Opinions on safety of dropbox ???

[Nan and Sandy Sanders]

There were 5 computers. Number 5 was a backup running software 
written by a separate  team. I don't think it was ever used.

 From http://history.nasa.gov/computers/Ch4-4.html ;

"One reason why the redundancy management software was able to be 
kept to a minimum is that NASA decided to move voting to the 
actuators, rather than to do it before commands are sent on buses. 
Each actuator is quadruple redundant. If a single computer fails, it 
continues to send commands to an actuator until the crew takes it out 
of the redundant set. Since the Shuttle's other three computers are 
sending apparently correct commands to their actuators, the failed 
computer's commands are physically out-voted. Theoretically, the only 
serious possibility is that three computers would fail 
simultaneously, thus negating the effects of the voting. If that 
occurs, and if the proper warnings are given, the crew can then 
engage the backup system simply by pressing a button located on each 
of the forward rotational hand controllers."

      Sandy
      WB5MMB

At 08:29 PM 8/6/2014, Rob Seastrom wrote:

>Tom Azlin W7SUA <tom at w7sua.org> writes:
>
> > I do not remember reading about any failures in the main four
> > computers. Perhaps someone else on list knows more?
>
>Well, not the *flight* computers, but...
>
>http://www.seastrom.com/shuttle.mp3
>
>A little background information here:
>http://office-watch.com/t/n.aspx?a=1329
>
>-r
>
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