Gronton, Conn. ? The Navy is considering lengthening the standard deployment of attack submarines beyond six months as it faces rising demands with a fleet that has been shrinking since the end of the Cold War, the commander of American submarine forces told The Associated Press in an interview.

Already, attack submarines are at times asked to stay out longer than six months — extensions that can be trying for sailors who serve in tightly confined spaces with limited outside communication as members of the “silent service.”

Vice Adm. John Richardson told the AP this week that keeping subs out longer is one of several options the Navy is considering as the number of attack subs is projected to continue dropping in the next decade and beyond.

“I think we’re looking at all the options,” he said. “As you try and maintain the same presence with fewer hulls, there are all sorts of variables in that equation. One would be extending deployment lengths. So that’s certainly on the table.”

Submariners are not alone in seeing deployments extended periodically, as two wars and evolving threats strain the entire U.S. military. A spokeswoman for the admiral, Navy Cmdr. Monica Rousselow, said it is impossible to say how long sub deployments might become because so many factors are involved.

Extending deployments permanently would save resources because the Navy could complete more missions with the nuclear-powered submarines that it has available. The fast-attack subs travel to far-flung corners of the globe for missions including intelligence gathering and firing missiles, but they can maintain a presence only for so long before making the time-consuming journey back to U.S. bases.

Navy contractors began stepping up submarine production this year, but pressure on the defense budget has raised uncertainty about future procurement. While some critics describe the multibillion-dollar vessels as costly relics of a different era, Richardson says submarines remain integral to America’s nuclear deterrence strategy and the security of a nation that conducts the vast majority of its trade by maritime channels.

Enlisted crew members on the attack subs sleep six to a room, stacked in bunk areas barely larger than a closet, and navigate corridors so narrow only one person can pass at a time. The deployments are typically broken up by port calls, but they can remain at sea for weeks or months at a time. The bigger, roomier ballistic missile subs generally stay closer to their home ports and have shorter deployments.

Sailors in the elite, all-volunteer submarine force go through psychological screening to make sure they can cope with the tight quarters and extended time beneath the ocean’s surface. Nobody with claustrophobic tendencies is allowed on board.

But retired submariners say the time at sea does take a physical and emotional toll, particularly when a mission is suddenly extended.