The Computer Hack That Saved Apollo 14

Apollo 14 almost never made it to the lunar surface thanks to a hardware failure which caused a short circuit in the abort switch. With the computer seeing the abort switch enabled the software team back on earth had a limited amount of time to figure out how to make the computer ignore the erroneous signal while still performing the landing. This required tweaking program state in memory while the program was running, a delicate operation with dire consequences for failure. No pressure guys.

[StormSilvawalker]

Nasa safety check: we have a possible issue involving the "Burn Baby Burn!" command.

Everyone: *turns slowly to that one guy who would call the engine ignition command that*

[mortcs]

As a hardware guy I think Apollo 13 was the greatest helldesk call in history. It had everything from bad reception, thermal hardware failures, cranky customers, computer reboots, hardware/process hacks and yes even a firey decent.

[JustWastedHoursHere]

I saw a T-shirt once that had an octal joke on it:
"Why do programmers get Christmas and Halloween confused?"
"Because DEC25 = OCT31"

Very clever, I thought!

[dewiz]

I remember this when it was happening. I was amazed, and confused at how they could “reprogram” at a Lunar “arm’s length”. At about the same time, I was working on a computerized typesetting machine (Photon Pacesetter), which had for-bit words. The machine developed a hardware problem with the character flash power supply. I was able to access the computer via a control panel, keying in values which slowed the machine so the flash power supply was able to recover for the next character. The machine ran at about 1/3 speed, but we got the paper out, and the next day, the repair technician replaced the power supply. I was so impressed with having been able to “fix hardware” with software, that I eventually made software my career.

[noodlesthest]

"Houston we have a problem"
*Indian voice* "Hello sir my name is Rajheed how may I help you today?"

[Adamzychu]

The only one appreciated tech support guy in the history of tech support guys.

[indianajones]

Well researched video!

In the case anybody wondered, on Apollo 15 and later the astronauts had a very easy way to tell the AGC to ignore the abort button and the abort stage button. That way the same issue couldn't have happened again. The AGC specialists developed a bunch of procedures for all the different switches that interact with the computer. So if any of these switches became faulty, they were prepared for it.

[tmage]

I knew I could count on Scott to use "computer hack" in its original context

[helge]

The issue was actually caused by a small metal fragment left in the switch at assembly. In low gravity it floated around and could shorten the switch contacts on every acceleration. Source: Gene Kranz, 'Failure is not an option'.

[LordFuturama]

A little bit OT but I recently notices KSP saying "flying safe" in the loading screen - i love it!

[Pieh]

7:37 Manley.exe has stopped responding. End program?

[OriginalToma]

I truly enjoy stories from the history of computer science. This kind of ultra low level command of wire jungles flying space ships to the Moon has such an appeal to me.

And Scott, you are an incredible YouTuber and an all around awesome human being (from what we see in the videos!). You just can't fake the passion for spaceflight that you have. Fly safe!

[patrick]

And THIS is one of the reasons I subbed. So many well-researched space shenanigans and, of course, checking the staging

[GreatgoatonFire]

Those woven memory units looks like some bonkers sci fi. Pretty cool.

[mikestewart]

Great video! Don is still around and is still awesome. The listing shown in the video is from Don's own personal collection, which he has allowed us (at the VirtualAGC project) to have scanned over the course of the past year. We actually just finished transcribing the last of them, Zerlina 56, this week. Other great programs Don has given us include:
* Aurora 12, a "fork" of the LM system test program, which has enabled us to greatly improve the accuracy of our emulator
* Sunburst 37, an early development build of the Apollo 5 software
* Sunburst 120, the flown Apollo 5 unmanned LM software
* Luminary 69, almost the flown Apollo 10 LM software (69 Rev 2 is what flew; this one is missing a last-minute lunar gravity model change)
* AP11ROPE, a 1970 remake of the Apollo 11 software (which has increased our confidence that Luminary 99 Rev 1, which we've had for a while, is what actually flew)
* Luminary 116, the flown Apollo 12 LM software
* Luminary 131 (shown in the video), an early release for the Apollo 13 LM (this underwent many changes before flying, however)
* Luminary 210, the flown Apollo 15-17 LM software

He actually has more listings than every other source we've had put together! In an ironic twist of fate, Apollo 14 is one of the only two LM missions he doesn't have software for (the other being Sundance from Apollo 9). We're still searching for it though!

[Voodoodrul]

THIS is the kind of content I love. Thanks Scott!

[oasntet]

"You have six seconds to key this in after the engines fire. And whatever you do, don't make a typo."

[jackalovski]

Was his first response "just switch it of and on again"?

[LTRacing]

I got to literally touch one of these computers as an intern at NASA this summer....pretty awesome

[ramonalonso]

Scott, you take me back to my youth. I was a member of MITs Apollo project (the older I get, the better I was). Your are right, Don Eyles was one of the essential geniuses, second only to Hal Laning, who architected runing 6 or 7 layers of interrupt on that little computer.
My claim to fame was that (early on) I proposed and did the early work on the core rope (hard to break code you cannot change), as well as the DSKY concept with Verb & Noun and the scheme for getting the angle and velocity increments without having to execute a subroutine. IBM labeled that scheme "cycle stealing, " which I thought was brilliant.
So many people were "essential!" What a priviledge (and luck) for me to have been part of that project!
Ramón Alonso