Gravity bomb " and the "
Fat Man" devices were large and cumbersome
gravity bombs. Historically the first method of nuclear weapons delivery, and the method used in
the twin instances of
nuclear warfare in history, was a
gravity bomb dropped by a
plane. In the years leading up to the development and deployment of nuclear-armed missiles, nuclear bombs represented the most practical means of nuclear weapons delivery; even today, and especially with the
decommissioning of nuclear missiles, aerial bombing remains the primary means of offensive nuclear weapons delivery, and the majority of US nuclear warheads are represented in bombs, although some are in the form of missiles. Gravity bombs are designed to be dropped from planes, which requires that the weapon be able to withstand vibrations and changes in air temperature and pressure during the course of a flight. Early weapons often had a removable core for safety, known as
in flight insertion (IFI) cores, being inserted or assembled by the air crew during flight. They had to meet safety conditions, to prevent accidental detonation or dropping. A variety of types also had to have a fuse to initiate detonation. US nuclear weapons that met these criteria are designated by the letter "B" followed, without a hyphen, by the sequential number of the "
physics package" it contains. The "
B61", for example, was the primary bomb in the US arsenal for decades. Various air-dropping techniques exist, including
toss bombing,
parachute-retarded delivery, and
laydown modes, intended to give the dropping aircraft time to escape the ensuing blast. The earliest gravity nuclear bombs (
Little Boy and
Fat Man) of the United States could only be carried, during the era of their creation, by the special
Silverplate limited production (65 airframes by 1947) version of the
B-29 Superfortress. The next generation of weapons were still so big and heavy that they could only be carried by bombers such as the six/ten-engined, seventy-meter wingspan
B-36 Peacemaker, the eight jet-engined
B-52 Stratofortress, and jet-powered British RAF
V bombers, but by the mid-1950s smaller weapons had been developed that could be carried and deployed by
fighter-bombers. Modern nuclear gravity bombs are so small that they can be carried by (relatively) small
multirole fighteraircraft, such as the single-engined
F-16 and
F-35.
Cruise missile s have a shorter range than
ICBMs.
U/RGM-109E Tomahawk pictured (
not nuclear capable anymore). A
cruise missile is a
jet- or
rocket-propelled missile that
flies aerodynamically at low altitude using an automated guidance system (usually
inertial navigation, sometimes supplemented by either
GPS or
mid-course updates from friendly forces) to make them harder to detect or intercept. Cruise missiles can carry a nuclear warhead. They have a shorter range and smaller
payloads than ballistic missiles, so their warheads are smaller and less powerful. The
AGM-86 ALCM is the
US Air Force's current nuclear-armed
air-launched cruise missile. The ALCM is only carried on the
B-52 Stratofortress which can carry 20 missiles. Thus the cruise missiles themselves can be compared with MIRV warheads. The
BGM/UGM-109 Tomahawk submarine-launched cruise missile is capable of carrying nuclear warheads, but all nuclear warheads were removed following the
Intermediate-Range Nuclear Forces Treaty. Cruise missiles may also be launched from
mobile launchers on the ground, and from naval ships. There is no letter change in the US arsenal to distinguish the warheads of cruise missiles from those for ballistic missiles. Cruise missiles, even with their lower payload, speed, and thus readiness, have a number of advantages over ballistic missiles for the purposes of delivering nuclear strikes: • Launch of a cruise missile is difficult to detect early from satellites and other long-range means, contributing to a
surprise factor of attack. • That, coupled with the ability to actively maneuver in flight, allows for penetration of
strategic anti-missile systems aimed at intercepting ballistic missiles, which typically fly on a ballistic arc without complex maneuvers. However, cruise missiles are vulnerable to typical
air-defence means as they are essentially
one-use unmanned aircraft; strategies such as
combat flights of fighter aircraft, or an integrated air-defence system comprising both CAP and ground-based elements, such as
surface-air missiles (SAM), can be used to defend against a cruise missile attack. Prior to the development of nuclear-armed
submarine-launched ballistic missiles, the United States and the Soviet Union conducted their first
at-sea deterrence patrols using modified
submarines armed with very large nuclear-armed cruise missiles; The US operated various
diesel-electric submarines armed with the
Regulus missile, and the Soviets operated
Modified Whiskey-class armed with the
P-5 Пятёрка. These early nuclear-armed SSGs served for a few decades until there were enough SSBNs put in service, after which they were retired. Their spiritual successors, armed with larger amounts of more modern, smaller cruise missiles continue to serve to this day serving in a tactical strike role, although they could be rearmed with nuclear cruise-missiles if need be.
Air- or
ground-launched nuclear-armed cruise missiles (sometimes even
nuclear-powered) were
considered by both sides early in the Cold War, but both concluded that it was impractical with the technology of the time. Nuclear-powered aircraft were considered due to the nascent
aeronautical and
rocketry technology of the time, especially when considering the temperamental and inefficient nature of
early jet engines, which limited the range and use cases of strategic bombers and cruise missiles. Later on in the Cold War both
disciplines had advanced far enough that it was feasible to create both reliable long-ranged cruise missiles and the strategic bombers able to launch them. Another
arms-race began which produced contemporary post-Cold War cruise missiles and launch systems;
VLS technology also allowed for surface ships to be armed with nuclear-armed cruise missiles while concealing their true payload. In 2018, the first operational nuclear-powered strategic cruise missile, the
SSC-X-9 "Skyfall" (9М730 Буревестник) was revealed by Russian president
Vladimir Putin. It is under development and is slated to enter service sometime in the 2020s.
