RN Subs

The History Of British Submarine Sonars

by Commander David Parry

The Early Years

The Fessenden oscillator is adopted and modified

Titanic. The name of this famous ship (or infamous, depending on the way you look at history) reverberates throughout the century since she sank in 1912. Her sinking was the instigator of many changes, developments and innovations not least the genesis of the US Coast Guard and SOLAS.¹ Among the innovations of how to detect obstructions at sea, like an iceberg, was one conceived by a Canadian born radio engineer, Reginald Fessenden working as a consultant to the Submarine Signal Company to enhance their system of underwater bells for shore-based stations, buoys, and light ships and for sound detection on ships.² It may well be that the Royal Navy had experimented with these underwater navigation aids for BR 3043 reports "a report dated 9 February 1909 stated that 'submarine sound signalling had been fitted in certain submarines and tests carried out with bells fitted on the Shambles and Tongue Light Vessels'."³ Fessenden's invention was an electro-mechanical oscillator, in effect a transducer,⁴ transmitting sound through the water at 540 Hz. He patented the oscillator in 1913 and trials of the system were an outstanding success.⁵

The Royal Navy was immediately interested and submarines began to be fitted with Fessenden hydrophones.⁶ But the Fessenden hydrophones were cumbersome, weighing 559 kg,⁷ so the Torpedo School was charged with developing them for submarine underwater signalling (in 1917 the work transferred to the Signal School).⁸ The work was started under the redoubtable Commander (later acting Captain) CP Ryan at HMS Tarlair, the Hawkcraig Admiralty Experimental Station, Aberdour. Ryan was very much an old-school retired Commander re-called to service and then promoted. He was not a scientist, and he knew little or nothing about sound theory or instrument design. Yet, with an enthusiastic if eclectic staff that included a totally blind man with 'absolute pitch', the elderly son of a celebrated historian, a famous violinist, a London theatre manager and two eccentric dogs.⁹ Nonetheless he had managed to get a variation of the Fessenden system to sea with trials in the submarine B3.¹⁰ (Another product of Ryan's work was a "much more sophisticated arrangement of five powerful and sensitive hydrophones by which they could approach an enemy and obtain her position without using the periscope.")¹¹ These arrays went into the R Class anti-submarine submarines of which 10 were completed just before or just after the end of WW1 but only two survived beyond 1923. However, they were not used to develop tactics for their intended role and the potential of the array was not explored. Later, the Germans used hydrophone arrays extensively; the Royal Navy not until asdic Type 186 in the 1950s.¹²

Ryan's work resulted in two new designs: an improved Fessenden which became Type 102; and a transmitting-only version that was designed to talk to submarines under tow. WW1 submarines, including the E Class and L Class, were fitted out with the Type 102 but research continued with upgrades until 1931 when the S Class were fitted with Type 106X¹³ operating at 1080 Hz.¹⁴

Early outfits had two 5 inch plate hydrophones of a new design (either a Mark II, IV or V) and tuned to 900 Hz that were fitted in the submarine's pressure hull, both forward with one on either side.¹⁵ By 1926, a third plate had been added, facing aft, "immediately abaft, or inside the after superstructure of the conning tower; it should, when possible, be placed not less than five feet above the pressure hull." ¹⁶

There were three principles behind the installation of this apparatus: safety, attack and navigation or tactical. For safety, it was considered possible to detect another dived submarine and so avoid collision. The attack mode was severely limited, and the submarine had to be swung across the bearing of the target to find the null point between the two forward hydrophones. Unsurprisingly, this was not considered to be very successful¹⁷ so the deficiency was rectified by the later installation of the Revolving Directional Hydrophones (RDH). The navigational use was for the detection of the submarine bells and the tactical was the start of sound telegraphy (S/T sometimes later called S.S/T or SST)¹⁸ whereby a submarine could both listen to the message and get a bearing on the transmitting submarine. The thought was that this would allow submarines to operate together in, for example, a patrol line.

Ranges out to 20 miles for SST were claimed but reception could be seriously affected by ambient or own ship's noise.¹⁹ The advice was for the operator to listen on all three hydrophones at the same time especially if SST was expected and some of the principles for a passive search housekeeping that would last well into the future were laid down. For example: slow speed to reduce flow noise; casing rattles had to be eliminated; machinery to be stopped (apparently the hydraulic system particularly interfered); and the operator was to be informed of course and speed changes and pump starts/stops etc.

In submarines, the Telegraphists were used to operate SST and the hydrophones and had the post-nominal HL, for Hydrophone Listener. There were two reasons to use the telegraphists: the transmissions used Morse code (the Morse for the letter 'F' was used for ranging) and the W/T amplifier was used to amplify the hydrophones signal. This meant that the hydrophone switchboard was co-located with the W/T amplifier although a pair of headphones was provided in the control room for the captain and later an extension listening station was in the fore ends to keep the operator away from the machinery noises²⁰ but it was a monotonous work resulting in operator fatigue and the necessity for frequent changes of operator.²¹ Submarines, of course, did not have large complements — the H32 had 42 crew members — so telegraphists probably found themselves watch and watch about. In 1920, such was the enthusiasm for asdics, that the General Service SD (Submarine Detector) branch was established being formed by selected seamen ratings under the age of 25.²² In submarines the job was still done by Telegraphists, called Telegraphist Detectors, and trained as asdic operators at HMS Osprey in Portland²³ which had been established as the antisubmarine school in 1924. But as late as 1937 sufficient numbers of suitable telegraphists could not be found; although it was hoped to resolve the situation by 1939!²⁴ The branches stayed like this until 1947 when both surface ship and submarine asdic operators became members of the Underwater Control (UC) branch.²⁵

The Revolving Directional Hydrophone

Towards the end of the war submarines began to be fitted with a set of revolving hydrophones positioned outside the hull. Initially this was supposed to be in the stem of the boat as shown, see Figure 1,²⁶ but this was amended to be on top of the forward casing as appears in Figure 2.²⁷ The apparatus consisted of two plate receivers, back to back, and connected by a rod. When either of the plates was pointing directly at the sound source there would be maximum movement on the rod and therefore maximum reception. Conversely, when both hydrophones were receiving the same amount of noise they would cancel each other out resulting in no rod movement and no reception. This was known as the 'minimum property' and was estimated to provide a bearing with an accuracy of ± 10°²⁸. The plate hydrophones were more sensitive and could detect sounds to three times the range of the RDH hydrophones. Even so, the RDH had detected surface ships up to nine miles.

The Royal Navy was immediately interested and submarines began to be fitted with Fessenden hydrophones.²⁹ But the Fessenden hydrophones were cumbersome, weighing 559 kg,³⁰ so the Torpedo School was charged with developing them for submarine underwater signalling (in 1917 the work transferred to the Signal School).³¹ The work was started under the redoubtable Commander (later acting Captain) CP Ryan at HMS Tarlair, the Hawkcraig Admiralty Experimental Station, Aberdour. Ryan was very much an old-school retired Commander re-called to service and then promoted. He was not a scientist, and he knew little or nothing about sound theory or instrument design. Yet, with an enthusiastic if eclectic staff that included a totally blind man with 'absolute pitch', the elderly son of a celebrated historian, a famous violinist, a London theatre manager and two eccentric dogs.³² Nonetheless he had managed to get a variation of the Fessenden system to sea with trials in the submarine B3.³³ (Another product of Ryan's work was a "much more sophisticated arrangement of five powerful and sensitive hydrophones by which they could approach an enemy and obtain her position without using the periscope.")³⁴ These arrays went into the R Class anti-submarine submarines of which 10 were completed just before or just after the end of WW1 but only two survived beyond 1923. However, they were not used to develop tactics for their intended role and the potential of the array was not explored. Later, the Germans used hydrophone arrays extensively; the Royal Navy not until asdic Type 186 in the 1950s.³⁵

Ryan's work resulted in two new designs: an improved Fessenden which became Type 102; and a transmitting-only version that was designed to talk to submarines under tow. WW1 submarines, including the E Class and L Class, were fitted out with the Type 102 but research continued with upgrades until 1931 when the S Class were fitted with Type 106X³⁶ operating at 1080 Hz.³⁷

Early outfits had two 5 inch plate hydrophones of a new design (either a Mark II, IV or V) and tuned to 900 Hz that were fitted in the submarine's pressure hull, both forward with one on either side.³⁸ By 1926, a third plate had been added, facing aft, "immediately abaft, or inside the after superstructure of the conning tower; it should, when possible, be placed not less than five feet above the pressure hull."³⁹

There were three principles behind the installation of this apparatus: safety, attack and navigation or tactical. For safety, it was considered possible to detect another dived submarine and so avoid collision. The attack mode was severely limited, and the submarine had to be swung across the bearing of the target to find the null point between the two forward hydrophones. Unsurprisingly, this was not considered to be very successful⁴⁰ so the deficiency was rectified by the later installation of the Revolving Directional Hydrophones (RDH). The navigational use was for the detection of the submarine bells and the tactical was the start of sound telegraphy (S/T sometimes later called S.S/T or SST)⁴¹ whereby a submarine could both listen to the message and get a bearing on the transmitting submarine. The thought was that this would allow submarines to operate together in, for example, a patrol line.

Ranges out to 20 miles for SST were claimed but reception could be seriously affected by ambient or own ship's noise.⁴² The advice was for the operator to listen on all three hydrophones at the same time especially if SST was expected and some of the principles for a passive search housekeeping that would last well into the future were laid down. For example: slow speed to reduce flow noise; casing rattles had to be eliminated; machinery to be stopped (apparently the hydraulic system particularly interfered); and the operator was to be informed of course and speed changes and pump starts/stops etc.

In submarines, the Telegraphists were used to operate SST and the hydrophones and had the post-nominal HL, for Hydrophone Listener. There were two reasons to use the telegraphists: the transmissions used Morse code (the Morse for the letter 'F' was used for ranging) and the W/T amplifier was used to amplify the hydrophones signal. This meant that the hydrophone switchboard was co-located with the W/T amplifier although a pair of headphones was provided in the control room for the captain and later an extension listening station was in the fore ends to keep the operator away from the machinery noises⁴³ but it was a monotonous work resulting in operator fatigue and the necessity for frequent changes of operator.⁴⁴ Submarines, of course, did not have large complements — the H32 had 42 crew members — so telegraphists probably found themselves watch and watch about. In 1920, such was the enthusiasm for asdics, that the General Service SD (Submarine Detector) branch was established being formed by selected seamen ratings under the age of 25.⁴⁵ In submarines the job was still done by Telegraphists, called Telegraphist Detectors, and trained as asdic operators at HMS Osprey in Portland⁴⁶ which had been established as the antisubmarine school in 1924. But as late as 1937 sufficient numbers of suitable telegraphists could not be >found; although it was hoped to resolve the situation by 1939!⁴⁷ The branches stayed like this until 1947 when both surface ship and submarine asdic operators became members of the Underwater Control (UC) branch.⁴⁸

The Revolving Directional Hydrophone

Towards the end of the war submarines began to be fitted with a set of revolving hydrophones positioned outside the hull. Initially this was supposed to be in the stem of the boat as shown, see Figure 1,⁴⁹ but this was amended to be on top of the forward casing as appears in Figure 2.⁵⁰ The apparatus consisted of two plate receivers, back to back, and connected by a rod. When either of the plates was pointing directly at the sound source there would be maximum movement on the rod and therefore maximum reception. Conversely, when both hydrophones were receiving the same amount of noise they would cancel each other out resulting in no rod movement and no reception. This was known as the 'minimum property' and was estimated to provide a bearing with an accuracy of ± 10°⁵¹. The plate hydrophones were more sensitive and could detect sounds to three times the range of the RDH hydrophones. Even so, the RDH had detected surface ships up to nine miles.

Figure 1: THE REVOLVING DIRECTIONAL HYDROPHONE
On the left the RDH is shown mounted above the casing at the stem of the submarine. The diagrams on the right show how the hydrophones need to be turned to determinebearing.

Figure 2: THE REVOLVING DIRECTIONAL HYDROPHONE

The RDH hydrophone can be seen ringed in front of the fin. This was an alternative position to that advocated in ADM 186/450 Handbook of Hydrophones in Submarines 1926 rather than the ADM 186/440 1924 position. The transmitting and receiving hydrophones are forward between the torpedo tubes and hydroplanes

The birth of the towed array?

The principal problem with hull mounted hydrophones was that own ship's noise and flow noise masked any detections and mariners were not too keen to be stationary while hunting submarines. At the suggestion of the Board of Inventions and Research (BIR), Ryan began investigating towing a hydrophone in early 1916. Others were also working on the problem, on 31 July 1917, GH Nash of the Western Electric Company claimed to have solved the problems of moving a hydrophone through the sea at speed without water noise, and how to hear and identify the direction of another ship totally submerged "or otherwise".⁵² He had developed the 'Fish' for the Anti-Submarine Division (he was reluctant to give it to the BIR because he had fallen out with them over a previous project). The 'Fish' had one bi-directional and one uni-directional hydrophone which rotated. Bearing was determined by the bi-directional hydrophone's minimum position and ambiguity resolved by the uni-directional hydrophone. There were other versions such as Cranston-Vanesbroeck's idea in 1915/16 which proved no better than that the readily available, petrol-filled hydrophone, (with no named inventor), and the Dawson Pendulum hydrophone which depended on the pendulum for stability.⁵³ It seems that Nash's invention, which was first tested in the swimming pool at Portland,⁵⁴ won the day, for 136 of his 'Fish' were initially ordered with an anticipated order of around 360 sets and Nash was awarded £3000 for his work.⁵⁵

But it was Ryan's 'Rubber Eel' that went into submarines. The Eel was 18 inches long by 3 inches in diameter and was omni-directional, the sound waves compressing the rubber body and passing through the internal jelly to the diaphragm where a microphone detected the vibration. It had a reel with 150 feet of cable mounted on the bridge rail and could be towed astern or over the side while the submarine was stopped. There is an indication, although no absolute proof, that the eel was towed dived.⁵⁶

Figure 3: THE LANCASHIRE FISH and THE RUBBER EEL
The Lancashire Fish is clearly much larger than the 18 inch long Eel and was a more sophisticated towed hydrophone. But it was too late to become operational during the war.

Research continued throughout the war on towed hydrophones resulting in an improved Eel, called the 'Porpoise', and eventually a sophisticated device called the 'Lancashire fish'. But none went into production before the war ended and the technology was not pursued further as was much of the research on hydrophones in favour of the advent of asdic.⁶²

The Inter-War Years and The Birth of Asdic

The conception and gestation period

The conception of asdic is murky and its gestation muddied. They involve an eclectic mix of British, Canadian, French and Russian scientists and engineers working in a wide variety of research establishments and companies. The three names most quoted are: Constantin Chilowsky, the Russian émigré who proposed an echo-ranging system using high-frequency sound waves; Paul Langevin, a leading French scientist who identified and introduced the efficacies of the quartz crystal to the transducer; and Robert Boyle, a Canadian scientist and protégée of Ernest Rutherford who persuaded Boyle to work for the BIR where he was charged with developing the work of Chilowsky and Langevin. It was Boyle's recognition of the wartime urgency and focus on producing a practical device that could be used at sea as soon as possible, rather than seeking scientific perfection, that wins him the accolade of being the "Inventor of Sonar".⁶³ Boyle made the breakthrough of getting an asdic echo from a submarine at 500 yards in 1918, but this used a separate transmitter and receiver. Three months later he was achieving the same results with a single transducer transmitting through a dome similar to the submarine RDH canvas covered, metal-lattice-framed dome which, it was discovered, caused only a small signal loss. The first ship-fitted asdic, Type 111, was fitted in HMT Ebro II just five days before the end of the war.⁶⁴ Unlike the other principals, Boyle did not take out any patents and later disappeared back into relative obscurity as an academic at the University of Alberta.

