The Use and Level of Computers During WWII

By: King Arthas

Part I – Introduction to WWII (War) Technology

The Second World War was undoubtedly the most disastrous war the earth has ever seen. It cost many millions of lives to both Allies and Axis. It is known that after a war ends there are no winners or losers among people. This is something that experts believe that in this case (Computer) Technology was the only positive step we made. In times of fear and insecurity people think quite differently than they normally do. For one more time Human Intelligence proves to us the divinity of its nature. With this article I will introduce you to a few Computer systems that where invented and widely used during WWII for a variety of projects. But first of all I will introduce you to (Hacs and Mark VI Director) showing a few things about what they could do and how they functioned.

HACS, an acronym of High Angle Control System, was a British anti-aircraft fire-control system employed by the Royal Navy from 1931 onwards and used widely during World War II. HACS calculated the necessary “aim off” required and placed an explosive shell in the location of a target flying at a known height, bearing and speed.

Early History (HACS)

The HACS was first proposed in the 1920s and began to appear on RN ships in January of 1930, aboard the HMS Valiant. HACS did not have any stabilization or power assist for director training. HACSIII which appeared 1937, had provision for stabilization, was hydraulically driven, featured much improved data transmission and it introduced the HACS III Table. The HACS III table (computer) had numerous improvements including raising maximum target speed to 350 knots, continuous automatic fuse prediction, improved geometry in the deflection screen, and provisions for gyro inputs to provide stabilization of data received from the director.

Development Operation

The earliest versions of the HACS could not generate true target motion, by computer prediction, through direct measurement of target speed, bearing, and altitude, so they were not “tachometric” systems, and made the assumption that the target speed, direction and altitude would remain unchanged from the time of prediction until the fired shell reached the target, which was a flaw common to most pre-WW2 AA computers. Instead the HACS Mk I through Mk IV generated predicted target motion based upon estimates of target speed by target type, and target direction by aligning a binocular gratitude with the target aircraft fuselage, and the measured values of target bearing, target range and target altitude. The HACS would use this information to create a predicted target motion or Range Rate (often called Rate Across in RN parlance), which is the apparent target motion across the line of sight. The predicted Range Rate was then used to move the High Angle Director Tower (HADT) UD4 Height Finder/Range Finder prisms via electric motor so that the UD4 operator would see the target being held apparently motionless in his instrument eyepiece. If the target had apparent movement, the UD4 operator would adjust the range/height and in so doing would correct the generated Range Rate, thereby creating a feedback loop which could establish an estimate of the target’s true speed and direction, within the limits of optical ranging accuracy. Target ranging output also generated a paper plot of the range on the computer itself in the High Angle Calculating Position (HACP) located below decks, so that a range rate officer could access its accuracy. The HACS predicted target position for gun orders by modeling target position and movement using the “ellipse method of calculating deflection”. 2D analogue of 3D target position and direction was created by projecting an ellipse onto a ground glass screen. The shape of the ellipse would vary with target altitude and speed. The intersection of the ellipse and the target direction was used as a basis for calculating elevation and training of the guns. The ellipse method had the advantage of requiring very little in the way of mechanical computation and essentially modeled target position in real-time with a consequent rapid solution time.

Target Drones

The HACS was the first Naval AA system to be used against radio controlled aircraft, and achieved the first AA kill against these targets in 1933. In March 1936, six Queen Bee targets were destroyed by the RN Mediterranean Fleet during intensive AA practice at a time of extreme tension between the UK and Italy. Target practice against target drones was done by using special shells which were designed to minimize the possibility of destroying expensive targets. The RN allowed media coverage of AA target practice and a 1936 Newsreel has footage of an actual shoot. In 1935 the RN also began to practice HACS controlled shoots of target aircraft at night.

