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Pressure Impulses during Supersonic Flight

  1. Aug 18, 2015 #1
    Hey Everyone. I am new to this forum, so first of all greetings to everybody.

    What are your thoughts on the below idea..?
    Is it possible to make the pressure impulses created by a Supersonic Aircraft to travel faster than the speed of Sound? I know that the pressure impulses during a Supersonic flight cannot travel upstream of the aircraft, but can this be made possible?
     
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  3. Aug 18, 2015 #2

    A.T.

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  4. Aug 18, 2015 #3
    Yep, I am aware of the basics of Shock Wave theory.

    If need be, let me explain my question a little bit better.
    In a Subsonic speed regime there is no sonic boom because the pressure impulses created by the plane are travelling faster than the plane, so they can go upstream meaning that the air has warning of the approaching aircraft. However, in the Supersonic case the aircraft is travelling faster than the pressure impulses it creates so the air has no warning until the aircraft is close and there we have a sonic boom. It is these pressure impulses that are of interest to me and if it is possible for us to create something that would give a boost to these pressure impulses so that they can travel faster than the aircraft that produces them during a Supersonic flight.
     
  5. Aug 18, 2015 #4

    berkeman

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    Welcome to the PF.

    The speed of sound in air is a function of the air and its properties, not a function of what started the sound wave in the first place. :smile:
     
  6. Aug 19, 2015 #5

    A.T.

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    Doesn't the second wiki sentence answer your initial question, about faster than speed of sound propagation?

    " When a wave moves faster than the speed of sound in a liquid, gas or plasma (a fluid, in physics terminology) it is a shock wave."

    That is a different question: Faster than the aircraft, not just faster than the speed of sound.
     
  7. Aug 19, 2015 #6
    Adding a boost of energy won't make them go faster. Added energy will simply make them louder.

    The speed of sound (or shock wave) is a fixed property of the medium. The only way to increase it is to compress the air to make the speed-of-sound in that section of air slightly faster than it otherwise would have been. I think there was a aircraft company that was experimenting with changing the nose design of small jets to exploit this effect to reduce the sonic boom and make supersonic private jets feasible. (It may have been one of those theoretical Popular Science cover-candy things. I don't quite remember.)
     
  8. Aug 19, 2015 #7
    Thanks Alec for your reply. I think you get what I am saying. This is what I was looking for.
    Do you know of any sources that I can use to explore this idea?
     
  9. Aug 19, 2015 #8

    boneh3ad

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    Simply compressing air won't change the sound speed. Increasing the temperature is required. Compression usually - but not always - increases the temperature, however.

    And there is no way to cause a simple sound wave (or pressure impulse) to travel faster than the speed of sound. Increasing the speed of sound in the medium will increase the speed of the sound wave, but it will still be limited by the new speed of sound. Unless that new speed of sound is faster than the plane, then the only thing that the increase in sound speed speed will do is make the conical shock have a larger half-angle.
     
  10. Aug 19, 2015 #9

    Nidum

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    This subject has been extensively researched since the 1940's .

    Very intensive research into specifically Concorde .

    Large amounts of information available .

    Here's a good read :

    http://www.nasa.gov/aero/centers_tackle_sonic_boom.html

    For much more just Google 'reducing sonic boom effects in aircraft'
     
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