Secrecy

Following Boyle's breakthrough and then quickly following the end of WW1, everything to do with asdic now became shrouded in the utmost secrecy even to the extent that quartz was referred to as 'asdevite'. This concealment continued until 1929 when the Naval Staff decided that the term 'asdics' could be openly used65 but that installations still remained a secret and any reference to them had to be concealed as a secret in double envelopes.⁶⁶ This led to some farcical implications of the policy as Mayers relates. On one occasion he was given a double envelope marked secret. Furtively reading its contents it told him that "Submarines L53 and L543 [both asdic fitted submarines] had left Gibraltar and would arrive at Devonport on March 10". He then read the very same words in the Times newspaper.⁶⁷

The name 'asdic' only first came to the public's attention in December 1939 when Winston Churchill used it in the House of Commons. Mr RW Chapman, of the Clarendon Press, wrote to the Secretary of the Admiralty asking for clarification on behalf of Oxford Dictionaries. The Director of the Signal Department replied saying that the word derived from "the first letters of the words Allied Submarine Detection Investigation Committee, a body which was formed during the war of 1914-1918, and which organised much research and experiment for the detection of submarines".⁶⁸ However, as Hackmann points out, there is nothing in the archive to suggest that this committee existed. Rather, Hackmann avers, it almost certainly was derived from the title Anti-Submarine Division-ics.⁶⁹

In 1920 the 'Bonar Law Committee'⁷⁰ proclaimed that asdics and hydrophones were considered both as anti- and pro-submarine devices⁷¹ and with a reorganised Department of Scientific Research and Experiment (SRE, Admiralty) development continued to produce, by 1922, the surface ship Types 111 then 112, 114 and 115 retractable asdic sets.

The Development of Submarine Asdics: Types 113, 116, 118 and 120

The Admiralty did not wait for the Ebro II trials to even start before ordering 20 Type 111 asdic sets in June 1918 rather, they had put their faith in outboard trials that had been conducted in two whalers, Icewhale and the Cachelot. The P59 had the distinction of being the first warship to be fitted with an inboard asdic in 1919 and about the same time as the whaler trials it was achieving detection ranges of 1100 yards. The set was standardised into the Type 112 with a retractable cylindrical canvas dome shrouding a single ply quartz transducer operating at 20-50 kHz. The transducer was hinged so it could act as an echo sounder and the set was fitted in the ships of the first A/S Flotilla in 1920-21 to give them a maximum asdic-operating speed of 12 knots.⁷²

As the first ships were being fitted with the next version, Type 112, work started, in 1921, on the first submarine asdic - the Type 113 which was to be a Type 112 turned upside down so that both the dome and the 15 inch, four-ply transducer with an extra quartz layer and mild steel inter-plate, operating at 23.7 kHz,⁷³ were above the casing of the submarine although it was all retractable into a watertight compartment. This position gave the transducer a 320° listening arc, with a blind 40° created by the fin, and it enabled the submarine to operate the asdic when dived and bottomed, but not, of course, when on the surface. In 1922 the first asdic was fitted in the submarine H32 (Lieutenant WAC Dickson) for a lengthy period of trials.⁷⁴ This was Type113A, and H32 was the only submarine of her class ever to be fitted with asdic.⁷⁵ One of the first things the trials found was that the canvas dome was totally unsatisfactory and it was replaced almost immediately by a thin copper dome and then, after 1928, by mild staybrite steel. The copper dome was unpopular with the submariners of the day because, true to the traditions of the service, it had to be polished!⁷⁶

Figure 4: TYPE 113 ASDIC: SIDE VIEW; AS FITTED IN H32: CROSS SECTION
The hatch that can be seen on the left-hand drawing is probably from a later version as it is not visible on the H32.

The trials were Lengthy and extended trials followed covering the many potential uses of this new technology: station-keeping with another submarine; active range on the target; avoiding anti-submarine attacks; SST with both ships and submarines; and firing on an asdic bearing.⁹² One particularly interesting, and pertinent, trial was conducted a few years later when the H32 was invited to see if she could penetrate the columns in a convoy and make attacks using hydrophone effect and asdic. The H32 would detect the convoy by periscope and then go deep to conduct an attack by hydrophone effect (passive sonar in today's parlance) confirming range of the target by an active transmission. It was concluded that she did this "without any great difficulty" although the detection ranges in comparison to the later asdic sets were very low, 1200-1400 yards and self-noise was a big problem. The H32 also transmitted fairly frequently and these transmissions were intercepted by the convoy escorts. But the conclusions also warned against getting too close to the target because of the difficulty in differentiating between contacts. It also emphasised the necessity to go at slow speed to avoid self-noise interference.⁹³

With the experience of the first destroyer asdic Type 114, modifications were incorporated, and the set became known as Type 113X to go into the submarine X1 (Commander Phillip Phillips) in 1923.⁹⁴ Further modifications to the Type 113X (which was now operating at 21-25 kHz and shared the Type 102 transformer)⁹⁵ created the Type 113C which was fitted in the 12

Group III L Class submarines in 1925. By 1926 seven submarines had been fitted. In the L Class submarines, however, the set was positioned aft of the fin and was intended to have an all-round reception but the development programme for a sound reflector arrangement to achieve that ambition was being developed for the destroyer Type 115. This programme, however, was abandoned and so Type 113 ended its long operational life with the 5th Training Flotilla in 1937 as obsolete with outdated electronics.⁹⁶

The set was initially designed to use in the active mode for determining the range of a target but it was found to act as an excellent hydrophone and so by the mid-1920s it was used more often in the passive mode taking over from the older hydrophones.⁹⁷

With the advent of the O Class submarines designed for long-range operations (the Far East was in mind) work started in 1923 on the replacement for Type 113A even while it was still undergoing sea trials in the submarine H32. The replacement, known as Type 116, could only be operated with the submarine dived but not bottomed with the exception that the Oberon's set was modified so that it could also be used on the surface.⁹⁸ This asdic was not a success and it is not too hard to realise why. It had a long vertical tube that extended through the pressure hull at both the top and bottom of the submarine; it leaked, and the asdic office, invariably had water splashing about. True to the eccentricities of many submariners, one First Lieutenant carried an umbrella!⁹⁹ The upper transducer was covered in a galvanised steel dome and although the set was in many ways similar to the Type 113 it had more advanced electronics and a heterodyne unit for earphone amplification. Transmission was still by a Morse key but a phonic chronoscope, which was stopped and started electromagnetically, was introduced for ranging.

While being built the first three O Class submarines Oberon, Oxley and Otway had an asdic office built into them and the dome seatings were machined ready, but the Type 116 was not fitted until the submarines had been handed over between 1926-27.¹⁰⁰ By that time 10 submarines were fitted with asdic.¹⁰¹ The inadequacy of this asdic was shown in the Oberon in September 1939 when it contributed to the submarine been declared unfit for operations.¹⁰²

The Type 116 had conical reflectors to provide all-round echo detection and listening, but these reduced its range dramatically and were scrapped along with the upper transducer and long rod leaving just a lower transducer projecting from the keel. Its operating frequency was modified to 10 kHz and the dome covering the keel transducer was changed to staybrite steel. The electronics were also cleaned up.¹⁰³ In 1929 this modified set, became the Type 118, and was fitted to the second batch of O Class, the Parthian Class, K26 and the Rainbow Class

(nominated Type 118A).¹⁰⁴ Asdic Type 118 then became the standard inter-war asdic set and unlike some of the Type 113 fitted submarines remained operational until 1937. Some concern was expressed that this set may become damaged in shallow water especially when the submarine was forced deep causing a recommendation that a mechanism to raise it within 30 seconds should be developed.¹⁰⁵ There is no indication this was done, but Type 118 was soon superseded by Type 120 and then Type 129 which were both keel-fitted.

February 1932 saw the introduction of the Type 120.¹⁰⁶ This was an improved Type 118 with almost identical directing gear and dome but placed more efficiently closer to the bow. By 1938 all submarine asdics were operating at 10 kHz,¹⁰⁷ which now became the standard frequency until the end of the 1950s as it was a better frequency for underwater signalling.¹⁰⁸ The Type 120 was further updated with a 4-ply quartz transducer and electronics from the small ships' Type 123.¹⁰⁹

Type 120 was fitted in the River Class submarines, where it was known as Type 120A, some of the earlier S Class submarines¹¹⁰ and the minelaying submarines of the Grampus-class.¹¹¹ McKenzie gives a good example of the versatility of this asdic set when, in the days before radars in 1936, the Hong Kong-based River-class submarine Rainbow led the old destroyer HMS Bruce " through a long, narrow, tortuous Channel, with no buoys or lights to assist navigation." She did this by using her Type 120A asdic in the 10 kHz active mode transmitting continuously to get ranges of the numerous rocks and hazards.¹¹²

Echo Sounders

In the beginning submarines had to rely on the leadline for taking soundings. The C27 (Lieutenant Sealy) had to use hers in the most stressing of situations as she fought to make her escape from the Gulf of Riga in October 1917 following the German invasion of the Gulf of Riga Islands under Operation Albion. Having been in action against the main German units, the battleships Kronzprinz and König, and having torpedoed the transport SMS Indianola, she was feeling her way across the 'four fathom bank' south of Osel Island when she wrapped her leadline around her propeller. In the best traditions of the Submarine Service her leadline was replaced by wheel spanner and a string.¹²⁰

Clearly it was not a good situation when submarines could only find the depth by touching the bottom when dived or using a leadline on the surface. In 1920 the then Captain Martin Dunbar-Nasmith therefore invented a submarine sounding apparatus. No record of what this apparatus looked like or how it worked has survived but it must have been successful for it was fitted to 133 submarines and Dunbar-Nasmith was awarded £600 for his invention.¹²¹ Not all submarines however, were fitted with the Dunbar-Nasmith apparatus. For example, the submarine X1 was fitted with a Kelvite Mark IV sounding machine supplied by Kelvin Bottomley & Baird Ltd in 1922.¹²² This could only be used on the surface with the use of a boom to keep the sounding wire clear of the submarine. Operationally it was clearly inconvenient.

The first half of the 19th century saw some experiments with the use of explosives to determine the depth of the sea but they were inconclusive.¹²³ Thereafter development of the echo sounder paralleled asdics, starting with Fessenden. Although the German, Alexander Behm¹²⁴ took out the first patent on an echo sounder, it too relied on an explosion like the earlier efforts whereas the first commercial echo sounder using an oscillator was installed on the SS Berkshire in 1924 by Fessenden's company, the Submarine Signal Company.¹²⁵

Asdics needed to find a way of automatically determining the time between transmission of the signal and reception of the echo. The problem was the same for echo sounding, but more so because of the short duration between the transmission and reception and so, with the obvious commercial potential of an echo sounder, this development work took priority in the 1920s and the work moved from the Sheldon research site to the Admiralty Research Laboratory, Teddington, (ARL) in the austerity years following the war although its results were used in parallel with the development of asdic.

Out of various ideas, that of BS Smith whose echo sounder operated at ultrasonic frequencies prevailed, and in 1925 the licence to manufacture was given to Henry Hughes & Son (now Kelvin Hughes). The submarine Rover was the first naval vessel to be fitted with a production Type 752 in 1930 but it wasn't until six years later that a rotating stylus recorder was introduced.¹²⁶ This echo sounder was marketed he commercial version being identified for use in submarines.¹²⁷

It was this submarine echo sounder that created a milestone in asdic history when it was used to find the RMS Lusitania. In June 1935 the treasure-hunting company Tritonia Ltd. commissioned the SS Orphir, fitted with the British Admiralty M. S.II and a French Langevin-Chilowsky echo sounder to find the wreck.¹²⁸ The difference was that the British echo sounder could make a record of the search. The Admiralty echo sounder found the wreck most successfully which was then dived on later in the year although they were unable to recover anything of value.¹²⁹

Figure 7: BRITISH ADMIRALTY MS II ECHO-SOUNDER TRACE OF RMS LUSITANIA

The trace shows clearly the Lusitania standing above the seabed which has been scooped away on one side of the ship. The break in the trace is where the surveying ship, SS Orphir, went astern and the disturbance interrupted the sounding.

Type 752 was followed in 1937 by the Types 753 and 754, a deep, 130 fathoms, and shallow echo sounder respectively. By 1938 the Type 758N, with a quartz transducer was being supplied by Henry Hughes for all new construction submarines and in readiness for WW2 although it was used with caution operationally as it could be intercepted by hydrophones and asdics tuned to the same or near frequency. A 'snap-sounding' could counter this but the echo sounder was liable to give false readings from fish and water variations.¹³⁰ This echo sounder had a few modifications during the war the most notable being the development of long lasting impregnated paper.¹³¹ It was to be standard fit until it was replaced in mid 1960s by Type 773, a deep echo sounder, and Type 776 a shallow echo sounder which went into all classes of submarines. The Swiftsure Class, for example, had one Type 773 transducer and four Type 776 transducers, one in the keel, and three upward looking: one forward, one on the top of the fin and one on the rudder.¹³² In the early 1970s Types 778 10KHz, deep echo sounder and 780 were introduced all being produced by Kelvin Hughes.¹³³ The Type 780 was developed as a surveying echo sounder operating at 30 Khz and used for upward looking. Today's Astute Class have two Type 790 echo sounders which still record on paper rolls but there are seven transducers with an Intelligent Switch unit beneath the Recorder for transducer selection. Two 10kHz transducers in the keel are for deep soundings and they can operate in a continuous mode or 'single ping'. There are also two 33 kHz transducers also fitted in the keel for shallow water and a further three upward -looking transducers on the forward casing, top of the fin and top of the rudder. The Type 790 is to be replaced by the Type 800 made by SEA Ltd.¹³⁴ It's a long way from leadline to the Type 800's display screen.

Type 752 was followed in 1937 by the Types 753 and 754, a deep, 130 fathoms, and shallow echo sounder respectively. By 1938 the Type 758N, with a quartz transducer was being supplied by Henry Hughes for all new construction submarines and in readiness for WW2 although it was used with caution operationally as it could be intercepted by hydrophones and asdics tuned to the same or near frequency. A 'snap-sounding' could counter this but the echo sounder was liable to give false readings from fish and water variations.¹³⁵ This echo sounder had a few modifications during the war the most notable being the development of long lasting impregnated paper.¹³⁶ It was to be standard fit until it was replaced in mid 1960s by Type 773, a deep echo sounder, and Type 776 a shallow echo sounder which went into all classes of submarines. The Swiftsure Class, for example, had one Type 773 transducer and four Type 776 transducers, one in the keel, and three upward looking: one forward, one on the top of the fin and one on the rudder.¹³⁷ In the early 1970s Types 778 10KHz, deep echo sounder and 780 were introduced all being produced by Kelvin Hughes.¹³⁸ The Type 780 was developed as a surveying echo sounder operating at 30 Khz and used for upward looking. Today's Astute Class have two Type 790 echo sounders which still record on paper rolls but there are seven transducers with an Intelligent Switch unit beneath the Recorder for transducer selection. Two 10kHz transducers in the keel are for deep soundings and they can operate in a continuous mode or 'single ping'. There are also two 33 kHz transducers also fitted in the keel for shallow water and a further three upward -looking transducers on the forward casing, top of the fin and top of the rudder. The Type 790 is to be replaced by the Type 800 made by SEA Ltd.¹³⁹ It's a long way from leadline to the Type 800's display screen.

