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

Slashdotted

[dreamer8815]

In three two one... Huston, we have a problem.

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.

Re:Slashdotted

[Mr. Bad Example]

> Huston, we have a problem.

Not the least of which is that he's dead.

The coolest project I've ever seen

[incog8723]

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

Warning

[poofyhairguy82]

From site: For Win32 users, it's much more work to get your computer set up to build Virtual AGC than it is in Linux, and the steps needed will be less familiar.

That made me feel good seeing as how this is the first week I've tried linux.

very simple processor

[ndevice]

Took a quick scan at the architecture of the machine, and I'm suprised that it's so simple.

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.

Add to that: RTL (before TTL) and magnetic core memory bring up the nostalgic value.

Re:very simple processor

[thhamm]

some of the "moon hoaxers" think thats why they could never get to the moon at all.
"though much faster, my pentium can barely run [insert 3d shooter here] at good FPS. how could it fly to the moon? so they never did."

logic?
clavius explanations.

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:very simple processor

[Edward Teach]

In the Apollo 11 descent to the moon, you hear someone say "twelve oh one alarm." This was the alarm that told the LM crew that the computer reset because it ran our of memory.

Re:very simple processor

[Anonymous Coward]

No, it didn't 'run out' of memory, there was no OS capable of making that determination. There were simply too many real-time interrupts coming in. The time-slice approach of the Apollo system simply couldn't handle all those requests.

Re:very simple processor

[TheHawke]

Eh, Brute force. They needed the AGC to be as simple, yet programmable with all the steps necessary to get the boys on the moon and back.
So they took the PDP8 and squeezed it down into the size of a early 80's era Kaypro portable (now that's saying something about my age) and managed to get it to draw as much power as your coffeemaker.
THEORETICALLY, they could have done it with a sextant and a good clock, BUT! Their navigation skills had to be dead-bang on every time to the fraction of a minute.
So it was easier to shoehorn this colossus into the spacecraft and let it do the driving.

Re:very simple processor

[oogoliegoogolie]

...the computer reset because it ran our of memory.

That's because when the LM was being designed some engineer decided "640 Bytes should be enough for anyone."

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.

Re:very simple processor

[Kenshin]

Wow. The last thing you want on the descent to the moon is a BSOD...

Re:very simple processor

[Teancum]

During the final few seconds, yes it was manual. But with Apollo 11 they had about 5 seconds of reserve fuel left when they actually set down. That was not 5 seconds to abort and go back up, but simply 5 seconds before they ran out of fuel.

While indeed there was actual piloting and people were clearly in the loop to run the spacecraft (and needed!), some of the critical timing issues for orbit insertion and lanuch windows simply have to be run with computers. There is no other way to ensure that you can hit the buttons at the precise time and stop in time.

While analog computers could have been used in this situation, this was the time period (late 1960's) when digital computers were finally widespread enough to be used in applications like this. The AGC was one of the first computers to use integrated circuits (IC's), and even then it was primarily 7400 series chips and a couple of specialized circuits. NASA at the time contracted something like 50%-70% of all IC production, which is where some people seem to think NASA was behind the development of some of the early micros.

BTW, this thread referenced the fact that sailors in the 16th through 19th Centuries used pretty much just a compass, clock, map, and sextant. The poster forgot to mention the clock, but it was indespensible back then...to give longitude data. Clocks still are very important even now, as that is all a GPS satellite really transmits anyway (the current time). All the rest of the positioning info is derived from the clock data.

Anyway, the sextant is actually a fairly sophisticated analog computer that is able to correctly identify your current lattitude with amazing precision. It tended to make the navigator go blind with one eye, which is why you see skippers and naval officers in depictions of the era wearing an eye patch. They litterally looked at the sun too long through the sextant. A good navigator using a sextant could get lattitude down to +/- 1/2 to 1/10th of a degree. Longitude you were usually considered very fortunate if you got it down to +/- 10 degrees (almost 600 miles when near the equator), which is why maps of the 18th Century are very accurate on lattitude but miserable with longitude, causing things like Minnesota's Northwest Angle.

