Speed in Warships

 

 

 

 

 

in

the shore, obscured from radar or visual detection. High speed is then important in attack as well as in retirement, for it minimizes the exposure of the at­tack boat to counterattack. This example is partly analogous to the destroyer case, when speed was in part a matter of reducing the duration of exposure to enemy attack. However, for the modern attack boat, high speed also buys a quick reaction against a time-urgent target. The boat need not remain on sta­tion, exposed to attack. Of course, as in the English Channel in World War II, high speed might allow such a boat to spend more of her time loitering on station and so allow for economies in the number of boats, and crews. The crucial factor is the range to which the boat must close before firing. Although the fast attack boat might spend far more of her life at high speed than did the destroyer, she is still de­signed only for short periods of high speed; she sim­ply avoids sea conditions in which her burst speed cannot be maintained; and she operates at high speed

for only a short period at a time. Indeed, even attack boats in which speed is used partly to reac loiter areas spend most of their lives at cruisin? speed.

Recent Soviet coastal ASW practice shows anothe^f application of very high, short-term speed. Th^e Soviets consider it vital to prevent alien ship⁵’ whether surface or submerged, from operating their coastal waters. This demands very quick tran sits by submarine craft from base to target area- not least because of the fleeting nature of submarine contacts: there is no Soviet SOSUS. Thus Soviet int£^f est in hydrofoil “subchasers” and, most recently, WIG devices. Such craft do not carry out Western style ASW operations. Rather, like fast surface attaC boats, they wait in port for the word that a su marine'has b.een discovered. Then they fly out, the^lf high speed minimizing the post-detection unc^er tainty which would arise from the submarine’s &⁰ tion. In principle, the higher the speed, the less ^ need for elaborate search sonar once the point of c°ⁿ tact is reached. Of course, the trade-off betwe^el1 transit speed and sonar requirement depends to so&^e extent on the acquisition range of the ASW weapon⁵

Proceedings / Naval Review ¹

As for submarines themselves, high speed retai ^ its tactical usefulness, mainly as a means of manen vering relative to fast targets, for it is very diffi^clj^ to close a 20-knot task group in a 10-knot su marine. In addition, just as with the old destroy^efj’ high speed can limit the time the submarine sp£ⁿ

as

tjj -^^e depth charge and hedgehog had to be sent on

the ^{f Way} °^{n C}^^e basis of information available before ty_as ^rnornent of launch; what happened afterwards fasted ^COntes,: between designers working towards fhe ^{r S}‘^nkln« ^weapons (i.e., a shorter dead time) and I_n^nianeuverability of the target.

We ^{aCt> ran}S^e> rhe speed of the weapon, and what For"" ^Ca^ ^terminal guidance are all closely related. b_eca^{an Utl}8uided weapon, “dead time” is a bit more, t₀ tk ^Se °f delays in passing the fire control solution

imposed ^t0 atta^k, especially when her adversaries are ¹ nil ted in speed by sonar conditions, fac °^WCVer ’ ^suc^ ^sP^eed loses much of its value in the I°ⁿg-range weapons such as Ikara, which has a * about ten miles and can be guided in flight, _t^e?^{r tkat ma}tter aircraft, which can greatly extend ^etnal area around an ASW platform. Moreover, at ^Wlth current technology, very high submarine ^s imply relatively easy detection of the sub- ^•ne by passive sonars.

e corrimon feature of all of the examples from anc ^^aSt *^{S s}^^{ort ran}S^e and lack °f terminal guid- thg⁶ t^*^{e wea}P^ons involved. Even at the peak of th^Clr ^^eve^°P^rnent> naval guns could not fire more _a ^{an a}^^out twenty miles. Their effective range ^Caus ^St maneuvering targets was far less, be-

Use^^e delays inherent in the fire control techniques _re . ^{ln e}ffect, because of the impossibility of cor- the            ^a*^{m a}^^{ter t}^^{le mom}ent of firing. The length of

have ^^CaC^ ^t*^me between launch and impact could j_e 'important consequences. Thus the remarkable str^^{C tame tke seven} U- S. destroyers and de­fi_re ^{yer escorts} survived under Japanese capital ship in 'u ^t^^C ^^att^^e °ff Samar in October 1944: by chas­^{e s}plashes of each salvo, the small ships could *ⁿg b ^C^^{C correct}'^ons Japanese gunners were mak- ^c°uld^e °^{re                   t}*^{ie next sa}'^v0- effect the latter

fan ^*^aVe k^een certain of hitting only at very short sur ^e               ’ⁿ consequence, four of the seven ships

p_ej_Q^1Ve^- Similarly, although by 1941 some, tor- _g ^{es ka}d ranges as great as 20 miles, obtaining a l_au Percentage of hits in battle required the torpedo ^{er t0} close; otherwise the target would have t_e. .^t0 evade a weapon whose course had to be de- ^J*ⁿed before it was launched.

