Vertical Launch System (VLS)
One of the weaknesses of all U.S. attack submarines since the Permit-class boats hit the water has been the shortage of space for torpedo tubes and weapons stowage. For over thirty years, U.S. attack boats have always had four 21-inch/533mm torpedo tubes to deliver their weapons, and about twenty-two stowage positions to hold them inside the boat. This was not much of a problem so long as all that the boats had to fire were heavy torpedoes and the occasional SUBROC. But beginning in the late 1970s with the introduction of the UGM-84 Harpoon antishipping missile, and the early 1980s with the UGM-109 Tomahawk missile series, this began to pose a real problem for submarine planners and skippers.
For example, say a U.S. sub skipper wants to shoot Harpoon missiles at a surface warship. Submariners traditionally prefer to keep at least one torpedo in a tube as a just-in-case weapon, much as a police officer keeps a hideout weapon in an ankle holster. This means the maximum salvo size that can be fired at the target ship is three Harpoons. This might be fine, but against a target like a Kirov-class battle cruiser with all its antimissile systems, those three missiles will be soaked up like water into a sponge; the weapons will be wasted, and the target will be alerted to the presence of the sub. What clearly is needed is a way to stow more weapons on the boat and fire more of them at one time.
The twelve hydraulically operated doors of the Miami’s vertical launch system for Tomahawk cruise missiles. JOHN D. GRESHAM
Some of the maze of hydraulic plumbing necessary to operate Miami’s vertical launch system (VLS). Note the handles for the various manual backups. JOHN D. GRESHAM
The designers of the Los Angeles-class boats anticipated this, because both the designs for Harpoon and Tomahawk were known at that time. Space was left in the forward ballast tank for twelve Vertical Launch System (VLS) tubes, each capable of storing and launching a Tomahawk cruise missile. In addition, space for the associated control and hydraulic systems necessary to operate the VLS system was left in a compartment forward of the torpedo room. Thus it was possible for a Los Angeles-class boat to carry and launch twelve additional cruise missiles without affecting the weapons stowed and fired out of the boat’s torpedo room. This meant an increase of 50 percent in weapons stowage and a 400 percent increase in ready firepower (when firing cruise missiles) over a non-VLS sub.
This change was not made immediately, however. Even though all the Los Angeles-class boats were capable of being fitted with the VLS system, the first boat to be so equipped was the USS Providence (SSN-719). And, because of budget constraints, it is quite unlikely that any of the earlier Flight I boats will ever be retrofitted with VLS missile tubes. Nevertheless, by the time the class is finished building, some thirty-one Flight II and 688I boats will have the system, providing room for some 372 Tomahawk missiles in the fleet. And that is a lot of firepower. By the way, it is easy to make out which boats have the VLS and which don’t by whether they are level in the water (VLS equipped) or nose up (non-VLS Flight I).
Enlisted mess area, USS Miami. Here the crew cooks, eats, does laundry, takes classes, and watches movies. JACK RYAN ENTERPRISES, LTD.
The way the VLS system works is quite simple. The missile canisters are loaded vertically from a crane. Each canister contains a complete all-up Tomahawk round, ready to fire. At the top of each canister is a thin membrane of clear plastic, which keeps the missile dry and safe. This is how it stays until the time to fire. The boat comes to launch depth, usually about 60 feet, and reduces speed, say 3 to 5 knots, perhaps raising a communications mast to get additional targeting or a navigational fix from the GPS satellite constellation. Once the flight instructions have been programmed into the desired missile(s), the launch system automatically begins the firing sequence.
The system opens the missile launch tube hatch hydraulically and an explosive charge propels the missile up through the plastic membrane and into the water. After the missile travels up about 25 feet the booster rocket fires, thrusting the Tomahawk out of the water. At this point the missile tilts over, drops the burned-out booster motor, lights the turbojet engine, and heads for its preprogrammed target. Meanwhile the launch tube fills with water (helping to compensate for the lost weight of the missile), and the hydraulic hatch is closed.
The VLS system is causing a revolution in design of new weapons for submarines. It has radically increased both the firepower and stowed weapons load for the U.S. submarine force—all at no increase in the size or displacement of the basic Los Angeles design.
