XPost: sci.space.science   
   From: JamesL@Lugoj.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?   
      
   The muzzle velocity of an M16 is ~ 950 m/sec (obviously not a hunting rifle   
   - unless you include humans in your hunting list). Firing straight down is   
   not be nearly as effective as you would think - much more effective is   
   firing "backward" against the direction of orbit. And counterintuitively   
   (unless one is familiar with orbital mechanics) the best place to fire   
   "backwards" is at the highest point in the orbit (the apogee). The worst   
   place to fire is at the lowest point in the orbit (the perigee). Obviously   
   in a nearly circular orbit it doesn't matter much when you fire.   
      
   The muzzle velocity of an M16 should be more than sufficient to drop a   
   bullet's perigee into the earth's atmosphere (for most low earth orbits of   
   interest) such that the orbit decays into the surface.   
      
   The speed of the bullet will probably be on the order of ~7000 m/sec as it   
   enters the atmosphere. A lead bullet probably wouldn't survive - but I   
   suspect a carbon-phenolic or silicon-dioxide (i.e. rock) bullet probably   
   should make it - or at least mostly.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)