Re:very simple processor

[shadowbearer]

IIRC correctly during the Apollo 11 landing they actually passed the "no-abort" point at about 60 seconds of fuel, when they were simply too low for a successful ascent stage abort.

OI isn't really that critical timewise unless you have to hit *precisely* the orbit you want; a few seconds either way (and there often was during the lunar missions even with the computer running things) meant merely that your orbit would have a few miles or tens of miles discrepancy in perigee/apogee, correctable with a short burn.

The Saturn rockets were pretty reliable wrt to launch windows, but as I recall with the Atlas and Redstone they often couldn't predict exactly how long the rocket would fire sometimes not even to tens of seconds; but they still achieved the trajectories they wanted. So it couldn't have been *that* critical.

De-orbiting to splashdown, now, that's a different matter, a few seconds difference in retrofire and you could under or overshoot your splashdown target by tens of miles. :) But then that's because after the retros were jettisoned they had little maneuverability, which wasn't true with LM deorbit.

Given that the Polynesians didn't have clocks (or sextants) they did most of their navigating using dead reckoning and knowledge of their local environment; which shows just how much they understood the local winds and their ability to move their rafts. ( * see below)

Without a clock determining longitude accurately was extremely difficult. One could approximate the time using star set/rise times and seasonal charts, but with the distortion near the horizon causing enormous errors in the actual location of the star, and especially given the inaccuracy of the charts at the time, this was pretty much a crap shoot.

Sextants are certainly incredible! While in college I had the opportunity to learn to use a modern one (with a sun filter) and on my first few tries I located the longitude of the observatory at SCSU to within 14 minutes of arc; not especially astounding by modern standards (see the link below), but astonishing given the basic simplicity of the device and my inexperience.

I didn't know that about the MN NW Angle, do you have a ref? Fascinating!

* There is a good piece available about the Polynesians and modern navigation here

Cheers,
SB

Re:very simple processor

[Erbo]

Right...1201 was "Executive overflow - no vacant areas." The computer was simply unable to complete all its jobs in the course of a major cycle.

Gene Kranz's book Failure Is Not An Option talks about simulating the moon landing, and seeing 1201 alarms coming up and the controllers unable to deal with them. Kranz ordered an abort after a 1201 alarm...but it turned out that was the wrong thing to do. Dick Koos, the simulation supervisor, told him, "This was not an abort. You should have continued the landing. The 1201 computer alarm said the computer was operating to an internal priority. If the guidance was working, the control jets were firing, and the crew displays updating, all the mission-critical tasks were getting done." They wound up figuring out rules on which program alarms would terminate descent...and the list did not include the 1201 or 1202 (similar) alarms.

Good thing, too, because both of those alarms occurred on Apollo 11's descent. Buzz Aldrin reported that it seemed to happen when they had a computer display of time, range-to-go, and altitude up. They continued the landing, which was eventually successful; the alarms didn't seem to affect the LM computer performance any.

Ahh, it's the Missing Piece!

[Anonymous Bullard]

Now the Chinese Communist Party can finally be confident that their Soviet-era space capsule can be launched at the moon, with one or two "People's Liberation" Army's faithful inside.

Like Deng Xiao Ping's 50-year plan towards (real) World Domination by using the capitalists' greed against their own long-term interests, this space-conquering plan began over 50 years ago when the "People's Liberation" Army invaded their peaceful neighbour Tibet, to be used as a back-up landing area. Well, Tibet can also be looted for their natural resources (oil, gas, uranium) and subjugation the hapless Tibetan people has been used as a great propaganda victory for Party jingoism, but clearly one of the main reasons to invade was to use the Tibetan territory as a back-up landing site.

