Vapour trails

"Capt.Doug" wrote

Jet fuel averages 6.7 pounds per gallon with more BTUs, so the
stoichiometric ratio is slightly different.

More air, to take advantage of the BTU's, right? Plus jets are more
efficient at altitude, so more air again, right?.

Much of the air ingested by a
jet engine is used for cooling, not for burning. Do we include this air as
being ingested?

For what we were talking about, which is how much air is being used to make
con trails, (my take on it) it would seem to me we are talking about the air
that is being used to burn fuel.

Do we include the fan's cold stream as being ingested?

I wouldn't. It's just a big fancy prop, and props are not making any con
trails.

Another thing that is being overlooked, is the HP rating of the engine. In
talking about the air being injested, we have to remember that piston
engines are at most making a couple thousand HP (most lots less than that)
and the turbine engines on large jetliners are making multiples more power,
burning more fuel, using more air, and making more water vapor, and making
bigger contrails.

I'm no expert on this stuff, but I think my thinking (and guestimates) are
about right. After all, the original question was not a highly defined,
quanitative question, and neither is the answer. g
--
Jim in NC

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.

Larry Dighera wrote:

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

Clouds reflect radiation wich results in cooler days and warmer nights.
The question is, what is the total effect (i.e. integrated over 24
hours). The article you cited says, the total effect will be a warmer
climate.

This said, and not having read the original paper, the weak point of
that paper is that it is the result of a singular event and as such, the
results cannot be reproduced. (Actually, they could...)

In general, the impact of clouds to the climate is mathematically very
difficult to model and is one of the last unresolved factors in climatology.

Stefan

In article , Newps wrote:

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.

Where I come from, 18e9 is 18 billion. I'm amused in sort of an odd way
that everyone keeps saying things like "assuming people can affect the
climate of the earth is the height of arrogance." This usually comes just
before or after they say there isn't enough evidence to decide one way
or the other. Pick a position and stick with it--using both arguments
is a hint that you've made up your mind and you're just spraying a
blinding cloud of rhetoric. My position is that the evidence probably
isn't conclusive, but the consequences are pretty severe, so we'd better
be damned sure we aren't boning ourselves. Perhaps everyone that's
convinced there's nothing to global warming should move to Florida
as a show of faith?

By the way, sorry for the double-quoting. If I weren't such a bad man
I'd have posted once on Newps's and once on Larry's comments....

Mike Beede

On Sun, 12 Dec 2004 17:32:20 +0100, Stefan
wrote in ::

Larry Dighera wrote:

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

Clouds reflect radiation wich results in cooler days and warmer nights.
The question is, what is the total effect (i.e. integrated over 24
hours). The article you cited says, the total effect will be a warmer
climate.

That's reasonable. The point is, airline traffic is of such great
magnitude that it is conceivable that it affects earth's environment.

"Newps" wrote:
To think that man could change the temp of the earth one way or the
other is the height of arrogance.

You've pulled statements to this effect out of your nether regions and
posted them before, but you've never cited any backup for them. What
are your qualifications as a climatologist?

Larry Dighera wrote:




[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.

A bad smell doesn't equate to pollution.