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: 103376,d901a50a5adfec3c X-Google-Attributes: gid103376,public X-Google-Thread: 1094ba,9f0bf354542633fd X-Google-Attributes: gid1094ba,public From: "Larry Elmore" Subject: Re: Fortran or Ada? Date: 1998/10/03 Message-ID: <6v57cq$b5e$1@news.campus.mci.net>#1/1 X-Deja-AN: 397339926 References: <36068E73.F0398C54@meca.polymtl.ca> <6u8r5o$aa4$1@nnrp1.dejanews.com> <360A3446.8AD84137@lmco.com> <6udre0$ha1$1@nnrp1.dejanews.com> <19980925.185359.250@yktvmv.watson.ibm.com> <6uifdr$dog$1@nnrp1.dejanews.com> <19980928.184428.604@yktvmv.watson.ibm.com> <19981002.190123.114@yktvmv.watson.ibm.com> <36156677.7566@lanl.gov> <19981002.222045.439@yktvmv.watson.ibm.com> X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Organization: CampusMCI Newsgroups: comp.lang.fortran,comp.lang.ada Date: 1998-10-03T00:00:00+00:00 List-Id: jbs@yktvmv.watson.ibm.com wrote in message <19981002.222045.439@yktvmv.watson.ibm.com>... >In article <36156677.7566@lanl.gov>, > on Fri, 02 Oct 1998 17:49:11 -0600, > William Clodius writes: >>jbs@yktvmv.watson.ibm.com wrote: >>> >>> The report I have says nothing like this. What report are >>> you referring to? >>> James B. Shearer >> >>Robert Eachus's comments are "mostly" inferable from the report. He is >>correct that the report says (in equivalent words) that "the stack was >>destroyed when the engine deflection exceeded the physical stress limits >>of the stack (booster and payload)." He is also correct that this >>implies that the software did not properly check that such an engine >>deflection was safe at that thrust. I suspect that he infers from >>presummed best practices that the software would make such a check, and >>that it failed because the physical parameters were wrong, and that the >>most likely reason that they were wrong was because the Ariane 4 >>parameters were used. However, the number of steps used in that >>inference are long and while the individual steps are plausible >>collectively they are less plausible. Further, whether any other system >>malfunction could have caused the software to command that that >>deflection is unknown. > > Actually what the report says is: > >! f) Approx. 0.05 seconds later the active inertial reference system, >! identical to the back-up system in hardware and software, failed for the >! same reason. Since the back-up inertial system was already inoperative, >! correct guidance and attitude information could no longer be obtained and >! loss of the mission was inevitable. >! >! g) As a result of its failure, the active inertial reference system >! transmitted essentially diagnostic information to the launcher's main >! computer, where it was interpreted as flight data and used for flight >! control calculations. >! >! h) On the basis of those calculations the main computer commanded the >! booster nozzles, and somewhat later the main engine nozzle also, to make a >! large correction for an attitude deviation that had not occurred. >! >! i) A rapid change of attitude occurred which caused the launcher to >! disintegrate at 39 seconds after H0 due to aerodynamic forces. >! >! j) Destruction was automatically initiated upon disintegration, as >! designed, at an altitude of 4 km and a distance of 1 km from the launch >! pad. > > I don't see anything in there about the engine deflection >being unsafe in itself, it just pointed the rocket in the wrong >direction. Presumedly a less extreme deflection (error) would just >have delayed the accident a few seconds. Well, _of course_ you didn't see anything in there about the engine deflection being unsafe in itself! That's because no one has suggested anything so foolish. Mr. Eachus wrote: "Note later in the report where it says that the stack was destroyed when the engine deflection exceeded the physical stress limits of the stack (booster and payload). " The failure was due to a management decision to use unchanged the Ariane 4 sub-system without any testing, or even adequate review. LArry