Ballistic missile

U.S. Navy Polaris ballistic missile on the pad in Cape Canaveral, Florida, U.S.A., circa 1964. CREDIT: Public domain

A ballistic missile is a guided missile, of much greater range than that of artillery, that follows a generally parabolic trajectory, as adjusted by guidance and control mechanisms, from launching point to target. In most cases, the trajectory is suborbital, spending at least part of its flight in outer space, but not going into orbit. The World War II German V-2 ballistic missile was the first used in warfare. Ballistic missiles have been a part of modern warfare, starting with the Germans bombing London during World War II, and have given human beings the opportunity to wage global nuclear war and create vast destruction from a distance. Starting in the early 1970s, their deployment became subject to a number of international treaties designed to limit the destruction of a nuclear war.

Ballistic conveys the idea that the basic energy is imparted, usually by a rocket motor or motors (i.e., multiple stages, during the initial boost phase rising to the edge of space. It then goes into a midcourse where it coasts ballistically subject to guidance. During the midcourse, several reentry vehicles can separate for fixed reentry (i.e., multiple reentry vehicle (MRV)), or they can be fired as multiple independently-targetable reentry vehicles (MIRV) onto a final path by a midcourse bus, which can align itself, essentially above the atmosphere, so reentry vehicles are on a specific trajectory. In many short-range ballistic missiles, the entire missile remains intact until the warhead detonates.

Midcourse is followed by atmospheric reentry, which can be affected by the aerodynamics of the reentry vehicle, the way in which it deals with the sometimes extreme heating of atmospherics, and other environmental affects near the target. Most reentry vehicles are essentially pure ballistic, although some advanced types have had aerodynamic controls or internal weights that allow them to be maneuvering reentry vehicles (MARV). As a result of arms control agreements, Soviet and U.S. land-based long-range missiles no longer have MIRVs, and MARVs were never deployed. U.S. Pershing II missiles were to have a MARV, and were a sufficient threat that not deploying them became an important "bargaining chip" in the Intermediate Range Forces (INF) treaty.

In the early 21st-century, a new international arms race has developed involving the use of hypersonic glide vehicles, sometimes launched from ballistic missiles. A hypersonic glide vehicle is a type of warhead for ballistic missiles that can maneuver and glide at hypersonic speed, in other words, many times the speed of sound at velocities of Mach 5 and greater. It can be used in conjunction with ballistic missiles to significantly change their trajectories after launch, allowing a weapon that theoretically is harder to detect by defensive forces. As of 2024, countries developing and testing these weapons include China, India, France, Russia, North Korea, Japan, and the United States.

The launching system

Early ballistic missiles were exposed to attack, on the surface, originally for up to several hours of fueling with cryogenic liquid propellants. Even a single bullet might significantly damage the missile before launch.

Survivability increased when the missiles could be fueled while underground, and then increased significantly when they started to use storable liquid propellants that did not require hours of preparation. Still, the storable propellants tended to be hypergolic, or igniting on contact; again, there was extreme vulnerability to physical damage. In one memorable case, on 19 September 1980, a U.S. Titan II missile crewman, working on a missile in an open silo at Little Rock Air Force Base in Arkansas, dropped a socket wrench weighing perhaps one pound, into the silo, where it hit the outer skin of the fueled rocket at approximately 6:30 PM. The crew treated the incident seriously, for the propellants are highly toxic aside from the other dangers. At approximately 3 AM the next morning, the rocket exploded, killing 1, injuring 23, and hurling a warhead several hundred feet away. The nuclear weapon demonstrated its safeguards by not partially or fully detonating.

Later, solid propellant missiles such as the LGM-30 Minuteman had a stable solid propellant. Reportedly, it could be launched 32 seconds after receiving a valid order, although it would take longer for that order to get from the National Command Authority to the launch crew. The problem remained, however, as missile warheads became more and more accurate, that land-based intercontinental ballistic missiles (ICBMs) were increasingly vulnerable, thus encouraging "use it or lose it" and ultimately being destabilizing.

Various schemes of making the ICBMs more survivable through mobility, perhaps on special railroads within a military base, proved impractical. It made more sense to move the missiles to submarines, especially when submarine-launched missiles had sufficient range to launch from well-guarded waters.

Guidance

Guidance for the boost and midcourse phases is usually inertial, utilizing devices such as gyroscopes, although some systems also use celestial guidance.

Payloads

The total payload, or throw-weight, of a missile includes both the actual destructive material of the warhead(s), but also ballistic missile penetration aids that confuse a defense as to which reentering objects are the truly dangerous warheads. Payload weight assigned to penetration aids has to be traded against weight allocated to guidance or to actual warheads; the optimal distribution was being researched from the very first days of ballistic missiles. If increased guidance system weight can make warhead delivery more accurate, smaller warheads can be used.

Warheads

Nuclear warheads have been most common for longer-range ballistic missiles. Some short-range missiles may have high explosive or cluster bomblet warheads, but unless the reentry vehicle is extremely accurate, may be psychological weapons.

Some chemical warheads, often as bomblets, have been demonstrated. Biological warheads are rumored but not confirmed; they may have been destroyed.

The reentry speed of an ICBM is so great that the reentry vehicle can be filled with concrete for a fixed target, or metal rods for an area target; the kinetic energy of the warhead is so great that a conventional explosive filling would add no appreciable energy.

Penetration aids

Confusing the defense can have effects on two levels. If the target nation has ballistic missile defense, penetration aids will make the problem of intercepting the true warheads much more difficult. Devices flying along with the missile, to increase the difficulty of identifying the true warheads, are called penetration aids. Penetration aid technology is difficult, and harder for a nation to achieve that to acquire the missiles or technology limited by the Missile Technology Control Regime (MCTR).

It sometimes is difficult to draw the line between penetration aids and warheads. Indeed, the real warheads may be configured to resemble a decoy, and vice versa.

Historical deployment and use

Soviet R-12 missile of type deployed to Cuba during the Cold War

Ballistic missiles were first used as weapons during World War II, by the German forces, who bombed London from a distance with V-2 ballistic missiles armed with conventional high explosives. Later, ballistic missiles were often armed with nuclear warheads, but to date these have never used in battle. The Cuban missile crisis of 1962 was over the deployment of Soviet R-12 Dvina intermediate-range nuclear ballistic missiles staged in Cuba within striking range of the continental United States. High-explosive warhead Scud ballistic missiles were used in the Iran–Iraq war of the 1980s, by both Iran and Iraq, and also in the U.S.-led Gulf War conflict of early 1991, by Iraq against Coalition Forces, Israel, and Saudi Arabia.