Radar and the Mark VI Director

HACS used various director towers that were generally equipped with Type 285 as it became available. This metric wavelength system employed six yagi antennas that could take ranges of targets, and take crude readings of bearings and altitude using a technique known as “lobe switching”. It could not however “lock on” to targets, and therefore was unable to provide true blind fire capabilities, which no other navy was able to do until the USN developed advanced radars in 1944 using technology transfers from the UK. This situation was not remedied until the introduction of the HACS Mark VI director in 1944 that was fitted with centimetric Radar Type 275. Another improvement was the addition of Remote Power Control (RPC), in which the anti-aircraft guns automatically trained with the director tower, with the necessary changes in bearing and elevation to allow for convergent fire. Previously the gun crews had to follow mechanical pointers that indicated where the director tower wanted the guns to train.

Ship gun fire-control systems (GFCS) enable remote and automatic targeting of guns against ships, aircraft, and shore targets, with or without the aid of radar or optical sighting. Most US ships destroyers or larger (but not destroyer escorts or escort carriers) employed GFCS for 5 inch and larger guns, up to battleships such as the USS Iowa. After the 1950s, GCFSs were integrated with missile fire-control systems and other ship sensors.

The major components of a GFCS are a manned director, with or replaced by radar or television camera, a computer, stabilizing device or gyro, and equipment in a plotting room The brains were first provided by the Mark 1A Fire Control Computer which was an electro-mechanical analog ballistic computer that provided quick and accurate near real-time first-shot hit firing solutions which could automatically control one or more gun mounts against stationary, or moving targets on the surface or in the air. This gave American forces a technological advantage in WWII against the Japanese who did not develop this technology, and still used visual correction of shots with colored splashes. Digital computers would not be adopted for this purpose by the US until the mid 1970s. However, it must be emphasized that all analogue AA fire control systems had severe limitations, and even the USN Mk 37 required nearly 1000 rounds of 5″ mechanical fuse ammunition per kill, even in late 1944. The MK 37 was the first of a series of evolutionary improvements in gun fire control systems.
Many of the above may not be completely understood by many unfamiliar to war machines but it provides you a general theory about smart mechanical units that scientists invented during an era of tremendous changes and the fear of death. However, in later parts I will make an attempt to present you a few more details about Computers, and how functional for the time they proved to be.

Two of the most important computers and their main purpose

This is the second part of Use and level of Computers during WWII. In this part I believe that it would be dishonorable if I wouldn’t make a reference to the two most important computers used during WWII, and these were ENIAC for the ALLIES and COLOSSUS for the AXIS. These two Computers worked as big advantages for the two sides. Such Computers were mostly used for code-breaking and cryptanalysis. Because as it is basically known this is such use is offered because of the tremendous speed and memory computers posses instead of a human brain. Computers are used for many functions and can be reprogrammed any time we want. That means that humanity has the ability to use them again and again for any type of process they want to make but of course they first need to be taught on how to do it…

As it is logical there are many more fields of use for computer however, referring to all of them is a selection that would make this article more incomprehensible. That is why I will avoid it..
The tremendous speed of a Computers CPU is based on the high amounts of power they use, something that also causes big problem to power supplies nowadays. The problem of power supplies is clearly a matter that didn’t concern people 70 years before.

As I have already announced in the previous part of the article, I will not touch on how these two machines worked but I will tell you a few general things about them such as dates and names to honor the Creators of them. This is because a lot of computistic details wouldn’t offer a clear view about the main theme…

COLOSSUS (AXIS)

The Colossus machines were electronic computing devices used by British code breakers to read encrypted German messages during World War II. These were the world’s first programmable, digital, electronic, computing devices. They used vacuum tubes (thermionic valves) to perform the calculations.

Colossus was designed by engineer Tommy Flowers with input from Allen Coombs, Sid Broadhurst and Bill Chandler at the Post Office Research Station, Dollis Hill to solve a problem posed by mathematician Max Newman at Bletchley Park. The prototype, Colossus Mark 1, was shown to be working in December 1943 and was operational at Bletchley Park by February 1944. An improved Colossus Mark 2 first worked on 1 June 1944, just in time for the Normandy Landings. Ten Colossi were in use by the end of the war.

