Apollo AGC

3 Articles

Deploy Workaround Code To The Field When “The Field” Is Lunar Orbit

February 3, 2020 by 6 Comments

The Apollo missions still inspire people today, decades after they took place. A fortunate side effect of the global public relations campaign is that a lot of information is publicly available for us to review and process. We’re right around the 49th anniversary of Apollo 14 mission, so it was a good time for [Frank O’Brien] to take readers through Apollo Guidance Computer and the hack that saved Apollo 14 (while it was in lunar orbit).

Space fans would already know many parts of this piece, but [Frank] weaves it together into a single narrative around a problematic “Abort” button that was found to be making intermittent contact as the crew were preparing to land on the moon. An inconvenient timing would have unnecessarily aborted the mission, which was obviously Not Good. [Frank] brings us up to speed on AGC fundamentals, just enough to understand the technical constraints for the hack, devised within the time constraints they faced.

For those that prefer a short video summary [Scott Manley] covered this same hack on YouTube. And for another perspective on the scope of this task, remember this was years before we had vi or emacs. When they were contemplating flipping status bits as programs were running, it’s not trivial to do a global search for code that might examine those bits. Look at the tome of source code AGC programmer [Don Eyles] worked with. Space fans who want to learn more can check out [Don]’s book.

For the ultimate AGC talk, check out The Ultimate AGC Talk.

Maybe someday trips to the moon will be a commonplace thing, but Apollo will always be the pioneer.

Restoring An Apollo Guidance Computer

November 17, 2018 by 7 Comments

The Apollo Guidance Computer is a remarkably important piece of computing history. It’s the computer that guided the Apollo lander to land on the moon. We’ve seen a few replica builds over the years, but [CuriousMarc] got a closer look at one of the real things. In this video, [Marc] gets a look inside as his colleagues take apart one of the original AGCs and get a closer look at the insides of this piece of computer history.  Continue reading “Restoring An Apollo Guidance Computer” →

An Apollo Guidance Computer Laid Bare

November 12, 2018 by 42 Comments

An Apollo Guidance Computer probably isn’t a machine that’s likely to come the way of most Hackaday readers. The device that played such a vital role in taking astronauts to the Moon and bringing them home again is hardly a common find, even if it is one of the most iconic machines of its type and era.

[Carl Claunch] was approached to assist in the restoration of an AGC, and while he can’t reveal any information about its owner he is at liberty to document his progress. The result is a fascinating in-depth technical examination of the device over multiple blog posts, and is well worth a read for anyone with an interest in the Apollo program. It’s an ongoing progression of blog posts that are probably too numerous to list individually, but include the construction of a substitute for the DSKY control panel as well as looking at the device’s memory and construction. [Carl] then embarks on a series of posts looking at the restoration itself. This is where we see the computer in greatest detail, and learn the most about it.

If you think you might have seen [Carl]’s name here before, you’d be right. One of his past exploits was getting the first version of FORTH running on an IBM mainframe.