Notional drawing of the layout of a nuclear submarine propulsion plant. JACK RYAN ENTERPRISES, LTD.
Around the core circulates the coolant of the primary loop, which feeds the heated coolant into a steam generator. The steam generator directs its steam into a secondary cooling loop, which feeds a pair of high-pressure turbines in the machinery spaces, where the steam is condensed back into water and fed back into the steam generator. The turbines feed into a massive set of gears known as reduction gears, which turn the main propeller shaft. In addition, some of the steam is used to turn several smaller turbines that provide electrical power to the boat and its various pieces of machinery.
It may come as a surprise that other than the transit tunnel aft to the main machinery space, the reactor is not manned. The DNR limits the time a man can stay in proximity to the reactor, even how long he might stay in the transit tunnel. The actual control area for the reactor plant and the turbines, called Maneuvering, is located aft in the engine room. While it has never been shown to the press, it probably follows the convention of commercial power plants, with the controls laid out over a block diagram of the reactor/turbine system. This panel is manned at all times, even when the boat is in port and the reactor is shut down (noncritical).
The dominating feature of the machinery space is the deck, or more correctly, the mounting for all of the machinery. While it may seem solid enough, it is in fact a large platform or “raft,” which is suspended on mounts on the inside of the hull. The mounts use at least one, probably two, sets of noise isolation mounts. These are like oversized shock absorbers designed to reduce the vibrations of the larger pieces of engine room machinery. The purpose of a raft is to take the noisiest things on the boat and isolate them from the hull, which radiates noise like a speaker into the water.
Mounted on the raft are the two main engines, the boat’s electrical turbine generators, and the supporting pumps and equipment associated with moving the boat. Proceeding aft, you see the main propeller shaft leading back to the main packing seals in the stern. In addition there are a number of workbenches, as well as a limited machine shop capable of supporting many small-scale repairs. The size of the main gear, called a bull gear, would preclude repair, but virtually every other contingency in the space could be handled by the engineering team. These crew members, by the way, are recognizable by the different types of radiation monitoring devices they wear. Unlike the film badges worn by those who live and work forward of the reactor, these personnel wear a small dosimeter (which looks like a tiny flashlight), so that any dosage of radiation they receive can be assessed immediately.
To get the power plant started, the engineering officer of the watch orders the personnel at the reactor control panel to retract the control rods to a known position. This allows the core to heat up, causing the coolant to generate steam in the steam generator. From here the turbines are set turning, and so too the reduction gear train. There is a popular notion that the speed of the boat is increased by just retracting the control rods farther from the reactor core. This, in fact, is exactly the converse of what actually happens; the rods are simply retracted to a fixed point and held there. The engineers’ main goal is to bring the reactor into equilibrium so that the basic amount of heat going into the primary coolant loop is constant. One can then control the speed of the boat by simply tapping more steam from the steam generator, thereby increasing the steam supply to the turbines. This results in cooling the primary coolant loop more, thus increasing the efficiency of the nuclear reaction, feeding more heat to the steam generator, and increasing the speed of the boat.
Conversely, stemming the flow of steam to the turbines not only slows down the spinning of the turbines, it also takes less heat from the primary coolant loop, and rapidly drops the efficiency of the nuclear reaction, “cooling” it down.
Life Support and Backup Systems
The auxiliary machinery space down on the third level aft of the torpedo room is arguably the most important compartment on Miami. Here is located all of the life support equipment, as well as the auxiliary power source. As you enter the space and head down the starboard aisle, you are given a quick introduction to “Clyde,” the big auxiliary diesel engine. This is an old favorite of the chiefs onboard, because it is a direct link with the old World War II fleet boats. Built by Fairbanks-Morse, the design dates back to the 1930s and is a scaled-down version of the model used to power all of our submarines during the war. It is reliable and the crew loves it, therefore the name Clyde, as in, “. . . right turn, Clyde!”
While some folks might wonder why such a dinosaur would be on one of the most advanced submarines, remember that not everything always works properly, including nuclear reactors. For example, what would happen if Miami was at sea and needed to scram the reactor plant? Restarting a reactor takes a lot of power, and while there is a large bank of batteries underneath the torpedo room, it might not prove adequate to completely restart a cold S6G plant. Thus the Fairbanks-Morse engine can provide, through a generator turned by the diesel, enough continuous power to get the tea kettle running again. It has other uses, too. In the event of a reactor casualty, the diesel provides the means for getting home. In that event, the captain orders the engineers aft to lower a small electric outboard motor, which is recessed in the lower hull aft, into the water to provide motive power to get home or to get help.
The diesel engine also has a role in firefighting onboard that might surprise some folks. In the event of a fire, one of the first things the captain might do (assuming this is not in a combat situation) is to surface and start up the diesel. This is because the diesel draws its air from within the boat, and thus it would suck up any air being polluted by the fire. Opening just the fairwater hatches from the control room will completely change the air in the boat in a matter of minutes.