Figure 8: THE COMMERCIAL VARIANT OF TYPE752
The brochure cover. Inside it says that the MV Asturias was the first British	Type 752	Type 773 that replaced the Type	The latest echo sounder, Type 800

Asdics were a learning process

As asdic was developed, primarily for surface ships, during the interwar years the search for understanding as how to use the new technology and the natural insecurity in such a situation is all too evident in the documentation of the time. The influence of using asdic in an active mode, as in surface ships, and the propensity to manoeuvre numbers of ships in formations clearly permeate the thinking is how to best optimise the use of asdics in submarines.

The primary use of submarine asdic to benefit the attack as a complement to the periscope (not yet for a fully blind attack) prevails throughout much of the documented discussions. In second and third place are normally the avoidance of A/S vessels and then the use of SST for station keeping or communications in some form.¹⁴⁰

An exception to this order of priorities is in a December 1931 letter to the Admiralty from the Rear Admiral (S), Rear Admiral Charles Little¹⁴¹ just a couple months after taking up his appointment. He reveals the indecision as how best to use asdic despite asdic having been at sea in submarines for almost 10 years. He says: "the extent of the potential uses of the asdic are not sufficiently realised or appreciated". He then calls for a coordinated investigation of the potentialities of asdic. Little was a pre-WW1 submarine CO. During WW1 he had been either a Commander or Captain (S) and in that capacity he would have been aware of the introduction of the Fessenden hydrophones, their developments, and use in the SST role. But, between March 1919 and September 1931, when he became Rear Admiral (S), he had been mostly in Fleet, big-ship appointments rather than in a submarine appointment. This experience, or lack of interim submarine experience, may explain why the first priority for investigation was "To facilitate co-operation between Submarines whether on the surface or submerged." ¹⁴² This mindset of submarines cooperating is in the mode of Fleet manoeuvres rather than Doenitz's later Wolfpack operations and it is based upon active transmissions for SST. It is taken to the extreme a few years later, for, in 1936 instructions for a detailed choreography of a submarine flotilla formation of eight submarines is published.¹⁴³ This was despite divisional tactics having been discontinued many years earlier so clearly there was still some confusion.

Two reports following up on Little's letter remain to give us some idea of how COs are beginning to use the technology. A report from the CO of L27 in response to Little's letter indicates that he used his Type 113 mostly in a passive mode except for when he was forced deep and then used an active range to press home his attack. A common use was to try and jam the active asdic-fitted ships with the submarine's active transmission.¹⁴⁴ A later report recounts something of a more formal investigation or trial between the submarine L27 and the 6th Destroyer flotilla. Again, the CO had good results when using it as an active intercept set.¹⁴⁵

In 1935 the Rear Admiral (S), now Rear Admiral CP Talbot, again rewrote the priorities into an order that would prevail into WW 2: attack, anti A/S, SST, and navigation. Asdics had now adopted the 10 kHz as a standard frequency that would be used by the wartime Type 129.¹⁴⁶ By 1938, with the clear advent of war, and although there was a shortage of telegraphists to operate the asdic sets, asdic was being used confidently in a passive mode to help the attack solution. Propeller revolution counting was particularly commented upon as producing good results (75.6% within 1 knot). Similarly, submarines were getting up to 1 ½ minutes warning of an attack by an A/S vessel and although blind fire had not been particularly progressed, the use of SST was particularly accomplished: out of 520 exercises in SST communication 490 were successful.

Typical 10 kHz sonar performance at this time, (but not yet Type 129), is shown at Table 1. Submarines would be detecting surface ships passively at ranges often comparable to, or better than, visibility in the North Sea.

Table 1: SUMMARY OF 10 KHZ ASDIC DETECTION OF VARIOUS TARGETS BY SUBMARINES
TARGET		Speed of Detecting Vessel
		Submerged 0-3 knots		Submerged above 3 knots
TYPE	Speed	Echo Detection	H. D. Detection	Echo Detection	H. D. Detection
A	Below 16	Not applicable	13,600	Not applicable	9700
	16-25	"	18,100	"	11,500
	Above 25	"	No data	"	No data
B	Below 16	2100	5600	3600	8700
	16-25	2100	3400	3200	9500
	Above 25	No data	24,000	No data	No data
C	Below 16	1900	4400	2500	8100
	16-25	1700	7900	1500	8700
	Above 25	No data	No data	No data	No data
D	Below 16	2300	4000	2500	5100
	16-25	3200	 6300	2600	6200
	Above 25	No data	8300	No data	No data
E	Below 16	2900	4000ble	2200	3600
	16-25	1900	4100	2600	4600
	Above 25	Â	Not applicable	Not applicable	Â
F	Below 16	3400	5200	2900	7900
	16-25	No data	No data	No data	No data
	Above 25	No data	No data	No data	No data
G	Below 16	No data available			6200
	16-25	No data available			6200
	Above 25	No data available			6200
Types of target are:- A - Target vessels of any description with a close screen (HT Ranges only B - Battleships, Battlecruisers and Aircraft Carriers C - Cruisers D - Destroyers and Sloops E - Submarines on the Surface F - The depot Ships, Merchant Ships, Trawlers and Miscellaneous Vessels

With this background the Submarine Service entered WW2.

The Wartime Asdics Type 129 and Type 138

The asdic that was to become familiar to all the WW2 submariners was the outstanding Type 129. First trialled behind a dome in the front end of the keel of HMS Seawolf in 1937, in 1938 it was decided that the set would be adopted as the standard submarine set.¹⁵⁶ This was, of course, just in time for it to be available for all the new construction submarines of the T Class, U Class, and V Class and their participation in WW2.

Operating at the now standard 10 kHz it was fitted in a cylindrical cage with a streamlined dome underneath the forward torpedo tubes at the forward end of the keel with an electric motor inside a watertight tank that was itself inside the pressure hull. This enabled the oscillator unit to be pulled inside the submarine for maintenance, repair or exchange. The Torbay (Lieutenant Commander Anthony Miers) achieved this at sea by isolating the fore ends, putting a pressure in the compartment to counteract sea pressure, opening the hatch over the tank withdrawing the oscillator and re-shutting the hatch. With the oscillator repaired, the process was repeated in reverse. All this happened in the Mediterranean, in April 1941, at night, on patrol in enemy waters. As Chapman points out, others would have waited until they were back in harbour but to fix it in this way was indicative of Miers' determined attitude.¹⁵⁷

Figure 9: ASDIC TYPE 129 FITTED IN HMS SENTINEL

Type 129 with Type 138 were the standard sonars in British submarines throughout WW2

The Type 129 was gyro stabilised and intended as an attack set. Like its predecessors, it was often seen for its SST capabilities where, in the early versions, transmission was by Morse key and ranging was done by chronoscope but the sets were soon modified to have a range recorder, A/S3, with automatic transmission. There is little evidence to suggest that its use in this role was often, if at all, practised but it was certainly used on occasions, especially in the Mediterranean. However, from empirical, operational experience it was realised that the set acted as an excellent slow-rotating, all-round directional hydrophone and when it was coupled to the hydrophone arrays it was particularly good in the passive mode at 10 kHz. This capability introduced the art of determining a target speed by propeller revolution count¹⁵⁸ it also meant, however, that submarines needed to reduce their self-noise. The biggest culprit in this area were the submarine's own propellers and trials had been conducted shortly before the war to try and reduce this noise source. One trial in two S Class submarines involved using a Gill "hydraulic propulsion mechanism" ¹⁵⁹ which appears to be shrouded, helicoidal propellers, developed during WW1 by a Major Gill.¹⁶⁰ The shroud was effective at lower speeds but was abnormally noisy at higher speeds.¹⁶¹ Another was to change the asdic motor's alternator. It was found that the Germans could detect the set's alternator on their hydrophone arrays. When the alternator was changed the set became Type 129K and it was trialled in the captured German U-boat, U570, HMS Graph. The trial concluded that the set was comparable with the German hydrophone arrays. ¹⁶² Another solution, not to reduce self-noise but to avoid it in the U-class, was to put a second listening position in the fore ends as far away as possible from the diesel engines when the submarine was on the surface. But a much more comprehensive solution came with the T Class submarines which had their machinery resiliently mounted.¹⁶³

Extensive trials were conducted to determine the capability of the Type 129 in all its modes. It was found to be a very capable asdic intercept set achieving ranges out to 10 miles on a transmitting ship if the set was tuned to the frequency of the ship's transmitting asdic. SST, considered to be a very important aspect of asdic, was particularly successful with 490 out of 520 attempts being successful under 50,000 yards. The average range between two dived submarines over 137 exercises was 14,600 yards. Even with the submarine sitting on the bottom SST communications were maintained out to three miles.¹⁶⁴ With the submarine dived and at under 3 kts, in the asdic, transmitting mode, a merchant ship could be detected at 3400 yards and a submarine at 2900 yards if they were below 16 knots. Hydrophone effect ranges were out to between about 13,000-18,000 yards on an escorted target and 4000 yards on a submarine.¹⁶⁵

Because of its position the Type 129 had a blind stern arc so from 1943 a passive, manually-trained, listening-only, hydrophone called Type 138 was added to cover the blind arc and complement Type 129.¹⁶⁶ In the T Class the Type 138 was fitted on the after casing between 9 and 10 tubes. This position meant that the set had to be accommodated in the engine room where of course there was little spare room anyway and so its intrusion caused considerable problems.¹⁶⁷

The Type 129 went through many modifications one of which was to add a Mine Detection Unit (MDU). The MDU probably came about as a result of the mining of HMS Hunter off the coast of Spain during the Civil War which triggered research into mine detection.¹⁶⁸ It first went into the Triad in 1940¹⁶⁹ and then two further mine detection sets were developed during the war, the first, in 1943 the Type 148 operating at 40 kHz and the second, later towards the end of the war, the Type 152X, which was trialled in the Alcide. However, the first was not really used and the second did not get beyond its prototype stage.¹⁷⁰

The Type 129 was a most versatile asdic, its qualities ably exemplified by the experiences of wartime COs:

Lieutenant Hugh McKenzie¹⁷¹ relates, when as CO of the Thrasher in 1941, and off Benghazi in the Mediterranean, he also used the MDU to keep the boat away from minefields that lay either side of the Benghazi approach channel which he was trying to penetrate.¹⁷² McKenzie also used it successfully for SST communications with the Upholder at a range of eight miles in the Gulf of Taranto.¹⁷³ He also tried and make contact with the Upholder (Lieutenant Commander David Wanklyn VC) on 14 April 1942 after hearing her taking an intensive depth charging in the Gulf of Sirte. Alas, there was no response, Upholder had been sunk.¹⁷⁴

Commander Ben Bryant used the MDU this to effect in the Safari. As he was creeping up the coast of Yugoslavia in October 1943 he tracked the minefield which was to seaward of him.¹⁷⁵

Lieutenant Commander Mervyn Wingfield, CO of the Taurus, having sighted a Japanese U-boat while on the surface in November 1943, had to go deep because of the light and then used his Type 129 in the hydrophone effect or passive mode to complete the attack by firing a salvo of six torpedoes - one of which hit and sank the submarine I34.¹⁷⁶

Perspicaciously, Lieutenant James Launders, CO of Venturer used his Type 129 for an hour, again in the hydrophone effect mode, while he stalked the U-864 off Norway on 9 February 1945 before making history by being the first and only submarine so far to sink another submarine while both were dived.¹⁷⁷

The 129/138 combination continued at sea until the early 1950s being fitted in submarines of seven other different nations.¹⁷⁸ After the war the Type 138 passive set was given an active capability and renamed 138F. This set was now capable of transmitting at 14kHz for echo-ranging and SST and passive listening at between 500 Hz to 4.5 kHz. However, submarine operations were soon to change after WW2 and it was realised that something more sophisticated was needed¹⁷⁹ and that would need scientific and technical research.

Post WW2 and the start of the Cold War

The scientific community re-organise for the Cold War

The first thing to happen following the war was that the research organisations reorganised. The association between Portland and asdics/sonar had started as HMS Sarepta, the Experimental Hydrophone Establishment in 1917 which became the antisubmarine establishment under Captain S D Tillard, a survivor of the Hogue sinking in 1914 and Jutland. He was in command of HMS Osprey, an old whaler and leader of the 1st Anti-Submarine Flotilla in 1924.¹⁸⁰ By this time the antisubmarine school had 13 officers training officers and asdic operators at Portland and HMS Vernon¹⁸¹ but in 1927 the school became a permanent establishment ashore at Portland.¹⁸² Tillard argued for the co-location of the various research establishments and a closer relationship with his antisubmarine school. This proposal received a sympathetic hearing and in 1927 the first Chief Scientist, B S Smith, was appointed,¹⁸³ an appointment that heralded, with the exception of a short move to Scotland during WW2, an association between Portland and sonar research until the end of the century. On return to Portland in 1946 the establishment was named the Anti-Submarine Experimental Establishment and then from 1947 the Underwater Detection Establishment (UDE). In 1959 it was decided that Portland would also become the home of scientific research into weapons, detection and control systems and the Admiralty Underwater Weapons Establishment (AUWE) was formed embracing UDE and the Admiralty Gunnery Establishment. At its height it had 93 Naval staff and 1,741 civilians of which 462 were of professional grades and 346 craftsmen.

Figure 12: UNDERWATER SYSTEMS RESEARCH ORGANISATION AND HISTORICAL ROADMAP FROM GOVERNMENTAL LABORATORIES TO INDUSTRY

The Admiralty's research establishments went through a number of reorganisations with their growth following WW2 and the increased research requirement for the Cold War. Equally, the establishments then had to go through a further reorganisation with the end of the Cold War and the shrinking research budgets.

Over the following years the Ministry of Defence's research organisations up and down the land were to go through several organisational iterations and mergers. First the Admiralty's research establishments were merged to form the Admiralty Research Establishment (ARE) in 1984. In 1991 as the "Peace Dividend" began to gain ground in Whitehall, all the main MoD's establishments were merged and split, the major part forming the tri-services Defence Research Agency (DRA) which was created as a separate trading organisation under the MoD. The Agency model was deemed successful and all the remaining parts of the research and test and evaluation organisations were merged to form the Defence Evaluation and Research Agency (DERA) in 1995. This was the prelude to full privatisation of the majority of this organisation and renamed QinetiQ with a much reduced government owned capability being secured as the Defence Science and Technology Laboratory (DSTL). The underwater research portion of QinetiQ, with roots going back to UDE, was sold in 2009 and now operates successfully from premises in Winfrith, Dorset.¹⁸⁴

The post-war improvements

Compared to the effort that had gone into developing surface ship asdics during the war submarines were something of a Cinderella. The Type 129 was fitted in all wartime submarines complemented by the Type 138 in 1940 and apart from a few minor modifications like the Type 152 prototype fitted in the Alcide late in the war which added a transducer operating at 30 to 65 kHz for mine detection, no new asdic set was developed. Even the Type 152 went no further than the prototype. >So, following the war, an endeavour was made to improve Types 129 and Type 138 with Types 169 and 168 respectively, but they were not great improvements.

Figure 11: HMS AMPHION WITH (PROBABLY) AN ASDIC TYPE 169 DOME FOR'ARD

Amphion

Another sonar that went no further than the prototype was the Type 171. This was a derivative of the surface ship sonar Type 170 or 'Four Square' after the construction of the transducer. It was housed on the casing in the fore part of the submarine under a large dome and a prototype was fitted in Thermopylae but like the Type 152 it went no further.¹⁸⁵

Before things went much further contention was to intervene.

Asdic changes its name to sonar

As the research establishments reorganised themselves to take on the Cold War challenge, something of a far more fundamental and contentious change was happening: asdic was to change its name to sonar.

