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Vampire
Under construction.
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Violet Club
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Violet Club was the first high yield weapon deployed by the British, and was intended to provide an emergency capability until a
thermonuclear weapon could be developed from the Christmas Island thermonuclear tests known as Operation Grapple. After the Americans
tested a thermonuclear weapon in 1952, followed by the Soviets with Joe 4, and before the UK government took a decision in July 1954 to
develop a thermonuclear weapon, AWRE Aldermaston were asked in 1953 about the possibilities for a very large pure fission bomb
yielding one megaton. AWRE's response referred to the Zodiak Mk.3 bomb, but progressed no further than a rudimentary
study. (1)
At this time studies were also started (2)
that ultimately led to a decision in 1954 to develop a thermonuclear weapon, and the design studies were split into two tracks, the
Thermonuclear Bomb Type A, a hybrid type, really a very large boosted fission device, no longer regarded as a thermonuclear weapon, and
the Type B, a device that derives a significant amount of energy from fusion. (3)
The British at that time had not yet discovered the Teller-Ulam technique necessary to initiate fusion, and the Type B was still beyond their
capabilities. The intermediate devices proposed, the Type A hybrids, were similar in concept to the Alarm Clock and Joe-4 layer cake hybrid
designs of other nuclear powers. Although these Type A intermediate devices used small quantities of fusion fuel in their fissile cores to
provide a supply of energetic, fast neutrons to boost the efficiency of the fission reaction, they did not derive a measurable amount of energy
output from fusion.
The Violet Club warhead, known variously as Green Grass, Knobkerry, and the Interim Megaton Weapon was a pure, unboosted fission
device derived from the two British Type A weapons, stripped of their fusion boosting elements. It was the largest pure fission weapon
deployed by any nuclear power.
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Genesis
The British Type A hybrid weapon was known as Green Bamboo, weighed approx 4,500 lb (2,045 kg) (4) and its spherical shape measured
approx 45 inches diameter, with a 72-point implosion system. Green Bamboo was intended as the warhead for all projected British strategic
delivery systems of the period; Yellow Sun Stage 1, a free-fall bomb for the V-bombers; Blue Steel an air-launched stand-off missile, also
deployed aboard the V-bombers; and Blue Streak, a silo-based medium-range ballistic missile. Various other proposed delivery systems would
also use this standardised warhead. The large girth of both Yellow Sun and Blue Steel was necessary to accomodate the large spherical
implosion system of Green Bamboo. (5)
A variant with a smaller implosion sphere, fewer explosive lenses, and some other changes was substituted for Green Bamboo when it
was realised that the Blue Streak ballistic missile would be unable to accommodate the weight of Green Bamboo without appreciable loss of
range performance. This Type A hybrid variant was codenamed Orange Herald, (6) and its reduced size and weight was achieved by reducing the size of the surrounding explosive
layers (7) to under 1'000 lbs (454 kg) (8)
and this would result in less compression at the fissile core when detonated, and a reduced nuclear efficiency and yield. Less fissile material is
consumed as a consequence of lower compression before fission ends as the core expands and blows itself apart. To counter this and maintain
yield at the desired level of 1 MT the fissile core of Orange Herald was enlarged, and this in turn made excessive demands on scarce and
expensive fissile material. Estimates computed from reliable declassified official sources of actual core cost (9)
and cost per kilogram of HEU (10) put the
core sizes of Green Bamboo and Orange Herald as 98 kg and 125 kg respectively, although some other published (and unverified) sources
claim lower figures of 87 kg and 117 kg respectively. A useful benchmark is the declassified document written by Sir William Penney in 1953,
that estimated 120 kg of HEU was required for the 1 MT Zodiak Mk.3 unboosted fission warhead. (11)
This Orange Herald hybrid boosted fission design was tested at Christmas Island in 1957, yielding 720 kt, (12)
although AWRE scientists considered that the boosting elements failed to work, and that it functioned as a pure fission device. (13)
Estimates of the quantity of HEU used in this device and in the Green Grass pure fission warhead of Violet Club should be interpreted in this
light, although there is no declassified hard evidence on this point and all published figures are speculative.
These two weapons, Green Bamboo and Orange Herald were intended as the two hybrid weapon predecessors of the first British
thermonuclear weapons, based on the Granite design series that began with Short Granite, Purple Granite, Grapple X, Grapple Y, Flagpole
and Halliard at Grapple Z.
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Emergency Capability Weapon
Delays and failures in the Granite programme and the abandonment of Green Bamboo without a test, left a gap in the programme, and
an emergency capability weapon to fill that gap was devised from elements of both Green Bamboo and Orange Herald; being known as
Knobkerry, (14) or Green Grass, and
the Interim Megaton Weapon. (15)
There were also other factors involved in the decision to build an Interim Megaton Weapon. One being that the British production programme
was by 1957 producing quantities of HEU for which there was no immediate need; and the Chiefs of Staff were reluctant to see it continue to
languish in stores, unused for weapons, when it was being produced at great cost. (16)
The Air Staff wanted the Interim Megaton Weapon to hoover-up the HEU allocated to them for strategic weapons but not yet used because of
delays in development of thermonuclear weapons. The Air Staff view was that if the stored HEU were not used, they may lose it to the other
Services. (17) The Army wanted
nuclear landmines, and the Navy required HEU for a nuclear submarine reactor development programme, and 60 kg to fuel HMS Dreadnought,
the Navy's first nuclear-powered submarine.
Although there are no reliable or declassified sources for this amount, and one declassified source states the core size as "up to 120
kg" (18) the Green Grass warhead
containing perhaps 60–86 kg of HEU was hurriedly produced and installed in a modified Blue Danube casing, to be known as Violet Club, until
a better weapon based on a later Yellow Sun casing and the Green Grass warhead could be produced. This later, fully developed weapon,
engineered to robust Service standards, was to incorporate better safety devices with in-flight removal of the nuclear safety device. The earlier
Violet Club weapon was expected to be short-lived. A lower standard of safety and robustness was accepted for Violet
Club, (19) and the nuclear safety
device was removed on the ground after loading into the aircraft. At take-off Violet Club was armed and live. Because it was thought too
dangerous to fly with it except in an operational emergency, and too dangerous to attempt a landing at base, no training, exercise or other
peacetime flights were ever permitted. Nor was it permitted to be transported by road to the remote V-bomber dispersal bases around the UK,
where the bombers would routinely disperse to at periods of heightened international tension. It had to be stored assembled at the assigned
bomber bases, since transport on public roads from nearby specialist weapon storage facilities was forbidden.
Plans for twelve Violet Club weapons were approved by the Chiefs of Staff for carriage in Vulcan and Victor aircraft, but in the event
production was curtailed early, with only five produced, (20) carried
by Vulcan aircraft only, and known by the RAF description of Bomb, Aircraft, HE 9'000 lb HC, (21)
and their Green Grass warheads were removed for transfer to Yellow Sun casings when these became available. None were ever under RAF
operational control during their short lives. Because of their complexity, and the fact that they were rushed into service as an emergency
capability weapon, and that they were never proof-tested in a full nuclear test, nor been through the normal rigorous pre-Service testing process
conducted by agencies independent of the designers and manufacturers, they were never formally accepted into service, or approved for Service
use. Instead, the weapons were in the custody of AWRE staff at RAF bases, to be released to the RAF in the event of a national emergency
being declared by the relevant authority. (22) Although
Violet Club was known by the Service designation Bomb, Aircraft, HE 9'000 lb HC, this was a notional weight only. Actual weight was different.
To make use of the existing Blue Danube casing without costly and time-consuming further tests, conditions that determined the known ballistic
properties of the casing were replicated in Violet Club, with ballast carried to match Blue Danube's weight of 10'250 lbs and centre of gravity.
The added weight of the ballbearing safety device increased total weight to 11'250 lbs (5'114 kg) when loaded into an aircraft for a 30-day
readiness period, (23) although the
aircraft release mechanism was limited to 11'100 lbs for a ferry flight. (24)
Dispersal to remote airfields with the safety device in place was therefore not possible.
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Design defects
Violet Club and Green Grass were not considered satisfactory designs and suffered from numerous design defects, some, in the case
of Violet Club's casing, being inherited from the Blue Danube casing that had itself suffered from numerous defects. Many of these were
attributable to it being the first British nuclear bomb, and it being the first bomb to be designed for release from aircraft flying at the great
heights and speeds envisaged; and there was no experience of bomb release at more than twice the height and speed of the previous
generation of medium bombers.
The Blue Danube casing also suffered from being the first bomb casing designed with a large di-electric plastic nose. There was little
previous manufacturing experience of these very large plastic mouldings, with only two manufacturers in the UK able to work to the demanding
standards required, and these mouldings were the cause of much frustration with operation of the radar fuzes in Blue Danube. These fuzes,
based on radar altimeter technology, were omitted from Violet Club, and replaced with off-the-shelf clockwork timers backed-up with
barometric fuzes. Without the requirement for radar transparency, the plastic nose was replaced with a less troublesome metallic nose in
Violet Club.
The barometric fuzes themselves were an issue, because the aerodynamic design of the casing was very 'slippery' with a terminal velocity
greater than Mach 2 when released from great heights and speeds. At this time, no aircraft could reach those speeds, and few could exceed
Mach 1 except in a dive. Indeed, prior to the delivery of the first V-bomber in 1954, the RAF had no means of carrying the Blue Danube casing
to the heights, or at the speeds required for test flights. At the high terminal speeds reached by the casing, the barometric sensing devices were
prone to errors unless located where transonic shockwaves could not effect accuracy, but there was little understanding or experience to draw
upon. In essence, the barometric fuzes were used in Blue Danube as 'gates' to switch on the power supply to the radar (altimeter) fuzes. This
technique permitted the radar fuzes to be used sparingly, in the last few seconds before detonation at a measured height above ground, and
being switched on only briefly, it was hoped that the radar fuzes would then be immune to enemy jamming. The barometric fuzes alone could not
acheive the accuracy demanded without calibration to local air pressure. In Violet Club, this complex system was discarded, and a simple
clockwork timer was activated at bomb release, that could be set using the casing's known measured ballistic performance data. The
clockwork fuze was then backed-up with a barometric fuze and an impact fuze to ensure detonation in the event of a failed clockwork and
barometic fuze.
A major defect was the reliance on batteries for all electrical power after release from the aircraft. The batteries used were 6v lead acid
accumulators, - commercial motorcycle batteries, that were kept fully-charged and inserted into the weapon on the ground
immediately before flight. In Violet Club they were used to charge large capacitors in the warhead firing circuits and provide power to the Blue
Stone ENI (External Neutron Initiator). Both were essential components of the firing circuits. Storing the batteries outside the weapon while on
the ground was thought a necessary safety break between the power supply and the firing circuits, but contributed to lengthy delays while the
batteries were inserted at the last minute before flight. Later generations of weapons used ram-air-driven generators that provided no power
prior to release, or thermal batteries that could be safely stored in the weapon for lengthy periods without maintenance, and the necessary
safety break was provided by other means, eg speed detectors activated only by bomb release.
Other design flaws, the rushed Service entry and uncertainty about shelf-life of the weapon led to a requirement for a complete strip-down
and inspection at six-monthly intervals. Each taking three weeks per weapon using AWRE civilian staff. The unstable nature of the weapon, with
the fissile core being greater than one uncompressed critical mass, required that the work being done in-situ at RAF bases, causing
considerable disruption to operational duties. Three principal reasons for the strip-downs were deterioration of the rubber bag lining the inside
of the hollow spherical core, that was in intimate contact with the steel balls, corrosion of the steel ballbearings, which exacerbated rubber bag
deterioration, and deterioration of the HE, which was prone to cracking. Replacement of the HE would cost RAF budgets in excess of £92'000
adjusted to 2007 prices. (25) The RAF
were under considerable pressure to find adequate storage for the weapons at operational bases, because the weapon was too unstable to be
transported by road to suitable specialist weapon storage facilities, or to be stored in close proximity to other similar weapons. One weapon per
storage building was the rule. Strip-down inspections were a further hindrance to their operational duties, seriously jeopardising essential safety
and servicing work on tactical nuclear weapons. (26)
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Green Grass warhead
The Green Grass warhead of Violet Club was a hollow spherical implosion design; a fissile core of HEU (Highly Enriched Uranium,
weapons or military grade U-235) surrounded by an explosive supercharge and a 72-lens implosion system. The HEU core brought together
into one solid piece was greater than one uncompressed critical mass. To prevent spontaneous fission and keep it sub-critical the HEU was
fabricated into a hollow thin-walled sphere of approximately 22 in (560mm) internal diameter and approximately 0.126 in (3.21mm) thick,
although there is as yet, no declassified hard evidence to support these figures computed from other declassified data.. When triggered, the HE
implosion system collapsed the core inwards into a solid sphere of approx 7 in (180 mm) diameter at normal density, continuing to crush it yet
smaller. The hollow core also benefited from what is referred to as levitation, where the airspace within the hollow sphere permits the collapsing shell
to gather speed before impacting at the centre. This process has been described as 'hammering' the core as in driving a nail using the kinetic
energy of a swinging hammer, as distinct from placing the hammerhead on a nail and pushing. Although it is not clear that British designers
were aware of the benefits of a levitated design at this stage.
The Green Grass warhead contained perhaps 60–86 kg of HEU (although there are no declassified direct sources for this figure). The most
reliable figure so far obtained is 58.9 kg, computed from declassified figures of amounts of material recovered and recycled after Green Grass
was withdrawn from service. Declassified records show that in total there were thirtyseven Green Grass warheads manufactured. Five were
installed in Violet Club casings initially, before being transferred to newer Yellow Sun Mk.1 casings to join thirtytwo others installed in Yellow Sun
Mk.1 casings; thirtyseven Green Grass warheads in total. 2179 kg of U-235 was recovered (27) from
these thirtyseven warheads, and the arithmetic shows an unexpectedly low figure of 58.9 kg per warhead. Although more than an uncompressed
bare (unreflected) spherical critical mass of 52 kg, (28) this
is a quantity of U-235 considerably less than the 64 kg (29) that
was used in Little Boy used at Hiroshima. Nevertheless, the RAF were nervous of the weapon.
