Trident (missile) explained

Is Missile:yes
Trident II
Vehicle Range:Greater than 4,000 nautical miles (4,600 statute miles, or 7,360 km)
Filling:up to Eight W76/W88
Yield:Up to 3.8 megatons
Engine:three stage solid propellant
Guidance:Inertial guidance system, with Star-Sighting
Cep:90 meters (if GPS guidance is used)
Speed:29,050 km/h (18,000 mph)
Length:44 ft (13.41 m)
Diameter:83 in (2.11 m)
Weight:58,500 kg (130,000 lb)
Payload Capacity:2,800 kg (6,170 lb)
Manufacturer:Lockheed Martin Space Systems
Unit Cost:$30.9 million[1]
Service:1990 - present
Used By:United States
United Kingdom

This article contains technical information about the Trident ballistic missile. For a discussion of the British Trident weapons program, see UK Trident programme

The Trident missile is a multiple independently targetable reentry vehicle submarine-launched ballistic missile (SLBM) designed by Lockheed Martin Space Systems in the United States which is armed with nuclear warheads and is launched from SSBNs, nuclear-powered ballistic missile submarines. Trident missiles are carried by fourteen active US Navy Ohio class submarines, with U.S.-designed warheads, and four Royal Navy Vanguard class submarines, with British warheads.


Trident I (C4) was deployed in 1979 and phased out in the 1990s and early 2000s. Trident II (D5) was first deployed in 1990, and was planned to be in service for the thirty year life of the submarines, until 2027.

Trident missiles are provided to the United Kingdom under the terms of the 1963 Polaris Sales Agreement which was modified in 1982 for Trident. British Prime Minister Margaret Thatcher had written to President Carter on July 10 1980 to request that he approve supply of Trident I missiles. However in 1982 Thatcher wrote to President Reagan to request the United Kingdom be allowed to procure the Trident II (Trident D5) system, the procurement of which had been accelerated by the US Navy. This was agreed in March 1982.[2] Under the agreement, the United Kingdom made a 5% research and development contribution.

D5 life extension

In 2002, the United States Navy announced plans to extend the life of the submarines and the D5 missiles to the year 2040.[3] This requires a D5 Life Extension (D5LE) Program, which is currently underway. The main aim is to replace obsolete components at minimal cost by leveraging commercial off the shelf (COTS) hardware; all the while maintaining the demonstrated performance of the existing Trident II missiles. In 2007, Lockheed Martin was awarded a total of $789.9 million in contracts to perform this work, which also includes upgrading the missiles' guidance and reentry systems.[4] The British Prime Minister (Tony Blair at the time) was quoted as saying the issue would be fully debated in Parliament prior to a decision being taken.[5] And on December 4 2006, Tony Blair outlined plans in Parliament to build a new generation of submarines to carry existing Trident missiles, and join the D5LE project to refurbish them.[6]


The launch from the submarine occurs below the ocean surface. The missiles are ejected from their tubes by igniting an explosive charge in a separate container which is separated by two titanium alloy pinnacles activated by a triple alloy steam system. The energy from the blast is directed to a water tank, which is flash-vaporized to steam. The subsequent pressure spike is strong enough to eject the missile out of the tube and give it enough momentum to reach and clear the surface of the water. However, should this fail, there are several safety mechanisms that can either deactivate the missile before launch or guide the missile through an additional phase of launch. Inertial motion sensors are activated upon launch, and when the sensors detect downward acceleration after being blown out of the water, the first stage engine ignites. The aerospike, a telescoping outward extension that halves aerodynamic drag, is then deployed, and the boost phase begins. The missile is pressurized with nitrogen to prevent the intrusion of water into any internal spaces, which could damage the missile or add weight which would destabilize the missile. When the third stage motor fires, within two minutes of launch, the missile is traveling faster than 20,000 ft/s (6,000 m/s), or 13,600 mph.

The missile attains a temporary low altitude orbit only a few minutes after launch. The Guidance System for the missile is an Inertial Guidance System with an additional Star-Sighting system, which is used to correct small positional errors that have accrued during the flight. GPS has been used on some test flights but is assumed not to be available for a real mission.

Once the Star-sighting system has been completed, the missile deploys the multiple independent reentry vehicles as their individual targets come within range. The lateral area coverage of the targets remains classified.