The name 'sonar' originated from Frederick Linton Hunt of the Harvard Underwater Sound Laboratory in 1942 as being analogous to radar, the term 'Sound, Navigation and Ranging' came later.¹⁸⁶ The contentious issue of renaming asdic as sonar was first raised in a letter by Captain AS Russkell, (Russell?) Captain of the Anti-Submarine School, then based in Dunoon, in December 1944.¹⁸⁷ He wrote to a wide audience seeking their opinion on changing the name from "ASDIC to SONAR". His reasons were the confusion between antisubmarine, which was identified by 'A/S', and asdic because asdic sets were named starting with the same nomenclature, 'A/S'. This was simply too much for many officers as Russkell points out: "a non-specialist Officer spoke of Asdic when he meant A/S and although this was pointed out to him, a similar mistake was then promptly made by a senior member of the A/S Branch who spoke of A/S when he meant Asdic". ¹⁸⁸

The responses received by Russkell displayed some entrenched prejudice "The adoption of the USA vocabulary is to be deprecated and should never be resorted to except when really necessary." ¹⁸⁹ The antipathy was unanimous and some could barely conceal the emotion generated. After a rant in which he invoked tradition and the insult to those who had developed asdic over the past 25 years, Captain Clarence Howard-Johnston, Director of the Anti U-Boat Division asked "How can we hope to inspire anyone with a word like "Sonar"?" and Captain Neville Prichard, Director of Anti-Submarine Warfare, wrote cuttingly: "there is no justification whatsoever for re-naming Asdic "Sonar", and that it would appear to D.A/S.W. that the staff at HMS Osprey could well be reduced by the author of this nonsense."¹⁹⁰ Nonetheless, the change in terminology went ahead albeit not until the early 1950s.¹⁹¹ But, as the files reveal, the reference to asdic was still being used into the early 1960s. 1965 seems to be a watershed year from whence the term sonar became standard terminology enabling the retronyms passive-sonar and active-sonar.

Four new sonar sets for the diesel submarine fleet: Searcher, Attacker, Watcher and Scanner

Figure 13: OBERON CLASS SONAR FIT

In August 1940 the German Type VIIC U-boat, U570, surrendered to aircraft and was subsequently towed to Iceland. The submarine was to be commissioned in the Royal Navy as HMS Graph. But first she was inspected to reveal her secrets. One of those secrets was her hydrophone array called Gruppenhorchgeräte (GNG). While, during the inter-war years the British focused on asdics and the active transmission to detect submarines, the Germans had put their efforts into continuing their development of passive-listening hydrophones arrays that had started back in 1914.¹⁹² This work had culminated in WW2 U-boats being fitted with increasingly sophisticated hydrophones arrays. By the end of the war the Germans had developed what was effectively a bow array system with the eponymous name Balkon (Balcony).¹⁹³ The U570 had arrays but not Balkon. Nonetheless, and for unknown reasons, the British did not get around to investigating U570's GNG until May the following year and even then nothing was much done to take advantage of the technology. The Americans, on the other hand, had found the German arrays superior to their own sonars so early in the immediate post-war period they put their own versions to sea to test them thus initiating the BQR hydrophone array programme which was to produce many famous sonars. They also embarked on a programme named JEZEBEL to detect discrete frequencies (tonals) from a target using narrowband techniques with frequency analysers. This programme was to morph into an airborne sonobuoy system and the seabed Sound Surveillance System, SOSUS that was to prove so effective detecting Soviet submarines during the Cold War.

Figure 14: GHG BALKON ON U194 (TYPE IXC)

This sophisticated bow array was developed as early as 1943

Although the British were aware of the American research and development and, of course, had investigated the German GHG,¹⁹⁴ it was not until the middle 1950s that the ARL CORSAIR programme and the parallel but linked UDE programme, sonar 191, were started. The technique for CORSAIR differed from the Americans as it was based on work by Sir Martin Ryle into the detection of weak radio signals by correlating signals from widely separated antennae over a wide frequency band. But, like the SOSUS programme, CORSAIR was to investigate the capability of seabed arrays to detect submarines. However, after lengthy trials based at Unst, Shetland Islands, with the array to the north, the programme was stopped because it was thought it would be ineffectual against future noise reduced submarines. Unfortunately, this thinking was based on the Porpoise class, wrongly making the assumption that the Soviets would make parallel progress in noise reduction of their submarines.¹⁹⁵

A cross correlation signal processing technique known as DICE had been developed by the ARL scientists for a series of exercises to trial the CORSAIR arrays. These techniques were fed into what was essentially a development of the German GHG, known as 'KNOUT'. The first KNOUT trials by ARL involved multi-hydrophone arrays fitted to the casing of the Tireless and Thule.¹⁹⁶ Field says "These experiments were so successful that within a few weeks it was proposed to extend the arrays to a horizontal line of 96 elements arranged so that the signals could be processed from various length sub-arrays." ¹⁹⁷ The problem was there were no hydrophones available. There were however, 'liberated' German GHG arrays available. These were purloined and fitted in the submarine Thule in early 1956. The submarine then took part in that year's 'summer war' during which the Thule's set detected over 130 different ships of which 36 were exercise targets and she was credited with eight successful attacks following detection by the arrays. A similar submarine, not so fitted, made no detections in three weeks.¹⁹⁸

The research programme KNOUT led to the development of what became known as the Type 186 or 'Searcher', a continuation of the trial array with 12 double hydrophones either side of the submarine — 24 hydrophones each side. The signal from the hydrophones was processed into frequency bands of 300-600 Hz and 600-1200 Hz and the signal was displayed on a paper record displaying the output from four pens representing each frequency band each side.¹⁹⁹ 'Searcher' could especially take advantage of the great strides in noise reduction much of which was development of the resilient rubber mountings found in the U570/HMS Graph²⁰⁰ which resulted in the Porpoise Class having a radiated noise when snorting of just 3% the previous norm.²⁰¹ The U570's mountings had been developed by the internationally renowned acoustic scientist Edwin Meyer whose work would eventually lead to the anechoic coatings of today's submarines.²⁰² The UDE and ARL research into machinery noise and propeller cavitation, which had started in 1941, also contributed significantly to the noise reduction. This research, conducted under a panel of experts known as the R&D Panel on Noise reduction, led eventually to the pump jet propulsion system desgned at the Admiralty Experimental Works, Haslar, that first went to sea in the Churchill.²⁰³

In March 1957 the Auriga was fitted with Type 186 for trials in the North Atlantic. Conducting the trial were two eminent submarine commanding officers, Lieutenant Commanders MR Todd and A J Whetstone. Their conclusions set the basis for Type 186 operation for decades to come. The arrangement of the hydrophones produced a single, fixed unsteered beam204 that meant that the submarine had to either circle or carry out a sinusoidal course while being in the ultra-quiet state. While recognising the considerable capabilities of the Type 186, they also recognised its limitations. The most important limitation was imposed by the lack of mobility of the diesel submarine. Unless the 186-fitted detecting submarine was more or less 'in the grain' ²⁰⁵ an aircraft would be needed to prosecute a contact. Alternatively, of course, a nuclear submarine, fitted with Type 186, would have the speed to prosecute her own detection.²⁰⁶

Figure 15: THE TYPE 186 HYDROPHONE

The submarine was fitted with 12 pairs of transducers either side. One transducer

Type 186 was subsequently fitted in all classes including the SSBNs for which it was bought on the basis that it had a range of 50 to 60 miles in favourable conditions compared with Type 2001's passive range of 25 to 30 miles but fitting was only achieved late in the programme on the basis of substituting 'provided for' with 'provided with'.²⁰⁷

In the early 1970s the Type 2007 was developed by the then BAC Stevenage from the Type 186 and DICE processing. BAC was under contract to ARL and the project was known by the codeword (not an acronym) 'SOAP'. With the exception of a trial in the Sovereign when the 186 hydrophones were replaced by cardioids, the Type 2007 used the Type 186 hydrophone arrays. The Sovereign experience was disbanded because the cardioids were easily broken by men working under the casing.²⁰⁸ The sonar 2007 had, like sonar 186, 12 hydrophones sets on each side of the boat. The greater benefit of sonar 2007 was that it had steerable beams which enabled the submarine to steer a straight course rather than the circling or sinusoidal course demanded by sonar 186. The set operated at a frequency of 100Hz-6.4kHz with the recorder showing six bands endeavouring to detect propeller cavitation, cooling pumps, turbine gearing and the like. The resulting printout was a foul-smelling chart recorder²⁰⁹ for both port and starboard correlated display.²¹⁰ "The …strip of paper with noise (random signals varying in intensity from black to white for each beam) combined with a consistent 3-bar stripe representing the correlated signals from each single sound source on that side of the submarine. The three bars were present because the small number of detector channels formed a diffraction pattern during processing. (Very large amplitude sound sources could show a five-bar diffraction pattern, but that was unusual.) For very distant or faint sound sources, it was necessary to look along the paper record (which represented many hours of correlation) to see the very faint characteristic bar pattern. It was usually possible to see several sources' tracks on the output paper strip and it was seldom difficult to separate which was which unless there were many." ²¹¹ A narrow band analyser, sonar 2017, was introduced. This had LOFAR analyser with three frequency scales and vernier scale with an accuracy of 1Hz, and a DEMON analyser with two frequency band and 0.1Hz resolution.²¹² This processing and display system was to receive a critical update for submarines going down to the Falklands in 1982. The upgrade used an equi-population algorithm to normalise the 12 grey levels on the display making the appearance of a contact far more apparent. The upgraded processor was then also connected to the 2046 towed array thereby extending the broadband detection capability.²¹³

Trials were conducted in the Sealion and the Otus which took a monoscopic set (i.e. half the full sonar set) to sea in 1965-6 for trials²¹⁴ but they were not very successful but then again, they were trying to detect an old T Class submarine against the background noise in the Bay of Biscay and during continuous stormy weather. When the set was later used during a major NATO exercise in the quieter, northern waters against US, French and Danish submarines, it performed well.²¹⁵

While both the Type 186 and 2007 were good at detection a classification capability was also needed. As a consequence, seven AN/BQQ-3 DEMON/LOFAR Target Classification sets, renamed sonar 2006 were bought from the USA. Four were for the SSBN submarines, one hot spare, one backup and one training set.²¹⁶ But the sonar 2006 was too big to go in the O Class submarines, they would have to wait for Dr Tom Curtis (see later) and sonar 2026.

FIGURE 16: TRANSDUCERS FACING AFT

Type 129, the successful wartime set, had temporarily been replaced by Type 169 (and Type 168 replaced Type 138). But with the January 1948 directive from the Admiralty, "In war the primary function of our submarines will be the intersection and destruction of enemy submarines in enemy-controlled waters",²¹⁷ it was clear that in order to fulfil their roles submarines needed improved asdics. In 1953 a new combination asdic was trialled at sea in the Thermopylae. The Asdic was a combination of a derivative of the surface ship four square' Type 170, called Type 171X, and Type 718X. The former was eleven inches square with one diagonal vertical mounted on top of the much larger rotatable Type 718X which was 5 feet wide by 2 feet high and split vertically into two halves for bearing accuracy by phase comparison. The whole outfit was mounted topside in the bow of the submarine under a dome. The conclusion of the trials which took place off Portland, Ushant and Gibraltar, was that the Type 171X was incapable of meeting its requirements and that development should stop but the Type 718X should be proceeded with. Indeed, the 718X was given a low-power-active mine detection capability and reclassified as Type 187 to become known by generations of submariners as 'Attacker'. It remained in the same position, where its 16' x 6' x 4.5' large dome was to become an iconic feature of British submarines, with the intent that it would provide bearing accuracy with the other development, Type 719x nominated 'Scanner' because of its horizontal high scanning rate and fitting in the keel and the back of the fin to provide torpedo detection.

FIGURE 17: HMS/M THERMOPYLAE

The dome for the trials combination sonar is clearly seen on the casing at the bow of the submarine. A similar dome housing Type 187 will become an icon of British submarine

The fourth sonar in the quartet was sonar Type 197, known as 'Watcher'. Development of the sonar started in the late 1950s with the development of an active intercept sonar known as Type 196. But work on this sonar was stopped in 1959 as part of a general NATO Policy Independence Programme and the research was given to the French. The Dutch pulled out of the programme after a year. The French having trebled the time taken to complete the programme in the UK then freely admitted that they had used the work to produce their own version of the set²¹⁸ declaring that they would not buy any of the equipment themselves but that the UK must pay the total cost. The set, which Etablissements Rally of Nice finally produced, was bought by the UK in 1962²¹⁹ and eventually went to sea in all classes of submarine as Type 197.

FIGURE 18: >SONAR TYPE 197 'PIMPLE'
SONAR TYPE 197 ANALYSER	SONAR TYPE 2019 DOME
	The dome is in the Submarine Museum. A plaque behind it says: Listens for active sonar transmissions Using Doppler can tell if the target is approaching or retiring Can indicate if the opposition is in contact with the submarine Used to aid classification of targets

Initially there were two sets of hydrophones distributed around the fin: a set of three hydrophones supplying the frequency display and four hydrophones feeding the bearing display. The hydrophones, which were made of Rochelle salts and frequently had to be dried out in the oven,²²⁰ but they were eventually replaced by the British Type 719 transducers and later collocated in a 'pimple' on the fore casing. There were three display units, the Interceptor-Analyser AUUD-1-B with a range of 2.5-40 kHz, the Interceptor-Goniometer DUUG-1-C that would show the bearing were transmission between 4-50 kHz and the remote display in the control room to show either the AUUD or DUUG.²²¹

Many trials and exercises were conducted to evaluate the capability of sonar 197 that included the submarines , Narwhal, Otter, Onslaught and Osiris. From the latter two submarines in 1965 and 1967 respectively both important performance and operational conclusions were drawn. The set operated best between 7-23 kHz as long as it was operated correctly with the initial detection normally be made on the AUUD but the set had to be calibrated first (the suggestion was against a sonar 177); warning against an active torpedo (in this case a Mark 24) was minimal and exacerbated by the length of time it took an operator to alert the command (30 seconds and the torpedo only started active transmissions at 1000 yards) and the British hydrophones reduced performance in the torpedo frequency range compared to the Rochelle salt type. An interesting side discovery was that sonar 719 could intercept a sonar 177 out to 35,000 yards with ±-5° accuracy, or five times the range at which the transmitting ship's hydrophone effect could be heard.²²² Otherwise, the sonar 197 was considered a most capable set and the amount of information it could provide was probably more than could be absorbed by the command team but that it was woefully inaccurate for bearing.²²³ It was therefore both advisable to have the more knowledgeable operator on the DUUG, than the AUUD, so that the most important relevant, information could be filtered before going to the command. That information could be any or all of bearing, frequency (for classification), range by ping stealing, range by transmission interval, danger level and mode of operation – a clue to the level of threat. The quality of operation in the trial submarines was identified as being disappointingly low.²²⁴

Type 197 began to be replaced in the early 1970s by a further product of the 'collaborative' programme. This was the sonar 2019 with its distinctive Hull Outfit 51R. The sonar, which was again made by the French, was also known by the appropriate name of PARIS which variously stands for Passive-Active Range Intercept Sonar, or the five frequency bands, P, A, R, I and S. The set provides bearing, pulse length, width and repetition rate to allow identification of specific sonars and their platform. The French signal processing was quickly replaced by UK designs based upon AUWE special-fit intercept systems. In more recent, 2076-fitted submarines the processing is in the 2076 cabinet and the data appears on the multi-function consoles but uses an updated processor,

There were also many smaller sonar developments

Underwater Telephone makes its appearance.

