Railgun--a Survey

choi

survey (n): "a broad treatment of a subject"
www.merriam-webster.com/dictionary/survey


Advanced weapons | Rail Strike; America’s navy wants to arm its ships with electrically powered superguns. Economist, May 9, 2015.
www.economist.com/news/science-a ... ered-superguns-rail

Quote:

“A single ship-launched missile can set the navy back well over $1m. Current estimates for railgun projectiles are around $25,000 per shot.

“the next challenge will be to work out a way to guide the projectiles, to permit accurate fire from a hundred miles’ distance.

Note:
(a) “FOR all [= despite] the centuries of refinement that separate a modern rifle from a Renaissance arquebus, the basic idea has not changed. That idea is to convert the chemical energy stored in an explosive into kinetic energy stored in a speeding projectile.”
(i) arquebus
en.wikipedia.org/wiki/Arquebus
([Modern] Dutch haakbus, meaning "hook gun" or "hook tube"/  muzzle-loaded; a matchlock firing action; smoothbore)
(A) A photo legend in this page talks about ba-jō-zutsu 馬上筒
en.wikipedia.org/wiki/Bajōzutsu
(B) The “tō” and “tsutsu” are Chinese and Japanese pronunciations of 筒. The first letter (in Japanese alphabet, I mean) of the latter was softened from “ts” to “z”--because now “tsutsu” is located not in the front, but the middle, of the combination word.
(ii) The m-w.com says “arquebus” is varaint of “harquebus.”

harquebus (n; Middle French harquebuse, arquebuse, modification of Middle Dutch hakebusse, from hake hook + busse tube, box, gun, from Late Latin buxis box)
www.merriam-webster.com/dictionary/harquebus

(b) Railguns are a staple of science fiction. The idea dates back to 1919, when a French inventor called André Louis Octave Fauchon-Villeplée filed a patent for an ‘Electric Apparatus for Propelling Projectiles.’ Unlike other sci-fi staples, such as laser blasters and particle-beam weapons, railguns are conceptually simple
As the name suggests, a railgun dispenses with the enclosed barrel employed by explosively propelled artillery in favour of a pair of electrically conductive rails (see diagram). This creates a linear electric motor. The motor’s moving part—its armature—sits between the rails and carries a projectile. When someone presses the trigger, current flows up one rail, through the armature and down the second rail. This generates a set of magnetic fields that accelerate the armature, and thus the projectile, forward along the rails and propel it out of the muzzle of the gun.

armature (n; Middle English, armor, from Latin armatura armor, equipment, from armatus)
www.merriam-webster.com/dictionary/armature

, where the “Middle English, armor” portion of the etymology means the word “armature” itself is Middle English, that means “armor,”
(c) “The brief given to the companies is to develop a weapon that can fire a 10kg projectile at about 2.5km a second. This is roughly seven times the speed of sound—and about three times the muzzle velocity of a conventional naval gun. At those sorts of speeds, there is no need to give the projectile a warhead. Its momentum is enough to cause destruction. The design has a muzzle energy of 32 megajoules, which is roughly the kinetic energy that would be carried by a small hatchback doing 900kph. The fiery plume, visible in the photograph, that accompanies the projectile out of the gun is not the result of propellant exploding but of the air itself being ionised by the electric current in the barrel.”

brief (n): "British  a set of instructions given to a person about a job or task"
www.oxforddictionaries.com/us/definition/english/brief

(d) “says Commander Jason Fox of Naval Sea Systems Command, the part of the navy responsible for railguns, the weapon offers three other advantages. One is range. The projectile’s speed means ships could attack other vessels, or bombard targets on land, from a distance of 110 nautical miles. That is much farther than existing naval guns can manage, and beyond the range of at least some shore-launched anti-ship missiles.
(i) nautical mile
en.wikipedia.org/wiki/Nautical_mile
(table 1 nm = 1.151 mile = 1.852km)

section 3 History: “The nautical mile was historically defined as a minute of arc along a meridian of the Earth (north-south), making a meridian exactly 180×60 = 10,800 historical nautical miles.

* Recall a meridian spans from North Pole to South Pole, through equator, composed 180 degrees. One degrees is made up of 60 minutes.
(ii) The narrowest part of Taiwan Strait is ~100 miles.