G-90 Arrow of Artemis

A kinetic bombardment or a kinetic orbital strike is the hypothetical act of attacking a planetary surface with an inert projectile, where the destructive force comes from the kinetic energy of the projectile impacting at very high velocities. The concept is often encountered in science fiction[citation needed] and originated during the Cold War.

The typical depiction of the tactic is of a satellite containing a magazine of tungsten rods and a directional thrust system. When a strike is ordered, the satellite would brake[1] one of the rods out of its orbit and into a suborbital trajectory that intersects the target. The rod picks up speed as it approaches periapsis/ the target location due to gravity, picking up immense speed until it begins decelerating in the atmosphere and reaches terminal velocity shortly before impact. The rods would often be shaped so as to maximize terminal velocity. In science fiction, the tactic is often depicted as being launched from a spaceship, instead of a satellite.

Kinetic bombardment has the advantage of being able to deliver the projectiles from a very high angle at a very high speed, making them extremely difficult to defend against. In addition, projectiles would not require explosive warheads, and—in the simplest designs—would consist entirely of solid metal rods, giving rise to the common nickname "Rods from God". Disadvantages include the technical difficulties of ensuring accuracy and the prohibitively high cost of positioning ammunition in orbit.

The Outer Space Treaty prohibits weapons of mass destruction in orbit or outer space. However, the Outer Space Treaty only prohibits nuclear, biological, and chemical weapons. Since the most common form of kinetic ammunition is inert tungsten rods, in most cases, kinetic bombardment remains legal.

Real life concepts and theories

During the Vietnam War, there was limited use of the Lazy Dog bomb, a steel projectile shaped like a conventional bomb but only about 1" long and 3/8" diameter. A piece of sheet metal was folded to make the fins and riveted to the rear of the projectile. These were dumped from aircraft onto troops and had the same effect as a machine gun fired vertically. Observers visiting a battlefield after an attack said it looked like the ground had been 'tenderized' using a gigantic fork. Bodies had been penetrated longitudinally from shoulder to lower abdomen.[citation needed]

Project Thor is an idea for a weapons system that launches kinetic projectiles from Earth's orbit to damage targets on the ground. Jerry Pournelle originated the concept while working in operations research at Boeing in the 1950s before becoming a science-fiction writer.[4][5]

The system most often described is "an orbiting tungsten telephone pole with small fins and a computer in the back for guidance".[citation needed] The system described in the 2003 United States Air Force report[citation needed] was that of 20-foot-long (6.1 m), 1-foot-diameter (0.30 m) tungsten rods, that are satellite controlled, and have global strike capability, with impact speeds of Mach 10.

The time between deorbiting and impact would only be a few minutes, and depending on the orbits and positions in the orbits, the system would have a world-wide range. There is no requirement to deploy missiles, aircraft or other vehicles. Although the SALT II (1979) prohibited the deployment of orbital weapons of mass destruction, it did not prohibit the deployment of conventional weapons. The system is not prohibited by either the Outer Space Treaty or the Anti-Ballistic Missile Treaty.

The idea is that the weapon would inflict damage because it moves at orbital velocities, at least 9 kilometers per second. Smaller weapons can deliver measured amounts of energy as large as a 225 kg conventional bomb.[citation needed] Some systems are quoted as having the yield of a small tactical nuclear bomb.[8] These designs are envisioned as a bunker buster.

In the case of the system mentioned in the 2003 Air Force report above, a 6.1 m × 0.3 m tungsten cylinder impacting at Mach 10 has a kinetic energy equivalent to approximately 11.5 tons of TNT (or 7.2 tons of dynamite). The mass of such a cylinder is itself greater than 9 tons, so it is clear that the practical applications of such a system are limited to those situations where its other characteristics provide a decisive advantage—a conventional bomb/warhead of similar weight to the tungsten rod, delivered by conventional means, provides similar destructive capability and is a far more practical method. Some other sources suggest a speed of 36,000 ft/s (11,000 m/s),[11] which for the aforementioned rod would amount to a kinetic energy equivalent to 120 tons of TNT or 0.12 kt. With 6–8 satellites on a given orbit, a target could be hit within 12–15 minutes from any given time, less than half the time taken by an ICBM and without the warning. Such a system could also be equipped with sensors to detect incoming anti-ballistic missile-type threats and relatively light protective measures to use against them (e.g. Hit-To-Kill Missiles or megawatt-class chemical laser).

The highly elongated shape and high density are to enhance sectional density and therefore minimize kinetic energy loss due to air friction and maximize penetration of hard or buried targets. The larger device is expected to be quite good at penetrating deeply buried bunkers and other command and control targets.

