Re: Papers on the Ariane-5 crash and Design by Contract

[frank@bigdog.engr.arizona.edu (Frank Manning)]

In article <858850191snz@nezumi.demon.co.uk> Martin@nezumi.demon.co.uk
(Martin Tom Brown) writes:

> Whilst I am generally in agreement, it isn't usually beyond the 
> wit of man to design in a relatively primitive hardware bias on
> servo systems so that they fly top dead centre with no input.
> Or fly round in small circles or whatever the design team decide 
> is the least embarassing failure mode. At least that way the rocket
> survives for long enough that humans can decide kill or cure.

Well, I understand what you're saying, and I agree that generally
this is a good idea.

In this case, though, I suspect the rocket is statically unstable,
which means the nozzles must be actively steered to keep the
vehicle on course. If the nozzles were locked in the center
position, for example, the vehicle would probably start flying
sideways very quickly. Depending on the speed, it would probably be
torn apart.

(Bit of Shuttle trivia -- in the Challenger accident, what destroyed
the orbiter was not an explosion, but the fact that it started
flying sideways when the dynamic pressure was rather high.)

-- Frank Manning