For six months a year the rumbling of his stomach, not the movement of the sun, is Frank Calvin's clock.
''If they serve eggs and toast instead of hamburgers and French fries, I know it's morning,'' says the sonar technician assigned to the ballistic-missile submarine USS George Washington Carver. ''It's the only way you can tell,'' he chuckles. ''You can't pull back the curtains to see what time of day it is or what the weather is like.''
Both he and 130 mates not only go down to the sea in ships, they go under it - three months at sea, three months on shore. And if any of us topside wonder what the ''climate'' is like 200 to 750 feet below the ocean's surface on one of the US Navy's 123 nuclear submarines, it's not like in the movies.
Cinema images of horns blasting, enemy ships in the cross hairs of periscopes , orders barked to ''fire torpedo No. 1,'' the strained faces of men listening for depth charges just don't fit.
Looking through the other end of the periscope into a nuclear sub shows a far less glamorous, a tediously routine, and a decidedly more technical picture than the movies suggest. It is a world of computers vectoring (positioning) the ship toward a target; men who live, sleep, and eat applied physics, electronics, and mechanical engineering; sonar bleeps; silence and stealth.
Submariners are at ease living on auditory scraps of information. Their environment is a sonar puzzle constantly changing, constantly being put together. Acoustic soundings, not the sun or stars, provide the information to determine where their ship is, where it is going - and who else is out there.
Submariners are elitist and make no bones about their contention that the wave of the Navy's future is under, not on, the water. Talk to one and he will tell you the dominant and technologically superior seaborne weapon system of World War I was the battleship; of World War II, the aircraft carrier. Today, the naval torch has passed to them.
It wasn't a carrier pilot who said, ''There are two kinds of ships: submarines and targets.''
All nuclear submarines are capable of operating independently of the earth's atmosphere for long periods of time.
Usually, the reason a nuclear sub has to surface is to get more food for its crew. It produces its own oxygen, and up to 8,000 gallons of fresh water a day. The reactor propels the ship and drives auxiliary generators for light and electricity.
The pressurized water reactor and associated steam plant need no oxygen. Neither is there any gaseous exhaust. In fact, not only does a nuclear sub make its own oxygen from seawater, it also ''scrubs'' stale air (removes carbon dioxide) then burns the waste gas in a catalytic converter at 600 degrees F. so that no bubbles are released to give away the sub's position.
''We know that our ships are quieter and can 'hear' better,'' that is, have better radar ''than the other guys,'' says Capt. David H. Boyd, an instructor at the US Naval War College in Newport, R.I. ''These are the two most important factors for a submarine.''
There is no shyness among submariners in advertising that their academic records and the rank and technical competence of their enlisted men are among the highest in the Navy.
Those in the US submarine force point out that although the submarine community of 33,000 men makes up little more than 7 percent of the Navy's 480, 000 uniformed personnel, they sail more than 35 percent of its combat ships. Standards are tougher here, too: One drug offense and you're off the sub.
How about the submarines' fighting prowess? The Falklands crisis provides some strong indications of this. Britain's nuclear attack subs were the first ships sent to the war zone. Though out of sight throughout the conflict, the subs were never out of mind. Reliable reports now indicate that the British might not have as many nuclear submarines in the area as reported to the press. It turns out that just the threat of a nuclear submarine served to bottle up the Argentinian fleet.
But what is it like to be on one for any length of time?
Some obvious questions come to mind: How do the men cope with the confinement , the lack of mobility, the boredom? How do they get along?
''We take a lot of professional pride in the work we do,'' says Lt. Comdr. William L. Stockho, executive officer on the attack submarine USS Haddock.
''When at sea it is an 18, rather than a 24-hour day. Six hours are spent at a duty station. The remaining 12 are set aside to repair equipment, study to qualify for operation of other systems on board, and'' - almost as an afterthought - ''eat and sleep,'' Commander Stockho said.