The genesis of the Underwater Telephone (UWT) is identified in correspondence between the Rear Admiral Dunbar-Nasmith, Rear Admiral (S) and the Admiralty in 1929. The Rear Admiral(S) had submitted an idea to the Admiralty that two submarines should be provided with apparatus to ascertain the feasibility of using the asdic beam to transmit speech. It was known to be possible and the benefits were identified as COs being able to discuss the tactical situation when at periscope depth or one CO to explain the situation to another who was deep. It was recognised, however, that it would be neither reliable nor safe and although it does not say why, it is reasonable to assume it is because of the danger of interception.

In 1930 a Staff Requirement was raised for a system to replace the existing SST equipment. It was required to work to depths of 500 feet for submarines to communicate with each other and capable of allowing submarine-ship communications and for a submarine to be able to communicate when on the surface. It was to have a variable beam 10-60° with an all-round listening capability. Although it must have been achievable with the technologies of the time, the requirement does not seem to have been progressed. With the search to replace the wartime Type 129 it was intended to fit an American designed Type 173X UWT²²⁵ with, probably, the 169/168 but is unclear whether this actually happened or not. What is certain is that the sonar Type 185 UWT made an appearance out of UDE in the late 1940s.²²⁶ Operating at the NATO standard frequency for communications at 8.087 kHz the set, with three fixed transducers in the casing, port or starboard and upward looking and using the trainable transducer array in the fin became a standard fit.

In probably the late 1940s/early 1950s a contract had been placed with industry for an emergency UWT but industry had failed to deliver. In 1951 UDE was given the job of developing the set. It was to have a minimum range of 500 yards. In developing the sonar aircraft technology was used to protect the electronics from the high humidity in submarines, and Post-Office and Army technology for the battery and earphones which were shaped to the frequency response allowing minimisation of power and bandwidth. The Type 183, having been totally developed in-house at UDE, went to sea in 1953 and was not replaced until sonar 2073 many years later.²²⁷

Sonar 2073 is fitted at each escape platform, forward and aft and each siting has a 10 kHz 'Pinger' – a location beacon sitting proud of the casing so that rescue vessels can mate with the escape hatches. The set's transducers are flush with the casing so as not to interfere with the rescue vessel. Like the Type 183 it operates from mains supplies with batteries and spares for its emergency use.²²⁸

Noise monitoring with sonar Type 189.

The war years had made submariners very conscious of own ship noise and the range at Loch Goil had been specially developed to monitor submarine signatures. The T Class were built with on-board noise monitoring hydrophones²²⁹ then in the mid-nineteen fifties submarines were fitted with sonar Type 189. The sonar had two purposes, two fixed hydrophones were at the after end of the submarine to monitor propeller cavitation complemented by a portable set for noise monitoring.

Bathythermographs.

Hackmann states emphatically that one of the two most valuable contributions towards the underwater battle from the USA during WW2 was the bathythermograph.²³⁰

The father of the bathythermograph was the South African born AF (Fred) Spilhaus. He is credited with designing the first bathythermograph at the Woods Hole Oceanographic Institute in the mid-1930s. It was a tube shaped projectile that both sank and was recovered quickly. It recorded temperature changes on glass.²³¹ The Germans used this technique in their research programmes which they conducted mostly in the Baltic although they abandoned Spilhaus early on in favour of some crude techniques developed to allow U-boat captains to approximate the bending of asdic beams.²³²

A sound velocity meter was designed in 1932 at HMS Osprey²³³ and when developed and used experimentally the velocity of sound underwater was able to be determined accurately and thereby the effects of temperature gradients, refraction, reflection, scattering, spreading and absorption, indeed all the factors affecting asdic performance began to be understood.²³⁴ An intensive trials programme was undertaken during the 1930s and, by 1937, 285 trials have been carried out in various parts of the world.²³⁵ but it was the Americans who developed the Bathythermograph as a useful instrument for submarines and American submariners were shown how to use layers to best effect.²³⁶ The British bought the American AN/BSH-2 bathythermograph and it was at sea in British submarines in WW2. How much the COs were educated in its use, however, is unclear but they certainly knew the effects of good and bad asdic conditions especially in the Mediterranean and were sufficiently familiar with its capability to use it to assist trimming and quick depth changes.²³⁷

But it was not until 1964 that the AN/BSH-2 was replaced by the transistorised two channel AN/BQH-1B that showed both the velocity of sound and water and the depth. This became sonar 2004 and was fitted in all submarines²³⁸ to be later complemented by the expendable — fired from the SSE – sonar 2039. Today, the Astute Class have a far more sophisticated Environmental Sonar Suite, sonar 2115. This has two sensors, one by the foreplanes and one in the fin that measure both temperature and salinity.²³⁹

A new class of submarine and updates to operational SSKs

Upholder: A new generation of SSK

The next generation of SSK was supposed to be a small boat, the original Naval Staff Target identified 1850 tons,²⁴⁰ that could be used in many of the classic roles of an SSK, for training and for command experience. The design, however, moved away from the original conception to something much bigger and sophisticated.²⁴¹

The design of the main bow array sonar for the 2400 or Upholder Class, started in the late 1970s. Like the design of the submarine it was a contentious issue. Sam Mason, who was now head of sonar at AUWE, met with the decision-makers Admiral John Fieldhouse, Controller of the Navy and Rear Admiral Bryson, Director General Weapons. Mason wanted to convince the meeting that UDE could produce a better sonar for the submarine than anybody else in the field. There was a necessary caveat, however: it could be in time for the end of the initial trials programme but not, unfortunately, in time for the submarine's launch. An in-camera lunch followed the meeting to which Mason was not invited but on conclusion Admiral Fieldhouse had to tell Mason that a decision had been made to buy the French Thomson Sintra sonar Argonaute, a passive search and intercept sonar. This became sonar 2040. Matters, however, did not rest there. Finding that the array materials were unacceptable Mason missed out on the chance to make the array at AUWE when it was leaked to the French what materials AUWE were using. However, he did win the battle for an increase in the height of the array which improved the directivity and passive performance. Then there was the question of the beamformer having insufficient digital storage but Masons concerns were dismissed out of hand by the French. He was not allowed to warn the MoD Directorate for Underwater Weapons Production (DUWP) about the situation because it would jeopardise the contractor's position!²⁴²

Another foreign sonar to be fitted in the Upholders was sonar 2041 otherwise known as the American Micropuffs, a passive ranging sonar that used the baseline between the three transducers to triangulate. Passive Underwater Fire Control Feasibility System (PUFFS) had been developed in the 1950s and 60s as the American AN/BQ G-4 and had gone to sea in the US SSKs. Micropuffs, a derivative of PUFFS, had been used by the Australians in their Oberon Class submarines since the 1970s but the Upholders were the only British submarines to receive the system.

Other sonars in the Upholders were sonar 2007, the French Thomson Sintra sonar 2019 PARIS, a bathythermograph sonar 2004 and the UWT sonar 2008 accompanied by sonar 2009 underwater IFF and sonar 2010 underwater teletype receiver/transmitter.

Despite the issues with the bow sonar British submariners claimed the Upholder a fine, capable submarine.²⁴³

O-boat Upgrade: 2051/Triton

With the lost opportunity to develop the sonars for the Upholder Class and the growing requirement to replace the obsolescent sonar outfit of the Oberon Class the research organisations resolved to establish their rightful place at the forefront of sonar development. Working on the principle of 'seeing is believing' they managed to procure the services of a trial submarine, the Opossum. However, the Opossum was an operational submarine so they were only given the period of her intermediate docking, which was three months, to install a new sonar fit

Reviewing the situation, it was identified that an O-boat had the strength and space to take a large array in the same place as the sonar 187. It would, however, need a new dome. Fortunately, a suitable circular passive sonar array that would give almost 360° coverage was available as a result of the research programmes at AUWE and the Plessey dome fitted to the Australian submarines to house their Krupp CSU3-41 attack sonars would cover the array.

FIGURE 19: THE TRITON BOW ARRAY

Three principal contractors, Plessey, Ferranti and Marconi were invited to participate in what was to become known as the Triton sonar suite, (a name plucked from random), on a risk basis for which they formed a joint-venture company. Plessey was to be responsible for the bow sonar beamformer and processing for which they used Curtis technology (see later); Ferranti would provide the sonar 2046 towed array which would be processed through the sonar 2007; and Marconi would provide the intercept sonar. This latter sonar, eponymously named Donald after its inventor Dr Donald Nairn had an array of unevenly spaced ball hydrophones under a blister dome. A low fequency used the longer base and vice versa for high signal strength while digital processing was able to give accurate frequency and period-processing, which looked for repeating periods (15 to 20 cycles were necessary), reduced the false alarm rates. The set had a slave display in the control room showing direction of the intercept for evasion purposes.

The development was not to be without its issues. As the completion date approached a problem was identified with the main array beam forming card and no resolution, and therefore no rectification date, could be identified. Nairn took a risk and developed a rudimentary beamformer that could be installed to prove the system in the hope that the main problem will be rectified in time. The risk paid off, but in the interim a new problem of a 'rumble' from the dome arose. Fortunately, the interference from the rumble was below the sonar frequencies and was removed by simple high-past filters. This rectification was accomplished within the timeframe of waiting for the main array beamformer problem's resolution. However, all this led to the bow sonar processing not being properly set to work and this had to be rectified before the operational trials by taking some drastic action: the processor was un-shipped, put in a car and taken to Weymouth, rectified and driven back to the boat in Faslane all within a week.

To fit the new sonar outfit in the submarine Sound Room a wooden mock-up was made at Weymouth. It was then found that the then standard cabinets would not fit. They were redesigned and Trton became a the first fully Royal Navy integrated sonar system having a common suite of operator consoles with touchscreens. The consoles subsequently became the standard multifunction displays for future submarine sonar outfits like, with further modifications for things like touchscreens and later sonars 2054 and 2076

The Canadians bought Triton for their three Oberon Class submarines in 1989 and nine outfits were ordered for the British O-boats although not all were fitted as submarines were taken out of service as part of the end of the Cold War dividend despite the sonar suite proving to be operationally outstanding. It was also destined for the second batch of the Upholder Class and the contract for this for it was won by Ferranti. When the Upholder building programme was curtailed Ferranti received compensation for the terminated sonar contract and purportedly used the money to bid for the sonar 2076.²⁴⁴ The lessons from sonar 2051 were used to develop sonar 2072 the last in a series of updates to sonar 2020.²⁴⁵

FIGURE 20: THE TRITON FOUR MULTIFUNCTION CONSOLE

These consoles became standard for all future sonar sets

The Nuclear Revolution

Sonar 2001

With the advent of HMS ²⁴⁶ and the nuclear revolution, followed shortly afterwards by the commitment to a submarine launched nuclear deterrent heralding the SSBN, it was clear from the preliminary studies that a large array would be needed to meet the needs of both the SSNs and the SSBNs. The Navy was, of course, thinking about how best to employ the and the follow-on SSNs and how to deploy the SSBNs. Those considerations were tailored by an excessive optimism about the reduction of submarine radiated noise and the possible use of active sonar as part of convoy and force protection. The conclusions drawn, therefore, were in favour of a sonar that was capable of both active and passive operation but with the emphasis on active.²⁴⁷

This led to the general characteristics for what was still called Asdic Type 2001, but shortly afterwards more simply sonar 2001, being agreed in 1957 when work started in earnest on the project. It was given the designator '2001'in place of the more sequential '201' to reflect its complexity.²⁴⁸ In summary, under good asdic conditions, the set was expected to detect an 8-knot snorting A-class submarine in deep sea state 2 at 30 miles. At own ship's speed of 10 knots the range was 17 miles and at 20 knots, 6 miles.²⁴⁹

The active performance took account of 'convergence zones', in which case detection was expected to be about 25-30 nautical miles on a broad aspect submarine, and 'bottom-bounce' although no figures were given for that scenario mostly because little was known about the phenomenon. The mode of active transmission is not identified but the ranges anticipated were as follows:²⁵⁰

TABLE 2: PROPOSED AGREED CHARACTERISTICS FOR ASDIC TYPE 2001, TNAADM 259/254
SPEED	Range Against Broad Aspect Target	Arrange Against Fine Aspect Target
5 knots and below	25 miles	15 to 22 miles
10 knots	18 miles	12 miles
20 knots	8 miles	5 miles

What was to evolve was a ground-breaking, massively advanced sonar for its day, much admired by the Americans for the standard of its engineering and coveted by the French who, refusing to buy a foreign sonar, asked for the production drawings. They were refused.²¹⁰ Moreover, sonar 2001 was never formally accepted into service and this allowed a programme of continuous development without the sonar becoming part of the support regime.²⁵² As a consequence, submarines were often going to sea with a new development.

As project leader of the 18-strong team at UDE, Sam Mason put the sonar in context: "177 [the principal surface ship sonar] used about 400 valves, had four receiver beams. 2001 had 96 correlograms to cover 240 degrees as opposed to 40 degrees for 177. 2001 used about 16,000 transistors". (sic). The transistor had been invented barely 10 years before and 2001 was to use them for both transmitting and receiving. The optimism for this ambition received some scepticism²⁵³ and Naval project staff had to go back to 'night school' to bring them up to date on electronics, so advanced was the technology at the time.²⁵⁴

Before joining the 2001 project, Mason had been working on the Type 177. As a result of this work, and especially because of his work on Doppler processing, he had been invited to make presentations in the USA. During the course of this visit he had the opportunity to see what the Americans were doing with regard to the development of their 2001 equivalent. This shaped his thinking. In particular he was convinced that at least part of the American approach was wrong. He explains his ideas for 2001 thus:

FIGURE 21: THE 2001, CONFORMAL BOW ARRAY

"Since passive alone was essential for the SSBNs, I pressed for the array transducers to be spaced for 6.5 kHz, not 3.2 kHz. This was accepted, partly I expect because it gave a very good short-range performance against a very quiet targets, and partly because it made the transducer easier to design. This also meant that we could have 2 passive bands, 800 Hz-1.5 kHz [1.5kHz-2.5kHz], and 5.5-6.5 kHz. This gave, at LF, wide beams for long-range detection where bearing accuracy was not critical and could detect noisy targets but not very quiet ones. The narrow 2 degree correlograms from the upper band [HF] gave accurate tracking and detection of quiet targets at shorter range; higher absorption which increased propagation loss at longer ranges but was unimportant at short range say less than 10kyds. The result of these decisions was that we needed a very wide band multi beam beamformer (24 beams active made up of 48 half beam pairs spaced at 5 degree intervals)"²⁵⁵ How much of this design thinking was influenced, either to include or exclude, by the digital multi-beam sonar (DIMUS) beam-forming techniques that came from the US as part of the technology-transfer is unclear.²⁵⁶

There was some contention as to where the array was to be sited with discord between the sonar 2001 project and the Torpedo Launching Team. The story as to how this dilemma is resolved is almost apocryphal and although certainly true the versions vary a little. What is known is that a meeting was held either at UDE or the MoD at which both parties were present under the chairmanship of, probably, Admiral Louis Mountbatten who was at the time First Sea Lord. The Torpedo Launching Team wanted the sonar mounted on top of the submarine rather like the sonar 187 dome whereas the 2001 project wanted a conformal array in the bow of the submarine to reduce flow noise. The torpedo people argued that "You've got to give the submarine teeth" implying that the torpedo tubes had to have precedence whereupon the 2001 project retorted that "You have given it bare gums!".²⁵⁷

The 2001 project had taken with them a model of the USS Albacore and a quantity of plasticine. When asked by Mountbatten where they wanted the sonar fitted they were able to show by placing the plasticine around the bow of the submarine. Mountbatten is supposed to have said "that looks quite nice you can have it".²⁵⁸

The 2001 project had won, however, the sonar was to be positioned above the horizontal centreline of the bow and this meant that the face of the array was pointing upward at 20° which was poor for self-noise and although there was no problem with beam formation that could correct the slope, the downward vertical beam needed for bottom bounce was ruled out. This poor position was corrected later in the Swiftsure and Trafalgar Class submarines with the BC variant where the transducer array was positioned below the centre line and downward looking with the position of the torpedo tubes reconfigured. The space for the 22 '60 Way' hull glands, one for each of the 21 the castings with 56 transducers each in the bow array plus copious spares of various parts that connected the transducers via the pressure hull to the Sonar Cabinet Space was known as the 'Cabbage Patch'. In the Valiant Class this area was 80 feet aft of the array above the wardroom and in the Resolution Class it was above the Sonar Cabinet Space.

