How powerful was the Apollo 11 computer? (2009)

http://downloadsquad.switched.com/2009/07/20/how-powerful-was-the-apollo-11-computer/

by nantes • 13 years ago

78 51 13 years ago

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ctdonath• 13 years ago

tl;dr - The Apollo 11 computer ran at 0.001GHz with 0.000002GB memory and 0.000032GB of storage (read-only at that). The display amounted to a few dozen 1-bit pixels.

And it took them to the Moon.

sp332• 13 years ago

Now we seem to be completely dependent on computers, but at the time, I'm sure they didn't rely on them as much. The people pretty much navigated themselves to the moon

CapitalistCartr• 13 years ago

At a speaking engagement by James Lovell, I heard him describe the emergency procedure for navigating that they did with Apollo 13. There was a large round port window facing forward with a line engraved across the middle. Line that up with Earth's terminator line like cross hairs. Fire the main engine by hand. That's it. And it worked.

R_Edward4• 13 years ago

Some time ago, I was trying to buy a few hundred dollars worth of furniture, only to be informed that the cashier could not process my order because her computer was down. Everything I was buying had a price tag and I was paying cash, so I suggested that she find a pencil and some paper, and just write everything down, so she could enter it when the computer came back online. The concept apparently fried a circuit or two in her brain, because there was 6% sales tax on everything, and how was she supposed to know how much that would be? Plus, how was she supposed to know how much change to give me?

Nowadays, we don't have price tags on anything anymore. Prices are fetched from a database using the UPC as a key, so if the computer's down, the buyer is out of luck. At a previous employer, we sold specialty goods to contractors, so we had strong relationships with our customers. I drafted a plan to print up pads of paper sale forms that looked more or less like our (80x24 greenscreen) order screens, so if we lost connection to the mainframe, we could still move product from the warehouse to the customers; we'd just give them the product and bill 'em later. It was a risky move, but not really any riskier than sending our customers across the street to our competitors. To my knowledge, they've never had to use the manual system, thankfully.

We may not be "completely dependent on computers" just yet, but we seem to be getting there.

kalleboo2• 13 years ago

I thought it was mostly rocket science? (calculating trajectories in advance, on supercomputers on the ground)

smackfu• 13 years ago

Well, the other real alternative was to determine their position, etc., then send that data back to NASA who would use their big computers to do the calculations, then send back the burn duration, etc.

rst• 13 years ago

Actually, the lunar descents were all on autopilot until fairly close to the surface. And even when the astronauts took "manual" control, the LEM was still fly-by-wire, like a lot of modern aircraft: the guidance computer was reading the movements of the joysticks and translating that into thruster settings. (Pulling the joysticks "hard over" would bypass the computers, but that was considered an emergency measure only.)

The LEM software was supposed to be capable of a fully automatic landing, but none of the astronauts rode it all the way down.

David Mindell's book "Digital Apollo" goes into these systems, and their development, in much detail; the discussion of the LEM user interface is in chapter 8.

kalmi10• 13 years ago

I love reading this: http://www.hq.nasa.gov/alsj/a11/a11.landing.html

"This display does not place a particularly heavy load on the computer, but when added to the existing load, was sufficient to generate the 1202 alarm."

---

"102:38:26 Armstrong: (With the slightest touch of urgency) Program Alarm.

102:38:28 Duke: It's looking good to us. Over.

102:38:30 Armstrong: (To Houston) It's a 1202.

102:38:32 Aldrin: 1202. (Pause)"

http://www.dailykos.com/story/2012/08/25/1124164/-Neil-Armst...

---

"102:36:18 Armstrong: (To Houston) Our position checks down range show us to be a little long.

102:36:21 Duke: Roger. Copy. (Heavy Static)

[In a post-mission analysis, Apollo Descent and Ascent Trajectories, Floyd Bennett notes that, at PDI, Eagle was about 3 miles farther downrange than planned, due to [..]"

