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Scramjet Speed

  1. Jan 30, 2006 #1
    The basic principle of a scramjet is to mix fuel with compressed air going supersonic speeds with relatively few or no moving parts. What I'm wondering is what the minimum speed the scramjet has to be moving to work properly. I've been looking on the web at numerous places, but no place gives me the same answer.
     
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  3. Jan 30, 2006 #2

    Astronuc

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  4. Jan 30, 2006 #3
  5. Jan 31, 2006 #4

    DaveC426913

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    That's becasue they're still experimental and probably a well-guarded secret.
     
  6. Feb 1, 2006 #5

    FredGarvin

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    You might be confusing a ramjet with a scramjet. There is a big difference between the two.
     
    Last edited: Feb 1, 2006
  7. Feb 1, 2006 #6

    DaveC426913

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    In that case, I stand with him in the "confused" camp. I was my understanding that a scramjet is, literally, a supersonic ramjet.


    And ... (hang on) ... it would appear that Wikipedia is in our camp too:

    "A scramjet (supersonic combustion ramjet) is a variation of a ramjet where the flow of the air and combustion of the fuel air mixture through the engine is done at supersonic speeds. This allows the scramjet to achieve greater speeds than a conventional ramjet which slows the incoming air to subsonic speeds before entering the combustion chamber."
     
  8. Feb 1, 2006 #7

    Astronuc

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    Definitely check out the Wikipedia article mentioned by Dave, but it will not answer the original question. - http://en.wikipedia.org/wiki/Scramjet

    The issue is that the nozzle design optimized for the high Mach range doesn't perform as well in the subsonic or low Mach range. The optimal geometry has to be tailored based on the physics of the shock waves in the inlet. The details may be available from NASA.

    See also - http://en.wikipedia.org/wiki/Hyper-X
     
  9. Feb 1, 2006 #8

    FredGarvin

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    When I first read this, I immediately thought that the question was saying "...mix fuel with compressed air WHILE going supersonic speeds." I had to reread the post to see that he meant that the airflow was indeed supersonic. I stand corrected. The only confused one here is me.
     
  10. Feb 1, 2006 #9
    Sorry Fred, I should have worded that better.
     
  11. Feb 2, 2006 #10

    Astronuc

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  12. Mar 25, 2006 #11

    Astronuc

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    Revolutionary jet engine tested - Hyshot III

    BBC Science News - http://news.bbc.co.uk/2/hi/science/nature/4832254.stm

    http://news.bbc.co.uk/2/hi/science/nature/4832254.stm#graphic

    See related thread - Mach 10 - https://www.physicsforums.com/showthread.php?t=52355

    Other links -

    Hypersonics at University of Queensland - http://www.uq.edu.au/hypersonics/

    QinetiQ - http://www.qinetiq.com/

    Australia's Defence Scientific and Technology Organisation - http://www.dsto.defence.gov.au/
     
    Last edited: Mar 25, 2006
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