8

Submarines

EARLY POST-WAR THINKING concentrated on the ‘Intermediate B’ class with High Test Peroxide (HTP) propulsion derived from the German ‘Walter’ system. An ex-German Type XVII, U 1407, was used for trials as HMS Meteorite.¹ An early British study was for a 1700-ton twin screw boat with 6000shp on each shaft giving a top speed, submerged, of about 21 kts. It was hoped to lay down the first boat early in 1947 for completion in 1950. By 1948 it was realised that there were too many unknowns to go ahead with operational HTP submarines, and it was decided to build an experimental craft. Later a second boat was added, probably when the need for fast ASW training became apparent.

Explorer, for a short time the fastest submarine in the world at about 27kts. She and her sister were extremely valuable in developing tactics against fast submarines. The machinery was very noisy and they were sometimes referred to as ‘sirens under the sea’. (MoD)

U1407, an ex-German Type XVIIC submarine, was recommissioned as HMS Meteorite during the British development of HTP propulsion. The boat is seen here at Barrow-in-Furness in a dock now converted into an attractive museum. (W Cloots)

Construction of these experimental craft was justified on three grounds:

To prove British HTP machinery.

To investigate the manoeuvrability and control of very fast submarines.

To study ASW against fast submarines.

The British experimental boats Explorer and Excalibur were to complete in 1956 and 1958 and well before this it was clear that their primary role would be ASW training. In order to arrange the HTP stowage and the coolers, a deep section shape was adopted with the outer hull under-slung from the pressure hull. The main tank capacity was limited to 9 per cent reserve buoyancy instead of the usual 16 per cent, making them poor sea boats. They had one tank forward, two aft and an amidships tank either side fitted with a Kingston valve. Appendages were done away with as far as possible – there was a single anchor without a capstan. The bridge structure was the minimum for surface navigation – low and hence wet – and accommodated a single periscope, an induction pipe for the diesel, battery vent, indicator buoy and the HTP expansion chambers. There was no Snorkel (‘Snort’).

For surface propulsion they had a single diesel as used in the ‘U’ class driving electric motors. The diesel was in the fore ends to obtain longitudinal weight balance, taking the place of the torpedo tubes in these unarmed vessels and, for the same reason, the battery was well forward. All HTP equipment was grouped together at the fore end of the unmanned turbine room, reducing the risk of leaks which could cause fires.² Turbine controls were grouped on the fore side of the forward bulkhead of the turbine room, close to the switchboard and control room. The HTP was stowed in PVC bags contained in free flooding tanks outside the pressure hull. Endurance was 3 hours at full speed. Oil fuel was stowed inside the pressure hull, below the control room.

The propellers were large, though not as big as desired for the power, and projected 1ft 5in beyond the maximum beam, protected by guards in the form of stabiliser fins. There were problems in scaling model tests of high-speed submarines to full scale (see Porpoise class below) and at the Staff Requirement stage it was said to be sure that they would reach 25kts and that 27kts was probable – and achieved. The power absorbed in the coolers was also uncertain. On Explorers first trial her escort was a Black-woodwith a top speed of barely 27kts. However, she had not been warned what to expect and thought she could keep up with any submarine with only one boiler in use!

Trim and compensating tanks followed normal practice but special tanks were provided to compensate buoyancy and trim for usage of HTP. Considerable attention was paid to escape arrangements – this may seem ominous in the light of HTP’s characteristics but in reality it was the first outcome of a post-war review of escape equipment. Bulkheads were strong, there was one escape chamber and the conning tower could also be used, whilst the diesel room hatch was fitted for twill trunk escape. She had a very wide, flat keel so that she would remain upright if resting on the bottom.

Despite frightening their crews, the two boats proved invaluable in developing tactics for surface ships dealing with very fast submarines. Both the USN and Soviet navies abandoned their HTP designs, demonstrating the achievement of the UK design teams.³

Control

A submarine can only operate in a very shallow band of the sea. Wartime submarines had a safe diving depth only a little greater than their length. Explorer is quoted with a diving depth of 500ft, rather over twice her length and thanks mainly to a new steel, UXW (see Chapter 13). Even so, running at 27kts (45ft/sec) it does not take long to reach a dangerous depth.⁴ Emergencies include flooding or a jammed hydroplane – a hydraulic failure, running deep at high speed, does not allow long to change to the alternative system. Running fast close to the surface may also be hazardous as the boat may broach in front of a passing ship.