Living Spaces
On the Miami’s second level is the bulk of the living space aboard the boat. If you stand aft near the forward escape trunk, then you walk forward, you will find the largest open area on the boat, the enlisted mess area. This place is a combination of cafeteria, schoolroom, movie theater, game room, and almost anything else that involves gathering the boat’s enlisted population together. Here are six tables with bench seats on both sides so that something like forty-eight sailors at a time, about half the Miami’s population, can sit down at once. Along the starboard bulkhead are such cherished pieces of equipment as the soda machines (no longer do they serve the hated “Yogi” cola), milk dispenser, soft ice cream machine, and that most cherished of Navy wardroom icons, the bug juice dispenser. By the way, well-informed palates suggest that the red flavor is best, but stay away from the orange! Strangely, it also makes an excellent scouring powder for cleaning floors and heads (all that acid in it, they tell me). Back near the escape trunk is the ship’s laundry. About the size of a phone booth, it handles the laundry for the entire boat, with a washer and dryer that would seem small in most apartments.
Adjacent to the enlisted mess area is the galley. Inside a room about the size of an apartment kitchen, the meals (four per day) are prepared for over 130 officers and men. It’s amazing that so much can be done in such a small space. There are all the usual institutional kitchen fixtures (electric mixer, oven, grill, and stewing pots), as well as a pair of refrigerated spaces for food storage. Usually one of these is set up as a deep freeze, the other as a fresh food refrigerator, though for longer patrols fresh food is avoided, and only frozen and dry stores are carried. It is a matter of record that the single most limiting factor to SSN operations is the quantity of food and other consumables. Before a long deployment, virtually every spare nook and cranny is packed with stores—food, soap, paper for the copy machines, dry stores, and, of course, most vital of commodities on board a sub, coffee.
A mess technician cooking lunch in the galley, USS Miami. JOHN D. GRESHAM
Moving forward on the port side passageway, you encounter the berthing spaces for the enlisted personnel. I should say here that if you have a touch of claustrophobia, this is where it will manifest itself. The three-tall bunks are roughly 6 feet long, 3 feet wide, and 2 feet tall: about the size of a coffin. Each bunk has a comfortable foam rubber mattress with bedding, a light for reading, a blower for fresh air, and a curtain for privacy. All your personal gear goes into lockers on the walls, or the 6-inch-deep trays under the bunks. For the enlisted personnel, this is the total extent of their privacy. This is even further limited, as about 40 percent of the enlisted population has to share, or “hot bunk,” their sleeping accommodations. This is because the 688I design just did not have enough room to provide a bunk for each enlisted man. This means that groups of three enlisted men have to share two bunks, with the sleep periods (they sleep in six-hour shifts) rigidly scheduled in advance.
Miami’s chief of the boat (COB) shows off the three-high bunks in the “goat locker.” Each bunk is about the size of a coffin! JOHN D. GRESHAM
On the starboard side of the boat are the berthing and mess spaces for the senior enlisted personnel, generously known as the “goat locker.” Here there is a small seating area about the size of a corner booth at a restaurant, which serves as eating area, office, and conference room for the chief petty officers. Heading aft from here is another aisle of three-high bunks, though these
are reserved for each man.
For the officers there is a separate wardroom for eating, studying, and doing paperwork. It is a nicely appointed area with its own pantry for coffee and snacks around the clock. In the middle of the space is a single table that serves as dining table, desk, and conference table. Unlike the commander of almost any other ship in the Navy, the commanding officer does not have a separate pantry to take his meals. He sits with his officers at every meal, giving it the feeling of a family gathering. The submarine service has always been more informal than the surface forces, and this is part of the esprit that makes the “bubbleheads” different from the rest. Commander Jones runs a “loose” wardroom where kidding and friendly ribbing is always welcome. He makes no secret of his love of good seafood, and is a big fan of ice cream. In fact, he is fond of saying that other than having the only private stateroom on the boat, his only command privilege on the Miami is choosing the flavor of ice cream for the machine in the galley. He chooses a rather diplomatic French vanilla flavor.
