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WILL THE ATV DELIVER?



 
 
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  #11  
Old July 18th 03, 04:36 PM
jeff findley
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Default WILL THE ATV DELIVER?

rk writes:
The bigger "mega-project" Mars failure was, from dim memory, a
fairly complex failure mode in the propulsion system that just
wasn't understood until the clarity of hindsight kicked in. The
real failure here was putting "all your eggs in one basket". The
failure of a "mega-project" is necessarily more painful than the
failure of a smaller, less ambitious mission.


Mars Polar Lander's failure, if it was in fact the software not
reinitializing a variable that said contact was made on the surface, a
result of the transient from the Hall effect sensor, was a problem with
the requirements writing, the software, verification, and finally the
testing. I don't recall anything very complex about this one.

For Mars Climate Observer, again, it wasn't a complex failure mechanism.
The error was in the reuse of the code from Mars Global Survery and the
swapping out of equations suppplied to Lockheed-Martin by the thruster
manufacturer, compounded by verification and test not catching it, along
with the navigation error not generating corrective action.


I was thinking of the one that most likely blew up. Where is that...
Here it is. Mars Observer. Here is a reference:

http://klabs.org/richcontent/Reports..._a01-34322.pdf
http://www.msss.com/mars/observer/pr...ss/moloss.html
http://www.msss.com/mars/observer/pr...sa_mo_loss.txt

As you can see, there was one most likely cause (failure of the
propulsion system due to fuel leaking past check valves during the
long cruise to Mars), but several other possible causes were also
identified. This wasn't a clear cut case where "more testing" could
have saved the craft. The "root causes" were numerous in this case.

Again, this was a driving force for smaller, more numerous planetary
probes instead of large, expensive, infrequent probes (that cause much
pain when you lose one).

Jeff
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  #12  
Old July 18th 03, 05:10 PM
Rick C
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Default WILL THE ATV DELIVER?

"Hallerb" wrote

Honestly all of you know my grammar isnt good. But I am interested in

space
which is more than 99% of americans, or so it seems......


Well, you're not a stupid guy, Bob. You've been told *repeatedly* that it's
"would have", not "would of". Would it be so hard for you to make the
change? Write it on a piece of paper and stick it on your monitor!


So, tell me, should the company go with the one they can't afford and end

up
filing for bankruptcy, or go with the one they can afford and hopefully

be
able to upgrade when money becomes less tight?


If the failure can cause them to go bankupt or ut of business they need to

find
another way.


No, Bob, the failure won't do that--buying the expensive option for failover
would.



  #13  
Old July 18th 03, 07:15 PM
Hallerb
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Default WILL THE ATV DELIVER?


Again, this was a driving force for smaller, more numerous planetary
probes instead of large, expensive, infrequent probes (that cause much
pain when you lose one).

Jeff


No the driving force was saving money even thoughj the track record for smaller
probes is poor science return.

The mega probes tended to be tested and run better and overall have had better
results.

The FBC ones well
  #15  
Old July 20th 03, 05:03 AM
Kevin Willoughby
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Default WILL THE ATV DELIVER?

rk said:
WILL THE ATV DELIVER?
Completion of ESA’s Automated Transfer Vehicle has

A few questions. Anyone know how much software (LOC, instruction and
data space sizes) is involved here?


Oh dear. These statistics are easy to measure, but that doesn't mean
they are important. More interesting would be a measure of the
complexity of the code, as that correlates better with the effort
required to get the system working.


* Testing and Simulation

They have a section titled "Building confidence through testing"


That's worrisome. To quote the great programmer, testing can only show
the presence of bugs, never the absence. (Testing is necessary, it
isn't sufficient.)
--
Kevin Willoughby lid

We'd spend the remaining time trying to fix the engine.
-- Neil Armstrong
 




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