Even without emergencies control and manoeuvrability present many problems and in the early post-war years neither theory nor experimental equipment were fully developed. Very simply, the approach was to measure the forces and moments and how they varied on the hull, appendages and control surfaces of a model submarine both on a straight path and when manoeuvring. In these early years there was no way of controlling a model on a curved path and L J Rydill⁵ suggested the results could be obtained by running curved models on a straight path and this approach was used for the Explorer design.⁶ Later, the manoeuvring tank was built at Haslar, 400ft × 200ft and 18ft deep. It has a rotating arm to which models can be fixed for a curved path of up to 90ft radius some 9ft below the surface. The models may be upright to measure turning forces or on their side to represent diving manoeuvres. Later still, the Planar Motion Mechanism was developed in which a model could be pitched up and down whilst following a straight path. Very large free-running models under magnetic loop control may also be used in control experiments.

The results of these tests, the ‘derivatives’, were fed into the differential equations describing the path of the submarine. For very many years this work was led by a scientist at AEW, Tom Booth, who received little credit for his work. The obvious feature of control studies is in the positioning of the forward hydroplanes. The RN favoured bow planes which give better control, particularly at periscope depth. However, bow planes are noisy, degrading passive sonars, and for this reason the USN favoured planes on the sail. The arguments were finely balanced and the author well remembers one Anglo-US meeting at which the American officers argued in favour of bow planes whilst the UK representatives wanted planes on the fin.

Much successful work was also done in developing a re-cycle diesel plant in which the exhaust was replenished with oxygen from HTP and re-used.⁷

Silencing

New and modernised submarines would use acoustic homing torpedoes as their primary weapon, as would enemy submarines. The use of active sonar would be limited since its use would disclose one’s own position, and existing asdics (sonar) were not well suited to passive operation.⁸ Both of these factors led to a requirement for future submarines to be quiet, to protect them against enemy torpedoes and mines and to provide a silent platform from which the enemy could be heard without being detected by their passive sonar.

Propeller cavitation was a problem at periscope depth but in most cases could be avoided by going deeper where the greater pressure prevented cavitation. However, even at depth the low-frequency pressure pulses from propeller blades passing through a non-uniform inflow were a problem. It is not often realised that streamlining improves the operating conditions of the propeller and makes an important contribution to reducing propeller noise as well as reducing flow noise over the hull. Much had been done during the war to reduce machinery noise by improved design and manufacture and by resilient mounting, but a further major improvement was needed.

A submarine model under the rotating arm at Haslar. The arm had a maximum radius of 90ft and the forces and moments on the model could be measured while turning. For ‘rise and dive’ manoeuvres the model would be turned on its side.

(MoD)

Scotsman was used for many experiments in streamlining, and also for experimental propellers.

(D K Brown collection)

Modernising the Wartime Submarines

At the end of the war the streamlined Seraph had proved valuable as a high-speed target and five more of the ‘S’ class were similarly converted. Seraph was ‘padded’ so that practice torpedoes could be fired at her. Scotsman was given more powerful motors (3600shp) producing a maximum speed of 16.3kts and tried in various configurations, including one in which there was no bridge fin at all. She was a most useful test bed for many ideas and equipments including propellers.⁹

Eight of the wartime ‘T’ class were modernised between 1951 and 1956. They were lengthened,¹⁰ which provided space for two more electric motors, doubling their power and increasing underwater speed to 15.4kts, and an additional battery section of 6560 amp/hr cells. They were streamlined – gun and external tubes were removed, and a new, tall fin enclosed periscopes, snort, etc. They were armed with Mark 23 (Grog) AS torpedoes and were intended to have ‘Fancy’, an anti-surface ship weapon using HTP, but after the explosion in Sidon in 1959 ‘Fancy’ was withdrawn and they received the venerable Mark VIII torpedo.¹¹ Sonar fit comprised Types 186, 187 and 197.

