Original main entrance to ARL in Queens Road viewed from the north-west.
According to A.B. Wood it was primarily used by visitors, staff used a rear
entrance accessible from within the National Physical Laboratory (NPL) site.

The initial organisation of (principal) research staff into groups, followed that at AES Shandon.

(A) Electrical Instruments and Mining. Dr C.V. Drysdale, J.H. Powell, J.A. Craig and E. Stephenson.
(B) Electrode Search Gear. Dr F.B. Young and W. Jevons.
(C) Acoustics. B.S. Smith, G.F. Partridge and G. Burnside.
(D) Asdics. R.W. Boyle, W.F. Rawlingson and J. Anderson.
(E) Explosions and Sound Ranging. A.B. Wood, J.M. Wood and F.W. Hill.
(F) Loops. Lt. F.K. Kemp RN, T.A. Daniell and H. Forman. Concluded in 1923 - L. Champney then free to work with Dr Young.
(G) Laboratories. L.O. Cook.
(H) Silent Propulsion. J.H.W. Gill, D.V. Hotchkiss and M.W. Burgess.
(J) Unattached. D.A. Keys.
(K) Underwater Spark Signalling. Dr W.M. Thornton, F.O. Hunt and A.Stubbs.

Plus new groups:-
Optics. Instructor Commander T.Y Baker RN.
Chemical, Infra Red etc. Dr R.T. Beatty.
Mathematical and Electrical. S. Butterworth.

Virtually from day one, ARL forged strong and lasting links with the Admiralty Experimental Works (AEW) at Haslar, Hants, and the Admiralty Engineering Laboratory (AEL) at West Drayton, Middx. Rapid progress was made as ARL developed the capability of constructing bespoke test and measurement equipment for themselves. Generally, the specially-made equipment supported the process of problem-solving by identifying the nature and cause of the problem, as a prelude to ARL evolving a practical solution. The fact that ARL quickly became effective in its role is a remarkable testimony to the likes of Albert B. Wood and Stephen Butterworth. Stephen Butterworth deserves a special mention as he was an applied mathematician with extraordinary scientific insight, able to capture and express physical effects in mathematical formulae for use by the experimenters, technicians and engineers at ARL.

Some of these specialised pieces of equipment provided general improvements in ship and submarine operations e.g. ARL’s design and development of Navigational Plotting Tables (the earliest form of ARL's course plotter being trialled in the battleship HMS Hood in 1925), and Depth Echo Sounders for safe navigation and survey. The latter stemming from ARL’s increased understanding of underwater sound as applied to ASDIC, as Sonar was then known in the UK. ARL literally turned a suck it and see black art into the science of underwater acoustics - see A.B. Wood's 1930s discoveries concerning underwater sound propagation, below.

A key piece of laboratory equipment designed by and constructed within ARL was the Rolling Table that simulated the motion imparted to a vessel by the movement of the sea. Likewise a large water tank was constructed on-site for use in (small-scale) hydro-ballistic studies. The tank was subsequently used (by A.B. Wood) to make some startling discoveries with respect to the fundamental factors of sound propagation in water. During World War II this tank, beneath the main workshop at ARL, was drained for use as a darkroom for Infra-Red work.

Throughout the history of ARL, a key aspect addressed was the detection of submerged submarines by use of underwater sound. One technique selected for further research was Echo Detection, which involves transmitting a high power sound pulse and then listening for the echo reflecting off the target. By 1927 ARL Acoustic Group’s work on Echo Detection (Active Sonar), primarily on Quartz transducers, 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 that ultimately transpired to be in favour of the submarine instead of against it. As was ARL’s research on large capacity Lead-Acid batteries for submarines that was sufficiently advanced by 1931 for the work to be carried through to conclusion by AEL.

One area of research commenced in the 1930s, that would prove to be highly beneficial to the Royal Navy, was the study of the noise radiated through the water by vessels. Whilst the Acoustics Group undertook the detailed measurement and analysis of self (radiated) noise, early study of Fluid Dynamics concentrated on 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, which was realised during the Cold War. Although significant strides were made in silencing X-Craft Midget Submarines during World War II.

Undoubtedly, ARL's research into decoupling equipment from the sea-induced motion i.e. stabilisation, and into remote control and position indication of equipment, were remarkably successful and led to the formation of Admiralty Gunnery Establishment - see ARL history 1945-77, link at foot of page.

Compass Problems
The Gyro Group (A.L. Rawlings) arrived from Greenwich in 1925, which investigated compass problems and perfected gyros which found multiple at-sea uses. See also Remote Control & Indication, below.

