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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 101deb,f96f757d5586710a X-Google-Attributes: gid101deb,public X-Google-Thread: 103376,5ac12f5a60b1bfe X-Google-Attributes: gid103376,public X-Google-Thread: f43e6,5ac12f5a60b1bfe X-Google-Attributes: gidf43e6,public From: Ken Garlington Subject: Re: Ariane 5 - not an exception? Date: 1996/07/30 Message-ID: <31FE07FE.4592@lmtas.lmco.com>#1/1 X-Deja-AN: 171129139 references: <4t9vdg$jfb@goanna.cs.rmit.edu.au> <4tiu6e$kpm@news2.cais.com> content-type: text/plain; charset=us-ascii organization: Lockheed Martin Tactical Aircraft Systems mime-version: 1.0 newsgroups: comp.software-eng,comp.lang.ada,comp.lang.pl1 x-mailer: Mozilla 2.02 (Macintosh; I; 68K) Date: 1996-07-30T00:00:00+00:00 List-Id: Bill Angel wrote: > > I am under the impression that for the US manned spaceflight > program (to get to the moon) ,an on-board computer that was serving as a > backup to the primary computer would have been performing its computations > using completely different software than the primary computer. By > utilizing this methodology, the same software "glitch" would not halt both > systems simultaneously. Perhaps a group of software developers could be > tasked with producing a version of the on-board software for Ariane in a > different computer language than that used by the primary processor. The > two processors, running simultaneously, would serve to check each other's > results with greater independence that they apparently do now. The problem with N-version programming is the common mode requirements error. See Dr. Levison's work, which fits my own experience. In this case, if both systems had the same problems with throughput margins, and the same basic information regarding the need to protect calculations were available to both teams, the very likely would have chosen the same (wrong) design solution. -- LMTAS - "Our Brand Means Quality"