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Saturday, May 15, 2010

How Alan Turing's Pilot ACE changed computing

On 10th January, 1954, a de Havilland Comet - the world's first commercial jet airliner - took off from Rome.

After only just 20 minutes in flight, it exploded, killing all 35 people on board.

(An employee at the Science Museum, London, stands in front of the Pilot ACE, a pre-cursor to Alan Turing's famous Automatic Computing Engine)

Months later there was another disaster, this time a Comet crashed near Naples during a flight between Rome and Cairo.

The two crashes in such short succession prompted an investigation.

Fatigued failure

It was eventually discovered, through a series of tests, that metal fatigue had been the cause of both accidents.

Testing had been carried out by building a replica aircraft in a tank of water before exposing it to high pressures - similar to the conditions it would experience in mid-air.

This required carrying out some intricate calculations - a task perfect for the Pilot ACE, the predecessor to English computer scientist Alan Turing's computer, the ACE.

We got the calculations side down to about one minute. From their point of view it was fantastic.
Tom Vickers

Tom Vickers was operations manager for the Pilot ACE. For BBC World Service's Digital Planet programme, he was interviewed by his granddaughter, Harriet, about the early days of the machine - and of computing in the UK.

"The idea of computers developed during the war, in America, and also at Bletchley where they did build special purpose computers for code-cracking.
"One of the key people there was Alan Turing, who was to design an electronic computer.

"He started off on his own, and I was encouraged to join. And so, the ideas of electronic computers developed."

Although work on the machine started in 1946, it was not until 1950 that they Pilot ACE ran its first programme.

By this point, Turing had left the project as he was, Mr Vickers says, frustrated by the speed of progress.
However, the ideas he had left behind were enough to get the project going.

"This led to the development of a machine called the Pilot ACE which would act as a starter for the full scale machine that Turing had envisaged."

Calculations for custom

After showing that the machine could be used to solve practical problems, the Pilot ACE went into public production.

Based at the National Physical Laboratory in Teddington, one of its first customers, the Royal Aircraft Establishment, was quick to use it when running tests on the metal-fatigued Comet airliners to see where the metal would crack.
"This led to an enormous amount of calculation and masses of data were collected."

Another early, loyal user of the Pilot ACE was Ordnance Survey which used it to analyse photographs used for creating maps.

"You got an aeroplane, it flew over the country, it took a load of photographs," Mr Vickers explained.
"You then analysed the photographs and could then make the maps.

"This was quite a lengthy process. Analysing one photo used to take them about a day," he said. "A good day's flying would keep you busy for many a month."

But by using the Pilot ACE, this time-consuming task was cut down to size.
"We got the calculations side down to about one minute. From their point of view it was fantastic."
As well as being useful, the Pilot ACE was highly profitable.

For the first two or three years of their mass-production, each machine was, Mr Vickers recalls, making upwards of £30 per hour.

In an era when highly respected scientists predicted that the UK could solve its computing needs with just three machines in the entire country, the Pilot ACE showed real potential of powerful computing.



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