The hollow spherical core was entirely supported by a tamper (believed to be tuballoy, or natural uranium) and the HE supercharge and
lenses. These in turn were supported inside a cast magnesium 'honeycomb' or matrix to aid structural strength. (30) The honeycomb can be visualised as similar in
concept to an eggbox supporting an egg, with holes piercing it to permit wiring and other services to pass.
Knobkerry, or Green Grass was the first deployed British warhead to dispense with the crude crush-type polonium-210 and beryllium
neutron generators used to initiate fission with a burst of neutrons. These were used in all earlier weapon designs, including Little Boy, Fat
Man, Blue Danube and Red Beard, and were a great inconvenience with their short shelf-life of around six to nine months before requiring
replacement. The logistical difficulties were enormous. Instead, Green Grass used an Electronic Neutron Generator or ENI codenamed Blue
Stone, also referred to as Unit 386D, which had the virtue of being located outside the implosion sphere and was adjustable, allowing
the neutron burst to be triggered at precisely the right moment to maximise yield. Prior to release, the Blue Stone ENI drew electrical power from
the aircraft via an improvised device known by the codeword Fishfryer, which supplied power to warm-up the ENI and charge
capacitors. (31)
Burst heights of 3'500 ft and 6200 ft AGL (above ground level) (32)
were chosen to maximise ground overpressure at 6psi, or to maximise overpressure without fireball ground contact, using a barometric fuze
with a clockwork timer backup. (33)
Impact and graze fuzes provided an assured detonation. With the exception of the clockwork timer, these fuzing
items were inherited with the Blue Danube casing. The radar altimeter fuzes were omitted, and the radar-transparent thermoplastic nosecone
was replaced with a metal nose. (34)
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Safety and arming
The safety system used was inherited from the Green Bamboo design, which also had a core fabricated as a hollow spherical shell,
although smaller than Green Grass, required fewer steel balls to fill it, and that weighed considerably less at 620 lbs
(282 kg). (35)
The weight of the safety system balls in Green Grass at 1'040 lbs
(473 kg) (36) suggests a much
larger diameter for the fissile core's spherical shell , although there is as yet no declassified hard evidence.
A fire in a bomb store or a traffic collision on an airfield could result in a partial crushing or collapse of the non-removable HEU core, and in
turn a spontaneous nuclear chain reaction. AWRE responded by inserting a rubber bag, rather akin to an outsize female condom, though a
hole in the core, and filled this with 6'500 (37)
steel ball bearings weighing 1'040 lbs (473 kg). (34) That computes to
balls of one inch diameter. When Green Grass warheads installed in Violet Club were later transferred to a more modern bomb casing, Yellow
Sun Mk.1, the quantity of these steel balls was increased to 120,000 with a reduction in size to 0.375 in diameter (9.5 mm) to make removal
easier, (38)
and there is a claim elsewhere in a book commissioned by the MoD that the quantity was increased yet further to
133'000, (39) which suggests that
the ball diameter was reduced further to approximately 9mm. The balls were retained in the device by sealing the hole with a
bung. (40)
The steel balls were intended to prevent a nuclear detonation even if the explosives fired accidentally, or in any conceivable accident. The ball
bearings had to be removed through the hole in the bomb casing during flight preparation, after the bomb was winched into the aircraft. The
ball bearings then had to be re-inserted into the lowered and upturned bomb before transport back to the bomb store. The batteries were also
installed before flight, and the neutron generator enabled, and without the final safety device of the ball bearings installed, these weapons
were armed and live, and the RAF view was that they were too dangerous to be flown on exercises. Bomber Command exercises
demonstrated that flight preparation followed by a scramble take-off could not be reduced below thirty minutes with the Green Grass warhead
fitted into the improved Yellow Sun
casing, (41)
and on exercises in bad weather and at night, a ninety minute scramble was the
norm. (42)
An accident was reported in the autumn-winter-spring of 1958-59 when the steel ball retaining bung was inadvertently removed and 6'500 one inch diameter steel
ball bearings the size of gobstoppers exited onto the
floor, (43)
leaving the bomb armed and vulnerable, and the Royal Air Force were so nervous of the outcome of a fire in storage, that permission was
sought to store the bombs inverted, so that a loss of the bung could not end with the steel balls on the floor, and the HEU unprotected
against a subsequent explosion. (44)
Even without the partial nuclear detonation feared by the RAF, there was "a risk of catastrophe". (45)
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Deployment and carriage
Deployment was to be at RAF Wittering and Vulcan squadrons at RAF Finningley and Scampton, although at Scampton a problem arose
because there were no suitable storage and workshop facilities on base at Scampton. The weapon was to be stored nearby at Scampton's
off-base specialist weapon storage and maintenance facility at RAF Faldingworth, seven miles away. The embargo on transport of assembled
Violet Club weapons on public roads was a subject of much head-scratching, and there are declassified files that show that an exception was
made for this site. (46)
The first weapon was delivered in April 1958, and the fifth and last was due for delivery on 27 November
1958, (47)
although there are suggestions that this date may have slipped to May 1959, just in time to be retired from
service. (48)
Carriage was by Vulcan medium bombers only, the Victor being later into service, with release at high altitude only, using the same
techiques as adopted for Blue Danube. The Violet Club casing had identical ballistic properties to Blue Danube to minimise development time
and cost.
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RAF dissatisfaction
Violet Club/Green Grass struggled to meet the Chiefs of Staff requirement for a high yield Interim Megaton Weapon as specified with a
megaton range yield. It was a cobbling together of elements of at least two other designs, Green Bamboo and Orange Herald, both inherently
unstable designs, each with fissile cores that were greater than one uncompressed critical mass. A hastily devised nuclear safety mechanism
added to overcome the warhead's inherent instability was less than adequate to ensure safety in several scenarios identified by the RAF. One
such scenario was that of an aircraft fire while a Violet Club bomb was loaded in the aircraft with the safety balls removed. The best advice
AWRE could offer was to drench the area with fire retardant while lowering the weapon to the ground for a quick getaway. Or lowering the
weapon to re-insert the steel balls. (49)
Without the steel balls inserted, a road traffic accident on the airfield that crushed or deformed the hollow spherical fissile core was sufficient
to initiate uncontrolled fission. With 1'500 lbs (689 kg) of HE in the bomb, (50) a large 'dirty bomb' was a real possibility, and contributed to the restrictions on road
movement on and off base.
Violet Club had to be armed before flight and take-off was likely to be hazardous, and therefore the weapon couldn't be used on an
airborne alert, (51) and couldn't be
jettisoned when armed. Landing on return to base with an armed bomb was too hazardous to contemplate. The aircraft's bomb release
mechanism's ferry flight weight limit of 11'100 lbs was inadequate for the bomb with the ballbearing safety device
installed, (52) so Violet Club couldn't
be flown to a remote dispersal base in accordance with RAF strategy planned for periods of heightened international
tension, (53) and that was a source of
great disatisfaction for the RAF, because the dispersal plan was central to RAF strategy. Strategic Air Command bomber bases were mostly
located deep within the North American landmass, and had considerable warning time before short-range missiles launched from off-shore
could reach their bases, and had adequate time to scramble their aircraft. Unlike SAC, all ten RAF Bomber Command main bases were within
range of short-range missiles launched from off-shore or Eastern Europe, and had only minutes after receipt of warning in which to scramble
their aircraft. The ten main bases were therefore supplemented by twenty-six dispersal airfields, located from Kent, close to the English Channel,
to Cornwall, Wales and Ulster in the west, to the north east and the Western Isles of Scotland. At times of international tension, bombers were to
disperse with their weapons around these distant airfields. Violet Club, being unmovable by road when assembled, unarmed, and not able to be
flown unarmed to the bomber's disperal airfield, effectively wrecked RAF strategic dispersal plans. The RAF were aware of these shortcomings
when they agreed to accept Violet Club as an emergency capability weapon for a short period, with the proviso that after approximately one
year a more developed variant of the Green Grass warhead fitted into a better, modern casing, Yellow Sun, would be introduced. It would have
in-flight arming with a mechanism to jettison the steel ball safety device only if the bombers were ordered beyond their fail-safe point. RAF
chagrin was in large part because that improved weapon was never produced, and the Green Grass ground-armed warhead installed in Yellow
Sun casings soldiered on for four years, until 1963, after the Cuban Missile Crisis, with the RAF unable to disperse its bombers.
The warhead installed in Violet Club was never proof-tested, and AWRE estimated its yield at 500 kilotons, based on the Christmas Island
test of Orange Herald. Mr W.J.Challens of AWRE who later became the Director of AWRE claimed to the Air Staff that it met the specification
because
A weapon of one half megaton is considered to be in the megaton range." (54)
A statement that returned to haunt AWRE when later estimates revised the yield downwards to 400 kt. (55)
Challens also stated to the Air Staff on behalf of AWRE that
"AWRE were almost completely sure that a nuclear explosion would not occur if the balls are in -
but in the absence of trial-proof he could not guarantee it."
(56)
It is hardly surprising that his qualification of 'almost' did not instil confidence in the Service users, and the non-nuclear elements of
the weapon were not adequately tested either, as this RAF Bomber Command instruction indicates.
"Aircraft engines must not be run with Violet Club loaded on the aircraft with the safety
device [of steel balls] in place. The engines must not be started until the weapon is prepared
for an actual operational sortie." (57) [To prevent the balls vibrating like a bag of jellybeans].
" ... uncertainty exists about the effects of movement with the balls inserted." (58)
Other engineering specialists were also unimpressed with the warhead. Dr S.Jones, writing on behalf of the Armaments Dept at the Royal Aircraft Establishment at Farnbourgh described the nuclear safety device as a:
"very unsatisfactory type of nuclear safety device that was essential for Green Grass ... " (59)
A senior officer, an Air Commodore, the Director of Operations at Bomber Command, writing on 26 Jan 1959, referring to the flight preparation time and recall after take-off said:
"I think the twenty minutes required to make the weapon 'ready' [for take-off] impacts on Bomber
Command's plans to no small extent: and it is not very 'safe' once this action has commenced.
Return to base after recall, may be hazardous. We want a better safety device." (70)
A Wing Commander at RAF Bomber Command, a Bomber Operations staff officer, minuted his senior, the Air Commodore quoted above with this comment,
dated May 1959:
"This minute means that Violet Club and Yellow Sun [both with the Green Grass warhead]
are not "in the megaton range" at all, notwithstanding the extraordinary measures taken
and costs involved for what we thought to be a megaton capability. This ... leads me to the
belief that production of Green Grass be curtailed. I cannot imagine any commercial
organisation continuing to buy a device that so patently fails to meet the requirement,
or to be misled without protest as the Air Ministry has so consistently been by AWRE." (71)
Summing up, senior officers at RAF Bomber Command believed they had been sold a 'lemon', and an expensive one too.
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Storage, maintenance and servicing
The complete weapon was not of the modern variety of nuclear weapon that is not normally servicable by the armed forces in the frontline, and
returned at intervals to the manufacturer for service. Violet Club, like Blue Danube before it, was intended to be serviced by the user, the
RAF, at air bases, without assistance from the civilian manufacturers. However, the RAF had little experience of nuclear weapons, security was
very restrictive, and few people outside AWRE had a firm understanding of nuclear technology, or the associated fuzing and firing technologies.
The weapon was not supplied to the RAF whole, fully assembled, ready for use, but as a series of parts, some major sub-assemblies, eg. the
nose section, the tail section, the centre section, and the warhead. Unlike the earlier Blue Danube weapon, the fissile core of Green Grass was
an integral part of the warhead and could not be removed without a complete strip-down of the warhead. The unstable nature of the warhead,
with its fissile core greater than one uncompressed criticial mass, precluded it being assembled before delivery, and so was assembled on
each airbase by a team of civilian staff from AWRE, with some assistance from RAF technicians. (62)
AWRE stipulated that each Green Grass warhead must be stripped-down at six-monthly intervals (63)
for a thorough inspection, taking three weeks per weapon, and done by AWRE civilian staff at RAF air bases, with some help from the RAF. A
further impediment was the restriction placed on locating more than two weapons in the same maintenance and storage building, and not closer
together than six feet. (64) A great
strain was placed on the RAF's other operational requirement to service Blue Danube weapons in the available facilities. The RAF were
unhappy with these arrangements, and the poor standard of design of Green Grass that had led to that situation.
AWRE were concerned to restrict knowledge of the inner workings of the weapon to as few people outside AWRE as possible. (65)
Their civilian staff were doing the routine maintenance work at airbases that senior RAF staff officers considered should be done by uniformed
personnel in order to comply with the Geneva Convention, which forbade civilian workers being used in the front line preparing weapons for
use. (66)
Attempts by the RAF and Air Ministry to produce a service manual TSD.779 vol 1 (67) for
uniformed servicemen met with determined opposition from AWRE at the highest
level, (68) which at one stage refused
to co-operate with production of a maintainer's manual, claiming that the manual jeopardised security, and that RAF maintainers had no need to
know what was inside the weapon, and what uniformed service personnel could not see, they did not need to know of. (69)
RAF staff officers and the Air Ministry asserted their right to determine the security procedures with the Service, and that their servicing policy would not be determined
by an external, civilian research establishment, (70) if
the RAF were to assume full responsibility for storage, maintenance and security of the weapon. The RAF asserted that some knowledge of the
inner workings and content of the warhead was essential to Service morale and efficiency. (71)
Without the limited knowledge contained within a service manual, their servicing personnel would not be able to carry out the servicing
task, (72) morale would decline, and
safety would be compromised. RAF engineering staff officers recommended that the RAF should only accept responsibility for the safe custody
of Violet Club, with AWRE completely responsible for everything concerning maintenance and preparation, and that the RAF should not accept
any delegation of servicing tasks until a servicing manual was issued to RAF engineering personnel. (73)
Storage temperature limitations were exacting. (74) The
limits specified were principally aimed at maintaining the HE implosion material in good condition, controlling differential rates of thermal
expansion and contraction between the HE and other components, and prevention of cracking and distortion of the HE. Short-term temperature
limits set for an operational mission were less restrictive initially at 5°C - 40°C, but later raised to 18°C - 40°C, while in the aircraft's heated
bomb bay. Long-term ground storage temperature limits were more rigorous at 18°C - 28°C in heated and air-conditioned magazines.
