depressed trajectory

A ballistic missile is a type of missile that uses projectile motion to deliver warheads on a target. These weapons are powered only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles (SRBM) typically stay within the Earth's atmosphere, while most larger missiles travel outside the atmosphere. The type of ballistic missile with the greatest range is an intercontinental ballistic missile (ICBM). The largest ICBMs are capable of full orbital flight.

These missiles are in a distinct category from cruise missiles, which are aerodynamically guided in powered flight and thus restricted to the atmosphere.

History

One modern pioneer ballistic missile was the A-4, commonly known as the V-2, developed by Nazi Germany in the 1930s and 1940s under the direction of Wernher von Braun. The first successful launch of a V-2 was on October 3, 1942, and it began operation on September 6, 1944, against Paris, followed by an attack on London two days later. By the end of World War II in Europe in May 1945, more than 3,000 V-2s had been launched. In addition to its use as a weapon, a vertically launched V-2 became the first human-made object to reach outer space on June 20, 1944.

The R-7 Semyorka was the first intercontinental ballistic missile.

The largest ballistic missile attack in history took place on 1 October 2024 when the Iranian Revolutionary Guard launched about 200 missiles at Israel, a distance of about 1,500 kilometers. The missiles arrived about 15 minutes after launch. It is believed that Iran's Fattah-1 and Kheybar Shekan missiles were used, which both have a range of about 1,400 km.

Flight

In order to cover large distances, ballistic missiles are usually launched into a high sub-orbital spaceflight; for intercontinental missiles, the highest altitude ( apogee) reached during free-flight is about . A ballistic missile's trajectory consists of three parts or phases: the boost phase, the mid-course phase and the terminal phase. Special systems and capabilities are required to facilitate the successful passage from one phase to the other.

The boost phase is the powered flight portion, beginning with the ignition of the engines and concluding with the end of powered flight. The powered flight portion can last from a few tenths of seconds to several minutes and can consist of multiple rocket stages. Internal computers keep the missile aligned on a preprogrammed trajectory. On multi-stage missiles, stage separation (excluding any post-boost vehicles or MIRV bus) occurs primarily during the boost phase.

The mid-course phase is the longest in the missile's trajectory, beginning with the conclusion of powered flight. When the fuel is exhausted, no more thrust is provided and the missile enters free flight. During this phase the missile, now largely consisting of a warhead or payload and possibly defensive countermeasures and small propulsion systems for further alignment toward its target, will reach its highest altitude and may travel in space for thousands of kilometres (or even indefinitely, in the case of some fractional-orbital capable systems) at speeds of up to .

The last phase in the missile's trajectory is the terminal or re-entry phase, beginning with the re-entry of the missile into the Earth's atmosphere (if exoatmospheric) where atmospheric drag plays a significant part in missile trajectory, and lasts until missile impact. Re-entry vehicles re-enter the Earth's atmosphere at very high velocities, on the order of at ICBM ranges. During the beginning of this phase, the missile's trajectory is still relatively well defined, though as the missile reaches the heavier layers of atmosphere it is increasingly influenced by gravity and aerodynamic drag, which can affect its landing.

Types

Ballistic missiles can be launched from fixed sites or mobile launchers, including vehicles (e.g., transporter erector launchers), aircraft, ships, and submarines. Ballistic missiles vary widely in range and use, and are often divided into categories based on range. Various schemes are used by different countries to categorize the ranges of ballistic missiles:

*Tactical ballistic missile (TBM): Range less than 300 km
* Short-range ballistic missile (SRBM): Range from
*Medium-range ballistic missile (MRBM): Range from
*Intermediate-range ballistic missile (IRBM): Range from
*Intercontinental ballistic missile (ICBM): Range greater than

Long- and medium-range ballistic missiles are generally designed to deliver nuclear weapons because their payload is too limited for conventional explosives to be cost-effective in comparison to conventional bomber aircraft.

