From: nuny@bid.nes   
      
   On Wednesday, February 7, 2018 at 8:04:44 PM UTC-8, nu...@bid.nes wrote:   
   > On Monday, February 5, 2018 at 10:31:29 PM UTC-8, timj...@gmail.com wrote:   
   > > The practical maximum length to diameter ratio in current long rod   
   > > projectiles is typically thought of as somewhere between 30:1 and   
   > > 40:1. If you were to scale up the projectile several times, could   
   > > the long rod maintain the same aspect ratio?   
   > >   
   > > e.g. If you had a 75cm length/2.5cm diameter long rod and scaled it   
   > > up 10x to 750cm/25cm, could it be expected to maintain the same degree   
   > > of rigidity during acceleration, flight, and impact?   
   > >   
   > > The "Rods from God" concept envisioned tungsten rods of 6.1m length   
   > > and 0.3m diameter, so at the very least they thought that a 20:1   
   > > aspect ratio was possible at that scale.   
   >   
   >   After seeing a video of an archer explaining how to account for arrow   
   > flex when doing precision target shooting (arrows greatly exceed 20:1),   
   > I think it's safe to say that there has to be a point of diminishing   
   > returns where real materials just aren't stiff enough. Where that point   
   > is I'm not sure but I will point out that given the fact that the RFG   
   > concept was never actually tried out we might discover that it doesn't   
   > scale up as far as we'd like it to.   
   >   
   >   What kinds of targets are you thinking of? Raw kinetic penetration   
   > should be applicable in any non-Star Trek/Wars "we have shields" scenario   
   > but I'm pretty sure scaling it up to kilometers-long relativistic   
   > penetrators for Really Big Ships won't work out unless the archer's   
   > tricks also scale up.   
      
     I should also mention that it can depend on how the rod is accelerated   
   and guided. Arrows are launched with force from the very aft end but with   
   no lateral stabilization during launch. That's why they flex (some bows   
   use a rest and their arrows flex vertically instead of side-to-side).   
      
     LRPs are usually saboted giving them 2D lateral stabilization during launch   
   but the RFG would be accelerated by gravity mostly. Perhaps a Great Big LRP   
   launched by a mass driver (rail/coilgun) wouldn't suffer flexing since the   
   whole thing would feel acceleration equally?   
      
      
      Mark L. Fergerson   
      
   --- SoupGate-Win32 v1.05   
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