Five riveted ‘T’ class were streamlined but not lengthened, whilst their battery was updated to 6560 amp/hr cells. Their speed was increased by 1.4kts and being fairly quiet, they were used mainly for ASW training. The fourteen surviving ‘A’ class were given somewhat similar treatment.¹²These updated boats gave valuable service and enabled tactics to be developed both for and against the first generation of fast submarines.

The Porpoise Class

By 1948 it was recognised that anti-submarine warfare (ASW) would be the primary role of the Royal Navy’s submarine force. Subsidiary to this, it was clear that they would have to spend much operational time providing targets for the training of surface ASW vessels and aircraft and the development of ASW tactics. In addition, it was thought likely that British submarines could operate against Soviet merchant ships supporting their army in the Arctic and possibly the Baltic and Black Sea. The German Type XXI had shown what conventional technology could do when required. The concept was brilliant and original but the individual techniques used for increased diving depth, greater battery capacity, more powerful electric motors and streamlined hull form were all well known.¹³ First priority was to use such techniques in modernising existing submarines and then to build a new design diesel-electric boat.

Six Porpoise class submarines, designed by R N Newton and E A Brokensha, were ordered in April 1951, and two more in 1954. They were a little bigger and somewhat shorter than the ‘T’ conversions, but improved design methods and UXW steel together with new structural design methods gave them a considerably increased diving depth. A model of the very long engine-room collapsed during tests at NCRE and a number of extra deep frames were fitted in the final design. They were exceptionally quiet for their day, mostly by careful attention to detail in the design and support of their machinery.

The engines were Admiralty Standard Range I (ASR I) designed at AEL, West Drayton and built first at Chatham Dockyard, an unusual case of ‘in-house’ machinery development. They were to prove very successful even though some of the design aims proved over-ambitious.¹⁴ Great attention was paid to habitability, including air-conditioning. The six bow tubes had rapid reloading gear so that a second salvo could follow very soon after the first, but this was heavy and not very reliable. Torpedoes could be fired at much greater depth than in previous classes. Submerged endurance was expected to be 55 hours at 4kts, about three times that of any previous RN boat.

The DNC, Sir Victor Shepherd, explained in 1955 that the submerged speed had come down from 17kts to 16kts, which he blamed on the use of reduced-noise propellers of lower propulsive efficiency and on caution in estimating full size performance from model tests.¹⁵ Submerged endurance on batteries had been further reduced following a re-assessment of auxiliary load by the Director of Electrical Engineering. At 4kts the auxiliary load was equal to the power for propulsion. In consequence, the nominal endurance at 4kts was reduced from 55 hours to 40 hours. Problems with the UXW steel, discussed in Chapter 13, led to a reduction in diving depth from 625ft to 500ft. In 1953 the design had been lengthened 4ft to accept an increase in machinery weight. Despite the fact that they fell short of performance targets, they were probably the best submarines of the day within NATO,¹⁶ and considerably superior to the Soviet ‘Whiskey’ class. They were deeper diving than either the ‘Whiskey’ or the German Type XXI (both 400ft), faster than the ‘Whiskey’ but 1kt slower than the XXI, and far quieter than either.

Taciturn, an early ‘T’ class conversion with enlarged battery and motors; streamlined for higher speed and quietness.

(D K Brown collection)

Andrew, an ‘A’ class boat streamlined but not given extra power.

(D K Brown collection)

They had noise-reduced propellers, benefiting from trials on surface ships and on Scotsman. Initially, these were very prone to ‘sing’, in which eddies are shed from the trailing edge, alternately from one side and then the other, exciting a resonant vibration of the blade which, in turn, makes the eddy shedding worse. It is said that Rorqual could be heard leaving the Clyde on the west coast of Scotland from a listening station on Long Island.¹⁷ The USN had similar problems and there was much interesting discussion on both theoretical and empirical solutions either seeking to control the eddy shedding or to prevent vibration by damping. Luckily, the Porpoise propellers had been designed before Conolly’s work on propeller strength (see Chapter 13) and were stronger than necessary. This made it possible to cut grooves in the blades, which were filled with a damping material which gave a complete cure.¹⁸

They had a good sonar fit aided by their low noise level and proved successful in a long service life. Top speed was about 16kts submerged and they had an endurance of 9000 miles on the surface.

