Thursday, February 9, 2017

Technical problems with Sci-Fi weapons

"Hey, I think I see what the problem is."  One problem with being an engineer is that I over-think things.
I have been enjoying Mil-Science Fiction.  I have a couple of dandy authors who write books in that genre on my side-bar (Old NFO and Bayou Renaissance Man).  This post is not about them.  It is about me.  Life is often more enjoyable when we don't over-think things.

Typical prose
"Twisting through the air like a cat, our hero launched a stream of shots from his 1mm, depleted uranium handgun.  The projectiles lanced through the air leaving bright, silvery streaks as they raced toward the enemy at .3 times the speed of light."

I'll bet he was twisting through the air
A 1.0mm diameter bead of depleted uranium weighs about 0.15 grains.  As a frame of reference, a single pellet of #9 bird shot weighs about 0.75 grains and the ubiquitous .22LR projectile most often weighs 40 grains.

Looking at momentum, which is mass-times-velocity:
  • .22LR = 7 lbm-fps
  • .308 FMJ = 57 lbm-fps
  • 12 gauge high brass = 93 lbm-fps
  • 1.0mm Bead rifle DU round, 0.3C = 6500 lbm-fps
  • 1.0mm Bead rifle steel round , 0.3C= 2700 lbm-fps
  • 1.0mm Bead rifle glass round, 0.3C = 960 lbm-fps
What does 6500 lbm-fps mean?

"After firing his first shot, our muscular, 170 pound, movie-star handsome hero (coincidentally named Joe) is instantaneously accelerated to 26 miles per hour."

Yeah, that will make him hard to hit...assuming he can hang onto his pistol without breaking his arm.
Hematoma caused by firing an elephant gun
And his rail-gun that shoots the 3mm bead?  A single shot has enough momentum to launch our hero backwards at 1030 mph. I bet that leaves a bruise.

The Engineering Solution
The Engineering solution is as old as the Pharaohs:  An Intertia Well known as an "Administrice" is embedded in the gun's stock.  Everything is stopped by an administrice...except maybe "the buck".

A simple representation of an Administrace...a simple interia well consisting of a Bureaucratic Cluster encapsulated by multiple layers of Clerkium.
Theoretical Mathematicians are not in full agreement where the inertia goes.

Some of the more radical T.M.s believe that it tunnels through to parallel universes and the energy becomes Entrepreneurial Spirit.  It works for me.  Obviously the more Administrace in a society the less Entrepreneurial Spirit it has.


  1. LOL, I actually 'try' to make mine believable, as you know... :-D

  2. OBTW, looking at the painting of the longboat, it's 'technically' in irons with the wind directly off the beam. It 'might' be able to move a .25kts, but would have to turn 30-90 degrees left to get the wind.