Trident missile

The Trident missile, named after the trident, is an intercontinental ballistic missile (ICBM) which is armed with nuclear warheads and is launched from submarines (SSBNs), making it a SLBM.

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 whose range is increased by an aerospike, a telescoping outward extension that halves frontal drag.

The Trident is carried by fourteen active US navy Ohio class submarines and, with British warheads, four Royal Navy Vanguard class submarines.

The launch from the submarine occurs below the ocean surface. The missiles are ejected from their tubes by gas pressure created by a "gas generator", a solid-fuel rocket motor attached to the bottom of the missile tube which heats a pool of water creating steam. After the missile leaves the tube and rises through the water over the submarine, the first stage motor ignites, the aerospike extends, and the boost stage begins. Ideally, the missile is "sheathed" in gas bubbles for its entire time in the water, so liquid never touches its fuselage. Within about two minutes, after the third stage motor fires, the missile is traveling faster than 20,000 ft/s (6,000 m/s).

Trident I (C4) was deployed in 1979 and phased out in the 1990s and early 2000s. Trident II (D5) was deployed in 1990, and was planned to be in service for the thirty year life of the submarines, until 2027. However, a decision was taken in 2002 to extend the life of the submarines and the D5 missiles to forty-five years. This requires a D5 Life Extension (D5LE) Program, which is currently ongoing. The main aim is to replace obsolete components at minimal cost, while maintaining the demonstrated performance of the existing missiles. In 2006, The UK Government said that it would maintain the UK's independent nuclear deterrent, although it still had to decide exactly how. It is expected to join in fully with the D5LE program for the missiles and have its own program for extending the Vanguard class submarines' lives and maintaining the UK's own warheads.
As a first step, the specialised Submarine Command System (SMCS) which was originally developed for the UK's Vanguard submarines, is being converted to a new version called SMCS-NG which runs on the Microsoft Windows operating system. This is probably the first use of Microsoft Windows to command a militry platform whose purpose is the firing of intercontinental nuclear missiles. While the UK Government has promised an extensive and open debate about the future of Trident, this first step (which, in computing terms, is a radical change of technology) was taken with neither the knowledge nor the agreement of the UK's parliament; indeed: in October 2004, the UK's parliament was explicitly told that there were no plans in place to make this modification. However, contracts were placed with the supplier, BAE SYSTEMS, one month later.

Trident I (C4) UGM-96A

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

Trident I first launch on 18 January 1977 at Cape Canaveral

Characteristics
* Purpose: strategic nuclear deterrence
* Contractor: Lockheed Martin Space Systems, Sunnyvale, California
* Propulsion: three-stage solid-propellant rocket
* Length: 34 ft (10.2 m)
* Weight: 73,000 lb (33,142 kg)
* Diameter: 74 in (1.8 m)
* Range: 7400 km (4,600 statute miles)
* Guidance system: inertial
* CEP: 1250 ft (380 m)
* Warhead: nuclear multiple independently targetable reentry vehicles (MIRV). Eight W76 (100 kt) warheads (Mark 4).
* Date deployed: 1979

Trident II (D5) UGM-133A

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 later Ohio SSBNs.Characteristics
* Purpose: strategic nuclear deterrence
* Contractor: Lockheed Martin Space Systems Co., Sunnyvale, Calif.
* Unit Cost: $30.9 million
* Propulsion: Three-stage solid-propellant rocket
* Length: 44 ft (13.41 m)
* Weight: 130,000 lb (58,500 kg)
* Diameter: 83 in (2.11 m)
* Range: 12000 km (7,500 statute miles)
* Maximum speed: 29,030 km/h (18,000 mph)
* Guidance system: inertial
* CEP: 300 ft (90 m)
* Warhead (in USA usage only): nuclear MIRV. Up to eight W88 (475 kt) warheads (Mark 5) or eight W76 (100 kt) warheads (Mark 4).
* Date deployed: 1990

Conventional Trident

The Pentagon developed the Conventional Trident Modification program in 2006 to diversify its strategic options. The US $503 million program would have converted existing Trident II missiles (presumably those scheduled for decommissioning of their warheads) into conventional weapons. 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.