I was just wondering, as a Fortran user. As far as I know, the simulations taken in order to carry the Apollo 11 mission was written in Fortran 2. I would like to confirm this from a reliable source. Also, I would be interested in the papers, if any, published around this topic (the numerical simulations research done at that time).


3 Answers 3


I worked at the MIT Instrumentation Lab during the Apollo program. Although I did not work on that program, I knew many of the people who did.

The guidance computers for the command module and lunar landing module were each programmed in their own assembly language. The missions were exhaustively simulated on a large IBM 360 Model 75 computer, using a language called MAC-360 created by Hal Laning. It resembled Fortran in being mostly about mathematical calculations. It had a 3-line format for representing vector and matrix calculations.

At the time, Fortran was the primary programming language, especially for math. There were many others - Cobol, Algol, B (a predecessor to C), Lisp, and of course numerous assembly languages.

There is more information here on the Apollo Guidance Computer.

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    $\begingroup$ Awesome! It is true that Lisp was also used for space-travel simulations. For completion, this is mentioned briefly in mitpress.mit.edu/sicp/full-text/book/book.html $\endgroup$
    – user2820579
    Mar 17, 2014 at 1:11
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    $\begingroup$ @user2820579: That was just an academic exercise by Gerry Sussman and Hal Abelson, occurring about a decade too late for Apollo. (I was a grad student in the AI Lab when Sussman was.) $\endgroup$
    – Mike Dunlavey
    Mar 17, 2014 at 1:15
  • $\begingroup$ Hal? Perhaps namesake or inspiration for the fictional computer in 2001 A Space Odyssey? Or just coincidence? $\endgroup$
    – Anthony X
    Jun 8, 2014 at 20:18
  • $\begingroup$ @AnthonyX: What I heard was it was "Hal" (J. Halcomb) Laning. This was in the 60s, predating Sussman and Abelson. (I worked with him also.) $\endgroup$ Jun 9, 2014 at 7:41
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    $\begingroup$ @Fred: Thanks for that. It brings me back 50 years, but hey... what's age anyway? :-) $\endgroup$ Dec 24, 2022 at 19:55

In my youth, I am now retired, I worked on the apollo program at north american space and information systems in downey calif. chief contractor for the Apollo Command/Service Modules. I also worked at Rocketdyne that was a part of north american.

All the code I used and developed at that time was in fortran. The fortran programs performed analysis of test firing data, analysis of rocket processes (combustion performance, chemical kinetics, heat transfer, etc) and programs performing spacecraft thermal analysis. I am not sure of the version but I do remember fortran 4 coming out during our efforts and there were some software changes needed to accommodate that newer version.

I can't speak regarding command and control software.

Truly exciting times and an experience I'll never duplicate. I still occasionally use this "ancient" software on hobby projects. It's still the state-of-the-art.

Tom Kosvic


I too worked on the Apollo Space Program, in Downey, California. I was the operator/maintenance/repair "computer man", in charge of the Downey computer that was one of the three interfaced with each other. The three computers in Downey, Johnson in Houston, and Kennedy Space had control rooms operated by the computer that was "my baby". While I can no longer remember how to do the work Fortran and Cobol were the languages (programs) in use when I ran the computer in Downey. Not only did my computer control all of the displaying and monitoring equipment that made up the Control Room, but it was used to test the Apollo Command Vehicle. I used to eat my lunch in the Command Capsule, while I flipped switches, read displays and conducted tests. It was a great honor to have been a part of sending men to the Moon, and I am still very proud to have been an active participant. I was hired away from The Apollo by IBM who asked me to help work the kinks out of System 360...

Luke G. Conley III


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