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SLBM-The Navy's Contribution to Triad
Lieutenant Colonel William D. Siuru, Jr.

TODAY, the strategic deterrence policy of the United States is based on Triad, with dependence on its three elements - intercontinental ballistic missiles (ICBM), strategic bombers, and submarine-launched ballistic missiles (SLBM). There have been volumes written on Triad, explaining its merits and deficiencies, but its key attributes can be outlined quite simply. Each of the three Triad components contributes three quite different threats to the Soviet Union as a result of their individual operating environments, technical characteristics, and modes of deployment. Because of these distinct differences, Triad represents an enormous threat to the Soviets, one that takes a tremendous expenditure of national resources to counter, if indeed each component can be defended against to a satisfactory degree. The Soviets have invested heavily in a variety of detection and defense technologies.

In addition by having three elements, the United States is hedging against a Soviet breakthrough in one defensive technology that could degrade one of the elements. If a breakthrough does occur, the other two elements can still maintain a sufficient deterrence while the third one is upgraded to overcome its shortcomings. It is extremely unlikely that breakthroughs in defensive capabilities will simultaneously negate two or three elements. In other words, the United States has not placed its reliance on one deterrence system only.

By having three independent elements, the United States has a far greater chance to achieve and use its own technological breakthroughs to improve its deterrence posture. We have a threefold chance to create an improvement that will prevent the Soviets from exploiting their strategic systems or overcome a Soviet defensive superiority. What is even more important is that, because Triad is an integrated system, we can improve overall Triad deterrence capabilities by improving the element most amenable to upgrading at the time and the element that provides the greatest increment of improvement for the least investment of resources.

While each Triad element has key strengths, each also has weaknesses. However, the three elements complement one another so that a weakness in one element is compensated by a strong point in another. Thus when all three elements, each with its own unique capabilities, are taken as a whole, the sum of our deterrence posture represents an insurmountable obstacle to an opposing strategist. Even though he might be able to negate one or two elements, it is the entire Triad concept that deters. It is impossible to negate all three Triad elements simultaneously and hence avoid a retaliatory attack. Further, it should be noted that a single U.S. missile with its multiple warheads which slips through Soviet defenses still may represent an unacceptable amount of damage to the Soviets.

Finally, Triad gives the United States more bargaining power at the arms limitation negotiating table: we have more options and more items to be traded. A further confirmation of the validity of the Triad concept is the fact that the Soviets are adopting this three-element posture themselves.

What the SLBM contributes to Triad

While each Triad component has several advantages, the key advantage of the ICBM is its quick response and accuracy in hitting the desired target. For the strategic bomber, it is flexibility and the ability to be recalled after launch. The SLBM has its key advantage in its survivability and the difficulty it presents to enemy surveillance, detection, and defensive systems.

The SLBM submarine can go undetected in the vast ocean areas that comprise a major portion of the earth's surface. A U.S. nuclear submarine equipped with missiles that have a range of 2500 nautical miles, like the current Polaris and Poseidon missiles, has millions of square miles of ocean to operate in and still be within range of targets in the Soviet Union.1 Trident I missiles, destined for use in the early 1980s with a full payload range of 4000 nautical miles, will have access to even four-and-a-half times more ocean area in which to hide. The Trident II, planned for the mid-1980s, will achieve an even greater range and payload combination. Not only can the SLBM use vast amounts of the earth's oceans to avoid detection, it can stay away from port for relatively long periods of time, thus decreasing the possibility of its being trailed from port to its hiding place. The usual sixty-day tour on station is not dictated by the endurance of the submarine and its mechanical systems but is governed by the time the crew can remain in isolation without suffering severe decrease in efficiency and morale.

In addition, since the SLBM submarine can be constantly moving, the Soviets must keep real-time information on its position. They cannot just locate it once and file the position in the targeting computer. If they lose one submarine, they must detect it again because of the damage potential just one unaccounted-for submarine represents. Although antisubmarine warfare (ASW) capabilities are improving, there are still many countermeasures, decoys, and quieter submarines to counter these improvements. Thus, the SLBM's advantage from a detectability standpoint remains secure. And because the other Triad elements are contributing to the total deterrence picture, our deterrence capabilities are not degraded to an unacceptable level while these improvements are implemented.

