In the next several decades, restructured naval forces will play an important role in regional conflicts. Moreover, submarines are expected to be key players in regional uses of force — to solve political problems and provide a proper defense of U.S. interests. Crisis situations are expected to evolve in many locations worldwide, and with increasing frequency, and forces using missiles will be particularly important in such situations.
Moreover, dependence on aircraft carriers — the cornerstone of our forward deployed Navy – for regional defense, may at times be restricted, particularly against countries with long submerged endurance, high performance submarines. (The German 209s, now widely proliferated to many foreign navies, proved difficult for modem British ASW forces to destroy in the Falkland Islands War of 1982.) This potential constraint to the unrestricted use of aircraft carriers could place a high premium on a U.S. Submarine Force with modernized weapons – mainly Submarine Launched Cruise Missiles (SLCMs).
Up to now, U.S. submarines and their weapons have been structured to meet the major war threat posed by the Soviets. However, the marked downgrading of this threat plus the ascendancy of Third Power political crises – in the present unipolar world – may affect U.S. defense interests and call for a Submarine Force modified to better fight the relevant conflicts. The use of SLCMs — all weather weapons – in conjunction with and in coordination with missiles used by other forces is now recognized as a major factor in quickly achieving decisiveness in regional hostilities, as was demonstrated in Iraq.
Importantly, with budgetary constraints a reality for at least the next decade, in order to have submarines which can use their missiles efficiently in regional wars, there are basically two directions to be taken in submarine force restructuring – build submarines specially configured for the Third Power environment or modernize the existing weapons. Significantly, it is impractical to modernize the structure of the submarine force by building a new, responsive submarine — because of the great time that it takes to realize a force of new submarines. At best, a new submarine might be operational in the second decade hence. Whereas, modifications to weapons appear to be achievable in the near-term of this present decade. Having a modernization program for torpedoes suggests retention of ADCAP torpedoes as presently configured to meet regional ASW threats and the acquisition of a low-cost antiship torpedo. On the other hand, modernization of submarine missiles is not so easily rationalized – and needs first, a definition of what they comprise and then the low-cost ways to achieve their modernization.
The nuclear SLCM is solely a Tomahawk varianl It can Oy 1,500 miles at 450 knots and deliver a medium yield device with about 60 meter accuracy. Its role in regional conflicts is likely to be minimal, except that regional forces with a nuclear capability may be deterred from the use of their nuclear weapons because of the potential use of nuclear SLCMs. In addition, its presence in the U.S. inventory constitutes a hedgetype capability if a major war against a nuclear power is threatened.
The submarine launched non-nuclear cruise missiles may be either short range Harpoons or longer range Tomahawks. Both have variants for either the land attack or antiship mission. Moreover both are operational on many of today’s U.S. attack submarines.
Recognizing that there are marked differences between these two kinds of non-nuclear SLCMs, it is valuable to define each weapon so that their modernization can be related to costs and capabilities for the next decade.
The Harpoon SLCM is a torpedo-tube launched encapsulated weapon which after ejection submerged, flies at 510 knots to over 60 miles. It is turbojet powered, weighs 1,530 pounds with its 13,000-pound thrust booster attached, and delivers a 507pound penetration blast warhead with proximity and time-delay fuzing. It uses inertial navigation and a radar altimeter for midcourse guidance and an active radar for terminal homing on its target in the antiship variant. The Harpoon modified for the Iraq war for a land attack mission used the DSMAC scenematching system with a 1V seeker to home on its targel The Harpoon is 13.5 inches in diameter and is 182 inches long with its booster attached. Its present cost is about $1.0 m. per unil.
The conventional Tomahawk SLCM is a turbofan-driven cruise missile with a 1,000 pound Bullpup warhead. It flies at 480 knots to at least 750 miles, hugging the sea or terrain over which it travels, using TERCOM (Terrain contour matching) along with inertial navigation for its midcourse guidance and DSMAC for its terminal homing in the land attack variant, or radar homing in Tomahawk’s antiship variant. With a small frontal-area radar cross-section its stealth characteristic is good. Tomahawk is 21 inches in diameter and is 246 inches long and weighs 2,650 pounds with booster. Its present cost is estimated to be over $2.0 m. per unit. Since Submarine Force restructuring for efficient response to regional conflicts is likely to involve shallow water operations and be severely constrained by budget limitations, a low-cost modernization of both Harpoon and Tomahawk is indicated and in a near time-frame. The development of new weapons requires too many years of work before they become operational, making this approach an impractical solution for the next decade.
Modernization of the inventory of Harpoons for the new environment of regional hostilities might be best accomplished by merely providing a more destructive warhead for its antiship variant. Against ships in regional wars — ships which for the most part are likely to be using shallow water areas of the seas –the Harpoon’s range of 60 miles, plus its other characteristics, except for its warhead, seem satisfactory and responsive to submarine needs for Third Power engagements. Thus, an antiship Harpoon with a warhead which produces great heat when it explodes in addition to its blast effects to both damage a ship and to spread the heat widely lnslde the targeted ship, seems appropriate. The Exocets used in the Falklands War, although not cruise missiles, nevertheless demonstrated that a small warhead of only 364 pounds of explosives did far more damage with the heat it generated from unexpended rocket fuel than by its blast effects. In fact, an unexploded Exocet whose rocket fuel burned after the weapon had penetrated the outer skin of the destroyer SHEFFIELD actually sank the warship due to the intense hot fires which raged out of control.
