How U.S. Submarines would double length of their normal patrols

Submarine Frequently Asked Questions

(provided by Chief of Naval Operations Submarine Warfare Division)
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17. (of 61.) How long can submarines stay underwater?

Nuclear-powered submarines can stay submerged for long periods of time. They are designed and manned to stay underwater long enough to support a wide variety of missions, which can last for several months. Submarines have equipment to make oxygen and keep the air safe. Food and supplies are the only limitations on submergence time for a nuclear submarine. Normally, submarines carry a 90-day supply of food. [emphasis added]

Research into preservation of foodstuff supplied by a well-known American purveyor has recently been completed. At ambient submarine compartment temperatures and humidity levels the food can be stored almost anywhere --- no refrigeration required-- far longer than the 90 days.
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Utilizing a fast food, fast boats (SSNs) may soon be capable of making missions as long as 6-months.
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If human safety tests now being conducted by NASA and the Naval Submarine Medical Research Laboratory prove successful, sea endurance trials will commence with a yet to be named SSN.
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Traditional sub cuisine with refrigerated stores will be utilized to break the monotony of fast food for breakest, lunch and dinner. Ordinary McDonald's Happy Meals, which have been shown to resist decomposition for six months (photos below) will need only fresh condiments and zapping in a microwave to make submarine endurance awesome.

Since assignment of women to SSNs is not currently planned, another potential impediment to doubling cruise duration will be entirely avoided.
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Submarines are always silent and strange.