Ship’s Cabling Problems
In 1927 ARL (Dr Young and L. Champney) investigated the degradation with time of the insulation of ship's electrical cables requiring expensive rewiring of ships within their hull life. This work was undertaken in collaboration with AEL.

Hydro-Ballistics & High-Speed Photography
Stephen Butterworth undertook model tank experiments in support his research into the entry and trajectory of u/w projectiles - torpedoes, depth charges and aircraft-laid mines, and much of value was gained. Measurement of the drag-coefficients of torpedo-shaped bodies using 1/20th scale models were made up to 1936. The effect on trajectory of various shapes of torpedo head were studied - fired above and below the water surface. High-speed photography was used for these experiments and further developed at ARL by J.A. Craig to be widely used in many other laboratories elsewhere.

Navigational Course Plotters
An important problem in which ARL was engaged from 1924 to 1933 related to the automatic plotting of the course of a ship on a chart. Between 1930 and 1932 Stephen Butterworth was also assisted by E. H. Lakey in the development of the Type B course plotter which became standard for all ships. First fitted to HMS HOOD in 1925 it was subsequently trialled in HMS REVENGE and HMS WARSPITE where its error after a 5000nm cruise was 1% in range and 0.25deg in bearing. By 1932 five further ships had been fitted with the course plotter: RODNEY, NORFOLK, REVENGE, DEVONSHIRE & BERWICK.

Subsequently, in 1933, the Type B (to be known as the Standard Service Course Plotter) was accepted for service in all naval vessels. The (final) specification for the ARL Course Plotter was supplied to DTM, Admiralty for manufacture and supply to the navy.

Remote Control & Indication
In 1923 the group investigating fire control of naval gunnery changed its name to 'Low Power Transmission', which researched and developed various technologies for communicating control to a remote point e.g. searchlights and guns, with the highest accuracy possible. This control gear research led inevitably to the design of stabilisers for automatic neutralisation of the effects of ship motion - roll & pitch. To support the work a Rolling Table was constructed at ARL with the assistance of Messrs. Vickers, in 1927. The table was 12-ft dia. with 17-ft max. horizontal travel, and could induced +/- 5degrees of pitch and +/- 30degrees of roll, in a maximum load of 5-tons.

The Rolling Table at ARL viewed from within NPL near ARL's rear entrance

In 1927, having successfully demonstrated compressed air as the medium for remote control, ARL produced the oil transmission gear drive for guns and searchlights which was considerably lighter than their earlier systems employing air or electric motors. All components - Oil Motors, Torque Amplifiers and Oil Pumps – were designed at ARL and initially incorporated into HMS IRON DUKE and other large warships.

The ARL searchlight stabilisation gear, with (ARL designed) compound pendulum control, and oil unit drive was trialled on HMS CHAMPION where it remained until 1929 when it was taken over as 'ship's equipment'. Searchlight control gear for HMS EXETER was specifically designed by ARL and fitted in 1930.

The Oil Drive System was also used in the design of stabilised controls for Radio Direction Finders and in 1936 for Homing Beacons for the aircraft carriers: HMS ARK ROYAL and HMS Courageous.

Another successful area of research was the magnetic slip-ring indicator motor known as the Magslip. A small A.C. repeater motor, a couple of inches in diameter, gave very accurate remote indications of dial readings or the angular position of any rotating mechanism. This Magslip transmission was widely employed for fire control e.g. HMS BARHAM in 1932. Following a trail at Datchet of using the ARL Magslip transmission system between the AA Predictor and the guns, the British Army took the decision to use it for their fire control applications.

Echo Depth Sounding
In 1925 the ARL design for a shallow-water (200 fathoms max.) echo depth sounder was passed to Henry Hughes & Sons (later Kelvin Hughes Ltd) for manufacture and fitting to naval and commercial vessels. With the design and adoption of a Magneto-Strictive (as opposed to Piezo-Electric - Quartz) transducer, operating around 16kHz, in 1931, depth recordings to 450 fathoms were achieved. This design using directional high frequency sound pluses was also passed to Henry Hughes & Sons for manufacture and became widely fitted.

ASDIC
Besides echo depth sounders much work was done on Magneto-Strictive transducers and arrays for research and sonar applications. In particular researching alternatives to the use of Quartz for high power, medium and high frequency transmitters, and for receivers.

Optical Devices & Infra-Red Research
ARL's Optics Group was immediately concerned with improving a large number of in-service optical devices including Prismatic Astrolobes, various types of Binoculars and Night Glasses, Rangefinders, Tetragonal prisms, aircraft predicting instruments and height-finders. Other topics of research included a Photographic Triangulation Camera for marking 'fall of shot', Inclinometers, a Bubble Sextant for use when the horizon wasn't visible, and filming of glass surfaces in optical instruments.