The 507 pound HE penetration warhead of the Harpoon is only marginally appropriate against merchant ships and Third Power warships – none of which are likely to have heavy deck or side armor. In fact, providing a very-hot explosion makes extra good sense against warships with aluminum superstructures. The aluminum may bum after a missile-hit. Fire has also proved more destructive of merchant ships than blast effects. Significantly, attrition of merchant ships can be expected in regional conflicts, as was seen in the Spanish Civil War of 1936.
In commenting on the naval portion of the just completed Iraq War, Norman Friedman in the May 1991 issue of the ProceedinflS generalized as to the use of antiship missiles against Iraqi ships and craft. He stated that “modem antiship missiles … hit and often disable their targets-but rarely sink them.” He further noted that, “The next generation of patrol boats and ships will probably have more distributed and more survivable systems. Hits may fail to even disable them, let alone sink them.”
Modernization of antiship missiles calls for warheads which will sink or at least disable today’s ships – not yesterday’s.
Tomahawk’s most pressing need for modernization is in its mid-course guidance system. The Iraq war illustrated first, the failure to have lERCOM data for the area in which Tomahawk might be used. Then, time consuming flights of surveillance satellites were needed to collect the elevation data necessary for digitizing into the TERCOM computer system. This also took additional time getting the data in its proper form for programming the Tactical Land Attack Missiles (TI..AMs) for particular land targets. At the outbreak of hostilities in future regional scenarios, there is likely to be DO TERCOM data available for that particular, unexpected area of conflict, and DO practical amount of time to derive the necessary elevation data to make the Tomahawk TIAM usable. Hence, a modification to present land attack Tomahawks which would substitute a GPS (Global Positioning Satellite) miniature navigation system for mid-course guidance would be the single most valuable modernization feature for the land attack SLCM. Such a guidance system with a small CEP, can destroy many targets efficiently even without activating a DSMAC terminal homing feature. However, utilizing the DSMAC system as well as the GPS positioning system should produce terminal accuracies to within a few feet of aim point, at ranges of many hundreds of miles. (In the Iraq war, a Tomahawk flew over 500 miles with inertial and TERCOM guidance and then with DSMAC terminal-homing reportedly flew into a cave with an 8-foot diameter mouth, and exploded the ammunition stored within the cave.) Significantly, the GPS guided SLCM with fmward looking radar altimeter and inertial guidance can be programmed far more simply and carry out its mission with less dependence on computerized programs which are susceptible to computer down-time for their reliability. Thus, for the conventional land attack Tomahawk the only major modernization item will be a substitution of a GPS guidance system for the present TERCOM system. A secondary modification should involve the warhead, since a 1,000 pound Bullpup warhead is far too limited in destructive power for the high cost of the weapon. Hence, trading off range to gain additional warhead weight and destructiveness is indicated. In addition, a modification to provide a means for attack evaluation is desirable. This might involve, at best, only the triggering of a signal to be received by a satellite when the Tomahawk had locked on to its DSMAC targeL Another type of evaluation signal might be generated by the explosion of the weapon. The antiship Tomahawk SLCM which uses the Harpoon’s mid-course and terminal homing guidance in its present configuration, can best be modernized by changing its Bullpup warhead to a heat generating warhead– by blowing unexpended fuel or by providing a special heat-generating fuel as part of the blast warhead, Importantly, for the likely conflicts of this decade, a range of 500 miles for an antiship weapon appears to be excessive.
Thus trading off range for increased warhead weight is logical. With the building of a new submarine or the modification of existing submarines likely to be accomplished in the far term rather than the near, and be extremely costly, it appears that the utilization of present submarines with better weapons is indicated as the low-cost approach to a responsive U.S. Submarine Force structure.
The 688s which have 12 vertical launch tubes are particularly well configured to fight the wars of this decade. They can eschew operating in shallow waters by projecting missile power into such waters as well as by projecting missile power across coastal seas into coastal land areas and the objectives they might contain – airfields, command and control centers, shipyard facilities, ships in port, communication complexes, bridges, railroads, etc. For submarines limited to just four torpedo tubes for launching missiles, only small salvoes of missiles can be rapidly employed. But, for many point targets, up to four missiles should be sufficient to do the job. However, for area targets, large salvoes of missiles should produce a best chance of effectively neutralizing or suppressing their activity. This would be true for communication complexes, ammunition dumps, airfields, oil storage areas, railroad yards, etc.
The significance of these suggested ways to make the U.S. attack Submarine Force responsive to regional threats by modernizing its weapons, is that such options offer a low-cost, practical near-term approach for ensuring a front-line role in regional conflicts. They also provide the wherewithal to fight coastal, shallow-water wars using existing submarines.