The weapon would be very hard to defend against. It has a very high closing velocity and a small radar cross-section. Launch is difficult to detect. Any infrared launch signature occurs in orbit, at no fixed position. The infrared launch signature also has a small magnitude compared to a ballistic missile launch. One drawback of the system is that the weapon's sensors would almost certainly be blind during atmospheric reentry due to the plasma sheath that would develop ahead of it, so a mobile target could be difficult to hit if it performed any unexpected maneuvering. The system would also have to cope with atmospheric heating from re-entry, which could melt non-tungsten components of the weapon.

The phrase "Rods from God" is also used to describe the same concept. An Air Force report called them "hypervelocity rod bundles".


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A kinetic energy penetrator (KE weapon; also a long-rod penetrator or LRP) is a type of ammunition designed to penetrate vehicle armour which, like a bullet, does not contain explosives and uses kinetic energy to penetrate the target. Modern KE weapons are typically of the armour-piercing fin-stabilized discarding-sabot (APFSDS) type.
History
A partially cut-away 30 x 173 mm APFSDS-T round

Early cannons fired kinetic energy ammunition, initially consisting of round balls of worked stone and later of round balls of metal. From the beginning, combining high muzzle energy with projectile density and hardness have been the foremost factors in the design of such weapons. Similarly, the foremost purpose of such weapons has generally been to defeat armour or other defensive structures, whether stone castle walls, ship timbers, or modern tank armour. Kinetic energy ammunition, in its various forms, has consistently been the choice for those weapons due to the need for high muzzle energy.

The development of the modern KE penetrator combines two aspects of artillery design: high muzzle velocity and concentrated force. High muzzle velocity is achieved by using a projectile with a low mass and large base area in the gun barrel. Firing a small size projectile wrapped in a lightweight outer shell, called a sabot, raises the muzzle velocity. Once the shell clears the barrel, the sabot is no longer needed and falls off in pieces. This leaves the projectile traveling at high velocity with a smaller cross-sectional area and reduced aerodynamic drag during the flight to the target (see external ballistics and terminal ballistics). Germany developed modern sabots under the name "treibspiegel" ("thrust mirror") to give extra altitude to its anti-aircraft guns during the Second World War. Before this, primitive wooden sabots had been used for centuries in the form of a wooden plug attached to or breech loaded before cannonballs in the barrel, placed between the propellant charge and the projectile. The name "sabot" (sah-BOTT) is the French word for clog (a wooden shoe traditionally worn in some European countries).

Concentration of force into a smaller area was initially attained by replacing the single metal (usually steel) shot with a composite shot using two metals, a heavy core (based on tungsten) inside a lighter metal outer shell. These designs were known either as armour piercing composite rigid (APCR), high velocity armor-piercing (HVAP) and "hartkern" (hard core) (resp. by the British, US and Germans). On impact, the core had a much more concentrated effect than plain metal shot of the same weight and size. However, the air resistance and other effects were the same as for the shell of identical size.

Between 1941 and 1943, the British combined the two techniques in the armour-piercing discarding sabot (APDS) round. The sabot replaced the outer metal shell of the APCR. While in the gun the shot had a large base area to get maximum acceleration from the propelling charge but once outside, the sabot fell away to reveal a heavy shot with a small cross-sectional area. High velocity armor piercing (HVAP) rounds were also introduced by the United States Army, and were primarily used by tank destroyers.
Design

The principle of the kinetic energy penetrator is that it uses its kinetic energy, which is a function of its mass and velocity, to force its way through armor. If the armor is defeated, the heat and spalling (particle spray) generated by the penetrator going through the armor, and the pressure wave that would develop, ideally destroys the target.[1]

The modern kinetic energy weapon maximizes the stress (kinetic energy divided by impact area) delivered to the target by:

    maximizing the mass - that is, using the densest metals practical, which is one of the reasons depleted uranium or tungsten carbide is often used - and muzzle velocity of the projectile, as kinetic energy scales with the mass m and the square of the velocity v of the projectile \left(\frac{1}{2}mv^2\right)
    minimizing the width, since if the projectile does not tumble, it will hit the target face first; as most modern projectiles have circular cross-sectional areas, their impact area will scale with the square of the radius r (the impact area being \pi r^2)

This has led to the current designs which resemble a long metal arrow.

The opposite technique to KE-penetrators uses chemical energy penetrators. There are two types of these shells in use: high explosive anti-tank (HEAT) and high explosive squash head (HESH). They have been widely used against armour in the past and still have a role but are less effective against modern composite armour, such as Chobham as used on main battle tanks today. Main battle tanks usually use KE-penetrators, while HEAT is mainly found in missile systems that are shoulder-launched or vehicle-mounted, and HESH is usually favored for fortification demolition.