X-Mozilla-Keys:                                                                                 
Vance Jaqua wrote:

SI is not that easy - I have done
consulting for rocket people all over the world. and
the metric system is just as goofed up as inches and
feet - A "bar" is not an atmosphere - it is 14.504
psia
probably measured on a cliff top in Sweden? a std
atmosphere is 14.696 psia - 100,000 pascals ( not a
million) is very close to a bar at 14.506 psia, and a
Kg/cm^2 -is 14.223 also close but no cigar - just far
enough off to burn up in the atmosphere of Mars
instead of orbit. 

Metric threads are different nation
to nation and none are as standardized as SAE classes
- when we helped the Japanese where metric is now law
of the land, they called out SAE threads with metric
numbers, ie 6.35 by 0.907 mm (1/4 28) part no. XXXXX
from Elastic Stop Nut of America. 

When we worked on
the upper stage of the "Peacekeeper" we were ordered
to use the SI system but the government soon found
that both cost and quality were going to be adversly
impacted and they had a change of heart. However we
were directed by NASA in all reports to use the SI
units, but we could also include English units in
parenthese. 

I even wrote a BASIC program that would
search an ASCI copy of a report and convert and retype
in that format. I have heard, and believe, that not
long ago the metric system was "corrected" such that a
meter was exactly 39.37 inches. The inch was better
anchored to a precision standard, and I think now they
are both anchored to x number of wavelengths of sodium
light. 

For anyone the best units are the ones you can
visualize, and I don't think anyone in the world
thinks in the bastardized version of metric called SI
Vance

 
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