Kinetic Bombardment — Real Sci-Fi Weapons
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How do you define a weapon? I would posit the following definition; a tool designed to multiply or direct force for the purpose of attacking another.
All weapons on earth seek to take force and apply it in such a way that its application becomes greater than an unaided action. As Archimedes said, “give me a lever long enough and a fulcrum on which to place it and I’ll move the world.” The club multiplies force, enabling a more effective strike for the same energy expended. The bow and arrow delivers energy via the drawing of a string, the lethal distance far exceeding the length of the draw. The firearm uses combined mechanical and chemical energy to multiply a simple trigger pull into an event that can kill from hundreds of yards away.
The most effective weapons are those which take the most advantage of the forces in our universe, for the benefit of the user. In this case, we’re talking about a universal and nearly inescapable force — gravity.
Gravity constantly exerts its force on all earthbound objects, pulling them tightly to the planet. If that force could be harvested, an extremely efficient weapon system could be created.
This is the idea behind the concept of kinetic bombardment — weaponry that gains all of its energy from kinetic impact can cause incredible damage without the effects of explosive, biological or nuclear weapons.
Robert Heinlein’s book The Moon is a Harsh Mistress demonstrates a hypothetical example of this. A lunar prison colony decides to declare and fight for its independence from the governments of earth. Equipped with an interplanetary launch system to send cargo back and forth, the people of Luna turn this into a platform for launching massive kinetic bombs at earth.
The idea has actually seen military use, and not just by trebuchets and catapults. “Lazy dog” bombs are relatively small fin-stabilized projectiles made out of steel. Dropped from a passing airplane, they blanket a wide area and can do considerable damage based off of kinetic energy alone. Concrete bombs have also been used to the same effect.
But perhaps the most infamous application of this idea is the concept of orbital kinetic bombardment. Sometimes referred to as “Rods from God”, plans were drawn up in the Cold War for satellite-borne weapons utilizing kinetic projectiles. The projectiles envisioned were the size of telephone poles, roughly 20 feet long and one foot in diameter.
These tungsten projectiles, with a mass of roughly 9 tons, are projected to be capable of reaching speeds of Mach 10 at the moment of impact, delivering energy equivalent to 11.5 tons of TNT. The projectiles imagined have a very slender, aerodynamic shape with stabilizing fins to increase sectional density, reducing drag and increasing the depth at which they could be used to strike. This is a similar design concept to super-dense, high energy kinetic rounds used in anti-tank weapons such as the APFDS (Armor piercing fin stabilizing discarding sabot) round.
A 2003 Air Force Report refers to these as hypervelocity rod bundles, and refers to their potential future capability to strike a target anywhere in the world from space. High sectional density and kinetic energy combined with a very high attack angle would make these hypothetical rod bundles particularly suited to striking hardened and buried targets with very little chance for effective countermeasures, without the long term environmental damage caused by nuclear weapons.
While kinetic energy weapons have been used, no form of this weapon has been tested from space — at least to public knowledge — and the application remains entirely hypothetical. One of the major obstacles to its implementation is the incredible cost of transporting such munitions into space, greatly exceeding the cost of comparatively powerful conventional explosives.
Massive projectiles launched from space. Stealthy and quiet, creating little signature which could alert any early warning system. Nuclear-equivalent explosions created solely from the power of Earth’s gravity. Nearly impossible to hide from anywhere on or underneath the earth. It’s little wonder a concept of this kind has earned such an awful name as “Rods from God.” While they are only real in the form of proposals and pre-production drawings currently, a weapon as fearsome as this may be employed on future battlegrounds.