Vapour trails

Air is mostly (70%) Nitrogen, most of the rest is Oxygen.

The atomic mass of Nitrogen is 14, of Oxygen is 16. Both occur as
molecules (N2, O2) so the mass of each molecule is twice the above
figures.

Now, at STP, there are 22.4 liters in a mole, and a mole is the amount
of stuff that would weigh (in grams) what its molecular mass is. So,
22.4 liters of nitrogen would weigh 28 grams. Of Oxygen, it would be
32 grams. So we have a little over a gram per liter. Ok, more than
just a little, but less than a gram and a half per, and it's in the
ballpark. Lets use one gram per liter.

A liter is 1000 cubic centimeters, which is the volume of a cube 10
centimeters on a side. (or equivealently, 1/10 meter on a side).
1000 liters would be a cube one meter on a side, and air would weigh
"a little" over one Kg per cubic meter. A meter is "a little" over
three feet, so a cubic meter is "a little more" over 27 cubic feet.
One Kg is "a little" over two pounds, divide by 27, or even 30, and I
get something less than a tenth of a pound per cubic foot.

Air is pretty heavy, which is why we can fly. It weighs .078
lb/cubic foot at standard sea level pressure and temperature. What's
that, about 13 cubic feet for a pound?

Yep. That's just about right.

Now, take a typical room that's three meters tall, three meters wide,
and four meters deep. Not a very big room, but it has a high ceiling.
This gives us 36 cubic meters, and the air would weigh "a little"
over 36 Kg. Well, I weigh more than a little over 36 Kg, but it's
close enough to show that a smallish room will hold less than a
person's mass in air, but a largish roomfull of air can easily
outweigh a person.

The air in a room can easily
outweigh the occupants.

Yep again.

Now, how big is the White House?

Jose
--
Freedom. It seemed like a good idea at the time.
for Email, make the obvious change in the address.

Orval Fairbairn wrote:
In article .com,
wrote:

Air is pretty heavy, which is why we can fly. It weighs .078
lb/cubic foot at standard sea level pressure and temperature.
What's
that, about 13 cubic feet for a pound? The air in a room can easily
outweigh the occupants.

Dan

I seem to recall .002378 #m/ft3 as air density at STP.

http://www.engineeringtoolbox.com/24_600.html lists it at 60
degrees F. as 7.636 x 10-2 lbs/cu.ft., or .07636 lbs, a bit less than I
had quoted. STP is at 59 degrees, but the one degree difference doesn't
change the density much.

Dan

On Thu, 16 Dec 2004 at 03:36:14 in message
, Orval
Fairbairn wrote:

I seem to recall .002378 #m/ft3 as air density at STP.

That is in slugs per cubic foot. Both figures are correct. One in pounds
mass and the other in slugs which is a mass unit. Is the slug still
used? I used it a lot in my early days.

My old standard atmosphere data gives sea level at 0.07675 lb/cubic
foot.

Divide that by g (32.17 ft per second per second) gives 0.0023857 slugs
per cubic foot.
--
David CL Francis

On Sat, 11 Dec 2004 20:42:05 +0000, Michael Calwell
wrote in
::

I work outdoors beneath the flightpath to Edinburgh Airport.

I take it that vapour trails are the condensed water contained in the
air ingested by the engines. My question is, how much air does an engine
ingest at cruise? How would you visualise that amount of air?

If I recall correctly, as a result of the ban on flight over the US
following the 9/11 terrorist attack, there was a measurable
temperature rise attributed to the reduction in airliner contrails.

Yahoo yielded this:
http://p211.ezboard.com/fchemtrailss...picID=75.topic

"Larry Dighera" wrote

If I recall correctly, as a result of the ban on flight over the US
following the 9/11 terrorist attack, there was a measurable
temperature rise attributed to the reduction in airliner contrails.

Yahoo yielded this:

http://p211.ezboard.com/fchemtrailss...picID=75.topic

I was unable to find where the link talked about that in a reasonable amount
of time, but I gotta say.....

Yeah, right!!! :-)
--
Jim in NC

On Sat, 11 Dec 2004 19:01:04 -0500, "Morgans"
wrote in ::

I was unable to find where the link talked about that...


