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From: eachus@linus.mitre.org (Robert I. Eachus)
Newsgroups: sci.military
Subject: Re: Scramjets
Message-ID: <1990Nov21.222054.20868@cbnews.att.com>
Date: 21 Nov 90 22:20:54 GMT
References: <1990Nov20.021943.27530@cbnews.att.com>
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From: eachus@linus.mitre.org (Robert I. Eachus)


    A SCRAMjet is a Supersonic Combustion RAMjet engine.  In an
ordinary jet engine the incoming air is heated and compressed by
turbulence in the intake of a supersonic plane so that the combustion
(burning) of the fuel can take place under subsonic conditions.  A
SCRAM uses Hydrogen fuel (with a much higher speed of sound at the
same temperature and pressure as air) and combustion takes place at
where the air hits a laminar flow of hydrogen.  This reduction in
turbulence allows both higher speeds and higher efficiency.

    Think of it this way, in a (very) high speed aircraft, most of the
heating of the incoming air occurs before combustion.  There is a
limit reached where all of the thrust is being converted into heating
of incoming air (and leading edges).  In a SCRAMjet the heating of the
airflow occurs in the combustion region, and much more of the thrust
can be devoted to moving the aircraft.

--

					Robert I. Eachus

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