e ASW problem was analogous. Weapons such

b_ecau ^UtlS^u*ded weapon, “dead time” is a bit more,

(or ^ ^WeaP^on °r launcher. While the weapon flies d_ep     ^rbe target maneuvers. The chance of a hit

bow ^S °^{n kow} rbe target has to maneuver, on ^radi ^V'^0lently ‘^{c can} maneuver, and on the lethal cojj^ °f the weapon. For example, in World War II tirne^k¹⁰⁰^ ^sbebs hit less than five percent of the n_Uci ’ ^Ut nowadays, no matter how badly aimed, a ^ar shell fired at a range of 20,000 yards would rarely miss. As ranges grow, so does the “dead time” and consequently the value to the target of being able to take evasive action and hence of high burst speed. Indeed, a fast target could use her burst speed simply to open the range and thus to improve her odds. If the attacker were the faster ship, she could use her burst speed to close the range.

Aircraft, which came into their own at sea during World War II, added something new: terminal guidance. In effect, an airplane was (and is) a missile able to overcome its “dead time” by intelligently seeking its target even many hours after launch. Of course, airplanes had other important virtues, but perhaps the greatest was that they eliminated much of the need for burst speed on the part of their launch platforms. In this sense the carrier is the prototype of all modern missile-armed warships, in which burst speed is of limited value for offensive purposes.

Still, burst speed was quite valuable during the Second World War as a defensive mechanism, even against air attack; but that was because the airplanes themselves attacked with bombs and unguided tor­pedoes, weapons incorporating substantial dead time. Once the air-launched weapons were provided guid­ance, ship speed and maneuverability lost a lot of their value—although, of course, guidance systems were not, and are not, by any means infallible, and in some circumstances a maneuvering target can still fool a guided bomb. However, it is fair to say that the development of self-guided aircraft weapons, opening in 1943 with the German FX 1400 bomb which sank the Italian battleship Roma, completes an evolution away from short-range, dead-time weapons. The great postwar development has been the extension of such long-range devices to platforms far simpler than aircraft carriers. Modern surface-to- surface missiles, then, reduce considerably the tacti­cal value of speed, at least for the range of speeds attainable by conventional ships.

By themselves long-range weapons lack this effect; it is only when they are combined with long-range sensors that the effect comes into play. To some ex­tent the evolution of carrier aircraft concealed the significance of the sensors, since the aircraft com­bined both sensor and weapon functions. Unlike other long-range weapons, which are wasted if they find no targets at the end of their runs, aircraft which do not find targets can be recovered and launched again.

The evolution towards a world of long-range weapons and sensors has been proceeding in stages, and it is vital to recognize that it is by no means complete. For example, though with their radar or plain eyesight PT boats could sense targets at 20,000 yards, they had to close to within about 500 or

1.0              yards to be reasonably sure of making hits with their unguided torpedoes. Now effective guid­ance makes it practical for their successors to fire from a range set by their onboard sensors, or about

20.0               yards. That is why many missiles designed for use by fast attack craft have ranges of that order. And, of course, it is easier to close to 20,000 yards than to 1,000. When external sensors can be used, ranges can be pushed far higher. Thus, the Soviets have long practiced integrated and centrally con­trolled coast defense operations, in which misile boats get their directions from a commander ashore. In such an environment, 200-mile weapons ashore (Shaddock) and 70-mile types afloat (SS-N-9 on the Nanuchka) become useful, and the concept of closing to weapon range becomes far less meaningful than formerly.

Moreover, long-range guided weapons do not in themselves eliminate all “dead time.” They just shift it from the assailant to the victim. That is, in the absence of automatic missile detection devices in the targeted vessel, the long range of an attack boat’s missile may, to some extent, restore the element of surprise found in classical PT boat operations. It cer­tainly did in the instance of the Israeli destroyer Eilat when she was attacked by Egyptian Styx missiles. In such cases, the “dead time” is the time it takes the target to recognize she is under attack and to react to it. However, it appears that the emergence of great numbers of small missile attack boats will force navies to invest heavily in just those sensors required to increase their warning time or, indeed, to neu­tralize fast attack boats before they can close to fire. Reportedly, U. S. formations have been surprised by West German torpedo boats in exercises in the North Sea and, in the Pacific, the hydrofoil missile boat Pegasus surprised a formation far from any land. So, the time to mount the necessary sensors appears to be at hand. The important point is that larger combat­ants can generally carry better sensors (e.g., sonars, LAMPS) and longer-range weapons than smaller ones can. Tactical speed itself will again be a declining asset in such circumstances. This likely trend is an important consideration if we are to assess properly the worth of future large SES programs.

