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: f43e6,5ac12f5a60b1bfe X-Google-Attributes: gidf43e6,public X-Google-Thread: 103376,5ac12f5a60b1bfe X-Google-Attributes: gid103376,public From: Ken Garlington Subject: Re: Ariane 5 - not an exception? Date: 1996/08/06 Message-ID: <32076E31.23E@lmtas.lmco.com>#1/1 X-Deja-AN: 172583767 references: <4t9vdg$jfb@goanna.cs.rmit.edu.au> <31FE35BC.1A0D@sanders.lockheed.com> <4totv7$o9f@goanna.cs.rmit.edu.au> <3200E43C.2AA9@lmtas.lmco.com> <839266234.26317.0@assen.demon.co.uk> 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: 1996-08-06T00:00:00+00:00 List-Id: John McCabe wrote: > > If you checks through the report again, you'll notice that having the > alignment function running up to 40 seconds after lift-off was not an > applicable requirement for Ariane 5, it was left over from Ariane 4. Right. Notice, however, that even on the Ariane 4, the alignment function continued to run, but _not_ apply correction vectors, prior to lift-off. I always had the impression that when an IRS was in alignment mode, it could not be in operational mode, and vice versa. It sounds like this IRS was designed to have a "pseudo" alignment mode, which would continue to calculate corrections, but only apply them when the IRS was in "true" alignment mode. As I understood the report, this "pseudo" mode was designed to allow quick entry and exit into the "true" alignment mode for quick updates prior to launch. If the Ariane 4 did not have this design feature of a "pseudo" mode, then the alignment task would have been disabled completely as soon as the IRS moved -- whether on the Ariane 4 or Ariane 5 -- and so the alignment calculations would not have been running in either case. There is a lesson learned here about adding too many "neat" features to safety-critical software. -- LMTAS - "Our Brand Means Quality"