Trident II D-5 Fleet Ballistic Missile
Trident II D-5 is the sixth generation member of the U.S. Navy's Fleet Ballistic Missile (FBM) program which started in 1956. Systems have included the Polaris (A1),Polaris (A2), Polaris (A3), Poseidon (C3), and Trident I (C4). The first deployment of Trident II was in 1990 on the USS Tenessee (SSBN 734). While Trident I was designed to the same dimensions as the Poseidon missile it replaced, Trident II is a little larger.
The Trident II D-5 is a three-stage, solid propellant, inertially guided FBM with a range of more than 4,000 nautical miles (4,600 statute miles or 7,360 km) Trident II is more sophisticated with a significantly greater payload capability. All three stages of the Trident II are made of lighter, stronger, stiffer graphite epoxy, whose integrated structure mean considerable weight savings. The missile's range is increased by the aerospike, a telescoping outward extension that reduces frontal drag by about 50 percent. Trident II is fired by the pressure of expanding gas in the launch tube. When the missile attains sufficient distance from the submarine, 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 20,000 feet (6,096 meters) per second.
The ten Trident submarines in the Atlantic fleet were initially equipped with the D-5 Trident II missile. The eight submarines in the Pacific were initially equipped with the C-4 Trident I missile. In 1996 the Navy started to backfit the eight submarines in the Pacific to carry the D-5 missile.
The Minuteman ICBM always had the theory that the missiles are at T-minus thirty seconds and holding. The Trident system and the Polaris system have been designed with a different philosophy. They're at sea and can be up and running in a matter of a few hours. But they don't try to keep them on alert all the time like the Minuteman.
The Nuclear Posture Review (NPR), which was forwarded to Congress in December 2001, outlined the Strategic Submarine Force structure: 14 SSBNs outfitted with the TRIDENT II (D5) Strategic Weapon System in 2 oceans. In accordance with the NPR, the remaining four of the original eighteen TRIDENT SSBNs will be converted to SSGNs. To achieve an all D5 SSBN force, backfit of four of the submarines to the D5 Strategic Weapon System from the TRIDENT I (C4) Strategic Weapon System has been initiated. The C4 SWS will be retired in FY 2005. The TRIDENT SWS and support facilities were designed from the beginning to handle the newer and larger missile system with minimal impact and cost.
TRIDENT II/D5 missile construction continues with an inventory objective of 425 missiles for 14 TRIDENT II/D5 SSBNs in two oceans. Planned procurement through FY 2005 is 5 to 12 missiles per year.
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