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=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,CP1252 X-Google-Thread: 103376,f039470e8f537101 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-07-22 14:24:14 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!arclight.uoregon.edu!wn13feed!worldnet.att.net!204.127.198.203!attbi_feed3!attbi.com!rwcrnsc54.POSTED!not-for-mail Message-ID: <3F1DAB65.1090004@attbi.com> From: "Robert I. Eachus" User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.0.2) Gecko/20021120 Netscape/7.01 X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: Ariane5 FAQ References: <1058799152.775376@master.nyc.kbcfp.com> <1058810510.375902@master.nyc.kbcfp.com> <3f1c374f$0$11375$cc9e4d1f@news.dial.pipex.com> <3f1ce57f$1@news.wineasy.se> <1058900795.12630@master.nyc.kbcfp.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit NNTP-Posting-Host: 66.31.71.243 X-Complaints-To: abuse@comcast.net X-Trace: rwcrnsc54 1058909053 66.31.71.243 (Tue, 22 Jul 2003 21:24:13 GMT) NNTP-Posting-Date: Tue, 22 Jul 2003 21:24:13 GMT Organization: Comcast Online Date: Tue, 22 Jul 2003 21:24:13 GMT Xref: archiver1.google.com comp.lang.ada:40671 Date: 2003-07-22T21:24:13+00:00 List-Id: Hyman Rosen wrote: > They didn't just move the software, they moved the hardware too. > I don't "want" anything. The investigatory report says that the > Ariane 4 SRI software and documentation failed to make obviously > clear its dependence on the details of the Ariane 4 flight path, > which helped lead to the assumption by the Ariane 5 people that > it would "just work". The failure to check for overflow in the > Ariane 4 code was not an essential part of its operation, but a > shortcut taken in order to reduce CPU usage. Software which has > such sensitive dependency on input is brittle and fragile, and > should accordingly come plastered with warning stickers. Why, why, do you keep spouting this nonsense? The documentation for the SRI software not only showed a dependence on the Ariane 4 flight path, but it explicitly stated that it had not been checked against the Ariane 5 requirements. The massive failure was the direct result of the political and management decisions which prevented the (Ariane 4 project) SRI engineers from seeing the Ariane 5 requirements, and prevented all the engineers, software, hardware, and test employed on the Ariane 5 development from ever seeing the Ariane 4 SRI documentation. Now I could go on long and loud about a contract situation where the Ariane 4 SRI upgrade was performened under those circumstances. But I wouldn't expect it to have these consequences. It was the combination of several separate management decisions, each of which can be criticised in hindsight, but all with the same engineering consequence, the Ariane 5 REQUIREMENTS were never compared to the Ariane 4 SRI SPECIFICATION. If that had happened several major problems INCLUDING this one would have been discovered. In fact, the actual failure was caused by another of these mismatches. The software for the engine controllers was set to take the data from the SRI, compare it to the (current) stack limits then pass either the maximum permitted deflection or the requested deflection to the servos. So what happened when the engine controllers got junk data? The engines were deflected to the structural limit for the Ariane 4 stack at this point in its flight profile. Of course, the Ariane 5 stack was bigger, the aerodynamic stresses greater, and it disintegrated. Then the range safety officer triggered the self-destruct. The same thing could have happened if Ariane 501 had hit wind shear. Also the SRI software used the Ariane 4 moments of inertia in its control laws. The report seems to indicate that there was a 10 Hz ocillation building up due to this. If it had gone on would that have been sufficient to destroy Ariane 501? Probably. -- Robert I. Eachus �In an ally, considerations of house, clan, planet, race are insignificant beside two prime questions, which are: 1. Can he shoot? 2. Will he aim at your enemy?� -- from the Laiden novels by Sharon Lee and Steve Miller.