Riveted ‘T’s were not suitable for the full conversion, but five – like Tireless shown here in 1954 – were streamlined, retaining their original machinery. They were quite quiet and useful for ASW training.

(D K Brown collection)

Oberon Class

The thirteen Oberons for the RN were updated Porpoises – one indication of a good design is that it can lead to an even better ‘Mark II’. The UXW steel used in Porpoise was difficult to fabricate and was replaced by QT28 quality which, together with further refinement to design methods gave a significant increase in diving depth. Special T bar frames were rolled and it was possible to have uniform size, omitting the deep frames which had been so inconvenient in the Porpoises. There were further improvements in silencing. The original sonar fit was the same as Porpoise but most were updated in the 1980s. Otus carried out trials with the Sub Harpoon SSM in 1989.

In addition to the RN boats there were six Australian, three Canadian, three Brazilian and two Chilean boats.¹⁹ The RN boats had a very long service life, approaching 30 years, but it was claimed that they were still the quietest submarines in the world at the end of their life.²⁰

Midget Submarines – Stickleback

In the early stages of the Cold War there was a fear that Soviet mini-subs might lay nuclear charges in harbours and estuaries. Four ‘X’ class midgets were built ostensibly for training in countermeasures, but it has recently been revealed that the RN had plans to return the compliment, laying either Blue Danube (20Kton yield, 10,000lbs weight) or Red Beard (20,000lbs) off Leningrad (now St Petersburg).

Porpoise, the first post-war operational submarine design. For their day, they were exceptionally quiet.

(D K Brown collection)

Orpheus. Very similar to the Porpoise but better steel and improved structural design gave the Oberon class a much greater diving depth. They were even quieter than Porpoise.

(D K Brown collection)

One of the four, Stickleback was sold to Sweden in 1958, returning to the UK in 1977 for display in the Imperial War Museum at Duxford. Sprat was lent to the USN for ASW training. Commander Richard Compton Hall, who commanded Minnow, says that the margin of safety was too small for peacetime operation.

The 1953 Design

By 1952 doubts were being expressed over the cost of the Porpoises and it was suggested by DN Plans that some at least of RN submarines should be of a simpler and less capable design so that more could be built with available funds. For the main ASW role in the Arctic a lower submerged speed would be acceptable (exercises showed speed to be of less importance than previously thought) and a shallower diving depth – 300ft was the maximum for air ejection of torpedoes. Since a single torpedo hit would sink a submarine, there was no need for a large salvo nor for rapid reloading. On the other hand, very elaborate fire-control gear would be needed and hovering gear was fitted.

There would be very little self-maintenance, in order to keep crew numbers down, which meant frequent visits to the depot ship so reducing the stores requirement. Four bow tubes with 10 torpedoes seemed adequate, together with one countermeasures tube (two countermeasures or anti-escort torpedoes). A 4in Mark XXIII gun could be mounted if required but was not carried in the ASW role. It was estimated that this required an extra 2ft on the length of the boat and, in all, some 40 tons on displacement.²¹ The smaller submarine resulting would be more suitable than an Oberon for Baltic and Black Sea work.

Staff requirements were issued in December 1952 (revised in 1953) and a number of design studies were completed. For the first time there was serious debate over one or two shafts. The single shaft had clear advantages in propulsion (c1kt) and would be quieter, but few operators and not many engineers were prepared to risk the lack of redundancy inherent with a single shaft. Stern tubes are virtually impossible with a single shaft. By late 1954 the intention was to build a first batch of six twin-screw boats followed possibly by nine single-screw versions. They were provisionally described as the Boreas class.²² The emphasis was on high silent speed but 10kts submerged was hoped for (8kts snorting) and 11kts on the surface. Endurance on battery was to be 30 hours at 4kts. The result was a submarine of 1100 tons. There was some thought of a later version with re-cycle diesels for use in the patrol area, snorting in transit. Habitability was much improved and cafeteria messing was proposed.