This space is also where the air is made or, more properly, maintained. Several different pieces of equipment in the auxiliary machinery space help to provide the clean, fresh air that can be found onboard. First are the carbon dioxide (CO2) scrubbers. CO2 is the gas given off by humans when they breathe and is dangerous when the concentration gets too high. The Miami utilizes a chemical scrubber to remove it from the air. The chemical absorbs CO2 when it is cool and releases it when it is warmed. In addition, CO and H2 “burners” remove the carbon monoxide and hydrogen gas generated by equipment as well as by cigarette smoking, which is allowed onboard. Finally, filters and dehumidifiers clean the air and help keep it “friendly” not only for the crew but also for the many pieces of equipment—especially electronic—on the Miami. In case a fire or some other emergency contaminates the onboard air, a force-fed air supply called the Emergency Air Breathing (EAB) system has attachment points throughout the boat, allowing crewmen with breathing masks to plug in to it and continue their duties.
Other life support equipment includes a device that takes water and electrically “cracks” it into its base elements of hydrogen and oxygen. The oxygen is retained in tanks and released into the boat’s atmosphere automatically by the environmental control system, and the hydrogen is vented off the ship from a small port in the aft edge of the fairwater. There is a fresh-water distillation plant that produces something over 10,000 gallons/38,000 liters of fresh water a day. Most of the water is used for drinking, cleaning, cooking, and personal hygiene. Very little water is usually required for the power plant (for charging the cooling loops and steam generators), but the reserve tanks are usually maintained near full “just in case.” It should be said that the obsession with water conservation is mostly for contingency purposes. Most COs like to have full tanks of water before they enter a tactical situation, just in case they need to shut down the distillation plant to keep noise down. And from what I hear, some boats just choose to run the distillation plant full-time and let the crew have as much shower time as they want, particularly during runs home. On a normal day aboard Miami, the majority of the water produced would go to crew habitability.
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Weapons—Torpedoes, Missiles, and Mines
While submarines are useful for covert actions like intelligence gathering and landing special operations forces, it is the threat of what they can do with their weapons that can cause so much fear and respect in an adversary. Ever since Sergeant Ezra Lee tried to sink HMS Eagle in Boston harbor back in 1776, just the potential threat of harm from a submarine has been enough to make an enemy stop and consider whether he should move his ships against you. Today the weapons can hit a wider variety of targets, and they have become even more deadly.
Torpedoes
The torpedo is the traditional weapon of the submarine, and the torpedoes that equip the U.S. SSNs today are truly awesome. For some years now, the U.S. standard torpedo has been the Mark (Mk) 48. This weapon, which first appeared in 1971, has gone through a series of different upgrades, culminating in the Modification (Mod) 4 version, which appeared in 1985. This version, designed as an intermediate upgrade to the next major version, allows for the greater speeds and deeper diving depths of the newer Soviet subs that were appearing at the time. As this book is written, about half the torpedoes being loaded aboard U.S. subs are Mk 48 Mod 4s.
Cutaway view of a Mark 48 advanced capability (ADCAP) torpedo. JACK RYAN ENTERPRISES, LTD.
The business end of a Mark 48 ADCAP torpedo. The black cover is the acoustic “window” of the torpedo’s seeker head. JOHN D. GRESHAM
A recent addition is known as the Mk 48 Advanced Capability (ADCAP) torpedo. Manufactured by Hughes, the ADCAP takes the basic Mk 48 package and adds the following new features:• A bigger fuel tank that provides for a 50 percent increase in range (about 50,000 yards), and a speed of 60+ knots.
• A new data send/receive module, which packs 10 miles of guidance wire into the aft end of the torpedo and 10 more miles into the dispenser in the tube. This allows the submarine to clear the launch point and still guide the weapon.
• A new combination seeker head/computer that uses electronically steered sonar beams to guide the weapon to the target. Earlier versions of the Mk 48 (like the Mod 4) used to have to “snake” about their course to search effectively for a target. The head allows the torpedo to see almost all the 180-degree hemisphere ahead of the weapon. The computer controlling the whole system is designed to make the ADCAP the world’s “smartest” torpedo.
Tail section of an Mk 48 ADCAP torpedo. Inside the cover (labeled No Step) is the pumpjet propulsor, and a dispenser for ten miles of guidance wire. The silver unit behind it, which stays in the tube, contains another ten miles of wire. JOHN D. GRESHAM
The back end of an R/UGM-84D Harpoon antiship missile. The locked cover, which protects the guidance fins, is removed prior to loading. JOHN D. GRESHAM
With ADCAP, the submarine force arguably has the finest torpedo in the world. Not only is it fast, deep diving, and maneuverable, but it has a big warhead (650 lb/295 kg of PBXN-103 explosive) with an active electromagnetic fuse that allows the weapon to be detonated precisely where it will do the most damage. And it has more “brains” than any other torpedo, with an amazing ability to outsmart countermeasures and jamming, as well as the capability to feed seeker-head data back to the BSY-1 system on Miami. This allows the fire control technicians to use the ADCAP as an offboard sensor. With such capabilities as these, it’s no wonder that the crew of Miami calls the ADCAPs in her racks “wish me dead” torpedoes.
