From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-0.4 required=5.0 tests=AC_FROM_MANY_DOTS,BAYES_00 autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,c617ae447ca32f2f X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2002-04-12 04:15:08 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!newsfeeds.belnet.be!news.belnet.be!news-x2.support.nl!psinet-eu-nl!psiuk-p4!uknet!psiuk-p3!uknet!psiuk-n!news.pace.co.uk!nh.pace.co.uk!not-for-mail From: "Marin David Condic" Newsgroups: comp.lang.ada Subject: Re: Ariane Failure Date: Thu, 11 Apr 2002 09:17:15 -0400 Organization: Posted on a server owned by Pace Micro Technology plc Message-ID: References: <3CA50E9A.CBF24F1B@lanl.gov> <3CB3031A.26E08904@gbr.msd.ray.com> <3CB435A4.8A011DF1@gbr.msd.ray.com> <3CB4DD65.99F17199@top.monad.net> NNTP-Posting-Host: dhcp-200-133.miami.pace.co.uk X-Trace: nh.pace.co.uk 1018531037 14551 136.170.200.133 (11 Apr 2002 13:17:17 GMT) X-Complaints-To: newsmaster@news.cam.pace.co.uk NNTP-Posting-Date: 11 Apr 2002 13:17:17 GMT X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4522.1200 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200 Xref: archiver1.google.com comp.lang.ada:22417 Date: 2002-04-11T13:17:17+00:00 List-Id: "Steve O'Neill" wrote in message news:3CB4DD65.99F17199@top.monad.net... > > Agreed... except when the potential result may be raining down flaming > pieces of a billion dollars worth of satellite. As I recall the photos > were very impressive. > Well, I'm impressed by the photos too. It can be very educational to engineers to look over the videos and photos of various engineering disasters. There are plenty to choose from. I'll still disagree that dual-redundant identical systems are a bad idea in rocket technology and that they are somehow inherently less safe than dissimilar systems. Having worked in that field I know some of the thinking that goes into these sorts of designs and lots of highly reliable identical systems have been built. "Dissimilar" only protects you from common design errors - maybe. It also increases the probability that there *will* be a design error. When considering the potential designs for a given piece of avionics, you need to look very carefully at all the possible failure modes you can think of and look at the probabilities of those failures occurring and ask how well a given design strategy will minimize the risk. Dual redundant, identical systems can and do function very well and at very high levels of reliability and it isn't automatically clear that for a given application a dual redundant dissimilar system is going to improve reliability. In fact, quite the opposite might be the case. MDC -- Marin David Condic Senior Software Engineer Pace Micro Technology Americas www.pacemicro.com Enabling the digital revolution e-Mail: marin.condic@pacemicro.com