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Douglas Harper's Etymology Dictionary

1942, from ram (v.) + jet (n.).


n. (context aviation English) A jet engine in which forward motion forces air into an inlet, compressing it (as opposed to having a pump type device compressing the air for combustion with fuel), and where combustion is subsonic.


n. a simple type of jet engine; must be launched at high speed [syn: ramjet engine, atherodyde, athodyd, flying drainpipe]


A ramjet, sometimes referred to as a flying stovepipe or an athodyd (an abbreviation of aero thermodynamic duct), is a form of airbreathing jet engine that uses the engine's forward motion to compress incoming air without an axial compressor. Because ramjets cannot produce thrust at zero airspeed, they cannot move an aircraft from a standstill. A ramjet-powered vehicle, therefore, requires an assisted take-off like a rocket assist to accelerate it to a speed where it begins to produce thrust. Ramjets work most efficiently at supersonic speeds around . This type of engine can operate up to speeds of .

Ramjets can be particularly useful in applications requiring a small and simple mechanism for high-speed use, such as missiles. Weapon designers are looking to use ramjet technology in artillery shells to give added range; a 120 mm mortar shell, if assisted by a ramjet, is thought to be able to attain a range of . They have also been used successfully, though not efficiently, as tip jets on the end of helicopter rotors.

Ramjets differ from pulsejets, which use an intermittent combustion; ramjets employ a continuous combustion process.

As speed increases, the efficiency of a ramjet starts to drop as the air temperature in the inlet increases due to compression. As the inlet temperature gets closer to the exhaust temperature, less energy can be extracted in the form of thrust. To produce a usable amount of thrust at yet higher speeds, the ramjet must be modified so that the incoming air is not compressed (and therefore heated) nearly as much. This means that the air flowing through the combustion chamber is still moving very fast (relative to the engine), in fact it will be supersonic - hence the name Supersonic Combustion Ramjet, or scramjet.

Ramjet (Transformers)

Ramjet is the name of several fictional characters in the Transformers toy-based media franchise. All have been Decepticon aligned characters who turn into jets, usually white.

Ramjet (Image Comics)

' Gage Reinhart' is a fictional character appearing in publications by Image Comics. Created by writer Jay Faerber and artist Mahmud A. Asrar, he first appeared in Dynamo 5 #1 (January 2007).

For the first 24 issues of the series, the character possessed telepathy, and went by the codename Scatterbrain. In issue #25 of the series (October 2009), the character, whose powers had been erased in the previous issue, obtained different powers. Now possessing the power of flight, he goes by the codename Ramjet.

Ramjet (disambiguation)

Ramjet may refer to:

  • Ramjet, the high speed propulsion engine free of moving parts
  • Ramjet (Transformers), a fictional character in the Transformers toyline
  • Ramjet (Image Comics), a superhero and member of Dynamo 5
  • Bussard ramjet, a theoretical form of spacecraft propulsion

Usage examples of "ramjet".

It was the light of a Bussard ramjet, burning a bare eight miles away.

There is a minimum speed at which a Bussard ramjet will operate, and Phssthpok was not far above it.

The abandoned Bussard ramjet crossed over the sun and curved inward, following a shallow hyperbola which would take it through the plane of the planets.

The faster a Bussard ramjet ship moves, the more fuel it would pick up.

Three great hollows held the components of a Pak-style Bussard ramjet ship.

I might believe they loaded everything on the trailing ship and used the lead ship purely as a stripped Bussard ramjet compressor.

The lead ship is a Bussard ramjet, built to fight, but not too different from ours.

A Bussard ramjet will put out a lot of funny chemicals: high-energy hydrogen and helium, lithium radicals, some borates, even lithium hydride, which is generally an impossible chemical.

They were more airplane than spaceship, for, although each was sealed and pressurized to operate outside the atmosphere while making contact with orbiting spaceships, each was winged and was powered with ramjet atmosphere engines as well as with rocket jets.

In a paper published in Astronautica Acta in 1973 he points out that a ramjet built of aluminum could withstand a journey of 12.

Bonded with a high-strength synthetic resin, a diamond fiber Bussard ramjet could travel those thirty-five hundred light-years in 15.

If we consider operating near the hot stars or near nebulae which throw off masses of hydrogen, the ramjet would really begin to take full advantage of the effects of Time Dilation in Relativity, as outlined earlier in this chapter.

However, a Bussard ramjet steered through this zone would need to be brought up to power gradually by slowly turning on the magnetic field.

But with an ion ramjet you could collect all there are in a given part of space, convert them to energy, and fly your machine for many years in the atmosphere.

Intense study of gossamer flight, ramjet flight, solar-powered flight.