Re: IS: Follow the Current - WAS: Apollo One, the FBI, and Scott Grissom

From: LaDonna Wyss (hpywife927_at_yahoo.com)
Date: 06/09/04 

Date: 8 Jun 2004 17:18:50 -0700

derekl1963@nospamyahoo.com (Derek Lyons) wrote in message news:<40d0b378.34449111@supernews.seanet.com>...
> hpywife927@yahoo.com (LaDonna Wyss) wrote:
> >2. No upstream impedence. The switch was the source of the short;
> >everything downstream was affected by the resultant voltage
> >transients.
>
> The problem is... While the behavior of other equipment on the bus
> (the term downstream is incorrect) is consistent with voltage
> transients , a hard short produces a standing change in voltage and
> current flow, not transients. (If it's not a standing change, its by
> definition not a hard short.) This standing change can be masked
> however by the effects of switching other equipment on and off the
> bus.
>
> Parenthetically I find it hard to credit that a hard short in a
> thruster switch would not cause the master breakers on the bus to
> perform their intended functions and drop the bus entirely. (I don't
> recall however if their were master breakers.)
>
> Transients are indicative of 'arcing and sparking', which is
> consistent with the known problems in the cabling inside the CM.
> Transients are also a common condition when you have a variable short
> or multiple variable shorts to ground (without arcing), again this is
> consistent with the known problems with the cabling. Combine these
> with the transient effects of switching on and off other equipment on
> the bus and you can increase the effects of these cabling problems by
> altering the current and voltage flow.
>
> D.

That's exactly my point. Yes, this was a "hard short", but you have
to take into consideration its existence long before the test started
that afternoon. When the test did start, everytime the crew powered
up a system on the same bus that system exhibited problems. The Block
I spacecraft was not nearly as protected as it should have been, nor
as protected as systems are today.
So what you are describing here is exactly what I have been talking
about.
LaDonna

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