Apollo Guidance Computer History Project
July 27, 2001
Fred Martin's introduction
FRED MARTIN: My name is Fred Martin, and I started at the Draper lab, the Instrumentation Laboratory in 1956, and I stayed there 13 years.
I started out in an autopilot group working on analog autopilots and fire control systems, then found my way, one way or another, into the Polaris program, and I did a little work on control systems for Polaris.
I then became a doctoral student. I like to say I was one of the first Apollo employees, I'm not actually sure about that. But it was the summertime of 1960, I think it was, and I was given an assignment by Milt Tragesor to look at how well you could see landing sites through the atmosphere of the earth from space, and what angle you have to look through the atmosphere to see landing sites. Of course if you look straight down you can look through the atmosphere, but what kind of angles would cause lack of contrast so that you could not see landing sites?
But that didn't last very long. Thereafter, I joined a group led by Dick Battin which became the Guidance and Navigation Group, which actually had all the responsibility for the programming for the Apollo Guidance Computer. This included all of the algorithms, it included the design, the programming, the simulation, and check out for both command module and LEM. It involved the simulation of all the equations of motion on the IBM 360 computers. It involved the simulation in the lab with the real computer, and man/machine interfaces. It involved designing what we call the functional simulator, where you could simulate the actions of the computer on a 360 and run all the equations of motion for the spacecraft, and all the gravitational aspects of it, and then keep moving ahead step by step as you went through the time line. So it could take you a very long time, let's say, to simulate five minutes of AGC time, but in that time you were updating all of the equations, all the differential equations of motion of the vehicle as well as all the bending and all the sloshing of the fuel, everything. It was a very sophisticated simulation system when you look back on it today. As a result we had very good ways of checking out and running computer programs against what we liked to call the truth, which was this highly accurate digital simulation that was created under Battin's direction.
Eventually I became the project manager of the Command and Service module software. That was all of the software, I would say, starting probably in the Apollo 8 and 9 era. So I became responsible for the schedules and the organization of the programming, and what subroutines there were, and parceling out work to people who were going to program it. I reported on schedules, and on progress, and so on.
One thing that was brought up in the discussion before which I think is kind of interesting, is an occurance on Christmas day, I think. I had just dropped my family off at Logan Airport. They were going to visit relatives in New Jersey. During every Apollo flight, we would man headphones 24 hours a day in a kind of command post, you might say. We had rotating crews that would go through there, and we were ready for anything, if anything would happen. And some things did happen, and we'll get into some of those things a little bit later. But the reason I'm bringing this one is because it was a very quiet Sunday. It was just like today in the sense of being sunshine, and very quiet, but a holiday period.
So I dropped them off and went back to the lab, and sat around with Dan and Margaret. It was about 2:00 o'clock in the afternoon, and we were listening to the astronauts on the phones. All of a sudden Jim Lovell says "Oh oh." And everybody said, "What's oh oh?" He said "I think I just did something wrong." I don't know who was on the phones at NASA, and the people at NASA were all monotones. I mean, you could have an earthquake and they wouldn't say much. So he said, "What did you do wrong?" "I think I keyed in PO1 and I'm in rendezvous. Did anything happen? Is that okay?" (Laughter) Of course, they didn't know whether it was okay at NASA at all, and so they asked us. I guess we didn't know if it was okay right away but it turned out it was not okay.
And Dan leaped into action, I remember him furiously spending the next I would say hour tracing through the listing, going through the situation of what would happen if you were in rendezvous and you keyed in PO1. It was quite a detective adventure. It turned out that Lovell had wiped out all of his erasable memory and all of his navigation, the correlations that he had been taking up, and all of the settings that he had done. He had pretty much corrupted the whole memory.
So we spent the first hour getting calls from NASA every five or six minutes asking "what did he do, what did he do, what did he do? Because he doesn't have any navigation data, if he lost everything, he would be alone. I don't know how many communication modes they must have had, five communication modes, they'd have to lose one, then two, then three.