The evolution of ASW makes clear the connection between weapon range and sensor range. Wartime ASW weapons were designed with short sonar ranges in mind; thus the 100-yard hedgehog worked in con­junction with a 1,000-yard sensor. The gap in range was important because of the time required to set up an attack and to follow up if the attack proved un­successful. By 1945 somewhat better sonar ranges

were in prospect. However, submarines had gotten substantially faster (the Type XXI, just becoming °P erational as the war ended), so that more could hap pen between sonar input and weapon arrival; and ** became necessary to interpose an elaborate comp^uter between the sonar and the weapon. Moreover, ^£^^e new weapon had to allow for considerable variation in attack range as a result of the submarine’s maneu

vers.                                                                    j

10

1*

Surface ship maneuver was constrained by the nee to maintain a simple fire control solution. These c°ⁿ siderations produced Weapon Alfa, an 800-y^ar fast-sinking depth charge. At this time the techno ogy for a much longer range device existed, and *® fact a cruise missile to carry a homing torpedo, cam the Kingfisher, was designed and tested. Reg^ret tably, it had to be cancelled because no sensor ^wlt compatible range existed. During the early much longer range, low frequency sonars (SQS-4, ^an then the 23 and 26) became practical, and at ont^e long-range ASW weapons were produced: Rat, th^ea Asroc and Subroc (the last for submarines low-frequency sonar). In each case the first stag^e 0 the weapon was ballistic, and the operator could n°^c correct his aim once the missile was enroute. T"¹’ solutions were employed in these weapons: term**¹ ^ homing (a homing torpedo, as in Rat or Asroc) ^an so great a lethal radius as to correct for aiming erf (nuclear warheads, as in some Asroc and all Subro* _ Another solution to the ASW dead time problem mid-course guidance, as in the wire-guided ^torP j_n and the helicopter-borne homing torpedo (Dash)- each case weapon capabilities reduce the demand mobility on the part of the launching platform- In fact some sonars, such as SQS-26, have detect*® ranges substantially better than the ranges of * weapons with which they are associated. In the ear sixties high surface ship speed was embraced ^aS _f means of ensuring conversion of long-range soⁿ contacts into sinkings, and a new ASW destroy project, called Seahawk, was designed to dash to'^var the enemy at 40 knots, using the new gas turbi*¹^ Seahawk was dropped partly in view of the success ship-borne helicopters which could themselves d^a out to a submarine contact and drop a torpedo of* though a great deal of time elapsed between the mise of Seahawk and the arrival of LAMPS. 1° event, Seahawk probably would have died from failure of the heavy sonar which was to have P mitted it to maintain contact even at high speed- Meanwhile work proceeded on short-rang^ light-weight homing torpedoes which initially conceived of as successors to the depth charge- ^ though thev were homing weapons, their acquis**¹

•₀ ^tarS^et- However, Asroc and the torpedo- _e helicopters largely eliminate this require-

at medium ranges.

b_ef₍₎^{e Was s}hort: they had to come close to the target ^arrntcl ^could be launched. Hence a torpedo­, ^S^'P still required high tactical speed to close

,                          u----------- a                       i.i                       i

Qri

ftent t₀ ^any ^case an ASW ship proceeding at high speed W,_e ^^r°^Secute a distant contact with short-range noise)"¹¹⁵ ^^{ost sonar} capability (due to her self- Whfch ^an<^ ^^{aVe awa}y ^er presence to the submarine, tango ^C°^U^ ^s^^oot hirst with her own rather longer- be _L ^^eaP°n. In effect, very high burst speed would anoth ’^{U rna}‘^nly to allow one ship to prosecute ASty ^{er S} ^'^stant sonar contact, and for some time ^c^c?arl ^attac^^cs were conducted in this way. However, the r, n WaS s'^mpler, ^at least conceptually, to have cone ^0secut‘^on done by a weapon embarked on the ^^tlng ^ip.

enced ^UL^a^’ ^t*¹‘^{s wea}P^on and sensor evolution influ- te_acted^{the des}'^{8n ofASW} ships. In 1945 the Navy XXi k ^t0 r^^{e ex}istence of fast submarines, the Type its _nev^ ^re9^u‘ting considerable increases in speed in "^b-K'|^SU^^aCe escorts: about 35 knots in a new ¹ ler (which became DL-1, the Norfolk) and

An amphibious ready group off the coast of Vietnam twelve years ago. These three ships, the I wo Jima (LPH 2), Thomaston (LSD 28), and Vancouver (LPD 2), have nominal speeds of 20 knots or more—much better than their World War 11 predecessors hut, in today’s circumstances, probably not good enough. It is in the successors to these ships that very high sustained speed may prove to be most valuable to the Navy.

