Groton — Jimmy Carter, the third and final Seawolf-class submarine that has been heavily modified for special operations, departed Electric Boat on Tuesday for the first phase of its sea trials. Under Navy policy the departure was not publicly announced, but Navy and EB sources said the Carter finished its most intensive in-port test last week without any major problems and was deemed ready for Alpha trials, as they are known. Last week the crew had conducted a “fast cruise,” in which they simulate submarine operations, including running the reactor up to full power, while tied alongside the pier. It...