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Lockheed UGM-96 Trident I

The UGM-96 Trident I C-4 was a long-range replacement for the UGM-73 Poseidon C-3 SLBM (Submarine-Launched Ballistic Missile). It was itself replaced by the UGM-133 Trident II.

In 1971, the U.S. Navy started the ULMS (Undersea Long-Range Missile System) program to develop an SLBM with significantly longer range than the UGM-73 Poseidon. Prime contractor Lockheed proposed a two-phase program. Initially, an advanced derivative of Poseidon (tentatively called EXPO - Extended-Range Poseidon) would be developed, which was to have the same external dimensions as Poseidon to make use of existing submarines. Later on, the ultimate long-range SLBM would be developed as a larger missile, together with a new class of ballistic missile submarines. The EXPO concept evolved into the Trident I C-4, while the new enlarged design eventually became the UGM-133 Trident II D-5.

Image: Lockheed Martin Missiles & Space
SLBM family: UGM-27A, UGM-27B, UGM-27C, UGM-73A, UGM-96A, UGM-133A

In 1974, Lockheed was awarded a development contract for the UGM-96A Trident I C-4 missile. The adoption of the SLBM designator C-4 clearly indicated that Trident I was regarded as an evolutional step from Poseidon C-3, compatible with the latter's launch platforms. To achieve the desired range of 7400 km (4000 nm) (compared to 5280 km (2850 nm) for Poseidon), several new technologies were used. One of the most important was a completely new propulsion system. The rocket motors use a new higher-energy propellant, light-weight Kevlar casings, and make more efficient use of the available fuel by completely buring out the motor instead of neutralizing the thrust for trajectory control. Another innovative feature of the UGM-96A is an extendable "aero-spike", which is extended from the nose after launch. This spike creates a shock cone, reducing frontal drag by about 50%. The aero-spike allowed the use of a significantly blunter missile nose, which not only houses the warhead section, but also a third rocket stage. The first flight of an UGM-96A occurred in January 1977, and the first launch from a submarine - USS Francis Scott Key (SSBN-657) - succeeded in July 1979. In October that year, SSBN-657 became the first submarine to go on patrol with the Trident I C-4.

Photo: U.S. Navy

The UGM-96A SLBM's warhead section normally consisted of six MK 4 independent reentry vehicles, each fitted with a 100 kT W-76 thermonuclear warhead. Up to 14 MIRVs could be loaded, of course reducing the range of the missile. The Trident I was also equipped with a new MK 5 stellar/interial navigation system, which increased accuracy to about 380 m (1250 ft) CEP.

The Trident I C-4 replaced the UGM-73 Poseidon missiles in 12 SSBNs, and was also deployed on the first Ohio class (SSBN-726) submarines. These SSBNs are designed to carry 24 of the larger UGM-133 Trident II D-5 missiles, but the first eight were equipped with Trident I because the D-5 was not yet available. The Strategic Arms Reduction Treaty (START) II limited the number of Trident submarines of the U.S. Navy to 18. All 18 Ohio class boats have been completed by 1997, and therefore all earlier SSBNs have been decommissioned. Between 1977 and 1986, Lockheed built about 600 UGM-96A missiles, for a peak deployment level of 384.

Photos: U.S. Navy Photo: Lockheed Martin Missiles & Space

At the end of the 1990, the Navy began to refit the four newer Trident I C-4 SSBNs with the Trident II D-5. The first two conversions were completed during 2002, and the whole program was completed by 2007. The four oldest Trident I SSBNs have been retired as ballistic missile submarines, and all of them are being converted to SSGNs (Guided Missile Submarines) as platform for the UGM-109 Tomahawk SLCM. The first of these boats left strategic service in October 2002, and the three others followed in 2003 and 2004. The first SSGN, USS Ohio (SSGN-726), rejoined the fleet in 2006, and the last conversion will be completed in 2008.


Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for UGM-96A:

Length10.39 m (34 ft 1.2 in)
Diameter1.88 m (6 ft 2 in)
Weight33000 kg (73000 lb)
Range7400 km (4000 nm)
Propulsion1st stage: Thiokol solid-fueled rocket
2nd stage: Hercules solid-fueled rocket
3rd stage: United Technologies Corp. solid-fueled rocket
Warhead6x W-76 thermonuclear (100 kT) in 6x MK 4 RV

Main Sources

[1] James N. Gibson: "Nuclear Weapons of the United States", Schiffer Publishing Ltd, 1996
[2] Norman Friedman: "US Naval Weapons", Conway Maritime Press, 1983
[3] Bill Gunston: "The Illustrated Encyclopedia of Rockets and Missiles", Salamander Books Ltd, 1979
[4] René J. Francillon: "Lockheed Aircraft since 1913", Putnam, 1987

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Last Updated: 18 January 2008/i>