ARL conducted a trial onboard HMS REPULSE in 1922 to measure the bending of an underway ship that impacts on long-range gunnery; a deflection of 60 seconds of arc was observed over a 190ft baseline.

Over the period 1925-27 ARL's Infra-Red (IR) research identified flaws in the detection of thermal emissions from aircraft engines (detailed measurement instruments were designed and constructed by ARL) but showed the potential for systems for secret signalling and station-keeping between ships at sea, to ranges of 3 miles or more.

Among the many (optical) novel features designed by ARL's Optics Group they also devised a system of transferring photographs from an aircraft to ship and shore, using TV transmission.

U/W Acoustics: Sound Propagation
AB Wood took over as Acoustics Group Leader at the end of 1927 following B.S. Smith's appointment at HMS OSPREY, Portland to oversee the implementation of the method ARL had devised for large-scale, Quartz crystal production, which had been devised by him. Under A.B. Wood, the Acoustic's Group continued development of hardware for Asdics and Echo Sounding, and new research topics included such fundamental problems as cavitation, sound propagation as modified by surface reflection and temperature gradients, measurements of sound intensity underwater and the velocity of sound in sheet materials - see ASDIC Domes, below.

ASDIC Domes
In 1927 there was an important and urgent requirement by HMS Osprey, which was addressed by ARL, for a sheet material suitable for Asdic domes. High material strength was required to withstand the hydrodynamic forces experienced at A/S vessel search speeds. Of equal importance was the requirement for the material not to interfere with the transmission and reception of the H.F. sound pulses. This work required the design of an acoustic Goniometer for measurement of the reflection and transmission characteristics of sheet material. Use of the ARL Goniometer highlighted hitherto unknown deviations from Rayleigh's classical theory of waves - see Break-through in Underwater Sound & its Propagation, below.

Ship’s Log Problems
In 1930 ARL undertook an investigation of accuracy of standard ship's log (speed indicators), resulting in a revised design by ARL being adopted by the manufacturers. Inaccuracies having been observed by AEW, Haslar and NPL from work in their test tanks.

ASDIC Transmission Power Problems
Over the period 1931-34 ARL's Acoustic Group designed and developed high frequency alternators to generate the electrical power required for (high-power) Asdic transmissions. These alternators were considerably cheaper and lighter than the valve oscillators in use. The A.C. alternators operating in the frequency range 15 to 25kHz were constructed in various sizes: 100W sets for small vessels e.g. trawlers to 7.5 kW sets for A/S vessels and for research purposes. The ARL alternator design included a novel method of accurate frequency control comprising a sensitive relay and governor.

Break-through in Underwater Sound & its Propagation
About 1934-35 ARL designed sound intensity sensors were used by A.B. Wood in small-scale experiments to investigate interference effects (Lloyd's Fringe type) between surface reflected and the direct path sound waves using the ARL tank (80ft long, 15ft wide & 10ft deep), also identified was sound wave refraction due to the presence of water temperature gradients. His pioneering work in this area became internationally recognised as it provided insight into the various factors affecting the performance of active sonar systems. The limitations in operation of active sonars were being observed at that time, but hitherto not understood.

Southern aspect of the 1939 Centre Block of ARL at Queens Road, which acquired the name "Fire Control"

With the outbreak of war in 1939, ARL's expertise was to become thinly spread and during the stress of the war years ARL investigations were often of an ad hoc nature, including such items as the determination of the characteristics of captured enemy material. To a greater extent long-term research programmes had to be put on the back-burner as very urgent naval requirements materialised.

Magnetic Mines
The first of these urgent requirements was in relation to the German's success in developing a magnetically-activated maritime mine. A.B. Wood had been transferred to the Admiralty's Mine Design Department at the time the first mine of this type was recovered and its activation mechanism investigated by him. As a result of the continuing dialogue between the Mine Design Department and ARL, A.B. Wood communicated his findings to Stephen Butterworth, the acknowledged expert in the field of electro-magnetism at ARL, in order that a countermeasure could be devised. Such was the urgency that HMS VERNON, the Royal Aircraft Establishment (RAE) and Vickers (see Note 4, below) were also involved in conceptual designs for countermeasures against the magnetic mine. The two schemes that exhibited promise were a passive method of degaussing vessels, and an active method of aircraft-carried electromagnetic sweep.