In discussing the SLBM, one would be unfair not to point out some of its shortcomings and the environment in which it operates. The main defense a missile-carrying submarine has is the ability to hide: once detected and its position known, its effectiveness is degraded until evasive action can be taken to get lost again. Besides quieter operation and the use of decoys to confuse the enemy's detection systems, submarines can be made less detectable by operating mainly in regions of the ocean where storms and other ocean produced noise mask the submarine's own sounds.

Because the submarine is a mobile launch point, it is difficult to know its precise location continually. Thus, since the starting point is an important part of a ballistic trajectory computation, the SLBM's accuracy on target is degraded in comparison to the land-based ICBM. Inasmuch as the SLBM carries 16 missiles-or in the case of future Trident boats, 24 missiles--a portion of the force is located in a single spot. A loss in capability occurs when the submarine is in port for repairs or crew change as well as when it is knocked out by enemy action. However, the SLBMs can be launched from port and still reach their targets. Also, in times of tension, more boats would be on alert.

Communications and command and control present some difficulties for the submarine force although not insurmountable. Very-low-frequency radio signals can penetrate a short distance into the water, so the National Command Authorities can be in communication with the submarines without their needing to surface and expose themselves.

Fortunately, weak points in the SLBM are compensated for by the other elements of Triad, and the SLBM is allowed to contribute its unique capabilities in the area of survivability and undetectability. The less accurate SLBM is still sufficiently accurate for "soft" targets such as industrial complexes and strategic bomber bases. The ICBM and bomber-based delivery systems, with their yield/accuracy combination, can be targeted against the "hardened" targets such as ballistic missile sites, hardened command centers, hardened industrial targets, etc., where essentially a direct hit is mandatory to achieve destruction.

Under normal world conditions, the usual number of missile-carrying submarines in port and going to and from station can be tolerated since essentially the entire ICBM force is continually on alert. Both the ICBM and the SLBM suffer from the inability to be recalled once launched. At times, the world situation may dictate that the United States merely indicate a show of force or national resolve rather than actually launching an attack. The strategic bomber offers this recall capability as well as several other unique features to Triad.

There is a point of controversy between the advocates of sea- and land-based ballistic missiles. Some proponents of the SLBM state that placing our deterrence force at sea decreases the chance that our country and especially its urban areas would be destroyed in a nuclear holocaust. If only our SLBMs were attacked, it would churn up the oceans a bit and we might lose some submarines and their crews, but our cities could go undamaged. But this is only part of the story. By having a single system to counter, the enemy has a much simpler targeting problem, just as if we used bombers or ICBMs alone. Additionally, the enemy might feel that we would not launch an attack if our submarines started to be destroyed. The United States would probably think twice before launching the remaining SLBM force against enemy cities, and because of the relative accuracy (or inaccuracy) of the SLBMs, they can be used effectively only against population and industrial centers. Such an attack would risk a retaliatory response against our cities, an unacceptable result. Thus, the U.S. could be subjected to nuclear blackmail and required to submit to enemy demands. As a result, the entire concept of deterrence would be undermined. It is only because of our maintenance of three viable elements of Triad that the enemy would hesitate to launch any type of attack. Consequently, we must retain a creditable deterrence posture.

History of Submarine Launched Ballistic Missiles

The United States has had an operational SLBM force since November 1960, when the first Polaris-carrying submarine, the U.S.S. George Washington, put out to sea on patrol This was five years after the first U.S. nuclear submarine, the Nautilus, was launched. This five-year period was needed to develop a solid propellant missile system to launch an SLBM from a submerged submarine. The first successful underwater launch of a Polaris missile occurred in July 1960, again from the Washington. A total of five submarines were fitted with the 1200 nautical-mile-range A-1 Polaris missiles.

To improve the capability of the Fleet Ballistic Missile (FBM) force, the 1500 nautical-mile-range A-2 Polaris was developed. The A-2 was first launched from the U.S.S. Ethan Allen off the Florida coast in October 1961. Eight nuclear submarines were equipped with the A-2 missile.