... after that, Armstrong selected a landing site visually, and landed the lunar module manually. :)

[Mission Control] Thirty seconds. (Just Mission Control telling Neil Armstrong how many seconds of fuel he has left for landing) :)

minikites• 13 years ago

If you like this, there's Spacelog, which is a neat way to view transcripts for a number of missions:

http://apollo11.spacelog.org/

http://apollo13.spacelog.org/

Browsing through the Apollo 13 "spacelog", it's interesting how a lot of the lines in the Apollo 13 movie are very similar to the ones in real life.

sigkill• 13 years ago

It's pretty awesome to know that you can get something that powerful inside your palm (the Atmega 328) for less than $3 single unit prices.

After some minor conversion, the Atmega/Arduino has almost exactly same storage space and RAM. Only, the Arduino clocks at 16MHz. Still, awesome regardless.

solistice• 13 years ago

That was the Block II version though. The previous version (at 24k Storage and 1k memory) is proably closer to the ATtiny1634, which only has 16k of main storage but clocks at a veritable 20Mhz. The thing I find amazing is that there's a bga version of that chip that is 2x2mm. And they're like <2$ single unit. Sorry for whipping out my 1634 pet peeve.

hvs• 13 years ago

For those interested in this subject, I highly recommend "The Apollo Guidance Computer: Architecture and Operation":

http://www.amazon.com/The-Apollo-Guidance-Computer-Architect...

John Pultorak built a Block I AGC (think "version 1") and provides all of his work in the Public Domain here:

http://klabs.org/history/build_agc/

dbarlett• 13 years ago

I haven't read that one, but enjoyed Digital Apollo: Human and Machine in Spaceflight http://web.mit.edu/digitalapollo/

microDude• 13 years ago

I think looking back at computer clock rates and memory is a silly endeavor. I remember a few months ago people commenting about "why we put a 2Mpx camera on the Curiosity Rover". The simple fact is, mission critical hardware/software is a different ball-game. You need reliability and fault tolerance.

If I was going to the moon today and had the choice of flight computers. Hands down, I would choose the Apollo 11 AGC over an iPhone A6 processor based system.

mikeash2• 13 years ago

Ironically, the Apollo 11 landing was nearly scrubbed because the computer got overloaded with tasks and couldn't process everything in time, so that lack of power really was a problem.

PavlovsCat2• 13 years ago

The computer got overloaded because of crew error.

forgotAgain• 13 years ago

How powerful was Shakespeare's word processor?

drivers99• 13 years ago

Minor nit-pick: The PC came out in 1981 but the XT came out in 1983. But they both have 8088 chips running at 4.77 MHz. The main difference was that you could get it with a 10 MB hard drive, but my PC (not XT) had upgraded ROM BIOS chips (you had to change the actual chips because they were not flashable) from around 1984 and so it has a 20 MB Seagate hard drive. (Which still works.) The XT also drops the cassette port.

I recently got ahold of my PC from storage again and when I opened it up I was surprised that the floppy drive uses up one of the five 8-bit ISA slots, even though it has very few simple chips. (The XT has 8 slots.)

(Pic of the floppy controller. http://upload.wikimedia.org/wikipedia/commons/a/a6/IBM_PC_Or... )

Florin_Andrei2• 13 years ago

Well, I started coding on an 8 bit machine, 3.5 ~~GHz~~ MHz, up to total 64 kB of memory (static and dynamic together) - but keyword here is "up to", initially it was less than that. I had all the "OS" pretty clearly mapped out in my head, by address no less. My programs did contain sometimes jumps to physical addresses.

So I think I've some idea how the AGC operated.

kalleboo2• 13 years ago

MHz I hope :)

Florin_Andrei2• 13 years ago

Darn. Yes, MHz. :) Thanks!

Kaibeezy• 13 years ago

followed the links to the guy who built an AGC from scratch - http://klabs.org/history/build_agc/ - detailed technical info plus photos - amazing!

filmgirlcw• 13 years ago

I still love this story -- even four years later! (and not just because my husband is the author!)

noir_lord2• 13 years ago

As someone who spends his time writing in High Level languages (though I have done lower level stuff in the distant past) these kinds of embedded computers hold a real fascination for me.

On my long term list of things to-do is get back into electronics and learn Ada (mostly because it's a million miles away from PHP).

bitwize• 13 years ago

Learning Ada is worth your while, embedded or no. Hint: If you have a problem and you find yourself reaching for C++, consider Ada instead. It's probably powerful enough for the task, safer, and more readable (therefore maintainable).

