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I Supersonic bullet - drag

  1. Apr 4, 2017 #1
    I'm a computer scientist currently developing projectile simulators. My software will factor in drag coefficients of various shaped projectiles as well as gravity, air pressures, air density and temperatures at various heights. I am familiar with the drag formula but it's only useful up to Mach 0.8. Please help me understand what additional formulas I must use for speeds beyond Mach 0.8 in the thought experiment below:

    Assuming that a bullet is a perfect sphere like a musket ball fired out of a hypothetically long barrel tank type caliber musket with 100mm caliber with enough energy to send the ball to supersonic speeds at say mach 1.5 and the ball is a sphere: drag coefficient of 0.47.

    Assuming the ball leaves the barrel at mach 1.8 at an angle of 45 degrees, the ball will continue to slow down from supersonic to sub-sonic speeds.

    What formula should I use to calculate drag while the ball is still in supersonic speeds?
    What formula should I use to calculate drag while the ball slows to trans-sonic speeds?(mach 0.8-1.4)
    I'm assuming that once it slows down to mach 0.8 I can use the normal drag formula that factors in drag coefficient.
    Last edited: Apr 4, 2017
  2. jcsd
  3. Apr 5, 2017 #2


    Staff: Mentor

    What you're asking for is a quick course in engineering ballistics. We can't help much here with that.

    I would suggest finding a good book on the subject and do some self learning.

    Here's one such resource:


    Others might be found via Google searches.
  4. Apr 6, 2017 #3


    User Avatar

    Staff: Mentor

    And with jedi's helpful post, this thread is done. :smile:
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