Weapons held at immediate readiness for 30 days alongside the aircraft on the airfield, were stored inside a heated pantechnican parked
alongside each aircraft, and temperature limits were as for the heated aircraft bomb bay, with some parts of the weapon kept warm using
an electric blanket.
The large amount of high explosive (approx 1'500 lbs or 682 kg) contained in each weapon was as great a concern as radioactive components,
and the number permitted in each storage building was strictly limited to two, and not closer together than six feet.
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Variants
There were no variants or derivatives of Violet Club, although the warhead itself, Green Grass, was used in a later weapon, Yellow Sun Mk.1,
and there were plans to install Green Grass in the Avro Blue Steel Mk.1 stand-off bomb carried by Vulcan and Victor medium bombers. These
plans were cancelled when a better warhead was made available after the 1958 US-UK Mutual Defence Agreement, often referred to
informally as the 1958 Bi-Lateral.
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Further development
There was no further development of Violet Club. It was a one-off design, with no development potential, and was succeeded by a
radically different concept, the fission-fusion-fission type of thermonuclear warhead, referred to above as the Type B.
The Interim Megaton Weapon, alias Knobkerry, alias Green Grass, that wasn't really of megaton yield, used in Violet Club and Yellow Sun Mk.1
had another distinction. It was the last entirely British nuclear weapon deployed with the RAF. All later weapons were of entirely American
design, or had significant amounts of American design know-how incorporated in their design following the 1958 Bi-Lateral. The RAF never
deployed a thermonuclear weapon of wholly home-grown design. Although lessons were undoubtedly learned from them, and some features
incorporated into later warheads, the thermonuclear devices tested in the atmosphere at Christmas Island in Operation Grapple were all
abandoned, because AWRE no longer had any need for them. They were all experimental devices that required further work, time, and
considerable amounts of money to develop them into reliable weapons able to withstand the rough-and-tumble of Service life. The American
designs offered in late 1958 were fully tested and Service-engineered, and cheap to produce. (75)
They were manufactured in Britain from British materials (athough many non-nuclear components were purchased in the United
States) (76) from American-supplied
blueprints. (77) They were British
property, and there were no American political constraints on their independent use. For the Treasury, the deal must have appeared truly
wonderful. Violet Club and Yellow Sun Mk.1 bridged the gap for a few short years until these American designed warheads became available.
Unlike the earlier weapons deployed with the RAF, Blue Danube and Red Beard, the fissile material for Violet Club was embedded in the
implosion sphere (78) and could not
be removed and stored separately. Also, unlike the earlier weapons, they did not use a plutonium fissile core, instead using HEU for the
reasons stated above. They were very large and 'dirty' fission weapons; the largest pure or unboosted fission bombs deployed by any nuclear
power before or since.
Although a fission warhead of any given yield would use more
HEU (79) (and be less expensive)
than a warhead constructed from plutonium, a fission weapon of Violet Club size was simply impossible to construct with a plutonium core
with the technology available, because the problems associated with predetonation, caused by Pu-240 impurities in reactor-produced Pu-239
were insurmountable, at that time, and with this design. With the technology of the period, HEU was the only possible usable fissile material for
an unboosted fission weapon of this large size. Consequently, the fissile core of Violet Club was considerably cheaper built from HEU than
plutonium because the industrial costs of producing the two fissile materials was widely different, with plutonium being over 640% more costly
than HEU. (80) An added bonus was
that the United States was supplying the UK with their lower cost HEU, while the UK were able to sell their expensive and surplus military grade
plutonium to the United States, which must have cheered the Treasury somewhat. A further bonus was that US produced HEU was priced at
less than one third of the British cost of HEU production, at 1958
prices. (81) In this period, the UK
purchased over seven tons of US produced HEU, much of it finding its way into the Interim Megaton Weapon. Enough to produce
approximately one hundred Violet Club bombs.
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Retirement
All five Violet Club weapons were retired by the end of May
1959. (82) The warheads were
removed and retrofitted to the new Yellow Sun Mk.1 casings, where they were to be adapted for in-flight removal of the steel ballbearing nuclear
safety device, using the smaller balls. These plans for in-flight arming were never implemented, the equipment was never deployed, and the
Green Grass warheads from Violet Club were transferred to Yellow Sun Mk1 casings intact. The failure of AWRE and RAE at Farnborough to
implement the in-flight arming plans was a source of much of the dissatisfaction expressed by senior RAF staff officers, partly because of safety
concerns; partly because of servicing issues; but mainly because the RAF Bomber Command dispersal plan was unusable.
The casings were scrapped, and none survive in museums. The five Green Grass warheads from Violet Club with a further thirtytwo warheads
built for Yellow Sun Mk.1 survived until 1963 when all were replaced by thermonuclear warheads of American design.
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Where can I see one?
There are no surviving examples of either Violet Club, the Green Grass warhead alias Knobkerry, the Interim Megaton Weapon. Only one
similar bomb carcass, an example of Blue Danube, survives in the AWE Historical Collection. This collection is kept on a secure site at AWE
Aldermaston, which is closed to the general public. Only in exceptional circumstances will AWE and the MoD invite bona-fide researchers to
view the collection.
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 A Blue Danube casing, externally
identical to the casing used for Violet Club.
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Writer's Personal Note
The carcases (bomb casings) for Violet Club were of the Blue Danube bomb casing design with some minor internal changes to the nose and
centre sections. The tails were identical. All were manufactured by Hudswell Clarke & Co Ltd at their Roundhay Road plant in Leeds, Yorkshire,
formerly used by Blackburn Aircraft to manufacture Fairy Swordfish and Barracuda torpedo bombers, the Supermarine Sea Otter air-sea rescue
flying boat, the Blackburn Firebrand naval fighter and torpedo bomber, and other naval aircraft of
WW2. (83)
This writer was employed there as a (very) junior design engineer, initially charged with making tea and being a 'gofor' (as in go for some fish
and chips). Over several years from 1955 I worked on Violet Club, Blue Danube, Red Beard, all the Maralinga and Christmas Island airdrop test
casings, and numerous other less well documented projects, both in the design offices, workshops and assembly areas, with access to every
aspect of the weapons. At the end of 1958, shortly before I moved on to work on new projects, Chief Designer Shaw and the Production
Manager (a higher form of gofor) received their reward, in the form of a gong, an MBE each in the New Year Honours List. Presumably awarded
on behalf of us lesser mortals who did the actual hard graft behind a drawing board. No computers then! Not even a pocket calculator had been
invented. The best we had was a set of log tables and a slide rule. But we managed OK I believe.
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References
- Dr Richard Moore. Visiting Research Fellow, Mountbatten Centre for International Studies, University of Southampton.Nuclear Illusion, Nuclear Reality. Britain, the United States and Nuclear Weapons,1958-64. Palgrave-Macmillan 2010. ISBN 978-0-230-23067-5
- W.Cocroft and R.Thomas. Cold War, Building for Nuclear Confrontation 1946-1989, English Heritage, 2003. ISBN 1-873592-69-8
- nuclearweaponarchive.org
- Dr Richard Moore, Visiting Research Fellow, University of Southampton. A Glossary of Nuclear Weapons. 'Prospero' Journal of BROHP Spring 2004.
- University of Southampton, Mountbatten Centre for International Studies/Nuclear History Working Paper No1.
- http://www.skomer.u-net.com/projects/bluedanube.htm Dated, but still a superb source.
- A.J.R.Groom. British thinking about nuclear weapons.
Published Francis Pinter Ltd, London, 1974. ISBN 0-903-804-018 Dated, but a superb source for the political background for the early Cold War period.
- Humphrey Wynn. RAF Strategic Nuclear Forces: their origins, roles and deployment 1946-69. Published HMSO London, 1994. ISBN 0-1177-2833-0 Copyright MoD.
- Lorna Arnold. Britain and the H-Bomb. Published MacMillan-Palgrave, London 2001. ISBN 0-333-75685-0 softback. Copyright MoD.
- Lorna Arnold. A Very Special Relationship: British Atomic Weapon Trials in Australia. Published by HMSO, London, 1987. ISBN 0-11-772412-2
- Norris R.S, Burrows A.S and Fieldhouse R.W. The Nuclear Weapons Databook Vol 5. British, French and Chinese Nuclear Weapons.
Published by the Westview Press, Oxford, 1994. ISBN 0813 31612 X
- Professor J.E.Harris, MBE, FREng, FRS, FIM. Interdisciplinary Science Reviews. Plutonium: from stardust to Star Wars.
Published ISR 2001, London, Vol 26 No 1. ISSN 0308 0188
- Professor J.E.Harris, MBE, FREng, FRS, FIM. Interdisciplinary Science Reviews. The threat of nuclear terrorism.
Published ISR 1999, London, Vol 4 No 2. ISSN 0308 0188
- avrovulcan.org.uk/nukes/violetclub.htm Photo of Green Grass, the Interim Megaton Weapon shown here.
- avrovulcan.org.uk/nukes/bluedanube.htm Photo of the Blue Danube bomb casing used for Violet Club, shown here
- BANG, from the Joy of Hi-Tech by Rodford Edmiston.