The next generation Polaris missile was the A-3, with a 2500 nautical mile range. Even though this Polaris fit in the same launch tubes as its predecessors, it was an 85 percent new missile. 2 Besides an increase in range, each missile now carried three warheads; however, they were not independently targeted but were designed to hit a target in a prearranged pattern. The first A-3 was launched from the U.S.S. Andrew Jackson in October 1963. A month later, President Kennedy watched the launching of another A-3 at Cape Canaveral. The A-3 became operational with the deployment of the U.S.S. Daniel Webster in September 1964. A total of 33 boats were equipped with the A-3, including the original five A-1 carrying boats which were refitted with the A-3. The A-3 equipped boats represented a significant increase in deterrence capability, for with a 2500 nautical mile range this missile can reach any target on land. 3 By 1967, the U.S. had 41 Polaris submarines carrying either A-2 or A-3 missiles on patrol.

The next SLBM was so different from the Polaris that it was given a new name, Poseidon C-3. While the Poseidon was based on Polaris technology and still fits the same tubes, it was a larger, heavier missile. The most important difference was Poseidon's multiple independently targetable reentry vehicles (MIRVs). The first launching of a Poseidon from a submarine occurred in August 1970 from the tubes of the U.S.S. James Madison. The first C-3s became operational with the deployment of the U.S.S. Madison in March 1971.

Currently, the FBM force consists of Polaris A-3 and Poseidon C-3 missiles. Ten submarines are carrying the A-3, while the remaining 31 have been fitted with the C-3. The earlier A-1 and A-2 versions of the Polaris have been retired.


Submarines. There are three classes of Fleet Ballistic Missile submarines in operation. The early five boats of the George Washington class with their 382-foot lengths and 6700-ton displacements carry the A-3 Polaris now. The boats of the 410-foot, 7900-ton Ethan Allen class also launch the A-3. The Poseidon-carrying boats consist of 31 Lafayette-class submarines with their 425-foot lengths and 8250-ton displacements. The submarines are powered by steam turbines that get their energy from water-cooled nuclear reactors. With an atmospheric control system of immense capacity, the submarine does not even have to raise a snorkel to obtain air. If it were not for the needs and endurance of the human crew, these submarines could stay on station almost indefinitely. Each submarine carries a crew of 12 to 14 officers and about 130 enlisted personnel, and each has two crews, a Gold and a Blue one. While one crew is on patrol, the other is in port training, orienting new crew members, taking leave, and in general getting ready for the next cruise. Normally, the submarines are on station for sixty-day periods.

The Polaris and Poseidon missiles are launched from the submarine's 16 tubes while the craft is submerged and out of sight. The missile is ejected from the tube either by compressed air or by a gas and steam generator system. Once the missile reaches the water's surface, the first stage of the missile is ignited and sent on its way. There is access to each of the 16 independently controlled launch tubes even during patrol at sea for performing inspection and maintenance of the missiles.

Missiles. The Polaris's two stages are filled with solid propellants. The first stage of the A-2 version of Polaris used a steel case, while its second stage and both stages of the A-3 have glass-fibre cases. Incidentally, the Polaris was the first large solid-rocket motor to have a glass-fibre case. The A-3 is 32 feet long, an inch longer than the A-2, both missiles having a 54-inch diameter. The A-2 and A-3 have total weights of 30,000 and 35,000 pounds, respectively.

The Poseidon is also a two-stage missile with its solid propellants carried in glass-fibre cases. The Poseidon has a substantially larger payload capacity, achieved mainly by its larger size which allows it to carry as many as 14 MIRVed warheads. It is 34 feet long, has a 74-inch diameter, and weighs 65,000 pounds.

The Polaris and Poseidon missiles have inertial guidance systems for directing the missile on a ballistic trajectory after launch from the submarine tubes. The system compensates for winds and other flight effects, keeps the missile in a stable flight attitude, and triggers the separation of the reentry vehicle (RV) from the missile to allow the RVs to continue on their ballistic trajectories to their targets. In order for the SLBMs to reach their targets accurately, very precise targeting information must be fed into the missile guidance memories prior to launch. Since the trajectories change as the submarine moves around, trajectory input data must be constantly updated. This is the function of the Polaris/Poseidon's fire control system. This system consists of a high-capacity digital computer that takes data such as the submarine's location, the local vertical direction, true north, and the target location and updates trajectories for each of the 16 missiles every few seconds. This system can prepare missiles for launch at a rate of one about every minute. 4

Support facilities. There is more to the FBM fleet than just the submarines and missiles. First, there is the worldwide communications newtwork that ensures positive control over the launching of the missiles to assure that they can be launched if necessary at the command of the President. Land-based, airborne, and satellite transmitters all playa part in this network. By use of very low-frequency radio transmitters, positive control can be maintained with the always submerged submarines without revealing their locations.

