Country of origin |
United States |
Entered service |
1982 |
Missile |
Missile length |
6.32 m |
Missile diameter |
0.62 m |
Wing span |
3.66 m |
Missile weight |
1 450 kg |
Warhead weight |
130 kg |
Warhead type |
Nuclear (5 - 150 kT) |
Range of fire |
2 400+ km |
Speed |
800 km/h |
CEP |
300 m |
Guidance |
Terrain-following radar and INS |
Launch platforms |
B-52G/H |
|
The Boeing AGM-86B ALCM
(Air-Launched Cruise Missile) is the primary nuclear munition of the
US Air Force (USAF). By the early 2016 it was the only air-launched
missile in the US inventory with a nuclear warhead. As a result, it
plays a pivotal role in the US government's strategic deterrence
policies.
Though this weapon itself is well-known, its origins ---
which by all accounts were quite strange --- are today quite
obscure. It was not originally supposed to be a cruise missile at
all; when it was, it was also supposed to perform two different
missions simultaneously; by the time the ALCM began to take shape as
a single-mission weapon, it suddenly became the program most
fiercely-opposed by the armed service that it was meant for; it was
canceled as a result, but it was revived in later years, and (much
to the chagrin of the USAF at the time) it eventually entered
service; and since then, the USAF has extolled it, as though they
never had an issue with it.
Since 1960
the USAF used an AGM-28 Hound Dog supersonic air-launched cruise
missile. It was carried by
B-52 series long-range strategic bombers.This missile had a
range of 1 250 km and was capable of carrying a nuclear warhead. It
was the first US air-launched stand-off nuclear weapon. Though
fielding of the Hound Dog was considered as a temporary solution
until a more suitable missile is available. Still though the AGM-28
Hound Dog was completely retired only in 1977.
Development of the new missile began in January of 1968. It
was known as the SCAD ("Subsonic
Cruise Aircraft Decoy"), an airborne decoy meant to mimic the radar
signature of a bomber carrying nuclear ordnance, which was to
replace the troublesome ADM-20 Quail in that role. SCAD was formally
approved in June of 1970, and work began on a prototype, the
ZAGM-86A. At some point in the early 1970s however, it occurred to
the USAF that the SCAD could itself be used to deliver a nuclear
warhead, and could do so relatively accurately after flying a great
distance from the launch point. The program was at this point split
into two parallel projects; SCUD ("Subsonic Cruise Unarmed Decoy"),
and SCAD, which was now backronymed to mean "Subsonic Cruise Armed
Decoy". The idea was that in the event of a nuclear offensive (most
likely against the USSR), US bombers employing the SCAD and SCUD now
had an additional layer of ambiguity to operate under inside enemy
airspace, as any radar contact could be a SCAD, a SCUD, or a bomber
armed with nuclear warheads (possibly being additional SCADs).
However,
when the USAF began pressing hard for the introduction of a new
bomber during the early 1970s, their attitude toward SCAD and SCUD
took an abrupt turn. The B-1A Excalibur strategic bomber was to use
raw speed and free-fall ordnance to attack enemy territory, and
because it was one of the most expensive items in the USAF budget,
air-launched cruise missiles were seen as unwanted competition.
Critics of the B-1 had already begun agitating for the use of cruise
missiles instead of B-1s, as older B-52s could be made to launch
them. This was not well-received by the USAF's leadership (nor
Rockwell, the B-1A's manufacturer, who were faced with possible
bankruptcy if they didn't sell the B-1). There was even discussion
outside the USAF of replacing bombers with cruise missiles entirely,
no doubt reminding some of such prior debacles as the Snark
intercontinental cruise missile (whose guidance system was so bad
that at least one example, aimed at the Faroe Islands in the North
Atlantic, instead landed in Brazil), and attempts by the Eisenhower
and Kennedy administrations to totally replace bombers with ICBMs.
Citing cost and schedule overruns, and a seemingly
uncountable increase in complexity for the ZAGM-86 and the program
developing it (which somehow hadn't been an issue when these
problems emerged years prior), the USAF canceled the program in June
of 1973. Behind the scenes, what the USAF's leaders actually feared
was that introducing the ZAGM-86 into service would eliminate the
case for the B-1A. The cancellation was short-lived, however,
because the USAF realized that because the Navy was developing its
own cruise missile (the SLCM, or Sea-Launched Cruise Missile, a
program that resulted in the
BGM-109 Tomahawk), they might lose the entire mission to the
Navy --- high-speed bomber or not. In response (at least in part) to
the SLCM program, SCAD was renamed ALCM (Air Launched Cruise
Missile), and the SCUD portion of the program was eventually
discontinued.