Officers’ wardroom, USS Miami. JOHN D. GRESHAM
The commanding officer of USS Miami, Commander Houston K. Jones, USN, conducting business in his stateroom. OFFICIAL U.S. NAVY PHOTO
As for the commander’s cabin, it is hardly the stuff you might find on the Queen Elizabeth II. Located just forward of the enlisted mess, on the second level, it is roughly 10 feet long by 8 feet wide. It is dominated by a combination desk/closet unit in the after portion of the cabin. Against the outside bulkhead is a pair of seats with a small table between them; this unit folds down into the bunk. Commander Jones is proud of saying that it’s the best bunk on the boat, and certainly it is the only one that does not have another bunk above and/or below it! On the door to his cabin are three notices. One reads KNOCK AND ENTER and another is, THINK QUIET! IT’S OUR BUSINESS . . . IT COULD BE OUR LIVES. The final one is a copy of Rudyard Kipling’s famous poem, “If,” not a bad philosophy to advertise if you are in charge of 132 lives and $800 million of the taxpayers’ money.
The commander’s desk contains a variety of different manuals, a safe for classified documents, and various communications devices to keep him in touch with the rest of the boat. One of the newest pieces of equipment to be added is known as a multifunction display, mounted adjacent to his bunk. This marvelous device, which is tied into the BSY-1 combat system, is a red gas-plasma display showing data on position, course, speed, heading, and depth, as well as modes to show the current tactical situation around the boat. The advantage to Commander Jones is that he can wake for a moment in the middle of the night, reach over and check the boat’s status, then roll over and go back to sleep—all without having to ruin his night vision by turning on a light or having to pick up a phone and talk to the OOD. He figures that not having to wake up fully several times is worth several hours’ more sleep. And that can be life and death for the boat in a combat situation. A total of eight of these devices are located around the boat in such places as the control room and sonar room.
The communications and recreational equipment in the captain’s cabin. JOHN D. GRESHAM
The Engine—The Reactor/Maneuvering Spaces
If you wander aft from the enlisted mess, past the forward escape trunk and down half a deck, you find the great divide on the Miami. This is the entrance to the tunnel aft to the propulsion spaces containing the S6G nuclear reactor (built by General Electric) and the main engineering spaces. It is marked by a number of different warning signs from the DNR, ranging from information on possible radiation hazards, to security notices about just who on the boat is allowed aft of this point. It should be noted that no member of the media, including myself, has ever actually seen an actual nuclear submarine reactor compartment or her engineering spaces. Nevertheless there are a number of things that we do know about these areas, and I will try to share them with you.
The first thing to understand about the nuclear reactor on a submarine is that it has only one real purpose, to generate heat to boil water into saturated steam. Other than that, all of the other parts of a nuclear submarine propulsion system are similar to any other type of steam-powered turbine plant. Its advantage over an oil-fired steam plant is the amount of energy concentrated in the nuclear fuel in the reactor core, as well as the complete lack of any need for air. On a weight and volume basis, nuclear fuel, such as enriched uranium, has several million times the amount of stored heat of a comparable amount of fuel oil. This concentration of energy is what makes all the dangers of handling nuclear fuel worth the trouble. In addition, because of the efficiency of the nuclear “fire,” it is possible to build boiler plants that are considerably smaller than comparable oil-fired plants.
The process of nuclear fission is essentially quite simple. Imagine a floor covered with mousetraps. Each mousetrap has, mounted on the striker arm, two Ping-Pong balls. If we imagine a uranium atom as a mousetrap, it is holding on to a pair of attached particles called neutrons much like the Ping-Pong balls. Now if you drop another Ping-Pong ball onto one of the traps and trip it, two balls will fly into the air. This represents what happens when a neutron enters the uranium atom and strikes the nucleus: the atom splits and releases the two neutrons, releasing energy as heat. And when those two fall onto two more traps, these will trip and each throw two more Ping-Pong balls skyward. This will continue to double and double again until all the traps fire off their balls in one final fusillade. This same principle, whereby neutrons strike more and more atoms until all of them finally split, is called an uncontrolled or supercritical fission reaction. And this is what happens when an atomic bomb detonates.