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Footnotes
- TNA (the National Archives, London). AIR 2/13759 E18B. Megaton bomb (Zodiac Mk 3). ^ up
- TNA AIR 2/13759 E14A p1. Megaton bomb (Zodiac Mk 3). ^ up
TNA AIR 2/13759 E18B. Megaton bomb (Zodiac Mk 3). ^ up
- Lorna Arnold. Britain and the H-Bomb, p61-62, 66, 84. Published MacMillan-Palgrave, London 2001. ISBN 0-333-75685-0 hardback,
ISBN 0-333-94742-8 softback, in North America: ISBN 0-312-23518-6 hardback. Copyright MoD. ^ up
- Dr Richard Moore: University of Southampton, Mountbatten Centre for International Studies: Nuclear History Working Paper No1. ^ up
- Humphrey Wynn. RAF Strategic Nuclear Forces: their origins, roles and deployment 1946-69, p193. Published HMSO, London, 1994. ISBN 0-1177-2833-0 Copyright MoD. ^ up
- TNA AVIA 65/1193 E1 and E5 part transcription. Warhead for a medium range missile: Air Staff requirement OR 1142 Orange Herald (DAW plans action) 1955-1958. ^ up
- Lorna Arnold. Britain and the H-Bomb, p87. ^ up
- TNA AIR 2/13746 E16A p1. Warhead for medium range ballistic missile BLUE STREAK (OR 1139 and 1142) 1955-1960. ^ up
- TNA AB 16/1888 E111. Grapple 1 and Green Bamboo weapons tests; finance. ^ up
- TNA AB 16/3878 Appendix 4. Forward prices of fissile materials covering dates 1957-1961. ^ up
- TNA AIR 2/13759 E14A p1. Megaton bomb (Zodiac Mk 3). ^ up
- TNA AIR 2/13759 E18B. Megaton bomb (Zodiac Mk 3). ^ up
Lorna Arnold. Britain and the H-Bomb, p147, p236. ^ up
- Lorna Arnold. Britain and the H-Bomb, p147. ^ up
- Dr Richard Moore: University of Southampton, Mountbatten Centre for International Studies: Nuclear History Working Paper No1. ^ up
- TNA AIR 2/13680 E11A. Megaton bomb (OR 1136) 1954-1956. ^ up
TNA AIR 2/13680 E46B. Megaton bomb (OR 1136) 1954-1956. ^ up
TNA AVIA 65/1116 E18 p4. MoD Defence Research Policy Committee: Atomic Energy Sub-Committee; agenda and minutes. ^ up
- TNA AIR 2/13680 E46B p1 para 2. Megaton bomb (OR 1136) 1954-1956. ^ up
- TNA AIR 2/13680 E11A. Megaton bomb (OR 1136) 1954-1956. ^ up
TNA AIR 2/13680 E46 p1-2 para 5. Megaton bomb (OR 1136) 1954-1956. ^ up
- TNA AIR 2/13680 E46B p02 (c). Megaton bomb (OR 1136) 1954-1956. ^ up
- TNA AIR 2/13718 E24 pages 1-2. Violet Club: policy, 1957-1958. Letter from ACAS (OR) to DCAS notifying him 14 April 1958, of formal clearance for Service use of Violet Club received from DGAW and transmitted to C-in-C Bomber Command 11 April 1958. ^ up
- TNA AVIA 65/1218 E167. Violet Club correspondence 1957-1959. ^ up
- TNA AIR 2/13718 E24B. Violet Club: policy, 1957-1958. Letter from ACAS (OR) to C-in-C Bomber Command, 11 April 1958. ^ up
TNA AIR 2/13718 E24B Annex 1, p2. Violet Club: policy 1957-1958. Annex to ACAS (OR) letter to C-in-C Bomber Command, dated 11 April 1958. ^ up
- TNA AIR 2/13718 E24B. Violet Club: policy, 1957-1958. Letter from ACAS (OR) to C-in-C Bomber Command, 11 April 1958. ^ up
- TNA AVIA 65/1218 E38. Violet Club correspondence 1957-1959. ^ up
- TNA AVIA 65/1218 E35. Violet Club correspondence 1957-1959. ^ up
- TNA AVIA 65/1155 E194, para 11. 10'000 lb HE MC bomb: ASRs 1947-1962. ^ up
- TNA AIR 2/13705 E27A. Yellow Sun: policy 1957-1966. ^ up
- TNA AB 43/92 E46 p1. Fissile material costs. 1963-1965. ^ up
- nuclearweaponarchive.org. Library/Fission ^ up
- English Wikipedia Little Boy basic weapon design. ^ up
- TNA AVIA 65/1218 E183(a). Violet Club correspondence 1957-1959. ^ up
- TNA AIR 2/13705 E15A p2 para I. Yellow Sun: policy 1957-1966. ^ up
TNA AVIA 65/1218 E43. Violet Club correspondence 1957-1959. ^ up
- TNA AIR 2/13705 E56A. Yellow Sun: policy 1957-1966. ^ up
TNA AIR 2/13705 E58A. Yellow Sun: policy 1957-1966. ^ up
- TNA AIR 2/13718 E7A (4). Violet Club: policy 1957-1958. ^ up
- TNA AIR 2/13718 E24B p1 para 4. Violet Club: policy, 1957-1958. Letter from ACAS (OR) to C-in-C Bomber Command, 11 April 1958. ^ up
TNA AIR 2/13718 E21A p1 para 3. Violet Club: policy, 1957-1958. Statement by W.J.Challens on behalf of AWRE, recorded in the minutes of a conference at the Air Ministry to discuss the acceptance standard of Violet Club. ^ up
- TNA AIR 2/13681 E17A p3 para 2.2. Megaton bomb (OR 1136) 1957. ^ up
- TNA AVIA 65/777 E2. Blue Steel warhead: installation 1957-1959. ^ up
- Royal Air Force Historical Society Journal No26 (2001) p96 ISSN 1361 4231 Report of a seminar on the RAF experience of nuclear weapons. Air Commodore Owen Truelove, an Engineer Officer nuclear weapons specialist's account. ^ up
- TNA AVIA 65/777 E9 p3. Blue Steel warhead: installation 1957-1959. ^ up
TNA AVIA 65/777 E37 p4. Blue Steel warhead: installation 1957-1959. ^ up
- David J.Hawkins. Keeping the Peace, the Aldermaston Story, p52 para 03. Published Pen and Sword Books in association with AWE plc Media and publishing group. 2000. ISBN 0-85052-775-9 Crown Copyright 2000. An account commissioned by the MoD written by a former Manager of Corporate Communications at AWE. Although useful in parts it should not be overlooked that this is written by a former PR officer at AWE, tasked with producing an account for AWE's public relations group. ^ up
- TNA AVIA 65/1218 E15. Violet Club correspondence 1957-1959. ^ up
- TNA AIR 2/13705 E62A. Yellow Sun: policy 1957-1966. ^ up
- TNA AIR 2/13705 E62A. Yellow Sun: policy 1957-1966. ^ up
- Royal Air Force Historical Society Journal No26 (2001) p96 ISSN 1361 4231 Report of a seminar on the RAF experience of nuclear weapons. Air Commodore Owen Truelove, an Engineer Officer nuclear weapons specialist's account. ^ up
- TNA AIR 2/13705 E36A. Yellow Sun: policy 1957-1966. ^ up
TNA AVIA 65/1218 E181. Violet Club: correspondence 1957-1959. ^ up
TNA AVIA 65/1218 E183. Violet Club: correspondence 1957-1959. ^ up
TNA AVIA 65/1218 E191. Violet Club: correspondence 1957-1959. ^ up
- TNA AIR 2/13705 E47A p3. Yellow Sun: policy 1957-1966. ^ up
TNA AIR 2/13705 E62A p2. Yellow Sun: policy 1957-1966. ^ up
TNA AIR 2/13718 E24B p1 & 2, paras 4 & 6. Violet Club: policy, 1957-1958. ^ up
TNA AIR 2/13718 E24B Annex 1, p3, para 13, item (i). Violet Club: policy 1957-1958. Annex to ACAS (OR) letter to C-in-C Bomber Command, dated 11 April 1958. ^ up
- TNA AIR 2/13705 E25A. Yellow Sun: policy 1957-1966. ^ up
TNA AIR 2/13705 E36A. Yellow Sun: policy 1957-1966. ^ up
TNA AIR 2/13705 E38A. Yellow Sun: policy 1957-1966. ^ up
- TNA AIR 2/13705 E23A. Yellow Sun: policy 1957-1966. ^ up
- TNA AVIA 65/1116 E20. MoD Defence Research Policy Committee: Atomic Energy Sub-Committee; agenda and minutes 1957-1960. ^ up
- TNA AIR 2/13718 E17A (c). Violet Club: policy 1957-1958. ^ up
TNA AIR 2/13718 E24B Annex 1 p3. para 13 item (i). Violet Club: policy 1957-1958. Annex to letter from ACAS (OR) to C-in-C Bomber Command, dated 11 April 1958. ^ up
- TNA AVIA 65/777 E35 p5. Blue Steel warhead: installation 1957-1959. ^ up
- TNA AIR 2/13718 E24B Annex 1 p2. para 12. Violet Club: policy 1957-1958. Annex to letter from ACAS (OR) to C-in-C Bomber Command, dated 11 April 1958. ^ up
- TNA AVIA 65/1218 E35. Violet Club correspondence 1957-1959. ^ up
- Humphrey Wynn. RAF Strategic Nuclear Forces: their origins, roles and deployment 1946-69, p448, Dispersal Map. Published HMSO London1994. ISBN 0-1177-2833-0 Copyright MoD. ^ up
- TNA AIR 2/13718 E21A p2 para 8. Violet Club: policy, 1957-1958. Statement by W.J.Challens on behalf of AWRE, recorded in the minutes of a conference at the Air Ministry to discuss the acceptance standard of Violet Club. ^ up
TNA CAB 21/4533 E3 page 2. Cabinet papers: nuclear weapons nomenclature: policy. 1955. ^ up
- TNA AIR 2/13705 E56A. Yellow Sun: policy 1957-1966. ^ up
TNA AIR 2/13705 E58A. Yellow Sun: policy 1957-1966. ^ up
TNA AIR 2/13705 E61A. Yellow Sun: policy 1957-1966. ^ up
- TNA AIR 2/13718 E21A p2 para 8. Violet Club: policy, 1957-1958. Statement by W.J.Challens on behalf of AWRE, recorded in the minutes of a conference at the Air Ministry to discuss the acceptance standard of Violet Club. ^ up
TNA CAB 21/4533 E3 page 2. Cabinet papers: nuclear weapons nomenclature: policy. 1955. ^ up
- TNA AIR 2/13718 E15A (3) (d). Violet Club: policy 1957-1958. ^ up
- TNA AIR 2/13718 E21A p2, para 7, item 14, and p2, para 8, item 15. Violet Club: policy 1957-1958. ^ up
- TNA AVIA 65/777 E75 p4(9)(a). Blue Steel warhead: installation 1957-1959. ^ up
- TNA AIR 2/13705 E30A. Yellow Sun: policy 1957-1966. Handwitten addendum. ^ up
- TNA AIR 2/13705 E59A. Yellow Sun: policy 1957-1966. ^ up
- TNA AIR 2/13718 E24B p1 para 3. Violet Club: policy, 1957-1958. Letter from ACAS (OR) to C-in-C Bomber Command, 11 April 1958. ^ up
TNA AIR 2/13718 E24B Annex 1, p1, para 3. Violet Club: policy, 1957-1958. Annex to ACAS (OR) letter to C-in-C Bomber Command, 11 April 1958. ^ up
- TNA AIR 2/13705 E27A p1, para 3. Yellow Sun: policy 1957-1966. ^ up
- TNA AIR 2/13718 E24B Annex 1, p1, para 6. Violet Club: policy, 1957-1958. Letter from ACAS (OR) to C-in-C Bomber Command, 11 April 1958. ^ up
- TNA AIR 20/11316 E12B p1(a). Nuclear weapons service manuals: policy 1958. ^ up
- TNA AIR 20/11316 E17A p2, para 4(a). Nuclear weapons service manuals: policy 1958. ^ up
TNA AIR 20/11316 summary p2, para 4(a). Nuclear weapons service manuals: policy 1958. ^ up
- TNA AIR 20/11316 E1A p1. Nuclear weapons service manuals: policy 1958. ^ up
TNA AIR 2/13718 E24B p1 para 4. Violet Club: policy, 1957-1958. Letter from ACAS (OR) to C-in-C Bomber Command, 11 April 1958. ^ up
- TNA AIR 20/11316 E3A p1, para 6. Nuclear weapons service manuals: policy 1958. ^ up
- TNA AIR 20/11316 E3A p1, para 1(a). Nuclear weapons service manuals: policy 1958. ^ up
- TNA AIR 20/11316 E4A para 4. Nuclear weapons service manuals: policy 1958. ^ up
TNA AIR 20/11316 E4B para 9, para 10. Nuclear weapons service manuals: policy 1958. ^ up
- TNA AIR 20/11316 E1A p1, para 3(a). Nuclear weapons service manuals: policy 1958. ^ up
- TNA AIR 20/11316 E3A p1. Nuclear weapons service manuals: policy 1958. ^ up
- TNA AIR 20/11316 E3A p1, para 6. Nuclear weapons service manuals: policy 1958. ^ up
TNA AIR 20/11316 E4B p1, para 5, para 9, para 10. Nuclear weapons service manuals: policy 1958. ^ up
- TNA AVIA 65/1218 E24. Violet Club correspondence 1957-1959. ^ up
- TNA AVIA 65/1771 E24 p1, para 3. Defence Committee on Nuclear Requirements 1959-1963. ^ up
- TNA AVIA 65/1064 E74 p1, p2. Inspection of atomic weapons 1958-1960. Twenty items and sub-assemblies purchased in the United States for Red Snow production in the United Kingdom. ^ up
- Lorna Arnold. Britain and the H-Bomb, p214. ^ up
Lorna Arnold. Britain and the H-Bomb, p213. Over 6'000 individual component and assembly blueprints. ^ up
- TNA PREM 11/2944 E185A. Prime Minister's papers. Red Snow thermonuclear warhead manufacture at Burghfield: transportation issues 1959-1960. ^ up
TNA PREM 11/2944 E185B. Prime Minister's papers. Red Snow thermonuclear warhead manufacture at Burghfield: transportation issues 1959-1960. ^ up
- Charles S.Grace. Nuclear Weapons: Principles, Effects and Survivability. Published: Royal College of Military Science, Shrivenham, Wiltshire, UK, and Brasseys, 1994. ISBN 0-0804-0992-X ^ up
- TNA AB 16/3878 Appendix 4, p1. Forward prices of fissile materials. 1957-1961. Letter dated 07 March 1959 from AEA to DAWRE. ^ up
- TNA AB 16/3878 Appendix 4. Forward prices of fissile materials. 1957-1961. Attached handwritten note identifies the US price of HEU @ £6'000/kg at 1958/59 prices, and the cost to the RAF from UK production as £21'000/kg at 1958/59 prices. Cost of Pu-239 to the RAF from UK production was £135'000/kg at 1958/59 prices. ^ up
- TNA AVIA 65/1116 E20. MoD Defence Research Policy Committee: Atomic Energy Sub-Committee; agenda and minutes. ^ up
- Wikimapia entry accessed 10.53 GMT 23 June 2010. ^ up
Hudswell Clarke & Co Ltd Wikipedia entry accessed 10.53 GMT 23 June 2010. ^ up
Fairey Swordfish Wikipedia entry accessed 10.53 GMT 23 June 2010. ^ up
Fairey Barracuda Wikipedia entry accessed 10.53 GMT 23 June 2010. ^ up
Supermarine Sea Otter Wikipedia entry accessed 10.53 GMT 23 June 2010. ^ up
Blackburn Firebrand Wikipedia entry accessed 10.53 GMT 23 June 2010. ^ up
Leeds Civic Trust Blue Plaque Awarded to Blackburn Aircraft site. ^ up
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Violet Friend
Under construction.
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Violet Mist
Under construction.
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Violet Vision
Under construction.
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Vixens (generic)
Under construction.
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Volcano
Under construction.
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WE.148
Under construction.
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WE.155
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Function
WE.155 was a watertight and airtight storage and transport container adaptable for all versions of the WE.177 bomb. The short version
used for the WE.177A tactical bomb was made up of only two sections, the nose and the tail sections bolted together, and lengthened to
accommodate WE.177B and WE.177C by the insertion of a 21 inch section bolted into the centre.
Its function was to protect the weapon from climatic conditions, rough handling and accidents, including fire, and being lost overboard from
ships. It was designed to float in seawater while fully loaded to enable recovery, and it was insulated to ensure a slow rate of heat transfer if
exposed to fire.
Although little is known from declassified sources of the environmental standards required for storage of the WE.177 weapon, standards
were less demanding than for the earlier weapons replaced by WE.177, which required self-sufficient air-conditioned storage, powered by their
container's own internal diesel generators. WE.155 containers had no internal power sources, no connections to external power sources, and
no air-conditioning.
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Description
Basically cylindrical in shape, divided into a forward, centre, and an aft section bolted together end-to-end as required. The sections had mild
steel inner and outer skins separated by a two inch thick filling of calcium silicate thermal insulation. The steel cylinders were strengthened by
D-shaped hoops of U-channel joined by longitudinal tubing. The hoops were attached at their lower ends to a horizontal framework of hollow
square-section members that formed a platform on which the cylinder appeared to rest. With eight adjustable legs added, this horizontal frame
forms a table-like structure onto which the cylinder was secured by the D-shaped hoops. With the legs fully raised the container can be stacked
up to three in height, allowing sufficient height clearance for forklift handling.