Both schemes were assessed by Stephen Butterworth and his recommended implementations were eventually taken-up. As Stephen Butterworth revealed, the original designs for both schemes lacked fundamental understanding of the polarisation of magnetic fields and their generation. Had ARL been involved from the outset, much valuable time could have been gained, which undoubtedly would have reduced the (naval and commercial) vessel losses. As it transpired, considerable success was achieved once countermeasures designed to ARL's recommendations were employed. Although in the case of aircraft-carried sweeps the success was rather short-lived as the Germans incorporated more sophisticated activation methods in their mines; particularly combined acoustic and magnetic activation. A.B. Wood and Stephen Butterworth carried out trials at RAE Farnborough of the aircraft based magnetic sweeps using the actuation mechanism recovered by A.B. Wood from the German mine.

Peter Wright ex-MI5 of "Spycatcher" notoriety stated that whilst working at ARL he had responsibility for the work on ship degaussing - see Note 5, below.

Low magnetic signature and (active) degaussing of vessels continues to be a first order (maritime) mine countermeasure.

Infra-Red Devices
The other major absorber of ARL resources was Infra-Red (IR) sensing devices for detectors and receivers. As noted above ARL was previously involved in IR sensor research in 1925, however the Experimental Department of the HM Signal School (HMSS) had been continuing their work and met with some success e.g. IR signalling ranges of 9 nautical miles.  Until 1938, there was little military interest in IR outside the Admiralty, the main exception being some Air Ministry work carried out at the Clarendon Laboratory, Oxford, by Dr. R. V. Jones, in about 1937, which was concerned with thermal detection of aircraft - see Note 6, below.

In 1938, the Admiralty were asked formally to undertake inter-Service (Navy, Army and Air Force) responsibility for IR research and development as an increased importance was placed on the ability to see in the dark, detect thermal emissions, and to communicate covertly. For this purpose a new group was formed at ARL under one of the experts in the field, Dr. E.G. Hill, who transferred from HMSS in mid-I938.

With the outbreak of war, the one stumbling block was the IR sensors themselves. Various technologies showed promise (some more than others) but the ability to manufacture reliably and in quantity was the major obstacle to the wider introduction of IR equipment into service. The ensuing ARL investigations led to the formulation of a process for constructing sufficiently sensitive IR sensors, on a large scale, with much improved reliability in performance. Initial production was set-up at ARL, however the facilities were insufficient to meet the demand for the sensors and this led to several manufacturing contracts being let to industry. ARL staff were then required to assume a quality assurance role to monitor sensor production and rectify the problems arsing from the manufacturing practices employed by the contractors.

The HM Signal School, and, to a lesser extent, the corresponding establishments for the other Services, continued to be responsible for the service equipment.

Anti-Submarine Weapons
In October 1941 the Admiralty Research Laboratory was asked to assist in increasing the stability and rate of sinking of the standard Mark VII depth charge and to develop the design of an entirely new forward thrown weapon. The Mark VII depth charge rather resembles a 50 gallon oil drum and its underwater behaviour had been described as that of a falling leaf, but eight months later the weapon had been stabilised and its terminal velocity' increased nearly three times. Also, building on the same cylindrical form the prototype design of an entirely new forward thrown weapon was well advanced by working on the principle that it is better to get a reasonably efficient weapon into service quickly than spend a long time on changes which might only slightly improve its performance. This new weapon became known as Squid and its first "kill" occurred in August I944 when HMS LOCH KILLIN sank the submarine U736.

X-Craft Midget Submarine Noise Reduction
The Acoustics Group at ARL had embarked upon a study of the in-water sound made by the propellers and machinery of submarines with the aim of reducing the radiated noise, thereby making Royal Navy submarines far more difficult to detect. Another important advantage of (self) noise reduction was the beneficial effect on sonars fitted to submarines; it meant there was less background sound (when passively listening) to mask the reception of the noise made by target ships and submarines, or to mask the (actively) transmitted sound reflected by them i.e. their echo.

Throughout WWII, ARL made great advances in vessel noise reduction having established its first Noise Range at Loch Goil, Argyll, Scotland in 1942. In the case of the X-Craft midget submarines their main machinery was mounted on a raft attached to the hull by resilient mountings designed by ARL. The consequent reduction in noise resulted in the range at which they could be detected falling from 10,000 to 200 yards.

Acoustic Countermeasures
A considerable proportion of ARL’s contribution during WWII was in terms of consultancy to other establishments on the design and effectiveness of countermeasures to German submarines and torpedoes. One of ARL’s individual contributions was the ‘Publican’ decoy for the German acoustic homing torpedo codenamed ‘Gnat’.

Notes