AGM-48 Skybolt
Encyclopedia
The Douglas
GAM-87 Skybolt (AGM-48 under the 1962 Tri-service system) was an air-launched ballistic missile
(ALBM), equipped with a nuclear warhead, developed by the United States
during the late 1950s. The UK joined the program in 1960, intending to use it on their V bomber
force. A series of test failures and the development of submarine launched ballistic missiles (SLBMs) eventually led to its cancellation in the mid-1960s. The UK had decided to base its entire 1960s deterrent force on Skybolt, and its cancellation led to a major confrontation between the UK and US, known today as the "Skybolt Crisis". This was solved during a series of meetings
that led to the Royal Navy
gaining the UGM-27 Polaris
missile and construction of the Resolution class submarine
s to launch them.
s in the 1950s rendered flight over enemy territory much more dangerous. Yet the Air Force and military planners were, in the mid-1950s, reluctant to simply hand over the nuclear strike capability to missiles, which after launch were no longer under positive control, could not be recalled or redirected, and would reach their targets within a matter of minutes after the order to fire. The missiles of the day were all required to be loaded with their fuels prior to launch (they all used nonstorable propellants); and they could only be launched from above ground (after long pre-launch checkouts) launch pads, making them vulnerable to attack - the first ICBMs, Atlas 1 and Titan 1 were of this type.
In addition, the inaccuracy of missiles in the 1950s made them useless as precision strike weapons. They could attack area targets like cities, but could not reliably and accurately attack precision strike targets like enemy bomber bases, hardened command and control centers, naval bases, or weapons storage areas. Initially, western ballistic missiles could not even reach such targets, which would be located deep within interior of the Sino-Soviet land mass in Asia. Therefore the potential integration of aircraft with the invulnerability of the ballistic missile was intriguing prospect to 1950s military planners.
Basing the strike package on aircraft offered a flexibility that missiles could not match. For instance, the bombers could stand off from the targets and wait for instructions from secure command centers to attack targets that were missed in an initial strike. Additionally, the bombers could use long-range weapons to strike known air defenses, and then overfly them to deliver precision strikes with conventional bombs.
Secondly, and most importantly, this mode of deployment meant that the strike force was rendered almost invulnerable. The bombers could fly to staging areas well outside the range of even the longest-legged defenses, and strike with impunity. This allowed for gradual escalation and a possible backing down through diplomacy. A ground-based missile cannot be used in the same fashion; it is either launched or not. If threatened with a nuclear strike, this presents their owners with the 'use them or lose them' predicament.
For the British, their dilemma was a matter of geography and financial resources. No fixed land based ballistic missile system could be credibly installed in the British Isles; they were well within the range of Soviet air strikes. The limited land mass available meant it would be relatively easy for missile sites to be spotted no matter what security measures were taken. Suitable locations for construction also carried a social and political cost. Fixed land based ballistic missile sites need many thousands of acres per squadron (typically ten missiles); and the squadrons need to be apportioned over many thousands of square miles, so that no single attack could conceivably destroy them all in one strike.
systems for mid-flight corrections of an inertial guidance platform, similar to that of the US Navy's SLBM systems, led to an accuracy similar to that of their existing ground-based missiles.
The US Air Force was interested and began accepting bids for development systems in early 1959. Douglas Aircraft received the prime contract in May, and in turn subcontracted to Northrop
for the guidance system, Aerojet
for the propulsion system, and General Electric
for the reentry vehicle. The system was initially known as WS-138A and was given the official name GAM-87 Skybolt in 1960.
At the same time the Royal Air Force
was having problems with their IRBM missile project, the Blue Streak
, which was long overdue. At the same time, they faced the same problems with the dwindling survivability of their existing nuclear deterrent, the V-bomber fleet. The long-range Skybolt would eliminate the need for both the Blue Streak and the Blue Steel II
standoff missile, then under development. The Blue Steel II was cancelled in December 1959 and the British cabinet had decided in February 1960 to cancel the Blue Streak.
Prime Minister
Macmillan
met President
Eisenhower in March 1960 and agreed to purchase 144 Skybolts for the RAF. By agreement, British funding for research and development was limited to that required to modify the V-bombers to take the missile, but the British were allowed to fit their own warheads and the Americans were given nuclear submarine basing facilities in Scotland. Following the agreement the Blue Streak programme was formally cancelled in April 1960 and in May 1960 an agreement for an initial order of 100 Skybolts was concluded.
