# Forty years ago...



## mklotz (Jul 16, 2009)

Forty years ago today the Saturn V departed on our first trip to the moon.

It was an exciting and somewhat frightening day for me. I contributed to the design of the AGS (Abort Guidance System) in the LEM (Lunar Exploration Module). The AGS was designed to take over if the primary guidance and navigation system failed. Its most critical role was to get the astronauts off the moon and into a safe (higher than the lunar mountains) orbit until the command module orbiting the moon could descend and rescue Armstrong and Aldrin.

The AGS was an unproved system. It was the first strapdown guidance system to fly on a manned space vehicle. Lacking the delicate gimbals of the primary system, it was hoped that it would survive better if the lunar landing was "rough". The software and error mechanisms of a strapdown system are far different than those of a gimballed system. We desperately hoped that we had gotten everything right the first time.

Given the insane complexities of the mission profile, I frankly thought that those poor bastards were doomed for sure. If they did manage to land I was certain they'd never get themselves launched back into lunar orbit for the return trip. I fully expected them to need the AGS and one really doesn't want one's design verified in such a way that two men's lives depend on the outcome.

When they landed on the moon I, like everyone else, cheered wildly. But I was cheering because the LEM was still upright and the primary guidance was still working. During their ascent from the lunar surface my wife had to remind me to breathe.

It was a wild experience, although one I don't care to repeat.


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## Stan (Jul 16, 2009)

Very interesting story Marv. When you consider the state of electronics at that time, it is amazing that anything was successful.


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## cobra428 (Jul 16, 2009)

Marv,
I was holding my breath too (for the whole mission)!! I was only 16 at the time but I watched and listened continuously. I'm guessing you did some work on Long Island at Grumman then. I worked with a fellow engineer, some time ago and he said he had done some design on the LEM. Good stories!
Tony


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## putputman (Jul 16, 2009)

I remember that day also. I went out and bought a new color TV (nothing wrong with the old B/W) so we could watch the moon landing. We had friends over and made a party out of it. 

Come time to broadcast the landing, it was all in black & white. Boy did I get the razzing from everyone on that deal. :big: I guess I should have known there isn't a whole lot of color on the moon. ;D


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## Foozer (Jul 16, 2009)

Loved that moon shot, the shear power of that candle.

Have one of the old Estes models still in the box. Figure one of these days will put it together but then, like most of the rest, it'd be another tree ornament. Just too nice a model for that to happen too.


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## ChooChooMike (Jul 16, 2009)

I like pretty much everyone else at the time was absolutely glued to the TV for each Apollo missions and moon landing.

Standing under a Saturn V in FL (it's laying on its side) and next to the one standing tall in Huntsville, AL, you can see just how HUGE that rocket was !!

I'm still in awe of what the U.S. accomplished by landing on the moon ! That was state-of-the-art technology at the time. Compared to today's technology, it's considered very primitive. Heck even the space shuttle is 1970's technology.

Mike


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## mklotz (Jul 16, 2009)

Stan,

IIRC (it's been a long time) the computer had only a 4K memory. The programmers were scheduling miracles to free up even a single word. They would have given important parts of their anatomy for a modern day memory stick.

Tony,

Not Grumman. TRW (Redondo Beach, CA) had the contract to develop the AGS. It was the first project I worked on after joining the company.


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## steamer (Jul 16, 2009)

Hi Marv,

One of my Profs in college was the lead on the "Navigation Base" which I think was related to the gyro navigation module.If I remember correctly his last name was Shepard....one of my senior projects was with a team doing the same design exercise though in our case, no ones life was on the line....just our grade! In the quarter of a century since then, some of the details are fuzzy...but the requirements were just nuts...... high vibration levels through max Q, large swings in temperature and crazy tolerances and the use of beryllium ect.....

Thank you for your efforts! That was no small task!........

Dave


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## Maryak (Jul 16, 2009)

Good one Marv, :bow: :bow:

I remember it well, we had just returned from the UK and bought a 2nd hand TV to watch the moon mission. There was no colour TV in OZ until 1975.

It is also significant as it was the year HMAS Melbourne and USS Frank. E. Evans collided. Fresh from the college of knowledge in the UK I had the unenviable task of supervising the replacement of the damaged bow section of Melbourne. Like you Marv, it's not an experience I would like to repeat.

Best Regards
Bob


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## georgeseal (Jul 16, 2009)

If this old brain remembers correctly

I was on the USS Tidewater AD 31 in the Med


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## ozzie46 (Jul 16, 2009)

I have heard it said that your pocket calculator you have at home has more computing power than the computers on the moon mission. If that is so then you guys would have killed for my 2 year old laptop. :big: :big: :big: :big: :big: 

 Great job by the way. :bow: :bow: :bow: :bow:


  Ron


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## mklotz (Jul 16, 2009)

The disturbing thing to consider is that your pocket calculator probably has more computational power than the computers in the Minuteman ICBMs.


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## ChooChooMike (Jul 16, 2009)

mklotz  said:
			
		

> IIRC (it's been a long time) the computer had only a 4K memory. The programmers were scheduling miracles to free up even a single word. They would have given important parts of their anatomy for a modern day memory stick.



