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By Rear Admiral Charles F. Horne III, U.S. Navy (Retired)
To aviators, “speed is life.” In the next century, for both commercial and military purposes, this maxim will apply to surface fleets, as well. Ships like this will have to sustain transoceanic speeds of 40-50 knots in sea state five, to remain competitive.
Many advances—jet airplanes, nuclear ships, satellites, and computers—have occurred in the 20th century. The 21st century will bring equally new and revolutionary developments that may include laser weapons, space platforms, and fast surface ships.
Looking 10 to 20 years ahead, not just to this year’s budget issues, one is forced to think innovatively.
The concept of competitive strategies emphasizes pursuit of those high technology capabilities that offer the most leverage in peace and war. The prominence of this concept will increase, given the natural limits on defense spending. If we accept this, where does surface ship technology fit?
Surface ships are currently limited to speeds of 30-plus
knots for two fundamental reasons. First, hull and powering resistance data accumulated for the past century infer that 30-plus knots is the practical outside limit for conventional monohulls. Second, there is widespread reluctance to apply large amounts of power to surface ships although airplanes now have 200,000 horsepower at sea level, almost the equivalent horsepower of a battleship.
The 21st century will demand fast ships because of the increasing tempo and changing environment of commerce and war at sea. Most cargo crosses the oceans of the world by ship. As the value and earning power of cargo increases, the demands for increased speed at sea will multiply. The ability to move combatant and cargo ships at speeds in excess of 40 knots and eventually at even greater speeds, in rough as well as calm seas, will afford significant strategic and tactical advantages. The Navy should examine, in a global context, maritime requirements the future will levy.
The United States is closely and irrevocably intertwined with many nations by alliances, trade, and commerce. Conflicts in the future will increasingly depend upon shifting aliiances and rising aspirations of Third World countries. Low intensity conflict will be of particular strategic significance. It will threaten vital resources and the
friendly orientation of the affected nations.
The U.S. Navy must be able to surge whenever or wherever needed. The element of surprise can be increased dramatically when surface ships can steam at 50 knots and cover distances of several hundred miles in a few hours. Speeds of 50 knots will mean greater fuel consumption, but the key point is that the ship will not surge all the time, it will do so only when the strategic or tactical conditions warrant it.
mitment is to reinforce its deployed divisions with additional men and material. This current commitment under
Speed also is imperative for battle group flexibility and mobility. The need for battle groups to disperse quickly and then contract will be increased. Battle groups must aPpear dispersed and random to enemy sensors, yet remain responsive to the battle group commander. The ability of some of the battle group’s ships to disperse at 50 knots to achieve spread formations greatly inhibits enemy targeting. Doubling a ship’s speed after being sighted by an enemy satellite can quadruple the area in which the ship can move out of danger during subsequent targeting and Weapon transit.
Within these battle group spread formations, high-speed 40- to 50-knot multipurpose replenishment ships would be force multipliers by providing responsive on-station replenishment for the widely dispersed combatants. Highspeed underway replenishment ships would extend the range of the battle group, permit it to stay on station longer, and increase its overall mobility.
In weighing where higher speeds at sea would provide the greatest returns, a strong case can be made that high speed replenishment ships would provide the most utility. This would be equally true in the case of shuttle ships that bring oil, ammunition, and supplies from the advanced logistic support bases to the battle group replenishment station ships—which then supply the combatants of the battle group. Both of these replenishment links of the Navy’s combat logistics force are vital to the battle group. The capability of the combat logistics ships to maneuver at 40-50 knots vice their current 15-26 knots, would greatly reduce their vulnerability, particularly when steaming unescorted, while significantly increasing their utility to ihe battle group.