The Trident was built in two variants: the I (C4) UGM-96A and II (D5) UGM-133A. The C4 and D5 designations put the missiles within the "family" that started in 1960 with Polaris (A1, A2 and A3) and continued with the 1971 Poseidon (C3). Both Trident versions are three-stage, solid-propellant, inertially guided missiles. In the post-boost phase, the Trident missile uses stellar sighting to update its position and reduce the drift error inherent in all inertial reference systems.

Trident I (C4) UGM-96A

See main article: UGM-96 Trident I. The first eight Ohio-class subs were built with the Trident I missiles. Trident were also retrofitted onto 12 SSBNs of the James Madison and Benjamin Franklin classes, replacing Poseidon missiles.

Trident II (D5) UGM-133A

See main article: UGM-133 Trident II. During the late 1970s, the Soviet Union developed a large number of heavy, increasingly accurate, MIRVed ICBMs (like the SS-18) that seriously threatened the survival of Minuteman III missiles in their silos. If the Soviet Union could have knocked out the majority of these missiles and the strategic bombers on ground, it would have left the United States with no counterforce capability for the second strike. The Poseidon and Trident I SLBMs were not accurate enough for counterforce strikes. If the Soviet first strike would have avoided hitting civil targets, the US might have been forced not to retaliate against Soviet cities, because of similar Soviet countercity capabilities. So the United States needed weapons which could survive a Soviet first-strike and neutralize the remaining Soviet strategic arsenal, in order to avoid the nuclear blackmail.

The second variant of the Trident is more sophisticated and can carry a heavier payload. It is accurate enough to be a first strike weapon. All three stages of the Trident II are made of graphite epoxy, making the missile much lighter. The Trident II was the original missile on the British Vanguard and Ohio SSBNs since USS Tennessee (SSBN-734). The D5 missile is currently carried by twelve Ohio class SSBNs.[7] Lockheed has carried out 124 consecutive successful test launches of the D5 missile since 1989, according to a company press release.

Conventional Trident

The Pentagon proposed the Conventional Trident Modification program in 2006 to diversify its strategic options, as part of a broader long-term strategy to develop worldwide rapid strike capabilities, dubbed "Prompt Global Strike".

The US $503 million program would have converted existing Trident II missiles (presumably two missiles per submarine) into conventional weapons, by fitting them with modified Mk4 reentry vehicles equipped with GPS for navigation update and a reentry guidance and control (trajectory correction) segment to perform 10 m class impact accuracy. No explosive is said to be used since the reentry vehicle's mass and hypersonic impact velocity provide sufficient mechanical energy and "effect". It offered the promise of accurate conventional strikes with little warning and flight time.

The primary drawback would have been establishing sufficient warning systems so that other nuclear countries would not mistake it for a nuclear launch. For that reason among others, this project raised a substantial debate before US Congress for the FY07 Defense budget, but also internationally.[8] Russian President Vladimir Putin, among others, warned that the project would increase the danger of accidental nuclear war. "The launch of such a missile could ... provoke a full-scale counterattack using strategic nuclear forces," Putin said in May 2006.[9]

UK Renewal

On 14 March 2007, the government of the United Kingdom won Commons support for plans to renew the UK's nuclear submarine system. Between £15bn and £20bn will be spent on new submarines to carry the Trident missiles. The fleet will take an estimated 17 years to develop and build, and will last until 2050. More than 90 Labour members of the Commons voted against the proposed upgrade to the missile system, and the vote was only won with the support of the Opposition, although with the substantial support of 63% of MPs.[10]

On 16 January 2009, some retired senior military officers announced that they think that the follow-on Trident program (that was approved back in 2007) should be scrapped. General Lord Ramsbotham commented that "Our independent deterrent has become virtually irrelevant except in the context of domestic politics."[11]


See also

External links

Notes and References

  1. The US Navy - Fact File
  2. Reagan letter to Thatcher
  3. Navy Awards Lockheed Martin $248 Million Contract for Trident II D5 Missile Production and D5 Service Life Extension. Lockheed Martin Space Systems Company. 2002-01-29. 2009-01-28.
  4. Lockheed press release April 9, 2007
  5. BBC News Trident decision 'not yet taken'
  6. BBC News UK nuclear weapons plan unveiled
  7. Lockheed press release April 9, 2007
  8. Trident plan wins Commons support
  9. Generals in 'scrap Trident' call