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From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: Fortran or Ada?
Date: 1998/10/06
Message-ID: <EACHUS.98Oct6190844@spectre.mitre.org>#1/1
X-Deja-AN: 398434925
References: <36068E73.F0398C54@meca.polymtl.ca>
 <slrn70dv6k.2qp.gisle@krake.ii.uib.no> <m3n27sqhms.fsf@visar.physast.uga.edu>
 <6u8r5o$aa4$1@nnrp1.dejanews.com> <m3zpbq24wq.fsf@visar.physast.uga.edu>
 <360A3446.8AD84137@lmco.com> <6udre0$ha1$1@nnrp1.dejanews.com>
 <19980925.185359.250@yktvmv.watson.ibm.com> <6uifdr$dog$1@nnrp1.dejanews.com>
 <19980928.184428.604@yktvmv.watson.ibm.com>
 <EACHUS.98Oct2160023@spectre.mitre.org>
 <19981002.190123.114@yktvmv.watson.ibm.com> <36156677.7566@lanl.gov>
 <19981002.222045.439@yktvmv.watson.ibm.com>
Organization: The Mitre Corp., Bedford, MA.
Newsgroups: comp.lang.fortran,comp.lang.ada
Date: 1998-10-06T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <19981002.222045.439@yktvmv.watson.ibm.com> jbs@yktvmv.watson.ibm.com writes:
!    h) On the basis of those calculations the main computer commanded the
!    booster nozzles, and somewhat later the main engine nozzle also, to make a
!    large correction for an attitude deviation that had not occurred.

!    i) A rapid change of attitude occurred which caused the launcher to
!    disintegrate at 39 seconds after H0 due to aerodynamic forces.
...

  >	    I don't see anything in there about the engine deflection
  > being unsafe in itself, it just pointed the rocket in the wrong
  > direction.  Presumedly a less extreme deflection (error) would just
  > have delayed the accident a few seconds.

    No a less extreme deflection would have resulted in the stack
being off course, but still in one piece.  If the course deviation had
been real, due to say heavy wind shear, the stack could have later
returned to a correct course.  But once you go beyond the (hopefully
known) stress limits, you don't have a launcher, you have a large
number of parts in loose formation.  Note that the main computer, not
the inertial guidance system ordered the deflection, and my
understanding is that it was using Arianne 4 deflection limits.
(Arianne 4 had a lower thrust to weight ratio, and was not as tall.)
--

					Robert I. Eachus

with Standard_Disclaimer;
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