Then there is the fleet of support vessels, including several submarine tenders for maintaining and resupplying the submarines while at sea and transports for carrying missiles. A converted cargo ship, the U.S.S. Compass Island is used to verify the accuracy of the navigation systems of the submarines which pinpoint their location at all times. A specially configured Operational Test Instrumentation Ship, the U.S.N.S. Range Sentinel, is used for flight safety and to gather telemetry data during operational test flights of the missiles.

Finally, there are the land-based support facilities. Several shipyards on both the East and West Coasts not only built and initially fitted-out the boats but they also overhauled and refitted the new types of missiles and modernized the submarines themselves. To train the crewmen to meet the highly technical and demanding jobs aboard an SLBM submarine, the Navy has several specialized schools that teach everything from basic digital computer theory to nuclear power-plant operation. There are initial training schools that convert basic recruits to missilemen as well as advanced and refresher courses in every aspect of FBM duty. Since the FBM fleet uses both the Atlantic and Pacific oceans, operational support facilities are located on both coasts. Missile assembly facilities at Charleston, South Carolina, and Bangor, Washington, can assemble missiles from completed subsystems and sections supplied by contractors, check them out, store them, and finally load them aboard submarines, their tenders, or resupply transports. Naval shipyards at Charleston and at Bremerton, Washington, are equipped to perform maintenance and check-out of the submarines themselves. Finally, there are extensive facilities and test ranges used in developing and testing the entire SLBM system. The chief testing site is at the Air Force Eastern Test Range at Patrick Air Force Base, Florida. Here are the launching pads and blockhouses in addition to all sorts of missile assembly, check-out, instrumentation, supply, and administration buildings needed for development launches of new missiles. Additional testing is done at such locations as the Pacific Missile Range off the coast of California and at the Navy's China Lake facility in the heart of the California desert.

Trident I and II

The Navy currently has new missiles and submarines under development. They are the Trident I and II missiles, which use advances in technology to achieve greater range and accuracy. * There are also the new, larger Trident submarines, which will carry more missiles, use new technology to be quieter and faster, and employ advances in command and control techniques. They will be replacing the older of the Polaris/Poseidon boats, which will be reaching their projected twenty-year service lives by the early 1980s. By 1987, all the current 41 FBM submarines will be more than twenty years old.

*TRIDENT Test Successful. Navy's new TRIDENT ballistic missile was successfully test-fired in late April from a pad at Cape Canaveral, Fla., with all three stages working. This was the fourth test and some 20 to 25 more pad launches are scheduled before submarine launches are to be tested sometime in the summer of 1979. Commanders Digest/May 12, 1977, p. 4.

The Trident I missile is designed to fit the same missile tubes as the Poseidon but achieve almost twice its range. Ten of the Poseidon boats will be fitted with these new missiles. In order to get more than 4000 nautical miles range out of the 74-inch diameter by 34-foot package, the Navy has done many things. First, a third stage has been added. Second, more energetic and denser propellants are packed into all stages to provide more efficient use of the propellant load.

Finally, many of the missile components have been made lighter so that weight saving can be applied to increasing range. More compact and lighter microelectronic circuits have been used in the design. Graphite epoxy materials have been substituted for aluminum, giving the same strength for half the weight in many of the missiles's load carrying structures. The nose of the Trident, which is subjected to searing temperatures while flying through the atmosphere, has a unique design. First, the nose is made of Sitka spruce wood. This material can sustain the heat load, is a good insulator, and is able to handle the loads during hoisting and loading aboard the submarine. Buried in the nosecap is an aerospike device that pops out during flight. At supersonic speeds, a shock wave is formed on this spike and drastically reduces the drag on the blunt, ogive-shaped nose of the missile. The postboost control system that drives the missile payload to the right location so that the warheads can reach the proper target is designed to operate at higher temperatures, thus reducing the weight for its thermal protection equipment. In all, these nonpropulsion items contribute hundreds of nautical miles of increased range.5

