XPost: sci.space.tech   
   From: ptrei@rsasecurity.com   
      
   Scott T. Jensen wrote:   
      
   > I'm up on the Space Station and I go out for a nice little space walk.  I   
   > take along my specially designed hunting rifle and fire a bullet down at the   
   > planet.  What would the bullet need to be made of for it to make it all the   
   > way to the surface and not burn up on entry to our atmosphere?  Is there   
   > anything the bullet could be made of that would be able it to make the trip?   
   > And would the speed of the bullet affect its chances?  Would also the bullet   
   > go weird like how bullets do when you shoot them into a pool of water?   
   >   
   > Idly curious,   
   > Scott Jensen   
      
   Since you are 'on the Space Station', your velocity relative to the   
   Earth is high (someone said 18000 mph). Rifle velocities are much   
   less, roughly 1000 - 1500 mph. This means that you can't   
   change the bullets velocity all that much compared to the ISS.   
      
   I'm not an expert on orbital mechanics, but I suspect that if you   
   fired in the proper direction (which may not be obvious), the   
   slug would eventually hit the atmosphere. It would still have   
   most of its orbital velocity, and come in at over 16000 mph.   
      
   A lead slug would almost certainly burn up. Some armor penetrating   
   rounds have steel or tungsten inserts. The tungsten ones would   
   have a much better chance of making it.   
      
   Whether it would skip off the atmosphere at first approach I can't   
   say. A lot depends on the angle of approach.   
      
   I'm not sure why you'd need a 'specially designed' rifle.   
   The vacuum is not an issue. Temperature and lubrication   
   might be. For these reasons a bolt action is probably   
   preferred.   
      
   Peter Trei   
      
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