Ballistic missile SLBM launched by
Royal Navy Missiles using a
ballistic trajectory deliver a
warhead over the horizon; in the case of the most capable of these, classified as
intercontinental ballistic missiles (ICBMs) (and
submarine-launched ballistic missiles (SLBMs) if transported by
submarine), they can reach distances of nearly tens of thousands of kilometers. Most ballistic missiles exit the Earth's atmosphere and re-enter it in their
sub-orbital spaceflight. Ballistic missiles aren't always nuclear armed, but the conspicuous and alarming nature of their launch often precludes arming ICBMs and SLBMs, the most capable classes of ballistic missiles,
with conventional warheads. Placement of nuclear missiles on the
low Earth orbit has been banned by the
Outer Space Treaty as early as 1967. Also, the eventual Soviet
Fractional Orbital Bombardment System (FOBS) that served a similar purpose—it was just deliberately designed to deorbit before completing a full circle—was phased out in January 1983 in compliance with the
SALT II treaty. An ICBM is more than 20 times as fast as a
bomber and more than 10 times as fast as a
fighter plane, and also flying at a much higher altitude, and therefore more difficult to defend against. ICBMs can also be
fired quickly in the event of a surprise attack. Early ballistic missiles carried a single
warhead, often of
megaton-range yield. Because of the limited accuracy of the missiles, this kind of high yield was considered necessary to ensure a particular target's destruction. Since the 1970s modern ballistic weapons have seen the development of far more accurate targeting technologies, particularly due to improvements in
inertial guidance systems. This set the stage for smaller warheads in the hundreds-of-
kilotons-range yield, and consequently for ICBMs having
multiple independently targetable reentry vehicles (MIRV). Advances in technology have enabled a single missile to launch a payload containing several warheads; the number of which depended on the missile's and payload bus' design. MIRVs has a number of advantages over a missile with a single warhead. With few additional costs, it allows a single missile to strike multiple targets, or to inflict maximum damage on a single target by attacking it with multiple warheads. It makes
anti-ballistic missile defense even more difficult, and even less economically viable, than before. Missile warheads in the American arsenal are indicated by the letter "W"; for example, the W61 missile warhead would have the same
physics package as the B61 gravity bomb described above, but it would have different environmental requirements, and different safety requirements since it would not be crew-tended after launch and remain atop a missile for a great length of time. While the
first modern ballistic missile designed is the basis of contemporary rocket- and missilery, it never carried a nuclear warhead. The first ICBM ever designed was the Soviet
R-7. The first
SLBM-carrying submarine was also Soviet; the
prototype Modified
Zulu-class and the mass-produced
Golf-class ballistic missile submarines carried their SLBMs in their sails, but these pioneering designs had to surface to launch their ballistic missiles. The Americans responded with the first "modern design" of ballistic missile subs; the
George Washington-class, which launched the
Polaris SLBM. The subsequent arms-race culminated in some of the largest submarines ever designed; the
Trident-armed 170-meter long
Ohio-class submarine armed with 24 × 8 MIRV
Trident missiles, and the
battlecruiser-sized 48,000
tonne Project 941 Акула, the Typhoon-class submarine, armed with 20
R-39s with 10 MIRVs each. After the Cold War, SSBN and subsequently SLBM development have slowed, but nascent nuclear powers are building
novel classes of
SSB(N)s, while the established powers, all members of the
United Nations Security Council, are plotting the
next-
generation of nuclear-powered nuclear-armed ballistic missile submarines.
Hypersonically-Gliding Warheads are a novel form of warhead to arm ballistic missiles. These maneuverable devices threaten to obsolate current forms of
ABM defences, thus various nascent and established nuclear powers are
racing to
field examples of such
systems.
Other delivery systems artillery shell is the smallest known nuclear weapon developed by the US. was an early US thermonuclear weapon and weighed around 21
short tons (19,000 kg). Other delivery methods included
nuclear artillery shells,
mines such as the
Medium Atomic Demolition Munition and the novel
Blue Peacock,
nuclear depth bombs, and
nuclear torpedoes. An
'Atomic Bazooka' was also fielded, designed to be used against large formations of tanks. In the 1950s the US developed small nuclear warheads for air defense use, such as the
Nike Hercules. From the 1950s to the 1980s, the United States and Canada fielded a
low-yield nuclear armed
air-to-air rocket, the
AIR-2 Genie. Further developments of this concept, some with much larger warheads, led to the early
anti-ballistic missiles. The United States have largely taken nuclear air-defense weapons out of service with the fall of the
Soviet Union in the early 1990s. Russia updated its nuclear armed Soviet era anti-ballistic missile (ABM) system, known as the
A-135 anti-ballistic missile system in 1995. It is believed that the, in development successor to the nuclear A-135, the
A-235 Samolet-M, will dispense with nuclear interception warheads and instead rely on a conventional
hit-to-kill capability to destroy its target. Small, two-man portable tactical weapons (erroneously referred to as
suitcase bombs), such as the
Special Atomic Demolition Munition, have been developed, although the difficulty to combine sufficient yield with portability limits their military utility. ==Costs==