for Submariners

by Hamilton 1:1 Communications, LLC

James Madison Class
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SSBN-627 James Madison-Class Submarines 



The James Madison class of submarine was an evolutionary development from the Lafayette class of fleet ballistic missile submarine. They were identical to the Lafayettes except for being designed to carry the Polaris A-3 missile instead of the earlier A-2. During the late 1970s and early 1980s, select units were further modified to carry Trident-I (C-4) missiles.


Improvements in the James Madison class included the ballistic missile, guidance, fire control, navigation and launcher systems. The improved missile system introduced was the Polaris A3 missile. The A3 was restricted by size because it had to fit into the existing submarine launch tube. But it was 1.5 inches (3.8 cm) longer, weighed 4,000 pounds (1,800 kg) more, and had a range 1,000 nautical miles (1,900 km) farther than the A2. Additionally, the number of reentry systems was increased from 1 to 3, making this the first multiple reentry vehicle missile.


The guidance, fire control, and navigation systems were improved to account for the longer range of the A3 missile. The launcher system was improved by replacing the liquid springs on which the launch tube rested with polyurethane foam.

Boats Built




General Dynamics Electric Boat Division;

Mare Island Naval Shipyard,

Portsmouth Naval Shipyard,
Newport News Shipbuilding



Power Plant:

S5W nuclear reactor
two geared steam turbines,

one shaft


425 ft. (130 meters)


33 ft.  (10 meters)


31 ft 6 in. (9.60 meters)


7,200 long tons (7,370t) surfaced

8,250 long tons (8,380t) submerged


20+ knots surfaced

25 knots submerged


(Two Crews)

13 Officers,

130 Men


4 × 21 in (530 mm) torpedo tubes for Mark 48 torpedoes
16 × vertical tubes for Polaris or Poseidon ballistic missiles