Apollo Guidance Computer Activities

AGC - Conference 1: Eldon Hall's introduction

Apollo Guidance Computer History Project

First conference

July 27, 2001 

Eldon Hall's introduction

ELDON HALL: My history started at the lab in '52 and I spent 35 years there. I think the reason why I got all the exciting jobs I did is because I was in the right place at the right time.


ELDON HALL: Like I guess all of us. But I was hired from Harvard also, so I wasn't prejudiced when Ramon Alonso and Al Hopkins came from Harvard, like some of the other MIT grads probably would have been. So I maybe paved the way.

But I was in the Physics Department, and in the Physics Department at Harvard, and all the way through school, I never heard of other number systems. Only once in a class, one Harvard professor said "When we get digital computers, we will be able to solve these equations we couldn't even solve." That's the only thing I heard about a digital computer until I got to Draper lab. So I grew up on the job.

I was on Polaris as some people had mentioned, and the computer for the Polaris. And then getting to the Apollo computer, I guess my first significant contribution, I was called upon to make the presentation in front of Frick who was the program manager for Apollo at that time, to justify changing the computer to integrated circuits. That was in the fall of 1962.

So I had to make that presentation, and Dr. Draper's comment after that presentation was that I was the best sales pitch he had ever heard. I don't know why, but anyway -- We were allowed to use integrated circuits, I guess, because of that sales pitch.

Then, well, you've heard most of the Apollo. We've gone through the Apollo. It was a very exciting program, of course. I was mainly, I like to think of myself as the father, because I had lots of people like Ray Alonso, and Al Hopkins, and Dan Lickly and Margaret Hamilton, that were really doing the work. I wasn't doing anything. So I was the father of the whole activity, I guess.

After Apollo, things kind of went downhill for me professionally, fortunately or unfortunately anyway. There wasn't anything exciting. I did a little bit on the shuttle, a little bit on fault-tolerant computing. And ... (inaudible) during the early stages of microprocessors and that kind of stuff, but nothing compared to going to the moon.

After I retired, in 1988 I wrote the book, which maybe many of you have seen, Journey to the Moon. Since then, since that's been published, I have been trying to answer questions by  e-mail. A lot of them are the questions that this project should be answering. One of them was kind of interesting. There was a young man in Venezuela -- 

DAVE HOAG: Jose -- 

ELDON HALL: Jose, yes. He was the most persistent, and is still persistent.

DAVE HOAG: He should have been during the design review sessions. 

ELDON HALL: He certainly should have. He found enough on the Internet to prove that I had a technical error in my book, which I argued about with him for a long time because I didn't believe he was right. The error is this, which might be of interest. For Apollo, I think it was 14, whichever one where Grumman had a switch that had a particle in it, the abort switch, it had a particle in it so it was disturbing the computer.

Draper lab had to write a little routine to send up to the Apollo computer to work around that. In my book initially I said that went up by the up-link. It was designed, the up-link was designed to do that kind of thing. It was Ray Alonso's scheme. Everything worked perfectly. Send it up by up-link.

But they didn't do it that way. Mission control wouldn't trust the up-link. They sent it up by voice, and the astronauts keyed it in manually. And Jose proved that to me. (Laughter)  So he's found that kind of stuff on the Internet, and there is lots of other stuff there that he's found. But he's only one of many.

One of the later ones, somebody wants to build an actual Apollo computer, and he's asking me lots of detailed questions, which I can't answer without a lot of digging, and maybe can't answer him then. So there is a need for this activity and how to achieve it, I'm not sure.

But coming up to tomorrow I guess, tomorrow I'm talking at the Vintage Computer Conference here in Boston. I don't know whether you're even aware of it. It's at 10:00 a.m. in the morning, where I'm sort of summarizing all of this, and showing the video which I had put together way back in 1966 for a Hagart Electric series.

So that's how I've been spending my time since the publication of the book. It took me six years to get the book published. 

Right now I'm making about .10 cents an hour I think. (Laughter)

Margaret Hamilton's introduction

site last updated 12-08-2002 by Alexander Brown