A hinged circular door closes the end of the forward section. The mild steel door encloses a fire break of two inch thick layer of calcium silicate,
- a material intended to slow heat transmission to the container's contents. Six radially distributed locking bars lock the door closed by engaging
in slots in the container outer rim. The locking bars are activated by a spiral cam plate driven via a geartrain by a manually operated handle, and
the wedge-shaped ends of the locking bars compress the door against an 'O' ring seal. The central raised casing on the door contains the cam
plate, gears and the operating handle. A padlocked hinged flap to the right of the raised casing provides access to the operating handle.
The rear end is closed by a 'D' shaped cover bolted in position and sealed by two 'O' section rubber seals, and like the forward section door is
constructed of welded mild steel sheet enclosing a two inch thick layer of calcium silicate fire break.
Two rails joined by crossmembers are secured inside the forward section and form part of a 10-inch gauge rail system. This supports a cradle
carrying the weapon. The cradle itself is not a part of the container, but is also used in conjuction with other weapon handling, servicing and
aircraft loading equipment. The forward ten inches of the rail system hinges vertically to permit the circular door to close, and lowers into a
horizontal position, bridging a gap to weapon servicing and preparation equipment, permitting the weapon cradle to be slid along the rail, to
exit the container. Adustable legs permit the rail height to be aligned with external equipment.
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Weights and Dimensions
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WE.176
Under construction.
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Genesis
WE.176 was the warhead component (or 'physics package') for an Improved Kiloton Bomb to the twin specifications of
OR.1176 (for the warhead later known by the designator PT.176) (1) and
OR.1177(2) for
the complete weapon known as WE.177.
Development began possibly as early as 1958 (3)
as an Improved Kiloton Bomb and Red Beard replacement. The Red Beard bomb was heavy, large for fighter-bomber tactical aircraft
to carry underwing, and the storage and handling conditions, and especially the temperature limitations, were a hindrance, and it was
aerodynamically unsuitable for high-speed low-level flight, whether carried externally or internally. Highly radioactive warhead components in
the Red Beard warhead, comprising a primitive impact initiator (a neutron generator) had a life measured in months rather than years, that had
to be returned to AWRE for re-lifing every six months from locations in the UK, Cyprus, Singapore and with the Fleet. The logistical issues that
arose were severe, (4) and
in the replacement warhead, WE.176, this initiator arrangement was replaced with an Electronic Neutron Initiator (ENI).
The first generation warhead installed in Red Beard was armed before take-off with no possibility to change selections in-flight, or to
disarm the weapon for a return to base. A replacement was urgently sought, even before Red Beard entered service, and an Air Ministry
Operational Requirement was issued as OR.1176 for the warhead, and OR.1177 for the complete weapon, in Aug 1959. (5) The
RAF concluded that the 15 kt yield of Red Beard was insufficient to ensure destruction of the type of targets they were assigned, and OR.1177
as originally issued specified several non-variable, manufacturer-set yields of 50, 100, 200, and
300 kilotons(6)
in a weapon using the Una warhead (7) later
renamed Ulysses(8) and
weighing up to 1'000 lbs, and with a diameter no larger than Red Beard's at 28 inches. The Royal Navy requirement GDA.10 for
a weapon of lower yields and weight, assigned the codename Red Flag(9)
was merged into OR.1176/OR.1177 as a joint requirement, (10) and
sometime later an RAF Coastal Command requirement OR.1156, updated to OR.1178 for an anti-submarine nuclear depth
bomb (NDB) was added, (11) although
a UK-owned NDB was subsequently never issued to RAF maritime anti-submarine patrol aircraft, which only used US-supplied and
owned weapons. (12)
Although many aircraft were fitted to carry the Improved Kiloton Bomb, the main users were originally intended to be the principal tactical strike
aircraft of the RAF and Royal Navy, TSR2 (a Canberra replacement), and in the Fleet Air Arm the Buccaneer.
Design was primarily focussed on the needs of these two key aircraft, although other aircraft were included in the specification; principally, the
aircraft being developed to OR.345 that became the Harrier, the three V-bombers and Canberra. (13) Although
the Air Ministry's original OR.343 specification required Red Beard to be carried by TSR2, it was quickly realised that high drag, temperature
and other limitations made internal or external carriage of Red Beard by TSR2 impossible. Unfortunately, the dimensions of the TSR2 bomb
bay were largely determined by the dimensions of Red Beard, and in later years, when it was too late to change these dimensions, twin
carriage of WE.177 gave rise to great difficulties. In particular the RAF and Royal Navy requirement written into later issues of OR.1177 for
'stick-bombing' delivery techniques of WE.177 by TSR2 and the Buccaneer. (14)
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WE.177
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WE.177 was the last air-launched nuclear bomb deployed by the UK, and the most complex weapon ever designed for the Royal Air
Force and Royal Navy. (1) There
were three versions, all free-fall and parachute-retarded. Two of these versions, WE.177B and WE.177C were thermonuclear weapons. The
remaining version, WE.177A was a boosted fission weapon.
The first version to be deployed, the thermonuclear WE.177B, was delivered to the Royal Air Force in September 1966 followed by
deliveries of WE.177A to the Royal Navy beginning in 1969, (2) and
the RAF in 1971, after a delay caused by the need to produce the ET.317 warhead for the UK Polaris A3T first; and was followed by
WE.177C deliveries to the RAF. The Navy weapons were retired by 1992 and all other weapons with the RAF were retired by
1998. (3)
The WE.177A boosted fission weapon, deployed in 1971, was originally conceived as an Improved Kiloton Weapon to replace Red Beard,
a tactical kiloton-range bomb. WE.177A was a dual-purpose weapon, being used by RAF and Royal Navy fixed-wing aircraft as a surface
attack tactical bomb against land and sea surface targets. It could be delivered by several methods including low-level loft bombing.
Forty-three were also deployed aboard Royal Navy surface vessels of frigate size and larger for use by embarked helicopters as an
anti-submarine NDB (Nuclear Depth Bomb). (4)
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Genesis
WE.177 development began possibly as early as 1958 as an Improved Kiloton Bomb and Red Beard replacement. The Red
Beard bomb was heavy, large for fighter-bomber tactical aircraft to carry underwing, and the storage and handling conditions, and especially
the temperature limitations, were a hindrance, and it was aerodynamically unsuitable for high-speed low-level flight, whether carried externally
or internally. Highly radioactive warhead components in the Red Beard warhead, comprising a primitive impact initiator (a neutron generator)
had a life measured in months rather than years, that had to be returned to AWRE for re-lifing every six months from locations in the UK,
Cyprus, Singapore and with the Fleet. The logistical issues that arose were severe, and in the replacement warhead, WE.176, this initiator
arrangement was replaced with an Electronic Neutron Initiator (ENI).
Red Beard was armed before take-off with no possibility to change selections in-flight, or to disarm the weapon for a return to base. An
improved Mk.2 Red Beard casing with in-flight loading of the fissile core, and separately, an improved Mk.2 warhead (that could be inserted
into the Mk.1 casing) with a higher yield and fewer environmental restrictions on storage was in the development pipeline but there is no hard
evidence that the Mk.2 Red Beard warhead was ever issued to the Services. Other limitations of Red Beard remained, principally its size and
weight on aircraft and in storage, and its aerodynamic unsuitability for external carriage at high speed, and the Mk.2 Red Beard casing was
cancelled with the issue of OR.1177.(5) A
replacement was urgently sought before Red Beard entered service, and an Air Ministry Operational Requirement was issued as OR.1176 for the warhead, and OR.1177 for the complete weapon, in Aug 1959.(6)
The RAF had concluded that the 15 kt yield of Red Beard was insufficient to ensure destruction of the type of targets they were assigned, and
OR.1177 as originally issued specified several non-variable, manufacturer-set yields between 50 and 300 kilotons in
a weapon weighing up to 1'000 lbs, and a diameter no larger than Red Beard's at 28 inches.(7) The
Royal Navy requirement GDA.10 for a weapon of lower yields and weight, assigned the codename Red Flag was merged
into OR.1176/OR.1177 as a joint
requirement,(8) and
sometime later an RAF Coastal Command requirement OR.1156, updated to OR.1178 for an anti-submarine nuclear depth
bomb (NDB) was added,(9) although
a UK-owned NDB was subsequently never issued to RAF maritime anti-submarine patrol aircraft. They were issued with an American B-57 NDB from US Navy
stocks held in Europe.(10)
As originally envisaged WE.177 was to be merely a tactical nuclear weapon for use in support of land forces and at sea, as an Improved
Kiloton Bomb to the twin specifications of OR.1176 for the warhead, and OR.1177 for the complete weapon. But the early
1960's was a period of rapid change in both warhead design and delivery systems. The era of the manned high-speed, high-altitude bomber
was ending with the arrival of guided missile defences and the ballistic missile, and several false starts were made in weapon choices. Efforts
to extend the life of the RAF strategic bomber force resulted in the Blue Steel short-range stand-off bomb and the Skybolt programme. Skybolt
was intended to extend the bomber's strategic role beyond the 1970's, and when cancellation came, followed by a decision to acquire Polaris,
a gap appeared between 1965 and the arrival of Polaris in service at the end of the decade, when the RAF strategic bomber force was unlikely
to be able to penetrate Soviet defences at high-level. A stop-gap weapon was needed that would permit the bombers to penetrate at low-level,
beneath the radar, and SAM defences. That stop-gap weapon, referred to at the time occasionally as
Weapon X (11) was
the genesis of WE.177B to the specification OR.1195 for the complete weapon. It is not known if there was an Operational
Requirement specification written for the warhead only, as had been the case with WE.177A.
In this emergency, the Improved Kiloton Bomb, WE.177A, was put onto the back-burner, with efforts concentrated on the stop-gap WE.177B,
followed by the Polaris warhead, followed by WE.177A. Deployment of WE.177B began in 1966, with WE.177A service entry delayed until
1971.
OR.1176
OR.1195
It will be difficult and perhaps impossible to unscramble an account of OR.1176 that began as a requirement for a tactical warhead to
replace Red Beard, from some later additions. An account of the Improved Kiloton Warhead, the OR.1195 strategic warhead, the others in a
series of warheads proposed for Skybolt, Polaris, Blue Water and others that are inextricably linked would make little sense if dealt with
separately in isolation from each other. The account here will adopt that unified format.
OR.1176 is the Operational Requirement, or specification written for the warhead or warhead capsule. OR.1177 is the
specification written for the complete weapon, WE.177. As originally written, the warhead specification was split from the weapon specification because it was
intended that the warhead capsule could be a stand-alone product that could be used in several different weapon delivery systems, eg. bombs,
SAMs, torpedos, SSMs etc, with the capsule possibly being transferred between weapons.(12) As
is normal practice, as the OR was revised over time and the Service's requirements were more closely defined, and especially with the addition
to the requirement of a laydown capability, it became clear that the capsule would also take on the function of a 'strong' casing, inside the outer
weapon casing. All the equipment that was required to continue functioning after laydown (a controlled crash-landing) was installed inside the
'strong' casing or capsule. Equipment outside the capsule was redundant after laydown and not part of the warhead, but of the weapon. So the
warhead capsule was self-contained, with its own power supplies, and everything needed to function to
detonation.(13)
Numerous proposals were considered to meet OR.1176, some were thermonuclear devices, some boosted fission devices, and some of each
in the existing Red Beard casing. The three proposed for the Red Beard casing were:(14)
PETER
A boosted fission device, an anglicised copy of the W-34 Python primary used in the Red Snow strategic warhead and
it was already in production in the UK, so could be available quickly. Yield of 11 kt was not capable of enlargement to the sizes specified by
OR.1176/1177.
TONY
A boosted fission device, an anglicised copy of the W-44 Tsetse primary used in the RE.179 strategic warhead for Skybolt and planned for production
in the UK, so could be available earlier than a new design. Yield of 10 kt was not capable of enlargement to the sizes specified by OR.1176/1177.
RED SNOW
A thermonuclear device, an anglicised copy of the W-28 thermonuclear strategic warhead in a Red Beard casing
lengthened by 12 in to 13 ft. Yield of 1 MT was much in excess of that specified by OR.1176/1177, but could be reduced, and it was already in
production in the UK, so could be available quickly.
Two further options were then considered:(15)
PETER in a newly designed casing of uncertain size, but likely to be of approximately 20 in diameter x 125 in length.
TONY in a newly designed casing of 15 in or 16.8 in diameter x 125 in or 137 in length.
Both casings were a better aerodynamic shape than Red Beard, but with similar design features, eg. ram-air turbogenerator powered. These
five options were quickly discarded. Peter and Red Snow in either casing could be available by 1961, two to three years earlier than Tony, and
four years earlier than Ulysses or Ursula. That was an important consideration for the RAF, but the Red Beard casing was unsuitable for the
reasons referred to above, and neither Peter nor the Tony boosted-fission warhead could be sufficiently enlarged to meet OR.1176/1177,
and so the next two options were thermonuclear warheads claimed in declassified papers to be of British origin in the slimmed-down new
casing considered with Tony above. These were:(16)
ULYSSES
A thermonuclear device of UK design originally codenamed Una, later renamed
Ulysses.(17) Although
information is sparse, declassified files state that the Una/Ulysses design was based on Red Snow,(18) the
anglicised US W-28 thermonuclear warhead, with the anglicised US W-44 Tsetse warhead known as Tony substituted(19) for
Red Snow's fission primary named Peter. All of which suggests that Una later renamed Ulysses was in reality merely
a copy of Red Snow scaled down in size to fit into the available space in the Skybolt ALBM and the Blue Water SSM it was originally
intended for, with Ursula possibly an adaptation of Una/Ulysses for a different project, OR.1178, later incorporated into
OR.1177. Other declassified sketches show Tony as a primary in a casing identical to the one for Ulysses. Casing dimensions were 16.8 in
diameter x 137 in length, and with the same ram-air turbogenerator configuration as the previous sketches. Ulysses is known to be associated
with the Skybolt ALBM and a tactical battlefield SSM for the British Army, and commonality of warheads was known be a major design goal.