30 knots in a new destroyer escort, compared to be­tween 21 and 24 knots in the war-built DEs. The old coastal escorts were to be substantially upgraded as well, from the 16 or 20 knots of wartime PC and PCE designs. In fact, the new DE was not even built; the Fletcher class DDE conversions were regarded as an interim substitute; and the new PC became the Dealey class (which was later upgraded to a DE desig­nation). All of these ships were armed primarily with the 800-yard Weapon Alfa. Through the late forties and early fifties they began to receive the first gener­ation of ship-launched ASW homing torpedoes, which could make up in large part for low escort speed; and over a quarter century Asroc and LAMPS completed the process. Thus, the major speed consideration in such current ocean escorts as the Knox class is the ability, not to outrun fast submarines in rough water, but to keep up with those ships they are in­tended to escort. Moreover, as escorts have grown in size, the material sacrifices involved in maintaining 28 or 30 knots have diminished.

All of this would appear to leave one aspect of escort burst speed out of consideration. An escort re­quires a considerable speed margin over her charges if she is to be able to carry out any detached missions and then return to the main body. Such missions might include, for a convoy escort, covering a strag­gler, rescuing survivors from a sunken ship, or prose­cuting a relatively distant submarine contact made by SOSUS or by a patrolling airplane. Unfortunately, high burst speed is extremely expensive, and the longer the weapon range in the escorts, the less the chance of missing a submarine through the escort commander’s unwillingness to detach a ship. This does not solve the problems just mentioned, but until escorts became plentiful toward the end of World War II, we didn’t solve it then either.

As electronics become less expensive, as terminal guidance techniques improve, as sensors grow in sophistication, it seems likely that high short-term speed will become a less useful tactical asset.

However, there is an important range of naval missions in which what matters is placing forces at a

Th'^s

can almost replace a number of slower units.

to

given point in short-order—not weapons, but men, so that terminal guidance is of lesser import. Moreover, in many cases it is essential that the forces be able to loiter at the point they have reached, often for some considerable time. All navies share a coastal patrol mission, yet it is impossible for most of them to afford large numbers of patrol craft. But if the craft have a good turn of speed, relatively few of them, centrally stationed, can cover a coast, provided they are alerted by some efficient sensor and com­munication system. For example, a major new mis­sion of the Royal Navy is to cover the North Sea oil rigs, even though there is no possibility of maintain­ing a large patrol force on station. If it is assumed that likely intruders will be unable to exceed twenty or thirty knots, and that efficient air cover can be sure of detecting them an hour short of their targets, then a force of sixty-knot hydrofoil boats becomes useful. Indeed, aircraft might be preferable except that a ship or a boat can carry boarding parties, re­pair crews, and so on; peacetime operations often re­quire something far short of what the airplane can hope to do, which is no less than to destroy the in­truder. Moreover, the seaborne force can stay on sta­tion when aircraft cannot. In any event, the Royal Navy decided recently to buy a 45-knot hydrofoil from Boeing for this work. It is interesting that even for this role, the first five ships they put on the job, the Island class patrol vessels of about 1,250 tons, have a top speed of only 16 knots. But, with their trawler-style hulls, they can maintain that speed in the rough North Sea when nominally faster vessels are reduced to a crawl.

A peacetime role peculiar to the U. S. and Soviet navies is the “tattletale,” a shadower of enemy fleet units. For the U. S. Navy, their function is to pro­vide early warning that Soviet units attempting to execute a “D-Day Shootout” have launched their missiles. In the Soviet case their task appears to be mainly to identify the most important ship within a U. S. formation, for the information of Soviet missile launchers. In both cases the shadower requires high speed, both burst and sustained, as she must be able to maneuver in company with the ships she is shadowing. In such a role, a ship is far more useful than an airplane because of her endurance and her ability to take station on the object of surveillance.

However, it seems likely that U. S. interest in such craft will decrease now that it has become evi­dent that the main launch platforms of Soviet anti­carrier forces are aircraft and submarines. A few years ago some of the fast Asheville class gunboats were as­signed to tattletale missions in the Mediterranean. But they have been decommissioned as the relevance of such a role has come into question, and most have been discarded.

Strategic Mobility

The classic naval asset is sustained, or strategic mobility. Indeed, strategic mobility was a prime in­centive for the adoption of steam turbines in capi^ta ships as long ago as 1906. Compared to the then- standard reciprocating engines, turbines permits higher reliable cruising speeds, albeit at a cost in ru^c economy. It is worth noting that the U. S. Navy- which thought in terms of Pacific (i.e., very long- range) operations, delayed its adoption of turbine⁵ precisely on grounds of fuel economy, or endurance- The German interest in.diesel power for their surfo^ce ships before World War II had similar roots; and ⁰ course so does the large U. S. investment in nuclei power.

High sustained speed also offered defensive advan­tages against submarine attack, and these still hold* Even with the advent of long-range submarine- launched missiles, most of the world’s submarine⁵ (and most of the Soviet Navy’s) are armed with tor­pedoes only, and such ships find it difficult to close with fast targets. Moreover, the faster a submarine ¹⁵ forced to move, the more noise she creates; hence th^e less useful her own sensors are and the smaller h^ef chance of remaining undetected prior to making ^atl attack.

