From: lwcamp@gmail.com   
      
   On Thursday, August 25, 2016 at 3:33:52 PM UTC-7, MrAnderson wrote:   
   > So, I was thinking about effect of plasma hit on human. In my variation of   
   plasma weapon, plasma is tungstenium or any other heavy metal, flies at 200   
   km/s,   
      
   At 200 km/s, why bother making it a plasma?  At that speed, the kinetic energy   
   of a tungsten plug will be so large that trying to make it a plasma would add   
   essentially nothing to the amount of boom it makes at the other end.  For   
   comparison, the energy    
   density from the kinetic energy of an object at 200 km/s is close to the   
   energy density of the Little Boy nuclear explosive used to bomb the city of   
   Hiroshima.   
      
   At these speeds, the dynamic pressures acting on the projectile as it pushes   
   through its target are so much higher than any plausible material strength   
   that you can ignore material strength and treat the problem as a hydrodynamic   
   jet penetrating a fluid.    
    In this limit, you have a well known solution that the distance penetrated is   
   the length of the projectile times the square root of the ratio of the   
   projectile density to the target density   
   D = L sqrt(rho_p/rho_t).   
   So find the distance penetrated, then divvy up the 20 GJ/kg energy yield over   
   that length.  It will be messy.   
      
   Of course, the same principle also applies to the air the projectile is   
   passing through - ram pressure will ablate away the front of the projectile as   
   it passes through the atmosphere, resulting in a maximum range of about 130   
   times the projectile's    
   length for something with the density of tungsten in an earth-like atmosphere.   
      
   > and is squeezed by handwavium powerful magnetic "bubble", that works in   
   vacuum and atmosphere. So, except containing the plasma bolt, it's quite   
   possible, right?    
      
   Well, that bit about "except for containing the plasma bolt" is a biggie.  The   
   virial theorem is quite insistent about this.  I mean, except for gravity it's   
   quite possible I could fly, right?    
      
   I suppose there's always the approximation used in solid state physics of   
   treating metals as a free electron gas moving in the field of the average   
   background charge of the nuclei.  In that sense, any metal is a plasma   
   already, and you could just use    
   tungsten metal for your "plasma".  This, of course, makes modern-day firearms   
   into plasma bolt guns.   
      
   > Tungstenium is dense, bolt travels at high velocity, so can it give a   
   kinetic punch to target? If yes, how strong will it be? I don't know how dense   
   this plasma might be, need help with that. Bolt dimensions will be, let's say,   
   0.5cmx50cm cylinder.    
      
   You need to know how dense the plasma is to estimate effects.  Solid tungsten   
   is about 20 g/cm^3.  That would give your bolt a mass of about 200 g (so   
   either your magazine is very heavy, or you only get a few shots).  It would   
   explode with an energy    
   roughly equivalent to a ton of TNT from the kinetic energy alone.  The bolt   
   would penetrate about 2 m through meat and bone, so a 25 cm thick human would   
   only absorb about 1/8 of that energy.  It's still enough that they won't be   
   scraping him off the    
   sidewalk because there won't be much sidewalk left.   
      
   Discharge momentum would be about 40,000 N s, so a 100 kg human firing one of   
   these things would be sent flying back at 40 m/s from the recoil (that's   
   faster than freeway speed).  If the gun alone had a mass of 10 kg, recoil   
   energy would be 80 MJ, so    
   expect the gunner's shoulder and limb to be ripped straight off (and the butt   
   and action of the gun to be destroyed from the impact).  10 kg is really heavy   
   for a firearm, but the heavier it is the less the recoil energy so it is   
   fairly conservative.   
      
   Luke   
      
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