''With only 130 men on board it isn't long before everyone gets to know everyone else,'' said the executive officer, ''and you must have confidence in each man's ability to do his job. If you make a mistake on the surface, you can just float around until you fix it. If you make a mistake when you're 400 feet deep, well, it could be your last one.
''We take qualifying a man for a duty station very seriously. It's a one-on-one teaching situation, but in the final result no one gets passed who can't do the job. The people who are successful on submarines are good managers of their own time,'' he said.
''Making repairs on a submarine is like repairing a watch through the stem,'' says Rear Adm. Lawrence Burkhardt III, commander of Submarine Group 5 in San Diego. ''Our training qualifications are so high because the task demands it.''
Some of these tasks range from fire control, which everyone from the cook to the captain must learn, to weapons control, sonar, navigation, communication specialist, and nuclear engineer.
This is where onshore training comes in. At the Navy's submarine school in Groton, Conn., all new enlistees receive at least 12 weeks' training. At the San Diego Submarine Training Facility, sailors already in the fleet receive continuing instruction in all the major support systems on a sub as well as any new systems. A major new system is introduced almost every two years.
Every member of the crew will have been tested in a flood chamber. Every possible valve that could leak, every pipe that could burst, does in practice. Repairs must be made before the room fills with water. Each man is evaluated on his individual performance as well as his teamwork.
''There is always something to do, and everyone has an important role, everyone knows this,'' says Comdr. Gerald Davis, captain of the attack submarine USS Haddock. ''Seeing that the ratio of my 'non-quals' to 'quals' goes down (men unqualified to operate specific systems and those qualified) from what it was at the beginning of a sea patrol is one of my major responsibilities,'' he said. ''In a way, I run a floating school.
''The crew's morale is another important responsibility. Should a fire break out or the ship spring a leak, each man must know where the the hoses, ventilation fans, and valves are in any part of the ship. Everyone on board must know that everyone else is equal to the emergency,'' Commander Davis said.
One area of concern to skipper Davis is any bad news a man might receive while underway. Except for very extreme circumstances, a sub's position will not be compromised by coming to the surface and offloading a sailor.
''My mother still doesn't understand why I couldn't come to my father's funeral,'' he said, ''and I had been in the Navy 12 years. Many men tell me at the start of a sea patrol that they don't want to hear anything bad until just before we dock.''
Each man receives four 50-word radio messages from family or friends during his time at sea.
The most demanding job, outside of being commanding officer or executive officer, is that of nuclear-propulsion engineer. It takes a minimum of 2 1/2 years of training to become one. Not surprisingly, this is the job most sought after by the civilian sector, and the area where retention of personnel is most difficult.
When talking about US nuclear submarines, there are two separate classes of ships: fleet ballistic-missile (SSBN) and attack submarines (SSN). Each has very different missions.
According to most military planners, the United States's 33 ballistic-missile submarines are the most secure of its strategic triad for nuclear deterrence (the other two are land-based missiles and bombers).
Just one of these ships, called ''boomers,'' carries more than the equivalent of all the explosives used in combat in World War II. The new Ohio class Trident , the largest sub in the Navy's inventory, packs more explosive power in its 24 missiles (each with nine independently targeted nuclear warheads) than all the gunpowder expended in all the wars man has fought to date.
Looking for a ballistic missile sub, when it is determined to remain undetected, is an exercise in futility. To date, more than 2,000 ballistic missile patrols have gone undetected.
There is little or no possibility that a missile could be launched without authorization. Four separate keys, each with a different set of coded instructions, must be turned by four different men before a nuclear-tipped missile can be fired. Both the ship's captain and the weapons-control officer on duty act autonomously and receive separate code-written orders. (This is the only place in the Navy where a captain's orders can be refused without threat of court-martial.)
Nuclear attack submarines fit the more conventional cinematic image: They seek out and destroy enemy ships, including other enemy submarines. With the introduction of Harpoon cruise missiles to their inventory of torpedoes and mines, they have the capability to attack land targets with conventional or nuclear explosives.
