Editing UGM-27 Polaris (section)

== After Polaris ==
To meet the need for greater accuracy over the longer ranges the Lockheed designers included a reentry vehicle concept, improved guidance, fire control, and navigation systems to achieve their goals.  To obtain the major gains in performance of the Polaris A3 in comparison to early models, there were many improvements, including propellants and material used in the construction of the burn chambers.  The later versions (the A-2, A-3, and B-3) were larger, weighed more, and had longer ranges than the A-1. The range increase was most important: The A-2 range was {{convert|1500|nmi|km|abbr=off}}, the A-3 {{convert|2500|nmi|km|abbr=off}}, and the B-3 {{convert|2000|nmi|km|abbr=off}}. The A-3 featured multiple re-entry vehicles ([[Multiple Reentry vehicle|MRVs]]) which spread the warheads about a common target, and the B-3 was to have [[penetration aids]] to counter [[Soviet Union|Soviet]] [[Anti-Ballistic Missile]] defenses.

The U.S. Navy began to replace Polaris with Poseidon in 1972. The B-3 missile evolved into the C-3 [[Poseidon missile]], which abandoned the decoy concept in favor of using the C3's greater throw-weight for larger numbers (10–14) of new hardened high-re-entry-speed [[reentry vehicle]]s that could overwhelm Soviet defenses by sheer weight of numbers, and its high speed after re-entry.  This turned out to be a less than reliable system and soon after both systems were replaced by the Trident. A proposed Undersea Long-Range Missile System (ULMS) program outlined a long-term plan which proposed the development of a longer-range missile designated as ULMS II, which was to achieve twice the range of the existing Poseidon (ULMS I) missile. In addition to a longer-range missile, a larger submarine (Ohio-class) was proposed to replace the submarines currently being used with Poseidon. The ULMS II missile system was designed to be retrofitted to the existing SSBNs, while also being fitted to the proposed Ohio-class submarine.

In May 1972, the term ULMS II was replaced with Trident. The Trident was to be a larger, higher-performance missile with a range capacity greater than 6000 miles. Under the agreement, the United Kingdom paid an additional 5% of their total procurement cost of 2.5 billion dollars to the U.S. government as a research and development contribution.<ref name=NAO-1987>{{cite book |title=Ministry of Defence and Property Services Agency: Control and Management of the Trident Programme |publisher=[[National Audit Office (United Kingdom)|National Audit Office]] |date=29 June 1987 |pages=Part 4 |isbn=978-0-10-202788-4 |no-pp=true}}</ref>
In 2002, the United States Navy announced plans to extend the life of the submarines and the D5 missiles to the year 2040. This requires a D5 Life Extension Program (D5LEP), which is currently underway. The main aim is to replace obsolete components at minimal cost by using commercial off the shelf (COTS) hardware; all the while maintaining the demonstrated performance of the existing Trident II missiles.<ref>{{cite press release|title=Navy Awards Lockheed Martin $248 Million Contract for Trident II D5 Missile Production and D5 Service Life Extension |publisher=Lockheed Martin Space Systems Company |date=29 January 2002 |url=http://www.lockheedmartin.com/news/press_releases/2002/NavyAwardsLockheedMartin248MillionC.html |access-date=2018-04-17 |url-status=dead |archive-url=https://web.archive.org/web/20090227182711/http://www.lockheedmartin.com/news/press_releases/2002/NavyAwardsLockheedMartin248MillionC.html |archive-date=27 February 2009 }}</ref>