In 1969, humans set foot on the Moon for the first time. He did it thanks to a computer less powerful than your cell phone

The arrival to the Moon It was one of the scientific and technological milestones most notable of the 20th century and something that remained in those who lived and in those who did not thanks to the images and audios. Something that happened more than 40 years ago, when there were still many technological revolutions to come, such as personal computers or mobile phones. What technologies made it possible for humans to reach the Moon?

Something that is already fascinating in itself, but it is even more so if you know the details of the computers, cameras and other devices that were used in the mission, taking into account their characteristics. What technology made it possible for three human beings they reached the moonWould they walk around and tell us in the meantime? We travel in time and space to review.

like matryoshkas

The Apollo 11 mission was the eleventh of a NASA program that had a total of 22 missions (19 of them being successful), in the 1960s until 1972. Until mission 7 the launches were unmanned and mission 8 was the first to orbit the Moon, but for all of them a Saturn rocket launcher was used.

The one for Apollo 11 was the Saturn V, a rocket 110.64 meters high and weighing 2,700 tons with a tank full of fuel (the largest NASA has ever built). Depending on the stage (there were three, S-IC, S-II and S-IVB) the number of engines varied and so did the fuel, which were mixtures of oxygen, kerosene or liquid hydrogen.

But the Saturn V was not the one that reached the Moon, but rather the one that went out into space and directed the modules towards it. These modules were the command and service (CM) and the lunar (LEM); The CM contained the engine of the propulsion system that was responsible for entering and leaving lunar orbit and had space for three astronauts, and the LEM was the first ship designed to be able to fly in a vacuum, without aerodynamic capacity.

The LEM separated from the CM as it entered the orbit of the Moon and descended to its surface. It was designed to land only on the Moon since the legs were so weak that they would not support the weight of the LEM in Earth’s gravity (9.8 m/s² versus 1.6 m/s² on the Moon). There was room here for only two astronauts.

The speeds that were reached (increasing upon entering the gravitational field of the Moon) were 3,700 kilometers per hour and up to 9,000 km/h due to lunar gravity. And here comes a question: how is it possible to brake at those speeds? To enter lunar orbit, hypergolic braking was used (using hydrazine, dimethylhydrazine and nitrogen tetroxide, hypergolic compounds – which explode without a heat source) and engine shutdown.

The computers of the Apollo 11 mission

To review the computing involved in the Apollo 11 mission, we must take into account the emission and reception, that is, what was on the ground and what the aircraft carried. And it is also worth remembering that at the time a computer was far from being something domestic or common, or from fitting on a desk.

On Earth, in the Goddard Space Flight Center and the Manned Spacecraft Center in Houston, worked with the IBM System/360 75 mainfream, which (along with the 44, 91, 95 and 195) was implemented with hardwired logic instead of microcode like all other IBM S/360 models. For the curious techieshere a configuration diagram and explanation of the team.

In the ships, however, the Apollo Guiding Computer (AGC), manufactured by Raytheon and designed by the MIT Instrumentation Laboratory. This team stood out for being one of the first to use integrated circuits. There was one in the LEM and another in the CM.

The specifications of these teams are surprising not because the numbers are smaller compared to the current ones, but because even making the effort to place our minds in the 1960s, it is impressive to see that teams like this managed to carry out something as complex as a round trip to the Moon. The AGC had storage of 36,864 14-bit words and RAM of 2,048 words.

Comparing it with later equipment, more or less between the two AGCs they have approximately the same memory as what a Commodore-64 (from 1982) had, but it was about eight times less powerful than an IBM XT (from 1981, which was 4.77 MHz compared to 0.043 MHz for the AGC). In fact, a computer with half a GB of RAM has 100,000 times more memory than AGC.

But computers do not live on hardware alone, and software here has considerable weight. 300 people participated in its creation over seven years, at an approximate cost of 46 million dollars (at the time). Among them was Allan Klumpp, a mechanical engineer at MIT whose proposal for landing on the Moon reflects all calculations as well as diagrams and drawings of the situation on the dashboard.

The program was called LUMINARY and was written in MAC programming language (MIT Algebraic Compiler), but no terminal or compilation programs, this was done with some punched cards which were prepared with a kind of typewriter (and if a hole was made wrong, a new one had to be made). On the occasion of the 40th anniversary of the famous achievement, it was transcribed the code of both modules (transcribing it), where we read that Klumpp said that this was never exempt from bugs.

What is notable here is the multitaskgiven that the fact that the software allowed it was already an achievement and that it was not easy for him to carry it out. In fact, there was some alarm due to the high demand on the computers as at the time of the moon landing, which resulted in a slow response and not with all the calculations, so there was one minute of the eleven that lasted the guidance phase in the descent in which the computer did not send information to the radar.

The broadcast of the event

Many of us will have seen (and perhaps several times) the images of Neil Armstrong descending from the module little by little until touching the lunar surface or we will remember that phrase “One small step for man, one giant step for humanity.” Images in black and white and in a low quality, which could be expected of the time and that they were images from space, which even makes us wonder more how they were able to carry out communications and broadcasting.

The video format was 525 scan lines at 30 frames per second, transmitted at 4.5 MHz. They cited it in Wired in a post in which they talked about Stan Lebar, who devised a small and particular system for what was transmitted to Earth, 320 scan lines and 10 fps and that it transmitted at 500 kHz. A camera that had to withstand temperatures from 121°C to −157°C, day and night on the lunar surface.

Regarding the audio, NASA explains that although communications between the crew and control personnel on Earth were heard around the world, what was not heard were the conversations between Aldrin and Armstrong, which was recorded and saved. In fact, they specify that all the Apollo mission ships had voice recorders that were activated throughout the mission to record the crew’s conversations. Those of Apollo 11 were digitized approximately when the mission was 40 years old (and are public).

They also detail the equipment that each module carried for the recordings, Data Storage Equipment (DSE) for the command and Data Storage Electronics Assembly (DSEA) for the mole. The DSE contains what was transmitted to Earth during the entire mission, as well as data from certain periods from the lunar module when it flew separately in the Moon’s orbit. The DSEA did not work very well and the recordings are not of very good quality.

The desire to step on another celestial body was also an accelerator for the engineering. In fact, the on-board computer that we have described was one of the first with an integrated circuit, posing a challenge in terms of the miniaturization of components at the time, measuring 32 x 61 centimeters and weighing 32 kilos (computers still occupied square meters and minicomputers, predecessors of what we know as a desktop computer, were still a few years away).

A historic journey whose elements can be seen in part in the Smithsonian National Air and Space Museum in Washington DC, including the command module among many other objects.

In Xataka | How many times have we gone to the Moon and why have only 11 military aviators and one geologist set foot on it in all of history?

In Xataka | The far side of the Moon hid an icy secret. We finally know why it is so different from what we see

Images | POT