The 1953 design was stopped in 1955. It was argued that its reliance on frequent support from a depot ship was unacceptable in nuclear war. The concept of mass production in wartime was also dead. However, the First Lord, Quentin Hogg, visited Bath personally to apologise for the cancellation and wasted effort, a gesture much appreciated.

1953 Quiet Submarine Design. This study appears in the files of The Admiralty Experiment Works, Haslar, which carried out experiments in 1955 to investigate the efficiency of single- and twin-screw designs. A single-screw design proved to be more efficient.

(Drawing by John Roberts from original in PRO ADM 226/300)

The Type 2400 Submarine, Upholder²³

During the mid 1970s there was keen debate as to whether the Oberons should be replaced by another class of diesel – electric submarine or all the scarce funds be allocated to nuclear boats. SSN were more capable but expensive and the diesel boats might be more suitable in shallow waters and could meet the training role at low cost. As part of the debate five design studies were prepared with submerged displacement ranging from 500 to 2500 tons. They were all single-hull boats built of NQ1 steel and had a submerged speed of about 20kts.

After lengthy discussion a study of 1850 tons was selected for development under an Outline NST. It used existing weapons and sensors derived from UK, US and German sources. Further investigation caused a growth to 1960 tons. At the final NST stage three options were offered, one being the 1960-ton version. Option 2 was of 2250 tons with a superior weapon fit, including Sub Harpoon, costing 15 per cent more, while the 2650-ton Option 3 cost a further 5 per cent more. Option 2 was selected, with the directive to agree a compromise with Vickers (VSEL), who wanted to attract export orders with a 2500-ton boat having greater endurance and a more flexible weapon fit. Finally a compromise was agreed at 2400 tons. Sensors include a Thompson cylindrical bow array, Micropuffs passive ranging, flank array, sonar intercept with fire control developed from the DCB in the Trafalgar class. Overall, the weapon and sensor fit is more advanced (and more expensive) than a Trafalgar. The features of the new submarine are best shown in comparison with the highly regarded Oberon class of very similar displacement.

	Type 2400 Oberon
Submerged Displacement (tonnes)	2400	2450
Length (oa) (m)	70	90
Pressure hull dia. (m)	7.5	5.5
Diving Depth (m)	Over 200	Over 150
Patrol length (days)	49	56
Diesel power (MW)	2 × 1.4⋆	2 × 1.28
Propulsion motor (MW)	4.0	2 × 2.24
Max sub speed (kts)	20	16
Crew	46	71
Torpedo tubes + reloads	6+12	6+18

⋆ Supercharged Paxman Ventura.

The pressure hull of NQ1 is very nearly a uniform cylinder, tapering slightly aft, with internal framing of NQ1 or HY80. The dome bulkhead forward presented a difficult design problem as openings were needed for the six tubes of 0.8m diameter, two for air turbine pumps of 1.0m,²⁴ and a weapon loading hatch. A Finite Element Analysis supported by large scale model tests confirmed that the design was safe.

The hull form was optimised for submerged performance; it needed about twice the power of the Oberon on the surface but slightly over half the power submerged. Numerous model tests and simulations were run at Haslar to ensure good control, in particular the ability to turn at high speed without unwanted depth excursions and to level out after a depth change without overshoot. The hull, fin and casing²⁵ were shaped to give as uniform flow as possible into the propeller to reduce noise.

All machinery was carefully mounted to reduce noise transmission and to resist the shock of underwater explosions. The power-operated weapon storage and loading gear was seen as a particular success. The latest developments in noise reduction coatings were fitted. The fin supports six masts – two periscopes, two snort masts, EW and communications – whilst also containing a five-man diver tower. There are three main compartments with escape equipment in the end spaces and there are two decks forward of the machinery. Air purification equipment is of the highest standard. Great attention has been paid to ease of maintenance and upkeep. A reverse osmosis plant is fitted.