High sustained speed is of defensive value eve¹¹ against missile-firing forces, because there will st> be delays before one can get off a missile strike First, reconnaissance forces must locate the targ^et’ then a strike must be arranged, and in such a fa⁵*¹ ion, if at all possible, to produce a saturation effe^ct' Therefore the strike platforms, whatever their nature have to sail, or fly, into the best possible position • The faster the target, the less the time available f°^f pre-strike preparation. An optimum strike may, ¹ fact, become impractical. In any case, high sustain speed minimizes the exposure of a valuable ship t0 attack, and so in itself improves the odds f°^r survivability—if the target does not have to rerna^|(1 in the danger zone for an extended period.

Another great advantage conferred by h‘£ strategic mobility is a kind of multiplier effect- single unit can move so fast that it can occupy sever*¹ well-separated positions in rapid sequence, and ⁵

type of argument was of little consequence prior the advent of aircraft carriers; but the combination ¹ carrier air group range and carrier speed made

sure

speed

quite important. World War II carrier air groups ^str*^ke targets about 150 miles away; carriers for ^r^^e'^{r consorts} could sustain speeds of 25 knots extended periods. In theory a carrier group could 90^^nt.^consecut*^ve dawn strikes against two targets ab ⁰¹¹ eS aP^art- An escort carrier group, cruising at 660^ ^ k^nots’ could strike at targets separated by miles; given three days, the relevant figures _tj°^Uld he 2,100 and 1,380 miles. Japanese reaction fou ^{eS Were} °^^ten such that strikes conducted three or ^Ur days apart on widely separated islands could be mered essentially simultaneous: the carrier war ^enorrn°usly successful partly because of the speed _c|_u ^which it was conducted. A reason for the short hav^*⁰⁰ str*^^e °P^erat*°ns in any one place might ^^een the desire to minimize the carriers’ expo- ^t0 counterattack. In fact, however, the carriers’

th ^Was used to multiply the number of targets ^{ey Cou}ld strike while they were in enemy waters for ^determined period, rather than to reduce their st L-^{SUre t0} attack hur a predetermined series of Pred^ ^^ten the length of their operations was qui |^Cate<^ ^mamly on fueling and reprovisioning re-

C '^s interesting that the carriers built for the war

similar speed.) Since World War II, the U. S. Navy has retained high carrier speeds for both strategic mobility and wind-over-deck. Strategic mobility has been so highly rated that efforts have been made to upgrade sustained escort performance to match. That is why the Spruances are designed to make 30 knots in rough water. However, they are not intended to make bursts of much higher speed.

"'en

erate _a •

air ^{d certain} amount of wind over the deck to assist frop- ^{C ln takin}S °ff ^ar*d landing. Winds coming tUr

reco'

^ where they might, carriers would often have to away from the fleet course in order to launch or ^Ver their aircraft, and then they needed a speed "'he ^nta^^{e C}° ^catck up to their consorts. (In fact, _SQrt^{n th}ey became the center of the fleet, their con- nsually changed course with them, and required

Wf.r ^^es‘8ned with such mobility in mind; but they ^e also given high speed because of a need to gen-

The old wind-over-deck argument survives in cur­rent proposals for very fast carriers (circa 100 knots), which would not require catapults to launch even conventional aircraft in a STOL mode. In this case, strategic mobility is often advanced as a supporting argument. But limits on the size of exotic ultra-fast ships suggest that such carriers may not prove terri­bly useful, unless they are produced in large num­bers. Another argument depends on a kind of aerial multiplier effect: ASW aircraft attacking a distant submarine can improve their payload if a carrier can move towards them while they are in flight, but only a really fast carrier can produce worthwhile results. For example, an ASW attack aircraft might cruise at 400 knots and spend one hour over the target, so that an attack on a submarine 200 miles away might require about two hours’ total mission time. During

and

stiH

tively. But when the weather breaks, the ship is

longer acquisition

the hour and a half spent enroute to and over the target, a 100-knot surface effect carrier could advance 150 miles toward the target, i.e., the airplane need carry only about three quarters as much fuel. Signifi­cantly lower carrier speeds would provide little ad­vantage in this context.

The multiplier effect carries one great caveat, which is too often dismissed: it works only as long as the fast units suffer few or no losses. An expensive but highly capable ship is an economy in peacetime; but when she sinks, all of her value sinks with her, perhaps from only a single hit. If one of four indi­vidually less capable (and less expensive) units goes, the force retains roughly three-quarters of its capabil­ity. This consideration is relevant, not merely to high speed ships, but also to many attempts to ex­ploit high technology for its multiplier effect (e.g., “one SQS-26-equipped escort can do the work of [de­leted] with SQS-4”—until she is sunk).

In a sense the multiplier effect is analogous to the theory that faster transport vehicles are more produc­tive than slower ones, and sometimes far more so if turnaround times are short: one 20-knot freighter can make two trips while a 10-knotter makes one, i.e., she is twice as productive. Often the conclusion is drawn that one 20-knot freighter is equivalent to two 10-knot ships. But that is not necessarily so. For one thing, fuel expenditure and other costs do not quite follow productivity. For another thing, the faster (hence, larger) ship may not be able to get into a port that a slower, smaller one can enter.