Apollo On Board Emulator, running on Red Flag Linux and locally-built Dragon CPU... even Evil Invading Dictatorships can be pretty geeky when it suits their World Domination Plans... ;-)

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:12-bit Instruction set

[kfg]

A quick inspection of an Apollo capsule reveals why they didn't just use a PDP8.

Think of three fat guys trying to move one of those things in a Mini Cooper.

KFG

Re:12-bit Instruction set

[hughk]

Not really, and it had an excellent reputation for real-time work. The thing is when NASA were shopping for processors a long time before the landing, the PDP-8 didn't exist in the compact form. By the time of the first landing it certainly did, but it was already too late. The PDP-8 and later the PDP-11 then just swept through the world of real-time computing.

Re:12-bit Instruction set

[melonman]

Also, it takes a long time to get electronic components approved for use in space, which is why the stuff in satellites is usually way behind what sits on your average desk. The university I attended designed and launched a series of very cheap satellites, which, apparently, ran some of the most advanced computing equipment in orbit, simply because it didn't matter too much if it blew up after 3 days.

Re:12-bit Instruction set

[AndroidCat]

And they made Buzz Aldrin sit in the back. No wonder he gets cranky if someone says that he didn't go to the Moon!

Simulation - emulation environment

[Anonymous Coward]

What I would like to see is a complete Apollo computing system simulator, consisting of the hardware simulator, where you could realistically simulate the effects of increased core voltage, heat, power surges, fluctuations, etc. coupled with the hardware emulator capable of running native Apollo code, just like vAGC.

Do they have this at NASA? For them it must be easier and more reliable to just use an identical environment for testing purposes, but some Apollo enthusiasts would enjoy tinkering with such a combined simulation-emulation environment (SEE).

Re:Simulation - emulation environment

[thhamm]

then integrate the whole thing into Orbiter.
this would be incredible. not just simulating the whole spacecraft in such detail, but actually doing the whole flight.

i wasnt my fault. i they tell me to stir the tanks, i stir the tanks.

How do they get to the moon...

[Purifier]

...without having a "Start" button? ;)

Re:How do they get to the moon...

[bytesmythe]

They just used LaunchPad... ;)

Slingshot

[Hypharse]

I tried to use this to run games. It didn't work at first, there just wasn't enough power. Then I used the gravitational pull of my neighbor's house as a slingshot and was running Doom 3 in no time.

I wonder......

[bhaynes]

......how long it will take someone to try and load it up with pr0n. "Huston, we have a REALLY BIG problem......"

Re:I wonder......

[Anonymous Coward]

Bah. Apollo computers only has a numneric display. The hottest pr0n that it can display is number "69" in all fields.

Game anyone?

[NewtonsLaw]

Does someone have a copy of that old favourite: "Lunar Lander" which runs on this emulator? :-)

Hell, even my Texas Instruments card-programmable calculator played that game!

Orbiter

[0123456]

"then integrate the whole thing into Orbiter."

Already being worked on:

http://mysite.wanadoo-members.co.uk/marui/orbite r_ agc.jpg

Re:Orbiter

[0123456]

Hmm, for some reason that link got screwed up: here's another try.

Re:Orbiter

[0123456]

Currently the programs run, but the IMU hardware simulation isn't there, so it can't control the spacecraft...

Source is here.

Space Shuttle computers

[Veteran]

An engineer I work with at JSC has an actual - legally obtained Space Shuttle flight computer. The government declared it surplus, and he bought it from the surplus section, so he has the paperwork documenting that he is the legal owner. His box is an actual flight unit, which was in space, not a ground test unit or engineering sample. He has the paperwork documenting its complete history.

Every once in a while you can find some incredible things in government surplus.

Re:Space Shuttle computers

[Veteran]

I believe he has powered it up, and it does work.

Linux

[schweini]

Darn. another platform to port linux to! Just when we thought we had most architectures covered :-)

But seriously: would it, theoretically (!), be possible to write a x86 emulator on something like that?

