Re: Ariane5 FAQ

[aek@vib.usr.pu.ru (Alexander Kopilovitch)]

Robert I. Eachus wrote:

>As far as I know the simulation developers did have ACCESS to all of the
>source code.  It was the documentation that they didn't have.  So some
>programmer might have noticed that the alignment code ran for 40 seconds
>after ignition, but without the documentation the hypothetical
>simulation programmer had no reason to doubt that it was done for valid
>reasons.

Thank you for clarification of this point. So, I'm going to change the answer
(the "Q" remains unchanged) in the next draft of the FAQ, to the following:

----------------------------------------------------------------------------
Q. So, if the limitations were clearly reflected in comments within the source
code then most probably they would be seen by the simulator's developers and
the disaster would be averted?

A. Probably No. Because simulation of the alignment function of real device
was excluded from the contract for the simulator development. Consequently,
the simulator's developers have no stimulus (without the documentation, which
was not given to them) to look into the part of the source code where the
limitations were violated in the flight. (They may look there out of curiosity,
but time pressure and general stress surrounding the project left too little
room for curiosity.)

The reason for omission of the alignment function from the simulator was that
for Ariane 5 that function is not needed after takeoff, and that before
takeoff that function was really identical for the Ariane 4 and Ariane 5.
What was overlooked is that for the Ariane 4 that function WAS executed after
takeoff (about 40 seconds), so the unchanged real device will execute that
function for the Ariane 5 despite the absence of any need for it there.
----------------------------------------------------------------------------



Alexander Kopilovitch                      aek@vib.usr.pu.ru
Saint-Petersburg
Russia