Ok, all you Apollo nuts .... try this site :

*Build Your Own Apollo 11 Landing Computer*

Summary from that link :



> I'm classifying this one under "Extreme Geek." But very cool Extreme Geek.
> 
> Remember the computer on the Apollo 11 Eagle lander that kept reporting "1201" and "1202" alarms as Neil Armstrong and Buzz Aldrin approached landing on the Moon? Well, now you can have one of your very own. Software engineer John Pultorak worked 4 years to build a replica of the Apollo Guidance Computer (AGC), just so he could have one. And then he wrote a complete manual and put it online so that anyone else with similar aspirations wouldn't have to go through the same painstaking research as he did. The manual is available free, but Pultorak says he spent about $3,000 for the hardware.
> 
> ...



*OK, Marv, stop drooling all over the keyboard .... *



> I have heard it said that your pocket calculator you have at home has more computing power than the computers on the moon mission.



The space shuttle, IIRC, is/was still using tapes to download individual programs into it's ancient computers cause they didn't have enough memory for more than 1 program at the time. Probably not that far removed from the Apollo computers. I believe they've been upgraded several times ??

Ironic seeing pictures of the shuttle with a laptop floating around the inside - that laptop has more computing power then all the system on the shuttle 

I'm sure some of us can actually remember when *core* memory was actually made up of tiny little iron/magnetic (ferrite) rings (cores) and wired together into a large 3-D block that made up the mainframe memory.

Mike


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## RobWilson (Jul 16, 2009)

Very interesting Link Mike , i have always been intrested in the technology of the Apollo Missions.
Cheers Rob


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## mklotz (Jul 16, 2009)

> I'm sure some of us can actually remember when core memory was actually made up of tiny little iron/magnetic (ferrite) rings (cores) and wired together into a large 3-D block that made up the mainframe memory.



Remember, hell, I wrote programs to be stored in those things. Two things can be said for core memory...

They beat the hell out of storing your data as pressure waves in mercury-filled delay lines (a technique used by Turing's Colossus - the computer that broke the WWII German codes). Turing would have eaten several more poisoned apples to get his hands on even 1K of core memory.

They'll withstand a nuclear EM pulse and keep on ticking - a nice feature when you're flying through the Armaggedon created by your brother missiles ahead of you in the attack sequence. Ditto if you're one of the second-wave missiles waiting in your silo for the retaliatory strike.


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## arnoldb (Jul 16, 2009)

Kudos to Marv and all the guys who worked on the Apollo project! - whatever your parts!

I had not even had my first birthday when Messrs Armstrong & Aldrin stepped on the moon!

I like reading books by Heinlein, Asimov and Clarke - not just because of the entertainment value in their writings, but because of the - how shall I put it - "enlightening and inspiring" value ?

I remember very fondly that one of the programs I put into my first computer (a TRS-80 Color Computer) was called "Orbit" - one could enter values for a couple of different variables to try and "orbit" a satellite around earth. To me, the most inspiring thing about that program was not the code, but trying to figure out how the code and calculations worked! - I also learned with that small computer how to optimise code for memory and CPU usage - which even today gives me an edge; I can not only code, but can try to use a computer to it's optimum capability.

So without talking more [email protected], - a SALUTE to everyone who was, and is, engaged in space exploration - no matter how small or large your part!!!

Regards, Arnold


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## Stan (Jul 16, 2009)

Marv: My memory is even worse than yours but I don't think the microprocessor had been invented in 1969. I was working with 7400 chips and marvelled when we got a 1k chip. All machine language programming to individual gates.


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## Tin Falcon (Jul 16, 2009)

Marv : Great hearing your first hand experience. 
I was but a young lad in primary school at that time yes on summer recess. Likely watched on an Olympic brand color tv. 
 I remember visiting the NAAFEC now the FAA Tech center while in High school and seeing a computer demo lunar lander where you had to enter a burn rate and burn time into the computer and safely land the LEM. I later remember putting the same program into my commodore 64 and playing it. Anyone remember the name of the program or where I could find that code. I know it must be a fairly simple program and likely public domain at this point. 
Tin


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## ksouers (Jul 16, 2009)

Marv,
Thanks for sharing such a great story. On occasion I get to talk to one of the old guys from McDonnell-Douglas and hear stories about how they worked on this and that part. The scary parts was hearing about how a couple cubic inches of this certain alloy "cost thousands of dollars and don't f-up the part cause these 6 pieces are the only stock that exists in the entire world." Probably more truth than exaggeration. And now the alloy is commonplace.

Tin,
I think the program was just called LANDER. At least it was in 1973 when I first started twiddling bits and bytes.


Kevin


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## rake60 (Jul 16, 2009)

Kudos for your efforts and involvement Marv! :bow:

I was only 8 years old at that time
but I remember every second of it!

I saw the full scale mock up of that Lunar Lander in the 
Smithsonian Air and Space museum in Washington D.C.
It was little more than foil and cellophane on an aluminum
tubing frame. I understand the capabilities of the on board 
computers of that time. 

Great story!

Rick


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## mklotz (Jul 17, 2009)

There's a Java version of LANDER here...

http://www.frontiernet.net/~imaging/lunar_lander_game.html


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## Paolo (Jul 17, 2009)

I remember that day also. Considering the entire entreprise was done using a Commodore pc capability..is incredible!!!
Cheers Paolo


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## Tin Falcon (Jul 18, 2009)

http://www.archive.org/details/flight_of_apollo_11
1969 28 minute documentary enjoy!!
Tin


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