Re:Linux

[AndroidCat]

If you can write a Turing Machine on it, you're there. Just give it a long enough R/W tape, and let'er rip! (I will warn you that your FPS frame rate will suck.)

Re:Duh...

[AndroidCat]

If it gets infected with Gator/Claria, it'll probably take them somewhere that sells printer ink and toner.

Not comparable in any way to calculators

[panurge]

This machine is optimised for the acquisition of fairly real-time data; read the architectural description. Multiple channel counters are implemented in hardware, partly because in the days of discrete logic this was relatively easy to do (and, of course, the tube calculators with which people had gained experience used lots of counters, because it is relatively easy to make a counter tube, while binary tube logic is very hardware inefficient.)

Calculators have absolutely minimal I/O and need hardly any interrupt handling capability, and general purpose CPUs like the PDP-8 require a great deal of external hardware to give efficient programmed I/O. It was only really with integrated electronics that general purpose CPUs became appropriate for real time instrumentation and control.
It's also important that in a space environment, every added gate is a hazard because it can get flipped by radiation. The ideal is to have the minimum gate count, minimum memory cell count, and the shortest possible path between phyical I/O and computing. The computers used in the Apollo meet this requirement.

Sorry to restate what may be obvious to some people, but a lot of people here will never have had to implement a rad-hard design, and will not understand why simplicity and directness are such virtues in design for space use.

Next step: hardware

[H_Fisher]

How long before somebody cobbles together a "system" this will run on - a re-creation of the hardware using today's components, or at least a neat-looking case for this emulator?

I'm sure somebody out there with more time than I have is working on it ... :)

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

[peawee03]

Not posting this as troll, flamebait, or anything other than a matter of engineering: could you do better?

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:Disaster waiting to happen

[Beryllium Sphere(tm)]

Maybe a capacitive measurement? Liquid oxygen must have a different dielectic constant from gaseous oxygen.

Why look at the apollo flight computer

[stinky wizzleteats]

When you fly it?

The most recent version of the apollo spacecraft add-on (NASSP 5) has a partial working AGC built into the navigation system.

Re:Why look at the apollo flight computer

[Queuetue]

Actually, it uses *this* AGC.

Car-PC

[LakeSolon]

Does anyone else have a sudden urge to run this on the touch-screen of their car-pc? I can't wait...

~Lake

Re:Car-PC

[Dr. GeneMachine]

Just be sure to have a lot of space in your trunk for all the punched tapes containing the data for your navigation system....

Re:very simple processor 1201

[Tuna_Shooter]

Also, I beleive that they left the rendevous docking radar switch in the on position during decent (a no no) also contributed to the 1201's. Even though it was listed in the Flight manual as being in the on postion. A mistake i believe that wasnt tested in the simulators but was found by 2 engineers during a passing conversation in a hall.

Anyone get a good look at the code yet?

[today]

Humorous snippet from the landing module code...

P63SPOT3 CA BIT6 # IS THE LR ANTENNA IN POSITION 1 YET
EXTEND
RAND CHAN33
EXTEND
BZF P63SPOT4 # BRANCH IF ANTENNA ALREADY IN POSITION 1

CAF CODE500 # ASTRONAUT: PLEASE CRANK THE
TC BANKCALL # SILLY THING AROUND
CADR GOPERF1
TCF GOTOP00H # TERMINATE
TCF P63SPOT3 # PROCEED SEE IF HE'S LYING

P63SPOT4 TC BANKCALL # ENTER INITIALIZE LANDING RADAR
CADR SETPOS1

TC POSTJUMP # OFF TO SEE THE WIZARD ...
CADR BURNBABY

Re:Anyone get a good look at the code yet?

[Quatloo]

And its nice to see octal again too!

Interesting time limit

[Chemisor]

> Note it only keeps mission time so after 24 hours you have reset the time

Yeah. 24 hours ought to be enough for everybody.

nope Re:Disaster waiting to happen

[WolfWithoutAClause]

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.

