[time-nuts] MTBF (was Rubidium standard)
phill.r1 at btinternet.com
Wed Nov 18 23:25:23 UTC 2009
What is the title / details of the book that you refer too ?
----- Original Message -----
From: <SAIDJACK at aol.com>
To: <time-nuts at febo.com>
Sent: Wednesday, November 18, 2009 11:01 PM
Subject: Re: [time-nuts] MTBF (was Rubidium standard)
> 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..
> 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
> use!! It cannot tell you anything mathematically about the extrapolated
> life....this has become another urban myth. If it works it is more by
> that by mathematical probability.
> Alan G3NYK
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