Absence of contrails increases diurnal temperature range

Clouds formed by the water vapor in the exhaust from jet planes have a
small but significant effect on daily temperatures, a new study
confirms. The grounding of commercial flights for three days after
last September's terrorist attacks in the United States gave David
Travis at the University of Wisconsin-Whitewater and colleagues a
chance they never thought they'd have: to study the true impact that
contrails from jet engines have on our climate1

Despite a wealth of experiments, it had been virtually impossible to
gauge the effect of contrails because air traffic, particularly over
regions such as Europe and North America, never stopped. Until 11
September 2001, that is. Contrails left high in the atmosphere spread
out into cirrus-like clouds under the right atmospheric conditions.
Natural cirrus clouds - thin layers of wispy water vapor that often
resemble fish scales - trap heat being reflected from the ground and,
to a lesser extent, reflect some of the Sun's rays.

Travis's team compared the average daily high and low temperatures
over North America from 11 to 14 September 2001, with climatic records
from 1977 to 2000, matching the weather over those three days with
similar weather in September from historical records.
They found that the difference between daily high and nightly low
temperatures in the absence of contrails was more than 1 oC greater
than in the presence of contrails. Comparing the three-day grounding
period with the three days immediately before and after, the impact
was even larger - about 1.8 oC.

The researchers suggest that in regions with crowded skies, contrails
work just like artificial cirrus clouds, preventing days from getting
too hot by reflecting the Sun's rays, and keeping nights warmer by
trapping the Earth's heat. Averaged over the globe, which is largely
free of air traffic, the effect is negligible. "But locally, contrails
are equally as significant as greenhouse gases," says Carleton.

The discovery is important, "especially when you consider that air
traffic is expected to increase at about five per cent a year". But
making use of the information by incorporating it into climate models,
for example, will be difficult. Little is known about what conditions
lead to contrail formation, how long they last, and whether they
affect more than just temperature.

References

1Travis, D. J., Carleton, A. M & Lauritsen, R. G. Contrails reduce
daily temperature range. Nature, 418, 601, (2002).

Larry Dighera wrote:

If I recall correctly, as a result of the ban on flight over the US
following the 9/11 terrorist attack, there was a measurable
temperature rise attributed to the reduction in airliner contrails.

The source you menion says quite the opposite:

"Locally, contrails are equally as significant as greenhouse gases."

(Copied from your later post.)

Stefan

On Sun, 12 Dec 2004 13:07:18 +0100, Stefan
wrote in ::

Larry Dighera wrote:

If I recall correctly, as a result of the ban on flight over the US
following the 9/11 terrorist attack, there was a measurable
temperature rise attributed to the reduction in airliner contrails.

The source you menion says quite the opposite:

"Locally, contrails are equally as significant as greenhouse gases."


Would that "opposite" be during the day or night? It also says: "...
nights warmer by trapping the Earth's heat."

So while my 3 year old memory may have been incomplete, it was about
as accurate as your interpretation of the article I posted yesterday.

What seems infinitely more significant is the awesome magnitude of
exhaust spewing from airliners as a result of burning 18,536,000,000
(that's 18-1/2 trillion) gallons of kerosene annually*; one would
expect some environmental impact.

* http://www.aopa.org/whatsnew/factcard.pdf

Larry Dighera wrote:



What seems infinitely more significant is the awesome magnitude of
exhaust spewing from airliners as a result of burning 18,536,000,000
(that's 18-1/2 trillion) gallons of kerosene annually*; one would
expect some environmental impact.


Baloney. If we had as a goal to raise or lower the temp of the earth by
a few degrees we couldn't do it. 30 years ago the sceintific community
was scared to death about global cooling. That didn't get anybody
revved up so they switched to global warming. Cover story in a 1975
issue of Time magazine, quoting all the great sceintists of the day,
said by the year 2000 there would be widespread famine due to the
reduced growing season because it was getting too cold. Now a mere 30
years later we're worrying about global warming. The globe is certainly
warming or cooling, it always has. But you cannot prove anything with
the 100 or so years of data that we have much less the last 30 years.
There used to be glaciers covering the northern 5th of the US, they came
and went dozens of times in the history of the earth. Did the caveman
worry about global warming as he watched the glaciers recede? Did the
caveman have anything to do with it? To think that man could change the
temp of the earth one way or the other is the height of arrogance.

On Sun, 12 Dec 2004 09:04:18 -0700, Newps wrote
in ::

Larry Dighera wrote:


What seems infinitely more significant is the awesome magnitude of
exhaust spewing from airliners as a result of burning 18,536,000,000
(that's 18-1/2 trillion) gallons of kerosene annually*; one would
expect some environmental impact.


Baloney.

[Temperature related diatribe snipped]

Stand down wind of an airliner and inhale, then tell me there's no
significant air pollution emanating from turbine engines. When I
worked at LAX I was nearly overcome with the fumes from these fire
breathers as they taxied by.