5 ms·

The shuttle computer does what computers do best: crunch numbers. I'd be interested in knowing what sort of hardware that RAM plugs in to, and also exactly how

The shuttle computer does what computers do best: crunch numbers. I'd be interested in knowing what sort of hardware that RAM plugs in to, and also exactly how fast operations need to be completed in order for the shuttle to not fall out of the sky.

Retric 17y ago
The shuttle uses 4 separate 1.2MHz IBM AP-101 operating in lockstep / redundant systems, with a 5th running an independent system. I assume the fifth is setup in case of software failures. http://en.wikipedia.org/wiki/IBM_AP-101 http://en.wikipedia.org/wiki/IBM_AP-101 http://en.wikipedia.org/wiki/Space_Shuttle http://en.wikipedia.org/wiki/Space_Shuttle PS: It's easy to forget just how old and hacked together the Space Shuttle is: Historically, the Shuttle was not launched if its flight would run from December to January (a year-end rollover or YERO). Its flight software, designed in the 1970s, was not designed for this, and would require the orbiter's computers be reset through a change of year, which could cause a glitch while in orbit. In 2007, NASA engineers devised a solution so Shuttle flights could cross the year-end boundary.[38]
- brk 17y ago
  * I assume the fifth is setup in case of software failures.* It is. The 5th has just enough to get the shuttle home, and is designed by a separate team. The presumption being that anything that knocked out the first 4 is probably a systematic failure.
- skoob 17y ago
  That's weird. Why would they even need date logic in the flight software?
  - sophacles 17y ago
    It probably has something to do with where to point the thing during re-entry. The shuttle would need to be able to land on different days in case something went wrong. Actually, the date stuff is probably used for all sorts of orbital calculations.
  - kjhgfvgbjnm 17y ago
    It doesn't - but can you guarantee that everything it is talking to doesn't also change? A GPS string might erroneously say it's day 367 or be one character too long because it printed 20010 or a telemetry link might ask for 4million readings because it calculated "-1"

Retric 17y ago

The shuttle uses 4 separate 1.2MHz IBM AP-101 operating in lockstep / redundant systems, with a 5th running an independent system. I assume the fifth is setup in case of software failures. http://en.wikipedia.org/wiki/IBM_AP-101 http://en.wikipedia.org/wiki/IBM_AP-101 http://en.wikipedia.org/wiki/Space_Shuttle http://en.wikipedia.org/wiki/Space_Shuttle PS: It's easy to forget just how old and hacked together the Space Shuttle is: Historically, the Shuttle was not launched if its flight would run from December to January (a year-end rollover or YERO). Its flight software, designed in the 1970s, was not designed for this, and would require the orbiter's computers be reset through a change of year, which could cause a glitch while in orbit. In 2007, NASA engineers devised a solution so Shuttle flights could cross the year-end boundary.[38]

brk 17y ago
* I assume the fifth is setup in case of software failures.* It is. The 5th has just enough to get the shuttle home, and is designed by a separate team. The presumption being that anything that knocked out the first 4 is probably a systematic failure.
skoob 17y ago
That's weird. Why would they even need date logic in the flight software?
- sophacles 17y ago
  It probably has something to do with where to point the thing during re-entry. The shuttle would need to be able to land on different days in case something went wrong. Actually, the date stuff is probably used for all sorts of orbital calculations.
- kjhgfvgbjnm 17y ago
  It doesn't - but can you guarantee that everything it is talking to doesn't also change? A GPS string might erroneously say it's day 367 or be one character too long because it printed 20010 or a telemetry link might ask for 4million readings because it calculated "-1"