Hello, I'm a newbie to this list, steered to it by MIT's David Chandler.
I've just published my first book, "Left Brains for the Right Stuff:
Computers, Space, and History" (do I have to put an [AD] flag here just for
mentioning that?). It's based on my Apollo and Space Shuttle work at MIT
Instrumentation/Draper Lab, 1959-1981, and one thing I do there is trace the
understanding of these program alarms from the very first hint of their
possibility as a consequence of Rendezvous Radar configuration.
I had to flip a coin to see whether to post to this thread or the Apollo 11
alarms thread, and I found a particularly stimulating assertion here: "...
the probability that Apollo 11, as flown, would have them during descent was
was actually 100%." My research, in which Don Eyles and the late George
Silver participated, shows that the probability was about 1% if you admit
that the exact instant of powering up the LM systems was a random variable
impossible to control. And I report that the NASA powers involved estimated
the probability as "way too small to worry about" compared to all the other
interesting risks in the project. But certainly our design of the system
software to deal flexibly with any unforeseen contingency was essential to
the mission's success. I'm confident that many who post to these threads
will find my book a useful resource! [/AD]
Hugh Blair-Smith
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of Henry Spencer
Sent: Sunday, January 17, 2016 11:20 PM
To: Arocket List
Subject: [AR] failure recovery (was Re: Re: Flight Controller Features)
On Sat, 16 Jan 2016, Norman Yarvin wrote:
...if you really needed a piece of state, that might not be enough; you
might have to save two copies of it, each with a checksum, and refresh
them alternately.
That level of paranoia, worrying about rare subcases of rare cases, is
worth it when one is writing an operating system to be used by
millions of people. For amateur rockets, not so much: you're not
going to have literally trillions of tries at hitting the ultra-rare
behavior.