They didn't use artificial gravity to seperate the LOX; quite the opposite.

In fact, in zero gravity LOX tends to divide up into regions of gas and liquid. If the gas happens to float past the sensor, then they get an incorrect reading of the density, and hence they don't know how much is in there. This was a big problem on previous flights. Stirring the tank mixes it all up and makes it the same density; allowing a reliable reading to be taken.

you have several pounds of highly combustible aluminum and graphite parts

Aluminum, particularly bulk aluminum is *not* combustible in LOX. It's used on the Space Shuttle main tank fer heavens sake!

Graphite can't really burn either; for it to burn it needs to reach ~3000K, and the LOX is pretty keen on it not reaching that temperature.

LOX only really explodes in contact with greases- it's soluble in them, and they form a contact explosive.

and you have a DC motor with brushes sparking up a storm

Provided the brushes are carefully chosen, this need not be a problem.

That's not actually what caused the explosion anyway.

During testing a relay welded itself shut due to incorrect voltages. In flight, the wiring overheated- and the insulation burnt in the LOX. That caused the LOX tank to overpressure, and it blew away half the side of the vehicle.

Re:nope Re:Disaster waiting to happen

[Veteran]

They didn't use artificial gravity to seperate the LOX; quite the opposite.

In fact, in zero gravity LOX tends to divide up into regions of gas and liquid. If the gas happens to float past the sensor, then they get an incorrect reading of the density, and hence they don't know how much is in there. This was a big problem on previous flights. Stirring the tank mixes it all up and makes it the same density; allowing a reliable reading to be taken.

Yes and no. In zero g the bubbles and liquid have no reason to separate. In a gravity field the bubbles float just like the do in water - so you get a liquid without voids in it - which you can measure.

Aluminum, particularly bulk aluminum is *not* combustible in LOX. It's used on the Space Shuttle main tank fer heavens sake!

Aluminum will burn in air if there is enough energy to break through the surface layer of aluminum oxide which builds up on the surface. In fact aluminum is so reactive with oxygen that this layer forms instantly when the metal is exposed to oxygen. Anything which will burn in air will really burn in LOX.

Graphite can't really burn either; for it to burn it needs to reach ~3000K, and the LOX is pretty keen on it not reaching that temperature.

There was an experiment where a scientist used LOX and charcoal to see how fast it would burn - it esentially flashed in less than a second. DO NOT ATTEMPT THIS. IT IS RIDICULOUSLY DANGEROUS. Your statement is like saying Nitro Glycerin is safe to have in your house. NOTE FOR THE YOUNG AND INEXPERIENCED: DO NOT STORE NITRO GLYCERIN IN YOUR HOUSE. IT WILL BLOW UP AND KILL YOU!!!

Provided the brushes are carefully chosen, this need not be a problem.

This is exactly the sort of thinking which resulted in the original disaster. Brushes are mechanical devices - there is inductance in a motor - when the brush connection is broken the inductance of the motor will cause a spark. We have studied the ignition properties of such sparks in LOX in my group. There is a statistical probability of a given spark igniting the brush material.

That's not actually what caused the explosion anyway.

During testing a relay welded itself shut due to incorrect voltages. In flight, the wiring overheated- and the insulation burnt in the LOX. That caused the LOX tank to overpressure, and it blew away half the side of the vehicle

That is the official theory which was reached by people who knew nothing about the spark ignition problem. The voltage in the GFE power supply used in the test was not enough to weld contacts - the LOX would have cooled the wires so that they wouldn't have reached ignition temperature. The explosion didn't happen until the tank was stirred. The thinking behind reaching that official theory was "Well none of the other tanks blew up so the design was OK so it must have been someing which was done to that particular tank that caused the problem."

Thanks for demonstrating the "Whirr click, whirr click " mind set to everyone.

