ADMIRALTY RESEARCH LABORATORY

1921 - 1993

‘Perhaps the most important thing we had achieved had been to help in preventing another world war' from the journal of Alec Mitchell, final Director of the Admiralty Research Laboratory, and Hydrodynamist that led the development of Pump-jet Propulsion.

Original entrance to ARL in Queens Road - primarily used by visitors, staff used a rearentrance accessible from inside the NPL site.

The Upper Lodge site was acquired by ARL in 1945 and as well as being the birthplace of portable underwater viewing systems using CCTV, contained specially constructed hydrodynamic facilities that played a vital role in the Royal Navy's operational effectiveness.

As the centre for Royal Naval research, ARL's remit was first to determine and then master the underlying science of virtually all aspects of Royal Navy operations. Accordingly, the greater proportion of modern naval warfare technology stems from the research conducted by members of the Royal Naval Scientific Service at Teddington.

Throughout the history of ARL, a key aspect addressed was the detection of submerged submarines by use of underwater sound. The first technique selected for study was Echo Detection, which involves transmitting a high power sound pulse and then listening for the echo reflecting off the target. A by-product of this research was the design and development of Depth Echo Sounders for safe navigation and survey. By 1927 ARL Acoustic Group's work on Echo Detection ASDIC (as Active Sonar was then known) was considered sufficiently mature that it was transferred to HMS Osprey at Portland, Dorset, for the development of service equipment. This opened the way for study of the more fundamental issues, which transpired to be in favour of the submarine instead of against it.

One area of research that would prove to be highly beneficial was the study of the noise radiated by vessels. Whilst the Acoustics Group undertook the detailed measurement and analysis of self (radiated) noise, the Fluid Dynamics Group concentrated on the dynamics of the motion and behaviour of bodies in water with respect to the shape, control and propulsion of warships, submarines and torpedoes. The primary aim of this dual-path research was greater efficiency coupled with quieter operation.

Such was the expansion of the work areas that by the mid-1930s there was a need for extra accommodation. The solution was to acquire further land to the east, on which was built a large office and laboratory complex in 1939. This was followed by a yet further eastward extension of the site, where a much smaller “Orlit Hut” style, single storey building was constructed.

Southern aspect of the 1939 building – commonly known as 'Fire Control' as itprovided accommodation for the embryo Admiralty Gunnery Establishment.

During WWII, ARL made great advances in vessel noise reduction, having established its first apposite Noise Range at Loch Goil, Argyll, Scotland in 1942. With the aid of this facility a dramatic reduction in the range (from 10,000 to 200 yards) at which X-Craft midget submarines could be detected was attained. The reduction in self-noise was accomplished by mounting their main machinery on a raft attached to the hull by resilient mountings designed by ARL.

Post-WWII ARL research into machinery noise sources, propeller cavitation and long-range passive (listening) sonar came together in the design and construction of a new class of conventional (Diesel-Electric powered) submarine: the PORPOISE class of the late 1950s. Their propellers were specifically designed for reduced noise by delaying the onset of cavitation. Propeller cavitation, arising from transmitting too much power or high rotational speeds, is a particularly loud source of noise that is easily detected. Both main and ancillary machinery noise reduction, together with quiet propellers, resulted in their radiated noise when snorting being a staggering 3% of what was previously the norm. Further, they were virtually undetectable when submerged and running on electric-drive. They and the similar, slightly later OBERON class were the quietest of all NATO submarines and substantially quieter than Soviet submarines. Their quietness in operation made them ideal platforms for (sonar) equipment that achieved detection by listening for the noise radiated by other ships and submarines. One such equipment was the ARL-designed long-range passive sonar, Sonar 2007. Prototype versions of this sonar (codenamed SOAP Stage II) were extremely successfully trialled in HM Submarines SEALION and OTUS in 1965.

Sonar 2007 was based on innovative digital processing of the underwater sound received by hydrophones (underwater microphones) fitted along the sides of the submarine. The digital processing concept was proven under an extensive ARL investigation into long-range (>100 miles) submarine detection systems, based on-shore, which commenced in 1952. The culmination of this investigation (codenamed CORSAIR) was large hydrophone arrays sited on the seabed connected to processing and display installed in a purpose-built Admiralty Experimental Station on Unst, Shetland Isles, over the period 1955-7.

PORPOISE Class was the first UK submarine class to embody key ARL advances.

It was very much a case of back to the drawing board as nuclear-powered submarines, capable of much higher transit and sprint (underwater) speeds, came into service. The main machinery of the first few generations radiated high levels of self-noise that demanded some radical thinking and new technology to reduce power generation and propulsion noise, to evade long-range detection by passive means.

