Re: Please do not start a language war (was Re: Papers on the Ariane-5 crash and Design by Contract

[Ken Garlington <GarlingtonKE@lmtas.lmco.com>]

Jean-Marc Jezequel wrote:
> 
> In article <332ED8AB.21E7@lmtas.lmco.com>, Ken Garlington <GarlingtonKE@lmtas.lmco.com> writes:
> 
> >   2. No one ran a full integration test with realistic flight data,
> >which would have
> >      alerted them to the mistake made in #1. Particularly for a
> >distributed mission-
> >      critical system, this should be considered an absolute
> >requirement.
> 
> Yes, this is true. But you have to understand that the mere design of the SRI
> made it very difficult to test it in an other way that performing a launch.
> This is because of the tight integration of hard-to-fool hardware with software
> in a black box functional unit. What can be your test strategy for a black box
> containing an inertial central? If the software had been designed with less coupling
> on this particular hardware, you could have test the software vs. a simulation of the
> hardware and its environment. Here, the launch was the test.

Read the final report. If you don't have a copy, see:

http://www.esrin.esa.it/htdocs/tidc/Press/Press96/ariane5rep.html

In particular:

"It should be noted that for reasons of physical law, it is not
feasible to test the SRI as a "black box" in the flight environment,
unless one makes a completely realistic flight test, but it is possible
to do ground testing by injecting simulated accelerometric signals in
accordance with predicted flight parameters, while also using a
turntable
to simulate launcher angular movements. Had such a test been performed
by
the supplier or as part of the acceptance test, the failure mechanism
would have been exposed."

If language is a problem, I believe the report is also available in
French.

As someone who, today, is performing testing of coupled IRS and flight
control systems in a ground-based environment, I am quite confident in
the conclusions of the paper on this point.

> Jean-Marc Jezequel               Tel : +33 2 99847192
> IRISA/CNRS                       Fax : +33 2 99847171
> Campus de Beaulieu               e-mail : jezequel@irisa.fr
> F-35042 RENNES (FRANCE)          http://www.irisa.fr/pampa/PROF/jmj.html

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