Apollo Guidance Computer

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Winston

Lorenzo von Matterhorn
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Have meant to read Digital Apollo and judging from one of the links to it in this article, I need to do so. The cause of the Apollo 11 1201 and 1202 alarms in detail:

https://books.google.com/books?id=g...v=onepage&q="Rendezvous Radar Switch"&f=false

that link found in this article:

Meet Margaret Hamilton, the badass '60s programmer who saved the moon landing


https://www.vox.com/2015/5/30/8689481/margaret-hamilton-apollo-software

Apollo Guidance Computer source code printout:

Margaret_Hamilton.jpg
 
Must be a ton of comments in the code....
All these pages of code fit in the tiny code space???
Really? 2k RAM and 32k ROM....no HDD to swap, so total code space is 32k....is that like a byte per page?
 
That's the source code. The compiled object code would have been way smaller. People actually wrote efficient code in those days.
 
That's the source code. The compiled object code would have been way smaller. People actually wrote efficient code in those days.

They had to. HP mini computer in the small college I went to from '74 to '78 had 8k core memory. Not 8 "megabytes" 8 kilobytes. Bunch a donuts on a grid. We had a couple of D17B quidance computers from the early Minuteman missiles.
https://en.wikipedia.org/wiki/D-17B. They were eventually dispersed to colleges and universities and I actually found a copy of the loose-leaf manual I was reading back then online. That hard drive was simply amazing and the class "geek"
fired one up and did a core dump. It worked. I also remember this fellow describe networking and Darpanet. The big kicker here is I distinctly recall him using the term it's an "internet-work". Historically I discovered that the term internet was
first mentioned in a December 1974 document: https://tools.ietf.org/html/rfc675. I don't know if "Al" had read that but I romantically like the idea that perchance he came up with it independently.

Years later when the term internet was more widely known, I thought back to those times in college. Heck handheld calculators just came out then and I had to ditch my SR-11 for an SR-51 first semester to keep up. Still have it and it will work when plugged into the wall wart. Kurt
 
Meet Margaret Hamilton, the badass '60s programmer who saved the moon landing

I've heard different things about what caused the 1201 and 1202 alarms. It was the Rendezvous Radar (which wasn't needed during landing except *maybe* to be ready during an abort) that was left on that caused the computer to overload and give the alarms. The different things I've heard are that it was a checklist error and a switch should have been turned to a different position during landing, or that Buzz Aldrin purposely left the RR on because he wasn't about to land without what he thought was the best way out of there.

I honestly think I remember an interview with him where he said that it was his fault the switch wasn't turned, and he skipped over that on purpose. But I've been corrected in this forum before so I don't know for sure.

Either way they got it fixed for the future landings.

Maybe they should have tried SCE to AUX?
 
Although I have read about here before, the article was nice. Thanks for sharing!
 
They had to. HP mini computer in the small college I went to from '74 to '78 had 8k core memory. Not 8 "megabytes" 8 kilobytes. Bunch a donuts on a grid. We had a couple of D17B quidance computers from the early Minuteman missiles.
https://en.wikipedia.org/wiki/D-17B. They were eventually dispersed to colleges and universities and I actually found a copy of the loose-leaf manual I was reading back then online. That hard drive was simply amazing and the class "geek"
fired one up and did a core dump. It worked. I also remember this fellow describe networking and Darpanet. The big kicker here is I distinctly recall him using the term it's an "internet-work". Historically I discovered that the term internet was
first mentioned in a December 1974 document: https://tools.ietf.org/html/rfc675. I don't know if "Al" had read that but I romantically like the idea that perchance he came up with it independently.

Years later when the term internet was more widely known, I thought back to those times in college. Heck handheld calculators just came out then and I had to ditch my SR-11 for an SR-51 first semester to keep up. Still have it and it will work when plugged into the wall wart. Kurt

I wrote code for the HP Mini, PDP8, PDP11, and a few other minis. Yes we lived in 8K of code space. I went to a class at Comdex in 1999 on the TCP/IP stack where the lecturer basically went through that RFP in gut wrenching, stultifying detail. My head still hurts. SR11? You whippersnapper, I have an SR10 - and like yours I can plug it in and it still works - almost 40 years later. Still have my 51, 52 & TI55 (Never learned to use RPN)
 
When I started college, there were no hand held scientific calculators. By the time I was a senior, one prof suggested you borrow an HP-35, which were fairly prevalent, if you wanted to be able to finish the exam. Still Have my 2nd, an HP-25 CIRCA 1977. RPN rules!
 
When I started college, there were no hand held scientific calculators. By the time I was a senior, one prof suggested you borrow an HP-35, which were fairly prevalent, if you wanted to be able to finish the exam. Still Have my 2nd, an HP-25 CIRCA 1977. RPN rules!

I love my old HP that uses RPN. It's so much easier doing calculations with it once you get the hang of it. It's too bad that can't be the standard.
 