Upholder completed in 1990 followed by three more up to 1993 and they proved very successful once problems with their torpedo tubes were overcome. They were put up for sale in 1995 as an economy measure and eventually leased to Canada – who got a splendid bargain, although there have been problems getting them into service, possibly due to lack of experience with the boats’ equipment.

Submarine Escape and Rescue

Up to the end of the war, most submarine accidents happened in shallow water, often due to collision on the surface. A study of ocean depths showed that the continental shelf was rarely over 600ft in depth, shelving rapidly to the deep ocean from which there was little chance of survival. If a submarine is on the bottom and unable to surface it almost certainly implies that one or more compartments is flooded and exposed to sea pressure. While it is possible to design bulkheads to withstand the same overall diving pressure as the pressure hull, such bulkheads would be so heavy as to severely limit the capability of the submarine. In consequence, bulkheads are usually designed to take a much lower pressure and will fail at any greater depth, where there is no chance of survival.

Following the tragic loss of Thetis in June 1939, a committee on escape and rescue was set up under Admiral Dunbar Nasmith, but during the war little could be done to change procedures or equipment. In April 1946 a new committee was set up under Rear-Admiral P A Ruck-Keene, who had been a member of the Dunbar Nasmith committee.²⁶ Their report was most valuable and formed the basis for all post-war work in this area; in particular, it was recognised that the greatest hazard was whilst survivors were still inside the submarine and they should be under pressure for the least possible time and that removal of carbon dioxide was more important than supplying oxygen. At that time the normal method of escape involved flooding a whole compartment to equalise the pressure and then, one by one, ducking below a twill trunk to reach the open escape hatch, using the Davis escape apparatus on pure oxygen on the way to the surface. This meant that the survivors would be under pressure for a considerable time, under which conditions oxygen, nitrogen and, particularly, carbon dioxide can be lethal.

The four Upholder class were victims of the ‘Peace Dividend’ and deemed unwanted in the post Cold War era. They were exceptionally quiet and had an unrivalled weapon and sensor fit. They have been leased to Canada. (Mike Lennon)

A one-man escape tower was developed so that men would be under pressure for the least possible time and it was decided that free ascent should be adopted and taught. Lungs full of air under pressure have more than enough oxygen for the time to reach the surface; indeed the most serious problem was to breathe out fast enough to avoid damage to the lungs. A 100ft tower was built at Fort Blockhouse for training. Further attention was to be paid to air purification, studies of the USN escape chamber were initiated, and location devices, buoys, etc developed

Development of an immersion suit to keep survivors afloat, dry and warm was started but was not in service when Truculent was sunk in a collision with a freighter in the Thames Estuary on 12 January 1950. A Standing Committee On Submarine Escape (SCOSE) was set up in October 1951. A simpler One Man Escape Chamber (OMEC) was designed, with the aim that the time under pressure while escaping from 300ft should be less than 3 minutes. A Built In Breathing System (BIBS) provided pure air for those waiting to escape (an oxygen-rich system had been tried).

The USN escape chamber, which could operate to 850ft, was carried in Kingfisher (ex-King Salvor) from 1954 to 1959. The early Porpoise class had a mating ring and escape bulkheads which could resist the water pressure at 800ft. The chamber was abandoned due to the logistics of getting it to the scene in time and difficulty in positioning it on a sunken submarine.

By the early 1960s it was realised that free ascent was not limited to 150ft. Trained, fit men should be able to escape from 300ft or even 600ft. In May 1963 there was another review under Captain J S Stevens. This aimed at increased depth, escape tower and no twill trunk. Liaison with USN over the use of their rescue submarine (DSRV) led to the decision to abandon the rescue chamber. This review emphasised that submarines are war machines, for which a degree of risk was inevitable. They also considered means of blowing ballast tanks at depth without HP air. This usually involved the use of an explosive, such as cordite, to generate the large quantities of gas at high pressure needed to blow ballast tanks against the pressure in deep water. This high pressure gas had to be vented quickly while surfacing else it might rupture the tanks, sinking the boat again. Large freeing ports were needed. The strength of bulkheads was reviewed as was the performance of pumps. Early location was seen as vital, so indicator buoys were fitted with radio, D/F, smoke candles, and underwater telephone. Three trapped men escaped from Artemis the day after her sinking (1 July 1971).

