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from the to-the-moon-and-beyond-(maybe) dept.
A deep dive into the Apollo Guidance Computer, and the hack that saved Apollo 14:
In the eight months since the harrowing flight of Apollo 13, engineers made several changes to the spacecraft to reduce the chance of another explosion happening. To help ensure that the crew could make it home if another emergency occurred, an additional oxygen tank and battery were added. The unplanned pause also allowed time for some software updates to be added to the lunar module computer; a particularly welcome addition was the ability of the computer to recognize changes in the height of the surface during the approach to the landing site. With this new capability, the computer would not be confused by the undulating terrain as the vehicle headed toward landing.
[...] A very serious problem cropped up almost immediately after TLI, as Kitty Hawk attempted to dock with the mission's lunar module, Antares. Fingernail-sized latches on the docking probe used to connect the command module to the lunar module failed to catch, and the two spacecraft were unable to dock. Only after repeated attempts was Kitty Hawk able to capture and securely attach Antares. Afterwards, the S-IVB was sent on its way to a lonely but spectacular death and the combined Apollo 14 spacecraft continued the voyage to Fra Mauro.
[...] However, less than four hours before the scheduled landing, controllers noticed that according to the indications on their consoles in Mission Control, the LM's Abort pushbutton appeared to have been pressed. When asked via radio, Shepard confirmed that no one on board Antares had pressed the Abort button—which meant there was a short-circuit or other electrical issue somewhere inside the LM's complicated guts.
This was potentially a mission-ending problem: if the button was pressed and the engine was firing, the LM would immediately begin its abort procedure as soon as the lunar descent started, making a landing impossible.
Under hard time pressure, the ground had to quickly figure out what was wrong and devise a workaround. What they came up with was the most brilliant computer hack of the entire Apollo program, and possibly in the entire history of electronic computing.
To explain exactly what the hack was, how it functioned, and the issues facing the developers during its creation, we need to dig deep into how the Apollo Guidance Computer worked. Hold onto your hats, Ars readers—we're going in.
(Score: 1) by fustakrakich on Monday February 03 2020, @11:58PM (13 children)
Full of ads and trackers and java!
I'll wait for someone to post the spoiler, please?
La politica e i criminali sono la stessa cosa..
(Score: 2) by JoeMerchant on Tuesday February 04 2020, @12:55AM
Spoiler alert: they had a literal army of ground crew poring over a tiny tiny piece of code that was basically assembler, and ground simulators to run it on, of course they found something clever.
🌻🌻 [google.com]
(Score: 3, Funny) by barbara hudson on Tuesday February 04 2020, @12:57AM (7 children)
SoylentNews is social media. Says so right in the slogan. Soylentnews is people, not tech.
(Score: 2, Interesting) by fustakrakich on Tuesday February 04 2020, @02:37AM (6 children)
I use Netscape, for 25 years. In all that time nothing better has shown up
And look up the word "facetious"
La politica e i criminali sono la stessa cosa..
(Score: 2) by barbara hudson on Tuesday February 04 2020, @04:06AM (5 children)
SoylentNews is social media. Says so right in the slogan. Soylentnews is people, not tech.
(Score: 1) by fustakrakich on Tuesday February 04 2020, @05:45AM (4 children)
*sigh* so presumptuous people are... Netscape [seamonkey-project.org]
La politica e i criminali sono la stessa cosa..
(Score: 2) by barbara hudson on Tuesday February 04 2020, @02:39PM (3 children)
Seamonkey is NOT Netscape, any more than any distro based on Debian is Debian. Repeat it until it sticks, mkay? Netscape is dead. You can still download it from some obscure sites, but why bother? Next you'll be claiming that Firefox is also Netscape.
And no, I'm not being presumptuous, just accurate. Netscape died in 2008 when AOL killed it. Tell someone to download Netscape today, they will end up on those cruddy spyware sites.
SoylentNews is social media. Says so right in the slogan. Soylentnews is people, not tech.
(Score: 2, Informative) by fustakrakich on Tuesday February 04 2020, @05:22PM (2 children)
Yes it is, a fully intact Netscape, with the same interface and innards it always had [with one or two additions to play your cat vids and deal with all that stupid HTTPS stuff]. Only the name has changed, officially, but the program is still Netscape, and it is still the best browser you will ever find.
Back on topic, please, since you "went in", what did the article say about the hack? Did they stick a bobby pin into the throttle quadrant [mcstatic.com]?
La politica e i criminali sono la stessa cosa..
(Score: 2) by barbara hudson on Tuesday February 04 2020, @06:56PM (1 child)
SoylentNews is social media. Says so right in the slogan. Soylentnews is people, not tech.
(Score: 1) by fustakrakich on Tuesday February 04 2020, @07:04PM
Unlike your example Seamonkey is not a fork
La politica e i criminali sono la stessa cosa..
(Score: 1, Informative) by Anonymous Coward on Tuesday February 04 2020, @02:14AM
With palemoon 28.8.2, noscript, cookiemasters, and the SteveBlack hosts file (with my edits to allow some sites I want), I see no adds.
Blocking all javascript still allows that url to be completely readable
https://arstechnica.com/science/2020/01/a-deep-dive-into-the-apollo-guidance-computer-and-the-hack-that-saved-apollo-14/ [arstechnica.com]
Did not check for images that track.
I am booted off of a read-only live linux squashfs image (writable overlay in RAM), so even if that site deposits tracking, its gone on the next boot.
There are ways to deal with ads, tracking etc.
(Score: 1, Funny) by Anonymous Coward on Tuesday February 04 2020, @03:59AM
I'd worry more about the grues if I were you.
(Score: 0) by Anonymous Coward on Tuesday February 04 2020, @10:02AM (1 child)
Fortunately NoScript with total blocking works, making the page totally OK, blocking 8 JS ?malicious-looking? domains, plus Arstechnica's scripts.
(Score: 2) by barbara hudson on Tuesday February 04 2020, @02:41PM
SoylentNews is social media. Says so right in the slogan. Soylentnews is people, not tech.