The high levels of self-noise, besides making them easily detectable, also had a detrimental effect on the performance of the sonars fitted to the submarines. Passive sonar (2007) was adversely affected by the ever-present noise and active sonar (2001) similarly suffered degradation by the flow-induced noise arising from the higher operating speeds. Following the demonstration of the intrinsic worth (in terms of operational advantage) of long-range passive sonar on quietened conventional submarines, ARL commenced development (in 1968) of passive sonar towed array technology to provide a comparable capability for UK nuclear-powered submarines. The research created the foundations for modern sonar employing digital processing techniques, which ARL developed using specially-designed hybrid analogue and digital equipment. By 1972, this area of research was significantly expanded and evolved into the design and development of software algorithms to run on the fastest general-purpose minicomputers, then available. A by-product of this research was very high-resolution (acoustic) analysis equipment used by ARL's Acoustic Intelligence Group and the joint Royal Navy and RAF acoustic analysis centre, based at Upper Lodge. These groups were key Naval Intelligence units during the Cold War.

The other significant break-through came as a result of ARL fore-fronting the incredibly successful (radiated) noise reduction of nuclear submarines and torpedoes with the use of pump-jet propulsion. Pump-jet propulsion had important operational advantages over conventional multi-bladed propellers: they generated a fraction of the noise for the same thrust and were considerably more powerful. This was an American concept that scientists at ARL, together with engineers at the Admiralty Experimental Works, Haslar, Hants, made work and was subsequently sold back! Pump-jet propulsion was a major output of the hydrodynamics work undertaken at Upper Lodge and was first trialled on HM Submarine CONQUEROR in 1970. The hunter-killer SWIFTSURE Class of submarine (in-service 1973) was the first to be designed with pump-jet propulsion and this drove the adoption of a less-tapered aft section (offering increased internal space), which is now a common feature of submarines; thus UK nuclear submarines were decades ahead of their contemporaries.

The painstaking process of the reduction of noise from the main and the myriad of auxiliary machinery of a nuclear submarine also bore fruit as the sources of noise were identified by ARL and supressed by component redesign and with the use of rafts and flexible couplings; further reduction was achieved by sound absorbent and anechoic coverings, which ultimately led to their use on the outer hull of submarines.

The above account of the work of the Noise Reduction and Hydrodynamics Groups together with a portion of the work of the Submarine Detection Group, virtually excludes the pioneering research by the Chemistry, Optics, Mine Countermeasures, Special Problems, Infra-Red, Solid-State Physics, (Gunnery) Fire Control, Radiological Defence, Military Oceanography, Mathematics, Human Factors, Assessment, Instrumentation and Engineering Design Groups of ARL. For a more detailed account of ARL's history visit: www.arl-teddington.org.uk

ARL Groups that became establishmentsARL's Fire Control Group developed a concept of stabilised platforms successfully used for torpedo depth and direction control, searchlights, gun directors and guns. Such was the expansion of work and success in these areas that the Group evolved into the Admiralty Gunnery Establishment (AGE) in 1943, initially co-located with ARL at Queens Road. It moved to Portland, Dorset in 1953.

A somewhat unlikely contribution, and an indication of the breadth of ARL's research, is the Wave Group (formed 1944) work to predict the sea conditions for the Normandy Landings. Similar to the formation of AGE, ARL's Wave Group was renamed the National Institute of Oceanography in 1949 and moved to its own establishment near Wormley, Surrey in 1955.

What happened to ARLIn 1977 the majority of the underwater acoustics work was transferred to Portland, Dorset. This move came at the time of a renaming of the establishment to “Admiralty Marine Technology Establishment [ARL]”. The main site in Queens Road was closed down in 1988 and by then what was formerly ARL was simply: “Admiralty Research Establishment – Teddington”. With the formation (in 1991) of the tri-services Defence Research Agency (DRA), the remaining former ARL site at Upper Lodge became “DRA Teddington”, only to be closed on Christmas Eve 1993 bringing to a complete end 72 years of ground-breaking scientific research that was of immense benefit to the Royal Navy.

Author's FootnoteIn 2005, with knowledge acquired as a member of ARL's Submarine Detection Group, I commenced documenting the achievements of ARL staff, primarily so that they may have the recognition they so rightly deserve. Consequently I was delighted to collaborate with Bill Swan in the establishment of an earnest monument. Such was the highly classified nature of the work outlined above that practicallynothing was generally known until the latter-day release of Admiralty documents under the Freedom of Information Act.Currently, some 5000 documents are available from The National Archives at Kew, relating to ARL; principle references:-ADM212 “Correspondence and Letters”, and ADM204 “Reports and Notes”.

Nigel R.D. Godsell November 2015Royal Naval Scientific Service: Scientific Officer, 1963-73

ARL advances (principally) in propulsion, long-range surveillance sonar, and stealthembodied in the SWIFTSURE class, and fed forward to the TRAFALGAR Class,was the first materialisation of today's submarine.

Further information available at www.arl-teddington.org.ukOriginal line drawings by W. (Bill) Swan Assistant Park Manager

The Admiralty Research Laboratory (ARL) was established in 1921 in

response to the Board of the Admiralty aspirations to expand upon the

technological advances in naval warfare made during World War I.

Occupying the eastern end of Queens Road, Teddington, it was well

placed to take advantage of the standardisation and testing facilities

developed, next-door, at the National Physical Laboratory (NPL).