggs in a den and cares for them until they hatch, after which she also dies. They are predators and hunt crustaceans, bivalves, gastropods and fish. Strategies to defend themselves against their own predators include expelling ink, camouflage, and threat displays, the ability to jet quickly through the water and hide, and deceit. All octopuses are venomous, but only the blue-ringed octopuses are known to be deadly to humans.

Air-breathing jet engines typically feature a rotating air compressor powered by a turbine, with the leftover power providing thrust through the propelling nozzle—this process is known as the Brayton thermodynamic cycle. Jet aircraft use such engines for long-distance travel. Early jet aircraft used turbojet engines that were relatively inefficient for subsonic flight. Most modern subsonic jet aircraft use more complex high-bypass turbofan engines. They give higher speed and greater fuel efficiency than piston and propeller aeroengines over long distances. A few air-breathing engines made for high-speed applications (ramjets and scramjets) use the ram effect of the vehicle's speed instead of a mechanical compressor.

An airbreathing jet engine (or ducted jet engine) is a jet engine in which the exhaust gas which supplies jet propulsion is atmospheric air, which is taken in, compressed, heated, and expanded back to atmospheric pressure through a propelling nozzle. Compression may be provided by a gas turbine, as in the original turbojet and newer turbofan, or arise solely from the ram pressure of the vehicle's velocity, as with the ramjet and pulsejet.

All practical airbreathing jet engines heat the air by burning fuel. Alternatively a heat exchanger may be used, as in a nuclear-powered jet engine. Most modern jet engines are turbofans, which are more fuel efficient than turbojets because the thrust supplied by the gas turbine is augmented by bypass air passing through a ducted fan.

A salp (pl.: salps) or salpa (pl.: salpae or salpas) is a barrel-shaped, planktonic tunicate in the family Salpidae. The salp moves by contracting its gelatinous body in order to pump water through it; it is one of the most efficient examples of jet propulsion in the animal kingdom. The salp feeds on phytoplankton, which it collects by straining water through its internal feeding filters.

The Aero L-39 Albatros is a high-performance jet trainer designed and produced by Aero Vodochody in the Czech Republic. In addition to performing basic and advanced pilot training, it has also flown combat missions in a light-attack role. Despite its manufacturing origin in the Warsaw Pact, the L-39 never received a NATO reporting name.

The L-39 Albatros was designed during the 1960s as a successor to the Aero L-29 Delfín, an early jet-powered principal training aircraft. Performing its maiden flight on 4 November 1968, it became the first trainer aircraft in the world to be equipped with a turbofan powerplant. Quantity production of the L-39 Albatros proceeded in 1971; one year later, it was formally recognized by the majority of the Warsaw Pact countries as their preferred primary trainer. Accordingly, thousands of L39s would be produced for various military customers in Eastern Europe. Additionally, it was exported to a range of countries across the world both as a trainer and a light-attack aircraft. Since the 1990s, it has also become popular among civilian operators. By the end of the century, in excess of 2,800 L-39s had served with over 30 air forces.

The Heinkel He 178 was an experimental aircraft designed and produced by the German aircraft manufacturer Heinkel. It was the world's first aircraft to fly using the thrust from a turbojet engine.

The He 178 was developed to test the jet propulsion concept devised by the German engineer Hans von Ohain during the mid-1930s. Having secured the industrial support of Ernst Heinkel, von Ohain was able to demonstrate a working turbojet engine, the Heinkel HeS 1, in September 1937. Heinkel pursued development of the He 178 as a private venture, independent of the German authorities and the Luftwaffe, keeping the aircraft relatively secret for much of its development. Heinkel was keen not only to demonstrate the capabilities of aviation gas turbines, but had a separate emphasis on developing high-speed flight technologies.

The Boeing 367-80, also known as the Dash 80, is a retired American four-engined prototype jet aircraft by Boeing to demonstrate the advantages of jet propulsion for commercial aviation. It served as basis for the design of the KC-135 tanker and the 707 airliner.

The Boeing 367-80 first flew in 1954, less than two years from project launch. Its US$16 million cost (equivalent to $187 million today) was an enormous risk for Boeing, which at the time had no committed customers. Only one example was built, which has been retired and now preserved and is on public display at the Smithsonian's National Air and Space Museum's Udvar-Hazy Center in Virginia.