From: alain245@videotron.ca   
      
   On Oct/4/2020 at 16:35, JF Mezei wrote :   
   > Is it just me or are non-weather aborts generally at the last   
   > minute/second ?   
   >   
   >   
   > I can understand events related to engine ignition that would cause an   
   > abort. But for everything else, don't they have sensors that   
   > continuously monitor everything and they would know of a problem well   
   > before T-2 ?   
   >   
   > If X is showing off-nominal reading 1 minute before launch, what are the   
   > odds that X will magically fix itself so software waits till the very   
   > last second in case it fixes itself?   
      
   They don't do that. In some cases if the reading is borderline, they   
   might discuss the situation and decide if they cancel launch if they   
   have some time to spare to do that. But I think that was mostly a few   
   decades ago that they would wait before cancelling launch if the reading   
   was borderline. I think nowadays, they have quite precise rules for when   
   to cancel, if readings go beyond they cancel they don't wait.   
      
   Last second aborts are usually because something that should happen in   
   the last seconds before launch didn't happen the way it was supposed to   
   do. They don't just wait until the clock ticks to zero and then flip the   
   switch for launch. There is a sequence, and if something goes wrong in   
   the sequence they abort.   
      
      
   Alain Fournier   
      
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