The breaking the sound barrier thread

Discussion in 'Defence & Strategic Issues' started by Sailor, May 22, 2009.

  1. Sailor

    Sailor Regular Member

    Joined:
    Apr 19, 2009
    Messages:
    591
    Likes Received:
    5
    Breaking the sound barrier

    At sea level a plane must exceed 741 mph to break the sound barrier, or the speed at which sound travels.

    The change in pressure as the plane outruns all of the pressure and sound waves in front of it is heard on the ground as an explosion or sonic boom. The pressure change condenses the water in the air as the jet passes these waves. Altitude, wind speed, humidity, the shape and trajectory of the plane - all of these affect the breaking of this barrier. The slightest drag or atmospheric pull on the plane shatters the vapor oval like fireworks as the plane passes through.

    Check out this F-18 Hornet video.
    YouTube - F18 hornet

    Here is my collection of photos of various aircraft breaking the sound barrier. The photos capture the moment.
    Add you favorite aircraft here.

    F-18 Hornet
    [​IMG]

    F-8 Crusader
    [​IMG]

    F-22 Raptor
    [​IMG]

    F-14 Tomcat
    [​IMG]

    B-2 Nighthawk
    [​IMG]

    and just to show the Brylcream boys they can do it, a B-52.
    [​IMG]

    B-1B Lancer
    [​IMG]
     
  2.  
  3. Soham

    Soham DFI TEAM Senior Member

    Joined:
    Mar 22, 2009
    Messages:
    1,972
    Likes Received:
    70
    Good pics Sailor. Funny to watch a Buff in the midst of the sonic boom.
    Just one question,
    You said :
    The speed of sound remains the same anywhere in air, then why the mention of Sea level ?
     
  4. Auberon

    Auberon Regular Member

    Joined:
    Mar 25, 2009
    Messages:
    275
    Likes Received:
    3
    Air is a mixture of gases, air itself is not the same everywhere, density, temp., composition etc varies, all have an effect on the speed of sound.
     
  5. Sailor

    Sailor Regular Member

    Joined:
    Apr 19, 2009
    Messages:
    591
    Likes Received:
    5
    Because the air gets colder as you go higher. The toughest reading for an aircraft is at sea level and the official measurement is taken there..

    Table: The impact of temperature on the speed of sound

    −25 315.7 Speed of sound c in m/s
    −20 318.9
    −15 322.0
    −10 325.2
    −5 328.2
    0 331.3
    5 334.3
    10 337.3
    15 340.3
    20 343.3
    25 346.2
    30 349.1
    35 352.0

    With the following formula you can calculate more exactly the speed of sound.

    Speed of sound Schall in m/s; temperature Vartheta in °C

    The speed of sound c depends on the temperature of air and not on the air pressure!
    The humidity of air has some negligible effect on the speed of sound. The air pressure
    and the density of air (air density) are proportional to each other at the same temperature.
    It applies always p / ρ = constant. rho is the density ρ and p is the sound pressure.
     
  6. Soham

    Soham DFI TEAM Senior Member

    Joined:
    Mar 22, 2009
    Messages:
    1,972
    Likes Received:
    70
    Oh yes... Thank you for the clarification. T'was but a silly question.
     
  7. Sailor

    Sailor Regular Member

    Joined:
    Apr 19, 2009
    Messages:
    591
    Likes Received:
    5
    It was a good question Sol. It is from such questions that things are learnt.
    I wonder how many here knew about temperature and air pressure in relation to the speed of sound?
     
  8. Known_Unknown

    Known_Unknown Devil's Advocate Stars and Ambassadors

    Joined:
    Apr 21, 2009
    Messages:
    2,632
    Likes Received:
    1,664
    Location:
    Earth
    Nice pics! Feels like the Starship Enterprise coming out of warp speed.
     
  9. prahladh

    prahladh Respected Member

    Joined:
    Apr 20, 2009
    Messages:
    864
    Likes Received:
    144
    Location:
    Universal Citizen
    Do passenger planes experience sonic booms, because they travel at way more than 740mph?
     
  10. Sailor

    Sailor Regular Member

    Joined:
    Apr 19, 2009
    Messages:
    591
    Likes Received:
    5
    Only the Concorde and the Tu-144 have flown at speeds exceeding the sound barrier Rimser. These were designed to do it.
    The Boeing 747 for instance flies at around mach .85 with a top speed of mach.92
     
  11. prahladh

    prahladh Respected Member

    Joined:
    Apr 20, 2009
    Messages:
    864
    Likes Received:
    144
    Location:
    Universal Citizen
    Thanks sailor.
    When I was on cathay pacific they showed a speed of 1225kmph which is mach1 I guess enough for a boom ?
    Am I right!
     
  12. Sailor

    Sailor Regular Member

    Joined:
    Apr 19, 2009
    Messages:
    591
    Likes Received:
    5
    Rimser, all I can say is that you got that wrong. It isn't possible. I have had uncountable international flights and the fastest I ever saw on the screen monitor was 1005kph.
     

Share This Page