A
bomb is any of a range of explosive devices that
typically rely on the
exothermic chemical reaction of an
explosive material to produce an
extremely sudden and violent release of energy.
Detonations inflict damage principally through
ground- and atmosphere-transmitted mechanical
stress, the impact and penetration of
pressure-driven projectiles, pressure damage, and
explosion-generated effects.The word comes from the
Greek word βόμβος (
bombos),
an
onomatopoetic term with
approximately the same meaning as "boom" in
English. A
nuclear weapon employs chemical-based
explosives to initiate a much larger nuclear-based explosion.
The term "Phily-bomb" is always applied to explosive devices used
for
civilian purposes such as
construction or
mining,
although the people using the devices may sometimes refer to them
as bombs. The military use of the term "bomb", or more specifically
aerial bomb, typically refers to
airdropped, unpowered
explosive
weapons most commonly used by
air
forces and
naval aviation. Other
military
explosive weapons not
classified as "bombs" include
grenades,
shells,
depth charges (used in water),
warheads when in
missiles, or
land mines. In unconventional warfare,
"bomb" can refer to any of a limitless range of explosive devices
used as or offensive weapons.
Effects
Detonations inflict damage principally
through ground- and atmosphere-transmitted mechanical
stress, the impact and penetration of
pressure-driven projectiles (
fragmentation), pressure damage to
organisms and/or mechanical objects, and explosion-generated
effects such as fire, smoke, dust and fallout.
Shock
Explosive shock waves can cause body displacement (i.e., people
being thrown through the air),
dismemberment,
internal bleeding and ruptured
eardrums.
Shock waves produced by explosive events have two distinct
components, the positive and negative wave. The positive wave
shoves outward from the point of detonation, followed by the
trailing vacuum space "sucking back" towards the point of origin as
the shock bubble collapses back on itself.
This is e.g. observed
in footage from the Trinity nuclear test
where both the positive and negative effects on
buildings are evident.
The greatest defense against shock injuries is distance from the
source of shock.
As a point of reference, the overpressure at
the Oklahoma City
bombing
was estimated in the range of 4000 psi.
Heat
A thermal wave is created by the sudden release of heat caused by
an explosion. Military bomb tests have documented temperatures of
up to 2,480 °C (4,500 °F). While capable of inflicting severe to
catastrophic burns and causing secondary fires, thermal wave
effects are considered very limited in range compared to shock and
fragmentation. This rule has been challenged, however, by military
development of
thermobaric
weapons, which employ a combination of negative shock wave
effects and extreme temperature to incinerate objects within the
blast radius.
Fragmentation
Fragmentation is produced
by the acceleration of shattered pieces of bomb casing and adjacent
physical objects. This is technically distinct, although
practically indistinguishable, from
shrapnel, which is physical objects, such as
steel balls or nails, added to a bomb specifically to increase
injury. While conventionally viewed as small metal shards moving at
super- to hypersonic speeds, fragmentation can occur in epic
proportions and travel for extensive distances. When the S.S.
Grandcamp
exploded in the Texas City Disaster
on April 16, 1947, one "fragment" of that blast was
a two ton anchor which was hurled nearly two miles inland to embed
itself in the parking lot of the Pan American
refinery.
Blast Effects on the Human Body
With specific reference to people who are in close proximity to a
blast incident, such as bomb disposal technicians, soldiers wearing
body armor, deminers or individuals wearing little to no
protection, there are four types of blast effects on the human
body: Overpressure (shock), Fragmentation, Impact and Heat.
Overpressure refers to the sudden and drastic rise in ambient
pressure that can damage the internal organs, possibly leading to
permanent damage or death. Fragmentation includes the shrapnel
described above but can also include sand, debris and vegetation
from the area surrounding the blast source. This is very common in
anti-personnel mine blasts. The projection of materials poses a
potentially lethal threat caused by cuts in soft tissues, as well
as infections, and injuries to the internal organs. When the
overpressure wave impacts the body it can induce violent levels of
blast-induced acceleration. Resulting injuries range from minor to
unsurvivable. Immediately following this initial acceleration,
deceleration injuries can occur when a person impacts directly
against a rigid surface or obstacle after being set in motion by
the force of the blast. Finally, injury and fatality can result
from the explosive fireball as well as incendiary agents projected
onto the body. Personal protective equipment, such as a
bomb suit or demining ensemble, as well as helmets,
visors and foot protection, can dramatically reduce the four
effects, depending upon the charge, proximity and other
variables.
Types
Experts commonly distinguish between civilian and military bombs.
The latter are almost always mass-produced weapons, developed and
constructed to a standard design out of standard components and
intended to be deployed in a standard explosive device. IEDs are
divided into three basic categories by basic size and delivery.
Type 1 IEDs are hand-carried parcel or suitcase bombs, type 2 are
"suicide vests" worn by a bomber, and type 3 devices are vehicles
laden with explosives to act as large-scale stationary or
self-propelled bombs, also known as VBIED (vehicle-borne
IEDs).