Inside the submarine were the Cabinets containing the electronics for the sonar, six of which controlled the 10 transmission modes²⁵⁹. In the Sound Room was Cabinet 27 which contained the Main 'Function Switch', the 'Sequence Timer' and four Displays and Recorders – these were the Initial Detection Display (IDD), the Sector Display, High Frequency (HF) and Low Frequency (LF) Pen Recorders. A PPI display was sited in the Control Room. Twenty-four other Cabinets were sited in the Sonar Cabinet Space (on 3 Deck in the Valiant and Churchill Class) comprising Transmit Receive Switches, Transmitter Power Amplifiers, Transmit and Receive Horizontal and Vertical Lag Line Units, PPI Receivers, Sector receivers, Buffer Amplifiers, Own Doppler Nullifiers, Stabilising Switches and Scanning Switches. Although there were nominally 27 Cabinets there was no Cabinet 25 as this – containing the HF & LF Pen Recorders - has been subsumed into Cabinet 27. The 'Sequence Timer' and the 'Function Switch' controlled the various Active transmission modes via a complex mechanism comprised of a 230-volt motor and a gear box, driving layshafts, camshafts, bevel gearwheels and microswitches. Electronics of the late 1950s and the 1960s could not reproduce the required accuracy of control.

FIGURE 22: A LATER VERSION OF SONAR 2001 DISPLAYS

The IDD utilised Photographic Display Units (PDUs). The PDUs were variants of equipment used by the RAF in reconnaissance aircraft modified considerably for Sonar 2001. In the RAF version reels of 1,000 feet of 35-mm black & white film took pictures continuously during a flight and the films were developed back at base after the plane had landed. 2001 still used the 1,000-foot reel of 35-mm film but, following a Transmission Sequence, the PDU photographed the received picture as it built up on the face of a CRT. As the next Transmission Sequence started the picture just taken was 'transported' (snatched) across to a 'processing pot' where it was developed, fixed, washed and dried such that, at the end of the 9.1 second Transmission Sequence, it could be further transported over a Projector Lens and then back-projected via a system of mirrors on to the IDD Screen i.e. the IDD Operator(s) was always looking at pictures from the transmission before last, a significant delay in the case of the 80 kyds range setting! Two PDUs were fitted as they were a complicated mix of electronics, pneumatics, photographics, liquid chemicals, high voltages and optics – very temperamental and subject to film breakages and running out of chemicals. In case of defects or maintenance and, on selecting the standby PDU, one of the mirrors was rotated through 90 degrees and, ideally, the picture from the second PDU would line up with the previous picture.

The 'Sector Display' was both an Active and a Passive Display. In its Active Mode the Sector Operator would select the approximate range and bearing of a contact of interest identified from the IDD screen. In the next 'transmission sequence' a 512 millisecond FM transmission would be sent out on the selected bearing and, in the following receive period the Sector Operator would look for an echo at the expected range and bearing. This was to provide an accurate range and bearing for Fire Control.

In the passive mode of Sector operation the UC1, or the senior UC Rating on watch, would man the Sector Display and could scan through the forward 240 degree arc to listen for and classify contacts of interest identified from the HF and LF pen recorders and could also sweep through the stern arcs listening to the signals from the stern scanner²⁶⁰

Trials for 2001 were conducted on HMS Verulum, an old wartime V Class destroyer. (The Verulum was relieved by the Matapan which was specially converted with extra accommodation, an additional funnel for the sonar power generator, and the ability to land helicopters). The Verulum was too small to take the full 2001 so only half the sonar was installed in a very large dome that increased the ship's draft by 11 feet. The dome also affected the ship's sea keeping capability by drawing down the ship's bow wave covering the dome with aerated water above 8 knots thereby greatly increasing self-noise and introducing a trials limitation.²⁶¹

FIGURE 23: SONAR 2001 FILM GATE

Trials took place in various sea areas and lasted until 1962. In the Mediterranean, on one of the few occasions the trials were held against a nuclear submarine, the set passively detected the USS Nautilus at a range of 200 miles when the submarine was at high speed.²⁶² On other trials, against submarines like the Cachalot in the North Sea, the set detected the SSK at 34,000 yards in the active mode.²⁶³ An added bonus was that the trials team could conduct bottom bounce trials because of the position of the transducers in the ship. With the upward -looking position in the , of course, this was not going to be possible.²⁶⁴

All of this development and activity attracted the attention of the Soviets. Following a tip off from a CIA agent in the Polish intelligence, Michael Golenieski (codenamed SNIPER) this led to the notorious Portland Spy Ring consisting of the ex-Master at Arms, Harry Houghton and his mistress Ethel Gee who worked at AUWE and procured the secret documents the Holy Grail being the DIMUS technology.²⁶⁵ These were handed to a Soviet spy, Gordon Lonsdale, a Canadian businessman. He in turn took them to the house of Peter and Helen Kroger who ran an antiquarian book business. Documents were sent abroad hidden in the books. It came out at the trial that the Krogers were really Morris and Lona Cohen, renowned spies from the United States.²⁶⁶

The 's sonar 2001 was, of course, a prototype, known as 2001 X1, designed and built at UDE. Shortly to follow the were the all-British SSNs, the Valiant Class and the Warspite Class and then the Resolution Class SSBNs. A competition was therefore held between the government laboratories and industry to manufacture the sets and it was won by Plessey. On the back of this win the Plessey company selected Templecombe to build a new factory on the basis that it had an east-west and north-south railway line for good communications. Unfortunately, no sooner have they moved into the facility than Dr Beeching scrapped the north-south line.²⁶⁷

All the sonar 2001 sets, however, for the Valiant Class, Churchill Class, Resolution Class and Swiftsure Class were to be built at Plessy's Ilford factory. The Valiant's 2001 X2 was slightly different in the layout of the bow array and the sonar cabinet spaces and with the Warspite's 2001 X3 there were again some further differences. Barrie Downer recalls these differences being highlighted in BR2510, the System Handbook, with different colour pages for the three boats. The Churchill and Resolution were all production models which were back-fitted into the , Valiant and Warspite as they were later refitted.²⁶⁸

Domes to cover the conformal array were also backfitted. The version 2001X went to sea initially without a dome but having had the idea tested in an SSK. The concern was that domes of the time caused bearing errors detrimental to developing the attack solution. The Americans were using steel domes which caused significant losses in transmission source level. It was not until 1970, after trials to test the transparency of a fibreglass dome, that domes were finally fitted although there were further problems to come for the new domes introduced spokes. This is where a benefit of the sonar not having been accepted into service helped. A measure known as Palliative was sent to sea. Palliative normalised the spokes and restored the performance of the sonar but it was not until the domes were coated in Rho/C polyurethane that the problem was finally resolved in 1976.²⁶⁹

Sonar 2001 was, of course, a very powerful active sonar and in the early days of the first three SSNs the COs used their sets frequently in the active mode albeit with a different panache.²⁷⁰ The then Lieutenant Commander Tony Wardale, a sea-rider for the 2001 trials in the observed the differences. Commander Peter Samborne, the first CO of the who had been American trained, would "drive his submarine at 500 feet and 28 knots enjoying a horse's neck (brandy and ginger ale) and a game of liar dice".²⁷¹ Samborne was followed by Commander John Fieldhouse, later, of course, Admiral of the Fleet and Chief of the Defence Staff. Fieldhouse's style was very different: a small glass of sherry sufficed. There was a consequential change in the character of the Wardroom noted Wardale.²⁷²

In the book to celebrate the Centenary of the Submarine Service, Anthony Howell relates both the and later the Warspite operating in an exercise against the South African Daphne class submarines. The SSNs used active sonar throughout and the small diesel Daphne boats got the better of them.²⁷³ This was in 1973 and 1975 respectively. It was not, of course, just these two experiences that persuaded SSN COs to use their 2001 sonars in the passive mode rather than a booked hot healthy one jumped over the phone plenty fibre is impetus was to move to Stoke and on the steps ctive but by then the Swiftsure Class was making its appearance and operational doctrine was very much for the passive mode. There was a serious Cold War in progress and any of the original ideas of using active for convoy or force protection had been long shelved.²⁷⁴

The Swiftsure Class brought with it the BC variant of which the most striking change was that the sonar was now in the chinstrap (below the centre line) position. There were of course many other improvements: the original germanium transistors were changed to silicon types and the server controls were changed to digital controls mixed up with analogue electronics. The ripple effect motor in the transmission system was also digitised. The Swiftsure Class also had a sonar 2018 DEMON analyser with electrical sensitive (Teledeltos) paper and sparky pens. The problem now, with sensitive analysers, was that the internal electronics of the 2001 set were so noisy they were masking target noises and so over the next five years much work was done to reduce the internal noise of the set.

The Swiftsure was commissioned in 1973 and very shortly afterwards, if not by then, design work on the next generation of bow array sonars, sonar 2020, had started but before that what was known as Phase 3 modifications were made to sonar 2001being developed jointly between AUWE and Plessey Marine, Ilford. Under this phase electromechanical elements were replaced with a digital sequencer unit enhancing the reliability and status of the system fitted in the Churchill, Valiant Class, Swiftsure Class and Resolution Class.²⁷⁵ It was during these Phase 3 modifications that the IDD display was abandoned and its output incorporated into the new displays.²⁷⁶

FIGURE 24: SONARS AND OTHER FEATURES OF THE SWIFTSURE CLASS SUBMARINE

Sonar 2001 was to be replaced in the Trafalgar Class submarines by sonar 2020. This sonar was an evolutionary development from the sonar 2001 (and the technology from sonar 2016) with a chinstrap bow conformal array, improved vertical coverage and accuracy and the Ferranti 1600 B computer to provide improved processing and track management displayed on new twin 24 inch CRT cursive displays that replace the old chemical IDD processing system and HF/LF recorder paper rolls.²⁹³ But possibly the biggest change was that, during the evolution of the bow array design for the 2020 and subsequent 2074 sonars, the majority of the transducers were now employed as passive hydrophones and only a small number retained for a residual active capability.²⁹⁴

Post 2001: The Towed Array, Processing and the Integrated Sonar Suite

The towed array

The genesis of the towed array concept lies in the Chesapeake Instrument Company's experience in designing seismic towed arrays for oil companies and in the late 1950s/early 1960s the USS Albacore and a USN SSBN trialled towing an array. An array made by the Bell Telephone laboratories in 1961 and trialled in an SSBN proved the concept and led to the first towed arrays being provided to the American SSBN 616 and 640 classes of submarine in the mid-1960s.²⁹⁵

The first British submarines to receive a towed array were the Resolution Class SSBNs in the mid-1970s. The array, known as sonar 2023, was American in origin as was the processing system associated with it. Significant levels of research into a UK towed array design was undertaken during the 1970s by ARL at Teddington and this was rapidly matured via industry to become sonar 2024 and was fitted to some Swiftsure Class boats. In some installations the towed array signals could also be used to feed the Sonar 2007 analyser system via a switch box, as an alternative to the hull arrays. Bearings of contacts observed by sonar operators of these systems were manually cut through to the command system.²⁹⁶

Introduced around 2003, Sonar 2074 was designed as the update for the Swiftsure Class and Trafalgar Class submarines. It was to be developed by GEC Marconi Marine who opened the purpose-built facility at Croxley Green near Watford to manufacture the sonar suite. However, the work moved to Templecombe when Plessey was taken over by GEC Siemens in 1988.297 Sonar 2074 was a long-range, active/passive, multi-function suite using HF, LF and FM frequencies across a range of sonars arrays: bow, flank arrays, reelable towed array, and a clip on towed array.

The orders for the Vanguard Class SSBNs started from 1986 and their sonar fit reflected the technology of the day. The main sonar suite, 2054, was, like 2074, an amalgamation of sonar arrays around the submarine including new, 'thick' flank arrays, the sonar 2046 towed array which used the improved sonar 2007 broadband correlator as its display, the bow array now sonar 2043 and the 'Donald' intercept set that had been developed for sonar 2051/Triton in the updated O-boats now called sonar 2082.²⁹⁸

FIGURE 25: SONAR 2082 – DONALD – ON THE RUDDER OF A VANGUARD CLASS SSBN AND THE SONAR 2054 FLANK ARRAY ALONG THE MISSILE COMPARTMENT

The 'pimple' dome of sonar 2082 can be seen against the sky; the flank arrays look like boxes stuck on the outside of the missile compartment.

By 2006 the Americans had developed their Acoustic Rapid COTS insertion (ARCI) programme forced on them by escalating costs, development in the commercial information and communication technology industries and the reducing sonar advantage with the Russians. The aim of the programme was the replacement of legacy sonar systems and financially manageable future development programmes. The MoD was in sympathy with the substance of ARCI although its focus of what it called "open spiral acquisition management" was more to do with cost of ownership of the legacy systems. As a consequence, in 2001 the MoD launched the Delivery of Rapid Sonar COTS Insertion programme (DEeRSCI). The Defence Science and Technology Laboratory, (Dstl) and QinetiQ led the programme with a number of industrial participants. ²⁹⁹ Development and trials showed the 2054 IR as viable and in December 2005 a tender was released. There were three bidders among which was Lockheed Martin UK which won and then used the principles of both ARCI and DeRSCI³⁰⁰ to implement the programme in a series of incremental phrases with a number of subcontractors.^{301 302}

For the supply chain and the developers, the benefits of all these programmes were self-evident. For the operators, they received better signal processing and thereby a greater opportunity of target detection, improved MMI and displays. The programme also delivered a Full Operational Trainer at HMS Raleigh.³⁰³

FIGURE 26: TOWED ARRAY ARRANGEMENTS

Sonar 2076 was developed in response to the Walker spy ring leaks in the 1980s in order to maintain a UK acoustic advantage. Like sonar 2074, Sonar 2076 was a fully integrated passive/active suite with bow, flank and towed arrays that provide a 230° forward arc for active sonar and a 360° passive capability.³⁰⁸ The intercept sonar retained the sonar 2019 hydrophone dome but had the Donald or sonar 2083 processor.³⁰⁹ The suite includes inboard processing, a recording suite and seven twin-screen operator multifunction common consoles. It was designed for the later Trafalgar Class and the early Astute Class submarines and included new developments in the towing winch technology, introducing direct drive electronic control to the winch making it much more flexible in positioning under the casing and providing superior control. Development and implementation coincided, however, with the Thomson takeover of Ferranti's sonar business to form Ferranti Thomson and, possibly more importantly, the end of the Cold War. The latter took the urgency out of sonar developments and consequently it took nearly 10 years before achieving Full Operational Capability in March 2009 in what was known as Stage IV of the system development.³¹⁰

Like sonars 2001 and 2020 before it, Sonar 2076's bow array has retained both its conformal shape and initially 1176 transducers weighing about 20 tonnes (later boats have a modified array)³¹¹ although the dome was now made of Rho-C rubber-carbon fibre material protected by a 'Toughskin' coating. The flank array has 48 conformal modules with 24 each side of the submarine of which 20 forward with a separate group of four aft. Of the 20 modules, the forward four and the after four can be used for passive ranging as can the separate group of four aft. In the earlier boats these were known as 'thick' flank arrays and have the disadvantage of compressing with depth thereby affecting the trim of the submarine to such an extent that an extra ballast pump was required. There were later replaced by 'thin' modules that eliminated the need for the additional ballast pump.

