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Apollo: One gas environment?



 
 
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  #12  
Old May 2nd 04, 09:51 PM
Heinrich Zinndorf-Linker (zili@home)
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Am Sun, 02 May 2004 11:42:43 -0500 schrieb "Herb Schaltegger":

For a normal person it is almost impossible to understand all these
interesting topics when it is full of gallons, feets and psi's instead of
litres, meters and Pascals


"Normal person", huh? You mean, some sort of "units snob?"

Well, since a good part of these "interesting topics" all use Imperial
measurements (the American part, of course), wouldn't it behoove you to
learn a few simple conversions so you can understand the discussion?
After all, a good many of us did so and can work fairly easily in either
system.


No, the problem with MANY (if not most) non-metric units is, that
there are often several localized versions of them - If you say (for
example) mile, pound or gallon, you can _never_ be absolutely, 100%
sure, which particular type of mile, pound or gallon is actually meant
- especially for people that are grown up in regions, where the
reflective use of these units has not been teached. Strict use of
metric (SI) units avoids ESPECIALLY THAT problem.

And there is the second problem of many redundant units - there is
absolutely no real need for a hundred or more different units for
mass, force, temperature, length (area/volume) and so on, for each of
are needed conversion factors that are _not_ simply powers of ten. In
SI there are only a very small couple of them.



cu, ZiLi aka HKZL (Heinrich Zinndorf-Linker)
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  #13  
Old May 2nd 04, 10:21 PM
Christopher M. Jones
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"Hans" wrote in message ...
I agree.

For a normal person it is almost impossible to understand all these
interesting topics when it is full of gallons, feets and psi's instead of
litres, meters and Pascals


That's a rather provincial notion don't you think?
That only "normal" people use SI units and you have to
be abnormal to use feet or gallons. Where's the love
of diversity? Where's the basic level of respect for
other cultures and other methods of doing things?
  #14  
Old May 2nd 04, 10:23 PM
Herb Schaltegger
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In article ,
"Heinrich Zinndorf-Linker (zili@home)" wrote:

No, the problem with MANY (if not most) non-metric units is, that
there are often several localized versions of them - If you say (for
example) mile, pound or gallon, you can _never_ be absolutely, 100%
sure, which particular type of mile, pound or gallon is actually meant
- especially for people that are grown up in regions, where the
reflective use of these units has not been teached. Strict use of
metric (SI) units avoids ESPECIALLY THAT problem.


No, yourself. In the context of sci.space.history and the history of
Project Apollo, the units questioned by the earlier poster "gallons,
feets and psi's" are all easily understood - as is the poster's
snobbishness and disdain for learning anything other than the system he
is most comfortable with. There are no "localized versions" at issue
with any of them vis a vis Apollo. The only definitions for these units
anyone need concern him- or herself with in this discussion are the
American ones.

For any other SI-snobs out there too lazy to look things up yourselves,
here are some basic conversions to keep you happy:

1 U.S. gallon = 3.79 liters
1 foot = 12 inches = 0.305 meters
1 inch = 2.54 centimeters
1 psi (pound per square inch) = 6.89 kilopascals
1 lbf (pound force) = 4.45 newtons

And there is the second problem of many redundant units - there is
absolutely no real need for a hundred or more different units for
mass, force, temperature, length (area/volume) and so on, for each of
are needed conversion factors that are _not_ simply powers of ten. In
SI there are only a very small couple of them.


Hate to break it to you, but when you start getting down to the nitty
gritty of the physics, the fundamental constants of nature don't give a
rat's ass about powers of ten. Doing the math itself in most
engineering applications is a hell of a lot harder than looking up a
silly conversion factor to change units at the end.

--
Herb Schaltegger, B.S., J.D.
Reformed Aerospace Engineer
Columbia Loss FAQ:
http://www.io.com/~o_m/columbia_loss_faq_x.html
  #15  
Old May 3rd 04, 01:11 AM
Jay Windley
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"Heinrich Zinndorf-Linker (zili@home)" wrote in message
...
|
| No, the problem with MANY (if not most) non-metric units is, that
| there are often several localized versions of them

Not when engineers use them. The English Engineering system is as rigidly
defined as the Systeme Internationale.

I'm not trying to trash SI, but the touted advantages are largely irrelevant
in use. For example, the relationship between liter and kilogram seems
wonderfully logical until you forget to take into account just under what
precise (and largely arbitrary) conditions a kilogram and a liter of water
can be considered equivalent.

Silliness is not in the use of arbitrary units; it's in the use of units
that are claimed to be consistent but are deceptively arbitrary anyway. If
a liter of water is *really* 0.994 kilogram under the conditions of
interest, then what good is it telling a student the SI system is
consistent? Foolishness is conveying the *illusion* of consistency and then
failing to deliver it.

--
|
The universe is not required to conform | Jay Windley
to the expectations of the ignorant. | webmaster @ clavius.org

  #16  
Old May 3rd 04, 02:25 PM
Henry Spencer
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In article ,
Jay Windley wrote:
I'm not trying to trash SI, but the touted advantages are largely irrelevant
in use. For example, the relationship between liter and kilogram...


Uh, what relationship between liter and kilogram? You are thinking of
earlier versions of the metric system; SI defines no such relationship.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |
  #18  
Old May 3rd 04, 04:54 PM
Brett Buck
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On 5/2/04 7:43 AM, in article , "Hans"
wrote:

I agree.

For a normal person it is almost impossible to understand all these
interesting topics when it is full of gallons, feets and psi's instead of
litres, meters and Pascals



Another sad comment on the current capabilities of the "normal person".
Or, you personally.
Brett




  #20  
Old May 3rd 04, 05:08 PM
Neil Gerace
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"Herb Schaltegger" wrote in message
...

Well, since a good part of these "interesting topics" all use Imperial
measurements (the American part, of course), wouldn't it behoove you to
learn a few simple conversions so you can understand the discussion?
After all, a good many of us did so and can work fairly easily in either
system.


The only difficult thing for me would be the difference between gauge
pressure and absolute pressure, but I learned that difference in high school
so it's nothing now.


 




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