Thus, in September of 1974, Boeing was awarded a contract to
complete development of the ZAGM-86. Only now, there was a catch; as
a thinly-veiled safeguard against cancellation of the B-1A, the
ZAGM-86 had to be shortened, for the purpose of fitting into the
bomb bay of that aircraft. The USAF "sanitized" the back-story on
requirement, stating that they wanted the ZAGM-86 to fit onto the
existing pylons for the
AGM-69 SRAM tactical nuclear missile already
in service (what they didn't let-on was that the only aircraft in
the USAF inventory then outfitted to carry the SRAM were the
FB-111 and B-52, but they carried this weapon externally).
Congress in 1977 had also taken an interest in a single
cruise missile model for use by both the US Navy and USAF (the JCMP,
or "Joint Cruise Missile Project"). Neither the US Navy nor USAF
cared much for the prospects of operating one another's missiles,
and the ZAGM-109 had proven more unwieldy for a bomber to carry than
the ZAGM-86, while the former was less suitable for launch from
submarines than the latter. The outcome of the JCMP program was
nonetheless productive, as both services agreed to use common
components in their respective cruise missiles, including the engine
and guidance system.
Another watershed event occurred in the same timeframe as
JCMP was the termination of the B-1 program by President Jimmy
Carter. This triggered a crisis in the USAF, because instead of a
debate over whether the USAF should operate B-52s with cruise
missiles or the B-1, now they no longer had a choice. Many officials
hoped the next presidential administration would revive the B-1
program (which did in fact occur), but the B-1 wouldn't enter
service until well into the future if it could even be revived at
all; left with no other choice, the USAF fully-embraced the ALCM.
As there was no longer a need to squeeze the ALCM into the
bomb bay of a B-1, the USAF had Boeing discontinue the AGM-86A in
favor of the original, larger version. Initially designated the ERV
ALCM, the larger missile was still compact enough for several to be
carried inside the B-52's internal bay, and was the model that
competed with the ZAGM-109 during the JCMP competition. Development
continued for several more years, and the larger ERV ALCM entered
service with the USAF in August of 1981 as the AGM-86B ALCM.
Interestingly, although the B-1 bomber finally entered
service with the USAF later in the same decade, and it too was
expanded into a "B" model, the original internal bay dimensions were
retained, making the
B-1B Lancer too cramped to carry the AGM-86B. The USAF also
declined to make the
B-2
Spirit bomber compatible with this missile, deciding that the
AGM-86B was too easily detected for use in the B-2's mission; this
led to the development of what would become the
AGM-129 ACM. As a
result, the only aircraft presently configured to employ the ALCM is
the B-52.
The AGM-86B has a long fuselage with a trapezoidal
cross-section, a tapered, slightly rounded nosecone, and rounded
corners. The sides of the ALCM are flat and sloped inward, while the
topside is rounded, and the belly is shallowly peaked. The fin-like
cantilever wings are short and extremely narrow, and are recessed
into the belly of the missile until it is launched. Two small,
trapezoidal horizontal stabilizers are mounted on the tail of the
missile, which are folded-up against the fuselage until launch. When
unfolded, they lock into an anhedral position. The tailfin is also
small and trapezoidal, and is wrapped around the left side of the
fuselage prior to launch. A tubular airscoop, which blends neatly
into the aft fuselage in its aft section, is mounted in front of the
tailfin. The thrust nozzle for the ALCM is very small, and mounted
at the base of the tail. Finally, it is worth noting that the
AGM-86C/D CALCM have an almost identical appearance, making
these conventionally-armed missiles difficult to distinguish from
the nuclear AGB-86B ALCM.
The B-52G (now retired) and
B-52H can carry the ALCM on its external hardpoints, or inside
its bomb bay. When mounted externally, a total of 12 ALCMs are
mounted on each pylon, in two tandem triple clusters. The ALCM is
carried in the bomb bat on a rotating launch rack, which hold up to
8 missiles; though the B-52 could probably carry more missiles if
they were stacked-up in the internal bay (in the same fashion as it
carries bombs), the rotating rack eliminates the dilemma of having
one or more missiles trapped above another that fails to release (a
malfunction known as a "hung munition", which is not an uncommon
problem). The trapezoidal cross-section of the ALCM also contributes
heavily to its ability to be carried in such large numbers on both
the pylons and the rotating rack, as it allows more to be crammed
into a given volume than a purely cylindrical missile --- this can
clearly be seen in photographs of rotating racks fully-laden with
ALCMs.