Avro
were made an associate contractor to manage the Skybolt programme for the United Kingdom and four different schemes were submitted to find a platform for the missile. A number of different aircraft platforms were considered including a variant of the Vickers VC10
airliner and two of the current V-bombers, the Avro Vulcan
and Handley Page Victor
. It was decided to use the Vulcan to initally carry two missiles each on hardpoints outboard of the main landing gear.
. Powered tests started in April 1962, but the test series went badly, with the first five trials ending in failure of one sort or another. The first fully successful flight occurred on December 19, 1962.
was particularly opposed to the bomber force and repeatedly stated he felt that the combination of SLBMs and ICBMs would render them useless. He pressed for the cancellation of Skybolt as an unnecessary program.
The British, on the other hand, had cancelled all other projects to concentrate fully on Skybolt. When McNamara informed them that they were considering cancelling the program in November 1962, a firestorm of protest broke out in the House of Commons. Jo Grimond noted "Does not this mark the absolute failure of the policy of the independent deterrent? Is it not the case that everybody else in the world knew this, except the Conservative Party in this country?" As the political row grew into a major crisis, an emergency meeting between parties from the US and UK was called, leading to the Nassau agreement
.
Over the next few days a new plan was hammered out
that saw the UK purchase the Polaris SLBM, but equipped with British warheads that lacked the dual-key
system. The UK would thus retain its independent deterrent force, although its control passed from the RAF largely to the Royal Navy
. The Polaris, a much better weapon system for the UK, was a major "scoop" and has been referred to as “almost the bargain of the century” The RAF kept a tactical nuclear capability with the WE.177
which armed V-bombers and later the Panavia Tornado
force. The "Skybolt Crisis" was a major event in the eventual downfall of the Macmillan administration.
Limited flight tests with the remaining XGAM-87A missiles continued after program cancellation. In June 1963, the XGAM-87A was redesignated as XAGM-48A.
carried one each on smaller pylons. The missile was fitted with a tailcone to reduce drag while on the pylon, which was ejected shortly after being dropped from the plane. After first stage burnout, the Skybolt coasted for a while before the second stage ignited. First stage control was by eight movable tail fins, while the second stage was equipped with a gimballed nozzle.
Guidance was entirely by inertial platform. The current position was constantly updated from the host aircraft though accurate fixes, meaning that the accuracy of the platform inside the missile was not as critical.
Douglas Aircraft Company
The Douglas Aircraft Company was an American aerospace manufacturer, based in Long Beach, California. It was founded in 1921 by Donald Wills Douglas, Sr. and later merged with McDonnell Aircraft in 1967 to form McDonnell Douglas...
GAM-87 Skybolt (AGM-48 under the 1962 Tri-service system) was an air-launched ballistic missile
Air-launched ballistic missile
An air-launched ballistic missile or ALBM is a ballistic missile launched from an aircraft. This class of missile never saw active use. The only known missile of this type that was intended for operational service, the GAM-87 Skybolt, intended to be launched from B-52 Stratofortress and Avro...
(ALBM), equipped with a nuclear warhead, developed by the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
during the late 1950s. The UK joined the program in 1960, intending to use it on their V bomber
V bomber
The term V bomber was used for the Royal Air Force aircraft during the 1950s and 1960s that comprised the United Kingdom's strategic nuclear strike force known officially as the V-force or Bomber Command Main Force...
force. A series of test failures and the development of submarine launched ballistic missiles (SLBMs) eventually led to its cancellation in the mid-1960s. The UK had decided to base its entire 1960s deterrent force on Skybolt, and its cancellation led to a major confrontation between the UK and US, known today as the "Skybolt Crisis". This was solved during a series of meetings
Nassau agreement
The Nassau Agreement, concluded on 22 December 1962, was a treaty negotiated between President John F. Kennedy for the United States and Prime Minister Harold Macmillan for the United Kingdom...
that led to the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
gaining the UGM-27 Polaris
UGM-27 Polaris
The Polaris missile was a two-stage solid-fuel nuclear-armed submarine-launched ballistic missile built during the Cold War by Lockheed Corporation of California for the United States Navy....
missile and construction of the Resolution class submarine
Resolution class submarine
The Resolution-class submarine armed with the Polaris missile was the United Kingdom's primary nuclear deterrent from the late 1960s to 1994, when they were replaced by the Vanguard-class submarine carrying the Trident II.-Background:...
s to launch them.
