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Apollo: One gas environment?



 
 
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  #21  
Old May 3rd 04, 05:10 PM
Neil Gerace
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"Malcolm Bacchus" wrote in message
.uk...

For a lot of us, particularly in countries that weren't conquered by
Napoleon, gallons, feet and psi make a lot more intuitive sense than
litres, metres (not meters, please - you read those) and pascals. And
given that those were the units used for a lot of the matters being
discussed here, it makes even more sense to keep them that way. Go down
the road of conversion and somebody soon will be asking what the cost of
Apollo was in Euros!


Currency is different altogether. It's truly amazing here how quick the
changeover to decimal currency was, and yet how slow the metrication process
has been. Yet the benefits are exactly the same.


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  #22  
Old May 3rd 04, 05:13 PM
Neil Gerace
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"Herb Schaltegger" wrote in message
...

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


Here we see that a country that refuses to use certain units amazingly has
its very own spelling thereof. How weird is that?


  #23  
Old May 3rd 04, 05:15 PM
Neil Gerace
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"Jay Windley" wrote in message
...

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.


Most normal situations. What about the relationship between the gallon and
the pound? And by the way, which gallon and which pound?


  #24  
Old May 3rd 04, 05:25 PM
Henry Spencer
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In article ,
Herb Schaltegger wrote:
Uh, what relationship between liter and kilogram? You are thinking of
earlier versions of the metric system; SI defines no such relationship.


I think that was Jay's point, Henry . . .


Hardly. He's criticizing SI because this particular relationship doesn't
work in practice, but SI has never claimed it did -- the claimed merits of
SI simply have nothing to do with this strawman argument.

Yes, earlier metric systems did claim such a relationship... but then, his
argument began with the assertion that the English Engineering system of
units -- whichever one that is -- was complete and consistent and should
be considered by itself, independent of the confusion introduced by all
the *other* English systems of units used in engineering. The least he
can do is extend the same courtesy to the metric system.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |
  #25  
Old May 3rd 04, 05:35 PM
Nicholas Fitzpatrick
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In article ,
Brett Buck wrote:
On 5/1/04 6:42 AM, in article , "Nicholas
Fitzpatrick" wrote:
I'm sure I'm not the only one who had to look this up, not knowing
what a psi is equivalent to. I'm sure everyone knows that 1 atmosphere
= 101.3 kPA ... but many of us forget that this equals 14.7 psi


We do? Gee, *I* got through 4th grade science!


Well, I certainly do ... and I thought that others might not be familiar
enough with Imperial units to do it without looking it up, so I thought
I would simply pass on what I had just looked up, to help anyone else.
Only trying to help. Don't see why this has to be a flame-war ...
outside of the USA, there are few people who would have much
familiarity with those units ... and I thought NASA now had deemed
that all their subcontractors had to use metric units now, after
that Mars accident.

Personally, I got through engineering without having to do much in psi ..
certainly saw enough kPa ... and the Imperial stuff I saw was all in
atmospheres. (though I certainly learned where to find the conversion
necessary when I need it ... I just never use it enough to have any
feel for it intuitively ... but then I can never master Farenheight
either, and I see that frequently enough ... always have to convert
it to something I can get my head around.

When I watch the weather, they always give you pressures
in kPa around here ... and my recollection being in the States that
that they don't use psi during a weather forecast either ...

Nick
  #26  
Old May 3rd 04, 05:49 PM
Nicholas Fitzpatrick
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In article ,
Jay Windley wrote:

"Heinrich Zinndorf-Linker ([email protected])" 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.


Hang on ... as an engineer, I have seen design errors made because someone
was sizing a pumping system in gallons per minute. And they used
Imperial gallons (4.55 litres) in the design, but they used
US Gallons (3.78 litres) when they installed the pumps. I've also seen
mindless conversion errors made, doing the simplest conversions
(feet to metres), causing elevation problems. And then there is the
problems I have seen with base-mapping, not knowing if the co-ordinate
system is set up in US Feet (0.3048 per metre) or US Survey feet
(0.304800609601 per metre), which the USGS seems to use differently
in diffent jurisdictions. And this might not seem much, but when
your State Plane co-ordinates are in the tens of millions (which they
often are), then you just created a 15-foot error in the location of
something, where your tolerance is less than a foot.

To keep things straight, we basically outlaw Imperial units on any
site, except those in the USA, where we outlaw metric units and only
use US units (though the US Feet versus US Survey feet remains an issue).
However, of late we've been seeing an interesting hybrid. Base-mapping
showing up in metric, however all the vertical elevations are still in
Imperial (boy, does that screw up a volume-calculation). I had a long
lecture from an engineer in one field office, when I queried his units
(which he hadn't labelled), to be told, that of course they were metric,
"Do you think we are hill-billies down here"? A week later, I learned
that although the horizontal was metric, the vertical was all measured
in Imperial ... which I guess I was supposed to assume ... oh well ...

Nick
  #28  
Old May 3rd 04, 06:17 PM
Neil Gerace
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"Herb Schaltegger" wrote in message
...

In the context of the gas systems for Project Apollo, that question is
silly.


So is your non-issue about the litre and the kilogramme. Neither is defined
in terms of the other, therefore there is no 'relationship'.


  #29  
Old May 3rd 04, 06:22 PM
Jay Windley
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"Henry Spencer" wrote in message
...
|
| Uh, what relationship between liter and kilogram? You are thinking of
| earlier versions of the metric system; SI defines no such relationship.

Not now, of course, because no such relationship exists. But earlier a
relationship was presumed to exist, and belief in that relationship is still
perpetuated among lay users of the system, even though it's wrong and
misleading. Whether you measure volume by the liter or the hogshead is
irrelevant as long as all the units are well defined.

I'm reminded of a (probably apocryphal) story about MIT engineering students
who were asked to design and construct a bridge using the unit of "smoot",
Professor Smoot being their instructor. His linear, volumetric, and mass
properties were the measurement units for the project. Steel had a density
of so many smoots-mass per smoots-volume, for example. In doing that, you
would gain a deeper appreciation for where these "accepted" values for
everything actually come from, and greater insight into the arbitrary nature
of practically any measurement system.

An American baker is happy baking cookies in Fahrenheit. A French baker is
happy baking cookies in Celsius. Does it really matter? My argument is
that it does not, and that any measurement system that claims to be based on
"natural" relationships is probably not.

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

 




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