The Apollo 11 Guidance Computer
Posted by
CmdrTaco
on Mon Feb 05, 2001 11:37 AM
from the i-bet-it-gets-lost-in-boston dept.
from the i-bet-it-gets-lost-in-boston dept.
wiredog writes "Dr. Dobbs has an article on the Apollo Guidance Computer with a jpg of a source code listing.
Some specs:
70-lb box ,
Approximately 20 instructions,
16 bit word,
ROM (rope core) 36K words; RAM (core) 2K words,
Basic machine cycle: 2.048 MHz"
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The Apollo 11 Guidance Computer
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If you're ever in Bozeman, MT... (Score:3)
Apollo Guidance Computer Manual (Score:5)
Re:Use of GOTO?!? (Score:3)
Scarcasim Alert! (Score:3)
Re:But it worked (Score:3)
I believe that was 64 seconds of fuel, with 60 seconds being needed to orient the descent module and fire the ascent module engine for a successful abort. The real question is whether Armstrong would have eaten into that 60 seconds to land. On the records he has always said no...
sPh
massively parallel human computers (Score:3)
article about a British meterologist who conducted
the first finite-difference weather prediction
calculation in the 1920s using a room full of
people with adding machines. The motive for this
was there were a few very dense measurements
of weather data during the Great War,
and Prof. Richardson wanted to see if it was predictable.
Richard Feymann in "Surely you aren't joking"
mentions a human calculation room for a-bomb
modeling at Los Alamos in the 1940s.
Women are better in space (Score:3)
The average woman astronaut, at 100 pounds, is 2/3 the weight of the average male astronaut at 150 pounds. With present day launch costs of 10,000 USD per pound, replacing a 6 person male shuttle crew with 6 females results in a cost savings of $3,000,000 dollars, or 300 extra pounds of equipment and payload. Factor in the reduced fod, water and oxygen requirements, and you might be able to loft 500 extra pounds into orbit.
Woman live longer than men, and are healthier in general. When you are talking about expeditions lasting 3+ years (ala Mars), you want the healthiest people you can going.
When you are talking about being locked in the space the size of 2 cubibles with 5 other people for 3+ years, you want low aggression, non-territorial people there, to avoid infighting and chaos. While Europe is making admirable strides towards breeding a complacent, passive population, for now, the best. most compatible crew would be woman.
However, due to the stranglehold that the caucasian patricarchy has on the space program, don't expect this to be acknowledged, or to even see more than a token amount of women in space. Pity the Israelis don't have a space program, they don't have the resources for false pride and propping up insecure males, the would go for the gusto and have woman like Golda Meir in orbit.
Thanks,
Mirror (Score:3)
http://www.perljam.net/misc/apollo11-code.jpg [perljam.net]
A noble era which passed us long ago. (Score:3)
I can remember years back writing some assembly code on an Apple II; I had a routine that ended up being two bytes too long to fit between Page 3 and the keyboard buffer. In order to make it fit, I ended up resorting to self-modifying code that saved three bytes. Now, you might make the argument that self-modifying code is horrible style (and you'd be right), but at the time, that didn't matter to me; what mattered was that I'd come up with a solution that worked given the limitations I was stuck with. Coming up with something like that gives a person a far greater sense of accomplishment than does a solution that was attained simply by artificially throwing more resources at the problem.
This type of mindset is for the most part dead. Oh, there are examples of it around in certain specialized arenas (for example, the current crop of Playstation 1 games has pretty much pushed that platform to its limitations.) But Moore's Law and dropping RAM prices have mandated that general software development should be quick and dirty rather than compact and elegant. And maybe, from a financial standpoint, that's how it should be; after all, it takes considerably more development time and effort (and therefore more money) to write the slickest code than it does to write acceptable code that works, given enough resources. However, that doesn't mean that we should not be able to lament the passing of the earlier era.
Finally, I should point out that I am not saying that current software developers are entirely devoid of creativity, because they're not. There are a lot of developers for a lot of different hardware platforms and operating systems that are doing some pretty cool things. I am claiming, however, that software development is rapidly becoming a field of endeavor that requires far less cleverness and wherewithall than it once did. Whether this is good or bad depends on your point of view, but I don't see how it can contribute to any increase in general software quality.
