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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 24th Feb 2023, 3:47 pm   #1
Roger Ramjet
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Default 1st Apollo Flight Computer

A retired TV engineer pal of mine is fascinated by 1st moon landing and states that although the flight computer was very basic, the memory parts were woven into the fabric of the capsule.

Is this true ?

Rog

Last edited by Roger Ramjet; 24th Feb 2023 at 3:53 pm. Reason: change word
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Old 24th Feb 2023, 3:53 pm   #2
paulsherwin
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Default Re: 1st Apollo Flight Computer

https://en.wikipedia.org/wiki/Core_rope_memory

https://en.wikipedia.org/wiki/Apollo_Guidance_Computer
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Old 24th Feb 2023, 4:05 pm   #3
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Default Re: 1st Apollo Flight Computer

There was a series called Moon Machines (6 part ISTR).

Well worth a watch if it reappears

One dealt with the Nav Computer.

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Old 24th Feb 2023, 4:34 pm   #4
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Default Re: 1st Apollo Flight Computer

There is a whole series of fascinating YouTube videos by 'CuriousMarc', beginning with
https://www.youtube.com/watch?v=2KSahAoOLdU&t=15s
on getting an Apollo Guidance Computer restored and operating. He has also done a whole series on the S-band Comms System.

Well worth watching.

andy
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Old 24th Feb 2023, 5:28 pm   #5
Bazz4CQJ
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Default Re: 1st Apollo Flight Computer

Quote:
Originally Posted by Roger Ramjet View Post
A retired TV engineer pal of mine is fascinated by 1st moon landing and states that although the flight computer was very basic, the memory parts were woven into the fabric of the capsule.
Is this true ?
Rog
It was woven; I recall a description of the involvement of a group of mainly elderly ladies, who had spent a lifetime working for some weaving company, before changing from garments (or similar) to memory. Think it went in to a metal box rather than being the "fabric of the capsule".

B
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Old 24th Feb 2023, 5:32 pm   #6
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Default Re: 1st Apollo Flight Computer

Light Years Ahead.

https://www.youtube.com/watch?v=B1J2RMorJXM

Computer for Apollo.
https://www.youtube.com/watch?v=YIBhPsyYCiM
https://www.youtube.com/watch?v=ndvmFlg1WmE

John.
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Old 24th Feb 2023, 6:19 pm   #7
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Default Re: 1st Apollo Flight Computer

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Originally Posted by tinkers3 View Post
From what I've read, this explanation of the alarms is a bit off the mark.

The computer had to take in data from the landing radar and/or the rendezvous radar and it was controlling the rocket engines and also steering the hi-gain dish antenna. There was a 5-way mode control switch to set up various combinations for various parts of the mission and it has been generally agreed that the switch was in the wrong position during the descent (how could that happen - there's speculation). Also, the inputs from the radars had been synchronised for frequency and amplitude but phase had been over-looked (i.e. design omission) and made the computer do more work. But there is also the issue that the position of the Apollo spacecraft during its first orbit around the moon had been determined with a significant error, which meant that right from the start of descent, the spacecraft was further along the ground track than calculated.

The recognition of the ground technician Steve Bales as the one man who said "continue" misses out the fact the Bales himself said he depended on input from colleagues.

I think that even today, some of the many aspects which contributed to the problem are the subject of some "uncertainty" (see Flight Director Gene Kranz's autobiography). The thing that's striking, is that just a few months later, the Apollo12 mission made a pin-point landing with no input from the crew, as was the case with the following missions. For Apollo12 onwards, an improved method of determining the spacecraft position (prior to descent) was used.

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Old 24th Feb 2023, 7:05 pm   #8
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Default Re: 1st Apollo Flight Computer

The computer was allocated too many tasks and simply ran out of resources. It handled this emergency correctly, generating an alarm and discarding low priority tasks. Good design and programming by Raytheon.
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Old 24th Feb 2023, 7:21 pm   #9
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Default Re: 1st Apollo Flight Computer

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The computer was allocated too many tasks and simply ran out of resources. It handled this emergency correctly, generating an alarm and discarding low priority tasks. Good design and programming by Raytheon.
Yes, but the key questions are why it became overloaded and what would have happened if Armstrong had not intervened (with tremendous skill)? Even forgetting the alarms, the computer was descending in to a field full of large boulders (it was 4 miles past the intended landing point, due the orbit calculation error, but did know that; garbage in, garbage out). Armstrong had to stop descending and fly more or less horizontally for some distance, far more than ever practiced in a simulation. By the time he found a good spot to land (controlled by eye and hand) they were very nearly out of propellant and the computer was just a passenger at that point.

As the Capcom said, "You got a bunch of guys about to turn blue".

B
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Old 24th Feb 2023, 7:36 pm   #10
60 oldjohn
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Default Re: 1st Apollo Flight Computer

One of this forum members was involved in the development of the Apollo computers. IIRC He was "Wirefull" John? from the SW of England, I have not heard from him for many years and fear the worst. I can not find any trace of Him in the members list so presume has been deleted.

