[-empyre-] glitch device/divide

Michael Bell mbell at visibleweather.com
Tue Dec 13 04:19:23 EST 2011


pleaes remove me from list
Michael 

........................................
Michael Bell Architecture + Visible Weather 
Professor of Architecture, Columbia University 
Director, Columbia Conference on Architecture, Engineering and Materials
Director, Master of Architecture Program, Core Design Studios 
www.visibleweather.com 
........................................
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On Dec 8, 2011, at 2:54 PM, Julian Oliver wrote:

> Some point earlier, I wrote:
> 
>> In 1996 the European Space Agency's Ariane 5 Flight 501 self destructed due to a
>> glitch in the guidance software.
> 
>> Again, a glitch itself doesn't have to be seen for it to have been highly
>> significant. No one saw the glitch at work in Flight 501, buried deep in the
>> guidance software subsystem. They saw the craft explode as a consequence of the
>> glitch.  Perhaps no one even saw the explosion, but a statistical representation
>> of it a second after all their comms went down.
> 
> In fact they did see the explosion alright.. ouch:
> 
>    http://www.youtube.com/watch?v=kYUrqdUyEpI&feature=related
> 
> Here's the anatomy of the glitch that caused that explosion. To summarise, it
> came down to an Operand Error resulting from an unexpected high value from an
> on-board alignment sensor:
> 
> The launcher started to disintegrate at about H0 + 39 seconds because of
> high aerodynamic loads due to an angle of attack of more than 20 degrees that
> led to separation of the boosters from the main stage, in turn triggering the
> self-destruct system of the launcher.
> 
> This angle of attack was caused by full nozzle deflections of the solid boosters
> and the Vulcain main engine. These nozzle deflections were commanded by the
> On-Board Computer (OBC) software on the basis of data transmitted by the active
> Inertial Reference System (SRI 2). Part of these data at that time did not
> contain proper flight data, but showed a diagnostic bit pattern of the computer
> of the SRI 2, which was interpreted as flight data.
> 
> The reason why the active SRI 2 did not send correct attitude data was that
> the unit had declared a failure due to a software exception.
> 
> The OBC could not switch to the back-up SRI 1 because that unit had already
> ceased to function during the previous data cycle (72 milliseconds period) for
> the same reason as SRI 2.
> 
> 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.
> 
> The error occurred in a part of the software that only performs alignment of
> the strap-down inertial platform. This software module computes meaningful
> results only before lift-off. As soon as the launcher lifts off, this function
> serves no purpose.
> 
> The alignment function is operative for 50 seconds after starting of the
> Flight Mode of the SRIs which occurs at H0 - 3 seconds for Ariane 5.
> Consequently, when lift-off occurs, the function continues for approx. 40
> seconds of flight. This time sequence is based on a requirement of Ariane 4 and
> is not required for Ariane 5.
> 
> The Operand Error occurred due to an unexpected high value of an internal
> alignment function result called BH, Horizontal Bias, related to the horizontal
> velocity sensed by the platform. This value is calculated as an indicator for
> alignment precision over time.
> 
> The value of BH was much higher than expected because the early part of the
> trajectory of Ariane 5 differs from that of Ariane 4 and results in considerably
> higher horizontal velocity values.
> 
> From:
> 
>    http://www.di.unito.it/~damiani/ariane5rep.html
> 
> We hope you enjoy your flight,
> 
> Julian
> 
>> Julian:
>> 
>>> Indeed it is what is relevant, as it is with any cultural trope. It's here
>>> however that software developers like myself find ourselves cynical  
>>> about Glitch
>>> Art precisely because we know that what we're often looking at/listening to is
>>> not a glitch, rather an event designed to have the appearance of one.
>>> 
>>> A glitch-concert using Max MSP is not glitch, rather the application  
>>> of digital
>>> synthesis to mimic sounds that sound like what we understand to be glitch,
>>> namely electrical sparks, servos breaking under load, etc.  Similarly, someone
>>> playing with GTK or Quartz Composer to manipulate a desktop interface 
>>> such that
>>> it performs unexpectedly isn't glitch, it's UX/UI design.
>>> 
>>> This leads us to the question "Can you design a glitch?". Perhaps you can only
>>> design /with/ glitches, not glitches themselves..
>>> 
>>> If glitches are political at all it's in because they represent a possible
>>> entry-point within an otherwise closed system, a 'de-punctualisation' (from
>>> Latour) of the Black Box. What many call glitches are in fact just the 
>>> beginning
>>> of what later becomes an exploit (whether that be jailbreaking a device or
>>> injecting malicious code into a process running on a server). In this way
>>> glitches signal the possibility of further action; an opening, they express
>>> freedom of movement.
>>> 
>>> Purely aesthetic fetishising of glitch depreciates this potential, I think.
>>> After all, some of the most potent and transformative glitches in  
>>> technological
>>> history are quite boring to behold. To most, they'd probably go unnoticed.
>>> 
>>> Cheers,
>>> 
>>> Julian
>> _______________________________________________
>> empyre forum
>> empyre at lists.cofa.unsw.edu.au
>> http://www.subtle.net/empyre
> 
> -- 
> Julian Oliver
> http://julianoliver.com
> http://criticalengineering.org
> _______________________________________________
> empyre forum
> empyre at lists.cofa.unsw.edu.au
> http://www.subtle.net/empyre
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> empyre forum
> empyre at lists.cofa.unsw.edu.au
> http://www.subtle.net/empyre
> 

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