The core memory inside a Saturn V rocket's computer | Hacker News Reader

The core memory inside a Saturn V rocket's computer

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154 pointsmatt_d50 comments

My dad used to work as a customer engineer for IBM. When I was about seven years old he took me to work, and showed me the printing press and mainframe at the Washington Post. He opened up a cabinet and there was the core memory with its thousands of crisscrossing wires. Now when I look at a multi-gigabyte chip, I still occasionally think of the time I could see a little donut for every bit.

An often forgotten fact is that core memory is why a "core dump" is called that.

Core memory isn't wiped on loss of power, so you could read the contents out of a dead machine, to see the last state.

I used to program a KA-10 (one of the main primary research architectures of the ARPANET -- ask yourself why Berkley sockets work the way they do). Anyway it had core memory except for the machine registers which were semiconductors (DTL, not TTL). Those 16 machine registers were also the first 16 addresses in memory BTW.

Aaaanyway, the power in Cambridge would sometimes go out, and when it did whatever process was running would die, as all the register state (including PC which was a separate register) would be lost. But otherwise you could just restart since the core was fine. Of course if the monitor (i.e. kernel in today's parlance) was running, well you were sunk.

> ask yourself why Berkley sockets work the way they do

Interesting... Is it possible to shed some light on how Berkley sockets were influenced by that architecture?

"The contents of core memory are retained when the power is disconnected, so it's likely that the module still holds the software from when the computer was last used, even decades later."

A useful feature if the vehicle containing the module is involved in an accident and ends up on the ocean floor. A successful core dump would reveal the state of main memory at the instant power was lost.

That's what happened with the Space Shuttle Challenger; they were able to recover the computer from the ocean and read out the core memory.

It's amazing still to see that they could pull off all those successful missions with barely powerful enough computers and much less sophisticated material science. Look at today when we still struggle with designing and executing reliable rockets.

I believe the moon missions were the peak achievement of humanity to this point (not just the us, is that crazy?). I'm hopeful we'll survive self destruction to go past them eventually.

The risk posture of society in general was very different then. There are a lot of things that were commonly done that would be unthinkable today, most of which have nothing to do with space travel. Letting children play unsupervised, for example.

I look at it differently: I survey how much apparently useless and baroque infrastructure has been overplayed on top of core functionality and dismay. Those were essentially embedded systems running on bare metal; basically “parts of a machine”. Now our systems are far more intricate — but they seem to be far less efficient.

I use to program the F-15 central computer. One went down in Alaska. The computer was underwater for 2 weeks. Once retrieved, we washed the core memory boards in distilled water. We were able to determine the state of the jet when it lost power.

Did the F-15 use an IBM 4π computer or something else? What language did you use to program it. (I think aerospace computers are underappreciated, so I'm interested in whatever you can tell me about it.)

That information may be sensitive. The F-15 platform is still under active development, and even if it wasn't those details might be too much to ask.

Arguably, the fastest fighter jet computer in the world is in a U.S. Air Force F-15E. It’s the Advanced Display Core Processor II (ADCPII) and it’s capable of processing 87 billion instructions per second.

http://www.boeing.com/features/2016/08/f15e-fastest-computer...

Sounds like they've moved on from the IBM 4π.

Do F-15s not have flight data recorders? The NTSB is generally able to figure out the state of the jet for all airliners that went down by looking at the FDR.

Hardly any of the shuttles even had flight data recorders.

I could potentially see not wanting to have something like that in military hardware, especially if it falls into enemies hands.

Makes me wonder what happened to the old GT40 at the university that had the "Moonlander" game, which had a McDonalds on the moon, that was always loaded into its core memory.

https://en.wikipedia.org/wiki/DEC_GT40

>DEC GT40 running Lunar Lander

>MM11-L 8K word core memory (MM11-K 4K word core memory on GT40-Bx models)

https://en.wikipedia.org/wiki/Lunar_Lander_(video_game_genre...

>In 1973, DEC commissioned the creation of a real-time, graphical version of Lunar Lander, which was intended to showcase the capabilities of their new DEC GT40 graphics terminals. The game, which was written by Jack Burness and named Moonlander, was distributed with DEC computers and displayed at trade shows. An arcade game version of the game concept was released as Lunar Lander in 1979 by Atari, which featured a fuel-for-money system allowing the player to purchase more fuel to continue their current game.

https://www.arcade-history.com/?n=lunar-lander&page=detail&i...

>Lunar Lander was Atari's first vector game and was inspired by "Moonlander", a game written by Jack Burness in 1973 as a demo for the DEC GT40 vector graphics terminal (based on a PDP-11/05 CPU). This game used a light pen to control thrust and rotation.