Background
Nuclear weapons theorists had speculated about how to integrate the flexibility and positive control (over the attack) of the manned bomber with the invulnerability (in the attack) of the ballistic missile. The introduction of useful surface-to-air missileSurface-to-air missile
A surface-to-air missile or ground-to-air missile is a missile designed to be launched from the ground to destroy aircraft or other missiles...
s in the 1950s rendered flight over enemy territory much more dangerous. Yet the Air Force and military planners were, in the mid-1950s, reluctant to simply hand over the nuclear strike capability to missiles, which after launch were no longer under positive control, could not be recalled or redirected, and would reach their targets within a matter of minutes after the order to fire. The missiles of the day were all required to be loaded with their fuels prior to launch (they all used nonstorable propellants); and they could only be launched from above ground (after long pre-launch checkouts) launch pads, making them vulnerable to attack - the first ICBMs, Atlas 1 and Titan 1 were of this type.
In addition, the inaccuracy of missiles in the 1950s made them useless as precision strike weapons. They could attack area targets like cities, but could not reliably and accurately attack precision strike targets like enemy bomber bases, hardened command and control centers, naval bases, or weapons storage areas. Initially, western ballistic missiles could not even reach such targets, which would be located deep within interior of the Sino-Soviet land mass in Asia. Therefore the potential integration of aircraft with the invulnerability of the ballistic missile was intriguing prospect to 1950s military planners.
Basing the strike package on aircraft offered a flexibility that missiles could not match. For instance, the bombers could stand off from the targets and wait for instructions from secure command centers to attack targets that were missed in an initial strike. Additionally, the bombers could use long-range weapons to strike known air defenses, and then overfly them to deliver precision strikes with conventional bombs.
Secondly, and most importantly, this mode of deployment meant that the strike force was rendered almost invulnerable. The bombers could fly to staging areas well outside the range of even the longest-legged defenses, and strike with impunity. This allowed for gradual escalation and a possible backing down through diplomacy. A ground-based missile cannot be used in the same fashion; it is either launched or not. If threatened with a nuclear strike, this presents their owners with the 'use them or lose them' predicament.
For the British, their dilemma was a matter of geography and financial resources. No fixed land based ballistic missile system could be credibly installed in the British Isles; they were well within the range of Soviet air strikes. The limited land mass available meant it would be relatively easy for missile sites to be spotted no matter what security measures were taken. Suitable locations for construction also carried a social and political cost. Fixed land based ballistic missile sites need many thousands of acres per squadron (typically ten missiles); and the squadrons need to be apportioned over many thousands of square miles, so that no single attack could conceivably destroy them all in one strike.
Development
In 1958 several American contractors demonstrated that large ballistic missiles could be launched from strategic bombers at high altitude. The use of astronavigationCelestial navigation
Celestial navigation, also known as astronavigation, is a position fixing technique that has evolved over several thousand years to help sailors cross oceans without having to rely on estimated calculations, or dead reckoning, to know their position...
systems for mid-flight corrections of an inertial guidance platform, similar to that of the US Navy's SLBM systems, led to an accuracy similar to that of their existing ground-based missiles.
The US Air Force was interested and began accepting bids for development systems in early 1959. Douglas Aircraft received the prime contract in May, and in turn subcontracted to Northrop
Northrop Corporation
Northrop Corporation was a leading United States aircraft manufacturer from its formation in 1939 until its merger with Grumman to form Northrop Grumman in 1994. The company is known for its development of the flying wing design, although only a few of these have entered service.-History:Jack...
for the guidance system, Aerojet
Aerojet
Aerojet is an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California with divisions in Redmond, Washington, Orange, Gainesville and Camden, Arkansas. Aerojet is owned by GenCorp. They are the only US propulsion company that provides both solid rocket...
for the propulsion system, and General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
for the reentry vehicle. The system was initially known as WS-138A and was given the official name GAM-87 Skybolt in 1960.
