An unguided bomb, also known as a free-fall bomb, gravity bomb, dumb bomb, or iron bomb, is an aircraft-dropped

bomb A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-transmitted mechan ...

(conventional or nuclear) that does not contain a

guidance system A guidance system is a virtual or physical device, or a group of devices implementing a controlling the movement of a ship, aircraft, missile, rocket, satellite, or any other moving object. Guidance is the process of calculating the changes in pos ...

and hence simply follows a

ballistic Ballistics may refer to: Science * Ballistics, the science that deals with the motion, behavior, and effects of projectiles ** Forensic ballistics, the science of analyzing firearm usage in crimes ** Internal ballistics, the study of the proce ...

trajectory A trajectory or flight path is the path that an object with mass in motion follows through space as a function of time. In classical mechanics, a trajectory is defined by Hamiltonian mechanics via canonical coordinates; hence, a complete tra ...

. It includes all aircraft bombs in general service until the latter half of

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, and the vast majority until the late 1980s, which were known simply as "bombs". Then, with the dramatically increased use of

precision-guided munition A precision-guided munition (PGM), also called a smart weapon, smart munition, or smart bomb, is a type of weapon system that integrates advanced guidance and control systems, such as Global Positioning System, GPS, laser guidance, or Infrared ...

s, a

retronym A retronym is a newer name for something that differentiates it from something else that is newer, similar, or seen in everyday life; thus, avoiding confusion between the two. Etymology The term ''retronym'', a neologism composed of the combi ...

was needed to separate "smart bombs" from free-fall bombs. "Dumb bomb" was used for a time, but many military circles felt it sounded trite, and eventually "gravity bomb" gained popularity. Bomb casings for unguided bombs are typically aerodynamic in shape, often with fins at the tail section, which reduce drag and increase stability after release, both of which serve to improve accuracy and consistency of trajectory. Unguided bombs typically use a

contact fuze A contact fuze, impact fuze, percussion fuze or direct-action (D.A.) fuze (''UK'') is the fuze that is placed in the nose of a bomb or shell so that it will detonate on contact with a hard surface. Many impacts are unpredictable: they may involve ...

for detonation upon impact, or some milliseconds after if a penetration effect is required. Alternatives include a fuze with an

altimeter An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. Ty ...

to cause an

air burst An air burst or airburst is the detonation of an explosive device such as an anti-personnel artillery shell or a nuclear weapon in the air instead of on contact with the ground or target. The principal military advantage of an air burst over ...

at the desired altitude, and a

proximity fuze A Proximity Fuse (also VT fuse or "variable time fuze") is a fuse that detonates an explosive device automatically when it approaches within a certain distance of its target. Proximity fuses are designed for elusive military targets such as air ...

to cause an air burst at a specific distance from the ground or other target.

Retarded bomb

The retarded bomb uses a mechanical method of creating increased

aerodynamic drag In fluid dynamics, drag, sometimes referred to as fluid resistance, is a force acting opposite to the direction of motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers, two solid surfaces, or b ...

, such as a

parachute A parachute is a device designed to slow an object's descent through an atmosphere by creating Drag (physics), drag or aerodynamic Lift (force), lift. It is primarily used to safely support people exiting aircraft at height, but also serves va ...

ballute The ballute (a portmanteau of ''balloon'' and ''parachute'') is a parachute-like braking device optimized for use at high altitudes and supersonic velocities. The original ballute configuration was invented in 1958 by the Goodyear Tire and Rubbe ...

, or drag-inducing petals. These deploy after the ordnance is released, slowing its fall and abbreviating its forward trajectory, giving the aircraft time to get clear of the blast zone when bombing from low altitudes or with nuclear ordnance. However, these bombs are less accurate than conventional free-fall bombs. Generally the high-drag tail replaces the low-drag so that the same bomb can be configured for either mode of attack during weapons preparation. High-drag bombs can also be dropped in low-drag mode if the pilot selects this option in the aircraft's weapon system, and will function exactly like a low-drag weapon.

References

{{Reflist Aerial bombs

Retarded bomb

See also

References