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From: Ken Garlington <garlingtonke@lmtas.lmco.com>
Subject: Re: Ariane 5 failure
Date: 1996/10/07
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references: <agrapsDy4oJH.29G@netcom.com> <52a572$9kk@goanna.cs.rmit.edu.au>
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Date: 1996-10-07T00:00:00+00:00
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Steve Bell wrote:

> Well, the French do things a little differently (but probably now they don't). The
> Ariane 4 and the first Ariane 5 allow(ed) this program to keep running for 40 secs
> past liftoff. They do (did) this in case there are any unanticipated holds in the
> countdown right close to liftoff. In this way, this position and velocity updating
> code would *not* have to be reset if they could get off the ground within just a few
> seconds of nominal.

But why 40 seconds? Why not 1 second (or one millisecond, for that matter)?

> You might take note that this would never happen with a
> Titan because we don't execute this ground software after liftoff. Even if we did, we
> would have caught the floating point overflows way before launch because we run all
> code in what's called "Real-Time Simulations" where actual flight harware and software
> are subjected to any and all known physical conditions. This was another finding of
> the investigation board - apparently the French don't do enough of this type of
> testing because it's real expensive.

Going way back into my history, I believe this is also true for Atlas.

> --
> Clear skies,
> Steve Bell
> sb635@delphi.com
> http://people.delphi.com/sb635 - Astrophoto page

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