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Old 24th Feb 2023, 7:41 pm   #11
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Default Re: 1st Apollo Flight Computer

No member is ever deleted from the forum unless they specifically request it. Members who haven't visited in a long time are given the status 'Retired' unless the mods receive different info.
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Old 24th Feb 2023, 7:45 pm   #12
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Default Re: 1st Apollo Flight Computer

Wireful3 maybe the member your thinking of John?

Cheers

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Old 24th Feb 2023, 8:44 pm   #13
60 oldjohn
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Wireful3 maybe thd member your thinking of John?

Cheers

Mike T

Hi Mike, I think you are right, but looking through the members list of "W", all seven pages I can not see him listed.

John.
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Old 24th Feb 2023, 9:14 pm   #14
Dave Moll
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Default Re: 1st Apollo Flight Computer

Indeed. It goes straight from Winston 1 to the first Wireless John. I assume this means that Wireful3 has been marked as no longer active (and thus only visible to moderators).
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Old 24th Feb 2023, 9:33 pm   #15
60 oldjohn
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Default Re: 1st Apollo Flight Computer

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Originally Posted by 60 oldjohn View Post
Quote:
Originally Posted by Cobaltblue View Post
Wireful3 maybe thd member your thinking of John?

Cheers

Mike T

Hi Mike, I think you are right, but looking through the members list of "W", all seven pages I can not see him listed.

John.
Thank you Mike, BTW You PM box is full.

Cheers, John.
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Old 24th Feb 2023, 10:47 pm   #16
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Default Re: 1st Apollo Flight Computer

They don't write software like this anymore:

https://news.mit.edu/2016/scene-at-m...ollo-code-0817

Nor do they have Little Old Ladies knitting the binary.

(It was familiarly known as LOL memory).

https://righto.com/agc.pdf

There's a couple of videos of the Ladies "knitting" the core rope available on youtube IIRC.

The cross assembler "YUL" ran on a Honeywell 1800 computer.

Quote:
Originally Posted by Ken Shirriff
I tried to build an emulator for the Honeywell 1800 mainframe so I could run the original Yul assembler.

But I gave up; this computer is very strange.

Among other things, it has two program counters and they can run forwards or backward. It's like spaghetti code squared.
This from a chap who analyses the insides of processor chips for fun. ROTF.

Everytime I attempt to get my head around a machine with program counters that run forwards & backward I laugh. It's the only way to stay sane.

Last edited by DrStrangelove; 24th Feb 2023 at 11:03 pm.
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Old 24th Feb 2023, 11:29 pm   #17
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Default Re: 1st Apollo Flight Computer

I went to the Washington Air & Space museum a few years ago & had a very good guided tour.

One of the highlights was the Apollo 11 capsule, where the guide mentioned the computer problems that were encountered & how Neil Armstrong coped with them. Luckily formerly being a test pilot helped him with dealing with temperamental equipment.

Armstrong had to improvise to deal with a broken power breaker, using a pen barrel to push the contacts together.
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Old 25th Feb 2023, 3:14 am   #18
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Default Re: 1st Apollo Flight Computer

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Originally Posted by Richard_FM View Post
I went to the Washington Air & Space museum a few years ago & had a very good guided tour. One of the highlights was the Apollo 11 capsule, where the guide mentioned the computer problems that were encountered & how Neil Armstrong coped with them. Luckily formerly being a test pilot helped him with dealing with temperamental equipment.
And of course, the Apollo 10 capsule is in the Science Museum in London.

Armstrong was very lucky to escape from an accident when a lunar module simulator ("The Flying Bedspread") he was flying crashed; it was probably less than 100ft above the ground when he ejected and came down on a 'chute. The simulator hit the ground and burned fiercely. About 1min in https://www.youtube.com/watch?v=tUJDbj9Vp5w

B
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Old 25th Feb 2023, 3:30 pm   #19
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Default Re: 1st Apollo Flight Computer

Quote:
Originally Posted by Bazz4CQJ View Post
Quote:
Originally Posted by Richard_FM View Post
I went to the Washington Air & Space museum a few years ago & had a very good guided tour. One of the highlights was the Apollo 11 capsule, where the guide mentioned the computer problems that were encountered & how Neil Armstrong coped with them. Luckily formerly being a test pilot helped him with dealing with temperamental equipment.
And of course, the Apollo 10 capsule is in the Science Museum in London.

Armstrong was very lucky to escape from an accident when a lunar module simulator ("The Flying Bedspread") he was flying crashed; it was probably less than 100ft above the ground when he ejected and came down on a 'chute. The simulator hit the ground and burned fiercely. About 1min in https://www.youtube.com/watch?v=tUJDbj9Vp5w

B
I remember seeing a clip of that accident in a documentary on the Space Race.
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