[time-nuts] MTBF (was Rubidium standard)

[SAIDJACK at aol.com]

Hi Poul,
 
that AGS system existed only on the LEM, and only to abort  a lunar 
landing. It couldn't even dock the two craft.
 
Mindell discusses in great detail how they went to a single-computer  
digital Autopilot on pages 138 to 143, because they considered a failure so  
remote as to being able to do away with redundant computers, or in-flight  
repair. Since all CM thrusters are controlled by the CM computer  software, a 
landing would not be possible without it. See also figure 6.2  on page 142.
 
But I think there was a manual way to start/stop the main engines, so maybe 
 this would have been useful if the main computer failed to at least get 
back  into an earth orbit?
 
This was apparently the very first fully-digital 100% fly-by-wire  system 
ever, and probably the last one that did not have redundant computer  backup.
 
bye,
Said
 
 
In a message dated 11/18/2009 15:30:36 Pacific Standard Time,  
phk at phk.freebsd.dk writes:

In  message <d03.691da87f.3835dc47 at aol.com>, SAIDJACK at aol.com  writes:

>No CM computer, no return to earth. I think this is also  discussed in  
the 
>movie Apollo  13.

http://history.nasa.gov/ says otherwise.

Lot of good stuff  there.

In particular:
http://history.nasa.gov/computers/Part1.html