[time-nuts] MTBF (was Rubidium standard)

[Robert Darlington]

Aside from the spare in the LM, they had a backup computer called the abort
guidance system developed by TRW.  I think it was bolted up under a seat
somewhere.

-Bob

On Wed, Nov 18, 2009 at 4:01 PM, <SAIDJACK at aol.com> wrote:

> Hi Alan,
>
> I am reading a book about the Apollo computer, they bet their life on it
> not failing (everything related to spacecraft maneuvering went through the
> computer, there were no mechanical or other backups whatsoever). They only
> had a  single computer per spacecraft!
>
> The book states that based on the entire Apollo program, they later
> estimated the units MTBF to be in excess of 50,000 hours (which is actually
> not  a
> lot compared to what typical GPSDO's can achieve today).
>
> A single transistor, ROM bit, solder-joint, or resistor failure could have
> killed them.
>
> Scary considering they went for 2 week+ missions..
>
> bye,
> Said
>
>
>
>
> In a message dated 11/18/2009 14:38:57 Pacific Standard Time,
> alan.melia at btinternet.com writes:
>
> Sorry  Mike , unless, as someone else said, the figures are derived from
> field  failures over at least a good porton of the expected like the MTBF
> tells  you absolutely nothing!! The statistics used on the usual 1000hour
> test  will only tell you the probability of failure in the first 1000hours
> of
> use!! It cannot tell you anything mathematically about the  extrapolated
> life....this has become another urban myth. If it works it is  more by luck
> that by mathematical probability.
>
> Alan  G3NYK
>
>
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