As war at sea becomes broader in scope with space surveillance satellites and long-range missiles, the battle groups will be less able to leave strategic positions to provide close support for power projection. Small, fast, mobile expeditionary forces with amphibious, logistic, and escort ships capable of speeds greater than 40 knots could fill that job. Their ability to move rapidly, once the decision to commit is made, minimizes their need for direct elose support while maximizing the element of surprise. The quicker the power projection force can steam to the objective area, the less time the enemy will have to prepare and, concomitantly, less offensive power will be required to defeat the enemy.
NATO’s flexible response strategy will remain the basis of alliance deterrent capabilities. These capabilities will continue to require rapid reinforcement. The U.S. comlines the need for rapid reinforcement capabilities by air and sea.
With the growing pressures for multilateral troop withdrawals, either in the context of arms agreements or for burden-sharing reasons, increased capabilities for responsiveness in the event of a conventional war will be needed. The requirements for fast and effective force closure to NATO and elsewhere increase for political and military reasons. To meet these emerging 21st century requirements, supply ships that can sustain speeds of 40-50 knots in sea state five will be needed.1 Not only will these fast sealift ships make an Atlantic transit in two to three days vice five to ten days, under most weather conditions, but they will also be less vulnerable to enemy torpedoes and missiles. This reduced vulnerability of faster supply ships should permit independent sailing and negate any need to be convoyed.
Convoying as we understood it in World War II will not apply in the 21st century:
- Any conflict will be a “come as you are” war. No longer does any industrial nation have the luxury of planning the two-to-three year industrial mobilization and shipbuilding period that the U.S. enjoyed in World War II.
- Escorts left over from battle groups and other combatant tasks will be too few to provide convoy protection.
- Large concentrations of ships such as convoys will attract cruise missiles and aircraft targeting. Dispersion (independent sailing) is therefore a prudent tactic.
- Soviet submarines capable of traveling at speeds of 20-30 knots submerged will get under a large convoy, hide in it, run with it, and shoot it—like a fox in a chicken coop.
- A major cost benefit will accrue from unescorted fast sealift ships because fewer escorts will be needed for convoy purposes, permitting the limited number of escorts to concentrate on battle group tasks.
It is therefore pertinent to reexamine World War II data to determine what speeds afforded safe, independent sailings and then extrapolate these to 21st century requirements vis-a-vis the Soviet submarine threat. Study of the allied shipping policy during World War II indicates that speeds of at least 15 knots were required for independent sailing while 20-30 knot speeds were preferred. A look at Table 1, from the book War at Sea by Captain S. W. Roskill, Royal Navy, shows that 13-15 knots was on the very marginal side of safety for independent routing.
On the safer side of independent sailing were the large and fast luxury liners such as the Queen Mary and the Queen Elizabeth, which averaged 25-30 knots’back and forth across the Atlantic and other oceans, burning up to 6,000 tons of fuel on one voyage. Although loaded with as many as 15,000 troops, these ships and others in the 2530 knot category were never caught by the U-boats in World War II.
Determining what speeds were needed for low-vulnerability, independent transits during World War II, and then extrapolating for 20-knot submerged approaches by modern Soviet submarines as opposed to 10-knot surface approaches of World War II German submarines, Table 2 summarizes the speed requirements for successful 21st
10-kt submarine approach speed 20 kt submarine approach speed
45 /I nautical mile approach 45°/10-nm approach
20-kt torpedo with 5-nm range 50-kt toipedo with 20-nm range
Target Speed | Sub Speed | Limiting Angle of Approach | Target Speed | Sub Speed | Limiting Angle of Approach |
30 kt | 10 kt | 2i°* | 50 kt | 20 kt | 22°* |
25 kt | 10 kt | 25°* | 45 kt | 20 kt | 26°* |
20 kt | 10 kt | 32°* | 40 kt | 20 kt | 30°* |
15 kt | 10 kt | 45° | 30 kt | 20 kt | 42° |
10 kt | 10 kt | 60° | 20 kt | 20 kt | O 1 O r- |
* Indicates successful independen! sailings Chris Kronings, Queen Elizabeth at War (Patrick Stephens Limited: 1985)
Table 1 | Comparison of Losses to Independently Routed and Convoyed Ships, November 1940-May 1941* Independently Routed (T.3 to 15 knntvt |
|
| Freetown Route | Halifax Route |
Homeward-bound................ |
|
|
Outward-bound................ |
|
|
Rate of loss on round voyage |
| IQ QOL |
|
|
|
| Freetown | Halifax |
| Route | Route |
Homeward-bound ................... |
|
|
Outward-bound...................... |
|
|
Rate of loss on round voyage |
|
|
*Source: Captain S.W. Roskill, DSC, RN The War at Sea, Volume 1, The Defensive (London: 1954), p. 458
Table 2 Independent Sailing Analysis
_____ World War II__________________________ 1990-2010 Conventional War
century independent sailings. While most Soviet nuclear submarines have submerged speeds of 30-plus knots, allied advances in acoustic detection will probably limit their approach speed to quieter thresholds of around 20 knots.