Missiles
Strange as it may sound, the nuclear submarines of the U.S. Navy operated for over twenty years without a dedicated weapon for attacking surface ships. Part of the reason was the ASW focus of the SSN force during the 1960s and 1970s. Also, for much of that time their primary targets, the surface ships of the USSR, had no long-range weapons that could attack a sub while it was submerged. But with Soviet deployment of their first sea-based ASW helicopters and the ship-launched SS-N-14 Silex ASW missile, there was a clear need for a weapon that would allow a boat to stand off farther than the ten to fifteen miles a torpedo shot would allow. It had to be launched from a torpedo tube and carried as an all-up or “wooden” round, requiring no maintenance and a minimum of support.
Cutaway view of an R/UGM-84D Harpoon antiship missile. JACK RYAN ENTERPRISES, LTD.
Encapsulated UGM-84 surface-to-surface Harpoon antiship missile leaving the capsule as it clears the surface of the water. OFFICIAL U.S. NAVY PHOTO
The weapon that was produced was the McDonnell Douglas A/R/UGM-84 Harpoon. This missile, which can be launched by ships, subs, and aircraft, was originally developed to allow patrol aircraft to shoot at Russian cruise missile subs on the surface. First deployed in 1977, it is approximately 17 feet/5.2 meters long, weighs about 1,650 lb/750 kg, and carries a 488-lb/222-kg high-explosive warhead. It utilizes a radar seeker that looks for surface targets and then initiates an attack “endgame” on the target. Packaged inside a buoyant, torpedo-shaped launch capsule, it is fired from one of the normal torpedo tubes and rises to the surface. When it reaches the surface, the nose of the capsule is ejected, and the missile is launched into the air by a small rocket booster. Once airborne, the booster is dropped, an engine inlet cover is ejected, and the small turbojet engine is ignited. The missile then descends to about 100 feet above the surface, and transits to the area of the target ship at a speed of about 550 knots.
The Harpoon can be launched in a variety of modes. These include what is known as Bearing Only Launch (BOL), in which only the bearing to the target is known. There is also a series known as Range and Bearing Launch (RBL) modes, which require both range and bearing. Depending on the range to the target and the amount of neutral shipping in the area, the seeker can be set to RBL-L (Large) for open ocean situations, or RBL-S (Small) for tight, short-range situations. If necessary, several doglegs or waypoints can be programmed into the Harpoon’s Midcourse Guidance Unit (MGU), which utilizes a small strapdown inertial guidance system to keep the missile on course. For submarines, there is even a self-defense option that allows the defending SSN to shoot the Harpoon “over the shoulder” into a charging surface ship.
Once the missile gets to the target area, the seeker is switched on and begins to search an area shaped much like a piece of pie. If the seeker radar locates a suitable target, the onboard computer does a quick test to make sure it is a valid target (not a wave or a whale), and begins the endgame. The missile descends to an altitude between 5 and 20 feet (depending on the height of the waves) and heads for the target. At the discretion of the Miami’s fire control technicians, the missile can be programmed to run straight into the side of the target ship (just a few feet above the waterline), or an optional “pop-up” maneuver can be selected to make the missile plunge deep into the middle of the ship.
In any case, the exploding warhead will tear much of the guts out of any ship up to cruiser size. In addition, any of the jet fuel not used by the missile’s turbojet will add to the destruction aboard the target vessel. It is a little-known fact that the warhead of the Exocet missile that sank HMS Sheffield in 1982 failed to detonate, but the residual rocket fuel in the missile’s motor caused enough of a fire to eventually sink the ship.
The latest version of Harpoon aboard the Miami is the UGM-84D, which uses a denser fuel mixture to give it more range (reportedly around 150 NM/250 km). All in all, with some eighteen different countries using it, Harpoon is one of the most successful missile programs ever run by the U.S. Navy.
After the ADCAP, no weapon has done more to make the Miami deadly and effective than the UGM-109 Tomahawk cruise missile. Tomahawk is an outgrowth of a loophole that was discovered after the signing of the SALT I arms limitation treaty in 1972. While the exact origin of the cruise missile program is debated, it is generally assumed that Henry Kissinger, then the National Security Advisor, asked the Department of Defense (DoD) to look for classes of nuclear weapons that had not been considered during the SALT I negotiations. After some study, the DoD systems analysts came to the startling conclusion that air-breathing cruise mi
ssiles, basically cheap pilotless aircraft with nuclear warheads, would make an excellent weapon to circumvent the terms of the SALT I agreement. They could be launched from ground vehicles, aircraft, ships, and submarines, would be extremely accurate, and would be quite difficult to detect and intercept.
Target damaged by a Harpoon missile impact. OFFICIAL U.S. NAVY PHOTO
As a result of these studies, a joint project office to develop cruise missile components was started by the U.S. Navy and U.S. Air Force. While both services wound up choosing different models of missile (the Air Force selected a model built by Boeing), most of the components such as engines, warheads, and guidance systems were of a common design. The winner of the Navy competition was the B/UGM-109 model developed by General Dynamics. McDonnell Douglas is the second-source contractor for the missile, called Tomahawk.