URSULA
A thermonuclear device, believed to be a variant of the Ulysses design, possibly intended for a different weapon project. With shorter length and
greater diameter Ursula would be too large for the bomb casing identified with Ulysses, suggesting that it was originally intended for a different
user, possibly the NDB to meet OR.1156, later OR.1178.. Designers estimated that neither Ulysses nor Ursula would be available to the RAF
before 1965.(20)
A mention should be made here of one further and final rejected option.
RED SNOW TAILORED BOMB.
Proposed by RAE Farnborough, this was a Red Snow thermonuclear warhead inserted into a new
design of casing of 21½ ins diameter, the minimum casing diameter possible with this warhead. Length was to be 156 inches, with a
longer version at 163 inches. At 1.1 megatons the yield of Red Snow was much greater than specified by OR.1176/1177 although it could be
reduced at manufacture with some saving in fissile material. The advantages offered by this option were that the warhead was of a tested and
proven design that was already in production in the UK, and could be available to the RAF by 1961, much earlier than any other option, without
the design deficiencies of the Red Beard casing, and with fewer storage limitations. It would be 25% smaller in diameter, and could be carried
externally by supersonic and transonic aircraft without the limitations imposed by Red Beard, or the stretched bluff-nosed Red Beard with Red Snow
warhead.(21)
Disadvantages were that the new 'tailored' casing would embody none of the very complex fusing and laydown features specified for
OR.1177; nor would the Red Snow warhead ever be capable of withstanding the stresses of laydown delivery. This 'tailored' design was at
best a short-term interim design.
RE.179
Simultaneously with consideration of the options for OR.1176 and OR.1177 listed above, there was a new thermonuclear warhead codenamed
RE.179 being considered with several other contenders for OR.1179, a requirement for a warhead for the Skybolt strategic
air-launched ballistic missile intended to re-arm the V-bombers. Weighing approximately 700-800 lbs, this was an anglicised copy of
the US W-59 warhead.(22) The
W.59 aka RE.179 warhead is known to be of less than 16 inches
diameter (23) and
a a sealed unit, not servicable by the end-users, with a natural uranium outer casing giving rise to handling and corrosion
issues,(24) A
fusion casing composed of natural uranium, suggests that the W-59 and RE.179 warheads were three-stage fission-fusion-fission devices. The
fission primary was an anglicised US W-44 Tsetse warhead, known in the UK as Tony.
When eventually Una/Ulysses was abandoned as the choice for OR.1176/OR.1177 along with the other contenders, and RE.179 selected as the
warhead for Skybolt, (25) its
components were also chosen as a common 'start-point' for a 'family' of similar warheads intended to arm OR.1177, OR.1195 and Blue Water.
Sound economics. Scientific manpower and other resources were scarce, and it made sense to standardise and reduce spares stockholdings.
Later, after Skybolt cancellation and cancellation of the Army's tactical battlefield missile Blue Water, the only remaining prospective
users of RE.179 components were to be the OR.1195 'stop-gap' weapon WE.177B, and a warhead for Polaris, the UK
successor to Skybolt; and further away in time, and not then fully defined were applications for a naval SAM and an army ADM. Other designs
also considered and rejected for the UK Skybolt and UK Polaris, included the British Acorn, (26) the
US W-47, (27) the
US W-56, (28) and
later for Polaris, the US W-58 warhead. (29) The
British regarded the W-47 as unsafe; (30) that
it used excessive amounts of fissile material; (31) used
a safety device of doubtful reliability; (32) that
it had corrosion problems that would degrade reliability; (33) and
its fissile core was unduly vulnerable to neutron radiation from ABMs, (34) and
rejected it. The W-56, an updated offspring of the W-47 concept and Acorn were also rejected for UK Polaris in favour of the W-58 that armed
later versions of the USN Polaris. The primary reason for prefering the W-58 was probably the desire to avoid further expensive underground
nuclear tests in the US and the W-58 was about to enter service with the US Navy in the latest hardened and cheapest Polaris variant, the A3T,
which Britain was to purchase, easing access to stocks of common spares. Then another safety issue arose with the fission primary of both the
W-58 and the W-59, the US W-44 Tsetse, to be manufactured in the UK as Tony for use as the primary in RE.179.
The US W-44 Tsetse primary used a plastic-bonded explosive (PBX-9404) (35) that was too shock-sensitive to comply with stringent British
explosives requirements. If replaced in an anglicized version of the W-44 with a less shock-sensitive British explosive, the implosion device
would generate less compression at the core, and a lower yield insufficient to guarantee ignition of the fusion
secondary. (36) The
reduction in yield was especially important at a late stage in the weapon's life-cycle of approximately three years, when in a worst case scenario,
tritium decay reduced Tony's yield to below its nominal 8½ kt ±¾ kt (37) by
approximately 5.5% annually to 6½ kt.
The British solution was to substitute a different primary based on a wholly UK design that began as Octopus, then Super
Octopus and then evolving into Cleo. Declassified files (38) describe
it as "a novel form of implosion", and it was tested (originally for the Skybolt warhead) underground at the Nevada Test Site as test Pampas
on 01 March 1962. (39)
It was the first British underground test, and its yield was 9½kT. The design incorporated gas-boosting, a composite-core and a mechanical
safing device, for the design was not inherently one-point-safe. Following Skybolt cancellation and the start of the WE.177B project there were
concerns that the mechanical safety device would not be reliable, and a modified design that had a larger HE supercharge producing more
compression at the core, a smaller core that was inherently one-point-safe, and dispensing with mechanical safing, was re-tested
as Tendrac on 07 Dec 1962. (40)
The Tendrac device became Katie, urgently required for the stop-gap weapon WE.177B to specification OR.1195.
Katie was later developed into Katie A(41) needed
for the OR.1176 Air Staff requirement for a ½ kt and 10 kt warhead for the Improved Kiloton Bomb, the naval staff requirement GDA.10 and
GDA.15 for a Red Beard replacement and NDB, and Coastal Command requirement OR.1178 for for a NDB that were all now subsumed into
the OR.1176 and OR.1177 specification. The Tendrac device was also developed into
Jennie(42) for
use as a primary in ET.317, the UK Polaris A3T warhead, and Katie A stripped of hydrostatic sensors and other NDB features was the
basis of a primary for the later variant of WE.177, the Type C, or WE.177C. (43)
Matched to Katie in WE.177B was a secondary derived from RE.179 (itself an anglicised copy of the US W-59) codenamed
Simon, (44) and
the complete WE.177B primary/secondary package was codenamed
ZA297. (45) A
similar Katie-based primary was adopted for the Polaris warheads then being designed, using scaled-down components derived from RE.179
and WE.177B. No further nuclear testing was required for the Katie device used in WE.177. The tests that followed Tendrac were concerned
only with the Polaris variant of Katie codenamed Jennie, and were known as the Polaris Economy Tests, (46) because
their objective was to economise on the scarce and expensive fissile material used in their fissile cores and as a thermonuclear 'spark-plug'.
Though it is reasonable to conclude that there were spin-offs and beneficial effects for the same basic design used in all versions of WE.177.
The RE.179-derived secondary device used in WE.177 and Polaris, known as Simon and Reggie (47) respectively,
had already been extensively tested in its original form as the US W-59 in the US Dominic test series in the Pacific in tests Questa,
Alma, Rinconada and Sunset, producing a yield of 1 MT in the Sunset test. (48)
There was no need for further tests of the fusion secondary, suggesting that RE.179, Simon and Reggie were closely related.
Other versions of Katie emerged later. Katie A also known as PT.176, is identified in declassified files with WE.177A.
Scenic (49) is
decribed as an all-oralloy Katie. Oralloy being a term used to describe weapons-grade U-235. So there was a version of Katie that used no
plutonium, although nothing is known of this version's purpose.
OR.1177
OR.1177 is the Operational Requirement, or specification written for the complete weapon WE.177 with the warhead to the separate
specification OR.1176. Proposals for an Improved Kiloton Bomb and Red Beard replacement began possibly as early as 1958, and
the first draft of OR.1177 was issued from the Air Ministry on 6 Nov 1959. The Red Beard bomb was heavy, large for fighter-bomber tactical
aircraft to carry underwing, and the storage and handling conditions, and especially the temperature limitations, were a hindrance, and it was
aerodynamically unsuitable for high-speed low-level flight, whether carried externally or internally. A replacement was urgently sought before
Red Beard entered service, and an Air Ministry Operational Requirement was issued as OR.1177 for the complete weapon, in Aug
1959 (50) to
use the warhead specified as OR.1176.
The RAF had concluded that the 15 kt yield of Red Beard was insufficient to ensure destruction of the type of targets they were assigned, and
OR.1177 specified several non-variable, manufacturer-set yields of 50, 100, 200, and 300 kilotons in a weapon weighing up to 1'000 lbs, and
not larger than the Red Beard casing diameter of 28 inches. (51) The
Royal Navy requirement GDA.10 for a weapon of lower yields and weight, assigned the codename
Red Flag (52) was
merged into OR.1176 and OR.1177 as a joint requirement, and sometime later an RAF Coastal Command requirement OR.1156 updated to
OR.1178 for an anti-submarine nuclear depth bomb (NDB) was added, (53) although
a UK-owned NDB was subsequently never issued to RAF maritime anti-submarine patrol aircraft. They were issued with an American B-57
NDB from US Navy stocks held in Europe. (54)
As originally envisaged OR.1177 was to be merely a tactical nuclear weapon for use in support of land forces and at sea, as an Improved
Kiloton Bomb, later known as WE.177.
As with many nuclear and aerospace projects of the time, OR.1177 underwent numerous revisions, attempts to reconcile the different requirements
of the RAF and Royal Navy in a common weapon casing, and attempts to design a 'common family' of warheads suitable for the Army, Navy and
Air Force. To complicate matters further, a Ministerial ruling of July 1961 endorsed by the Cabinet, still not declassified, limited all British
tactical nuclear weapons to a yield of 10 kt. (55) A
further complication was cancellation by the US of the Skybolt project. Polaris was substituted, and its warhead was eventually to be part of the
'common family' too, after several false starts. But until Polaris could relieve the RAF of responsibility for the UK's nuclear deterrent, a 'stop-gap'
weapon was urgently needed, and its warhead requirement numbered OR.1195 was also to be derived from the 'common family' of
warheads originating from OR.1177, OR.1176, a Skybolt RE.179 warhead derived from the anglicised US W-59 and W-44, and Army SSM
Blue Water warhead, also derived from the anglicised W-59 and W-44.
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GDA.10 naval requirement
GDA.15 naval requirement
GDA.10 was a naval requirement drafted in mid-1959 by the Gunnery Division (Air) for a replacement for the Red Beard bomb carried
by carrier-borne strike aircraft of the Fleet Air Arm. By December 1959 the Navy had agreed to an offer by the Air Ministry to merge GDA.10
into their OR.1177 requirement, (59) and
a process of agreeing a common requirement began. Like OR.1177, the naval GDA.10 was limited in scope to be no more than a Red Beard
replacement suitable for carriage and release at high-speed and low-level by Buccaneer aircraft and their successors, using LABS loft release.
Initially, there was no requirement for laydown release. That was added later to reduce aircraft vulnerability. (60) A
requirement for use as an anti-submarine nuclear depth bomb (NDB) either helicopter delivered or on the Ikara missile appears to have been
added later.
Maximum weight of 550 lbs was set at the limit for the shipborne Wasp helicopter. Yield requirements are still unclear, although some official
declassified sources refer to three yields of ½, 2 and 10 kt. These yields were possibly arrived at later after the NDB requirement was clarified.
The ½ kt yield being needed only for NDB use in shallow water and other specialized anti-submarine operations. The yield of the 10 kt weapon
was intended for fixed-wing strike operations. The remaining 2 kt yield is less certain, although is consistant with a long-standing naval
requirement for a suitable small warhead of that yield for the naval SAMs Sea Slug Mk.2 and Sea Dart. The 2 kt requirement was abandoned
later.(61) The
½ and 10 kt yields were eventually selected as the yields of WE.177A.
The low weight and low yields specified in GDA.10 were significantly at variance with the higher yields and weights specified in OR.1177. The
naval requirement could best be met by a boosted fission warhead as was eventually selected for WE.177A. The RAF requirement in OR.1177
for yields of 40 - 300 kt could be most economically met by a thermonuclear warhead as installed in WE.177B and later in WE.177C. Carriage
by the Wasp helicopter for anti-submarine use made weight a critical factor with little possibility of compromise, while the RAF were content with
a weapon weighing up to 1'000 lbs; much too heavy for the Wasp and its successors.
Studies were made about adopting the B-57, a US designed weapon used by the US Navy for fixed-wing strike and as an NDB. The weapon
could be fitted with a British warhead in the UK without conflicting with non-proliferation committments. The study eventually rejected this option,
one difficulty being that the B-57 weapon detonated at depth using a timing device triggered at splashdown,(62) whereas
the Royal Navy specified the safer option of detonation by depth-sensing hydrostatic pistols. Other objections concerned conflicting HE safety
standards; The US B-57 used the W-44 Tseste warhead that could be produced in the UK as Tony, but the anglicised Tony used a safer UK HE
composition that resulted in a lower yield. Towards the end of Tony's three-year service lifespan, tritium decay coupled with the reduced
explosive power of the British HE composition reduced the nuclear yield of Tony from a nominal 8½ kt ±¾ kt by 5.5 annually (63) to
6½ kt; believed insufficient to guarantee ignition of the fusion secondary of the larger warheads required for OR.1177;(64) and
the fission warhead was intended to be a common design suitable for multiple applications. A further objection was in the safety arrangements
in the B-57 for the tritium gas-boosting systems that failed to comply with British safety of explosives standards.(65) The
gas system to contain radioactive tritium incorporated a fusible blow-out plug similar to those found in some gasoline engine blocks. UK
practice was different, with an explosive squib isolating the tritium containment. The study concluded that major changes were required to an
anglicised B-57 to comply with British practice for storage aboard ship.(66) The
B-57 proposal was not adopted, and the studies recommended a new design of British warhead in a newly-designed British casing.(67)
Politicians then intervened. In July 1962, for reasons not entirely clear (and the Cabinet papers are still classified) the government decided on
an upper limit of yield for all British tactical nuclear weapons of all types and uses.(68) The
limit was set at 10 kt, significantly lower than the yields required by OR.1177 for the RAF, but high enough to include the naval GDA.10
requirement (and the US B-57). The RAF requirements for yields of 50, 100, 200 and 300 kilotons were dead in the water.