At the same time the Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
was having problems with their IRBM missile project, the Blue Streak
Blue Streak missile
The Blue Streak missile was a British medium range ballistic missile . The Operational Requirement for the missile was issued in 1955 and the design was complete by 1957...
, which was long overdue. At the same time, they faced the same problems with the dwindling survivability of their existing nuclear deterrent, the V-bomber fleet. The long-range Skybolt would eliminate the need for both the Blue Streak and the Blue Steel II
Blue Steel missile
The Avro Blue Steel was a British air-launched, rocket-propelled nuclear stand-off missile, built to arm the V bomber force. It was the primary British nuclear deterrent weapon until the Royal Navy started operating Polaris missile armed nuclear submarines....
standoff missile, then under development. The Blue Steel II was cancelled in December 1959 and the British cabinet had decided in February 1960 to cancel the Blue Streak.
Prime Minister
Prime Minister of the United Kingdom
The Prime Minister of the United Kingdom of Great Britain and Northern Ireland is the Head of Her Majesty's Government in the United Kingdom. The Prime Minister and Cabinet are collectively accountable for their policies and actions to the Sovereign, to Parliament, to their political party and...
Macmillan
Harold Macmillan
Maurice Harold Macmillan, 1st Earl of Stockton, OM, PC was Conservative Prime Minister of the United Kingdom from 10 January 1957 to 18 October 1963....
met President
President of the United States
The President of the United States of America is the head of state and head of government of the United States. The president leads the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces....
Eisenhower in March 1960 and agreed to purchase 144 Skybolts for the RAF. By agreement, British funding for research and development was limited to that required to modify the V-bombers to take the missile, but the British were allowed to fit their own warheads and the Americans were given nuclear submarine basing facilities in Scotland. Following the agreement the Blue Streak programme was formally cancelled in April 1960 and in May 1960 an agreement for an initial order of 100 Skybolts was concluded.
Avro
Avro
Avro was a British aircraft manufacturer, with numerous landmark designs such as the Avro 504 trainer in the First World War, the Avro Lancaster, one of the pre-eminent bombers of the Second World War, and the delta wing Avro Vulcan, a stalwart of the Cold War.-Early history:One of the world's...
were made an associate contractor to manage the Skybolt programme for the United Kingdom and four different schemes were submitted to find a platform for the missile. A number of different aircraft platforms were considered including a variant of the Vickers VC10
Vickers VC10
The Vickers VC10 is a long-range British airliner designed and built by Vickers-Armstrongs Ltd, and first flown in 1962. The airliner was designed to operate on long-distance routes with a high subsonic speed and also be capable of hot and high operations from African airports...
airliner and two of the current V-bombers, the Avro Vulcan
Avro Vulcan
The Avro Vulcan, sometimes referred to as the Hawker Siddeley Vulcan, was a jet-powered delta wing strategic bomber, operated by the Royal Air Force from 1956 until 1984. Aircraft manufacturer A V Roe & Co designed the Vulcan in response to Specification B.35/46. Of the three V bombers produced,...
and Handley Page Victor
Handley Page Victor
The Handley Page Victor was a British jet bomber aircraft produced by the Handley Page Aircraft Company during the Cold War. It was the third and final of the V-bombers that provided Britain's nuclear deterrent. The other two V-bombers were the Avro Vulcan and the Vickers Valiant. Some aircraft...
. It was decided to use the Vulcan to initally carry two missiles each on hardpoints outboard of the main landing gear.
Tests
By 1961, several test articles were ready for testing from USAF B-52 bombers, with drop-tests starting in January. In January 1961 a Royal Air Force Vulcan visited the Douglas plant at Santa Monica to make sure the modifications to the aircraft were electrically compatable with the missile. In Britain compatibility trials with mockups started on the VulcanAvro Vulcan
The Avro Vulcan, sometimes referred to as the Hawker Siddeley Vulcan, was a jet-powered delta wing strategic bomber, operated by the Royal Air Force from 1956 until 1984. Aircraft manufacturer A V Roe & Co designed the Vulcan in response to Specification B.35/46. Of the three V bombers produced,...
. Powered tests started in April 1962, but the test series went badly, with the first five trials ending in failure of one sort or another. The first fully successful flight occurred on December 19, 1962.
