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Comment by chmaynard | Hacker News Reader

"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.

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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.

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.

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!

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.

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.

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