>If the player landed at exactly the right spot, a McDonalds appeared. The astronaut would leave the lander and walk over to the McDonalds and order a Big Mac to go, before walking back to the Lander and taking off again. If players crashed directly into the McDonalds, the game displayed a message reading 'You clod. You've destroyed the only McDonald's on the Moon.' After a short run of Lunar Lander machines were manufactured, production was shifted over to "Asteroids" and the first few hundred "Asteroids" machines were housed in Lunar Lander cabinets. Atari donated a gold edition version of the coin-operated video game to the Discovery Center of Science & Technology in Syracuse, New York.

https://www.technologizer.com/2009/07/19/lunar-lander/

>Gameplay was simple, but challenging: The player wielded the GT40’s integrated light pen and carefully guided the lunar module’s descent by touching areas of the screen that controlled thrust. The player attempted to land via thrusting the lunar module’s rockets in real time while avoiding too fast an entry, or too steep an angle. With Burness’ innovations, the modern action-based Lunar Lander we all know today was born.

http://www.brouhaha.com/~eric/retrocomputing/dec/gt40/

http://moonlander.seb.ly/

Source code:

http://www.brouhaha.com/~eric/retrocomputing/dec/gt40/softwa...

I played Lunar Lander in the arcades, top draw game that.

As I read that, I was wondering if modern MEMS compasses are sensitive enough to read the magnetisation orientation of those ferrite cores? Could you non-destructively read the memory out of that one core at a time using cheap quadcopter components?

It would be cool to read the magnetic field of the cores directly. The first problem is you'd essentially destroy the core stack disassembling it to get at the planes and expose the cores. The second problem is the cores are sub-millimeter sized, so you'd need a fairly high resolution probe. I think a typical Hall effect sensor would be too big, and a magnetic-force microscopy probe would be too small. But if anyone knows of a probe that work work, please let me know.

Ahhh, right. I hadn't read the photo credits on those pics of the core planes. I see now that they are not the ones out of the assembled one you got to examine...

I hadn't worked out just how small everything was.

Thanks for the response!

My company still builds core memory for a military flight computer. It’s cheaper than re-qualifying a new computer.

I'd be interested in knowing what core memory computers are still in use, if it's not secret.

I started working at Burroughs in 77 as a field engineer. We still had one or two tube/core based computers out at customers sites. Just amazed me at the time when I got to see them. I never got to work on them, I started with the systems built with dtl chips. Memory was 1k x 1bit chips.

The good old days...

There is a great Linus Tech Tips and Smarter Every Day Youtube video about this. Highly recommended!

https://www.youtube.com/watch?v=olRF5Ckaga0

Ever since I learned Destin from Smarter Every Day works in defense I have lost interest in his channel. That was a disappointing discovery, though I did suspect it.

Why are you disappointed?

I suppose you think we should not defend ourselves?

The Department of Defense is 99.9% offense, 0.1% defense. You can use the argument that the best defense is a good offense, but that doesn't really excuse the number of (largely unprovoked) attacks on and occupation of other sovereign nations.

> and occupation of other sovereign nations.

Not that I disagree with the sentiment, but if you're (successfully) occupying a nation, it is by definition not sovereign anymore.

0.1% defense in terms of actions, but not in terms of capabilities. It's just that attacks on the US are very rare, because it's so capable of defense.

US military dominance is an ever present defense for nations around the world who would otherwise be harrassed or attacked by aggressive neighbors. US military involvement in the Middle East doesn't change that.

Of course you can argue we shouldn't be involved in the Middle East, and there are some reasons to think we shouldn't be, but we can agree on that point and still believe the US should have the world's dominant military.

The UK is being harassed by Ireland, the Faroe Islands, the Netherlands, Belgium, and France?

> but we can agree [that] the US should have the world's dominant military.

Who is "we"? It's not me.

What industry would you prefer he support? Every industry is corrupt, depending on who you ask...

While both are bad, there's a difference between "This abstractly might harm someone," and "I'm helping develop something that is absolutely going to kill someone and of which the intent is to kill someone."

I used to work in sub-contract electronic engineering and I told my bosses that I didn't want to do defence work. So I ended up building a bunch of equipment for coal mining and civil aviation. This has killed far more people than the defence work would have done.

Did these civil aviation devices helped anyone move more efficiently from place A to place B? I often move from place A and place B and happily accept all the risk involved. Absolved! Next!

Uber has killed more people than every American ICBM ever

Conflating "missile" with "ICBM" is a bad habit.

What type of missile does he work on?

ATEC handles basically everything under the sun.

I'm not that familiar with him, but he mentions a couple of types he's helped test for ATEC in this video:

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

https://en.wikipedia.org/wiki/FGM-148_Javelin

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

Judging by the video's contents, he's worked on more than just missiles.

I'm not trying to absolve Uber or something, for the record: the people who work for Uber aren't innocent, either. It just seems clear that they're a lesser evil. Malpractice versus malfeasance.

Consider that the US military, particularly the Navy, with its missiles, has facilitated safe global trade since the end of WWII. That in turn has lifted more people out of poverty than any previous single measure in human history. The US Navy has done more good than Uber could ever hope to achieve.

On the other side, consider for instance what Iran and Saudi Arabia would start doing to each other if the recently energy-independent US disengaged completely from the middle east. You can look at Syria in the wake of Trump's withdrawal for a tiny sample of the kind of violence that would occur in such a power vacuum.

