"Derek Lyons" wrote in message
...
"Jim Oberg" wrote:
JimO adds: No alarm bells --

Right. And the tile damage caused by foam didn't break anything major
did they? And the problem with O-ring blow-by turned out to be a non
issue too, didn't it?

*Anytime* a primary system is OOC, especially when it's a chronic
condition (as it seems to be with Elektron), alarm bells should be
ringing so loud as to crack the windows.

Apples and oranges. There was no backup for the TPS damage on Columbia and
there was no backup (still isn't) to prevent o-ring blow by on the SRB's
from turning into a disaster. Those are crit-1 failures. Hopefully we'll
finish developing the TPS repair techniques that NASA abandoned after they
became comfortable with the TPS performance early on in the program, so at
least that won't be crit-1 anymore.

However, ISS has no less than four sources of O2:

1. Elektron - Preferred the most because it turns otherwise useless H2O
into O2

2. Progress O2 tanks - Preferred second (likely because of upmass
efficiency and safety)

3. Solid O2 generators - Not as preferred (likely due to higher upmass and
safety issues)

4. US airlock O2 tanks - Not currently preferred due to the current shuttle
grounding.

There are plenty of consumable oxygen supplies, enough to get the next
Progress....

And what shall we leave off of Progress to accomodate the extra O2?
Or shall we simply expend margin and hope for better luck?

The Russians are very good at this balancing act. They've been doing it
ever since the first Progress launch in the 1970's. It would certainly be
helpful if the shuttle was flying, but with only two people on ISS, this
situation really isn't much different than what the Russians did with Salyut
and Mir.

If you expected ISS to improve on what was done with Mir, what was the basis
for that belief? The US went into this knowing full well that US life
support wouldn't be online for many years into the program.

That along with lack of a US CRV and many other things makes the ISS very
dependant on the Russians. Really, this is more of a US failure in the way
the program was structured rather than a Russian failure. The Russians know
the limitations of Elektron very well.

Jeff
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