The Sounds of Silence — Acoustic Isolation
Silence. That is what has made American boats better than their opponents for over thirty years. It is their armor and their cloak all wrapped up into one vital quality. Nevertheless it comes at a high price and is called a fragile technology-fragile because it is based upon well-understood principles of physics, and because it can be compromised so easily. In terms of military technology, it is one of the crown jewels, in the same category as the ability to build stealth aircraft and nuclear weapons. So effective has this silencing effort been that the latest U.S. SSNs and SSBNs are so quiet, they can effectively disappear in the ocean's background noise.
To make a quiet submarine, the naval architects must take a holistic attitude to the design of the boat and every piece of equipment that goes into it. The key is mounting each piece of equipment that moves or makes noise on something that damps out the vibrations. The transmission of these vibrations-things like the spinning of a pump or the hum of a generator-sends noise out into the hull, where it is radiated into the water. In addition, the rubber decoupling tiles coating the hull help keep noise inside the hull from being transmitted out into the water.
The mounts on the main machinery raft take care of the biggest source of radiated noise. The rest of it is probably taken care of by secondary mounts underneath each piece of equipment (pumps, turbines, etc.), designed to attenuate the specific type of noise generated by that particular piece of equipment. In addition, each piece of machinery is probably designed to be as smooth running and noiseless as America's best mechanical and electrical engineers can make it. For example, the seawater circulation pumps, which are arguably the most noisy devices on the boat, transmit almost no noise in the 688I-class boats. Supporting this is a noise-monitoring system with sensors throughout the boat designed to tell if any piece of equipment or gear is loose or malfunctioning. An added benefit of this system is that it probably is capable of predicting when and how a piece of machinery is going to fail by its acoustic signature (such as the sound of bearings wearing out).
The various techniques used to decrease the radiated noise of American submarines constitute the single most classified aspect of the Miami and her sisters. The above description is only the most cursory discussion possible of this incredible technology. In fact, the only real way to describe the magnitude of the achievement is to say that the S6G reactor generates something like 35,000 shaft horsepower[10], yet with all this power the total noise radiated by the Miami is probably something less than the energy given off by a 20-watt lightbulb. It is for this reason that submariners sometimes refer to their Air Force cousins flying the F-117A stealth fighter as 'the junior stealth service.'
So, you ask, what is it like to live aboard a submarine like Miami? Well, imagine a combination of living in an oversized motor home and summer camp, and this is a lot of what life in the 33-foot pressure hull is like. Not much room, very little noise, very little news from home, and virtually no privacy. Against these 'downs' are the esprit de corps of the submarine force, and the knowledge that being a submariner truly makes a man the best of the best in the U.S. Navy.
If you were to go out on a cruise on Miami, the very first thing you probably would notice is that you seem to be bumping into everything and everyone on the boat. This is not unusual for someone new on a sub, and after just a few hours you begin to 'think small and thin' so that you can smoothly move around your fellow submariners.
The next thing that comes to your attention will probably be the rather odd working schedule, a watch program that has a crewman working six hours 'on' and twelve hours 'off.' While he is 'on,' a sailor is standing watch; while 'off,' he is eating and sleeping, doing maintenance on equipment and systems, and studying for qualification. This creates the unusual standard of a Miami 'day' being eighteen hours rather than twenty-four. Unfortunately the entire boat takes on this schedule, which tends to lead rapidly to crew members' suffering from sleep deprivation. While in theory a crew member is allowed eight hours of 'off' time in a given twenty-four-hour period, this rarely works out into long periods for sleeping. Very quickly one loses all sense of time on the surface and back home, and the sleep that one does get tends to be 'on the fly.'
The main crew mess area, USS Miami. Here one of the chiefs is conducting a briefing as part of the continuing 'school of the boat.' JOHN D. GRESHAM As for sleeping itself, this is a relatively comfortable thing to do on Miami. With the exception of Commander Jones's stateroom, the bunks for all the officers and men are about the same size, with similar appointments. And while a berthing space is about the same size as a big coffin, once you learn to think small, the space seems quite roomy. With fresh air blowing on your face and a nice foam mattress, falling asleep is really not much of a problem.
What is a problem is the 'hot bunking' required for a large portion of the enlisted personnel on the Miami. This tends to dominate the schedules of the junior enlisted crew members, with a rigidly set schedule for many of the berthing spaces. If 'special' or extra personnel have to be aboard, the crew will lay out extra bunks in the torpedo room over the weapons stowage racks. These are actually quite comfortable, with good headroom, though some folks find the idea of sleeping in a room with literally tons of explosive and fuel rather discomforting. Another problem is the lack of personal stowage space. For those with their own bunks there is a 6-inch-deep stowage pan under each mattress, as well as some locker space. For those having to 'hot bunk,' three men have to share the space normally allotted to two.
A typical bunk space or rack in the forward enlisted berthing area. These are stacked three high, and frequently two of these will be shared by three men in a scheme called 'hot bunking.' JOHN D. GRESHAM Dining aboard Miami is truly a pleasure, as the Navy goes all out to give the men the best chow the taxpayers' money can buy. In fact, because of the limited room for exercise, many of the men actually tend to gain weight on cruise. The food itself is simple but wholesome, with fresh fruit and vegetables becoming the most prized items after a few weeks. The Navy has done some rather clever things to extend the storage life of much of the fresh food aboard. For example, eggs are specially treated with a wax coating to extend their shelf life.
The cooks and their helpers (everyone does an occasional stint of mess duty) work hard to vary the menu and make meals interesting, using a galley about the size of an apartment kitchen. Certainly the culinary highlight of a cruise is the traditional halfway meal of 'surf and turf' (steak and crab legs). Unfortunately, by the last few weeks of the cruise every man aboard will be sick of three-bean salad, and dreaming about fresh veggies almost as much as he does about his family.
Those dreams of home and family are always at the center of the submariners' thoughts, though there is very little the Navy can do to give them the kind of communications home that sailors aboard a carrier or frigate might have. The stealth of the modern SSN means that the crew of the Miami is almost never allowed to send personal messages home, and news from home is heavily limited and censored. Word from home is limited to a series (about one a week while on patrol) of forty-word messages called 'Familygrams.' Each Familygram is carefully crafted by a wife, parent, or loved one to give the crewman at sea an idea of what is happening at home. An example of a notional Familygram is seen below:
421. DOE LTJG 5/14: REMEMBERED MOTHERS-FLOWERS BEAUTIFUL-THANK YOU. GREAT NEWS. IN CHARGE SUMMER CAMP PROGRAM. THIRTY KIDS. STARTS 24TH. BOUGHT SWIMMING POOL JOHN JR. B ALGEBRA SEMESTER. NO TIME FOR GARDENING, CERAMICS. MONEY FINE-FEW BILLS. SAVING FOR VACATION.