The Astute Class submarines have the ability to stream both a 'clip-on' and 'reelable' towed array. The clip-on is streamed from the starboard side aft and has to be connected in much the same way as the earlier sonar 2023 and 2024 towed arrays and retains all the ship handling limitations of those arrays. The reelable array, however, has a drum and winch underneath the casing with control from inside the submarine giving more flexibility. Both methods have cutters in case of emergency.

FIGURE 27: THE INTEGRATED SONAR 2076 SUITE OF THE ASTUTE CLASS

There are two arrays for mine detection, one for transmission and one for receiving. They use high frequency short pulse transmissions to detect close range objects like mines at ranges up to about 300m with a transmission beam width of approximately 15° both horizontally and vertically.³¹²

A concern with an integrated sonar suite is power failure which could lead to a total loss of functionality and if the submarine was deep at the time it would pose a problem returning to periscope depth or surfacing. Sonar 2085 resolves this issue by utilising signals from every other stave in the forward and after fin arrays and feeding the signal to a hand -controlled scanner and display unit in the sound room. It has its own Uninterrupted Power Supply

Data recording has progressed from the early Racal four track recorders to needing the equivalent data rate of one music CD per second today.³¹³ Within the sonar 2076 suite this is taken care of with the Common Open Recorder (COR II) with two data recorders using RAID technology each of which has four data recording packs and they can work continuously.

Thales, which had lost out on the sonar 2054 IR bid, was given the contract to migrate the sonar 2076 to an open architecture in what was known as the Stage V programme. Thales used its Open Platform for Underwater Systems framework (OPUS) to dramatically increase the processing power — from 150 Mflops to 450 Mflops — and data with from 15 Gb/sec to 400 Gb/sec but at the same time reduce the cabinets from seven to six while allowing additional hardware to be installed. Two notable benefits from this work have been the ability to run third-party software and the HCI advantages of new full-colour role-based displays that came out of Thales' private venture programme, Novus.³¹⁴

The contribution of Dr Tom Curtis

Many eminent scientists were associated with the development of Royal Navy submarine sonars during the Cold War and some of their names adorn the footnotes to this paper. But no history of submarine sonar would be complete without recording the outstanding contribution of Dr Tom Curtis.

Dr Curtis' main break-through started in 1979 after he had designed and made a narrowband processor for the SNCP programme. When the surface ship towed array, sonar 2031, was troublesome and of concern to the DUWP Project Leader, Rodney Bown. Curtis' earlier work persuaded Bown that, rather than industry, Curtis' team at AUWE could build the towed array processor and meet the deadlines. Taking a risk of bucking the trend for expensive defence industry solutions, Bown gave Curtis the job to work in parallel with Marconi the contractor. Under Curtis' leadership, his team designed and built a 32 channel 5 octave processor in about 6 months. When it came to the trials in HMS Lowestoft, the Curtis team walked onboard at 9am and left at 1230 with the system working and tested. The trial had been arranged for Marconi, but their system was not ready, so it was agreed to trial the Curtis equipment instead. This was so successful that Admiral Hill Norton, the First Sea Lord, was invited to see the results. He in turn went to the Controller of the Navy and the consequence was that the Marconi contract was cancelled in favour of the Curtis system.³¹⁵ Not only were the deadlines achieved but the MoD saved about £70 million. The set became sonar 2031Z and went to sea in the Type 22 and then later, the Type 23 frigates.

On the back of this success, Curtis was asked to build a replacement processor for the SSBNs' towed array as their programme too, was falling behind. This time a 32 channel, 2 octave processor was developed and built and then trialled in HMS Revenge. This became sonar 2062, a stop gap that went to sea in the SSBNs before sonar 2026 was finally commissioned for the SSBNs, Trafalgar and Upholder Class submarines. Going from strength to strength, the Curtis team went on to build the processing for sonar 2046, the new towed array, although the design was transitioned to Ferranti who used the new multifunction consoles with the proprietary 'CHARGE' graphic displays.³¹⁶ Sonar 2046 functionality was subsequently subsumed into the sonar 2076 suite made by Thales. These developments were contrary to the way the Americans were moving. The Americans were spending much effort on thin arrays to use at high speed. In Mason's opinion, this was "bad acoustics!" and, following a presentation to a high-level group including the Controller of the Navy and DGW, the British argument to adopt tactics for slower arrays with better acoustics was accepted.³¹⁷

A team member explains Curtis' genius by doing what the Americans and UK industry were not doing. He took another route, building modular hardware based on commercial digital electronic devices (this meant few board types and low-cost devices) and then used simple computers for control display. He also used local small sub-contractors. Together with digital memory advances his solutions were effective a very real outcome being a 60% reduction in the system weight and an 80% reduction in power consumption over earlier sets.³¹⁸ This made powerful processing available to the SSK – and with considerable cost savings. This was all made possible by his first-class knowledge of state-of-the-art electronic devices and signal processing algorithms, a real understanding of at-sea sonar design and a multi-disciplinary approach matched with a practical, 'can-do' attitude and well-honed leadership skills.³¹⁹

Conclusions

The history of submarine sonars seems to be very much in two parts: the early developments were the first part when submarine sonars, or asdic as they were then known, were second-class citizens to the development of the anti-submarine asdic. It is interesting to see how many technologies of the future underwent embryonic trials in those days. Submariners were, however, fortunate that the developments led them to having the capable Types 129 and 138 asdics at sea during WW2. Post WW 2 gave the new SSKs a revitalised, and also capable, sonar outfit of sonars 187, 186, 719 and 197. These sonars were to give sterling service for over 20 years and three or four generations of submarine officers learned their trade through their use.

But it is very clear that it was both the advent of the Cold War and very much the introduction of nuclear submarines that enabled an outstanding collection of acoustic scientists and engineers to be sufficiently funded to develop what are today world-beating, sovereign assets of sonar outfits. This all started with the development of sonar 2001 for the , early SSNs and SSBNs. The admiration of the Americans and the enviousness of the French pay homage to the excellence of that sonar not to mention the many submariners who used it to great effect operationally at sea.

After sonar 2001 came its natural successor sonar 2020 accompanied by nothing short of a transformation of submarine acoustic capability with the introduction of towed arrays of increasing capability, their processing with the outstanding Curtis technology and the new flank arrays. It was these, these days, every-day, but then possibly revolutionary, advances that made each new class of submarine a better sonar platform and allowed and enabled the Cold War submariners to gain and maintain the sonar advantage.But it was not just the development of individual sonars that formed the advancements, it was also the way that sonar performance was combined and integrated –between the individual sonars and with the command system – to form the 'integrated sonar suite' that has produced such quality capability.

The research organisations have almost disappeared and industry has taken up the cudgel for future development. The bar is set high

I am indebted to the many people who have helped put this paper together: Kevin Butcher, Jeff Crawford, Tom Curtis, David Cust, Barrie Downer, Frank Everest, Marcus Faulkner, Gerry Goward, Tom King, George Malcolmson, Sam Mason, Donald Nairn, Michael Pitkeathly, Steve Ramm, Tony Wardale, Tony Whetstone, John Wickenden, Geoff Williams

