President Kennedy decreed in 1961 that the United States (USA) would put a human being on the moon in that decade. This placed considerable pressure on NASA engineers who were designing the Apollo XI. The design of the Lunar Excursion Module (LEM) was an extremely difficult challenge for the control engineering of the 60s, especially where the computational capacity of that time was much less powerful than the current one.
The 8088 microprocessor that served as the basis for the IBM PC, released in 1981, just a decade after the Apollo 11 trip to the Moon, had eight times more memory than the guiding computer (16k vs 2k of the AGC Apollo) 1. The IBM PC XT ran at a dizzying clock speed of 4,077MHz. That is 0.004077 GHz. Internally, the architecture of an 8086 microprocessor had 8 registers of 16 bits available to work. It could track eight records, while the ACG only four.
Currently a processor of a smartphone of 1000 mhz and 512 MB of RAM, has 100,000 times more RAM than the AGC Apollo Guidance Computer (which ran at around 1 mhz). The recent iPhone 6 released by Apple Computers operates at 1.4 GHz and is capable of performing 3.36 billion instructions per second. The Apollo AGC guiding computer on board the lunar module (LEM) executed instructions at a speed of around 40 KHz (or 0.00004 GHz).
NASA had access to some of the most powerful computers of the day at the time, five models of IBM 360/75 mainframe computers, each approximately 250 times faster than the AGC. They ran almost in 24/7 mode, calculating data and initial elevation orbits, monitoring biomedical data during the mission, and performing numerous other calculations. The Apollo AGC guiding computer on board the lunar module (LEM) executed instructions at a speed of around 40 KHz (or 0.00004 GHz). NASA had access to some of the most powerful computers of the day at the time, five models of IBM 360/75 mainframe computers, each approximately 250 times faster than the AGC. They ran almost in 24/7 mode, calculating data and initial elevation orbits, monitoring biomedical data during the mission, and performing numerous other calculations.
The lunar module was a two-stage spacecraft designed for the moon landing during the Apollo program. Known first as LEM, the initial idea was due to John C. Houbolt of the Langley Research Center, who presented it with Charles Mathews of the Marshall Space Flight Center on February 6, 1962, in response to the lunar descent program based on the encounter in orbit of the LOR type of the Apollo program. 2
As the Apollo program progressed, engineers were asked to fit the computer into a space of half a cubic foot and weigh less than 75 pounds. A sketch of the computer of that time would reflect a scheme of a current PC. The engineers of that time determined that for precise control the data of the sensors would require 15 bits per word and that it should store 2000 words of data values.
The programmers determined that the control program would require around 37,000 storage words if each word consisted of 15 bits. Given the technology of the early 1960s, engineers considered implementing the computer entirely with transistors or even with vacuum tubes. However, both could have taken up more space and consumed more power than the integrated circuits currently available. It would have been ideal to use integrated circuits during that time, but the technology of that time had not yet been designed.
The AGC, was the most advanced in its time, had 2K words of random-access RAM memoryand 36K of read-only ROM memory 1. It processed tasks at a speed of 1 MHz and its main program was called Colossus 249, a software in charge to perform the calculations for the details of the flight. The system memory of the Apollo’s guidance computer consisted of a read-only memory used to store the program and read / write type read / write memory to store the data. The computer had to store 2048 15-bit words of data in read / write type memory.
The team had 2048 words of RAM and 36,864 of ROM. The length of the words was 16 bits. While the AGC was guiding the astronauts on the ship, on Earth NASA worked with huge IBM “360 Model 75” mainframes for communications with the ship and the calculations required to launch the lunar module off the surface of the ship. Moon and send it back to Earth.
In the 60s the human used to look up and towards the stars with an immense passion for the mystery of the infinite. The computational capacity that allowed the first planetary exodus to this civilization was not found in the computers of that time but in the brains and hearts of the people who worked with great passion to achieve this great challenge of the technology of humanity of that time and of all the humanity that lived this great feat. Millions of people from all over the world tuned their televisions to observe the great deed of humanity with much more passion than the current generations that vibrate watching football players losers.
Almost 49 years have passed and our civilization looks down, permanently towards social networks and carrying out rapid processes and in many cases without any greater reasoning and mainly to “chat”.
Author: PhD. Fernando Jimenez Motte