A new role for them is to serve as antisubmarine escorts for aircraft carriers. It places a demand on a branch of the Navy that is used to going it alone. Submariners are concerned that contact with surface ships being escorted means someone else can be listening, and fixing on their positions as well.
Inertial guidance, satellite, and radio navigation systems provide precise information regarding a submarine's position. Communications systems on subs include two-way satellite connections and low-frequency receivers which allow radio reception under water.
At any given time, 70 to 90 submarines are at sea on patrol. Their missions and positions are highly classified information.
Yet this high-technology underwater world has its lighter side. Don't underestimate the importance of a properly running ice-cream machine. Food is taken very seriously by submariners and it is a rare skipper who takes his men out on a patrol without complete confidence that his ice-cream cones will not be used as drinking cups because the ice cream won't freeze.
At the start of each patrol, the 300-foot-long tubular-shaped attack subs must be crammed with enough food for the entire cruise. (Ballistic-missile subs and the new Ohio class Tridents are even bigger - 425 feet and 560 feet long, respectively.) ''It breaks down to about 480 pounds per day for a crew of 130 men,'' explained the information officer, Lt. Gene Eliot.
Unlike the movie ''Das Boot,'' in which one of the two heads on a Nazi U-boat is stacked with food, the SSN Haddock's seven heads are left free. ''But the men end up walking on some boxes of food for the first week or so,'' said Lieutenant Eliot. ''You more or less eat your way down.'' The first decks that are cleared of food are the crew's mess; the last are the bunking areas.
It takes planning to position the food so that a good variety is available at each layer. Otherwise, you may have three straight days of margarine followed by two days of tapioca pudding.
Keeping fit is also a problem. Room for exercise is at a premium. But after the ship has been at sea for a while, crew members naturally cut down to one or two meals a day and need only four hours of sleep per 18-hour shift.
''Privacy is always a problem,'' said Seaman Calvin. ''It's the one thing you really can't get enough of no matter how busy you are. When you're in your own bunk, that's your home and the other men know this and respect it.''
For the men on the SSN Haddock, berthing is a little more complicated. Their attack sub is smaller than the ballistic-missile ship Calvin is assigned to. There are only 79 bunks for 130 men. This results in using a bunk in shifts - ''hot racking,'' as it's called. Since at least one-third of the crew will always be on duty, there are always empty bunks.
Commander Davis has the biggest suite on board (the only single room). It's not even as large as a king-size mattress. Personal space declines with decline in rank.
Camaraderie is a given in such close quarters. Officers will sit at their single mess table and conduct most of the ship's affairs. Walking between two men having a conversation is normal.
Bob Schuelke, a former officer and nuclear engineer who left the Navy recollected: ''In any of the tours I made, there never was any time where we didn't get along, do our jobs, and have a real sense of accomplishment. My main reason for leaving the Navy was the burden such long separations were placing on my family. Otherwise, I enjoyed it and found myself challenged continually.''
Chief Warrant Officer Max Alexander has spent 5 1/2 years of his 21 years in the Navy under water. ''I came to subs from the surface community,'' he said. ''Let me tell you, the improvement in morale and technical competence stood out. Just let a cook prepare a meal that's good - or bad - and everyone knows it. I'd see the captain daily. On an aircraft carrier, with upwards of 5,000 men, you could go for an entire cruise and not see anybody with rank. And you never knew who prepared the food.''
''Pay helps morale too,'' said Admiral Burkhardt. ''The raises in the last two years have been good and our retention rates, especially among officers, show it.''
For commanding officers on submarines, top pay will be in the $35,000 to $40, 000 range. All submariners get at-sea bonus pay in addition to their regular wages.
But as Bob Schuelke says, ''How do you pay someone for all the time he's away from his home and family? You can't. They have to be down there for other reasons.''