An important potential use of the multiplier theory is in ASW. Since the survival of the sub­marines’ target is regarded as being far more impor­tant than the immediate destruction of the sub­marines, surface ASW ships are employed chiefly to screen high-value ships. How effectively they can do so depends upon, among other things, how deep such a screen can be. As submarines become faster, and as their weapons grow in range, screens must be deployed farther and farther out, and this requires more escorts to cover a longer perimeter. The only solutions appear to be greater effective radius per es­cort, e.g., via LAMPS (technological multiplier ef­fect); or effectively more escorts via the multiplier effect of high speed. Unfortunately most submarine detection by U. S. forces is acoustic, and fast and noisy often appear to be synonymous. So a ship can listen or she can move rapidly, but she can’t do both at the same time. However, proponents of very fast ASW ships suggest intermittent sensor operation from these ships in the slow, quiet mode. High speed would be used between these “drifts” either to reach other search positions or to bring weapons to bear on submarines already detected at very I⁰⁰? range. In theory a three- or four-fold speed advantage over submarines should make the latter essentiall) static with respect to the ASW attack craft.

Such “sprint and drift” tactics are not new; the) were widely practiced by hydrophone-equipped craft- such as the 110-foot U. S. sub chasers, as early ^aS World War I. The operative point at that time ^vvaS that a hydrophone was useless while the sub chaser⁵ engines were running. The boat had to drift to 1^|S ten, and then sprint at full speed to maintain an ap preciable average speed of advance.

The high search rates claimed for “sprint drift” would seem useful in barrier patrol operation⁵- such as in the Greenland-Iceland-U. K. Gap.

It might be argued that aircraft have far higher search rates than ships have; but ships can use larg^ef sensors than aircraft can, and above all they can e* ecute very long missions. In bad weather neither ship nor airplane may be able to seek submarines eff^e<-' with her convoy, while the P-3 probably is not. O^r’ if the foe has a patch of clear weather from which ^t0 shoot, the ship, on station, can provide some protec tion. The patrol plane, at her base, can provide none- Unfortunately, the fastest of the exotic hull fori¹¹⁵ begin to approach aircraft characteristics; that ¹⁵ ’ they suffer from poor mission duration at high spe^e ' Yet “sprint and drift” operation envisages high A- escort average speeds. The average speed of advan^L’^L' of a force crossing the Atlantic may be 20 knots. Th^L sprint and drift escort may go 80 knots. In eff^eCt' maneuvering relative to the force, the very fast A- craft would travel several times as far as that for^ce’ and that at her greatest speed; even so, she won spend the same amount of time at sea. Fuel con sumption being what it is likely to be at such sp^ee ’ can she do it? The drift phase also presents proble^nlS’ for most of the proposed craft derive much of the^,r sea-keeping ability from their high speed.

if)?⁰

Modern missile attack boats show analogous ^c°ⁿ^ siderations. Faster boats can cover larger areas fro**¹ central base; as long as it is assumed that they ^wl suffer few losses, their speed can be traded aga^,n numbers. Moreover, attack boat speed reduces ex'P¹^ sure to countermeasures, the success rate of which ¹ likely to depend more on a boat’s duration of e*P sure than on any details of her characteristics. H° ever, to a considerable extent the boat’s weap^ characteristics can be traded off against her sp^ee just as speed in the boat can yield flexibility, so longer range in the weapon. (On the other haⁿ missile range requires more effective tar? sensors, generally sensors outside ^

miles from the continental United States; and amphibious convoys might require more

boat ) c; , ,                                                                               .

Cra^ similarly a carrier armed with 750-mile air-

tjj_a ^Can strike many more points in a short time ^tan °ne armed with 400-mile aircraft—and tha ^{<ln lrn}P^rovement would be far more significant ⁿ that attainable by a 10-knot ship speed dif- ^terential.

A

•s i-u °ⁿ^ ^C^^e £^reat advantages of strategic mobility gtea ^3t ^^e*ⁿ8 ^at>le ^t0 move material en masse over ^'stance in time to affect developments ashore. _Cati ^ ^t^^le distances are really great, slow movements ^{e r}*diculously lengthy. For example, Pacific 7 5Q₀landing^{s we}re made at distances as great as

slow than a

l_e$s month to waddle to them at 10 knots or J_t j Coring which time a great deal could happen. Pbib ^{n<> sur}P^r*^se rhat a major goal of postwar am- _mUt'^0us development was the 20-knot force (7,500 |jL , ^ln ^ days). These points gain force in view of hou_r^ European scenarios, in which days or even <)ui_re ^1X1 *®bt ^we^ be crucial; the 20-knot force re- a_Ssu^eS.^ab°ut a week to cross the Atlantic. However, of 1 ^rrUn^ ‘•hey could carry the fuel, a 100-knot force ^rfce surface effect amphibious ships could cross in

Equipped with the long-range SQS-26 sonar, a Knox class frigate launches an Asroc against a submarine some miles distant. Such sensors and weapons have “largely eliminated" the need for "high tactical speed to close the target. ” Yet, the question remains, how does an escort commander with 27-knot ships screen the 33-knot container ships or aircraft carriers he is charged with protecting?

under two days. It might be argued that aircraft would do even better; but they are far less efficient than even the exotic ships, and in addition they re­quire elaborate landing and servicing facilities which might be among the early victims of a Soviet attack.