Entry to the tunnel leading to the propulsion spaces, USS Miami. JOHN D. GRESHAM
But we don’t desire an explosion, we want a slower reaction like a fire in a boiler. Imagine that in our room of mousetraps and Ping-Pong balls, we hang some monkeys from the ceiling. And we train them to grab one out of every two Ping-Pong balls when a trap goes off. This would allow the series of tripping traps to go on for a much longer time. And this is exactly what happens in a nuclear reactor. Instead of monkeys, a reactor uses what are called control rods (made of a neutron-absorbing material like cadmium or hafnium) set to absorb exactly the right amount of neutrons to bring the reaction into controlled or critical fission. This reaction still generates a great deal of heat, which is used to boil water into saturated steam to power the sub’s turbines. In this way the same nuclear fuel that can cause a nuclear explosion in an instant can be used to power a ship for a period of years. And because of design procedures that have been tested over a period of decades, the fuel in the reactor cannot explode or even come close to doing so. The DNR takes great pride in the safety record of the boats with U.S.-designed reactor plants, which is perfect.
Most of the heat in the reactor is collected into what is known as the primary coolant loop. This is a series of pipes passing an extremely pure water-based coolant through the core of the reactor. This heat is passed through a heat exchanger to what is called the secondary loop. This is where the water for the steam turbine is actually boiled. Now, the steam created here is not the stuff you get from the tea kettle on your stove. This steam, which is under high pressure, is heated to literally hundreds of degrees and contains a great deal of motive energy. And this is the stuff that turns the turbine blades of the main engines, which feed into the reduction gears, which turn the propeller shaft and the propeller. Quite simple, really!
There are a few small problems with this system, though, and we need to discuss them. The obvious one is the question of how to protect the men aboard from the harmful effects of the reactor’s radiation. As we mentioned before, the early Soviet nuclear boats scrimped on shielding and became cancer incubators for the naval hospitals of that now-defunct nation. The answer, in a word, is shielding. The entire structure surrounding the reactor compartment is layered with a variety of different shielding materials.
Between the reactor compartment and the forward part of the boat is a
huge tank of diesel fuel, which powers the big Fairbanks-Morse auxiliary engine in the machinery compartment. As it turns out, that fuel is extremely efficient at modulating or absorbing the various subatomic particles that could damage human tissues. In addition, the entire reactor is contained inside a reactor vessel that looks like an oversized cold capsule on end. Surrounding this vessel, as well as inside of it, is a system of layered shielding. While the materials actually used are classified, it is easy to deduce that lead (an excellent gamma ray absorber) and chemically treated plastics (based on fossil fuels) are probably used extensively.
In addition to its extensive shielding, the entire reactor plant has been overengineered. Since its earliest beginnings, the DNR has insisted that naval reactors be built with extremely high safety margins. While DNR will not comment, for example, upon just how much pressure all of the reactor plumbing can take, it is generally acknowledged that the entire reactor plant has been built several hundred percent more robustly than is required (400 percent to 600 percent has been mentioned). In addition, every system has at least one backup and usually an extra manual backup on top of that. The legacy of the Thresher loss is this fanatical obsession with safety.
Another area of extreme secrecy is the exact configuration and design of the reactor core itself. In fact, other than the technology used to reduce radiated noise, nothing on the Miami is as sensitive as the power plant core. This probably consists of a series of uranium fuel elements formed into plates to allow maximum heat transfer to the primary coolant loop. The fuel elements are probably mounted parallel to each other in a fuel assembly mounted atop a support structure in the base of the reactor vessel. The fuel used is highly enriched Uranium-235, probably 90 percent pure U-235 or better. For those who might wonder, the fuel used in commercial nuclear power generation plants runs about 2 percent to 5 percent pure, and the material used in nuclear weapons is about 98 percent pure. In between each fuel element is room for a control rod (also in the form of a plate and made of a neutron modulator), to control the rate of nuclear fission. Each rod is designed to drop automatically into place between two fuel elements in the event of a reactor problem, thus quenching the nuclear reaction. In addition, a procedure called scram allows the crew or the automated monitoring systems to shut down the reactor immediately, and restart it later if conditions allow.