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Notes

1. https://spectrum.ieee.org/: Inventors Responses to the Sinking of RMS Titanic. Two US Navy cruisers were sent to track icebergs 1912. In 1913, US Revenue Cutters had to be used thus saving the service from disbandment. Instead it merged with the US Life-Saving service to form the US Coast Guard. SOLAS: International Conference on the Safety of Life at Sea. The first conference was held in London in 1913.
2. The Journal of the Acoustical Society of America 137, 2273 (2015), The Submarine Signal Company.
3. RNSM BR 3043, p.29.3
4. ibid A transducer, unlike a hydrophone which can only receive, can both send and receive.
5. ibid
6. The name hydrophone comes from the medical world and a small rubber bag attached to a stethoscope invented by Scott Alison in the second half of the 19th century. The name was adopted by Alisha Gray (who had invented the telephone independently from Bell) when he was working on an underwater bell and microphone system with AJ Mundy. He called the underwater microphone a hydrophone. http://www.antiquemed.com and Hackmann, Willem, Seek and Strike, Sonar, anti-submarine warfare and the Royal Navy 1914-54. London, HMSO, 1984, P.5
7. HMS Collingwood Heritage Collection (CHC) Underwater Submarine Communications
8. Hackmann, op. cit., p.21
9. TNA ADM 218/1 A B Wood Personal Recollections of the growth of a Civilian Scientific Service in the Navy They were: a Mr Gordon; Lt Cdr Ashley Froude whose father was a celebrated historian, author of Froude's "History of England" and biographer of Thomas Carlyle; Lt Hamilton-Harty, later Sir Hamilton Harty conductor of the Halle orchestra; Lt Brett, a famous violinist; and Lt Rose, a London Theatre Manager.
10. Ibid p.49
11. BR 3043, P.29.4
12. http://www.rnsubs.co.uk
13. CHC Type 106
14. Hackmann, op. cit. p.74
15. TNA ADM 186/440 CB 1664 Handbook of Hydrophones in Submarines
16. TNA ADM 186/450, CB1757 DTM Department, Handbook of Hydrophones In Submarines 1926
17. Compton-Hall, Richard, Submarines And The War At Sea 1914-18, London, Macmillan, 1991, p.61
18. For simplicity, hereafter referred to as SST
19. Compton Hall op. cit. p.60
20. TNA ADM 186/450
21. Barrow Submariners Association, http://rnsubs.co.uk/dits-bits/articles/development/asdic.html acquired April 2018
22. ibid
23. Carter, op. cit., P.53
24. TNA ADM 186/535 CB 01793 Half-Yearly Report No 26 of HMS Osprey, Portland (Experimental Section) for Half-Year Ended March 31st1937
25. http://www.godfreydykes.info/Royal_Naval_Ratings_Badges_19th_-_20th_Centuries.htm
26. TNA ADM 186/440 CB 1664 DTM Department Handbook of Hydrophones in Submarines 1924
27. TNA ADM 186/450
28. ibid
29. The name hydrophone comes from the medical world and a small rubber bag attached to a stethoscope invented by Scott Alison in the second half of the 19th century. The name was adopted by Alisha Gray (who had invented the telephone independently from Bell) when he was working on an underwater bell and microphone system with AJ Mundy. He called the underwater microphone a hydrophone. http://www.antiquemed.com and Hackmann, Willem, Seek and Strike, Sonar, anti-submarine warfare and the Royal Navy 1914-54. London, HMSO, 1984, P.5
30. HMS Collingwood Heritage Collection (CHC) Underwater Submarine Communications
31. Hackmann, op. cit., p.21
32. TNA ADM 218/1 A B Wood Personal Recollections of the growth of a Civilian Scientific Service in the Navy They were: a Mr Gordon; Lt Cdr Ashley Froude whose father was a celebrated historian, author of Froude's "History of England" and biographer of Thomas Carlyle; Lt Hamilton-Harty, later Sir Hamilton Harty conductor of the Halle orchestra; Lt Brett, a famous violinist; and Lt Rose, a London Theatre Manager.
33. Ibid p.49
34. BR 3043, P.29.4
35. http://www.rnsubs.co.uk
36. CHC Type 106
37. Hackmann, op. cit. p.74
38. TNA ADM 186/440 CB 1664 Handbook of Hydrophones in Submarines
39. TNA ADM 186/450, CB1757 DTM Department, Handbook of Hydrophones In Submarines 1926
40. Compton-Hall, Richard, Submarines And The War At Sea 1914-18, London, Macmillan, 1991, p.61
41. For simplicity, hereafter referred to as SST
42. Compton Hall op. cit. p.60
43. TNA ADM 186/450
44. Barrow Submariners Association, http://rnsubs.co.uk/dits-bits/articles/development/asdic.html acquired April 2018
45. ibid
46. Carter, op. cit., P.53
47. TNA ADM 186/535 CB 01793 Half-Yearly Report No 26 of HMS Osprey, Portland (Experimental Section) for Half-Year Ended March 31st1937
48. http://www.godfreydykes.info/Royal_Naval_Ratings_Badges_19th_-_20th_Centuries.htm
49. TNA ADM 186/440 CB 1664 DTM Department Handbook of Hydrophones in Submarines 1924
50. TNA ADM 186/450
51. ibid
52. TNA ADM 273/829 Hydrophones
53. ibid
54. Carter, Geoffrey, The Royal Navy at Portland since 1845, Liskeard, Maritime, 1987, p.48
55. Hackmann, op. cit., p.61
56. TNA ADM 1/13476 Submarine Quarterly Letter Number Eleven dated 11 April 1925. In discussing hydrophone reception in the W/T cabinet listening to the eel in the cabinet is mentioned
57. TNA ADM 273/829 Hydrophones
62. ibid p.62
63. Hackmann op. cit. passim Chapter IV, THE BIRTH OF ASDICS; Proc, Jerry Asdic and sonar systems in the RCN, http://jproc.ca/sari/asd_gen.html acquired April 2018. Proc is quoting Geoff McMaster, Express News
64. Hackmann op. cit. p.88
65. ibid 126
66. Mayers, Colin, Submarines Admirals and Navies, Los Angeles, Haynes, 1940, p. 60
67. Ibid pp. 60-61
68. TNA ADM 188/1939 Correspondence between The Clarendon Press and the Admiralty
69. Hackmann, op. cit. p,.xxv
70. The Naval Shipbuilding Sub-Committee of the Committee of Imperial Defence
71. Hackmann op. cit. p.126
72. ibid p.416
73. ibid p.166
74. TNA ADM 186/475 Handbook for Asdic set type 113A in HM Submarine H32
75. Hezlet, Vice Admiral Sir Arthur, British and Allied Submarine Operations in World War II, Huddersfield, RNSM, 2001, p.1
76. Hackmann op. cit. p.173
92. Barrow Submariners Association op. cit.
93. RNSM A 1929/4 Letter from The Captain A/S HMS Osprey to the Rear Admiral (S) dated 13 December 1929
94. Hackmann op. cit. pp. 203-204
95. ibid
96. Ackermann, Paul, Encyclopaedia of British Submarines 1901-1955, Penzance, Periscope, 1989, p.168
97. Hackmann op. cit. p.128
98. TNA ADM 186/457 CB 3002 (26) Progress in Torpedo, Mining, Anti-Submarine and in aliied subjects 1926
99. ibid p. 207
100. Ackermann op. cit. p.48
101. TNA ADM 186/457 Eight of the submarines were: X1, Oberon, H32, L56, L69, L71 and HMAS Otway and Oxley
102. Hezlet op. cit. p.13
103. Hackmann op. cit. pp. 208-209
104. Ackermann op. cit. p.48
105. TNA ADM 116/3564 China Station: Fourth Submarine Flotilla Quarterly Reports
106. TNA ADM Minutes of the 35th A/S Design Committee Meeting held at the Admiralty on 21 January 1931
107. TNA ADM 186/551 Progress in Torpedo, Mining, Minesweeping, Anti-Submarine measures, and chemical warfare defence, 1938
108. Hackmann op. cit. p.211
109. Ibid p. 428
110. Hackmann, op. cit. p.428
111. Barrow Submariners Association, Barrie Downer's notes
112. McKenzie, Vice Admiral Sir Hugh, The Sword of Damocles, Stroud, Alan Sutton, 1995, p.58
120. Parry, David, The Baltic C Class, MA Dissertation, University of Greenwich, 2014
121. Parry, David, History of Submarine Command Systems, Friends of the Submarine Museum,
122. Branfill-Cook, Roger, X1. The Royal Navy's Mystery Submarine, Barnsley, Seaforth, 2012, P.64 Erroneously Branfill-Cook shows an older version of the sounding machine. At http://collections.rmg.co.uk/collections/objects/42898.html the National Maritime Museum says: "Between 1903 and 1906, Lord Kelvin worked with the Royal Navy to develop the Kelvite Mark IV Sounding Machine specifically for use on fast moving ships. This was adopted by the Royal Navy and was still being produced with only minor modifications in the 1960s"
123. Hackmann, op. cit. P.4
124. http://www.alexander-behm-echolot.de/ acquired May 2018 and Salous, Sana, Radio Propagation Measurement and Channel Modelling, Chichester, John Wiley, 2013, P.424
125. http://www.subchaser.org/fathometer acquired May 2018
126. Hackmann op. cit., p.226
127. TNA ADM 218/59 The British Admiralty Recording Echo Sounder 1935 By Henry Hughes and Son Ltd
128. TNA ADM 218/55 The British Admiralty Super-Sonic Echo Sounder 1932-1935 by Henry Hughes and Son Ltd and How the Lusitania Was Found, Irish Immigration Database available at http://www.dippam.ac.uk/ied/records/46372 acquired June 2018
129. Loftas, Tony, JIM: homo aquatic-metallium, New Scientist 7 June 1973
130. Compton-Hall, Richard, The Underwater War 1939-1945, Poole, Blandford, 1982, p. 41
131. Hackmann, op. cit., p.410 59
132. David K Brown and George Moore, Rebuilding the Royal Navy Warship Design since 1945, Barnsley, Seaforth, 2003, p.129
133. Butcher, Kevin, Sonar-So Far, unpublished notes
134. Systems Engineering and Assessment Ltd.
135. Compton-Hall, Richard, The Underwater War 1939-1945, Poole, Blandford, 1982, p. 41
136. Hackmann, op. cit., p.410
137. David K Brown and George Moore, Rebuilding the Royal Navy Warship Design since 1945, Barnsley, Seaforth, 2003, p.129
138. Butcher, Kevin, Sonar-So Far, unpublished notes
139. Systems Engineering and Assessment Ltd.
140. TNA ADM 186/462 Submarine Manual 1928
141. Before becoming Admiral (S) Charles Little, an experienced submariner, was 'Commander 4th SM Flotilla' from November 1911 to February 1915, 'Assistant to Commodore (S)' from February 1915 to September 1916, Fearless 'in command' from September 1916 and then Fearless as 'Captain 12th SM Flotilla' from May 1917 to 1919. Downer, Barrie, Royal Navy Submarine Commanding Officers 'The Perishers' 1901 to 2018
142. RNSMA 1981/31 Proposed Future Policy
143. TNA ADM 186/499 Instructions for Submarine Operations, Section 1, The Tactical Handling of Submarine Flotillas dated 1936
144. Ibid Memorandum from the Commanding Officer HM Submarine [Lieutenant Commander RM Edwards] L27 to The Captain (S) Second Submarine Flotilla dated 26 July 1932
145. ibid Memorandum from The Captain (S) Second Submarine Flotilla to The Commander in Chief, Home Fleet dated 4 November 1932
146. RNSM A 1931/2 Rear Admiral (S) letter to the Secretary of the Admiralty dated 27 February 1935
156. TNA ADM 186/551
157. Chapman, Paul, Submarine Torbay, London, Robert Hale, 1989, pp.45-46
158. TNA ADM 186/535
159. The Engineer 2 April 1920 p. 346
160. https://www.gracesguide.co.uk/Gill_Propeller_C acquired May 2018
161. TNA ADM 186/535
162. Hackmann, op. cit. P.218
163. Chapman, op. cit. p. 31 It is not clear if the earliest T-class how the mountings or if the later submarines copied the U570. See page 24
164. TNA ADM 186/551
165. TNA ADM 186/535 Appendix III document
166. ibid p. 217-218
167. Kemp, Paul J, The T Class Submarine: The Classic British Design, Annapolis, Naval Institute Press, 1990, pp. 53-54
168. TNA ADM 186/546 HMS Osprey, Portland (experimental section) half-yearly report 27 1938
169. Hackmann, op. cit. p.219
170. TNA ADM 1/15336 HYDROGRAPHY (57): Asdic detection for minesweeping, TNA 199/1924 Technical Staff Monograph and Hackmann, op. cit., p.267
171. Later Vice Admiral Sir Hugh McKenzie KCB DSO+ DSc, Chief of the Polaris Executive
172. McKenzie, Vice Admiral Sir Hugh,. Sword of Damocles, Stroud, Alan Sutton, 1995, p. 111 60
173. ibid p.106
174. Allaway, Jim, Hero of the Upholder, Shrewsbury, AirLife, 1991, p.164 and McKenzie op. cit. a p, 115
175. Dickison, Arthur P, Crash Dive, Stroud, Sutton, 1999, p. 30
176. Hezlet, Vice Admiral Sir Arthur KBE CB DSO* DSC, Submarine Operations, Huddersfield, RNSM, 2001 p 366 and Wingfield, Mervyn, Wingfield At War, Dunbeath, Whittle's, 2012, p.109
177. Hezlet, op. cit, p.313 and Ballantyne, Iain, Hunter Killers, London, Orion, 2013, p.17. The U-864 was fitted with a 'schnorchel' (American: snorkel; British: snort) but had an engine that was misfiring and making a loud noise (she was heading back into Norway for repairs). Launders detected U-864 on Venturer's hydrophones (sonar) while she was snorting, confirmed it was a submarine contact when he saw her periscope, and then tracked her by sonar for an hour before firing a four-torpedo salvo at 2000 yards with the torpedoes set at depths between 30 and 36 feet.
178. Ackerman, op. cit. p.48 and Hackmann, op. cit. pp. 217-219 The nations were France, Holland, Russia, Turkey, Greece, Norway and Poland
179. Kemp, op. cit. pp. 53-54
180. The antisubmarine establishment had some P Class and two ex-Whalers, the Icewhale and Cachalot acting as trials vessels. The Icewhale was renamed Osprey according to research by Mr. Roger Fry at http://www.dorsetecho.co.uk/news/features/nostalgia/8335706.Why_Portland_s_naval_base_was_called_HMS_Osprey/?ref=arc acquired June 2018
181. TNA ADM 186/444 CB 0975 Progress in Torpedo, Mining, Anti-Submarine and in allied subjects 1924
182. Carter op. cit. P.50
183. ibid
184. Email correspondence with John Wickenden June 2018.
185. Kemp op. cit. p.10 and Hackmann, op. cit. p. 437
186. Hackmann, op. cit. p. 437
187. TNA ADM 1/16497 Letter from The Captain, HMS "Osprey", Dunoon, Argyll dated 5th December, 1944
188. Ibid
189. TNA ADM 1/16497 The Commodore HMS Western Isles
190. ibid
191. The first references to sonar rather than asdic start to appear in the archives around this period.
192. Buer Arthur O., Some hardly known aspects of the GHG, the U-boats group listening apparatus, Foundation for German communication and related technologies, 2005, available at http://www.cdvandt.org/GHG1996.pdf
193. Rössler, Eberhard, Die Sonaranlagen der deutshen Unterseeboote, Bernard & Graefe Verlag, Bonn, 2006, passim
194. Hackmann, op. cit, p.352
195. Project CORSAIR, http://arl.g3w1.com/Corsair/index.htm acquired June 2018 hello
196. History of the ADMIRALTY RESEARCH LABORATORY (ARL) Teddington: 1921 to 1977, http://arl.g3w1.com/ : acquired June 2018
197. Field, N H, KNOUT, Journal of Naval Science, Vol.13, No. 1 (February 1987) Again Field is in contention. While Field quotes these numbers he had probably doubled them. Asdic Type 186 had 12 sets of two hydrophones each side of the submarine: a total of 48 hydrophones not 96.
198. Field, op. cit.
199. TNA ADM 259/255 Thoughts on the Tactical Uses of Type 186 Submarine Search Hydrophone Set
200. Bud and Gummett, op. cit., p. 166
201. http://arl.g3w1.com/
202. The interesting story of how Meyer rescued his research and family from under the noses of the Russians is at http://www.guicking.de/dieter/Erwin-Meyer-Eng.pdf. The first anechoically coated submarine was U480 which was not found until 1988. She had remained undetected by asdic in the Channel but was sunk by a mine.
203. Bud and Gummett, op. cit., p.162-164
204. http://arl.g3w1.com/
205. In a position whereby the target would pass close to the submarine rather than the submarine having to chase the target.
206. TNA ADM 259/255
207. TNA ADM 225/2974 Final note Polaris sonar set-up
208. Williams, op. cit.
209. Williams, op.cit. The foul-smell came from electrically conducting Teledeltos paper the surface of which was marked by a stylus carrying a high voltage that created a spark to burn the surface. The same technique was applied in the recorders of 2017 and 2018.
210. Butcher, op. cit. 61
211. Email correspondence with Frank Everest June 2018
212. Author's Perisher notes. DEMON: Detection Envelope Modulation On Noise; LOFAR: Low Frequency Analysis and Recording. DEMON is a narrowband analysis that furnishes the propeller characteristic: number of shafts, shaft rotation frequency and blade rate of the target. LOFAR is a broadband analysis that estimates the noise and vibration of the target machinery. De Moura, De Seixas and Ramos, NN, JM and Ricardo, Passive Sonar Signal Detection and Classification Based on Independent Component Analysis,www.intehopen.com
213. Nan, op. cit.
214. http://arl.g3w1.com/
215. Everest, op. cit.
216. TNA ADM 225/2974 Development of ASDIC equipment: (Long range submarine ASDIC-type 2001)
217. TNA ADM 259/111 Trials of asdic Types 171X and 718X in HMS/M Thermopylae
218. TNA ADM 225/2974 Letter from Material Branch I to HM Treasury dated 8 August 1962 and Mason, op. cit.
219. TNA ADM 225/2974 letter from material Branch 1 to HM Treasury dated 27 August 1964
220. Email correspondence with Barrie Downer May 2018
221. TNA DEFE 67/12 Report on sonar type 197
222. TNA DEFE 67/12
223. TNA DEFE 67/26 Operation Evaluation Report Sonar Type 197
224. ibid
225. Hackmann, p.cit. p. 352
226. Hackmann, in Seek and Strike, does not give a year of introduction but Sam Mason, says that it was at sea in 1951 when he was asked to develop the Type 183.
227. Mason, op. cit.
228. Downer, op. cit.
229. Conversation with Tom King, ex-TASI and Warrant Officer who remembers them well.
230. Hackmann, op. cit., P.144
231. https://www.nytimes.com/1998/04/01/us/athelstan-spilhaus-86-dies-inventor-with-eye-on-future.html acquired May 2018
232. Hackmann, op. cit., p.152
233. ibid, p.144
234. ibid, p.145
235. ibid, p.152
236. Ibid, p.290
237. TNA ADM 199/1924
238. Downer op. cit.
239. ibid
240. Brown and Moore, op.cit. p. 117
241. Conversation with Rear Admiral Tony Whetstone May 2017. Whetstone was the driving force behind the next-generation SSK when he was Chief of Staff to FOSM in the 1970s.
242. Mason, op. cit.
243. Conversations with David Cust 2017
244. Dr Donald Nairn, interviewed by David Parry 5 July 2018
245. ibid
246. TNA ADM 1/26779 A number of names were considered for Britain's first nuclear submarine including the eponymous if sardonic 'Upandatom
247. Mason, Sam, ASDIC and SONAR, A personal story from the Cold War, unpublished notes
248. Bud and Gummett, op.cit. p.172
249. Ibid p. 173
250. TNA ADM 259/254 Proposed agreed characteristics for Asdic Type 2001
251. Mason, op. cit.
252. Nairn, op. cit.
253. Geoff Williams, interviewed by David Parry April 2018
254. Wardale, op. cit.
255. Mason, op. cit.
256. Preston, Anthony, The Influence of the Cold War bond Submarine Design, in a Edmonds, Martin (ed)100 Years Of 'The Trade', a Lancaster, CDISS,2001
257. Mason, op. cit. and Bud and Gummett, op. cit., p. 173
258. Mason, op. cit. 62
259. Downer, Barrie, unpublished notes
260. Downer, op. cit.
261. Mason, op. cit.
262. ibid
263. Wardale, a op. cit.
264. Mason, op. cit.
265. Preston, op.cit.
266. http://www.dorsetecho.co.uk/news/15687081._Far_damaging_than_Profumo Secret_documents_on_Portland_Spy_Ring_released/
267. Conversation with Captain Steve Ramm, Thales Templecombe, April 2018.
268. Downer, op. cit.
269. Mason, op. cit. Mason relates the story that the CO of the Swiftsure Class submarine used for trials was uncooperative and would not allow the trials team to take measurements but the spokes had gone! The concept had to be proved on another submarine later.
270. Downer, op. cit. Barrie Downer was the Sonar maintainer in the Valiant and he recalls Commanders Peter Herbert, Dick Husk and Robin King all using the active mode extensively.
271. One hopes not literally as this would have been outside the operating envelope! Although such a thing had not yet been produced).
272. Wardale, op. cit.
273. Edmonds, Martin (Ed), The South African Navy's Submarine Service in a, Lancaster, CDISS, 2001
274. The results of a major exercise in 1957 called 'Rum Tub' which involved the USS Nautilus were largely responsible for dispelling the notions of convoy protection.
275. Butcher, op. cit.
276. Email correspondence with Warrant Officer Jeff Crawford June 2018
293. Butcher, op. cit.
294. Nairn, op. cit.
295. TNA ADM 332/1 Passive sonar classification for submarines (Sonar type 2012) Naval Staff Requirement (NSR) 7711
296. Hennessy, Peter and Jinks, James, The Silent Deep, London, Penguin, 2015, p. 375 amplified by Williams, op. cit.
297. Butcher, op. cit.
298. Downer and Butcher, op. cit. and https://www.naval-technology.com/projects/vanguard-submarine/ acquired July 2018 63
299. The participants were: ALS (towed array narrowband tracker); Array Systems Computing (towed array transient detector); Hamongram (bow array); SEA (geo-acoustic inversion process); and Thales (intelligent detection and tracking for bow and towed arrays)
300. Wickenden, op. cit.
301. The subcontractors were: Atlas Elektronik UK (formerly QinetiQ sonar processing); Drumgrange (intercept processing); Kaon (recording); Aish (displays); and Advantys (legacy interfaces)
302. Scott, Richard, Open season: submarine sonars build on commercial imperatives, Jane's International Defence Review March 2010
303. ibid
308. Downer, op. cit.
309. Nairn, op. cit.
310. Butcher, op. cit.
311. Haynes, Astute Class Nuclear Submarine: Owner's Workshop Manual, Yeovil, Haynes. 2018, p.135
312. Downer, op. cit.
313. Williams, op.cit.
314. Scott, op. cit.
315. Mason, op. cit.
316. Butcher, op. cit.
317. Mason, op. cit.
318. Britain's sonar breakthrough, Defence Attaché No. 5/1983
319. Wickenden, op. cit.

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