So we did figure that out, but it took quite a while. Then there was the slow process of telling him how to bring things up, and him to take new sightings and so on. That was what happened for three hours on a quiet, Sunday afternoon.
Those things happened, and other things happened of that nature too. But I would like to say that the environment at the lab was very unique. I can only say that in retrospect because I had not worked before -- I went from a college student in 1956, and there I was at the lab until I left and joined a small company in Cambridge. But it was a very unusual environment, I think. Incredibly dedicated people would work 24 hours a day, or 18 hours a day for days on end for, I would say, no extra pay or anything.
There was a feeling of national urgency, you might say, of national responsibility, and the fact that you had the astronauts coming to the lab regularly for instruction, just sitting in classrooms, just talking to people. You had the pressure of what was going on. It was really an incredible experience for, I think, everybody that was there. The fact that you were building something that you knew that was going to be used; it wasn't a study. It wasn't a series of notebooks that would sit on some general's desk, or some other thing that nobody would use, or a trade off study or something. This was something that they were going to use.
And compared to the way things are done today, you know, if we had a problem, we didn't know how to do something, we would get in a room, a blackboard, four people spend an hour or two, decide how to do it, then do it. Or we'd ask NASA, some people, very bright people down there what they thought, I'm thinking of a couple of people we worked with all of the time, and we'd just do it.
Eventually that sort of loose environment changed, and it became much more rigorous, and with much more documentation, and much more design, and design reviews and things like that. I'm not suggesting in any way, shape, or form that that was bad that that discipline came into the program, but at the beginning of the program you just had a bunch of good ideas and you just did them.
Today I think, and I've heard this from others, that if we had to do this program today, in the manner in which programs are done today, I don't think the program could ever be done. I don't think that the amount of paper generated, the meetings, the reviews, the number of people involved -- I don't think the program would have ever gotten off the ground. Or instead of costing whatever it cost, $20 billion dollars, it would have cost $100 billion dollars in the same kind of dollars.
DAN LICKLY: Let me add to Fred's. You mentioned, I mentioned how old he was. I was going to say most of the people during that design phase in the early 60's up until whenever, the design development phase was done by a bunch of people who all weren't yet 30. They were all very young, working, very wrapped up on it, and young enough not to be frightened by mistakes they might make, or too dumb to notice how dangerous this all was.
But it was a very productive and exciting place to be. Ray for years always said, "Why can't I find another Apollo?" Because a lot of people searched for another program like that later.
__: People were lucky, that's all.
DAN LICKLY: Very lucky.
FRED MARTIN: I'll just finish off by saying that when we left to go with this company in Cambridge, we still were very much tied into the space program and to our NASA friends, and people who we had worked with for the last five or six years.
A number of us were very interested in the software end of it. We thought that in the next space program -- which at that time they were thinking of a space station-- that there must be a better way to do software than we had done on Apollo, even though I think we did a pretty good job. We're not going to do the same thing with an assembly language, with a slow interpreter and so on. We're going to do something different.
So we got some contracts from NASA to study languages. The prevalent languages that were around those days were Fortran and an Air Force language called Jovial. We studied those languages quite a bit, and we came up with a new design for a language which borrowed a lot of the features of the Apollo programming concepts in real time: scheduling real time, monitoring real time tasks, and so on, and also all of the vector matrix arithmetic that was in the MAC language that was at MIT.
We created a new language, and we named that language after a computer scientist who was at Draper, Hal Laning. We called the language "HAL" and NASA adopted that language in 1975 for the shuttle. Today it is now almost 30 years later, it's still the language that the shuttle is using. They program all their on-board stuff in that language. They have tried many times to get away from it by going to Ada or something, C, and so on and so on, but they've got such an investment in the software and all the surrounding analysis and tools. So that language still lives on, and it has many many ideas that came directly from the Apollo experience.
It has many ideas that did not get into another language until the Ada language was adopted by the Defense Department many, many years later, when they looked at how to handle real time, and how they were going to make a safe language. I think I'll stop there.
site last updated 12-08-2002 by Alexander Brown