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Re:Re: Re: The hard questions..



Kevin said...

> >If we had been clairvoyant we would have probably charged the aux. battery
> >and taken the main battery off line.
>
>you had earlier mentioned that the command team had noticed battery anomalies
>several months ago...

Correct, and that had stayed "stable" for quite a while.  I was speaking of 
the rapidly deteriorating final scenario.

> > Charging the aux. battery would have accomplished nothing unless the
> > shorted main battery were also taken off-line.
>
>If the aux battery would have been completely charged might it not have 
>dumped
>enough energy into the main to possibly burn open the dendrite shorting a
>cell?

...maybe, I doubt it though.  We'll never know for sure.

>  Or  having the aux battery  fully charged you may have been more prone to
>"cut loose" the main  as you were watching it fail since you would have known
>that you had a good fully charged aux...

The aux. battery would have come up to working voltage virtually instantly, 
so that really wasn't a factor.

>In hindsight at the time of failure,cutting both batteries open might have
>been yet another option, since you could then catch the sat in sunlight and
>look at what was going on with both batts before committing to one or the
>other... but there may be things I'm not aware of that would have  prevented
>this from working...

That command is not an option.  The hardware prevents taking both batteries 
off-line.

>personally I think the relay design is poor  and connecting a dead aux is not
>much better... diode isolation even though it costs you a voltage drop  would
>have been better, but I know then you couldn't try and save a set of
>batteries until later... every design has tradeoffs.

The diode option was extensively debated during construction.

>      I for one no know of no company, group, individual, or doctor...   that
>doesn't do a post-mortem after something goes wrong...   to learn from what
>has happened and to see if anything could have been done differently  in the
>future. But there is no reason for anyone to wrap themselves in self pity or
>to martyr themselves as being to blame, for that is non-productive... but to
>just say it was "inevitable" and lets move along to the next sat without
>reviewing all of the possibilities and options  is equally non-productive.

I am not attempting to be a martyr or engage in self-pity.  The 
"inevitable" in my comments does not refer specifically to this 
incident.  It refers to the fact that nothing lasts forever.  Every 
satellite and every person must eventually die and blame is not always a 
component of that event, although many of us have a strong tendency to try 
to make it so.  I don't personally believe that we have seen AO-40's 
ultimate death.  It was certainly not my point that we should "move on 
without reviewing."  Amsat groups all over the world are analyzing this 
incident and considering applications  to future satellites.  Questions 
have already been posed about P3-E's battery configuration, based on this 
incident.   However, there is a right way and a wrong way to construct a 
review process.  These are a weekly function in my business.  Blaming, 
finger-pointing, inflammatory rhetoric, etc. are not 
productive.  Productive reviews are at the process level.  Any review of 
AO-40 will always be heavily colored by the unknowns of the 400n incident 
which caused significant mechanical distortions, heat, pressure, etc.  We 
have no way to know the extent of these damages.  It seems quite likely 
that they played a part in the battery failure.



-- 
  _______________________________________________________________________
  Stacey E. Mills, W4SM    WWW:    http://www.keplerian.com
   Charlottesville, VA     PGP key: http://www.keplerian.com/key
  _______________________________________________________________________

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