Try implementing Unix utilities (cat, ls, echo) in it for a weekend of fun. :)

noir_lord2• 13 years ago

My one true love programming language is Pascal (mainly because when I was exposed to it I'd only every used BASIC) and later Object Pascal.

Looking at Ada I see a lot of similarities, it looks like "home" to me.

mikestew• 13 years ago

Though multitasking and VMs on the AGC were a feat, that's not what amazes me. The IBM 360 demonstrated that both were possible at the time, and the AGC impressively did it on less hardware. What does amaze me is how long it took such things to come to the personal computer, and arguably how much DOS/early Windows held things back. Unix, with its multitasking, ran on PCs and Macs in the 80s, so we only waited 20 years after the 360 (and 15 after the AGC) for multitasking. But usable VMs didn't come (or at least weren't commonplace) until, what, mid-90s? 30 years after the 360, and 25 after the minimal AGC? What the heck took so long?

zerohp• 13 years ago

Few personal computers had protected memory until the late 1980s. Unix didn't run on PC or Mac until protected memory hardware was available.

Emulation was always popular, and it is a type of virtualization. Few people wanted to emulate the same platform they already had. Pure software emulators were pretty slow in the 1980's, unless the target platform had the same cpu as the host.

My family had an Amiga and we had both a bridge board and an A-Max. The bridge board was a full PC on an expansion card, so its not really a VM. The A-Max was more like a VM. Its hardware contained the Apple ROMs and a floppy disk interface because the Amiga floppy drive could not read Mac disks. The software used the ROMs and Apple floppy drive to emulate a Mac.

Now that I think about it, I think the real reason was ram and to a lesser degree hard drive space. My first encounter with virtualization in Linux happened when most people were running between 8 and 64mb of ram. 64mb of ram was very expensive. That's a pretty big constraint.

batbomb• 13 years ago

Far Travelers is an awesome book about satellites that you can read for free. Much more information than you'd care to know about, it's amazing.

"Another significant improvement included the addition of extra "brain power" to allow the orbiters to perform more complex functions. Viking orbiters possessed two 4096-word, general-purpose computers that could operate in parallel or tandem modes. These replaced the small special purpose computers contained in Mariners 8 and 9. The capability for more rapid picture taking allowed for better site surveys and special regional studies. This capability was augmented by tape recorder systems that could store 2.112 megabits per second, with a capacity of 55 TV pictures-over half a billion bits of information."

http://history.nasa.gov/SP-480/ch12.htm

http://history.nasa.gov/SP-480/contents.htm

hcarvalhoalves• 13 years ago

The AGC is quite a feat, but already from the digital age. I find the TDC's used during the WWII more fascinating. I wonder how the space age would look like with electromechanical computers :)

http://en.wikipedia.org/wiki/Torpedo_Data_Computer

gpsarakis• 13 years ago

The details on the software and the in-flight patching in the Apollo 14 mission are quite amazing. Another point to make is that nowadays we have tremendous amount of computing power combined with comprehensive numerical analysis tools on the planet which allows engineers to perform thorough simulations for the stages of space/air/sea travel and the behavior of vehicles.

smoyer• 13 years ago

"(1/1000th of 1 MHz, much as 1 MHz is 1/1000 of 1 GHz)"

Half of 1 MHz is 500 KHz not 500 Hz ... it may sound slow but the PIC uCs we were using in the '90s were clocked at 20 MHz maximum and executed about 4 MIPS. For the 1960s, that computer really was rocket science!

Theodores• 13 years ago

The comparison with an early PC is not imaginative.

Think of the original Sinclair ZX81 with 1K of RAM and 8K ROM. Swap out the Z80 for a 6502 to get approximately the same register count. Without a screen to worry about (it took up too much RAM + CPU time) and you could do a lot, e.g. 1K chess or, as the adverts said, run a nucular power station with it. You could also service I/O with hardware interrupts.

joshlegs• 13 years ago

isnt all the code open source now? seems i read that it was not long ago

How powerful was the Apollo 11 computer? (2009)

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