As others say, they will get you there and put you up, ie you don't pay anything during your interview time in CT. Get up early, check in, get a temporary clearance. Get an interview schedule. Take a tour of the submarine yard. Go on scheduled interviews. Have lunch/interview. Go home.
Overall, it was a great experience. THEY ARE HIRING, so do not be scared or intimidated. All the interviewers were so kind and generous with their time and stories. It was much more of a conversation. Just be active, be thoughtful, good posture, smile, show signs of listening, be inquisitive. Do THESE things and I am sure that if they brought you all the way up there... you will get the job
Personally, interviewed 3 times for one department. Once in another. Got both jobs.