The Colossus computers were used to help decipher teleprinter messages which had been encrypted using the Lorenz SZ40/42 machine—British code breakers referred to encrypted German teleprinter traffic as “Fish” and called the SZ40/42 machine and its traffic “Tunny”. Colossus compared two data streams, counting each match based on a programmable Boolean function. The encrypted message was read at high speed from a paper tape. The other stream was generated internally, and was an electronic simulation of the Lorenz machine at various trial settings. If the match count for a setting was above a certain threshold, it would be sent as output to an electric typewriter.

ENIAC (ALLIES)

ENIAC, short for Electronic Numerical Integrator and computer, was the first general-purpose electronic computer. It was a Turning-complete, digital computer capable of being reprogrammed to solve a full range of computing problems. ENIAC was designed to calculate artillery firing tables for the U.S. Army’s Ballistic Research Laboratory, but its first use was in calculations for the hydrogen bomb.
When ENIAC was announced in 1946 it was heralded in the press as a “Giant Brain”. It boasted speeds one thousand times faster than electro-mechanical machines, a leap in computing power that no single machine has since matched. This mathematical power, coupled with general-purpose programmability, excited scientists and industrialists.
The ENIAC’s design and construction were financed by the United States Army during World War II. The construction contract was signed on June 5, 1943, and work on the computer was begun in secret by the University of Pennsylvania’s Moore School of Electrical Engineering starting the following month under the code name “Project PX”. The completed machine was unveiled on February 14, 1946 at the University of Pennsylvania; it was formally accepted by the U.S. Army Ordnance Corps in July 1946.

ENIAC was conceived and designed by John Mauchly and J. Presper Eckert of the University of Pennsylvania.

German Enigma encryption machine

Electronics rose to prominence quickly in World War II. While prior to the war few electronic devices were seen as important pieces of equipment, by the middle of the war such instruments as radar and ASDIC (sonar) had proven their value. Additionally, equipment designed for communications and the interception of those communications was becoming critical.
Digital electronics, particularly, were also given a massive boost by war-related research. The pressing need for numerous time-critical calculations for various projects like code-breaking and ballistics tables accentuated the need for the development of electronic computer technology. The semi-secret ENIAC and the super-secret Colossus demonstrated using thousands of valves (vacuum tubes) could be reliable enough to be useful, paving the way for the post-war development of stored program computers.

The United Kingdom and the United States were the leaders in electronics. The US center for basic radar development was the Massachusetts Institute of Technology Radiation Laboratory. The British developed the cavity magnetron which gave a high power source of microwaves suitable for radar, and which is now used in microwave ovens.
Electronic and optical countermeasures such as jamming and radar absorbing material were developed.
While the war stimulated many technologies, such as radio and radar development, it slowed down related yet non-critical fields such as television and radio.

Cryptanalysis

Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information which is normally required to do so. Typically, this involves knowing how the system works and finding a secret key. In non-technical language, this is the practice of code-breaking or cracking the code, although these phrases also have a specialized technical meaning.

“Cryptanalysis” is also used to refer to any attempt to circumvent the security of other types of cryptographic algorithms and protocols in general, and not just encryption. However, cryptanalysis usually excludes methods of attack that do not primarily target weaknesses in the actual cryptography, such as bribery, physical coercion, burglary, and social engineering, although these types of attack are an important concern and are often more effective than traditional cryptanalysis.
Even though the goal has been the same, the methods and techniques of cryptanalysis have changed drastically through the history of cryptography, adapting to increasing cryptographic complexity, ranging from the pen-and-paper methods of the past, through machines like Enigma in World War II, to the computer-based schemes of the present. The results of cryptanalysis have also changed — it is no longer possible to have unlimited success in code breaking, and there is a hierarchical classification of what constitutes a rare practical attack. Methods for breaking these cryptosystems are typically radically different each era, and usually involve solving carefully-constructed problems in pure mathematics, the best-known being integer factorization.

Cryptanalysis  is the most widely known use of computers during the WWII. Their great power and undisputable speed was based on the  human programmer’s knowledge at that time. Something which I would like to make a reference to in the 3rd last part of this article….

To be continued.

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