Cancellation
By this point the value of the Skybolt system had been seriously eroded. The US Navy's Polaris submarine-launched ballistic missile had recently gone into service, with overall capabilities similar to Skybolt, but with "loiter times" on the order of months instead of hours. Additionally, the US Air Force itself was well into the process of developing the Minuteman missile, whose improved accuracy reduced the need for any bomber attacks. Robert McNamaraRobert McNamara
Robert Strange McNamara was an American business executive and the eighth Secretary of Defense, serving under Presidents John F. Kennedy and Lyndon B. Johnson from 1961 to 1968, during which time he played a large role in escalating the United States involvement in the Vietnam War...
was particularly opposed to the bomber force and repeatedly stated he felt that the combination of SLBMs and ICBMs would render them useless. He pressed for the cancellation of Skybolt as an unnecessary program.
The British, on the other hand, had cancelled all other projects to concentrate fully on Skybolt. When McNamara informed them that they were considering cancelling the program in November 1962, a firestorm of protest broke out in the House of Commons. Jo Grimond noted "Does not this mark the absolute failure of the policy of the independent deterrent? Is it not the case that everybody else in the world knew this, except the Conservative Party in this country?" As the political row grew into a major crisis, an emergency meeting between parties from the US and UK was called, leading to the Nassau agreement
Nassau agreement
The Nassau Agreement, concluded on 22 December 1962, was a treaty negotiated between President John F. Kennedy for the United States and Prime Minister Harold Macmillan for the United Kingdom...
.
Over the next few days a new plan was hammered out
Polaris Sales Agreement
The Polaris Sales Agreement was an agreement between the United States and the United Kingdom which formally arranged for the Polaris missile system to be provided to the UK to maintain its independent nuclear deterrent. The arrangement had been set up in principle as a result of the Nassau Agreement...
that saw the UK purchase the Polaris SLBM, but equipped with British warheads that lacked the dual-key
Two-man rule
The two-man rule is a control mechanism designed to achieve a high level of security for especially critical material or operations. Under this rule all access and actions requires the presence of two authorized people at all times.-Nuclear weapons:...
system. The UK would thus retain its independent deterrent force, although its control passed from the RAF largely to the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
. The Polaris, a much better weapon system for the UK, was a major "scoop" and has been referred to as “almost the bargain of the century” The RAF kept a tactical nuclear capability with the WE.177
WE.177
WE.177 was the last air-delivered tactical nuclear weapon of the British Armed Forces. There were three versions; WE.177A was a boosted fission weapon, while WE.177B and WE.177C were thermonuclear weapons...
which armed V-bombers and later the Panavia Tornado
Panavia Tornado
The Panavia Tornado is a family of twin-engine, variable-sweep wing combat aircraft, which was jointly developed and manufactured by the United Kingdom, West Germany and Italy...
force. The "Skybolt Crisis" was a major event in the eventual downfall of the Macmillan administration.
Limited flight tests with the remaining XGAM-87A missiles continued after program cancellation. In June 1963, the XGAM-87A was redesignated as XAGM-48A.
Description
The GAM-87 was powered by a two-stage solid-fuel rocket motor. Each B-52H was to carry four missiles, two under each wing on side-by-side pylons, while the Avro VulcanAvro Vulcan
The Avro Vulcan, sometimes referred to as the Hawker Siddeley Vulcan, was a jet-powered delta wing strategic bomber, operated by the Royal Air Force from 1956 until 1984. Aircraft manufacturer A V Roe & Co designed the Vulcan in response to Specification B.35/46. Of the three V bombers produced,...
carried one each on smaller pylons. The missile was fitted with a tailcone to reduce drag while on the pylon, which was ejected shortly after being dropped from the plane. After first stage burnout, the Skybolt coasted for a while before the second stage ignited. First stage control was by eight movable tail fins, while the second stage was equipped with a gimballed nozzle.
Guidance was entirely by inertial platform. The current position was constantly updated from the host aircraft though accurate fixes, meaning that the accuracy of the platform inside the missile was not as critical.
See also
- List of military aircraft of the United States
- List of missiles by nation
Further reading
- Neustadt, Richard E. Report to JFK: The Skybolt Crisis in Perspective. Ithaca, NY: Cornell University Press, 1999. ISBN 0-8014-3622-2.
External links
- Skybolt, Encyclopedia Astronautica