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#11
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WILL THE ATV DELIVER?
rk writes:
The bigger "mega-project" Mars failure was, from dim memory, a fairly complex failure mode in the propulsion system that just wasn't understood until the clarity of hindsight kicked in. The real failure here was putting "all your eggs in one basket". The failure of a "mega-project" is necessarily more painful than the failure of a smaller, less ambitious mission. Mars Polar Lander's failure, if it was in fact the software not reinitializing a variable that said contact was made on the surface, a result of the transient from the Hall effect sensor, was a problem with the requirements writing, the software, verification, and finally the testing. I don't recall anything very complex about this one. For Mars Climate Observer, again, it wasn't a complex failure mechanism. The error was in the reuse of the code from Mars Global Survery and the swapping out of equations suppplied to Lockheed-Martin by the thruster manufacturer, compounded by verification and test not catching it, along with the navigation error not generating corrective action. I was thinking of the one that most likely blew up. Where is that... Here it is. Mars Observer. Here is a reference: http://klabs.org/richcontent/Reports..._a01-34322.pdf http://www.msss.com/mars/observer/pr...ss/moloss.html http://www.msss.com/mars/observer/pr...sa_mo_loss.txt As you can see, there was one most likely cause (failure of the propulsion system due to fuel leaking past check valves during the long cruise to Mars), but several other possible causes were also identified. This wasn't a clear cut case where "more testing" could have saved the craft. The "root causes" were numerous in this case. Again, this was a driving force for smaller, more numerous planetary probes instead of large, expensive, infrequent probes (that cause much pain when you lose one). Jeff -- Remove "no" and "spam" from email address to reply. If it says "This is not spam!", it's surely a lie. |
#12
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WILL THE ATV DELIVER?
"Hallerb" wrote
Honestly all of you know my grammar isnt good. But I am interested in space which is more than 99% of americans, or so it seems...... Well, you're not a stupid guy, Bob. You've been told *repeatedly* that it's "would have", not "would of". Would it be so hard for you to make the change? Write it on a piece of paper and stick it on your monitor! So, tell me, should the company go with the one they can't afford and end up filing for bankruptcy, or go with the one they can afford and hopefully be able to upgrade when money becomes less tight? If the failure can cause them to go bankupt or ut of business they need to find another way. No, Bob, the failure won't do that--buying the expensive option for failover would. |
#13
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WILL THE ATV DELIVER?
Again, this was a driving force for smaller, more numerous planetary probes instead of large, expensive, infrequent probes (that cause much pain when you lose one). Jeff No the driving force was saving money even thoughj the track record for smaller probes is poor science return. The mega probes tended to be tested and run better and overall have had better results. The FBC ones well |
#14
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WILL THE ATV DELIVER?
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#15
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WILL THE ATV DELIVER?
rk said:
WILL THE ATV DELIVER? Completion of ESA’s Automated Transfer Vehicle has A few questions. Anyone know how much software (LOC, instruction and data space sizes) is involved here? Oh dear. These statistics are easy to measure, but that doesn't mean they are important. More interesting would be a measure of the complexity of the code, as that correlates better with the effort required to get the system working. * Testing and Simulation They have a section titled "Building confidence through testing" That's worrisome. To quote the great programmer, testing can only show the presence of bugs, never the absence. (Testing is necessary, it isn't sufficient.) -- Kevin Willoughby lid We'd spend the remaining time trying to fix the engine. -- Neil Armstrong |
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