Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!emory!att!cbnews!cbnews!military
From: muller@ecn.purdue.edu (Mark B. Muller)
Newsgroups: sci.military
Subject: Scramjets & Ramjets
Message-ID: <1990Dec5.031758.7595@cbnews.att.com>
Date: 5 Dec 90 03:17:58 GMT
Sender: military@cbnews.att.com (William B. Thacker)
Organization: AT&T Bell Laboratories
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Approved: military@att.att.com



From: muller@ecn.purdue.edu (Mark B. Muller)

>From: elec140@csc.canterbury.ac.nz
>In article <1990Dec3.050627.2654@cbnews.att.com>, henry@zoo.toronto.edu (Henry Spencer) writes:
   [discussion of eficieny of ramjets deleted]
>
>If this is true, then where is the distinction between a ramjet and a scramjet?
>Is it to do with an external combustion chamber, or is this only one
>implementation of a scramjet?
>
   a scramjet is a Supersonic Combustion Ramjet.  This means that the 
   flow through the combustion process is supersonic.  In a conventional
   ramjet, even when flying at supersonic speeds, the flow is slowed to 
   subsonic speeds, the fuel added and burned, and then the flow accelerated
   again before going out the back. The changes in speed are accomplished
   via the geometry of the inlet and the exhaust nozzle.

   As far as efficieny goes, it all depends on flight regime.  For low
   subsonic speeds, Turbopros are generally best, while for high subsonic
   speeds, turbofans are most efficient.  In the transonic and low supersonic
   regime, turbojets become efficient, while at supersonic and high
   supersonic speeds, ramjets become attractive.  At speeds above this 
   (around mach 5), scramjets become "better".  Of course, there are other
   considerations in choice of engines.  For example, many subsonic
   missiles use ramjets or solid rockets to save weight and simplify things,
   as these engines have few moving parts.

   

  *-------------------------------------------------------------------------*
  *  Mark Muller                  Undergraduate at Purdue University        *
  *  muller@gn.ecn.purdue.edu     Aeronautics & Astronautics Engineering    *
  *-------------------------------------------------------------------------*


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