The Navy D5 missile?
The Trident II Strategic Weapon System (SWS) is deployed aboard Ohio-class (Trident) submarines and consists of: the Trident II (D5) Submarine Launched Ballistic Missile (SLBM); Reentry System; and supporting Shipboard Systems.
http://www.navy.mil/navydata/fact_display.asp?cid=2200&tid=1400&ct=2