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Jet aircraft

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A jet aircraft is a vehicle propelled by one or more jet engines. Most jets are fixed-wing aircraft, meaning their wings do not move during flight. These machines are designed to fly at very high speeds. They often operate at transonic speeds, which is just below the speed of sound. Many jets cruise at Mach 0.8, roughly 981 km/h (610 mph). They typically fly at altitudes between 10,000 and 15,000 meters. This high altitude allows jet engines to operate with maximum efficiency.

To fly efficiently at high speeds, engineers use the Whitcomb area rule. This rule states that the total cross-sectional area of an aircraft should follow a specific shape called a Sears-Haack body. By following this rule, designers can minimize shockwaves. Shockwaves are a problem because they waste energy during flight. The engine itself works by expelling hot gas to create thrust. This process is measured by propulsive efficiency. This is the percentage of energy from the fuel that actually moves the plane. It is never 100% because some energy is always lost to air drag and gravity.

Propulsive efficiency
Propulsive efficiency

There are several distinct types of jet engines used for different purposes. A turbojet has a very high exhaust speed. This makes it ideal for supersonic flight, which is faster than sound. However, turbojets are not very efficient for slower, subsonic flight. A turbofan is a different design that uses a large fan. High bypass turbofans are very efficient and are used by most modern airliners. Low bypass turbofans are often used for transonic or low supersonic speeds. Other propulsion types include ramjets, pulsejets, and even rocket engines.

Boeing 707-138B Qantas Jett Clipper Ella N707JT
Boeing 707-138B Qantas Jett Clipper Ella N707JT

The history of jet flight began with independent work by two inventors. Frank Whittle, an English officer, began developing jet engines in 1928. Hans von Ohain worked on similar concepts in Germany during the early 1930s. In August 1939, the Heinkel He 178 became the first jet aircraft to fly. This flight took place in Rostock, Germany, using von Ohain's design. Early engines faced a problem called "creep," which is metal fatigue from high heat. This caused early engines to burn out quickly. Eventually, the axial-flow engine design became the industry standard by the 1950s.

Ohain USAF He 178 page61
Ohain USAF He 178 page61

Military jet development moved very quickly during the mid-1940s. The Messerschmitt Me 262 was the first operational jet fighter. It entered service in April 1944 and had 300 aircraft go into combat. The Gloster Meteor was the first production jet from the United Kingdom. In the United States, the Lockheed P-80 Shooting Star was introduced by the end of 1945. During the Korean War, a jet-to-jet dogfight occurred in 1950. A US pilot shot down two North Korean MiG-15s in this historic encounter. The fastest military jet ever recorded was the SR-71 Blackbird. It could reach speeds as high as Mach 3.35.

Lockheed SR-71 Blackbird (modified)
Lockheed SR-71 Blackbird (modified)

Commercial aviation was transformed by the arrival of jet travel. The de Havilland Comet began the first commercial jet service in 1952. It flew from London to Johannesburg and offered a smoother ride than propeller planes. However, the Comet suffered from metal fatigue due to design defects. This allowed the Boeing 707 to enter the market in 1958 and become very successful. The 707 used underslung engines, which were safer if a fuel leak occurred. Later, supersonic transports like the Concorde entered service. The Concorde flew at Mach 2 for 27 years, from 1976 to 2003.

British Airways Concorde G-BOAC 03
British Airways Concorde G-BOAC 03

Jet technology connects to many different areas of science and engineering. It relates to thermodynamics through engine heat and energy conversion. It also connects to aerodynamics through the study of air resistance and shockwaves. Even specialized vehicles like helicopters use jet technology. Some compound helicopters use auxiliary turbojets to add extra thrust. There are even jet-powered wingsuits that allow humans to fly for short periods. In the most extreme cases, the X-43 scramjet can reach speeds of Mach 9 to 10. This shows how jet propulsion continues to push the limits of speed and flight.

XH-59 U.S. Army demonstrator
XH-59 U.S. Army demonstrator
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🖼️ Images & Media (7)
File:McDonnell Douglas DC-10-30, Omni Air International - OAI AN0377799.jpg
McDonnell Douglas DC-10-30, Omni Air...
File:Ohain USAF He 178 page61.jpg
Ohain USAF He 178 page61.jpg
File:Boeing 707-138B Qantas Jett Clipper Ella N707JT.jpg
Boeing 707-138B Qantas Jett Clipper Ella...
File:British Airways Concorde G-BOAC 03.jpg
British Airways Concorde G-BOAC 03.jpg
File:XH-59 U.S. Army demonstrator.jpg
XH-59 U.S. Army demonstrator.jpg
File:Lockheed SR-71 Blackbird (modified).jpg
Lockheed SR-71 Blackbird (modified).jpg
File:Propulsive efficiency.png
Propulsive efficiency.png
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