World War Engineers and Scientists (part one)

Note:  Chain Home radar receiver towers and bunkers at Woody Bay near St Lawrence, Isle of Wight, 1945. This installation was a back-up ‘Remote Reserve’ station to Ventnor CH station during the Battle of Britain.

Photo credit:  https://www.iwm.org.uk/collections/item/object/205196922

This article, part one to three, covers world war engineers. This covers the scientists, the engineers and the engineering feats.

As this web-site is dedicated to technology, why not add a bit of colour by running a series of articles on the very people that enhanced our lives through war, famine and feast? A few years back I read a book on the history of rock and roll and was amazed at how the lives of these phenomenal musicians were entwined in some way or other. Yet the same course of events has to be said about all of us – our lives are not as haphazard and jumbled as we may wish to think. I’m a firm believer in visible forces, patterns in life which come about due to our own actions. And inactions. All wars inevitably come from one of our greatest sins, greed. But in war we will see some marvellous discoveries, inventions and unbelievable advances in science. Yet, to prevent war we need to persevere even more, focussing on deadly weapons and the technology behind these weapons to provide a deterrent to potential threat. The scientists chosen in this first article are all linked to the two world wars of the 20th century be it in peacetime or at war.

My favourites are Maxwell (electromagnetic waves), Hertz (existence of radio waves), Rutherford (coining alpha, beta and gamma), Einstein (the theory of relativity), Bohr (electron orbit), Planck (quantum theory), Marconi (radio telegraphy), Wilhelm Röntgen (X-Rays), Barnes Wallis (the bouncing bomb), Sir Frank Whittle (jet propulsion), Thomas Edison (thermionic effect), Nikola Tesla (wireless), Ambrose Fleming (thermionic diode), Lee de Forest (tube amplifier), Albert Hull, John Randall and Harold Boot (cavity magnetron), Russell and Sigurd Varian (klystron), John Bardeen, Walter Brattain, William Shockley (germanium transistor) to name a few.

• Marconi

Guglielmo Marconi patented the first wireless telegraphy system which was used extensively in the royal navy. Having a means to communicate inter-ship and ship to shore made shipping safer but in it lay also the darker side. Radio direction finding, although primitive, enabled enemy vessels to lock onto vessels transmitting any form of electromagnetic wave in the ‘wireless’ frequency spectrum. Fixed frequency carrier wave communication was simple and highly effective but lengthy transmissions allowed the enemy to triangulate and calculate a vessel’s position. Of course another problem was also apparent – ‘wireless’equipment also radiated their own form of interference.

The local oscillators used in hetrodyning ‘wireless’ sets could radiate via the receiving antenna and also be picked up by sensitive receiving equipment.  But Marconi wasn’t the inventor of wireless as we know it, this has been accredited time and again to Nicholas Tesla. Note the links between the discoveries and experiments of Edison, Tesla, Lee de Forest, Fleming and Marconi.  There is an overlap and no doubt any one of them could have been the pioneer of modern communication. Wireless or radio as we now know it played an instrumental part in saving and destroying lives through the last century, the maiden voyage of the Titanic is oft used to describe the use of radio in peace time to save lives. In war however radio stations are instructed by government law to shut down. Even in peace time radio stations onboard ships are shut down while the ship is in port, some authorities even sealing the radio office. In most cases this is an interference or security issue, in the two world wars it was illegal to possess a radio transmitter. The USA effectively commissioned all radio stations in WW1.

Due to the ever increasing danger of submarine activity in WW1 merchant vessels started carrying radio operators, called ‘wirelessmen’ – merchant vessels did not stand a chance against these awesome predators of the sea.  In the first world war radio direction finding found it’s mark but Marconi remained the hero.

• The magnetron wins the war

Radar (Radio Detection and Ranging) played a vital role in the second world war. Although devices used for object ranging and detection had been built before the mid 1930s, ranging and directional properties in this detection on a single system was still in it’s infancy. Hertz uncovered properties of materials that would absorb or reflect electromagnetic energy. Early detection systems consisted of a transmitter operating at a few MHz transmitting a pulsed carrier wave, a receiver designed to detect signals at the reflected frequency (fundamental) and the transmitting/receiving antenna. In early tests detection only was the prime interest and ‘radar’ used the Doppler system (e.g. the frequency of the horn on a moving vehicle drops as the vehicle passes an observer – i.e. the fundamental frequency apparent more so only when the vehicle is closest to an observer).

Doppler radio detection is the pioneer of modern aviation radar. While the USSR, USA, Germany, Netherlands, Italy France and Japan were all involved in the development of radar pre-1930s the more sophisticated radar built in the UK consisted of transmission and receiving antenna stacks plus the use of a goniometer used to obtain directional information. The goniometer in it’s simple form consists of a rotating coil inside that of a stator winding, the rotating coil indicating the bearing from zero to 360 degrees and the stator the head’s up position through two loop antennae, a forward facing loop at e.g. N-S and the other at E-W. (Bellini Tosi Goniometer). At this stage most radio range finding equipment used frequencies below 1GHz – the awesome might of the magnetron still not been recognised by the British or the Amnericans. Japan forged ahead but lacked foresight.

Research in the early 30’s seems to link mainly the Germans and Japanese to the split anode magnetron, a device which at that stage was not stable enough to possibly garner enough interest from the British. The Japanese radio engineers of the 30s were, in my research, very advanced in a lot of ways compared to their western counterpart, Hidetsuga Yagi been a prime example of their engineering de facto, his designs still been used worldwide in telecommunications today. The Yagi antenna had two very large advantages over its rivals, direction critical and reduction in signal loss. At this stage we see that designs seemed to stick to pulsed carrier wave, frequencies below 1GHz and separate transmission/receiving lines. The biggest drawback was the sheer size and weight. Lower frequencies equals bigger aerials. In a defensive role we know that the British had radar towers all along their coast line and German attacks were often severely weakened by these early warning systems but what made the British then the leaders in this field throughout the war?

