The astronauts would input two-digit codes for verbs and nouns, to carry out commands like firing thrusters, or locking on to a particular star to re-align the ship Photo: Smithsonian National Air and Space Museum/AFP

The machine that made the moon missions possible

By Issam AHMED

We've all been there: you're working on something important, your PC crashes, and you lose all your progress.

Such a failure was not an option during the Apollo missions, the first time ever that a computer was entrusted with handling flight control and life support systems -- and therefore the lives of the astronauts on board.

Despite an infamous false alarm during lunar descent that sent Commander Neil Armstrong's heart rate racing, it was a resounding success that laid the groundwork for everything from modern avionics to multitasking operating systems.

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

Microchip revolution

Integrated circuits, or microchips, were a necessary part of the miniaturization process that allowed computers to be placed on board spacecraft, in contrast to the giant, power-hungry vacuum tube technology that came before.

The credit for their invention goes to Jack Kilby of Texas Instruments, and Robert Noyce, who co-founded Fairchild Semiconductor and later Intel in Mountain View, California.

But NASA and the Department of Defense -- which needed microchips to guide their Minuteman ballistic missiles pointed at the Soviet Union -- greatly accelerated their development by producing the demand that facilitated mass production.

"They had these incredible, absolutely insane requirements for reliability that nobody could possibly imagine," Frank O'Brien, a spaceflight historian and author of "The Apollo Guidance Computer: Architecture and Operation," told AFP.

In the early 1960s, the two agencies bought almost all the microchips made in the U.S., roughly a million all told, added O'Brien, forcing the makers to improve their designs and build circuits that lasted longer than their early life cycles of just a few hours.


Modern computers, such as the smartphone in your pocket, are generally capable of doing a myriad of tasks all at once: handling emails in one window, a GPS map in another, various social network apps, all the while ready for incoming calls and texts.

But in the early era of computers, we thought of them in a fundamentally different way.

"There wasn't a lot they were asked to do. They were asked to crunch numbers and replace humans who would do them on mechanical adding machines," said Seamus Tuohy, the principal director of space systems at Draper, which spun off from the MIT Instrumentation Laboratory that developed the Apollo Guidance Computer.

That all changed with Apollo Guidance Computer, a briefcase-sized machine that needed to juggle an array of vital tasks, from navigating the ship to running its oxygen generator, heaters and carbon dioxide scrubbers.

Instead of a computer operator giving a machine a set of calculations and leaving it for hours or even days to work out the answer -- all of this needed to be done in a time-sensitive fashion, with cut-offs, and the ability for users (astronauts) to give it commands in real time.

NASA felt it required an onboard computer to handle all these functions in case the Soviets tried to jam radio communications between ground control in Houston and U.S. spaceships, and because Apollo was originally conceived to go deeper into the solar system.

All of this required a software "architecture," much of which was designed by engineer Hal Laning.

Real-time input

It also needed new ways for man to interact with machine that went beyond the punch-card programming of the time.

The engineers came up with three key ways: the switches that you still find in modern cockpits, a hand-controller that was connected to the world's first digital fly-by-wire system, and a "display and keyboard" unit, abbreviated DSKY (pronounced "dis-key").

The astronauts would input two-digit codes for verbs and nouns, to carry out commands like firing thrusters, or locking on to a particular star if the ship, which relied on an inertial guidance system to keep its pitch, roll and yaw stable, had begun to drift off course.

O'Brien used the metaphor of a tourist who visits the US and is hungry but doesn't know much English, and might say "Eat pizza" to convey the basic meaning.

Passing the test

Apollo 11's most tense moment came during the final minutes of its descent to the lunar surface, when the computer's alarm bells began ringing and making it seem as though it had crashed.

Such an event could well have been catastrophic, forcing the crew to abort their mission or even sending the vessel spiralling out of control to the surface.

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

"The way that computer handled the overload was a real breakthrough" said Paul Ceruzzi, a Smithsonian Institution scholar on aerospace electronics.

O'Brien noted that while the AGC was puny by modern computing standards, with a clock speed of 1 Mhz and a total of 38Kb of memory, such comparisons belied its true caliber.

"With that terribly small capacity, they were able to do all the amazing things that we now think of as completely normal," he said.