The crews of nuclear submarines with reactor and air purification systems working could survive for a long time.²⁷ After 1963 thoughts were given to see if pressurisation be quick enough for free ascent from over 300ft. Tests were held at the RN Physiological Laboratory (RNPL) simulating escape from 300–500ft. In the Mediterranean, Orpheus in 1965 staged an escape from 480ft (keel 500ft). By mid-1970, instructors from the submarine HQ and training establishment HMS Dolphin at Gosport left Osiris off Malta at 600ft. Target times were 30 seconds under pressure with the tower flooded before pressurisation. Deeper trials have been carried out with specially-skilled men. The average, fit sailor has a good chance of escaping from 300ft and may even survive 600ft.

¹ D K Brown, Nelson to Vanguard (London & Annapolis 2000), p117.

² The risk of fires was indeed reduced but not abolished: not for nothing were the boats known as Exploder and Exciter!

³ One of the leading members of the team, Eleanor MacNair, has helped with this section.

⁴ At 30° bow down this would imply a vertical velocity of 22.5ft/sec.

⁵ D K Brown, A Century of Naval Construction, p315.

⁶ A curved model is part of the Science Museum reserve collection at Wroughton.

⁷ Eleanor Macnair (personal communication).

⁸ In 1951 when this author was serving in Tabard the First Lieutenant was devising an elaborate mathematical method of locating an enemy from passive observations.

⁹ Serious consideration was given to a new ‘trials’ submarine but with the increasing confidence in model tests and computer simulations the cost could not be justified.

¹⁰ Taciturn 14ft; Turpin, Thermopylae and Totem 12ft; Tabard, Tiptoe, Trump and Truncheon 20ft.

¹¹ ‘Fancy’ was a slightly modified Mark VIII adapted for HTP. On 16 June 1959 a ‘Fancy’ torpedo exploded aboard the submarine Sidon while she was alongside the depot ship Maidstone in Portland Harbour, and sank her.

¹² Alliance is preserved in this state on shore at the Submarine Museum, Gosport.

¹³ There is a parallel here with Warrior (1860) which also used conventional technology in a novel ensemble.

¹⁴ ADM 157/139 (PRO) includes a paper, originally Secret, detailing the way in which performance fell short of the original intention.

¹⁵ They had a very early design of reduced noise propellers; later designs did not lose in efficiency. Some of the problems of scaling from model to ship are explained in Appendix 2 on Reynold’s Number.

¹⁶ The USN Tangs were designed for 18.3kts submerged but only achieved 16kts. This was part of the evidence leading to a reduction in the design speed of the Porpoise. Tang could dive to 700ft. Caution is needed in comparing diving depths as it is not certain on what basis these were defined.

¹⁷ With later propellers, she was able to surface off the Statue of Liberty without being detected.

¹⁸ Most other classes were given a V-shaped trailing edge which, with experience, proved successful in controlling the shedding of eddies.

¹⁹ British sales successes post-war were the Whitby-Leander class frigates and the Oberons, both the best of their category and not cheap. Much the same may be said of the Vosper Mark 10. British Shipbuilders’ attempt at selling a cheap frigate may well have been mistaken.

²⁰ Onyx is preserved at Birkenhead, Ocelot at Chatham.

²¹ For a more detailed discussion of this design see: N Friedman, The Post War Naval Revolution, (London & Annapolis 1986).

²² ADM 205/106 (PRO).

²³ P G Wrobel, ‘Design of the Type 2400 Patrol Class Submarine’, Trans RINA (1985). Main source for this section, used with permission of RINA.

²⁴ Torpedo firing gear.

²⁵ A small GRP casing was thought desirable to shroud external fittings such as hatches.

²⁶ H J Tabb RCNC, ‘Escape from Submarines, A Short Historical review of Policy and Equipment in the RN’, Trans RINA (1975), p19.

²⁷ It is not easy to consider an accident which would keep an SSN on the bottom and leave many survivors. Flooding bow compartment is about all, which is what appears to have happened to the Russian submarine Kursk in 2002.