The Dutch had their own radar systems developed by Philips and in many ways were more advanced than the Britsh and Americans. Sadly the Dutch fell at the beginning of the war and so most of their plans, designs and structures were destroyed to prevent it falling into German hands. The Germans had brilliant scientists overseeing their own deployment of radio ranging equipment but as it was mainly seen in defensive terms Hitler saw no urgency. The British had Randall and Boot. These two scientists took Hull’s split anode and the multi-cavity invention by Hans Hollman, incorporated eight cavities, increased the magnetic field and water cooled the higher powered device.  As the magnetron uses velocity modulation, output frequencies were in the order of a few GHz, the higher frequencies improving resolution drastically and just as importantly requiring less power to function efficiently.

A radar output is pulsed and although the peak power may be in the magnitude of many kilowatts the RMS equivalent is PRF x pulse length in microseconds x peak power which was in the order of a few watts. This meant that overall the radar became a very efficient device.  The end result was a high powered lightweight device which could be fitted to aircraft.  In my studies of radar in the early 80s we were taught that modern radar is designed around the magnetron. Whether it is correct to state this is debatable. What we do know is that without Hull, Hollman, Randall and Boot and their contribution to technology the Battle of Britain and the second world war may have had a very different ending.

The Tizard Connection:  In the early years of the war the multi resonant cavity magnetron design was secretly shipped to the United states with other top secret documents (Whittle’s gas turbine included) as part of the British war effor to get American participation and subsidy. The Bell Telephone Lab was given the task to mass produce these magnetrons which were later used in aircraft.  The first shipment oif the 10kW 10cm magnetrons were released at the end of 1940.

• Barnes-Wallis and the Bouncing Bomb

Just as surely as the allied forces saw the defensive and offensive capability of radar which the axis powers did not, there was no skimping from both forces when it came to the research and manufacture of a mass destruction bomb.  Barnes-Wallis was instrumental in the development of the “Bouncing Bomb”, termed from his design notes on a”spherical bomb – surface torpedo” which was used to destroy dams feeding hydro-electric plants in the industrialised Ruhr area. Although initial designs were around a ten tonne device there were severe limitations to the payload capability of aircraft at the time at the crucial drop height. The bouncing bomb was a back-spinning device which skipped when dropped low over the water, missing torpedo nets and sank against the dam wall using water as a medium to enhance the destructive power of the device.  In May 1943, with dam levels highest, Operation Chastise was carried out reportedly with great success. These 3 and 4 tonne bouncing bombs were cylindrical in shape (1.5m x 1.3m) and hydrostatically detonated at 30 foot but also had a 90 second timer if the hydrostatic pistols failed. Although these bombs were highly effective in use both as a dam buster as well as a battleship destroyer credit must be given to the aircrews at the time.  These bombs were dropped exactly 60 foot from the surface of the dam, telemetry been calculated via tilted downward facing lights mounted on the nose and tail of the bomber (Lancaster). When the two lights converged the aircraft was at the right height, distance from the dam wall been calculated by a yoke angled for the bombardier to focus on the twin towers on either side of the dam wall wall.  In these attacks the British lost 40% of their air crew and to this day historians are sceptical as to the success of this mission as by the end of June the German hydro-electric plants were running at full power.

• Weapons of Mass Destruction

In August 1939 Leó Szilárd wrote a confidential letter to President Roosevelt in which he described the menace of Nazi Germany’s research and development in nuclear physics and the real danger of building a weapon of mass destruction. Albert Einstein signed this letter adding weight to the eventual decision by the Roosevelt government to start their own nuclear research program, later to be known as The Manhattan Project. An engineer and political consultant to President Roosevelt, Vannevar Bush was instrumental to getting co-operation between civilian scientists and the military through the amalgamation of the National Defence Research Committee into the Office of Scientific Research and Development (OSRD) of which he was director. The American Nuclear bomb program was directed by theoretical physicist Rober J Oppenheimer. Even though scientists at the the time theorised that a nuclear bomb was possible they had very little knowledge of pure uranium-235 or plutonium, a new element and product of uranium-238.

In comes Enrico Fermi, brilliant Italiant theortician, experimenter and father of the atomic bomb. Fermi is accredited along with Leó Szilárd for the first nuclear pile (Chicago Pile 1 or CP-1) an artificial nuclear reactor. This reactor was made up of graphite blocks and uranium pellets controlled by the insertion or withdrawl of cadmium coated rods. Critical mass is obtained by using the smallest possible amount of fissile material (material that is capable of sustaining a chain reaction of nuclear fission). In a nuclear bomb the fuel is subcritical e.g. Uranium is made up of separate subcritical pieces due to their size or shape. To detonate, all these pieces must come together very rapidly e.g. a piece of uranium (a Doughnut) is fired into another piece (spike)through a pistol like barrel into another piece to reach critical mass. This method of detonation was used in the first atomic bomb on Hiroshima in 1945. (Little Boy). The universally acclaimed author Richard Rhodes writes (1986) in depth about “The making of the Atomic Bomb”, a 900 page best-seller. This not a boring science fiction novel – Rhodes did extensive research and tells it as it was. Fascinating reading.

The first nuclear test was near Alamogordo, New Mexico in July 16th 1945. This test was codenamed “Trinity”. Using a plutonium core the test bomb “Gadget” measured approximately 5′ in diameter 100 tons of TNT was used to implode this plutonium core which reached supercritical mass and exploded.