Re:But it worked (Score:3)
Actually, it didwork. Armstrong left the docking radar on when the procedure said to shut it off. This consumed processing cycles which meant that not all the events could be processed in the time allotted, which meant that some very critical calculations weren't getting done. The problem wasn't in the computer, it was in the astronauts not following procedure. The program was basically a big loop which had to be executed every 'n' milliseconds, and the engineers knew how many cycles they had to burn during those 'n' milliseconds, and designed and tested the procedures and programs accordingly. Once the astronauts deviated from the procedures, they were in unknown territory.
Re:Complexity Kills (Score:3)
They are not laptops. The laptops are only for austronauts personal use and sometimes for control of non-critical experiments
The guydance and control computers are actually almost as simple as apollo 11. They were either 804(X=8,9)or 805(X=0,1). These were the highest ones certified for NASA use at the time the shuttle was designed. There is an overall of 5 of these extremely simple systems operating commands to the valves and the engine ignition system on a voting principle. The majority gets to execute the command. The idea is that there cannot be a simultaneous triple failure. This is actually described in detail in one of the articles on the shuttle ran by Scientific American in the eighties.
Use of GOTO?!? (Score:5)
Who do these guys think they are? Every 1st year CS student knows that GOTO is considered harmful. [acm.org]
Let's do ourselves all a favor and never go to the moon again using a GOTO statement!
By comparison... (Score:4)
They are usually based on 8032 family processors, and are clocked at a stunning 12MHz.
Of course, I'm speaking for the Bosch Jetronic family, newer ones are more powerful (but not by much).
But it worked (Score:5)
Considering that today people seem to want to throw the latest technologies at every tiny little problem they encounter the fact that the Apollo 11 worked is a testament to the fact that more is not always better, and that complexity brings its own problems.
Unfortunately, it seems as though people have gotten used to the idea that they require the latest technology, the latest "innovations" in order to be successful and cool. Hence the market for shoddy products that are rushed out quickly to customers, who can be guaranteed to solve their problems by getting the next release because it's newer and therefore superior.
Whereas this machine, so simple compared to even the simplest of embedded processors today, did what it was supposed to, and did it well. Today, we see all kinds of computer problems due to technology being thrown at projects as a miracle cure without considering what is actually required! Just look at the Navy's debacle with NT for a prime example.
Well done /. We need more stories to remind us that more technology isn't always good. Remember, 90% of everything is crap, and technology is no exception.
Complexity Kills (Score:5)
Now we have astronauts taking laptops into space and using MS software for email and networking while on board. The testing cycles for all this software is long because all faults have to be eliminated, but the simple fact remains that computer and software designs are becoming so complex that in the very near future, if not already, they are too complex for use in the space program.
Hunting down a bug in a 100000 lines of code is one thing. Hunting down a bug and all the other bugs it causes in 4 million lines? NASA has already faced this problem, because they use Win 95 laptops. How about 10 million lines. How about 20 M?
What about the computer processors that run the space shuttles. Frankly, they're all old technology, because upgrading to the newer stuff is just too damned dangerous. If the video processor that powers your HUD guidance systems crashes because of an obscure hardware bug that occurs only in freefall, you're screwed.
Personally, I think that this sort of complexity is going to become the limiting factor in the advancement of technology. A point will come in the very near future when systems, be they processors or OS's, become so complex that the testing time necessary for critical use makes rapid development unprofitable.
Re:But it worked (Score:3)
The DSKY Rules! (Score:5)
To the astronauts, the DSKY was the GNC; the GNC really was just a box stowed in the Lower Equipment Bay.
The interface was so good, it was subsequently used on the F-8 fighter prototype. For more on the DSKY, see:
http://www.dfrc.nasa.gov/gallery/photo/F-8DFBW/HTM L/EC96-43408-1.html
To see it in action, watch the "From the Earth to the Moon" series from HBO. Most local video stores have 'em. The Apollo 12 one was my favorite for seeing the DSKY in action, when Al Sheppard helped upload new code (IN FLIGHT) to ignore a flakey ABORT button.
Best to ya,
Quantum Hack
http://www.hamhud.net
Re:Midgets are better in space (Score:4)
Send Mini-Me to Mars!
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Not practical. (Score:3)
For this reason, it is my belief that gay men are far better suited for long term space exploration,
Are you kidding? The Madonna CDs alone would make the launch weight prohibitive!