The guidance system used in the AGM-86B consists of a
McDonnell-Douglas AN/DPW-23 Terrain Following Radar (TFR), with a
Terrain Contour Matching (TERCOM ) capability. TERCOM allows the
missile to fly on a preprogrammed route, via image recognition of a
series of radar photographs of the terrain. The addition of
Instrument Navigation System (INS) guidance helps steer the missile
onto this course upon launch, and maintain the proper heading, both
via compass. This makes the missile fully autonomous upon release
and impossible for enemy action to divert, allowing the bomber that
launched it to immediately begin another missile run, or beat a
hasty retreat.
However,
TERCOM is also quite delicate, and is easily defeated by jamming or
interference, and terrain covered by snow, ice, or inundated with
water has been found to yield false radar returns. Experience with
the
BGM-109 Tomahawk (which uses the same guidance method) also
demonstrates that missiles with TERCOM guidance can easily drift off
course, especially if much of the terrain they have to fly over is
largely featureless (such as in the Arabian Desert); sometimes, when
the TFR finally began to receive returns from unfamiliar landmarks,
effectively causing the missile to fly aimlessly until it had flown
the required distance, and then plunged into the ground. Notably,
errant Tomahawks launched in the 2003 Invasion of Iraq landed in
locations as far off target as Turkey, Iran, and Syria. It goes
without saying, but such imprecision has frightening implications
for a nuclear-tipped cruise missile with a range of over 2 000 km.
The AGM-86B is powered by a Williams F107-WR-100 turbofan
engine, generating 2.7 kN of thrust; some examples are powered by
the largely similar F107-WR-101 engine, with the same power output.
The missile briefly produces a line of thin, black smoke after
launch, suggesting that it uses a black powder-based starter
cartridge (though other factors could cause the smoke trail to be
darker during the first seconds of propulsion). As the missile is
already moving through the air at considerable speed when released
from an aircraft, a rocket booster is not employed in the AGM-86B,
unlike the US Navy's counterpart, the BGM-109 Tomahawk (which
otherwise employs the same F107 engine).
The AGM-86B only delivers one type of munition, the W80
thermonuclear warhead. This is a variable yield warhead, with which
the aircrew can selectively "dial-in" the force of the blast. The
lowest setting is 5 kT, while the highest is 150 kT. The W80 was
produced in two variants, the W80-1 and subsequent W80-0; the
differences between the attributes of these models is unclear.
Approximately 1 715 AGM-86Bs have been manufactured, from
1980 to 1986. Of these, 528 remain in the US inventory, with another
500 being retired from 2007 onward. Several-hundred of the others
were converted into
CALCMs in earlier years. The unit cost of an AGM-86B is
approximately US$1 million, though assembly lines used to
manufacture the AGM-86B no longer have the ability to do so. Due to
the geopolitically sensitive nature of nuclear arms, the AGM-86B is
not available for export.
The AGM-86B has made several notable appearances in media,
notably in the movie Never Say Never Again, where it was incorrectly
depicted as being launched from a B-1A (only the AGM-86A was
compatible with the B-1 series; moreover, in the scenes showing the
missiles being prepared under the aircraft prior to flight, the
aircraft's belly is clearly that of a Concorde airliner); the film
also incorrectly depicts the AGM-86B as being powered by an
afterburning engine (there are no afterburning F107s).
The future of the AGM-86B ALCM remains uncertain, as a
suitable successor has yet to materialize, despite the USAF's Long
Range Stand-Off requirement for such a weapon. Its role is possibly
more important than ever before, due to the retirement of the
subsequent
AGM-129 ACM in 2012, and the slowly dwindling number of
operational
B-52Hs to launch them. The remaining missiles have been given a
SLEP (Service Life Extension Program) to extend their service into
as far into the future as 2030, but the 1970s-era technology of the
ALCM has arguably been obsolete in the nuclear attack role for
decades.
It is also possible that the remaining AGM-86Bs will be
converted into conventionally-armed CALCM missiles (which had been
done before); though given that no such conversion has been made for
years, this outcome is increasingly becoming improbable.
Variants
SCAD:
"Subsonic Cruise Armed Decoy"; the original concept for the ALCM.
Evolved into the AGM-86A.
SCUD: "Subsonic Cruise Unarmed Decoy"; airborne decoy version
of the SCAD. Did not enter service.
AGM-86A ALCM: Original design with a reduced length for the
B-1A's bomb bay. Did not enter service.
AGM-86B ALCM: Enlarged version of the AGM-86A, with a
radically enlarged and re-shaped fuselage.
AGM-86C/D CALCM: Conventionally-armed version of the ALCM.
Described on a separate page.
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