Now none of that erases the various abuses and misadventures of the US military, but you're reducing a highly complex equation stretching over 70 years to a single simple variable: "Do the machines kill people or not?"

If every engineer in the US simply refused to build missiles as it appears you desire, the second, third and fourth order effects of that choice might kill even more people than if the missiles had just been built and potentially used. I'd argue it isn't clear at all whether Uber or the US defense industry is the lesser evil, and in fact there's a lot more history to take pride in in the defense industry.

That's a pretty random comparison. The Titan II missile killed 54 that I know of, while Uber killed 58 people in 2018, but I'm not sure what that tells us about core memory.

I just think that it's silly to boycott someone's videos about the a launch vehicle just because they work in missile testing. Especially when you consider the heritage of launch vehicles in general, and the Saturn V in particular

The Saturn V's F-1 engines were originally designed for the Air Force. Would you boycott a video about the Saturn V made by someone who actually worked on the thing, because they worked on a part of the Saturn V when it was still a military project? I feel like that is a ridiculous purity test.

The Titan series of ICBMs, with light modifications, was a workhorse for America's civilian space program. The Atlas, Delta, and Minotaur families of rockets were also originally ICBMS. AFAIK the only deaths from the Titan II were industrial accidents, which can happen just as easily for a civilian rocket program (although silo conditions did exacerbate the accidents). I don't think it's fair to say that someone who worked on testing the rocket contributed to those deaths— if anything, competent testing should reduce the number of accidents.

I won't go too much into the less wholesome background of the Saturn V, which had multiple former Nazis in leadership positions, all of whom had previously worked on rockets like the V-2. The head of the Saturn V program office even gave up his US citizenship in the 80s as part of a deal with the government to avoid prosecution for war crimes and abuse of prisoners during the Holocaust. I don't understand why someone would be willing to accept that, but not accept involvement from a random test engineer at Redstone Arsenal.

People don't ride around town on ICBMs every day.

https://www.youtube.com/watch?v=snTaSJk0n_Y

And planes still occasionally drop ICBMs that destroy people's houses.

https://www.independent.co.uk/news/world/americas/frozen-exc...

https://en.wikipedia.org/wiki/Blue_ice_(aviation)

Steve Wozniak likes to put stickers in airport bathrooms that say "DANGER: DO NOT FLUSH OVER CITIES".

https://twitter.com/stevewoz/status/912498392223252481

https://webfactory.mk/2018/05/28/do-not-flush-over-cities/

Destin was, until late 2018, a full-time Missile Flight Test Engineer at Redstone Arsenal. He is currently a PhD candidate at the University of Alabama Huntsville advised by Kavan Hazeli.

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

The source Wikipedia cites says he's still employed there:

https://mmee.uah.edu/people/destin-sandlin

Destin is studying Ph.D. in Mechanical Engineering at the University of Alabama in Huntsville. He has a B.S. in mechanical engineering from the University of Alabama and an M.S. in aerospace engineering from the University of Alabama in Huntsville. While an undergraduate, he was awarded the University of Alabama's Outstanding Senior Award. He is a full-time Missile Flight Test Engineer at Redstone Arsenal.

Upvoted you because I got turned off his channel by a similar but different issue last year: firearms.

He was doing a lot of episodes involving rifles, such as viewing the bullet's turbulence with polarization (iirc) and slo-mo. It was still scientific, but just a lot about guns. Then in the intro to one episode (sorry, I can't be bothered to go reference all of these), he said something like: people have criticized me because I talk a lot guns, but they're just so cool. In other words, "sorry not sorry." I closed the tab and never went back to his channel.

I'm in the US and I know guns are mainstream in the US, and he was actually good at studying them (not even really glorifying them). But there had been a lot of high profile shootings (Sandy Hook, Las Vegas, Florida, etc.), so it just seemed off. And frankly, I'm not into guns myself (just like I'm not into the foodie trend), so since he stated clearly he was going to focus on firearms, I just stopped following.

It's a youtube channel, and we all have limited time, so I see nothing wrong with stating a reason for giving up on it--even if it's a politically or culturally charged issue. It's not like the parent comment or I are criticizing the channel or even arguing he shouldn't do what he does.

They kinda are though.., or at least it's the most obvious implication. The entire comment is them saying they stopped watching after finding out he worked in the defense industry. Nothing to do with the content of the linked video, nothing to do with the original article. Just a statement that they think working in the defense industry is bad enough to stop watching the channel. If they aren't implying that we shouldn't watch SmarterEveryDay because of his career background, then they should have more clearly stated their point. As it stands the comment sounds like the classic "phrase a controversial point as an obvious implication so when people call you out on it you can backtrack and say they misinterpreted".

In the 80's I went to a college's "yard sale" and picked up a HP 9100B programmable calculator; they have core memory. When I plugged it in I remember it starting to run the program it had in it, not missing a beat. I still have it, maybe it's time to see if it still works.

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