I was actually going to do a post on my personal blog about Thomas Edison, who died on October 18, 1931, but as my AD/HD mind whirled and jigged I latched onto another favorite inventor, Robbert Goddard, for whom tomorrow is significant:
He became interested in space when he read H.G. Wells's science fiction classic The War of the Worlds when he was 16 years old. His dedication to pursuing rocketry became fixed on October 19, 1899. While climbing a cherry tree to cut off dead limbs, he imagined, as he later wrote, "how wonderful it would be to make some device which had even the possibility of ascending to Mars, and how it would look on a small scale, if sent up from the meadow at my feet." For the rest of his life he observed October 19 as "Anniversary Day", a private commemoration of the day of his greatest inspiration.
Of course the Father of Rocketry laid the foundation for all subsequent space exploration, including Project Apollo. The computer-assisted Apollo 11 landing:
04 06 38 26 CDR (EAGLE) - PROGRAM ALARM.
04 06 38 28 CC - It's looking good to us. Over.
04 06 38 30 CDR (EAGLE) - It's a 1202.
04 06 38 32 LMP (EAGLE) - 1202.
04 06 38 48 CDR (EAGLE) - Give us a reading on the 1202 PROGRAM ALARM.
04 06 38 53 CC - Roger. We got - We're GO on that alarm
...
04 06 42 22 LMP (EAGLE) - 1201
04 06 42 24 CDR (EAGLE) - 1201.
04 06 42 25 CC - Roger. 1201 alarm. We're GO. Same type. We're GO.
...
04 06 45 40 LMP (EAGLE) - CONTACT LIGHT.
04 06 45 43 LMP (EAGLE) - Okay. ENGINE STOP.
04 06 45 45 LMP (EAGLE) - ACA - out of DETENT.
04 06 45 46 CDR (EAGLE) - Out of DETENT.
04 06 45 47 LMP (EAGLE) - MODE CONTROL - both AUTO. DESCENT ENGINE COMMAND OVERRIDE - OFF. ENGINE ARM - OFF.
04 06 45 52 LMP (EAGLE) - 413 is in.
04 06 45 57 CC - We copy you down, Eagle.
04 06 45 59 CDR (TRANQ) - Houston, Tranquility Base here.
04 06 46 04 CDR (TRANQ) - THE EAGLE HAS LANDED.
Ever have one of those days or weeks when computers just don't seem to work the way they should? Okay, yeah, dumb question. Anyhoo, stuff this week has made me wax nostalgiac for simpler days.
On Tuesday I couldn't log into the computers in either of my classrooms, nor could I get into the College's web portal from my laptop. Fortunately one of my students is a help desk dude and was able to reset my password for the portal in the AM, then the school's domain in the PM (poor bastard has me twice in one day).
[ed note: I've since gotten the problem at least temporarily resolved, and confirmed that we do in fact have a single-signon system based on the Windows domain. I thought that was the case, but it appeared that the help desk had to go into two different systems to "unlock" me and the intermittent problems seemed unrelated, so I thought maybe I just didn't understand how things worked on the backend.]
Yet today when I tried to get into the portal and to my online class website, I was locked out again. At least I'm not trying to do anything mission-critical or dangerous like, say...landing on the moon, so failure is an option and I can afford to wait until tomorrow to get things resolved and my lecture MP3s posted.
Similarly when the lady ringing up my prescription at the pharmacy today said, "oh, I might have to do this manually," it wouldn't have been a huge deal to sign for my meds with ink on paper instead of with the fancy electronic pen on their terminal. That's what people had to do starting yesterday, but by the time I came in things apparently were fixed.
Since I'm a space geek as well as a computer geek, all this brought to mind Apollo and the computer glitches on Eagle back in 1969. I've always been astonished that NASA was able to send 3 human beings a quarter million miles away with a computer less sophisticated than a Timex Sinclair:
Here's a challenge...
Develop a system that can control a 13,000 kg spaceship, orbiting at 3,500 kilometres per hour around the moon, land it safely within metres of a specified location and guide it back from the surface to rendezvous with a command ship in lunar orbit. The system has to work the first time, and minimise fuel consumption because the spacecraft only contains enough fuel for one landing attempt.
Do this with a computer that has barely 5,000 primitive integrated circuits, weighs 30 kg and costs over $150,000. In order to store your software, the computer doesn't have a disk drive, only 74 kilobytes of memory that has been literally hard-wired, and all of 4 Kb of something that is sort of like RAM.
Sounds daunting?
That's the task that faced Peter Adler and Don Eyles of the MIT Instrumentation Lab who were responsible for developing the software for the Apollo Lunar Module. Their system worked, but almost caused the first moon landing to be aborted in the final minutes before the touchdown.The Apollo mission was conceived at the height of the Cold War. Planners were concerned that the Soviet Union might try to jam any navigational information sent from the ground, so the on-board computers had to be capable of having autonomous command of the spacecraft.
...
The computers that formed the basis of the Apollo Guidance and Navigation System (AGS) were at the bleeding edge of technology in the 1960s. They were the first to use the integrated circuit technology that subsequently gave us desktop computers and so many of the consumer electronic products that fill our lives today.
...
The fixed memory contained the programs, constants and landmark coordinates using 36,864 terms or words, each of 15 bits length. That came to a grand total of 74 kilobytes of memory. The erasable memory, which was used to store variable data used in calculations or as registers for logic operations, had only 2,048 15-bit terms.
The fixed memory was made from coincident-current ferrite cores woven into a rope with copper wires and sealed in plastic. Software components were encoded into a core according to the 'pattern' of its weave. Each core functioned as a small transformer, with up to 64 wires connected to each core. If a wire passed through a particular core, a '1' would be read. If a particular wire bypassed the core, a '0' would be read. If you wanted to change the software contained in fixed memory, you had to rewire the sealed core to change the bits. The erasable memory was made from similar materials but with a different design. Each core in the erasable memory could be changed using magnets. Turning clockwise to indicate a '1' or anti-clockwise indicating a '0'.
In order to use the computer, astronauts used a display and keyboard unit (DSKY, pronounced "disky"), which weighed another ten kilos. This wasn't a QWERTY keyboard, but a number pad along with some special buttons. In order to input a command or action, the user had to press a button marked "Verb", followed by a number that corresponded to the action. To input data, the user pressed the "Noun" button along with a number. Even though it sounds complicated, the interface was elegant and it worked.
The computers were programmed thus:
Allan [Klumpp], his friend Don Eyles, and about 300 others wrote their programs in the first high-order computer language, called MAC (MIT Algebraic Compiler), then compiled it BY HAND into assembly language, which they typed onto punched cards (there were no terminals or text editors). Incidentally, the Shuttle's software is written in a language called HAL/S, named after Hal Lanning, the author of MAC. HAL/S is an improved version of MAC.
Don Eyles was also responsible for a clever workaround during the Apollo 14 landing:
The abort switch on the instrument panel was sending a spurious signal that could have spoiled Alan Shepard and Ed Mitchell's landing. I had written the code that monitored this discrete. The workaround simply changed a few registers, first to fool the abort monitor into thinking that an abort was already in progress, and then to clean up afterward so that the landing could continue unaffected. The procedure radioed up and flawlessly executed by the astronauts involved 61 DSKY keystrokes.
I'm amazed it worked at all. Then again, the systems were simpler and probably more reliable than any Microsoft crap we have today. Hmm...maybe they don't want to upgrade to the glass cockpit and 787 computer system in Project Constellation's LSAM for our next planned lunar foray...
ntodd
I love the space program - it's the most American of all American things. I miss it.
Posted by: WalterNeff | December 29, 2007 at 12:33 AM