Moreover, a 100-knot amphibious force would re­store to seaborne forces that advantage over forces moving on land which they enjoyed so effectively in the times of which Mahan wrote. Such forces could be particularly useful in operations around the pe­riphery of the Soviet-held Eurasian land mass. They might tie down large numbers of enemy troops and masses of material which would have to cover alter­native landing points. Only very effective enemy in­terior communications would solve this problem; and current overland transport technology gives little hope in that direction. Certainly helicopters and air­craft cannot move enough fast enough to do the trick. In effect, until the force was committed, a single very fast amphibious force would be equivalent in threat value to several slow ones.

The scenario envisaged is closely analogous to that of May and June 1944, when the Germans had to position their forces in northern France to counter the anticipated Allied landings. The area over which they had to spread forces was set by the arc Allied amphibious forces could reach after an overnight voy­age from England. Anything more distant would give the Germans time to shift their forces. Then a significantly faster amphibious force might have threatened a significantly larger sector of the conti­nent’s coast—and might have thinned German forces, or induced the Germans to hold even more in reserve than they did.

Such a specialized ultra-fast amphibious or trans­port force would require specialized escorts, or at least major investments in self-defense, requiring very special systems. It is important to recognize that, in view of current and prospective weapon and sensor developments, it might not be substantially more immune to attack than a 20- or 30-knot force, the advantage gained from reduced exposure not­withstanding.

An ultra-fast task force presents a somewhat simi­lar advantage in the cold war context. There is al­ways a high probability that a crisis will erupt somewhere far from U. S. naval forces—a probability which cannot but grow in an era of shrinking num­bers of U. S. ships. Crises can develop extremely rapidly and, as in the European war, the delay of a week to permit a carrier task force to transit may be unacceptable. However, the current alternative, to move land-based aircraft into an area, is impractical: it depends, for example, upon the availability of friendly bases, and even then the aircraft have no ability to sustain operations without a massive— usually nonexistent—stockpile of weapons and spare parts already in place. Naval forces, by way of con­trast, are self-sufficient, at least for short times. For example, a quick-reaction 100-knot intervention force could operate in an area for the several days required for more powerful—and more con­ventional—forces to appear. The recent Iranian rev­olution is a good example.

In this case it was not so much the speed with which the crisis developed but the inability of the U. S. government to decide upon a course of action which reduced actual available force time. Moreover, the Administration apparently feared that to begin to move carriers from the Seventh Fleet would be to telegraph its intention to intervene, and so either to indicate low confidence (from the Shah’s point of view) or excessive aggressiveness (from the rebels )• Once a decision had been made to make a show or force, there was too little time to do more than send some unarmed F-15 fighters—a gesture almost uni­versally derided. A very high-speed task group would have made a rather better impression—but at a very high purchase cost, for relatively little combat cap³' bility per dollar. Note, too, that it would be neces­sary to buy an entire task group (indeed, several) be­cause the value of the ultra-fast ships would be ⁱⁿ their sustained group transit speed.

One final point is worth making. It may be that very fast commercial ships will prove well worth­while. In that case, just because high speed provides little or no immunity, it will be necessary for the Navy to think seriously about escorts—or about the practice of World War II in which convoys were passed from one escort group to another during ³ transit. Although very fast warships are not so very useful in themselves, it is not at all inconceivable that 80 or 100-knot freighters may pay off hand­somely, especially in view of modern containerized cargo technology, which reduces sharply the tim^e needed to load and unload the ships. After all, th^e Maritime Administration has been among the spon­sors of SES projects.

Costs and Benefits

High speed has always been expensive: in conven­tional hulls it requires large engines with large fu^e appetites, and sacrifices in all other qualities ^c° match. Sometimes the engines are inefficient at any­thing but high speed, so that strategic mobility suf­fers. As we have seen, new exotic craft are so ineffi­cient at anything but high speed that for them 1° speeds are nor even considered normal forms of op^ef' ation. The great triumph in their design is th^£ achievement of substantial range at high speed; bu^c unfortunately in many of the applications which tad be envisaged, the endurance required is measured nO^c so much in distance as it is in time. The fast ad¹ phibious, transport, or intervention force is a signifi cant exception.

