ramjet


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Related to ramjet: ramjet engine, scramjet

ramjet:

see jet propulsionjet propulsion,
propulsion of a body by a force developed in reaction to the ejection of a high-speed jet of gas. Jet Propulsion Engines

The four basic parts of a jet engine are the compressor, turbine, combustion chamber, and propelling nozzles.
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Ramjet

A member of a class of high-speed air-breathing propulsion systems. These include subsonic combustion ramjets (RAM), supersonic combustion ramjets (SCRAM), dual-mode ram-scramjets (RAM-SCRAM), dual-combustor ramjets (DCR or DCRJ), and air-ducted rockets (ADR). In each case, air collected from the atmosphere is ducted into the engine to serve as the oxidizer for the burning of fuel that is stored on board. All the engines operate on a modified form of the basic Joule or Brayton cycle; that is, the air is compressed in the inlet, burned at near-constant pressure, and accelerated in an expansion nozzle. In accordance with Newton's second law, thrust is produced by the increase in momentum as the gas passes from the inlet to the nozzle exit. Compression is produced by one or a multiplicity of compression waves generated on the inlet surfaces. The level of pressure that can be reached in these waves is insufficient to produce net thrust unless the air speed is greater than about Mach 0.9 (that is, the velocity is 0.9 times the local speed of sound). Thus the ramjet must be launched from a high-speed aircraft or brought up to speed by a booster rocket or another adjunct engine. The latter type are known as combined-cycle engines. A classic example is the combination of a turbojet and a ramjet, which is called a turboramjet. See Brayton cycle, Rocket propulsion, Turbojet, Turboramjet

A subsonic combustion ramjet may be boosted to its operating speed by a solid-fueled rocket (see illustration). After the booster separates, the air entering the inlet is compressed through oblique shocks and a terminal normal shock. The flow aft of the normal shock and in the combustor is subsonic, but the velocity is high and flameholders are needed to anchor the flame and thereby produce high combustion efficiency. Passing from the combustor, the exhaust gases are reaccelerated in a converging-diverging nozzle to supersonic speed at the engine exit. See Nozzle

There are several characteristics that lead to the choice of one of the ramjet cycles for a variety of missions. Foremost are the engine performance as measured by specific impulse, light weight, and low cost. For applications up to about Mach 3, the turbojet has the highest specific impulse among hydrocarbon-fueled engines, which leads to its choice as the power plant for subsonic and supersonic aircraft. Most missile applications demand higher thrust which requires afterburning. For flight speeds between Mach 3 and 5, the subsonic combustion ramjet is optimal, and above Mach 5 the choice is among the supersonic combustion ramjet, the dual-mode ram-scramjet, and the dual-combustor ramjet. The solid rocket has much lower engine performance and is used only when high specific impulse is not the governing factor. Rocket-powered vehicles are used for relatively short-range missions or for near-to-vertical flight.

ramjet

A simple duct or tube of a special shape that collects the air caused by forward speed, or the ram effect; compresses it; makes it flow over some heat source; and then ejects the air at a higher speed than the entry speed. In this arrangement, there is no moving part and the system can work only at a forward speed. Originally called an aerothermodynamic duct

ramjet

, ramjet engine
a. a type of jet engine in which fuel is burned in a duct using air compressed by the forward speed of the aircraft
b. an aircraft powered by such an engine
References in periodicals archive ?
The Ramjet missile streaks through the sky at more than three times the speed of sound, meaning it can destroy an aircraft 50 miles away in less than a minute.
The Sanger 2 would use existing technology, be powered by a turbo ramjet that uses liquid hydrogen, and be operational around 2005.
had tested a ramjet aboard a P-80), offered funding, but the troubled economic and political situation in France as it engaged in decolonization wars complicated matters.
The vehicle accelerated to Mach 4.8 using a solid rocket booster, then reached Mach 5.1 with its air-breathing supersonic combustion ramjet (scramjet) engine before crashing into the sea as planned.
As the title suggests, The Development of jet and Turbine Afro Engines offers a historical look at turbine and other jet-type engines such as rocket, pulse jet, and ramjet. The primary focus, however, is on gas turbines, including turbojet, turbofan, turboshaft, and turboprop types.
THE vice girl at the centre of the Roger Ramjet vice scandal last night said: "He got what he deserved."
The last eight will be powered by a dual combustion ramjet engine at speeds up to Mach 6.
A rocket carrying the "scramjet" - short for supersonic combustion ramjet - went off course as it flew 196 miles above the Earth.
It was designed to use a ramjet for propulsion and to reach speeds of 2,500 mph (Mach 3.7) and altitudes of 75,000 feet.
He has to have a chin like Roger Ramjet, the shoulders of Johnny Weismuller, the ruggedness of Brad Pitt and the sexual prowess of a modern-day Errol Flynn.
Topics addressed by the French, Japanese, Romanian, Russian, Syrian, Ukrainian, British, and American authors include the influence of Russian engineers Konstantin Tsiolkovski and Jury Vasiljevich Knodratjuk on the evolution of space technology and space flight theory; the development by Yves Le Prieur of wartime applications for black powder rockets in World War I; World War II liquid rocket developments in Japan, ramjet and A4 propulsion research in the United States and Europe; British parliamentary debate over space policy in the late 1950s; the first Syrian cosmonaut and his experiments on the Mir Space Station; the history of US Space and Rocketry Center; and the research funding history of space lasers, floating rocket launch programs, and other space- related technology.