Intercontinental ballistic missile

Modern ICBMs typically carry multiple independently targetable reentry vehicles (MIRVs), each of which carries a separate nuclear warhead, allowing a single missile to hit multiple targets. MIRV was an outgrowth of the rapidly shrinking size and weight of modern warheads and the Strategic Arms Limitation Treaties (SALT I and SALT II), which imposed limitations on the number of launch vehicles. It has also proved to be an "easy answer" to proposed deployments of anti-ballistic missile (ABM) systems: It is far less expensive to add more warheads to an existing missile system than to build an ABM system capable of shooting down the additional warheads; hence, most ABM system proposals have been judged to be impractical. The first operational ABM systems were deployed in the United States during the 1970s. The Safeguard ABM facility, located in North Dakota, was operational from 1975 to 1976. The Soviets deployed their ABM-1 Galosh system around Moscow in the 1970s, which remains in service. Israel deployed a national ABM system based on the Arrow missile in 1998,^[30] but it is mainly designed to intercept shorter-ranged theater ballistic missiles, not ICBMs. The Alaska-based United States national missile defense system attained initial operational capability in 2004.^[31]


ICBMs can be deployed from multiple platforms:


The last three kinds are mobile and therefore hard to detect prior to a missile launch. During storage, one of the most important features of the missile is its serviceability. One of the key features of the first computer-controlled ICBM, the Minuteman missile, was that it could quickly and easily use its computer to test itself.


After launch, a booster pushes the missile and then falls away. Most modern boosters are Solid-propellant rocket motors, which can be stored easily for long periods of time. Early missiles used liquid-fueled rocket motors. Many liquid-fueled ICBMs could not be kept fueled at all times as the cryogenic fuel liquid oxygen boiled off and caused ice formation, and therefore fueling the rocket was necessary before launch. This procedure was a source of significant operational delay and might allow the missiles to be destroyed by enemy counterparts before they could be used. To resolve this problem Nazi Germany invented the missile silo that protected the missile from Strategic Bombing and also hid fueling operations underground.


Although the USSR/Russia preferred ICBM designs, that use hypergolic liquid fuels, which can be stored at room temperature for more than a few years.


Once the booster falls away, the remaining "bus" releases several warheads, each of which continues on its own unpowered ballistic trajectory, much like an artillery shell or cannonball. The warhead is encased in a cone-shaped reentry vehicle and is difficult to detect in this phase of flight as there is no rocket exhaust or other emissions to mark its position to defenders. The high speeds of the warheads make them difficult to intercept and allow for little warning, striking targets many thousands of kilometers away from the launch site (and due to the possible locations of the submarines: anywhere in the world) within approximately 30 minutes.


Many authorities say that missiles also release aluminized balloons, electronic noisemakers, and other decoys intended to confuse interception devices and radars.


As the nuclear warhead reenters the Earth's atmosphere, its high-speed causes compression of the air, leading to a dramatic rise in temperature which would destroy it, if it were not shielded in some way. In one design, warhead components are contained within an aluminium honeycomb substructure, sheathed in a pyrolytic carbon-epoxy synthetic resin composite material heat shield. Warheads are also often radiation-hardened (to protect against nuclear armed ABMs or the nearby detonation of friendly warheads), one neutron-resistant material developed for this purpose in the UK is three-dimensional quartz phenolic.


Circular error probable is crucial, because halving the circular error probable decreases the needed warhead energy by a factor of four. Accuracy is limited by the accuracy of the navigation system and the available geodetic information.


Strategic missile systems are thought to use custom integrated circuits designed to calculate navigational differential equations thousands to millions of FLOPS in order to reduce navigational errors caused by calculation alone. These circuits are usually a network of binary addition circuits that continually recalculate the missile's position. The inputs to the navigation circuit are set by a general-purpose computer according to a navigational input schedule loaded into the missile before launch.


One particular weapon developed by the Soviet Union – the Fractional Orbital Bombardment System – had a partial orbital trajectory, and unlike most ICBMs its target could not be deduced from its orbital flight path. It was decommissioned in compliance with arms control agreements, which address the maximum range of ICBMs and prohibit orbital or fractional-orbital weapons. However, according to reports, Russia is working on the new Sarmat ICBM which leverages Fractional Orbital Bombardment concepts to use a Southern polar approach instead of flying over the northern polar regions. Using that approach, it is theorized, avoids the American missile defense batteries in California and Alaska.


New development of ICBM technology are ICBMs able to carry hypersonic glide vehicles as a payload such as RS-28 Sarmat.


In March 12 2024 India announced that it had joined a very limited group of countries, which are capable of firing multiple warheads on a single ICBM. The announcement came after successfully testing multiple independently targetable reentry vehicle (MIRV) technology.^[32]