© 2019 AFP

©2019 GPlusMedia Inc.

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And they accomplished all this with less computing power than my iPhone. What an accomplishment. What could these guys do with Supercomputers, AI, Quantum Computing, and the material science of today. They make us look like slackers. Mars... ?

For the bravery of the astronauts, for all the men and women who played a part and worked together to make it happen, for its time, which was more innocent and will never be recaptured.

5 ( +5 / -0 )

The Apollo code was posted to github a few years ago.

Shuttle GPCs had 108KB of RAM until about 1990.

3 ( +3 / -0 )

@Crazy Joe

For the bravery of the astronauts, for all the men and women who played a part and worked together to make it happen, for its time, which was more innocent and will never be recaptured.

Whenever you put together individual talents and persuade them to work together as a team you will get similar results. Selection of the right goal is the key.

I wonder if the word “sacrifice” ever was uttered at NASA. Possibly, but not as a motivator. Whenever I hear politicians talk about “sacrifice” I shudder as they mean my loss and not their own.

2 ( +2 / -0 )

That brings back some memories. My company sent me on a training course at Texas Instruments when I was being trained in instrument measurement and control. The measuring instruments were operated by glass valve amps.

To think such a box as in the post enabled the travel to the moon. Those astronauts must have wondered if they were on a one way trip.

When the moon landing happened I was still in my first year of training with Texas Instruments at a smelting plant.

Base stuff can work well. We measured the temperature of the furnaces with Texas instruments. Heat generates electricity in mv which can be measured. To calibrate the instrument I used an optical device (pyrometer) with a sliding glass slide with different colors. Watch the color of the fire and you had the temperature.

Love those early devices.

Moon landing was an amazing achievement.

2 ( +3 / -1 )

I believe they also had to upload commands to the device in orbit. A first ever that we do everyday today

0 ( +0 / -0 )


Sure, I've got a bridge to sell you if anyone believes this hogwash.

Till this very day, nations depend on Soyuz rockets for space launches. Well?

If the advancement in tech was to hold true and given the absurd statement that our phones have more computing power than the tin can rockets, should we be traversing the outer reaches of space? Shouldn't moon trips be something that's readily available to the masses? What a colossal mess!!

-2 ( +3 / -5 )

The modern day smart phone has much more computer power than the one in the post. It's not about flying to the moon while sitting astride an iPhone.

-1 ( +2 / -3 )

I understand they also carried slide rules on the Apollo missions. I was learning to use one at school around the same time.

0 ( +0 / -0 )

Wooden slide rules we used at school, guess kids today wouldn't know what one was. Modern calculator hadn't been made then.

1 ( +1 / -0 )

My first calculator cost the same as a month’s bedsit rent. I could then calculate my debt to 8 decimal places.

1 ( +1 / -0 )

A couple of hundred British scientists and engineers were involved in the mission.

0 ( +1 / -1 )

I wonder if the word “sacrifice” ever was uttered at NASA. Possibly, but not as a motivator.

The NASA community does make sacrifices all the time for the mission they are working. I used to sleep in a closet when I worked 12 hr shifts supporting the STS program. It was the only place that was dark and quiet enough in my home to sleep during the day. The rest of the family still had school and work during the day.

I was on-call 24/7 for years, even when a mission wasn't active. The facilities were used 24/7 for training. I don't remember being called much during the daytime, but I do remember many of the 3am calls that required me to physically go into Bldg 30S and do something. Usually it a failure of our team's subsystem. Almost always it was user-error because they'd skipped our training classes.

0 ( +0 / -0 )

I think, the point of this article is, that with all the amount of money that went into the Apollo Moon Missions, what came out from it, was not just limited to putting a Man on the Moon.

0 ( +0 / -0 )

Before Electronic calculators we used Log tables and slide rules, these were also still School curricula until the early 1980's in the UK.

0 ( +0 / -0 )

The involvement of British Scientists during the Apollo program was clearly demonstrated:

But lets not forget those of the previous arch-emeny too ... Germany:

0 ( +0 / -0 )

Wooden slide rules we used at school, guess kids today wouldn't know what one was.

I just got my old one out of the drawer (plastic not wooden), and I have to admit I've totally forgotten how to use it. I may need a refresher course.

0 ( +0 / -0 )

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