Apollo On Board Computer Emulator

frankk74 writes "For those of you interested in Historical Computing and the Apollo manned spaceflights Ron Burkey has created a open source emulation of the Apollo Guidance Computer called vAGC. I use it as my desktop clock of choice. Note it only keeps mission time so after 24 hours you have reset the time :-). P.S. Another cool Apollo toy free and payware can be found here."

Comments

The coolest project I've ever seen

[incog8723]

Forget Linux. Forget overclocking/unconventional CPU cooling. This is cool shit.

12-bit Instruction set

[Anne Thwacks]

A quick inspection of the instruction set reveals why they only made 157 of these and made 6 million PDP8s.

Re:12-bit Instruction set

[Rosco P. Coltrane]

A quick inspection also shows that a PDP8 weighs as much as the Saturn V rocket, and weight is the last thing they needed to haul stuff on the moon...

Re:very simple processor

[RedWizzard]

People say over and over again that simple handheld calculators are more powerful than that thing, and it seems that the oft-parroted line is more accurate than they realize.

Or perhaps they repeat it because it's accurate and they know it?

Re:Slashdotted

[Metteyya]

I have a lot of respect for all the admins and webmasters for not banning their sites/servers from people-coming-thx-to-slashdot.

Disaster waiting to happen

[Veteran]

I had occasion to look at the plans for the oxygen tank that blew up on Apollo 13. There is no great mystery why it blew up, the mystery is why they didn't all blow up.

Trying to figure out how much is left in a liquid oxygen tank in outer space is not an easy task. If you wanted to know that answer here on earth you would weigh the tank - which obviously won't work in free fall.

The idea they came up with was to have a sensor in the tank that could measure the level by resistive means. In order to have a 'level' to measure they had to create an artificial gravity inside the tank by swirling the contents with an internal electric motor and a blade. In the movie "Apollo 13" one of the astronauts talks about "stirring the O2 tank", that is what he is talking about.

Consider what this all means: you have a tank full of liquid Oxygen, you have several pounds of highly combustible aluminum and graphite parts which are soaked in liquid Oxygen, and you have a DC motor with brushes sparking up a storm inside the tank. Another name for such a combination is a "bomb".

NASA's - management driven - engineering has long been full of "Whir click, whir click - OK, Russian Roulette is flight certified as safe" thinking. Nobody does a "how could this all go wrong" analysis.

Re:Disaster waiting to happen

[Anonymous Coward]

That is really amazing. I'll look it up, of course, but it sounds about right. I would have used some ultrasonic transducers or beta probes or something to sense the level... Who knows what state those where in in the 60s but I know they used the beta probe approach to sense fuel level in airplanes back then.

Re:Disaster waiting to happen

[Veteran]

i would have suggested an external motor with magnetic coupling to an internal stirring blade - similar to what is done in chemistry labs.

Measuring how long the stirrer takes to come up to speed tells you the mass of what you are accelerating.

Re:Disaster waiting to happen

[wideBlueSkies]

Just thinking about this...could we not tell the mass of the liquid in a tank by shaking it slightly? The time/energy it takes to get the tank moving, combined with the momentum after turning off the shaker could probably determine how much stuff is in there.

Or another alternative...sonar...sound reflected off the contents of the tank.

wbs.

Re:very simple processor

[Speare]

But somehow a few rafts colonized the polynesian islands. Somehow a compass, a sextant and a bunch of canvas guided boats across the Atlantic for centuries.

Re:very simple processor

[Archibald Buttle]

The hoaxers are dicks.

It is of course completely irrelevant that their pentium is a heap of crap, as you imply. These are the kind of idiots that don't believe that you could have a 3d game on a 20 year old 8bit micro - showing them Elite blows their minds.

They think that because a computer is slow it's worthless. Well, that's what Microsoft and Intel keep telling us so it must be true. Also their 3d shooter is damn slow. That's gotta be proof.

Conversely those of us with brains, real software development knowledge, and an appreciation of physics realise that you hardly need any computing power at all for an Apollo space craft. Indeed it's arguable that the computer they did have was overkill - a computer-less solution could have been engineered.

Re:very simple processor

[Daniel Dvorkin]

Look at just about any operation your computer performs. Not only is it all math, it's generally fairly simple math. You could do it all with a pencil and paper -- but you can't do it as fast. It's speed that's the issue. On a ship, you have time to correct your errors. When landing on the Moon ... you don't.