Re:nope Re:Disaster waiting to happen

[thompson42]

In flight, the wiring overheated

No, the wiring overheated on the ground, as the test conductors ran the internal tank heater for hours to boil off the LOX inside. The tank contents did not empty as quickly as usual because the tank fill pipe had been dislodged when the tank was dropped two inches during installation some months before. Because the tank heater was built for 28V and the older ground test equipment delivered 65V, the heater thermostat failed, and the tank heater stayed on 100% of the time instead of cycling on and off. The intense heat that built up in the well-insulated tank damaged the wiring in the tank.

the LOX would have cooled the wires so that they wouldn't have reached ignition temperature

Ignition occurred when the wires with damaged insulation came into contact with each other and arced. The arc was hot enough to induce combustion in the wire insulation.

Re:nope Re:Disaster waiting to happen

[the pickle]

There was an experiment where a scientist used LOX and charcoal to see how fast it would burn - it esentially flashed in less than a second.

Experiment? More like "let's see how fast we can light a barbecue grill!" ;)

p

Re:nope Re:Disaster waiting to happen

[Veteran]

No argument there! Of course this would not have been news to the tank designers either.
It may have been. There is currently a discussion between various groups at NASA on this very subject - is there some minimum value of spark energy which is safe in a pure oxygen athmosphere? We say no, others say there is.

This entire thread is highly instructive of how memory and the human brain work in the real world: When I read the original reports about a year and a half ago I knew and understood the cause of the actual accident - but I remembered the dangerous design of the tank better than I did the pedestrian causes of the actual incident. Why? as a design engineer the design problems were of more interest to me. Over time I forgot the actual cause of the incident and substituted what I did remember about it.

Learn from this error lest it happens to you at some point.As you get older this happens more since you have much more information stored as an older person than you do as a young person. This makes you slower to respond (it takes longer to search through more stuff), and the chances of 'bit errors' increase with the number of bits stored.

Nevertheless my original point can be modified to: "it was a poor design decision to have live electrical circuits inside of a LOX tank".
I think most of us can agree with that.

Parent is informative, deserves upmod

[Beryllium Sphere(tm)]

In addition, the incorrect voltages during testing were the result of failed communication between the contractor and NASA, a spectacular example of why the paperwork is important.

Beowulf comment ...

[Alain Williams]

If we have a Beowulf cluster of these, do we have a space invasion on our hands ?

If so: who is invading who ?

Draper Labs built the AGC

[dswartz]

I would just like to point out that Draper Labs in Cambridge, MA (the company I work for) built the AGC. An exact replica of the real AGC sits in our Simulation Lab.

Intuitive

[suwain_2]

Some people complain that the Linux CLI is too user-unfriendly. Have they tried using this thing?

Setting the time:
Press Verb 2 5 Noun 3 6 Entr. Then enter a + to indicate you're entering the time in decimal, not octal. Be sure to enter all 5 digits of the hour. Then press Entr, and enter minutes, and then repeat for seconds. And make sure you remember that the seconds are in 100ths.

V25N36E+00012E+00002E+04400E

Totally intuitive.

Notes on compiling

[crucini]

I didn't immediately succeed with the author's instructions. Here's what worked for me:

cd yaAGC
./configure
make
sudo make install
cd yaDSKY
./configure
make
sudo make install
yaAGC --core=Validation.bin --debug
In another window, still in the yaDSKY directory: yadsky --cfg=src/LM.ini
(Note lowercase yadsky)
Congratulations, Ronald. Pretty cool. Does the contrast on the LED display have to be so low? The background is very light.

Am I the only one here who actually tried the program?

Re:Curious about the computers back on the ground

[hughk]

NASA was using IBM360s in those days. They really had little processing power in real terms (although they were quite good on I/O).

I have no idea what the Prius has as a processor, but a modern laptop would substantially exceed the processing power of the ground installation. Perhaps only if programmed in FORTRAN though (the NASA language of choice at the time).