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From: rav@goanna.cs.rmit.edu.au (@@           robin)
Subject: Re: Ariane 5 failure
Date: 1996/10/04
Message-ID: <532k32$r4r@goanna.cs.rmit.edu.au>#1/1
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references: <agrapsDy4oJH.29G@netcom.com> <52a572$9kk@goanna.cs.rmit.edu.au>
 <843845039.4461.0@assen.demon.co.uk>
organization: Comp Sci, RMIT, Melbourne, Australia
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Date: 1996-10-04T00:00:00+00:00
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	john@assen.demon.co.uk (John McCabe) writes:

	>Just a point for your information. From clari.tw.space:

	>	 "An inquiry board investigating the explosion concluded in  
	>July that the failure was caused by software design errors in a 
	>guidance system."

	>Note software DESIGN errors - not programming errors.

	>Best Regards
	>John McCabe <john@assen.demon.co.uk>

---If you read the Report, you'll see that that's not the case.
This is what the report says:


    "* The internal SRI software exception was caused during execution of a
     data conversion from 64-bit floating point to 16-bit signed integer
     value. The floating point number which was converted had a value
     greater than what could be represented by a 16-bit signed integer.
     This resulted in an Operand Error. The data conversion instructions
     (in Ada code) were not protected from causing an Operand Error,
     although other conversions of comparable variables in the same place
     in the code were protected.

    "In the failure scenario, the primary technical causes are the Operand Error
    when converting the horizontal bias variable BH, and the lack of protection
    of this conversion which caused the SRI computer to stop."

---As you can see, it's clearly a programming error.  It's a failure
to check for overflow on converting a double precision value to
a 16-bit integer.