Fast ships (40-50 knots) are needed to provide the low vulnerability required for high-value cargo. Should Soviet submarines in the future employ approach speeds of more than 20 knots, the need for 40-50-knot speed will intensify for successful independent voyages. The eight SL-7’s already in the U.S. inventory (speeds of 30 knots at full load) appear too slow for low-vulnerability independent sailing, but too fast to be tied down to a convoy. On the other hand, these eight SL-7’s, which are euphemistically called fast sealift, are at least a start in the direction of high-speed strategic resupply.
Throughout the Cold War, we have prepared for worldwide conflict, but instead have been bedeviled by Third World contingencies of lesser intensity in Vietnam, the Middle East, the Persian Gulf, the Mediterranean, and the Caribbean.
The United States will need faster and better ways to respond to low intensity conflict. It will need fast ships to cover long distances expeditiously with reduced vulnerability, since more Third World nations are acquiring submarines—including some nuclear submarines.
Former President Ronald W. Reagan would have been more effective politically if he could have sent surface mine warfare equipment and craft to the Persian Gulf at 50 knots instead of the 15-18-knot speeds he actually achieved. Britain’s Prime Minister Margaret Thatcher would have benefited had fast ships been available instead of the 15-knot ships taken up from trade during the Falk- lands Conflict. The shrinking numbers of U.S. bases overseas further emphasizes the need for rapid deployment capabilities.
For low intensity conflict, the concept of competitive strategies argues for acquiring several 40-50 knot cargo and amphibious ships along with several high-speed refueling and escort ships. The fast supply and amphibious ships also should have minimum draft (30 feet) and minimum underwater appurtenances, such as propellers.
Waterjet propulsion not only reduces acoustic signatures, but also eliminates propellers, permits access to shallow harbors, and simplifies maneuvering alongside makeshift platforms. These few high-speed ships would provide an effective response to Third World contingencies, and constitute a visible and credible deterrent.
The fast sealift ships also must be economically attractive to commercial interests in peacetime. Faster speeds should prove attractive for shipment of valuable and perishable cargo. Japan is convinced and has earmarked more than $70 million in research and development funds for their shipbuilders to design a 50-knot commercial supply ship that will carry only 1,000 tons of payload. Staying ahead in naval technology is just as vital to the United States as it is to other island nations like Japan. We have the opportunity to lead the way in commercial high-speed ships as well as naval vessels; these ships could be the cornerstone of a revitalized merchant marine.
U.S. Shipbuilders must confront the technological risks head-on and apply airplane-type power to our surface ships. If a 380-ton, Boeing 747 jet aircraft, carrying only 80 tons of payload, can accommodate 200,000 horsepower, then a 30,000-ton surface ship, carrying about 10,000 tons of payload, should be able to accommodate 400,000-600,000 horsepower.