Most current hydrofoils and surface effect craft at^e able to carry significant payloads only because the) are built on aircraft rather than ship lines, whit means little space for the vessel’s operators, main^te nance crews, and spare parts, and little survivabifi^ in the event of damage. Hence, even if they can b^e

not take

into account the very different cost per ton

°f the

conve

ls k tHcntion weapon and aircraft fuel stowage. It _a ^ ⁿ° means clear that a fast platform capable of ⁿⁱⁿg ten or twenty aircraft in one wave, but not

e Celled frequently, such craft may find extended P^erations (e.g., sprint and drift cover for conven- •onal forces) difficult to maintain.

■            We have seen, a great virtue of ultra high speed lo ^{ltS mu}^^t*P^^er effect, an effect valid so long as

Ses are small. However, fast craft almost by their li^^tLJ^re produce considerable noise, and this noise is y to make them targetable by submarines using ^ery long-range weapons—weapons the fast craft, in ^{W c}heir low payloads, may be unable to counter ^ Actively. Nor does ;_{t seem} likely that a lightly- ^{Ul C} hydrofoil or surface effect ship would be able to , . ^{1Ve a} single missile hit. A larger conventional P might have far better survivability simply be- ^{Use s}he is more heavily built or because the missile ^ud hit randomly on her much longer hull, and

■            f Wt’h miss a vital spot. Moreover, the larger vit 1 ^^{ams some}-survivability from duplication of aff ^S^^st:erns> whereas the smaller exotic ship cannot

*^)r the weight involved. Nor can she afford sig- ant armor, even of the anti-splinter variety, kj ^e sea-keeping ability of a hydrofoil, and proba­n ^t^^at °f a surface effect ship, suffers catastrophi- y if she is forced to slow sharply, say as a result of _v- ^lne damage—or even of engine failure. Merely by fa ^ ^^{Cr S}*^Ze’ ^{a convent}‘^onaI ^ship may well suffer

ess if she is forced to go dead in the water for a fime.

seems important to keep in mind that one of the ^at Psychological appeals of exotic craft is that they e ar to offer great economies. A PHM carries so abl ^arrnament at such good speed even in consider- sea states; and she is so small too! Surely size l^uates with low dollar cost; surely a 220-ton PHM lch can wipe out a 6,000-ton destroyer is well ^rthwhile. The trouble is that the argument does

PHM and its exotic cousins, as compared to ^enttonal ships. Just as the exotic ships occupy a t\y - P°*^nt *ⁿ technology and performance be- in ^{en S}^'P^{S ar,}d aircraft, they occupy a midway point in ^C°^St P^{er un}‘^r weight. Small is by no means always

“expensive

e '60-knot carrier involves similar misconcep- i ^s- It seems to many that carriers are expensive _Cau_s^{USe the}y are large, and that they are large be- _er^j^e efodern aircraft require big catapults and pow- _tL ^arresting gear. Surely any means of avoiding heavy fixed structures must reduce carrier size,

cost. The trouble is that carrier size is also a matter f ■        ■              •

ot air wing size and aircraft maintenance— ^ot to rr

lai« i *° ^means clear that a fast platform capable of of maintaining or rearming them, is terribly useful. Moreover, it would seem that flight deck operations with a 100-knot wind passing over continuously might present problems.

On the other hand, if the 100-knot logistic force is worthwhile, then it becomes necessary to provide with it 100-knot escorts. Presumably an important element of the trade-off calculation involved is the cost of the escorting force—which will have rela­tively low capability, yet very high cost. Similarly, a sprint-and-drift barrier force requires frequent re­plenishment and possibly a continuous stream of fresh crew; and the hidden support cost may make the entire concept uneconomical.

In many ways the greatest defect of ultra-high- performance craft would appear to be not an inability to cross an ocean and thereafter perform a mission in a short-sea area. Small, fast vessels can do that. Rather, it is their inability to perform a mission, such as screening other ships, while so moving across the ocean. Unfortunately it is still the case that high short-term speed is perceived as an obvious benefit, requiring no further analysis. Thus the rise of the PHM program and then its abortive demise on cost grounds; and thus the remaining fascination with the surface effect ship, whose high speed is often adver­tised as a means of restoring to us the upper hand in ASW.

It is extremely unlikely that analysis of the sort presented here will ever overcome the kind of ex­citement that very high speed vehicles appear to arouse. However, it is by no means clear that, in the context of current and future budgetary problems, the Navy should be investing heavily in operational craft which, though perfectly operable, have little or nothing to do with its primary wartime missions.

The prognosis, then, is that observers of the naval scene will continue to find U. S. backwardness in the matter of ship speed bothersome; that programs like the PHM will continue to be funded on an intermit­tent basis—and that the chief buyers of very fast craft will continue to be minor navies, seduced by what amounts to nautical sex appeal. If we look at the new Krivak class, it would appear that even the Soviets seem to know better by now.