In adapting and redrafting OR.1177 to fit the changed circumstances, the naval requirement of GDA.10 was also modified. The requirement for
a naval SAM nuclear warhead had lapsed, and the Admiralty deleted their requirement for a 2 kt yield,(69) leaving
only the ½ kt and 10 kt requirement. The GDA.10 designation was also changed at this time to GDA.15. By this time the full range of
carriage and release options seen in the OR.1177 section above had been added to the joint RAF-RN requirement and an additional
requirement for the strategic weapon WE.177B had been issued as OR.1195.
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TSR2 & Buccaneer
The aircraft that the Improved Kiloton Bomb was intended for were the forthcoming TSR2 and Buccaneer, the principal tactical strike aircraft of
the RAF and Royal Navy respectively, and their successors. Although there were other aircraft that were expected to carry WE.177, these were
of secondary importance to plans for TSR2 and Buccaneer.
The Operational Requirements for these two strike aircraft originally specified the then current tactical nuclear bomb, Red Beard, as their
nuclear ordnance, because the Improved Kiloton Bomb was not then contemplated. Consequently, the bomb bays of these two aircraft were
sized to carry Red Beard. The Buccaneer S1 was never cleared (70) or
deployed with WE.177; it carried only Red Beard. It soon became apparent that Red Beard was unsuited for carriage and release at the high
speeds these aircraft were designed for, and Red Beard was deleted from the TSR2 design. However, without a major redesign, the TSR2
bomb bay remained optimised for a Red Beard sized weapon, in part because early RAF planning for an improved weapon specified a
weapon not larger in diameter than Red Beard, and early planning was on the basis that it would likely be of 28 inches, then 18 inches, then
finally 16½ inches diameter. Without a major and costly redesign of TSR2 when its costs were already spiraling out of control for other reasons,
the bomb bay remained unchanged in size. Oversized for a single WE.177 of high yield; and after the intervention of politicians limiting yield to
10 kt, undersized for twin lower-yield WE.177 bombs carried abreast. Buccaneer did not suffer from that problem because its fuselage and
bomb bay were wider and easily accommodated twin WE.177 weapons abreast
After the intervention of politicians referred to above, limiting for political reasons the yield of all British tactical nuclear weapons 10 kt, RAF
requirements for yields of 50, 100, 200 and 300 kilotons were dead in the water; and while retaining those design features that would make
addition of higher yields possible at a later date without major design changes, weapon designer's and RAF tactician's thoughts turned to how
they could use a 10 kt weapon to attack the hard targets assigned to the RAF by SHAPE.
One solution studied extensively was for multiple carriage of up to four weapons internally and externally on TSR2(71) and
two internally aboard the Buccaneer,(72) and
at a late stage in its design process TSR2 designers and weapon designers struggled to accommodate two weapons abreast or in tandem in
the TSR2 bomb bay designed for a single larger weapon. Multiple carriage was required to enable aircraft to release two or four weapons
against a single target in a 'stick-bombing' technique,(73) spaced
at 1'000 yards, or simultaneous release, where up to four weapons were released together, with detonation of all weapons triggered
simultaneously by one weapon to prevent nuclear fratricide of the others. The tactical studies and modifications required for both the weapon
and TSR2 were still ongoing up to the time of TSR2 cancellation.
With the large reduction in weapon diameter from Red Beard's 28 inches to ultimately 16½ inches offered by designers, the Navy also added
a requirement for twin abreast carriage in Buccaneer, that aircraft designers had no difficulty in accommodating, permitting Buccaneers to be
assigned more than one target per sortie.
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Other aircraft
As with other complex weapons developed over an extended period of time, the aircraft expected to carry this weapon were themselves subject
to cancellation and other changes in plans. The many changes are too lengthy to catalogue here. The principal intended users were the TSR2
and naval Buccaneer, and Tornado aircraft were the eventual successors to the ill-fated TSR2. The table shows the aircraft specified in RAF
Plan 'R' circa 1970; with the naval fixed-wing and rotary-wing types added.
One aircraft appearing in Plan 'R' was not equipped with WE.177. Nimrod maritime patrol aircraft of the RAF continued to be deployed with
US-owned B-57 NDBs supplied from US Navy NATO stock located in the UK and Sicily,(74) while
the WE.177 weapon stocks assigned to Nimrod units in Plan 'R' were allocated elswhere. Valiant bombers were retired prematurely after
fatigue issues emerged. Victor B2 bombers remained as Blue Steel units until re-assigned to a tanker role. Vulcan and Victor B1A aircraft and
Canberras were retired before WE.177 stocks became available, and RAF Harrier units were not assigned a nuclear role. Sea Vixen aircraft
were cleared for use of WE.177 as an insurance against delay in the Buccaneer development programme, and although assigned a secondary
role as a strike aircraft, were not specifically allocated WE.177 stocks, although in an emergency, if no Buccaneers were available, they were
capable of delivering the stocks kept aboard carriers for the embarked Buccaneers.
The Ikara anti-submarine missile was purchased from Australia for deployment aboard the CVA-01 carrier and its escorts based on the
Type 82 destroyer HMS Bristol. After cancellation of the carrier and escorts, Ikara stocks were used to equip some Leander class frigates, and
plans to equip Ikara with the WE.177 shortened by the removal of the tail bodycap and radar nose were abandoned. The Scimitar naval strike
aircraft and Canberras were photographed carrying and releasing WE.177 test rounds, but were used only for those test purposes and never
deployed operationally with the weapon; the Canberra being retired before stocks of WE.177A tactical weapons became available to the RAF
in 1971
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OR.1156 & OR.1178
OR.1156 pre-dated the Air Staff Operational Requirement for an Improved Kiloton Bomb, OR.1177, (75) the first draft being produced in January
1958 (76) at
the instigation of the Commander-in-Chief of RAF Coastal Command. (77) Prior
to that, an Air Ministry Working Party set up to recommend future policy on airborne anti-submarine detection and weapons had concluded early
in 1957 (78) that
only a nuclear depth bomb could provide certainty of killing the new generations of fast, silent nuclear-powered submarines being developed in
the Soviet Union. The Working Party recommended that a nuclear depth bomb be developed for all versions of Shackleton aircraft, at that time
RAF Coastal Command's front-line long-range maritime patrol bomber. OR.1156 was to be met initially by an adaptation of the Red
Beard warhead, (79) and
later proposals were considered using the Una warhead, (80) later
renamed Ulysses. (81)
Shackleton maritime patrol bomber maildrop to HMS Minerva on the Beira Patrol. Photo:HMS Minerva website.
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Although there is no hard evidence, and what follows here is speculation, it is entirely possible that the Ursula warhead was
intended for the OR.1156 nuclear depth bomb project. Although little is known of Ursula, it is known to be shorter and be of greater
diameter than its contemporary, Ulysses. (82) Neither
of these characteristics would be detrimental to the OR.1156 anti-submarine weapon, given the capacious bomb bay of the Shackleton or its
successors, and Ursula would meet the dimensions specified in the first draft of OR.1156. (83) Una
was known to be a thermonuclear design based on Red Snow, the anglicised US W-28, using the Tony fission trigger, an anglicised US W-44. (84) Given
Ursula's design ancestry in Una, and its design, dimensional and weight similarities to Una it is entirely possible that Ursula was the warhead
of choice for OR.1156 at one point in time.
The first draft of OR.1156 specified a yield of 30-50 kt,(85) and
it is now known that the Red Beard warhead never achieved those figures; and there were numerous handling, storage and temperature
limitation environmental issues with the weapon.(86) Similar
issues as those that resulted in OR.1177 for an Improved Kiloton Bomb. As an interim measure, yield requirements for OR.1156 were lowered
to 5-10 kt in the period to 1965,(87) and
15 kt in the five year period to 1970.(88) The
Red Beard warhead could have met those requirements, but with no possibility of an increase to meet the full requirement of 30-50 kt, and no
doubt explains the search for an alternative warhead in Una or Ursula.
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Ultimately, given the pressures on resources, the Coastal Command requirement became a joint Naval Staff/Air Staff requirement and
renumbered OR.1178 before being subsumed into OR.1177 and deployed in 1969 as WE.177A.(89)
The Royal Navy deployed WE.177A in its intended role as a fixed-wing strike weapon and as a helicopter-borne anti-submarine weapon.
However, neither RAF Coastal Command long-range maritime patrol Shackletons or its successor, the Nimrod, ever deployed this weapon. There
were plans to do so, but never implemented, the 79 WE.177A weapons planned for their use being allocated elsewhere.(90) From
1961(91) Shackletons
were supplied with a stock of 36 US Navy Project 'N' weapons maintained for their use at RAF St Mawgan, Cornwall,(92) and
Sigonella US NAS, Sicily.(93) Shackletons
carried the Mk-101 Lulu NDB, and were able to carry two plus other weapons.(94) Nimrods
could carry two B-57 NDBs, but were allocated only one per aircraft.(95) Use
of the American weapons was restricted to the NATO area and temporary deployments of Coastal Command Shackletons and Nimrods to the
Middle and Far East were without nuclear weapons.(96) A
primary reason for wanting a UK-owned NDB for these aircraft was to free them from that and other restrictions on their operational flexibility.
Nimrods based in Cyprus on NATO duties had to first fly the 894 nm to Sicily to collect their weapons from American custody.(97)
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WE.177 design antecedents
In the early 1990's some writers asserted that the WE.177A design was based on the US B57
bomb, (98) which was of a similar size,
weight, yield and purpose, and that speculation has been widely repeated elsewhere. The B57 also functioned as a NDB, and it used the
W-44 Tsetse/Tony boosted fission warhead rejected by the British for their RE.179 primary. It is also true that the British had access to its
design and planned to manufacture it in the UK for various purposes. However, since the early 1990's, many secret files have been declassified,
and these make it clear that the claims about a common design were merely speculation and wrong. The original Naval Staff Requirement,
GDA.10 incorporated into OR.1177 makes clear from the outset in 1960, that the Navy required a bomb with three yields of ½kt, 2kt and
10kt, that was lighter and smaller than the RAF requirement, and at a max weight of 550 lbs very similar to the US B57; and the B57 was
indeed studied closely.
Declassified records released in 2008 (99) shows
that the B57 was rejected as unsuitable. The UK Ordnance Board (the safety authority) was unimpressed with the shock-sensitivity of the
PBX-9404 used in the B57's W-44 warhead. The Ordnance Board , RAE Farnborough and the Navy required considerable redesign of
several arming systems to comply with British safe practice, in particular the methods used to control radioactive tritium, and make
inadvertent operation of the tritium valve impossible, from fire or other causes, eg. electromagnetic radiation. (100) The
RAF and Navy also required a hydrostatic system of detonation at a predetermined water depth. The B57 design relied upon a timer to
detonate that was unable to determine depth, or if the weapon had grounded on a shallow sea floor. The B57 also required modification to
permit all the delivery and flight profiles required by the Navy. Redesign was expected to be costly and time consuming as compared to
developing a new weapon using the studies already done on OR.1177, while a warhead capsule to OR.1176 was already well advanced.
Some writers made the assertion (98) that
because the British conducted so few full-scale nuclear tests, WE.177 was unlikely to be an indigenous design. That it must, by a curious
extension of that opinion, be an American design, the closest being the B57, while failing to understand that the WE.177 fission element was
one of a 'family' of designs, deliberately similar, intended to produce a 'common design', usable with only minor changes, in a variety of
applications from Skybolt, Polaris, Blue Water and WE.177. As it indeed was, and so a single series of only four full-scale underground
nuclear tests were necessary, plus one failed test. (101)
There were four other [nuclear] 'effects' tests conducted in the US, and numerous non-nuclear 'scaled' tests in the UK. Hardly a small testing
programme for a single fission device. In fairness to those writers, it may not have been so apparent then as now, after numerous
declassifications of archived documents; and finally in reference to the assertion of so few nuclear tests being conducted by the British, one only
has to contemplate the words: "the Israeli bomb"; of which there were apparently no tests at all.
Such speculation also fails to take into account the cultural and financial differences between the US and British nuclear programmes. The
early US programme was over-reliant on full-scale testing because of the extreme urgency attached to its very large programme. There are
instances of poor design directly attributable to a poorer theoretical understanding of the physics, and an empirical design
approach. (102)
The fission primary of the W-28 being one example of design flaws attributable to an imperfect theoretical
understanding. (103)
On the other hand, the British, with fewer resources, and always short of cash, employed their meagre resources to better effect, with a
better understanding of the theory that underpinned their efforts. They also benefitted from the shared US test data, as the US benefitted
from equally valuable British know-how. That shared know-how, coupled with British experience and greater theoretical understanding was
one factor that contributed to an American desire to complete the 1958 Bilateral, or Mutual Defence Agreement. The US understood that
they had much to gain from the British, as the British also gained. It was a shared experience, not a one-way street.
