Scram jet

Intro

A scram jet is a hypersonic air breathing vehicle where the air is collected and ignited with minimal change in velocity of the air stream. It is known as the holy grail of aerospace engineering. The fact that the air being collected for the oxidizer changes little in velocity before oxidization occurs, means that the vehicle is able to collect the oxidizer from the atmosphere with less drag than would be typical of a other air breathing vehicles such as (a ram jet and a jet plane).

The vehicle has many applications, including military (see project falcon), space (see X43-A), rapid parcel deliver and 30 minute flights from New York to Tokyo. A scram presents the best hope for cheap access to space because it could potentially produce a SSTO ]]reusable launch vehicle]] with a mass ratio 16 times better than what is possible from non air breathing vehicles.

This is because the mass of the oxidizer (oxygen) is 16 times more than the mass of the reducer (hydrogen). Despite the scram jets superior performance it cannot be used at each point in the flight because it only works at high velocities within the atmosphere. Other methods of propulsion like the ramjet will be required to get the vehicle up to speed and take the scram jet from the upper portion of the atmosphere to space.

Although the majority of the trip in distance is between the top of the atmosphere to LEO by far the greatest energy is spent obtaining orbital velocity as opposed to orbital altitude. Thus the majority of the energy will be given to the rocket through scram jet propulsion and not other propulsion techniques.

External Links

A nice short explanation of the ramjet and scramjet with some simple diagrams. Seems slightly dated though

S-43A at NASA

NASA What is a scram jet

Scramjet from wikipedia Contains a fair amount of theory. A good second source.

Scramjet from aerospaceweb.org As well as the X-43A shows the conceptural WaveRider (SED-WR)

Theoretical Papers

Alexander S. Roudakov, Vyacheslav L. Semenov, John W. Hicks, [http://www.nasa.gov/centers/dryden/pdf/88580main_H-2243.pdf NASA Dryden Flight Research Center Edwards, California Recent Flight Test Results of the Joint CIAMNASA Mach 6.5 Scramjet Flight Program]

M. K. Smart, Experimental Testing of a Hypersonic Inlet with Rectangular-to-Elliptical Shape Transition

Gentle Papers

Air-breathing propulsion, PROPULSION AND ENERGY

And Now Some Poems

The Scram Bird ref
Soaring High like None Bird Before
Breathing air too thin for a plane
Creature or Machine it goes at speeds insane.
A feet man, swift and cheater would adore

Between black and blue the scram bird soars
Heavy rockets put to shame
Only primitive technology is to blame
The holler grail of aviation and more

By John Creighton