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Calculate Rate of Disintegration of Projectile

  1. Jan 20, 2013 #1
    I was thinking about meteorioids and how upon their entry into the atmosphere the large amount of disintegration they experience so i wanted to try running through a calculation of something similar to see if i could i understand it better. I'm going to outline a general thought process I've come up with then ask a specific case.
    Ignoring gravity or the existance of a floor for now because of the complications that would cause.

    Lets say we have a [insert size and mass/density here] [insert shape name here] of [insert material here] [falls apart/does not fall apart] and we fire it at [insert velocity here].
    How [long or far] will it travel before the object fully disintegrates?
    How [much mass/volume] is lost before the object stops disintegrating.

    Lets say we have a 1 meter radius sphere of iron (density 7.874 g·cm−3) in 1 atm air. We assume it does not fall apart or explode in it's transit. We fire it at 100 km/s, how much mass does the object lose in its transit.
  2. jcsd
  3. Jan 20, 2013 #2


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    Not a simple problem. The interactions between the projectile and the air as it is traveling at hypervelocity do not lend themselves, IMO, to analysis by a couple of simple formulas.
  4. Jan 20, 2013 #3
    Im not really interested in a simple formula as much as trying to piece together information to come up with more information and more formulas. I'm interested in the journey for this calculation, not so much the end product.

    As more variables are introduced I want to see what you have to consider and what doesnt matter.
  5. Jan 20, 2013 #4


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    If you're thinking about meteorites hitting the earth....
    You could start by assuming that the entire kinetic energy of the projectile is converted into heat. That's a pretty good approximation for the total energy released.
  6. Jan 20, 2013 #5
    I was more interested in learning about the rate of disintegration, distances traveled, heats experienced, and just about different factors that need to be considered and how each of them would likely be playing out as per the relevant formulas .
    Last edited: Jan 21, 2013
  7. Jan 21, 2013 #6


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    What fates may befall the material? Combustion, evaporation, thermal cracking, explosion... Rate of heating will matter, since rapid external heating would create greater stresses. Conductivity. Spin?
  8. Jan 21, 2013 #7
    For now lets assume the particle does not fracture into macroscopic fragments. Should a fate like that befall it then instead the methodology we create here can instead be reapplied for the fragments in question (with a lot of new variables that is).

    How would one be able to determine the heat gained from air friction?

    Also how would one be able to determine the transfer of heat into the "cooler" center of the sphere?

    Obviously thermal conductivity comes to play a very large role here but even if the conductivity high is would it effect disintegration in the first (maybe few) second(s) at some non-negligible amount?
    Last edited: Jan 21, 2013
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