Construction
WE.176 and the WE.177A weapon it was originally intended for, differed in one principal respect from the earlier weapon it replaced. Red
Beard like similar early British and US weapons had a first generation spherical implosion device that used a removable fissile core that
could be stored separately from the high-explosive components, with the fissile core inserted into the weapon at the last possible moment,
either in-flight by mechanical loading devices (IFL) or on the ground immediately before take-off (LML). These arrangements were thought
to enhance the safety of what were very complicated, yet primitive devices, that mishandled would have devastating consequences. Storing
the fissile core separately from the HE, detonators and an electrical power supply was merely an extension of the age-old good practice of
storing fuzes or detonators well away from the main explosive charge. But primitive as the first generation nuclear weapons were, they were
still very complex devices, and Service personnel had little practical experience of performing delicate servicing and assembly operations
on equipment so complicated and so demanding of precision. The successor to Red Beard was expected to minimise these operational
difficulties, and also produce a similar nuclear yield from a smaller and lighter package. The methods needed to achieve this end, required
greater precision in manufacture, all the neccessary equipment permanently installed in a self-contained package to be serviced only by the
manufacturer's specialist workers, and less involvement by Service personnel. Additionally, the Improved Kiloton Bomb had to meet the new
tougher requirements of transonic and supersonic flight, and new methods of delivery, including laydown, which could be described as a
controlled crash-landing, where the deceleration from supersonic speeds whilst still airborne could be as stressful as ground contact.
The WE.176 replacement warhead was engineered rather differently. The first draft of the specification OR.1177 called for the weapon to be
supplied, stored and transported in several main sections (nose with radar elements, centrebody, tail, and warhead capsule). It had been
hoped that the warhead capsule itself could be transferred between different weapons as and when operations required. For example: it was
envisaged that a warhead capsule might be transferred between a bomb and another delivery vehicle, eg. an air-defence missile, an
anti-submarine missile, or a submarine torpedo. This arrangement was quickly seen to be impractical if other operational requirements
were to be met, and a self-contained warhead enclosed in a shock-resistant capsule was installed in the fully assembled bomb casing at
manufacture, and was issued to the Service in that state, installed in a non-air-conditioned storage container. It required no servicing or
assembly operations by the Service user other than periodic checks for gas leakage and routine checks of the electrical systems.
After a decision to reject the use of the US W-44 Tsetse primary originally proposed because of concerns about the shock-sensitivity of the
PBX-9404 HE used, a UK-designed primary was substituted. This was based on a design originating with a UK device named Super Octopus,
that was later developed into the Cleo design. An enlarged Cleo was adopted for use in the primary for the warhead for Skybolt, the
thermonuclear bomb to OR.1177 (then to be much larger than WE.177A), and a primary for the Blue Water SSM for the Army. Skybolt had the
greater priority at this time, and the PAMPAS UGT detonated 01 March 1962 has been attributed to the Skybolt warhead development program,
although its use was always envisaged for these other weapons. The Royal Navy GDA.10 requirement for a small bomb that led to WE.177A
was not yet not approved.
PRO declassified files provide hard evidence that the Cleo device tested at Pampas UGT was not one-point-safe. It used a mechanical safety
device consisting of a core filling of two litres of five micron diameter glass balls that were to be ejected during the arming sequence, before
the void was evacuated to a vacuum. Prior to detonation the void was filled with pressurised tritium. There were concerns about the
consequences of ejecting these glass balls into the aircraft mechanisms, and concerns about the mechanical reliability of the ejection
mechanisms. Similar arrangements in earlier weapons had led to a weapon being in an unsafe condition in storage when the core filling
escaped from the warhead onto the storage area floor. See here at
Footnote 41 & 42.
The TENDRAC UGT on 07 December 1962 was of an enlarged modified device, and a declassified PRO file refers to this device having a
smaller fissile core than PAMPAS, and being inherently one-point-safe. It also dispensed with the mechanical safety device, eliminating the
doubts about the glass ball core filling, and easing the provision of a gastight fissile core. The evacuation to vacuum could then be done in the
factory at assembly. The plutonium hemispheres manufactured at Aldermaston were probably closed by welding, (although there is no direct
hard evidence for this) and seated on polymeric (plastic) cushions inside a gastight beryllium tamper, welded closed. There is evidence in
declassified files of the manufacture at ROF Cardiff of U-235 hemispheres, which suggests that the fissile core may have been a composite
one composed of two different fissile materials. The reason for this choice may have been to reduce the scarce and expensive plutonium
quantity to an absolute minimum, substituting the less costly U-235. A beneficial effect for the designers was that reducing plutonium quantity
assisted in achieving one-point-safety. The Chinese demonstrated in an atmospheric test of a boosted fission device with a composite core on
18 Nov 1971 that a core with as little as 2kg of plutonium and a small amount of HEU would increase the nuclear yield of the less efficient HEU
by blanketing the HEU with the more energetic neutrons produced by the fission of plutonium.
Although further changes were made, and further UGTs were done to optimise the device as a primary for Polaris after the cancellation of
Skybolt and the Army's Blue Water SSM, the enlarged-Cleo device tested at TENDRAC was used as the primary for WE.177B, and
alone as the fission warhead PT.176 for WE.177A, remaining essentially as it was when tested at TENDRAC. Some changes may have been
incorporated after the CORMORANT UGT two years later, and the so-called Economy Tests COURSER (a failure) and CHARCOAL. These
later tests were not originally mounted for warhead development, but were a programme of advanced reseach unconnected with Skybolt,
WE.177 and Polaris, although some use of them was made to optimise the Polaris warhead, especially in economising on fissile material,
they may have been too late to influence major changes on the eve of WE.177B deployment. The principal changes from the Skybolt proposal
was a reduction in fissile material used in the W-59 Skybolt thermonuclear secondary to acheive a yield of approximately ½MT for WE.177B
(or as much as possible given the restraints on casing size), and this change, and a similar later change for Polaris, did not directly
impact on the design of the Pampas-Tendrac enlarged-Cleo design of a primary device, which could remain essentially unchanged. Although
weight reduction was possibly a prime concern for the Polaris version. There is no hard evidence either way.
The life-limiting factor was the radioactive tritium gas used in the warhead, which decays at a known rate, and was specified to be replaced
at three-year intervals initially. All other components were designed to match that expected three-year life, and the entire weapon was
returned to the manufacturer at that interval, when all routine servicing was done. This practice has been the norm for all subsequent
nuclear warheads.
The armoured, shock-resistant warhead capsule contained an independent power supply and all the equipment needed for the warhead to
function to detonation after a hard landing on the ground or in water in what is termed a 'laydown' delivery. The warhead capsule was
protected by the shock-absorbing qualities of the nose and tail, and the after part of the centre section. The equipment housed in these
sections was no longer required after laydown. The tail was said to 'slap-down' on landing, and in doing so absorbs some of the landing
shocks, protecting the armoured warhead capsule, itself secured inside a forged high-strength aluminium alloy centre section casing.
The warhead capsule was gas pressurised and watertight to 2'000 ft water depth. The rear centre section casing, the tail section and the
nose section flooded after landing in water, with the parachutes being detached by an explosive cutter to ensure a rapid sink rate when used
as a NDB. The radar-transparent ceramic nosecone was not needed for the laydown delivery onto land or water and was jettisoned by a
small explosive charge immediately after aircraft release. The resulting flat nose shape helped the weapon to enter the water cleanly
without porpoising, and performed a similar function on flat ground, where a lengthy slide was not desirable.
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WE.177A
WE.177A weighed 282 kg (620 lb), with a selectable yield of 10 kT and 0.5 kT. This was a boosted fission weapon. The 0.5 kT
yield was used only in the NDB role for detonation below 140 ft (43 m) in shallow coastal waters or in oceanic deep waters below 350 ft
(107 m) to limit damage to nearby shipping. The full 10 kT yield was used only below 350 ft (107 m) in deep oceanic waters where no
shipping was at risk (104) and
the low yield was selected automatically where the water depth did not exceed 350 ft.
The full 10 kT yield was used by fixed wing aircraft for surface attack. It had airburst, ground burst or laydown options. Although this variant
most closely matched the original GDA.10 naval requirement and was identified as the 'A' model, it was not the first to be deployed.
Development was purposely delayed when the Skybolt ALBM was cancelled. Revised priority was then given to a bomb intended to extend
the life (in a strategic role) of the Vulcan bomber force. This stopgap weapon was WE.177B, also known as Weapon X, a thermonuclear parachute-retarded free-fall
bomb based on a lengthened WE.177A casing, using as a thermonuclear primary the intended warhead for WE.177A. This primary was
known as KATIE in WE.177B. and as KATIE A in WE.177A.
Twenty WE.177A bombs were transferred to the RAF from the Royal Navy when the large carriers were decommissioned, and the remaining
43 weapons that were assigned to the Navy's helicopters were retired in 1992. These were also capable of use by Sea Harriers. It was known to the
Armed Services as 'Bomb, Aircraft, HE 600 lb MC'. In this service jargon MC (Medium Capacity) referred to a nuclear weapon in the kiloton
range. The suffix HC (High Capacity) referred to a weapon in the megaton range, although there were some anomalies. The twenty weapons
transferred to the RAF were in fact still deployed on Buccanneer aircraft tasked for the maritime strike role, and assigned to SACLANT, as
they were when carrier-borne.
WE.177A anti-submarine weapons were deployed afloat by the Royal Navy for use by embarked helicopters. They were never deployed by
the RAF aboard their maritime anti-submarine aircraft. RAF Nimrods based in the UK were equipped with US B-57 weapons drawn from
NATO stocks maintained in the UK at RAF St Mawgan for RAF and Dutch Navy maritime aircraft. (105)
Nimrod aircraft based in the Mediterranean and assigned to SACEUR were also equipped with US B-57 weapons maintained in a US Navy
stockpile at Sigonella in Sicily. Although it was intended to issue 72 WE.177A weapons plus 7 reserves, totalling
79 (106) to all Nimrod squadrons
and the 'shadow squadron' (an operational training unit in its peacetime role) (107) there
were never enough WE.177A weapons in British stockpiles to permit implementation of those plans. Nimrods were configured to carry two
WE.177A weapons, although the B-57 weapons assigned from US stockpiles totalled only 36, sufficient for only one per aircraft. UK-based
Nimrods were assigned to SACLANT for use in the Atlantic area, and Cyprus and Malta-based aircraft were assigned to SACEUR and in
support of CENTO for use in the Mediterranean. Use of the American B-57 NDB was limited to the Atlantic and Mediterranean areas. Nimrod
squadrons were ocasionally rotated to Singapore without nuclear weapons, a limitation on operational flexibility that WE.177A NDBs would not
have suffered.
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WE.177B
WE.177B weighed 457 kg (1'007.5 lb), with a single yield of 450 kT. Although it weighed in excess of 1'000 lb it was known to the
Armed Services as Bomb, Aircraft, HE 950 lb MC No.1.
WE.177B had a thermonuclear warhead, comprising two parts. The primary was KATIE referred to above, but without the variable yield facility
or the NDB's hydrostatic fuse. KATIE was based on a British design known as CLEO, earlier known as Super Octopus, intended as the
thermonuclear primary for RE.179, a British warhead for the RAF version of the cancelled Skybolt air-launched ballistic missile. The secondary
(or fusion element) of RE.179 was based on the US W-59 warhead and was known by the British codename of SIMON. However, the W-59
primary used PBX-9404, a plastic-bonded-explosive, considered by the British to be unsafe. The US W-44 primary was replaced with a
British primary developed from CLEO, that evolved into KATIE, that did not use the shock-sensitive PBX-9404. When Skybolt was cancelled the
fusion secondary of RE.179 was adapted with KATIE to become WE.177B (also referred to as Weapon X) and in a smaller version, the British
ET.317 warhead for the Royal Navy's Polaris A3T.
|
 WE.177B and carrier, awaiting
aircraft loading at RAF Marham. Photo: Leitch.
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WE.177B had airburst, impact, ground laydown and water laydown options. Roughly, 'laydown' can be taken to mean a ground burst or a sea
surface burst with a time delay after a relatively soft parachute retarded landing, enabling the bomber to escape the detonation. The nose and
tail sections absorbed much of the energy, with the equipment in those sections being redundant after touch-down. The warhead in the toughened
centre section survived the crash-landing unscathed. Priority was given to the laydown option for the Vulcan bombers, and the first nine examples
deployed had no other option than laydown delivery. These nine weapons were recalled for early refurbishment when radar and other delayed
equipment was retrofitted. The WE.177B programme was completed by September 1967.
Numbers built are still uncertain but reliable sources put the figure at 53. (108)
Skybolt warheads ordered numbered 90 (109) and
at cancellation this was the RAF requirement for WE.177B, although this quantity was reduced later. When Polaris became operational with the Royal Navy, the RAF bomber force continued in a tactical role with
these and other bombs. With the conversion of the Victor bombers to fuel-tankers and retirement of the Vulcan bombers, WE.177B was carried
by successor aircraft, including RAF Tornados. All WE.177B were retired by August 1998.
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![TNA DEFE 24/691 E28 sect 4. Polaris, Poseidon and the Holy Loch 1970-1971."There is also an understanding in respect of US nuclear weapons, destined for release in times of emergency to maritime aircraft of the Netherlands [and the RAF] and stored in St Mawgan, Cornwall, which was set out in an exchange of letters between Prime Minister Wilson and President Johnson in 1965…. " ^ up](http://nuclear-weapons.info/images/tna-defe24-691e28_06.JPG){kind=link}
![TNA ADM 1/30991 E3A p2. An improved kiloton bomb. 1959-1961. [For the Royal Navy].](http://nuclear-weapons.info/images/tna-adm1-30991e03a_002.JPG){kind=link}
![TNA ADM 1/30991 E6 p1. An improved kiloton bomb. 1959-1961. [For the Royal Navy].](http://nuclear-weapons.info/images/tna-adm1-30991e06_001.JPG){kind=link}
