Debunking Contrail Theory - Part 2
Analysis of turbofan jet engines, the water vapor concentration at 35,000 feet, comparing to conditions conducive to cirrus cloud formation, and some math.
Recapping part one, we delved into the prevailing theory explaining the conspicuous and persistent plumes trailing certain aircraft as condensation. The theory suggests that humidity levels play a crucial role in determining the size and longevity of these trails. "Toggle" footage raised concerns about the humidity factor, casting skepticism on the entire theory, prompting further investigation. We also explored the broader science of condensation and initiated an examination of the atmospheric conditions at the cruising altitudes of the relevant planes.
The central question revolves around whether or not the checkerboard skies we see result from jetstream condensation. Since my last contribution, I've established 35,000 feet as the standard cruising altitude for my research. If evidence emerges to challenge this and proves that these jets are operating above the tropopause, it would imply stratospheric aerosol injection (SAI). However, current research leads me to believe that these aircraft operate within upper troposphere altitudes (30,000 to 40,000 feet).
What is a turbofan jet engine, and how does it work?
While part one touched on the average cruise height of an aircraft equipped with a turbofan jet engine, it overlooked a detailed examination of the engines themselves.
A turbofan jet engine constitutes an air-breathing propulsion system extensively utilized in both commercial and military aircraft. The term "turbofan" denotes the integration of two primary components: the core engine, a conventional gas turbine, and a fan positioned at the engine's front. A distinctive aspect of a turbofan engine lies in its bifurcation of airflow into two streams. One stream traverses through the core engine (hot stream), while the other bypasses the core engine, flowing around it (cold stream).
Cirrus cloud formation
As is often the case, nature provides a compelling example. Cirrus clouds, being a type of high-altitude cloud, offer valuable insights into the typical formation of ice crystals at such elevations.
Found at altitudes generally above 20,000 feet, cirrus clouds emerge in very cold air. The process initiates with the presence of moisture in the atmosphere. As air ascends due to phenomena like frontal or orographic lifting, it cools. Upon reaching saturation, water vapor condenses into minute ice crystals, often forming around ice nuclei such as dust particles. With the continuous addition of water vapor, these ice crystals grow, giving rise to cirrus clouds and their characteristic thin, wispy appearance.
The crucial aspect here lies in the fact that the saturation of water vapor is facilitated by rising air. Water vapor isn't abruptly introduced; rather, it emanates from a source from far beneath its formation.
Can a Turbofan Engine Spontaneously Generate Massive Clouds at 35,000 feet?
Due to varying weather conditions and locations, humidity levels at 35,000 feet can fluctuate. As a general principle, higher altitudes exhibit significantly lower humidity than ground level. At cruising altitudes of 35,000 feet, there is roughly 2-4g of water vapor per kg of dry air. I calculated specific humidity from temperature and relative humidity available from this source. As we have discovered previously, colder air has a far lower moisture-holding capacity than warm air. For comparison, specific humidity in exhaled air is around 10 to 20 grams of water vapor per kilogram of dry air.
While water vapor does exist at these altitudes, it is unlikely that the tiny amount of water vapor available can explain the size of the plumes we see. The more I delve into this subject, the more convinced I am that condensation does occur, yet my suspicion grows that a partial truth is being used to promote a grand falsehood. Despite the remarkable technology of turbofan jet engines, they cannot create tangible matter from thin air.
A mere 20% of the air passing through the turbofan enters its hot stream, which is responsible for the change in dew point, which is when gaseous water vapor heats up to extreme temperatures, and forms into ice crystals upon contact with the sub zero temperatures behind the jet. How much condensation is actually possible, and is this enough to explain the giant clouds left in the wake of some aircraft?
There are approximations in my math, but the mass flow rate “m” of dry air through a turbofan jet engine can be calculated by:
m = p x A x V
where:
m is the mass flow rate,
p is the air density,
A is the cross-sectional area through which the air is flowing (surface area of the fan),
V is the velocity of the air.
Given the values:
p = 0.521 kg/m3 (density of air at 35,000 feet)
A = 3.15 m2 (surface area of a turbofan on a Boeing 737)
V = 277.16 m/s (upper-average speed of a Boeing 737)
Substitute these values into the formula:
m = 0.521kg/m3 × 3.15m2 × 277.16m/s
m ≈ 430.99kg/s
Therefore, roughly 431kg of dry air pass through each turbofan per second. Between the two of them we come to 862kg of dry air. 20% of this passes through the hot stream, so roughly 172.4kg of air passes through the core engine of the turbofans. +
At these altitudes, if relative humidity levels were 100%, specific humidity would be roughly 4g of water vapor per kg of dry air. This extremely generous estimate lands us at 690g of water vapor pér second. 1g of water is equal to 1ml in volume. This is nearly 3 full cups of water.
Even if we were to assume that 100% of water vapor which passes through the turbo fan were to condensate (both cold stream and hot stream) then we would calculate less than 3.5L per second. With our most generous calculation, we get less than a US gallon.
Closing statement
Contrail theory is, as far as my research has shown, an invalid explanation for the huge plumes of gaseous matter left behind by some planes in flight. Though I will gladly welcome challenges on this matter, I am under the impression that I have debunked the contrail theory, and there is room in this space for new theses to explore what these phenomena may be.