Quasi-ballistic missiles

A quasi-ballistic missile is a category of SRBM that is largely ballistic but can perform maneuvers in flight or make unexpected changes in direction and range. Large guided MLRS rockets with range comparable to an SRBM are sometimes categorized as quasi-ballistic missiles.

List of quasi-ballistic missiles

;

* Shaurya (active)
* Pralay (active)
;
* LORA (active)
;
* MGM-140 ATACMS (active)
* Precision Strike Missile (active)

Hypersonic ballistic missile

Many ballistic missiles reach hypersonic speeds (i.e. Mach 5 and above) when they re-enter the atmosphere from space. However, in common military terminology, the term "hypersonic ballistic missile" is generally only given to those that can be maneuvered before hitting their target and don't follow a simple ballistic trajectory.

Throw-weight

Throw-weight is a measure of the effective weight of ballistic missile payloads. It is measured in kilograms or tonnes. Throw-weight equals the total weight of a missile's warheads, reentry vehicles, self-contained dispensing mechanisms, penetration aids, and any other components that are part of the delivered payload, and not of the rocket itself (such as the launch rocket booster and launch fuel). Throw-weight may refer to any type of warhead, but in normal modern usage, it refers almost exclusively to nuclear or thermonuclear payloads. It was once also a consideration in the design of naval ships and the number and size of their guns.

Throw-weight was used as a criterion in classifying different types of missiles during Strategic Arms Limitation Talks between the Soviet Union and the United States. The term became politically controversial during debates over the arms control accord, as critics of the treaty alleged that Soviet missiles were able to carry larger payloads and so enabled the Soviets to maintain higher throw-weight than an American force with a roughly comparable number of lower-payload missiles.

The missiles with the world's heaviest payloads are the Russian SS-18 and Chinese CSS-4 and , Russia was developing a new heavy-lift, liquid-propellant ICBM called the Sarmat.

Depressed trajectory

Throw-weight is normally calculated using an optimal ballistic trajectory from one point on the surface of the Earth to another. A "minimum-energy trajectory" maximizes the total payload (throw-weight) using the available impulse of the missile. By reducing the payload weight, different trajectories can be selected, which can either increase the nominal range or decrease the total time in flight.

A depressed trajectory is non-optimal, as a lower and flatter trajectory takes less time between launch and impact but has a lower throw-weight. The primary reasons to choose a depressed trajectory are to evade anti-ballistic missile systems by reducing the time available to shoot down the attacking vehicle (especially during the vulnerable burn-phase against space-based ABM systems) or a nuclear first-strike scenario. An alternate, non-military purpose for a depressed trajectory is in conjunction with the spaceplane concept with use of airbreathing jet engines, which requires the ballistic missile to remain low enough inside the atmosphere for air-breathing engines to function.

In contrast, a "lofted" trajectory is frequently used for testing purposes, as it reduces the range of the missile (allowing for a controlled and observed impact), as well as signals a lack of hostile intention with the test.

Combat use

The following ballistic missiles have been used in combat:

* Ghadr-110
* LORA
* MGM-140 ATACMS
* OTR-21 Tochka
* Qaher-1/2M
* Scud
* V-2
* Zolfaghar
* Kh-47M2 Kinzhal
* Oreshnik

See also

* MIRV
*NATO reporting name (has lists of various Soviet missiles)
* Surface-to-surface missile
*Weapons of mass destruction
* List of currently active missiles of the United States military
* List of ICBMs
* List of missiles
* List of missiles by nation
* List of NATO reporting names for ballistic missile submarines
* Missile guidance

Notes

References

*Needham, Joseph (1986). ''Science and Civilization in China: Volume 5, Chemistry and Chemical Technology, Part 7, Military Technology; the Gunpowder Epic''. Taipei: Caves Books.

Further reading

* Bath, David W. ''Assured Destruction: Building the Ballistic Missile Culture of the U.S. Air Force'' (Naval Institute Press, 2020
online book review
*
*
*

External links

Missile Threat
A Project of the Center for Strategic and International Studies

{{Authority control

Chinese inventions
German inventions of the Nazi period
Wernher von Braun