The first Poseidon submarine will be refitted with the Trident I missile in fiscal year 1979, and a total of ten submarines will be refitted through FY 1982. Although a goal of the Trident design was to retain as much commonality with the Poseidon missile as possible, the Trident will use about 30,000 individual pieces of equipment different from those in the Poseidon. 6

A second generation Trident missile is also being planned for the 1980s. This is the larger Trident II missile which will capitalize on Trident I technology. In addition to the new missile, new submarines are also being built. These are the larger Trident boats with their 24 missile tubes. These boats will be made quieter and faster by using improved nuclear power plants. For example, for quieter operation, the submarine will use quieter air reducers and will be equipped with advanced sound isolation. These new boats will be fitted initially with Trident I missiles; however, by the mid-1980s they will be operational with Trident IIs aboard. The Trident submarines will be considerably larger than the Poseidon boats, 560 feet long versus 425 feet. This additional size will not only accommodate eight additional missiles but will allow more room for the crew, which will be essentially the same size as the current crews.

The increased range of the Trident system will provide for more than just a larger portion of the ocean in which to hide. The increased range allows basing to be entirely within the continental United States, thus eliminating costly and sometimes politically unstable overseas bases. The Trident-carrying boats can be on station virtually as soon as they leave port. This means more time on station during each patrol. So in reality there will be more missiles ready for launch at any one time.

For the Trident system, the Navy plans to have ship refit, missile support, base support, and crew training located entirely within the United States. This means reduced personnel costs and greater stability for the crews and their families, When not at sea, the men will perform all the shore preparations and training at home, greatly reducing travel costs and hopefully increasing the retention rates highly skilled but volunteer crewmen. Although Polaris submarines have operated in the Pacific since 1964, basing of the Trident system in the Pacific will, in conjunction the Atlantic-based Poseidon force, confront the Soviets with an extensive two-ocean threat. This threat will be expensive to counter and probably could not be very effectively countered without bases near the coastline of the United States. 7

THE CONCEPT of Triad was perhaps best summarized by Secretary of Defense Donald H. Rumsfeld during Hearings before the House Armed Services Committee in support of the fiscal year 1976 military budget.

U.S. strategic nuclear deterrence continues to be based on a Triad of strategic forces, These forces are designed to ride out a surprise attack and retaliate in a controlled second-strike at Presidential direction. A combination of ballistic missiles-land- and sea-based-and heavy bombers is necessary to diversify the strategic forces sufficiently, so that neither system failures nor enemy ingenuity could prevent retaliation. Responsive command and control of these forces is essential to deal with the possibility of less than all-out attacks and to terminate a nuclear exchange at the earliest moment possible if, despite best efforts, deterrence should fail. 8

The United States SLBM fleet has contributed its unique capabilities of survivability and deception to Triad for over a decade. Polaris and Poseidon have served well and will continue to do so for some time into the future. However, this capability will be augmented by an even more capable system, the Trident missile and submarine,

United States Military Academy


1. Herbert Scoville, Jr., "Missile Submarines and National Security," Scientific American, June 1972, p. 18.

2. "Polaris and Poseidon-FBM Facts," Strategic Systems Project Office, Navy Department, 1973, p. 7.

3. Ibid.

4. Ibid., p. 13.

5. Clarence A. Robinson, Jr., "New Propellant Evaluated for the Trident Second Stage," Aviation Week & Space Technology, 13 October 1975, p. 15.

6. "Trident Subsystem Tests in Final Phase," Aviation Week & Space Technology, November 3, 1975;, p. 38.

7. Tom Nugent, "The Trident Story," All Hands, February 1975, p. 6.

8. Statement by the Honorable Donald H. Rumsfeld, Secretary of Defense, Hearings on Military Posture before the House of Representatives' Armed Services Committee, 94th Congress, 27 January to 11 February 1976 (U.S. Government Printing Office: House Armed Services Committee, 94-13).

The illustrations for this article are official United States Navy photographs.


Lieutenant Colonel William D. Siuru, Jr., (Ph.D., Arizona State University) is an Instructor and Course Director in the Department of Engineering, United States Military Academy. He has spent his entire military career in the research and development field, with assignments at the Air Force Rocket Propulsion Laboratory, the Space and Missile Systems Organization, and at Wright-Patterson AFB. Colonel Siuru is the author of many articles and books on technical subjects, including previous articles in Air University Review.

Disclaimer The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.


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