> It
> turned out that the cause of the failure was a software error 
> in the inertial reference system.

NO NO NO

Not everything that goes wrong and has software involved is a software
error.

Within its design limitations the software functioned exactly as
specified, hence it was NOT a software error. The execption handling was
turned off deliberately and this was fully documented. The software was
written for the Ariane 4, and within the physical limitation of this
rocket the fatal execptions could simply not occur. This was fully
analysed.

What happened was that the Ariane 4 software was re-used in the Ariane
5, withou re-analysis or tests, and apparently without any technical
person even reading the documentation. This is a management stupidity,
not a software error. IIRC the tests were originally planned, but
removed as a cost reduction. The French attitude in this aspect can be
summarised as "it has already flown in space succesfully, so it must be
OK".

The difference between the 4 and the 5 is that the Ariane 5 relies much
more on quick-burning solid fuel boosters (those two big thingies to the
side of the main body), hence she has a much higher acceleration in the
first part of her flight. This (high acceleration) was the parameter for
which the Ariane 4 software was not designed.

When the Ariane 5 made its maiden flight I was in the main hall of
Fokker Space (a Dutch space company). All (~250) employees were gathered
in front of a big video wall to see her maiden flight, which included
the first flight of some Dutch Space produced parts (IIRC the engine
frame). There was a large cake and champain. Everyone was very
cheerfull, but sudenly the whole hall was totally qiet. We did ate the
cake, but the champain was left in the bottles. I was the software
'troubleshooter' for a big project (thye ERA robot arm) so I read the
reports with great interest and we had a lot of discussions about it.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu
 

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