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

There are 14 active US Ohio class submarines and 4 UK Vanguard class submarines equipped with the two variants of Trident: the initial Trident-I (C-4) UGM-93A and subsequent Trident-II (D-5) 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 through to the 1971 Poseidon (C3) to the two Trident versions.

Both versions of the Trident are three-stage, solid-propellant, inertially guided missiles. The range of both models of the missile is increased by an aerospike, a telescoping outward extension that reduces frontal drag by about 50 percent.

The launch from the submarine occurs below the ocean surface, they are ejected from their launch tubes by gas pressure created by a "gas generator," a solid fuel rocket motor attached to the bottom of the missile tube and exhausting into it. After the missile leaves the tube and rises through the water over the submarine (in a bubble of gas -- water never contacts the missile) the first stage motor ignites, the aerospike extends, and the boost stage begins. Within about two minutes, after the third stage motor kicks in, the missile is traveling in excess of 6100 m/s (20,000 ft/s).

Trident I (C4) was first deployed in 1979 and gradually phased out through the 1990s and early 2000s. Trident II (D5) was first deployed in 1990 and is planned to be deployed past 2020.

Contents

1 Trident-I (C4) UGM-93A 1.1 Trident-I Backfit program 2 Trident-II (D5) UGM-133A 3 External links

Trident-I (C4) UGM-93A

The first eight units of the Ohio-class submarines were built with the Trident-I missile system installed, all units of the class have now been upgraded to the Trident-II

Trident I (C4) - General Characteristics

• Primary Function: Strategic Nuclear Deterrence
• Contractor: Lockheed Martin Space Systems, Co., Sunnyvale, Calif.
• 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
• Warhead: Nuclear multiple independently targetable reentry vehicles (MIRV). Eight W76 (100 kt) warheads (Mark 4).
• Date Deployed: 1979

Trident-I Backfit program

Trident I missiles were also installed in 12 SSBN's of the James Madison and Benjamin Franklin classes, replacing the Poseidon missiles previously installed in those units.

Trident-II (D5) UGM-133A

Trident II is more sophisticated than Trident I (C4) with a significantly greater payload capability. The Trident II is also accurate enough to be considered a first strike weapon. All three stages of the Trident II are made of graphite epoxy, whose integrated structure means considerable weight saving. Trident II replaces the earlier Trident I missile in those units of the Ohio class built with Trident I. Additional units were built with Trident II. The Trident II is also provided to the United Kingdom which equips the missile with their own warheads and deploys the missiles on the Royal Navy's own Vanguard-class submarines.

Trident II (D5) - General Characteristics

• Primary Function: Strategic Nuclear Deterrence
• Contractor: Lockheed Martin Space Systems Co., Sunnyvale, Calif.
• Unit Cost: $30.9 million
• Power Plant: 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: Greater than 7400 km (4,600 statute miles)
• Guidance System: Inertial
• Warhead: Nuclear MIRV. Up to eight W88 (475 kt) warheads (Mark 5) or ten W76 (100kt) warheads (Mark 4).
• Date Deployed: 1990

External links

• http://www.chinfo.navy.mil/navpalib/factfile/missiles/wep-d5.html