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The machine that made possible the missions of the moon

Washington (AFP) – We've all been there: you're working on something important, your computer crashes and you lose all your progress.

Such a failure was not an option during the Apollo missions, the very first time a computer was responsible for managing flight controls and life support systems – and therefore the lives of astronauts on board.

Despite an infamous false alarm during the lunar descent that sparked Commander Neil Armstrong 's heart race, it was a resounding success that laid the foundation for everything from modern avionics to airborne systems. multitasking.

Here are some examples of how the Apollo Pilot Computer (AGC), millions of times less powerful than a 2019 smartphone, has shaped the world we live in today:

– The flea revolution –

Integrated circuits, or microchips, were an essential part of the miniaturization process of placing computers aboard a spacecraft, unlike the giant and greedy vacuum tube technology that existed before.

The merit of their invention goes to Jack Kilby of Texas Instruments and Robert Noyce, co-founder of Fairchild Semiconductor and then Intel in Mountain View, California.

But NASA and the Department of Defense – who needed bullets to guide their Minuteman ballistic missiles pointed to the Soviet Union – have dramatically accelerated their development by generating demand that has facilitated mass production.

"They had those incredible reliability requirements, absolutely foolish, that no one could imagine," said Frank O. Brien, space flight historian and author of "The Apollo Guidance Computer: Architecture and Operation."

In the early 1960s, the two agencies bought almost all the chips made in the United States, which represents about a million, added O. Brien, forcing manufacturers to improve their designs and build longer circuits as their first life cycles. a few hours.

– Multitasking –

Modern computers, such as the smartphone in your pocket, are usually able to perform a multitude of tasks at the same time: managing emails in one window, GPS map in another, various social networking applications, while being ready for incoming calls and SMS.

But at the beginning of the computer age, we thought of it in a fundamentally different way.

"They did not have much to do, they were asked to reduce the numbers and replace the humans who would do them on mechanical adding machines," said Seamus Tuohy, senior director of space systems at Draper. , which took off MIT instrumentation laboratory that developed the Apollo guidance computer.

Everything changed with Apollo Guidance Computer, a machine the size of a briefcase that had to reconcile many vital tasks, ranging from shipboard navigation, through to the oxygen generator, heaters and carbon dioxide scrubbers.

Instead an IT operator gives a machine a set of calculations and leaves it for hours, if not days, to find the answer – all of this must be done in a time-sensitive way, with cuts and a capacity users (astronauts) to give them real-time commands.

NASA felt that it required an on-board computer to handle all these functions in case the Soviets attempt to scramble radio communications between ground control in Houston and American spacecraft, and because Apollo was originally designed to go deeper into the solar system.

All this required a software "architecture", designed largely by engineer Hal Laning.

– Entry in real time –

It also required new ways for humans to interact with a machine, going beyond the punch card programming of the time.

Engineers have developed three main methods: switches that are still found in modern cockpits, a manual remote control connected to the world's first digitally controlled digital flight system and a "screen and keyboard" unit, abbreviated as DSKY. (pronounced "dis-key").

Astronauts were entering two-digit codes for verbs and names, in order to execute commands such as firing thrusters or to lock on a particular star if the ship, which was relying on a system inertia guidance to maintain its stability started to drift.

O & # 39; Brien used the metaphor of the tourist who visits the US and who is hungry but does not speak much English and who could say "Eat pizza" to explain the basic meaning.

– Take the test –

The most tense moment of Apollo 11 occurred during the final minutes of its descent into the lunar surface, when the computer's alarm tones began to ring and give the impression that it was crushed.

Such an event could have been catastrophic, forcing the crew to abandon their mission or even to send the ship out of control to the surface.

Back in Houston, an engineer realized that if the machine was temporarily overloaded, its intelligent programming allowed it to automatically do less important tasks and focus on the landing.

"The way the computer has handled the overload has been a real breakthrough," said Paul Ceruzzi, a research scientist in aerospace electronics at the Smithsonian Institution.

O & # 39; Brien noted that although the AGC was punished by modern computing standards, with a clock speed of 1Mhz and a total of 38KB of memory, such comparisons belied its true caliber.

"With this extremely reduced capacity, they have been able to do all the incredible things that we now consider perfectly normal," he said.

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