When I started college, there were no hand held scientific calculators. By the time I was a senior, one prof suggested you borrow an HP-35, which were fairly prevalent, if you wanted to be able to finish the exam. Still Have my 2nd, an HP-25 CIRCA 1977. RPN rules!

You also did not have indoor plumbing, electricity or those fancy gas powered cars. I bet you walked barefoot and uphill to school, both ways, in the snow...
 
I do know I walked uphill both ways this past weekend to recover my rockets :eek:
 
Depends how close to the hills you are :) Let me tell you, these legs don't like high stepping through 3-4' grass! Especially uphill!
 
I wrote code for the HP Mini, PDP8, PDP11, and a few other minis. Yes we lived in 8K of code space. I went to a class at Comdex in 1999 on the TCP/IP stack where the lecturer basically went through that RFP in gut wrenching, stultifying detail. My head still hurts. SR11? You whippersnapper, I have an SR10 - and like yours I can plug it in and it still works - almost 40 years later. Still have my 51, 52 & TI55 (Never learned to use RPN)

Heck, when I started college, the SR11's abilities lasted a couple of months. My compatriots were buying the just released SR-50 and it was sorely needed to get through tests. The 51A just came out a few months after the 50 and since my fathers business at the time sold office supplies, he picked one up wholesale for me. Ewwwww...... first degree linear regression and factorials! Cripes I don't even use any of that stuff anymore.

Here's another piece of trivia. I went to a small scientifically oriented college and as far as I was concerned, boys and girls were equals when it came to scientific endeavors. Heck there was a lady math professor who was a student "at" the University of Chicago when the atom was split under the old Stagg stadium. Later worked on the Manhattan project and acquired a patent for some of her work there. Never spoke about it as those folks were sworn to secrecy. After she passed years later, mention was made of the fact she worked on the "bomb" in an Alumni journal and that she had signed over the patents to the college in the course of her career (she never married). There was a rumor circulating to that effect while I was going to school there but it was kept hush hush.

The gist of all this is I thought men and women were equal as far as the "ability" to learn science. At least that was my experience in school. Many gals were better than men in the sciences.
Hence, a newspaper vendor was staring at me one day as I was swearing at the front page of the Sun-Times that stated men were "better" than women in math and science. Bull hockey.
I just assumed some people had a better "knack" for it and sex didn't play a part in that.

Anyhow, the Social Sciences authorities said they had "data" to support that assertion (at the time?) and I acquiesced that perhaps scientifically inclined girls were attracted to Illinois Benedictine College due to the college's reputation in the fields. Soooo, that "skewed" my impression.:eyeroll:
I still don't think there is much difference between sexes. Geez, some men become lawyers for cry'in out loud 'cause they don't "get" scientific notation.
I do know a hospital administrator who educated me about the ability of one to learn calculus and I think he's right. Some people just have the knack or
right mind to "get it" more easily. He was a business major and he took 400 level math courses for fun and could ace the hell out of it. Me? I had to learn
by brute force. It wasn't easy. But now, I couldn't do an integral if my life depended on it. Kurt
 
The gist of all this is I thought men and women were equal as far as the "ability" to learn science. At least that was my experience in school. Many gals were better than men in the sciences.

I saw an interesting story a while ago that said that women and men were about equally represented in CS fields until the early to mid 80s. By then, the first kids who had grown up with the early computers were coming into college and leaving everyone else behind because they had experience from home. Those first computers were marketed as toys for boys, so relatively few girls got them. From then on, CS professions skewed male.

I'm a whippersnapper--I used my high school TI-81 for about a decade out of college, then bought a TI-83 since the 81s weren't available anymore. Several of my coworkers still have their old HPs (35?). One went so far as to buy an iPhone emulator for the calculator since his HP's power button went dead.
 
When I started work in the late 70's as a hardware guy, I found there were a lot of female programmers. This was not the demographic on the hardware side and didn't match the boy/girl ratio in college. I was further surprised when I found that a lot of the female programmers did not even have technical degrees. Kinda matches what was said in the linked article.
 
Don, I found the body of the V2. It was along the vector that you and my wife suspected. Only a couple of feet into the grass.

Thanks again for the help.
 
I've heard different things about what caused the 1201 and 1202 alarms. It was the Rendezvous Radar (which wasn't needed during landing except *maybe* to be ready during an abort) that was left on that caused the computer to overload and give the alarms. The different things I've heard are that it was a checklist error and a switch should have been turned to a different position during landing, or that Buzz Aldrin purposely left the RR on because he wasn't about to land without what he thought was the best way out of there.

I *think* I have heard the same thing {or something quite similar}. The LEM had radar for landing, AND radar that {tracked the Apollo CSM}. Armstrong & Aldrin were running both radars, but the folks who designed or programmed {or whatever} the computer had not allowed for that to be done. I guess they figured they would EITHER be landing using one OR ascending using the other....
 
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