It is important to recall that concerns over large amounts of power and related fuel costs did not stop visionaries from adapting the airplane to jet engine power or the submarine to nuclear reactor power. These major technological breakthroughs have long since demonstrated their worth and dispelled the early fears of excessive power and fuel usage. So, also, can the surface ship of the 21st century successfully be adapted to the power needed to transit the oceans faster.
The United States must design a hull to accommodate this power and exploit it effectively in sea state five or greater. An analysis of hull forms suggests that the classic monohull, designed to accommodate high power, is the path to follow for good sea-keeping at high speeds. The new hull must cross the residual drag wall that exists around 35-37 knots, without having to be longer and larger than the Queen Mary.
The best propulsion for fast ships will probably come from the aircraft industry; 50,000 to 60,000 horsepower gas turbines adapted for marine use. The aircraft industry has made improvements in gas turbine performance and economy that will benefit ship modernization. The U.S. Navy has been using gas turbines on its Spruance (DD- 963)-class destroyers and Ticonderoga (CG-47)-class cruisers with remarkable success for more than ten years. Much has been learned during this decade about marine gas turbines, including the possible addition of intercooled regenerative engines to improve overall fuel economy as much as 30%. Coupling relatively lightweight gas turbines with the flexibility of electric drive, now being pursued by the Navy, offers exciting surface propulsion.
The United States must develop the best propulsors for these 40-50-knot surface ships of the future. Research suggests waterjet propulsion. A case can be made that for seagoing ships to steam at speeds in excess of 37 knots, waterjets will be required. Evidence suggests that propellers are neither as efficient nor as adaptable as waterjets at speeds of 40-50 knots.
Equally significant are the other technologies that can be clustered with electric drive: “new propulsors, inherently more quiet and flexible than today; new hull forms, with dramatic improvements in both seakeeping and survivability. Indeed, the concept of a cluster of technologies is every bit as exciting as the potential of any of the technologies within it.”2
With the advent of electric drive, gas turbines, waterjets and other cluster technologies, automation will become a clear by-product of the fast ships of the future, leading to better ship control and reduced maintenance. These benefits in turn lead to fewer people to man fast ships—a real advantage in a cost-conscious world.
We must consider stealth as we pursue new propulsion and propulsor technologies. It is desirable to reduce the probability of interception by increasing ship speed, and also by reducing acoustic and radar signatures. Waterjets required for high speeds are less prone to cavitation and vibration than propellers. Their wake characteristics are less turbulent. Electric drive to eliminate noisy shafting and gearboxes, gas turbines mounted as high as possible in the ship, and waterjet propulsors should significantly quiet the ship—all major contributions to stealth.
The U.S. Navy, comparable in assets and worldwide commitments to a trillion-dollar corporation, should establish a clear and sustaining research and development program of associated cluster technologies to develop fast ships within the next 20 years. The amount of research and development to acquire fast ships and the pace of the program are not critical at first; the idea is to get started, so that industry’s technological innovation, for which the United States is renowned, can begin to focus on the objective.
Sea power has been essential to the United States. We have made many state-of-the-art advances in aircraft carriers, nuclear submarines, and Aegis-equipped ships. We can not dismiss high speeds for surface ships as too esoteric, too expensive, or too far in the future. The need for speed is evident all around us—in computers, in media reporting, in transportation, and in business.
For sea power to flourish in the United States, we must invest in future force multipliers. One force multiplier will always stand out—faster ships.
'The Atlantic is well-known for its heavy seas and storms. Ships experience sea states of five or greater an average of 45% of the fall and 35% of the winter in the Atlantic.
"Admiral C.A.H. Trost, U.S. Navy, Chief of Naval Operations, “The Cresting Wave,” keynote address, Navy Research and Development Symposium, Naval Surface Warfare Center, White Oak, MD, 26 Sept. 1988.
Rear Admiral Home is an associate with McDermott Incorporated and Babcock & Wilcox. He served as Commander, Mine Warfare Command and Commander, Naval Forces Korea before retiring in January 1987.