The Trident missile is truly an amazing piece of kit. The most remarkable thing for me is that would be able to operate with zero external systems (such as GPS)

The Trident missile is truly an amazing piece of kit. The most remarkable thing for me is that would be able to operate with zero external systems (such as GPS), so that in the event of a complete electromagnetic blackout it could still hit its target. It does this by fixing off the stars (http://www.nytimes.com/1982/07/13/science/trident-s-technology-may-make-it-a-potent-rival-to-land-based-missiles.html?&pagewanted=all http://www.nytimes.com/1982/07/13/science/trident-s-technolo...). The Royal Navy subs only carry upto 48 warheads, even though they are capable of carrying 192, so I guess that's only 48 major cities from the Uk contingent :o (http://www.fas.org/nuke/guide/uk/slbm/vanguard.htm http://www.fas.org/nuke/guide/uk/slbm/vanguard.htm) One fascinating limitation (read engineering opportunity) of these boats is they way they dispose of waste gas (such as that produced in oxygen generation). It's ejected from the sub, but tends to form into largish bubbles, which when they hit the surface are sometimes detectable by spy satellites - so their location is sometimes compromised. (sorry, can't find a link to back this up - I wonder why..) I believe the Vanguard class subs (the Royal Navy's Trident bearing subs) can carry ~4 months food supply, so that's how often they have to resupply.