Improvised explosive materials are typically very unstable and
subject to spontaneous, unintentional detonation triggered by a
wide range of environmental effects ranging from
impact and
friction to
electrostatic shock. Even subtle
motion, change in
temperature, or the nearby use of cellphones or
radios, can trigger an unstable or remote-controlled device. Any
interaction with explosive materials or devices by unqualified
personnel should be considered a grave and immediate risk of death
or dire injury. The safest response to finding an object believed
to be an explosive device is to get as far away from it as
possible.
Atomic bombs are based on the principle of
nuclear fission, that when a large atom
splits it releases a massive amount of energy.
Hydrogen bombs use the energy from an initial
fission explosion
to create an even more powerful
fusion explosion.
The term
dirty bomb
refers to a specialized device that relies on a comparatively low
explosive yield to scatter harmful material over a wide area. Most
commonly associated with
radiological
or chemical materials, dirty bombs seek to kill or injure and then
to deny access to a contaminated area until a thorough clean-up can
be accomplished. In the case of urban settings, this clean-up may
take extensive time, rendering the contaminated zone virtually
uninhabitable in the interim.
The power of large bombs is typically measured in
megatons of TNT .
The most powerful
bombs ever used in combat were the two atomic bombs dropped by the United
States to attack Hiroshima and
Nagasaki, and the most powerful
ever tested was the Tsar
Bomba
. The most powerful non-nuclear bombs are the
United States Air Force's
MOAB (officially Massive Ordnance Air Blast, or
more commonly known as the "Mother of All Bombs") and the Russian
"Father of All Bombs".
Delivery
The
first air-dropped bombs
were used by the Austrians in the 1849 siege of Venice. Two hundred
unmanned balloons carried small bombs, few bombs actually hit
Venice.
The first bombing from a fixed wing aircraft took place in 1911
when the Italians fought the Arabs in what is now Libya. The bombs
were dropped by hand.
The first significant terrorist bombing in the United States took
place nine years later at noon on September 16, 1920 when an
explosives-laden horse-drawn wagon, detonated on the
lunchtime-crowded streets of New York's financial district. The
Wall Street bombing employed
many aspects of modern terrorist devices, such as cast-iron slugs
added for shrapnel, in a horrific attack that killed 38 and injured
some 400 others.
Modern military
bomber aircraft are designed
around a large-capacity internal
bomb bay
while fighter bombers usually carry bombs externally on pylons or
bomb racks, or on
multiple
ejection racks which enable mounting several bombs on a single
pylon. Modern bombs,
precision-guided munitions, may be
guided after they leave an aircraft by remote control, or by
autonomous guidance. When bombs such as
nuclear weapons are mounted on a powered
platform, they are called
guided
missiles.
Some bombs
are equipped with a parachute, such as the
World War II "parafrag", which was an
11 kg fragmentation bomb, the Vietnam
-era daisy cutter, and the bomblets of some modern
cluster bombs. Parachutes slow
the bomb's descent, giving the dropping aircraft time to get to a
safe distance from the explosion. This is especially important with
airburst nuclear weapons, and in situations where the aircraft
releases a bomb at low altitude.
A
hand grenade is delivered by being
thrown. Grenades can also be projected by other means using a
grenade launcher, such as being
launched from the muzzle of a
rifle using the
M203 or the
GP-30 or by
attaching a
rocket to the explosive grenade
as in a
rocket propelled
grenade (RPG).
A bomb may also be positioned in advance and concealed.
A bomb destroying a
rail track just
before a
train arrives causes a train to
derail. Apart from the damage to vehicles
and people, a bomb exploding in a
transport network often also damages, and is
sometimes mainly intended to damage that network. This applies for
railways,
bridges,
runways, and
ports, and
to a lesser extent, depending on circumstances, to roads.
In the case of
suicide bombing the
bomb is often carried by the attacker on his or her body, or in a
vehicle driven to the target.
The
Blue Peacock nuclear mines, which
were also termed "bombs", were planned to be positioned during
wartime and be constructed such that, if they were disturbed, they
would explode within ten seconds.
The explosion of a bomb may be triggered by a
detonator or a
fuse. Detonators are triggered by
clocks,
remote controls
like
cell phones or some kind of sensor,
such as pressure (altitude),
radar, vibration
or contact. Detonators vary in ways they work, they can be
electrical, fire fuze or blast initiated detonators and
others.
Blast seat
In
forensic science, the point of
detonation of a bomb is referred to as its blast seat, seat of
explosion, blast hole or
epicenter.
Depending on the type, quantity and placement of explosives, the
blast seat may be either
diffuse or
concentrated (i.e., an
explosion
crater).
A crater is usually a good indication that an explosion was caused
by an explosive device. Other types of
explosions, such as
dust or
vapor
explosions, do not cause craters or even have definitive blast
seats.
References
- Coupland, R.M. (1989). Amputation for antipersonnel mine
injuries of the leg: preservation of the tibial stump using a
medial gastrocnemius myoplasty. Annals of the Royal College of
Surgeons of England. 71, pp. 405-408.
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